Motor driving apparatus and motor driving method Number:7,088,067 from the United States Patent and Trademark Office (PTO) owispatent A motor driving apparatus has a driver circuit configuration capable of individually adjusting three phase coil currents. Coil current waveforms are formed to have a total of three phase shaft direction forces to be zero in compliance with predetermined mathematical expressions, and thus, three phase coil current profiles can be made independent of one another, and vibration-causing factors attributed to the fact that a certain phase is in an non-energized state are corrected by adjusting the current profiles of the other phases. Consequently, the vibration and the noise can be reduced.<H apparatus, driving, Motor, driving, a, 7088067.html, Patent, pto, 7088067

Title: Motor driving apparatus and motor driving method

Abstract: A motor driving apparatus has a driver circuit configuration capable of individually adjusting three phase coil currents. Coil current waveforms are formed to have a total of three phase shaft direction forces to be zero in compliance with predetermined mathematical expressions, and thus, three phase coil current profiles can be made independent of one another, and vibration-causing factors attributed to the fact that a certain phase is in an non-energized state are corrected by adjusting the current profiles of the other phases. Consequently, the vibration and the noise can be reduced.

Patent Number: 7,088,067 Issued on 08/08/2006 to Yamamoto, et al.

Inventors: Yamamoto; Yasunori (Hirakata, JP), Mori; Hideaki (Nishinomiya, JP), Kuroshima; Shinichi (Ibaraki, JP), Nishino; Hideki (Takatsuki, JP), Iwanaga; Taishi (Nagaokakyo, JP)
Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka, JP)

Appl. No.: 11/191,853

Filed: July 27, 2005

Foreign Application Priority Data


Jul 28, 2004 [JP]			P2004-219663

Current U.S. Class: 318/432 ; 318/138; 318/254; 318/434; 318/439

Current International Class: H02P 7/00 (20060101)

Field of Search: 318/432,434,138,439,254,599,700,800

References Cited [Referenced By]

U.S. Patent Documents


6674258	January 2004	Sakai et al.
6710569	March 2004	Iwanaga et al.
6940239	September 2005	Iwanaga et al.
2003/0102832	June 2003	Iwanaga et al.

Foreign Patent Documents


2892164	Feb., 1999	JP
2003-174789	Jun., 2003	JP

Primary Examiner: Duda; Rina
Assistant Examiner: Smith; Tyrone
Attorney, Agent or Firm: RatnerPrestia

Claims

What is claimed is:

1. A motor driving apparatus for driving a multiphase motor by controlling energization to star-connected motor driving coils of multiple phases, the apparatus comprising: a rotor position detector section for obtaining rotor position information by detecting back electromotive voltages induced in a motor driving coil of a non-energized phase; a half bridge circuit group including a pair of high-potential-side driving transistors and low-potential-side driving transistors respectively connected to one side of terminals of the motor driving coils and the other side of the terminals which is a neutral point of the motor driving coils; a torque command signal generator section for generating torque command signals for motor driving in accordance with original torque command signals input from the outside and output signals of the rotor position detector section; a pulse modulation control signal generator section for generating pulse modulation control signals for driving each phase coil in accordance with the command signals generated by the torque command signal generator section; and an energization control section which is supplied with the pulse modulation control signals and controls the energization of the motor driving coils of the multiple phases at a predetermined cycle in accordance with the supplied pulse modulation control signals, wherein the energization control section sets an non-energized period during which only one motor driving coil of the motor driving coils of the multiple phases is set to an non-energized state and the energization control section performs the energization to the neutral point in the non-energized period, so that the motor driving is performed in a manner such that a total of coil currents of the multiple phases is not zero in the non-energized period.

2. The motor driving apparatus according to claim 1, wherein the energization control section sets the neutral point terminal to be in a non-energized state where the neutral point terminal is not energized in an all-coil energized period during which driving currents are flowed to all the motor driving coils.

3. The motor driving apparatus according to claim 1, further comprising a total current detecting section for detecting either a total current of all the high-potential-side driving transistors or a total current of all the low-potential-side driving transistors, and the energization of each of the motor driving coils is time-divisionally controlled.

4. The motor driving apparatus according to claim 1, further comprising: a shunt resistor for detecting either a total current of the high-potential-side driving transistors or a total current of the low-potential-side driving transistors; and an error amplifier section that amplifies a difference between a signal in accordance with an inter-terminal potential difference of the shunt resistor and a signal in accordance with the torque command value, wherein the torque command signal generator section generates the torque command signal of the individual phase in accordance with an output signal of the error amplifier section and the output signal of the rotor position detector section.

5. The motor driving apparatus according to claim 1, further comprising: a PWM ON pulse generator section that generates a pulse signal for selecting the high-potential-side and the low-potential-side driving transistors and for starting PWM energization; a shunt resistor for detecting either a total current of the high-potential-side driving transistors or a total current of the low-potential-side driving transistors; and a comparator that performs comparison between a signal of an inter-terminal potential difference across the shunt-resistor and the torque command signals for the individual phases including the neutral point together with a torque command signal equivalent to the sum of the torque command signals, the torque command signals being generated from the torque command signal generator section, wherein the pulse modulation control signal generator section generates PWM signals in accordance with output signals of the PWM ON pulse generator section and output signals of the comparator.

6. The motor driving apparatus according to claim 2, further comprising a total current detecting section for detecting either a total current of all the high-potential-side driving transistors or a total current of all the low-potential-side driving transistors, and the energization of each of the motor driving coils is time-divisionally controlled.

7. The motor driving apparatus according to claim 2, further comprising: a shunt resistor for detecting either a total current of the high-potential-side driving transistors or a total current of the low-potential-side driving transistors; and an error amplifier section that amplifies a difference between a signal in accordance with an inter-terminal potential difference of the shunt resistor and a signal in accordance with the torque command value, wherein the torque command signal generator section generates the torque command signal of the individual phase in accordance with an output signal of the error amplifier section and the output signal of the rotor position detector section.

8. The motor driving apparatus according to claim 2, further comprising: a PWM ON pulse generator section that generates a pulse signal for selecting the high-potential-side and the low-potential-side driving transistors and for starting PWM energization; a shunt resistor for detecting either a total current of the high-potential-side driving transistors or a total current of the low-potential-side driving transistors; and a comparator that performs comparison between a signal of an inter-terminal potential difference across the shunt-resistor and the torque command signals for the individual phases including the neutral point together with a torque command signal equivalent to the sum of the torque command signals, the torque command signals being generated from the torque command signal generator section, wherein the pulse modulation control signal generator section generates PWM signals in accordance with output signals of the PWM ON pulse generator section and output signals of the comparator.

9. A motor driving method for driving a multiphase motor by controlling energization of star-connected motor driving coils of multiple phases and by performing driving control of a pair of high-potential-side driving transistors and low-potential-side driving transistors respectively connected to one side of terminals of the motor driving coils and the other side of the terminals which is a neutral point of the motor driving coils, the method comprising the steps of: obtaining rotor position information by detecting back electromotive voltages induced in a motor driving coil of a non-energized phase; generating torque command signals for motor driving in accordance with original torque command signals input from the outside and the obtained rotor position information; generating pulse modulation control signals for driving each phase coil in accordance with the generated torque command signals; and controlling the energization of the motor driving coils of the multiple phases at a predetermined cycle in accordance with the pulse modulation control signals, wherein, in the energization controlling step, there is set an non-energized period during which only one motor driving coil of the motor driving coils of the multiple phases is set to an non-energized state and the energization control step performs the energization to the neutral point in the non-energized period, and wherein the energization control step does not perform the energization to the neutral point in an all-coil energized period during which driving currents are flowed to all the motor driving coils, so that the motor driving is performed in a manner such that a total of coil currents of the multiple phases is not zero in the non-energized period.

10. The motor driving method according to claim 9, further comprising a step of detecting either a total current of all the high-potential-side driving transistors or a total current of all the low-potential-side driving transistors, thereby time-divisionally performing the energization control so that energized currents to the terminals of the motor driving coils respectively becomes predetermined target current values.

11. The motor driving method according to claim 9, wherein the total of the coil currents becomes zero in the all-coil energized period during which driving currents are flowed to all the motor driving coils.

12. The motor driving method according to claim 9, wherein in the non-energized period during which only one motor driving coil is set to the non-energized state, waveforms of the coil currents of the respective phases are formed such that a total sum of products of multiplication of the coil currents of the respective phases and shaft direction force constant waveforms different by 90.degree. in phase from torque constant waveforms of the coil currents becomes substantially zero.

13. The motor driving method according to claim 9, wherein in the non-energized period during which only one motor driving coil is set to the non-energized state, the coil currents of the respective phases are controlled to have waveforms such that each of products of multiplication of the coil currents of the respective phases and respective sine functions different by 90.degree. in phase from current phases of the coil currents of the respective phases mutually form a shape substantially axially symmetric with respect to a symmetry axis of an intermediate time point of the non-energized period.

14. The motor driving method according to claim 9, which is a driving method for a sensorless three-phase motor, wherein waveforms of the coil currents of the respective phases are formed such that a function of a product of multiplication of a second-phase coil current delayed in phase by an electrical angle of 120.degree. from a first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a second-phase coil current has substantially a same magnitude and an opposite polarity with respect to a function of a product of multiplication of a third-phase coil current advanced in phase by an electrical angle of 120.degree. from the first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a third-phase coil current, in an non-energized period of the first phase coil current.

15. The motor driving method according to claim 9, which is a driving method for a sensorless three-phase motor, wherein waveforms of the coil currents of the respective phases are formed such that, a function of a product of multiplication of a second-phase coil current delayed in phase by an electrical angle of 120.degree. from a first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a second-phase coil current and a function of a product of multiplication of a third-phase coil current advanced in phase by an electrical angle of 120.degree. from the first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a third-phase coil current, form substantially a symmetric shape with respect to an intermediate time point of the non-energized period of the first phase coil current set as a symmetry axis thereof.

16. The motor driving method to claim 9, which a driving method for a multiphase motor having the number of phases being N, wherein, assuming that k represents an integer from 1 to N, a function of the coil current of the respective phases is represented by f(.theta.-(k-1)360/N), and a fundamental wave related to an overall cycle of f(.theta.) is represented by sin(.theta.), f(.theta.) is a function satisfying an equation all the time as following: .SIGMA.f(.theta.-(k-1)360/N)cos(.theta.-(k-1)360/N)=0 wherein .SIGMA. represents a sum of the products of the coil currents of the respective phases and a sine wave advanced by an electrical angle of 90.degree. from the fundamental wave thereof with respect to all the phases in the range from k=1 to k=N.

17. The motor driving method according to claim 13, wherein, in a period during which a motor coil of one phase is in an non-energized state, coil current waveforms of the other phases that are not in the non-energized state are formed such that, when a fundamental wave component of the corresponding current waveforms is represented by sin(.theta.), the current waveform of one phase, the fundamental wave component of which is represented by sin(.theta.), is proportional to sin(.theta.-30) in a period during which the other one phase is in the non-energized state during a transition from a zero current level to a peak of the sine wave and in a period during which the other one phase is in the non-energized state during a transition from a zero current level to a bottom of the sine wave, and the current waveform of the one phase, the fundamental wave component of which is represented by sin(.theta.), is proportional to sin(.theta.+30) in a period during which the other one phase is in the non-energized state during a transition from the peak of the sine wave to the zero current level and in a period during which the other one phase is in the non-energized during a transition from the bottom of the sine wave to the zero current level.

18. The motor driving method according to claim 9, wherein a coil current waveform in an energized period of a coil of a certain one phase interposed between a non-energized period of the coil of the certain one phase and a non-energized period of a coil of the other phases adjacent thereto is formed to be substantially a triangular shape wherein the current value becomes zero on the non-energized period side of the coil, whereby the coil currents of the respective phases are made to be continuous over all cycles.

19. The motor driving method according to claim 9, wherein motor driving is performed in a manner that a phase difference between the coil current waveform of the respective phases and the torque constant waveform of the respective phases is maintained to be substantially a constant angle.

20. The motor driving method according to claim 9, wherein one cycle of the continuous current waveforms of the respective phases having the non-energized periods includes an non-energized period, a subsequent slow-sloped current increase period, a subsequent sharp-sloped current increase period, a subsequent maximum current period, a subsequent sharp-sloped current decrease period, a subsequent slow-sloped current decrease period, a subsequent non-energized period, a subsequent slow-sloped current decrease period, a subsequent sharp-sloped current decrease period, a subsequent minimum current period, a subsequent sharp-sloped current increase period, a subsequent slow-sloped current increase period, and a subsequent non-energized period.

21. The motor driving method according to claim 10, wherein the total of the coil currents becomes zero in the all-coil energized period during which driving currents are flowed to all the motor driving coils.

22. The motor driving method according to claim 10, wherein in the non-energized period during which only one motor driving coil is set to the non-energized state, waveforms of the coil currents of the respective phases are formed such that a total sum of products of multiplication of the coil currents of the respective phases and shaft direction force constant waveforms different by 90.degree. in phase from torque constant waveforms of the coil currents becomes substantially zero.

23. The motor driving method according to claim 10, wherein in the non-energized period during which only one motor driving coil is set to the non-energized state, the coil currents of the respective phases are controlled to have waveforms such that each of products of multiplication of the coil currents of the respective phases and respective sine functions different by 90.degree. in phase from current phases of the coil currents of the respective phases mutually form a shape substantially axially symmetric with respect to a symmetry axis of an intermediate time point of the non-energized period.

24. The motor driving method according to claim 10, which is a driving method for a sensorless three-phase motor, wherein waveforms of the coil currents of the respective phases are formed such that a function of a product of multiplication of a second-phase coil current delayed in phase by an electrical angle of 120.degree. from a first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a second-phase coil current has substantially a same magnitude and an opposite polarity with respect to a function of a product of multiplication of a third-phase coil current advanced in phase by an electrical angle of 120.degree. from the first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a third-phase coil current, in an non-energized period of the first phase coil current.

25. The motor driving method according to claim 10, which is a driving method for a sensorless three-phase motor, wherein waveforms of the coil currents of the respective phases are formed such that, a function of a product of multipiication of a second-phase coil current delayed in phase by an electrical angle of 120.degree. from a first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a second-phase coil current and a function of a product of multiplication of a third-phase coil current advanced in phase by an electrical angle of 120.degree. from the first phase and a sine wave delayed in phase by an electrical angle of 90.degree. from a third-phase coil current, form substantially a symmetric shape with respect to an intermediate time point of the non-energized period of the first phase coil current set as a symmetry axis thereof.

26. The motor driving method to claim 10, which a driving method for a multiphase motor having the number of phases being N, wherein, assuming that k represents an integer from 1 to N, a function of the coil current of the respective phases is represented by f(.theta.-(k-1)360/N), and a fundamental wave related to an overall cycle of f(.theta.) is represented by sin(.theta.), f(.theta.) is a function satisfying an equation all the time as following: .SIGMA.f(.theta.-(k-1)360/N)cos(.theta.-(k-1)360/N)=0 wherein .SIGMA. represents a sum of the products of the coil currents of the respective phases and a sine wave advanced by an electrical angle of 90.degree. from the fundamental wave thereof with respect to all the phases in the range from k=1 to k=N.

27. The motor driving method according to claim 14, wherein, in a period during which a motor coil of one phase is in an non-energized state, coil current waveforms of the other phases that are not in the non-energized state are formed such that, when a fundamental wave component of the corresponding current waveforms is represented by sin(.theta.), the current waveform of one phase, the fundamental wave component of which is represented by sin(.theta.), is proportional to sin(.theta.-30) in a period during which the other one phase is in the non-energized state during a transition from a zero current level to a peak of the sine wave and in a period during which the other one phase is in the non-energized state during a transition from a zero current level to a bottom of the sine wave, and the current waveform of the one phase, the fundamental wave component of which is represented by sin(.theta.), is proportional to sin(.theta.+30) in a period during which the other one phase is in the non-energized state during a transition from the peak of the sine wave to the zero current level and in a period during which the other one phase is in the non-energized during a transition from the bottom of the sine wave to the zero current level.

28. The motor driving method according to claim 10, wherein a coil current waveform in an energized period of a coil of a certain one phase interposed between a non-energized period of the coil of the certain one phase and a non-energized period of a coil of the other phases adjacent thereto is formed to be substantially a triangular shape wherein the current value becomes zero on the non-energized period side of the coil, whereby the coil currents of the respective phases are made to be continuous over all cycles.

29. The motor driving method according to claim 10, wherein motor driving is performed in a manner that a phase difference between the coil current waveform of the respective phases and the torque constant waveform of the respective phases is maintained to be substantially a constant angle.

30. The motor driving method according to claim 10, wherein one cycle of the continuous current waveforms of the respective phases having the non-energized periods includes an non-energized period, a subsequent slow-sloped current increase period, a subsequent sharp-sloped current increase period, a subsequent maximum current period, a subsequent sharp-sloped current decrease period, a subsequent slow-sloped current decrease period, a subsequent non-energized period, a subsequent slow-sloped current decrease period, a subsequent sharp-sloped current decrease period, a subsequent minimum current period, a subsequent sharp-sloped current increase period, a subsequent slow-sloped current increase period, and a subsequent non-energized period.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to multiphase-motor driving and control techniques. More specifically, the invention relates to a motor driving apparatus and a motor driving method for a rotor-position sensorless motor having no rotor position sensor such as a Hall-effect device for sensing a rotor position.

2. Description of Related Art

In recent years, in sensorless driving of a small three-phase motor, switching timing of an energized-phase is controlled by providing a non-energized period (also referred to as "current-OFF period", hereinafter) in which a coil current of one phase in a "Y" connection (i.e., "star connection") coil is set to zero. More specifically, energized-phase switching timing is controlled by detecting zero crossings of back electromotive voltages associated with rotor rotation which are generated in an inter-terminal potential difference between both terminals, namely between an energization terminal and a neutral point terminal, of the coil of the phase during the non-energized period.

Conventionally, when abrupt current variations occur in switching of an energized-phase, there arise vibrations and noises to be drawbacks. In order to reduce such vibrations, noises, and the like, for example, Patent document 1, i.e., Japanese Patent No. 2892164 discloses a method for smoothing current variations. FIG. 11 shows a basic circuit configuration as disclosed in the patent document. Referring to FIG. 11, reference numeral 16 denotes a rotor position detector section which includes three comparators 24 corresponding to three phases (U, V, and W phases) and a phase-processing logic circuit 23. The inter-terminal potential differences of the respective motor coils during the non-energized periods are compared by the comparators 24, and converted by the phase-processing logic circuit 23 to a rotor phase information signal.

In the configuration of FIG. 11, three phase driving current waveforms 101, 102, and 103 of a sensorless motor are obtainable as shown in FIG. 12 in a phase-switching trapezoidal wave synthesizer section 21. These three phase driving current waveforms are formed to be smooth as trapezoidal wave shapes, and have non-energized periods Ta, Tb, Tc, Td, Te, and Tf for reading back electromotive voltages of coil terminals in order to detect the rotor position.

In addition, Patent document 2, i.e., Japanese Unexamined Laid-open Patent Publication No. 2003-174789 discloses a technique as outlined herebelow. This configuration includes a PWM (pulsewidth modulation) control section that generates PWM control pulses independent of each other and that performs PWM control, in parallel for two phases, of energization of a phase determined by an energization switching section. The configuration further includes a comparator section that performs comparison between a current detection signal indicative of a level of current flowing to a motor coil and various torque command signals generated by a torque command signal generator section. By determining an ON period of the PWM control pulse, the switching of the phase current is performed smoothly in the range from a low torque to a high torque, thereby reducing the motor vibrations and noises generated due to sharp changes in phase current. More specifically, according to Patent document 2, one phase coil terminal, except for a neutral point 4, is fixed to either one of a high potential and a low potential, and driving transistors of the remaining two phase coil terminals are alternately time-divided to be ON state so as to reach respective target current values or the sum current value thereof. Thus, these two phase coil current values are controlled, and an opposite-sign current obtained by summing the two phase currents is set as the current of the potential-fixed coil.

However, according to these conventional techniques, as shown in FIG. 11 for example, in the "Y"-connected three phase motor coils, there is not provided a driving transistor directly connected to the neutral point 4. In addition, the publication document does not discloses a technique for reducing the vibration and noise of the motor under controlling the coil current waveform of the other two phases in the energized state in the intervals Ta, Tb, Tc, Td, Te, and Tf wherein the coil of only any one of phases is in the non-energized state.

As in the conventional examples shown in FIGS. 11 and 12, even when coil current profiles of the individual phases are simply controlled to be trapezoidal wave shapes provided with non-energized intervals, significant vibrations and the noises are still generated. A reason therefor is that the motor vibration and noise are significantly dependent on components of a force that acts in the motor shaft direction between the rotor and the stator, wherein the current waveform includes a large amount of the vibration components acting in the shaft direction. When the motor rotor is virtually displaced in the shaft direction with respect to the motor stator, the magnetic flux across the respective phase coils is varied. Generally, the variation rate of such magnetic flux has the same waveform as the total magnetic flux across a corresponding phase coil. Hereafter, the magnetic flux variation rate will be referred to as either "magnetic flux variation rate in the motor shaft direction" or "shaft direction force constant". Different from a force (torque) acting in the rotation direction, the magnetic flux variation rate in the motor shaft direction applies as a force acting in the motor shaft direction, the force acting in the shaft direction is remarkably influenced by the current variation in a time region where the current exhibits a zero crossing. As such, the existence of the non-energized period of a coil causes a residue of shaft-direction vibration components having an amplitude of a non-negligible level, resulting in that sufficient suppression of the vibration, the noise, and the like can not be achieved.

Referring to FIGS. 13A to 13C, factors for not sufficiently suppressing the vibration and the noise of the motor having the non-energized periods in the coil current will be described referring to the case of a three-phase motor as an example. FIG. 13A includes the three phase driving current waveforms 101, 102, and 103, which are the same as those shown in FIG. 12. The three phase driving current waveforms represent first phase (U phase), second phase (V phase), and third phase (W phase) coil current waveforms each having a trapezoidal-wave shaped current waveform. Each of the three phase driving current waveforms 101, 102, 103 has a period wherein the coil current becomes zero, i.e., non-energized state in a period in the vicinity of the zero crossing of the respective current. Ta denotes a non-energized period in a current increasing region included in the coil current of the first phase, Tb denotes a non-energized period in a current increasing region included in the coil current of the second phase, and Tc denotes a non-energized period in a current increasing region included in the coil current of the third phase. Td denotes a non-energized period in a current decreasing region included in the coil current of the third phase, Te denotes a non-energized period in a current decreasing region included in the coil current of the first phase, and Tf denotes a non-energized period in a current decreasing region included in the coil current of the second phase.

It can easily be known that the summation of the respective phase coil currents 101, 102, and 103 results in a current value of zero as shown in FIG. 13A. This is an inevitable consequence of the case without driving means for directly driving the neutral point. Reference numeral 104 represents the waveform of the magnetic flux variation rate (shaft direction force constant) of the first phase with respect to the motor-shaft direction variation rate. The magnetic flux variation rate waveform 104 is approximately represented as a waveform proportional to a sine wave that is different in phase by an electrical angle of 90.degree. from a sine wave component of a fundamental wave of the first phase coil current waveform 101. Generally, the magnetic flux variation rate relative to a displacement in a motor shaft direction can be said to be proportional to a sine waveform that is different in phase by an electrical angle of 90.degree. from the magnetic flux variation rate relative to a displacement in the motor rotation direction. The magnetic flux variation rate relative to the motor-rotation-directional displacement is alternatively called a torque constant, and is distinguished from the shaft direction constant or the magnetic flux variation rate relative to the above-described motor-shaft direction displacement.

As such, a torque constant waveform in units of the respective phase coil current is represented in the form of a sine wave matching in phase with the fundamental wave of the respective phase coil current, and the shaft direction force constant in units of the respective phase coil current is represented in the form of a sine wave 90.degree. delayed in phase from the respective torque constant waveform. The product of the multiplication of the first phase coil current 101 times the magnetic flux variation rate (shaft direction force constant) 104 relative to the motor-shaft direction displacement represents the motor-shaft direction force with respect to the first phase coil current. Although not shown in the drawings, similarly as in the case of the first phase, the second phase magnetic flux variation rate relative to a motor-shaft direction displacement is approximately represented proportional to a sine waveform that is different in phase by an electrical angle of 90.degree. from the second phase coil current 102, and the product of the multiplication of the two values represents a motor-shaft direction force with respect to the second phase.

Similarly, third phase magnetic flux variation rate relative to the motor-shaft direction displacement is approximately represented proportional to a sine waveform that is different in phase by an electrical angle of 90.degree. from the third phase coil current 103, and the product of the multiplication of the two values represents a motor-shaft direction force with respect to the third phase. Motor-shaft direction forces of individual phase coil currents of the first, second, and third phases are shown by waveforms 105, 106, and 107 in FIG. 13B. A synthetic motor-shaft direction force obtained by summing the motor-shaft direction forces 105, 106, and 107 of the three phases is shown by a waveform 108 in FIG. 13C. In the non-energized periods represented by Ta, Tb, Tc, Td, Te, and Tf, as shown in the synthetic motor-shaft direction force 108 in FIG. 13C, it can be known that vibration components of the shaft direction forces remain uncancelled. These result in residues of the vibration and noise.

In the example of FIGS. 13A to 13C, the shaft direction force remains in a period other than the above-described non-energized periods. This is because a current peak period (or, a current bottom period) representatively represented by 109 of FIG. 13A is long, and therefore the deviation from the sine wave having the trapezoidal waveform is large. This results in residues of the vibration and noise, similar to the above. As such, when the current peak period/current bottom period 109 is longitudinally steered to be an electrical angle of about 60.degree., the shaft direction force is reduced in a period other than the non-energized period.

In the motor driver circuit described in the conventional techniques, no driving transistor for directly driving the neutral point is connected in the "Y"-connected three phase motor coils. Accordingly, the total sum of the three phase coil currents becomes zero, and a coil-current freedom degree is 2. More specifically, when the coil current of one phase is set to zero to be in non-drive state, the freedom degree of the remaining two phases is only 1. Ordinarily, conventional driving methods are of the type restricted in the freedom degree, as described above. Consequently, according to motor driving with only the freedom degree of 2, for example, in the first-phase non-energized period Ta, the current values of the second-phase coil current 102 and the third-phase coil current 103 need to be identical to each other with the polarities opposite each other. This restriction makes it difficult to sufficiently reduce the vibration and noise of the motor including the non-energized periods.

According to the conventional configuration, the driving transistor for directly driving the neutral point of the "Y"-connected motor coils is not provided while the freedom degree of the three phase coil currents is 2, and therefore the residues of the vibration and the noise are sizable, that is, the residues are not sufficiently suppressed. Under constraints where, in the first-phase non-energized periods Ta and Te, both the current values, namely, the second-phase coil current 102 and the third-phase coil current 103, have the opposite polarities and the identical magnitudes, it can easily be inferred from the waveforms of the shaft direction force components attributed to the respective phase coil currents that the synthetic motor-shaft direction force 108 can never be sufficiently suppressed.

SUMMARY OF THE INVENTION

The invention is made to solve the problems described above. Accordingly, an object of the invention is to provide a motor driving apparatus and a motor driving method, wherein, for example, in a three-phase motor having non-energized periods, the freedom degree of three-phase current waveforms can be made to 3, and non-energized periods of respective phase coil currents for detecting a sensorless-motor rotor position are provided, so that the vibration and the noise are sufficiently reduced.

In order to achieve the above object, a motor driving apparatus according to one aspect of the invention drives a multiphase motor by controlling energization to motor driving coils of multiple phases. The apparatus comprises: a rotor position detector section for obtaining rotor position information by detecting back electromotive voltages induced in a motor driving coil of a non-energized phase; a half bridge circuit group including pairs of high-potential-side driving transistors and low-potential-side driving transistors respectively connected to both terminals of the motor driving coils; a torque command signal generator section for generating torque command signals for motor driving in accordance with original torque command signals input from the outside and output signals of the rotor position detector section; an energization control signal generator section for generating energization control signals for driving each phase coil in accordance with the command signals generated by the torque command signal generator section; and an energization control section which is supplied with the energization control signals and controls the energization of the motor driving coils of the multiple phases at a predetermined cycle in accordance with the supplied energization control signals.

In this configuration, the energization control section sets an non-energized period during which only one motor driving coil of the motor driving coils of the multiple phases is set to an non-energized state, so that the motor driving is performed in a manner such that a total of coil currents of the multiple phases is not zero in the non-energized period.

In the configuration described above, preferably, the motor driving coils of the multiple phases include a neutral point of star-connected common connection terminal, and the half bridge circuit group includes the high-potential-side driving transistors and the low-potential-side driving transistors that are connected also to the side of the neutral point terminal. In the cases of linear voltage driving and voltage PWM driving, the torque command signal generator section generates voltage target values of the coil terminals of the respective phases and the neutral point. For the linear current driving, the torque command signal generator section generates current target values of the coil terminals of the respective phases and the neutral point. For the PWM driving, the torque command signal generator section generates the target current values of the respective phases and a flow-out/in current of the neutral point and the target current value of the total currents obtained by synthesizing thereof. Thereby, motor driving for the neutral point terminal is performed in the non-energized period during which the coil current of any of the phases is set to zero.

A motor driving method according to another aspect of the present invention drives a multiphase motor by controlling energization of motor driving coils of multiple phases and by performing driving control of high-potential-side driving transistors and low-potential-side driving transistors. The method comprising the steps of: obtaining rotor position information by detecting back electromotive voltages induced in a motor driving coil of a non-energized phase; generating torque command signals for motor driving in accordance with original torque command signals input from the outside and the obtained rotor position information; generating energization control signals for driving each phase coil in accordance with the generated torque command signals; and controlling the energization of the motor driving coils of the multiple phases at a predetermined cycle in accordance with the energization control signals.

In this method, in the energization controlling step, there is set an non-energized period during which only one motor driving coil of the motor driving coils of the multiple phases is set to an non-energized state, so that the motor driving is performed in a manner such that a total of coil currents of the multiple phases is not zero in the non-energized period.

The motor driving apparatus and the motor driving method according to the invention individually include the cases of the linear driving and the PWM driving. In the case of the PWM driving, pulse modulation control signals to be described in the embodiments are used for the energization control signals.

According to the invention, with the configuration described above, in a non-energized period of a coil of a certain phase, when forces acting in the shaft direction induced by the coil current of the other phases are synthesized, vibration components of the forces acting in the shaft direction are cancelled from one another. Thereby, in total, the vibration and noise can be suppressed, and the motor driving apparatus and the motor driving method having the functionalities of reducing vibration and noise can be implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a circuit diagram showing a motor driving apparatus according to an embodiment 1 of the invention;

FIG. 2 is a circuit diagram showing a motor driving apparatus according to an embodiment 2 of the invention;

FIG. 3 is a circuit diagram showing a motor driving apparatus according to an embodiment 3 of the invention;

FIGS. 4A, 4B and 4C are views showing coil current waveforms, shaft direction magnetic flux variation curves, and shaft direction forces, respectively, in the case where only zero-crossing neighborhoods of a sine-wave shaped coil current are non-energized;

FIGS. 5A, 5B and 5C are views descriptive of a motor driving method relative to the coil current in an embodiment 4 of the invention;

FIGS. 6A and 6B are views descriptive of driving of other two phases and a neutral point in the case where one phase is in a non-energized period which is being adapted to the respective embodiment of the invention;

FIGS. 7A and 7B are views descriptive of coil current waveforms, shaft direction magnetic flux variation curves, and shaft direction forces in the non-energized period in the embodiment 4 of the invention;

FIGS. 8A, 8B, 8C, 8D and 8E are views descriptive of coil current waveforms, shaft direction magnetic flux variation curves, and shaft direction forces in the non-energized period in the embodiment 5 of the invention;

FIGS. 9A, 9B, 9C, 9D and 9E are views descriptive of coil current waveforms, shaft direction magnetic flux variation curves, and shaft direction forces in the non-energized period in the embodiment 6 of the invention;

FIGS. 10A, 10B and 10C are views descriptive of a motor driving method relative to the coil current in an embodiment 7 of the invention;

FIG. 11 is a circuit diagram showing a conventional motor driving apparatus of a sensorless type;

FIG. 12 is a view showing three phase coil current waveforms in the conventional sensorless type; and

FIGS. 13A, 13B and 13C are views showing coil current waveforms, shaft direction magnetic flux variation curves, and shaft direction forces, respectively, in the conventional sensorless type.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described herebelow referring to the accompanying drawings. Common elements in the individual drawings are shown using the same characters, and repeated descriptions are omitted herefrom. Generally, PWM (pulsewidth modulation) driving methods, linear driving methods, and the like methods are widely used for motor driving. The PWM driving method includes a type termed a "voltage PWM driving method," which pulsewidth modulates weighted voltage values in a configuration as shown in FIG. 1, and a type termed "current PWM driving method," which directly controls a current value in units of a respective driving transistors as shown in FIGS. 2 and 3 described below.

According to the voltage PWM driving method, a plurality of torque command signals are pulsewidth-modulated using a triangular wave signal, wherein each of the torque command signals has an amplitude defined in accordance with an amplified output of an error between a mean voltage (mean current) of a shunt resistor and an original torque command value TQ. The plurality of torque command signals are, for example, three phase signals when neutral point driving is not performed, or signals with which, using one phase set to a reference potential, when a combination of the remaining two phases causing the potential difference to vary with respect to the reference potential is alternated in units of 120.degree.. When the neutral point driving is performed, the torque command signals are obtained by modulating four signals consisting of three phase signals and the neutral point signal. Alternatively, the torque command signals are obtained by dividing an interval, wherein one phase is set to a reference potential in units of the divided intervals, and the other phase signals are set as signals having voltage values as relative differences so that the signals are modulated. In comparison, the current PWM driving method is a method that uses a PWM scheme, wherein multiple command signals of amplitudes proportional to the original torque command values TQ are formed, so that switch-off is performed upon detection of a match between the respective command and the current of the shunt resistor in time division. The multiple command signals include three phase coil currents, neutral-point flow-out/in current, and a current obtained by summing a plurality of currents thereamong.

EMBODIMENT 1

FIG. 1 shows an essential portion of a circuit configuration of a motor driving apparatus according to the embodiment 1 of the invention. The motor driving scheme of the invention is characterized as follows. Multiple phase motor driving coils include a neutral point working as a star-connected common connection terminal. A half bridge circuit group includes high-potential-side and low-potential-side transistors in pairs connected also to the neutral point terminal side. It is noted here that the term "half bridge circuit group" indicates a plurality of half bridge circuits each including a pair of high-potential-side and low-potential-side transistors in series in the description. During an non-energized period wherein only one motor coil of the multiple phase motor driving coils is set to a non-energized state, a driving current is also applied to the neutral point terminal. During an all-coil energized period wherein the current is flowed to all the motor driving coils, the neutral point set to the non-energized state wherein driving current is not applied to the neutral point terminal.

Referring to FIG. 1, Tr1 and Tr2, respectively, denote a high-potential-side driving transistor and low-potential-side driving transistor connected in common to a terminal 1 of a motor coil 9 of a first phase (U phase). Tr3 and Tr4, respectively, denote a high-potential-side driving transistor and low-potential-side driving transistor commonly connected to a terminal 2 of a motor coil 10 of a second phase (V phase). Tr5 and the Tr6 denote a high-potential-side driving transistor and low-potential-side driving transistor commonly connected to a terminal 3 of the motor coil 11 of a third phase (W phase). Further, Tr7 and the Tr8, respectively, denote a high-potential-side driving transistor and low-potential-side driving transistor commonly connected to the neutral point terminal 4 to which the three motor coils 9, 10, and 11 are commonly "Y"-connected. The high potential side is a source current side (draw-out side of the respective phases) to which a current of a voltage Vcc is supplied; and the low potential side is a sink current side (draw-in side of the respective phases). A diode is connected between a drain and a source of each of the driving transistors in the direction along which regenerative current flows. In the case where the motor driving transistor is of the CMOS or DMOS type, the diode may be a parasitic diode existing between a body and a drain of the motor driving transistor.

Reference numeral 12 denotes a current-detecting shunt resistor for detecting the total current of the low potential-side driving transistors. Alternatively, the current detecting shunt resistor may be configured to detect the total current of the high-potential-side driving transistors. Reference numeral 13 denotes a current-detection amplifier section that amplifies both-end voltages of the current detecting shunt resistor 12; reference numeral 14 denotes a pre-drive section; reference numeral 15 denotes an energization switching section; reference numeral 16 denotes a rotor position detector section; reference numeral 17 denotes a triangular wave oscillator section; reference numeral 18 denotes a pulse modulation control signal generator section; reference numeral 19 denotes a torque command signal generator section for generating a torque signal in units of the respective phases; and reference numeral 20 denotes an error amplifier section. The error amplifier section 20 amplifies a difference between a signal obtained in accordance with a shunt-resistor inter-terminal potential difference and a signal obtained in accordance with an original torque command input signal TQ (also referred to as "torque command value," hereafter) being externally inputted.

The triangular wave oscillator section 17 is a circuit that generates a triangular wave signal for obtaining a timing of turning ON and OFF a PWM control signal of a neutral point output and three phase outputs of the pulse modulation control signal generator section 18. The pulse modulation control signal generator section 18 includes a comparator section formed of multiple comparators and performs a PWM control process to thereby generate PWM control signals, with which the energization switching section 15 applies the driving current to the neutral point terminal during the non-energized period, and does not apply the driving current to the neutral point terminal to be set in an non-energized state during the all-coil energized period in which the current is flowed through all the motor driving coils. As one embodiment of an interior configuration of the torque command signal generator section 19, the configuration may be formed to include an interval divider section 19a, a synthesizer section 19b, a phase control section 19c, an enable signal generator section 19d, a mode switching section 19e, and a counter (not shown) for obtaining a timing of a logic circuit (not shown) regarding the respective phase waveforms.

The divider section 19a divides the electrical angle of 360.degree. into predetermined intervals of the electrical angle based on the rotor position information. The purpose of the division is to set a target value of a control amount, thereby performing appropriate and rational control in units of the predetermined intervals of the electrical angle. The synthesizer section 19b gives a voltage target value in units of the intervals to each of the phase coil terminals including the neutral point and generates a basic profile of the torque command signal, thereby generating the torque command signal formed by proportionally reflecting an output of the error amplifier section 20, to be supplied to the pulse modulation control signal generator section 18. The phase control section 19c is a phase shift means that is used when necessary. The mode switching section 19e performs a switching operation between a so-called start mode and a detection mode in the sensorless motor driving in accordance with the output set by the counter (not shown). With the torque command signal generator section 19 configured as described above, variations in the three voltages and the neutral point voltage with respect to phase angle variations are formed as signal waveforms having an amplitude proportional to the output from the error amplifier section 20, whereby various torque command signals are generated in synchronism with the cycle of rotor position signals (binary signals).

For example, a rotor phase detection signal inputted to the interval divider section 19a is divided in units of a predetermined electrical angle to generate divided signals, and the synthesizer section 19b allocates a predetermined voltage value corresponding to a thus-divided signal in units of a predetermined electrical angle interval in accordance with the rotor phase detection signal. Since the present embodiment is an example in the case of the voltage driving, the current waveform is delayed in phase relative to the voltage waveform. The phase control section 19c shifts the respective voltage waveforms generated by the synthesizer section 19b, by a predetermined value if necessary, thereby generating respective-phase dedicated input torque command signals. Thus, the phase of the fundamental wave of the respective phase coil currents can be matched with the respective phase torque constant waveforms represented by a sine wave. Further, a countermeasure can be taken to suppress the vibration and the noise in the shaft-direction force constant waveform in units of the respective phase coil currents represented by a sine wave delayed in phase by an electrical angle of 90.degree. from the respective torque constant waveform.

The enable signal generator section 19d is provided to output the timing signal to the rotor position detector section in order to prevent an error in the back-electromotive-voltage detection of a back electromotive voltage working as the rotor position signal from occurring because of, for example, a switching noise transferred from the driving transistors. The enable signal generator section 19d uses a signal generated by the pulse modulation control signal generator section 18 in order to generate the timing signal. The mode switching section 19e determines whether or not to perform commutation in accordance with the back electromotive voltage by determining whether or not the back electromotive voltage increases to a sufficient level. If not in accordance with the back electromotive voltage, the mode enters the start mode. Although the operation of the start mode is not described herein in detail, such a method is well known as that, for example, synchronized operations are performed using commutation with a predetermined cycle until the back electromotive voltage reaches a detectable level, and the driving current is applied to an appropriate phase predicted from a response signal to an input of a rotor position searching pulse.

The operation of the motor driving apparatus shown in FIG. 1 will be described herebelow. Three phase motor coil terminal voltages and a neutral point terminal voltage are inputted to the rotor position detector section 16. Specifically, the voltage signal of the common connection node 1 of the transistors Tr1 and Tr2, the voltage signal of the common connection node 2 of the transistors Tr3 and Tr4, the voltage signal of the common connection node 3 of the transistors Tr5 and Tr6, and the voltage signal of the common connection node 4 of the transistors Tr7 and Tr8 are inputted to the rotor position detector section 16. Then, the inter-terminal potential difference in the non-energized period of each motor coil is compared by the comparator 24, and a proper signal is extracted by the logic circuit 23 from the comparator 24 using the enable signal received from the enable signal generator section 19d. Thus, the extracted signal is converted to a proper rotor phase information signal, and the rotor phase information is supplied to the respective-phase dedicated input torque command signal generator section 19.

More specifically, the rotor position detector section 16 compares the potential difference between the both terminals 1 and 4 of the motor coil 9 in the non-energized period of the motor coil 9 of the first phase (U phase), compares the potential difference between the both terminals 2 and 4 of the motor coil 10 in the non-energized period of the motor coil 10 of the second phase (V phase), and compares the potential difference between the both terminals 3 and 4 of the motor coil 11 in the non-energized period of the motor coil 11 of the third phase (W phase). Thereby, the rotor position detector section 16 detects the respective rotor positions. The rotor position detection method itself according to the back voltage detection method of detecting the inter-terminal back voltage of the respective coils in the non-energized period is well known, and is disclosed in the patent document 1, for example.

Since the current detecting resistor 12 (shunt resistor) is provided, the total current of all the low-potential-side driving transistor currents can be detected. The voltage across the current detecting shunt resistor 12 is amplified in inter-terminal potential difference by the current-detection amplifier section 13, and then smoothed. A difference between an output of the current-detection amplifier section 13 and the original torque command value TQ applied from a torque input terminal is amplified by the error amplifier section 20. The amplified output value from the error amplifier section 20 and the rotor position information outputted from the rotor position detector section 16 are inputted to the respective-phase dedicated input torque command signal generator section 19. In accordance with the position information applied from the rotor position detector section 16, the torque command signal generator section 19 generates torque command voltages for the respective three phases and the neutral point while being amplitude-modulated in proportion to the outputs of the error amplifier section 20.

The input torque command signals for the respective three phases and the neutral point, which are outputted from the torque command signal generator section 19, are compared with the output signal of the triangular wave oscillator section 17 in the comparator section 18a of the pulse modulation control signal generator section 18. After undergoing the PWM control process, the output pulse modulation control signals become three phase PWM control signals including a neutral-point driving current control signal, and then inputted to the energization switching section 15. The pulse modulation control signal creator section 18 additionally includes a function of, for example, generating the PWM signal having undergone a shoot-through prevention treatment in association with the comparison processing, and signal generation for the prevention of erroneous detection of the rotor position information, and a function of outputting the generated signals to the rotor position detector section 16.

The torque command signal generator section 19 generates various torque command signals for generating appropriate currents to the individual phase coils through the energization switching section 15.

As described above, in the voltage PWM driving, the target current waveform capable of reducing the shaft direction force is weighted as the voltage waveform for the respective phases using the means shown by the blocks 19 and 20 in FIG. 1, and the voltage waveform is compared with the triangular wave in the comparator section 18a. Thus, the waveform is replaced with a duty ratio to perform the PWM driving.

The energization switching sec