Title: Electric power steering apparatus
Abstract: An electric power steering removes external wiring connecting between an electric motor and a control unit, whereby the influence of radiation noise caused by a PWM operation can be reduced. In addition, the heat radiation and assemblability of the electric motor and the control unit can be improved, while achieving high power output. A housing 64 with a metal substrate 61 fixedly secured thereto is arranged at a side opposite to an electric motor 30. The cooling fins are formed on an outer side of a housing 64 and on an outer side and an inner side of a cover 65. A metal substrate 61, a large current substrate 62 and a control substrate 63 are arranged inside of the housing 64 and the cover 65 in a laminated structure.
Patent Number: 6,906,483 Issued on 06/14/2005 to Tominaga, et al.
| Inventors:
|
Tominaga; Tsutomu (Tokyo, JP);
Fujimoto; Tadayuki (Tokyo, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
227272 |
| Filed:
|
August 26, 2002 |
Foreign Application Priority Data
| Mar 14, 2002[JP] | 2002/070240 |
| Current U.S. Class: |
318/293; 318/280; 318/287; 361/688; 361/752 |
| Intern'l Class: |
H02P 001/00; H02P001/22; H02P001/40; H02P003/00; H02P003/20 |
| Field of Search: |
318/293,139,254,256,280,287
361/688,752,704,600,679,709,711,722,717-720,748,807
180/280
|
References Cited [Referenced By]
U.S. Patent Documents
| 4218724 | Aug., 1980 | Kaufman.
| |
| 5602451 | Feb., 1997 | Kohge et al.
| |
| 5810111 | Sep., 1998 | Takeuchi et al.
| |
| 6201700 | Mar., 2001 | Tzinares et al.
| |
| 6548972 | Apr., 2003 | Takagi.
| |
| Foreign Patent Documents |
| 06270824 | Sep., 1994 | JP.
| |
| 08-192757 | Jul., 1996 | JP.
| |
| 09-030434 | Feb., 1997 | JP.
| |
| 09-117093 | May., 1997 | JP.
| |
| 10-243687 | Sep., 1998 | JP.
| |
| 11-115775 | Apr., 1999 | JP.
| |
| 2001/-196770 | Jul., 2001 | JP.
| |
Primary Examiner: Martin; David
Assistant Examiner: Santana; Eduardo Colon
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
1. An electric power steering apparatus equipped with an electric motor adapted
to output assist torque to a steering wheel of a vehicle, and a control unit for
controlling the driving of said electric motor,
said control unit comprising:
a power substrate mounting thereon a bridge circuit which includes a plurality
of semiconductor switching elements for switching current supplied to said electric
motor in accordance with a torque assisting said steering wheel;
capacitors for absorbing ripples contained in said current;
a control substrate mounting thereon a microcomputer which generates a drive
signal for controlling said bridge circuit based on at least steering torque of
said steering wheel;
a power connector electrically connected to a battery of the vehicle;
a signal connector adapted to input and output signals through external wiring;
a plurality of motor terminals electrically connected with said electric motor;
a large current substrate mounting thereon at least said capacitors and having
conductive plates forming wiring patterns and said motor terminals insert molded
thereto with an insulating resin; and
a housing and a cover in which said power substrate, said control substrate and
large current substrate are received;
wherein said power substrate, said power connector and said signal connector
are arranged in said housing in parallel with each other in an axial direction
of said electric motor, with said motor terminals being protruded outward from
said cover,
wherein said cover is fixedly secured to said housing in parallel to the axial
direction of said electric motor, and said motor terminals are inserted into said
electric motor and electrically connected with said electric motor.
2. The electric power steering apparatus according to claim 1, wherein said conductive
plates connected with said power connector are arranged in parallel with each other
substantially in the center of said large current substrate, and said capacitors
are arranged at the opposite side of said motor terminals with said conductive
plates interposed therebetween.
3. The electric power steering apparatus according to claim 1, wherein said electric
motor comprises a three-phase brushless motor, and switches each for switching
on and off a current supplied to said three-phase brushless motor through said
motor terminals are arranged in at least two ones of three parallel paths connecting
between said three-phase brushless motor and said bridge circuit.
4. The electric power steering apparatus according to claim 3, wherein said switches
are arranged in those two ones of the three parallel paths which are arranged on
opposite outer sides.
5. The electric power steering apparatus according to claim 3, wherein said switches
are connected with said paths by welding, with their welding locations being arranged
at a side opposite in a diametral direction of said electric motor to that side
at which said switches are connected with said motor terminals.
6. The electric power steering apparatus according to claim 1, wherein said power
substrate is fixedly secured to said housing while being covered with said large
current substrate, and said power substrate is of a laminated structure of three
layers in which said large current substrate and said control substrate are superposed
on said power substrate in this order in a direction toward said cover, said cover
being fixed to said housing to form an internally sealed structure, and said housing
and said cover have their mating surfaces located at a power substrate side of
the control substrate.
7. The electric power steering apparatus according to claim 1, wherein each of
said motor terminals has a narrow low-rigidity portion formed at its intermediate portion.
8. An electric power steering apparatus equipped with an electric motor adapted
to output assist torque to a steering wheel of a vehicle, and a control unit for
controlling the driving of said electric motor,
said control unit comprising:
a power substrate mounting thereon a bridge circuit which includes a plurality
of semiconductor switching elements for switching current supplied to said electric
motor in accordance with a torque assisting said steering wheel;
capacitors for absorbing ripples contained in said current;
a control substrate mounting thereon a microcomputer which generates a drive
signal for controlling said bridge circuit based on at least steering torque of
said steering wheel;
a power connector electrically connected to a battery of the vehicle;
a signal connector adapted to input and output signals through external wiring;
a plurality of motor terminals electrically connected with said electric motor;
a large current substrate mounting thereon at least said capacitors and having
conductive plates forming wiring patterns and said motor terminals insert molded
thereto with an insulating resin; and
a housing and a cover in which said power substrate, said control substrate and
large current substrate are received;
wherein said power substrate, said power connector and said signal connector
are arranged in said housing hi parallel with each other in an axial direction
of said electric motor, with said motor terminals being protruded outward from
said cover,
wherein said cover is formed with an opening through which said motor terminals
are exposed outwardly from said cover, with a lid of an insulating resin being
attached to an outer side of said cover, said lid having a plurality of penetration
holes through which said motor terminals are able to extend.
9. The electric power steering apparatus according to claim 8, wherein an adhesive
resin is filled into a gap between the outer periphery of said cover and said opening
and surroundings of those portions of said motor terminals which are protruded
from said cover.
10. The electric power steering apparatus according to claim 8, wherein said
electric motor comprises a three-phase brushless motor, and said lid is formed
with a connector housing of a sensor connector which is connected with a rotational
position sensor for detecting a rotational position of a rotor of said brushless motor.
11. The electric power steering apparatus according to claim 10, wherein a plurality
of sensor terminals connecting between said microcomputer and said rotational position
sensor are insert molded to said large current substrate, and said connector housing
is formed with a plurality of penetration holes through which one end portions
of said sensor terminals extend, the one end portions of said sensor terminals
being inserted into said penetration holes thereby to construct said sensor connector.
12. The electric power steering apparatus according to claim 11, wherein said
large current substrate has a first concave portion formed at a location adjacent
the one end portions of said sensor terminals, and said lid has a convex portion
which is formed at a location including said penetration holes for said sensor
terminals, and into which said first concave portion is inserted with a gap formed
therebetween, an adhesive resin being filled into said gap.
13. The electric power steering apparatus according to claim 12, wherein said
large current substrate has a second concave portion which is formed in the neighborhood
of said first concave portion, and into which said adhesive resin is able to flow.
14. The electric power steering apparatus according to claim 8, wherein said
lid has vent holes formed therethrough for fluid communication with an ambient atmosphere.
15. The electric power steering apparatus according to claim 14, wherein said
vent holes are equipped with a filter which permits the passage of air but blocks
the passage of water.
16. The electric power steering apparatus according to claim 15, wherein said
vent holes are formed at locations protruded from a surface of an adhesive resin
bonding said cover and said lid with each other.
17. The electric power steering apparatus according to claim 14, wherein said
lid is formed with a wall which protrudes from a surface of an adhesive resin bonding
said cover and said lid with each other, and said vent holes are formed inside
said wall.
18. The electric power steering apparatus according to claim 8, wherein a nut
is insert molded to said lid at a location at which said lid is electrically connected
with said electric motor.
Description
This application is based on Application No.2002-070240, filed in Japan on Mar.
14, 2002, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
2. Description of the Related Art
In general, in vehicles such as motor cars equipped with an electric power steering
apparatus, the steering torque applied to a steering shaft by an operator's steering
effort on a steering wheel is detected by a torque sensor so that a control unit
can control the current supplied to an electric motor operatively connected with
the steering shaft in accordance with the steering torque thus detected, thus causing
the electric motor to output a required amount of steering assist torque to the
steering shaft through a speed reducer.
FIG. 12 is a block diagram of an electric power steering apparatus which uses
a brushless motor as an electric motor.
This electric power steering apparatus includes an electric motor 1 which
outputs assist torque to the steering wheel (not shown) of a vehicle, a control
unit 6 which controls the operation of the electric motor 1, a battery
4 which supplies current to drive the electric motor 1, a torque
sensor 5 which detects the steering torque of the steering wheel, a motor
connector 15 which electrically connects the control unit 6 to the
electric motor 1, a power connector 16 which electrically connects
the battery 4 with the control unit 6, and a signal connector 17
which provides electrical connection between the electric motor 1, the torque
sensor 5 and the control unit 6.
The electric motor 1 has an armature winding 2 which is connected
in three phases to a stator (not shown) and a rotational position sensor 3
for detecting the rotational position of a rotor (not shown).
The control unit 6 includes three capacitors 7 of large capacities
(e.g., about 2200 μF×3) for absorbing ripple components of a motor current
IM flowing through the electric motor 1, a pair of shunt resistors 8
for detecting the motor current IM, a three-phase bridge circuit 10 which
is composed of a plurality of semiconductor switching elements (for instance, FETs)
Q1-Q6 for switching the motor current IM according to the magnitude
and direction of the assist torque, a coil 11 for removing electromagnetic
noise, and a control circuit 12.
The control circuit 12 includes a current detector 9 connected
across the serially connected shunt resistors 8 for detecting a current
flowing through the electric motor 1, and a microcomputer 13 for
calculating the assist torque generated by the electric motor 1 based on
a steering torque signal from the torque sensor 5, the microcomputer 13
also calculating the current corresponding to the assist torque by feeding back
the motor current IM and the rotational position of the rotor detected by the rotational
position sensor 3. The microcomputer 13 outputs a drive signal to
the bridge circuit 10 through a drive circuit 14 so as to control
the bridge circuit 10.
In addition, though not shown, the microcomputer 13 includes, in addition
to an AD converter, a PWM timer circuit and the like, a well-known self-diagnosis
function of self diagnosing at all times whether the system is working normally
and of interrupting the motor current IM when there takes place abnormality.
FIG. 13 is a cross sectional plan view of the essential portions of the electric
power steering apparatus with the circuit structure shown in FIG. 12. Here,
note that in order to avoid the complexity of the drawing, only major circuit elements
are illustrated while omitting peripheral circuit elements, wiring patterns, conductive
wires, etc.
In this figure, an insulated printed-circuit board 19 is mounted on the
bottom of a box-shaped metal frame 18 which has the functions of a shield
board and a heat sink concurrently. For instance, a heat sink 20 made of
aluminum is attached to one end face of the inner surface of the metal frame 18.
The capacitors 7, the shunt resistors 8, the coil 11, the
microcomputer 13, etc., are mounted on the insulated printed-circuit board
19. Also, on the insulated printed-circuit board 19, there are arranged
a plurality of conductive plates 21
a-21
e each having
a large width and a large thickness besides the above-mentioned wiring patterns.
In addition, the semiconductor switching elements Q1-Q6 are fixedly
attached to one end face of the heat sink 20.
Now, the operation of the electric power steering apparatus as constructed above
will be described below.
The microcomputer 13 receives an output signal from the torque sensor
5 representative of the steering torque, an output signal from the rotational
position sensor 3 representative of the rotational position of the rotor
of the electric motor 1, and the motor current IM fed back thereto from
the shunt resistors 8 through the current detector 9, and generates
a rotational direction instruction for power steering and a current control quantity
corresponding to the assist torque, which are input to the drive circuit 14.
When the rotational direction instruction and the current control quantity are
input from the microcomputer 13, the drive circuit 14 generates a
PWM drive signal and supplies it to the semiconductor switching elements Q1-Q6
of the bridge circuit 10. As a result, a current flows from the battery
4 to the electric motor 1 through external wiring, the power connector
16, the coil 11, the bridge circuit 10, the motor connector
15 and another external wiring, so that the electric motor 1 generates
a required quantity of assist torque in a required direction.
At this time, the motor current IM flowing through the electric motor 1
is detected by means of the shunt resistors 8 and the current detector 9,
and fed back to the microcomputer 13 so that it is controlled to be equal
to a motor current instruction Im. In addition, the motor current IM contains ripple
components which would be generated by the switching operation of the bridge circuit
10 when the bridge circuit 10 is driven to operate in a PWM manner,
but it is controlled to be smoothed by means of the large-capacity capacitors 7.
Moreover, the coil 11 serves to prevent the noise, which would be generated
by the above-mentioned switching of the bridge circuit 10 during the PWM
operation thereof, from being radiated outside to cause radio noise.
In the electric power steering apparatus as described above, the value of the
motor current IM to be controlled is about 25-30 A in case of light cars but it
reaches such a value as high as about 60-80 A in compact cars.
The control unit 6 of this electric power steering apparatus is installed
in the passenger's compartment of an excellent environment in the vehicle, which
is remote from the engine room thereof where the electric motor 1 and the
battery 4 are arranged.
Accordingly, a plurality of long wires or cables are required for providing
electrical connection between the control unit 6 and the electric motor
1. As a result, there arises a problem that the cost of manufacture becomes
high and the weight of the vehicle increases.
In addition, if the length of wiring is extended, there takes place another problem
in that a power loss is increased and radiation noise generated due to the PWM
operation of the bridge circuit 10 is increased as well. Also, the increased
radiation noise might cause a malfunction of other control equipment, radio noise, etc.
Furthermore, the size of the semiconductor switching elements Q1-Q6
constituting the bridge circuit 10 in the control unit 6 increases
in accordance with the increasing magnitude of the motor current IM. It is also
necessary to control the generation of heat at the time of the plurality of semiconductor
switching elements Q1-Q6 being turned on or subjected to the PWM
switching operation by arranging them in parallel with each other. Thus, the size
of the heat sink 20 has to be increased to improve the radiation of heat
from the semiconductor switching elements Q1-Q6. Moreover, the sizes
of the respective electronic members employed in various parts of the apparatus
increase in proportion to the increasing motor current IM, and hence it is required
to physically or practically increase the length of a wiring pattern extending
from terminals of the power connector 16 to ground by way of the coil 11,
the bridge circuit 10 and the shunt resistors 8 as well as the length
of a wiring pattern extending from the bridge circuit 10 to the motor connector 15.
As a result of the various reasons as referred to above, there arise the following
additional problems. That is, the size of the control unit 6 is necessarily
enlarged; the magnitude of the motor current IM is decreased by voltage drops in
the respective wiring patterns; and the durability of the wiring patterns is reduced
by the heat generated.
SUMMARY OF THE INVENTION
The present invention is intended to solve the above-mentioned variety of problems,
and has for its object to provide an electric power steering apparatus which is
capable of reducing the influence of radiation noise caused by PWM driving, decreasing
the cost and weight thereof and generating large output power.
In order to achieve the above object, the present invention resides in an electric
power steering apparatus equipped with an electric motor adapted to output assist
torque to a steering wheel of a vehicle, and a control unit for controlling the
driving of the electric motor. The control unit includes: a power substrate mounting
thereon a bridge circuit which includes a plurality of semiconductor switching
elements for switching current supplied to the electric motor in accordance with
a torque assisting the steering wheel; capacitors for absorbing ripples contained
in the current; a control substrate mounting thereon a microcomputer which generates
a drive signal for controlling the bridge circuit based on at least steering torque
of the steering wheel; a power connector electrically connected to a battery of
the vehicle; a signal connector adapted to input and output signals through external
wiring; a plurality of motor terminals electrically connected with the electric
motor; a large current substrate mounting thereon at least the capacitors and having
conductive plates forming wiring patterns and the motor terminals insert molded
thereto with an insulating resin; and a housing and a cover in which the power
substrate, the control substrate and large current substrate are received. The
power substrate, the power connector and the signal connector are arranged in the
housing in parallel with each other in an axial direction of the electric motor,
with the motor terminals being protruded outward from the cover.
According to the above arrangement, it is possible to reduce the height
or the size in the vertical direction of the apparatus, without causing no interference
between the power substrate, the power connector and the signal connector. In addition,
the housing is arranged on the opposite side of the heat-generating electric motor
so that the heat inside the control unit can be effectively radiated. As a result,
the durability and heat resistance of the apparatus are improved.
The above and other objects, features and advantages of the present invention
will become more readily apparent to those skilled in the art from the following
detailed description of preferred embodiments of the present invention taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view showing an electric power steering apparatus
according to a first embodiment of the present invention.
FIG. 2 is a block diagram of the electric power steering apparatus of FIG. 1.
FIG. 3 is an exploded perspective view of the electric power steering apparatus
of FIG. 1.
FIG. 4 is an exploded perspective view of a control unit shown in FIG. 1.
FIG. 5 is a cross sectional view of the control unit of FIG. 1.
FIG. 6 is a plan view of a large current substrate of FIG. 4 when seen from
one side thereof.
FIG. 7 is a rear view of the large current substrate of FIG. 6.
FIG. 8 is a cross sectional view of a part of the control unit of FIG. 1.
FIG. 9 is a cross sectional view of a part of the control unit of FIG. 1.
FIG. 10 is a cross sectional view of a part of a modification of the control
unit of FIG. 1.
FIG. 11 is a cross sectional view showing a part of an electric power steering
apparatus according to a second embodiment of the present invention.
FIG. 12 is a block diagram showing a known electric power steering apparatus.
FIG. 13 is a cross sectional plan view of the essential portions of the known
electric power steering apparatus with a circuit structure shown in FIG. 12.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, preferred embodiments of the present invention will be described below
in detail while referring to the accompanying drawings.
In the respective figures to be referred to below, the same symbols are attached
to the same or corresponding parts or elements as those of the known apparatus
shown in FIG.
12 and FIG.
13.
Embodiment 1.
FIG. 1 is a cross sectional view which shows an electric power steering apparatus
according to a first embodiment of the present invention. FIG. 2 is a block diagram
of the electric power steering apparatus of FIG.
1. FIG. 3 is an exploded
perspective view of the electric power steering apparatus of FIG.
1. FIG.
4 is an exploded perspective view of a control unit
60 of FIG.
1.
FIG. 5 is a cross sectional view of the control unit
60 of FIG.
1.
FIG. 6 is a plan view of a large current substrate
62 of FIG. 4 when seen
from one side thereof. FIG. 7 is a rear view of FIG.
6. FIG.
8 and
FIG. 9 are cross sectional views of a part of the control unit
60 of FIG.
1.
The electric power steering apparatus illustrated includes an electric motor
30 which outputs assist torque to the steering wheel (not shown) of a vehicle,
a control unit
60 which controls the operation of the electric motor
30,
a battery
4 which supplies current to the electric motor
30 for driving
thereof, a torque sensor
5 which detects the steering torque of the steering
wheel, and connectors
68,
74 and
74a for receiving
and outputting signals.
The electric motor
30 in the form of a three-phase brushless motor includes
an output shaft
32, a rotor
33 with a permanent magnet
31
having
8 magnetic poles fixedly attached to the output shaft
32,
a stator
36 arranged around the rotor
33, and a rotational position
sensor
3 arranged at an output side of the output shaft
32 for detecting
the rotational position of the rotor
33.
The stator
36 includes twelve salient poles
34 arranged in confrontation
with the outer periphery of the permanent magnet
31, insulators
35
attached to the opposite sides of the salient poles
34, respectively, an
armature winding
2 which is wound around the insulators
35 and which
consists of winding components (
2u,
2v,
2w)
of three phases U, V and W. The armature winding
2 has three ends of three
phases connected to three winding terminals
37, respectively, which extend
in the axial direction of the output shaft
32.
The rotational position sensor
3 is comprised of a resolver, and has a
rotor
3a and a stator
3b. The outside shape or profile
of the rotor
3a is formed into a special curve such that the permeance
of a diametral or radial gap defined between the stator
3b and the
rotor
3a changes like a sine wave in accordance with the angle of
rotation of the rotor
3a with respect to the stator
3b.
An exciting coil and two output coils are wound around the stator
3b
so as to detect a change in the diametral gap (i.e., a change in the radial
distance) between the rotor
3a and the stator
3b to
generate output voltages of two phases which change in a sine curve and in a cosine
curve, respectively.
A speed reduction gear
50 is fixedly mounted on the electric motor
30.
The speed reduction gear
50 includes a gear case
51 connected with
a bracket
39 of the electric motor
30, a worm gear
52 arranged
in the gear case
51 for reducing the rotational speed of the output shaft
32, and a worm wheel
53 which is in meshing engagement with the worm
gear
52. The worm gear
52 is formed at its one end with an outer
spline, and a coupling
38 having an inner spline formed on its inner surface
is press fitted over an end of the output shaft
32, so that the splined
end of the worm gear
52 is fitted into the coupling
38 to provide
spline engagement, through which the torque of the electric motor
30 is
transmitted to the speed reduction gear
50.
The control unit
60 includes three capacitors
7 of large capacities
(e.g., about 2200 μF×3) for absorbing ripple components of a motor current
IM flowing through the electric motor
30, a pair of shunt resistors
8
for detecting the motor current IM, a three-phase bridge circuit
10 which
is composed of a plurality of semiconductor switching elements (for instance, FETs)
Q
1-Q
6 for switching the motor current IM according to the magnitude
and direction of the assist torque, a coil
11 for removing electromagnetic
noise, and a control circuit
12.
The control circuit
12 includes a current detector
9 connected
across the serially connected shunt resistors
8 for detecting a motor current
IM flowing through the electric motor
30 and a microcomputer
13 for
calculating the assist torque generated by the electric motor
30 based on
a steering torque signal from the torque sensor
5, the microcomputer
13
also calculating the current corresponding to the assist torque by feeding back
the motor current IM and the rotational position of the rotor detected by the rotational
position sensor
3. The microcomputer
13 outputs a drive signal to
the bridge circuit
10 through the drive circuit
14 so as to control
the bridge circuit
10.
The control unit
60 includes a metal substrate
61 acting as a power
substrate, a large current substrate
62 having a plurality of conductive
wires and conductive plates insert molded with an insulating resin, a control substrate
63 in the form of an insulated printed-circuit board, a housing
64
made of aluminum having high thermal conductivity, and a cover
65 which
is connected to the housing
64 and houses therein the metal substrate
61,
the large current substrate
62, the control substrate
63, etc.
The housing
64 and the cover
65 are arranged in parallel to the
axial direction of the electric motor
30 with the cover
65 being
fixed to the bracket
39 of the electric motor
30.
The metal substrate
61 is comprised of an HITT substrate (a brand name
of Denki Kagaku Kogyo K. K.) for example. That is, wiring patterns are formed on
an aluminum substrate of a thickness of 2 mm as a copper pattern of a thickness
of 100 μm through an insulating layer of a thickness of 80 μm. In addition,
mounted on the wiring patterns on the metal substrate
61 through soldering,
are switching elements Q
1-Q
6 which together constitute the bridge
circuit
10 for switching the current supplied to the electric motor
30,
large current parts such as the shunt resistors
8, etc., for detecting the
current which flows through the electric motor
30, and a connection member
66 which provides electrical connection between the metal substrate
61
and the large current substrate
62.
The connection member
66 has a plurality of connection terminals Cm, which
are formed by insert molding, for providing electrical connection between the metal
substrate
61 and the large current substrate
62, and between the
metal substrate
61 and the control substrate
63. Each of the connection
terminals Cm of the connection member
66 has its end portions Cm
1,
Cm
2 arranged in the form of a letter L, when viewed in a direction perpendicular
to the metal substrate
61, as show in FIG.
4.
The wiring patterns formed on the metal substrate
61 each have a cross
sectional capacity enough to accommodate or withstand a large current flowing therethrough,
so that circuit elements used for a large current flowing through the electric
motor
30 can be mounted.
Peripheral or surrounding circuit elements (small current parts) including
the microcomputer
13, the drive circuit
14 and the current detector
9 are mounted through soldering on the wiring patterns on the control substrate
63.
The wiring patterns on the large current substrate
62 are formed by a
plurality of conductive wires and conductive plates through insert molding of an
insulating resin. The plurality of conductive wires and conductive plates are exposed
from the insulating resin at locations for electrical connection.
Each of sensor terminals Sm for sending a signal from the rotational position
sensor
3 to the microcomputer
13 has one end portion Sm
2 exposed
from the insulating resin to be electrically connected with the control substrate
63, and the other end portion Sm
1 protruded from a hole
65a
in the form of an opening formed in the cover
65 to be electrically
connected with the rotational position sensor
3 of the electric motor
30.
A plurality of conductive plates
110 for electrically connecting between
the bridge circuit
10 and a power connector
68a to be described
later in detail are arranged in parallel with each other in the vicinity of the
center of the large current substrate
62, as shown in FIG.
6 and
FIG.
7. The conductive plates
110 are electrically connected through
welding with the three capacitors
7 which are arranged at a side opposite
to motor terminals Mm.
The motor terminals Mm protrude from the hole
65a in the form of
an opening formed in the cover
65 so as to be inserted into the electric
motor
30 whereby they are electrically connected with the winding terminals
37, respectively. The motor terminals Mm include three paths arranged in
parallel with each other. Motor relays
67 in the form of switches for making
or interrupting the supply of motor current IM from the bridge circuit
10
to the electric motor
30 are connected in series with two outer ones of
the three paths, respectively. These switches are connected with the paths through
welding, as shown in FIG.
1. Their welding locations are arranged at a side
diametrally or radially opposite to the electric motor
30 side at which
the switches are connected with the motor terminals Mm.
The housing side connector
68 fixedly attached to the housing
64
includes a power connector
68a electrically connected to the battery
of the vehicle, a signal connector
68b for receiving and outputting
signals from and to the vehicle side through external wiring, and a torque sensor
connector
68c for receiving a signal from the torque sensor
5.
The power connector
68a, the signal connector
68b and
the torque sensor connector
68c are formed of an insulating resin and molded
into an integral unit. Note that the torque sensor connector
68c may
not be necessarily formed integral with the signal connector
68b,
that is, they may be formed separately from each other.
The housing side connector
68 is inserted into the hole
64a
in the housing
64 from the outside, and fixedly attached to the housing
64. The housing side connector
68 is formed with a protrusion
68d.
As shown in FIG. 5, a gap or clearance is formed between the inner wall surface
of the hole
64a in the housing
64 and the side surface of
the protrusion
68d. An adhesive resin in the form of a silicon adhesive
69 is filled into the gap so that the insulating resin portions of the housing
64 and the housing side connector
68 are coupled with each other
through adhesion. The power connector
68a has terminals
68e
electrically connected with the conductive plates
110 of the large current
substrate
62 through welding.
Here, note that in the case where there is no protrusion
68d,
an adhesive resin is filled into a gap or clearance between the housing side connector
and a hole which is formed upon mounting of the housing side connector
68
to the housing
64.
The housing
64 has cooling fins
64c formed on the outer
side surface thereof. The metal substrate
61 is attached to the inner side
of the housing
64 in intimate contact therewith so that the radiation of
the heat generated by the metal substrate
61 is increased under the action
of the cooling fins
64c. The large current substrate
62 is
received in and fixedly secured to the housing
64 while covering the metal
substrate
61. In addition, the control substrate
63 is arranged to
be superposed on the large current substrate
62. As a consequence, the metal
substrate
61, the large current substrate
62 and the control substrate
63 together form a laminated structure including three layers. In contrast,
the metal substrate
61 and the housing side connector
68 are arranged
in the housing
64 in such a manner that they do not superpose one over the
other, but they are arranged in parallel to the output shaft
32.
The end portions Cm
1, Cm
2 of each of the plurality of connection
terminals Cm are arranged in the form of a letter L on the metal substrate
61.
However, one end portion Cm
1, at one side of the L-shaped configuration,
of each connection terminal Cm is arranged in the neighborhood of and in parallel
with terminals
68b1,
68c1 of the signal
connector
68b and the torque sensor connector
68c.
The one end portion Sm
2 of each sensor terminal Sm is arranged in alignment
with the other end portion Cm
2 at the other side of the L-shaped configuration
of each connection terminal Cm. The end portions Cm
1, Cm
2 of each
connection terminal Cm, the one end portion Sm
2 of each sensor terminal
Sm, the terminals
68b1 of the signal connector
68b
and the terminals
68c1 of the torque sensor connector
68c are inserted in and soldered to corresponding through holes
100,
101 formed in the control substrate
63.
A rubber ring
70 is inserted into a groove
64d formed around
the opening of the housing
64, and the cover
65 is fixedly attached
to the housing
64 by means of screws
71. As a result, airtightness
at the mating surfaces of the housing
64 and the cover
65 is secured.
At this time, the mating surfaces are located between the control substrate
63
and the metal substrate
61, as seen from FIG.
5.
As shown in FIG. 5, the cover
65 has inner cooling fins
65b
and
outer cooling fins
65c formed in such a manner that these cooling
fins
65b,
65c are arranged so as not to interpose each
other, when viewed in a diametrical or radial direction of the electric motor
30.
The inner cooling fins
65b function to perform heat transfer by natural
convection, whereas the outer cooling fins
65c function to perform
heat transfer in a state including forced convection in addition to natural convection.
For this reason, the inner cooling fins
65b have a pitch or interval
larger than that of the outer cooling fins
65c in order to expedite
smooth natural convection in the inner cooling fins
65b.
Note that in this embodiment, the cooling fins
65b,
65c
are arranged to be shifted or displaced from each other in a direction perpendicular
to the axis of the electric motor
30, but they may be formed to be shifted
or displaced from each other in the axial direction of the electric motor
30.
A lid
72 made of an insulating resin is mounted to the outer side of the
cover
65 by means of screws
73 so as to cover the hole
65a
of the cover
65. As shown in FIG. 9, the lid
72 has three penetration
holes
72g formed therein through which the motor terminals Mm electrically
connected with the armature winding
2 extend. Each of the motor terminals
Mm is formed at its intermediate portion with a low-rigidity portion Mmb of a narrow width.
Moreover, as shown in FIG. 8, the lid
72 has a plurality of penetration
holes
72f formed therein through which the end portions Sm
1
of the sensor terminals Sm electrically connected with the rotational position
sensor
3 extends, and the lid
72 also has a connector housing
72a
formed outside of the penetration holes
72f, so that the end
portions Sm
1 of the sensor terminals Sm are inserted into the penetration
holes
72f, thus constructing a sensor connector
74.
Moreover, as shown in FIG. 9, when the lid
72 is attached to the
cover
65, there are formed a gap or clearance between the outer periphery
of the lid
72 and the hole
65a and gaps or clearances around
the penetration holes
72g. However, an adhesive resin in the form
of a silicon adhesive
75 is filled into these gaps to secure the airtightness
of the mating portions of the lid
72 and the cover
65. Note that
when the motor terminals Mm are in intimate contact with the penetration holes
72g, the adhesive resin is filled into the surroundings of the those
portions of the motor terminals Mm which protrude from the lid
72.
The large current substrate
62 has a first concave portion
62a
formed in a portion thereof in which the end portions Sm
1 of the sensor
terminals Sm protrude toward the sensor connector
74, and a second concave
portion
62b formed outside of the first concave portion
62a.
The connector housing
72a has a convex portion
72b in
the neighborhood of the penetration holes
72f for the end portions
Sm
1 of the sensor terminals Sm, the convex portion
72b being
inserted into the first concave portion
62a with a gap or clearance
formed therebetween. An adhesive resin in the form of a silicon adhesive
76
is filled into the first concave portion
62a before the lid
72
is assembled. As the convex portion
72b of the connector housing
72a is inserted into the first concave portion
62a,
the silicon adhesive
76 is caused to flow out from the first concave portion
62a into the second concave portion
62b, so that the
silicon adhesive
76 is filled into the gap between the first concave portion
62a and the convex portion
72b. As a result, the airtightness
of the mating portions of the sensor terminals Sm and the lid
72 is secured.
The lid
72 is also formed with a plurality of vent holes
72c
for providing fluid communication between the interior and the exterior of
the control unit
60. A water-repellent filter
77, which permits the
passage of air but blocks the passage of water, is heat welded to the inner surface
of the lid
72 from the inside thereof so as to cover the vent holes
72c.
In addition, the vent holes
72c are formed in the convex portion
72e protruded outward from the surface of the silicon adhesive
75
which adheres or bonds the cover
65 and the lid
72 together, so as
to prevent the silicon adhesive
75 from flowing into the vent holes
72c
to close them.
Here, note that a wall
72d protruding outward from the surface
of the silicon adhesive
75 may be formed in surroundings of the vent holes
72c, as shown in FIG.
10.
Now, reference will be made to the assembling procedure of the electric power
steering apparatus as constructed above.
First of all, when the electric motor
30 is assembled, the permanent
magnet
31 is fixedly adhered to the output shaft
32 of the electric
motor
30, and then the output shaft
32 is magnetized to form eight
poles by a magnetizer. Thereafter, an inner race of a bearing
40 is press
fitted over the output shaft
32, thus forming the rotor
33.
Subsequently, the three-phase armature winding
2 is wound around
the twelve salient poles
34 of the stator
36 through the insulators
35 in such a manner that the winding components (
2u,
2v,
2w) of three phases U, V and W are shifted in their positions by
an electrical angle of 120 degrees apart from one another. In this manner, four
windings per each of U, V and W phases and hence twelve windings in total are formed.
Then, the winding starting ends and the winding terminating ends of the respective
windings of U phase are connected with each other to form the armature winding
component
2u of U phase. Similarly, the armature winding components
2v,
2w of V phase and W phase are formed. The winding
terminating ends of the armature winding components
2u-
2w
of U, V and W phases are mutually connected with each other to form neutral
points, and the winding starting ends of the armature winding components
2u-
2w
of U, V and W phases are connected with the winding terminals
37, respectively.
Thereafter, the stator
36 thus formed is press fitted into a yoke
41.
Subsequently, the outer race of the bearing
42 is fixedly secured
to the bracket
39, and then the output shaft
32 of the rotor
33
is press fitted into the inner race of the bearing
42. The rotor
3a
of the rotational position sensor
3 and the coupling
38 are press
fitted over the output shaft
32. In addition, the stator
3b of
the rotational position sensor
3 is fixedly secured to the bracket
39.
Thereafter, the yoke
41 having the stator
36 built therein is fitted
over and fixedly secured by screws (not shown) to the bracket
39 with a
rubber ring
43 mounted on an outer peripheral end thereof,
Next, reference will be made to the assembling procedure of the control unit
60.
First, parts such as the microcomputer
13, its surrounding or peripheral
circuit elements, etc., are arranged on the control substrate
63 with the
respective electrodes coated with a cream solder. Then, by heating the control
substrate
63 from its one side or by heating the entire atmosphere surrounding
the control substrate
63 by the use of a reflow device, the cream solder
is melted to solder the respective parts to the corresponding electrodes on the
control substrate
63.
Similarly, other parts such as the semiconductor switching elements Q
1-Q
6,
the shunt resistors
8, etc., are arranged on the metal substrate
61
with their electrodes coated with a cream solder, and the connection member
66
is placed on and fixedly attached to the metal substrate
61 by means of
screws
78. Then, the cream solder is melted by the use of the reflow device
to solder the respective parts and the connection member
66 to the corresponding
electrodes on the metal substrate
61.
On the large current substrate
62, there are arranged the coil
11,
the capacitors
7, the motor relays
67, etc., at prescribed positions.
These electronic parts are coupled with the conductive plates
110 and the
motor terminals Mm by means of welding. At this time, a group of the conductive
plates
110 are arranged in the vicinity of the center of the large current
substrate
62 in parallel with each other. In this manner, a group of the
motor terminals Mm are constructed such that their three paths are arranged adjacent
and in parallel with each other.
In addition, the capacitors
7 are mounted on the large current substrate
62 at a side opposite to the motor terminals Mm connected to the motor relays
67, which are also connected in series with two outer ones of the three
paths, respectively.
Thereafter, the housing side connector
68 is fitted into the hole
64a in the housing
64 from the outside thereof and fixedly
secured to the housing
64 by means of screws
79. At this time, the
silicon adhesive
69 is filled in the gap between inner wall surface of the
hole
64a in the housing
64 and the protrusion
68d
of the housing side connector
68, and hence the insulating resin portions
of the housing
64 and the housing side connector
68 are adhered or
bonded to each other through the silicon adhesive
69.
Subsequently, the metal substrate
61 is placed on the housing
64 from the opening side thereof and fixedly attached thereto by screws
80. Then, the large current substrate
62 is arranged on and fixedly
secured through screws
81 to the metal substrate
61. At this time,
the metal substrate
61 is fixed to the housing
64 by means of the
screws
80,
81 which are arranged at four corners of the housing
64.
As a result, the metal substrate
61 is urged into intimate contact with
the housing
64. Thereafter, the terminals
68e of the power
connector
68a are electrically connected with the conductive plates
110 on the large current substrate
62 by means of welding. In addition,
the conductive plates
110 and the motor terminals Mm on the large current
substrate
62 are electrically connected with the connection terminals Cm,
respectively, of the connection member
66 on the metal substrate
61
by means of welding.
Thereafter, the control substrate
63 is arranged at an upper portion
of the large current substrate
62, and the connection terminals Cm, the
terminals
68b1 of the signal connector
68b,
the terminals
68c1 of the torque sensor connector
68c,
the sensor terminals Sm of the large current substrate
62, etc., are inserted
into the through holes
100,
101 in the control substrate
63
and connected with each other collectively by means of soldering with partial jet streams.
At this time, the terminals inserted into the through holes
100,
101
of the control substrate
63 are each arranged in the form of a letter L.
One end portion Cm
1, at one side of the L-shaped configuration, of each
of the plurality of connection terminals Cm is arranged in the neighborhood of
and in parallel to the terminals
68b1 of the signal connector
68b and the terminals
68c1 of the torque sensor
connector
68c. Further, the end portions of the terminals inserted
into the through holes
100,
101 of the control substrate
63
are concentrated on two sides of the control substrate
63, and the mating
surfaces of the housing
64 and the cover
65 are located between the
control substrate
63 and the metal substrate
61 in a diametral or
radial direction of the output shaft
32.
Subsequently, the rubber ring
70 is inserted into the groove
64d formed on the outer periphery of the opening in the housing
64,
and the cover
65 is fixedly secured to the housing
64 by means of
the screws
71 with the silicon adhesive
76 being filled into the
first concave portion
62a of the large current substrate
62.
At this time, airtightness at the mating surfaces of the housing
64 and
the cover
65 is secured. Then, the water-repellent filter
77 is heat
welded to the inner surface of the lid
72 so as to cover the vent holes
72c formed therethrough, and one end portions Sm
1 of the sensor
terminals Sm are inserted into the penetration holes
72f in the lid
72. After the motor terminals Mm are inserted into the penetration holes
72g, the lid
72 is fixedly attached to the cover
65
by means of the screws
73. At this time, the silicon adhesive
76
is forced to flow out from the first concave portion
62a to the second
concave portion
62b in accordance with the insertion of the convex
portion
72b of the lid
72 into the first concave portion
62a,
whereby the silicon adhesive
76 is filled into the gap between the first
concave portion
62a and the convex portion
72b.
Furthermore, since the connector housing
72a is formed
on the outer periphery of the penetration holes
72f through which
the end portions Sm
1 of the sensor terminals Sm extend, the sensor terminals
Sm are inserted into the penetration holes
72f to form the sensor
connector
74.
Moreover, by attaching the lid
72 to the cover
65, there
are formed gaps or clearances around the penetration holes
72g and
between the outer periphery of the lid
72 and the hole
65a,
but an adhesive resin in the form of the silicon adhesive
75 is filled into
these gaps or clearances.
At this time, the vent holes
72c are formed in the convex portion
72e which protrudes outward from the surface of the silicon adhesive
75 bonding the cover
65 and the lid
72 with each other, so
that the silicon adhesive
75 is prevented from flowing into the vent holes
72c to close or block them.
Then, the electric motor
30 and the control unit
60 thus separately
built are assembled with each other. As shown in FIG. 3, the rubber ring
82
is fitted on the bracket
39 of the electric motor
30, and the control
unit
60 is fixedly secured to the bracket
39 by means of screws
83,
whereupon the connector
74a on the electric motor
30 side
and the connector
74 on the control unit
60 of the rotational position
sensor
3 are placed in fitting engagement with each other to provide electrical
connection therebetween.
Thereafter, the winding terminals
37 of the electric motor
30
and the motor terminals Mm of the control unit
60 are fixedly coupled with
each other by screws
84, and electrically connected with each other. At
this time, even if there are generated gaps or clearances in the axial direction
of the output shaft
32 between the winding terminals
37 and the motor
