Title: Direct drive windshield wiper assembly
Abstract: A direct drive windshield wiper assembly including at least one brushless DC motor providing a drive torque through an output that is rotatable about the longitudinal axis of the motor and a windshield wiper that is driven by the motor about the longitudinal axis in a repeated wiping motion across the surface of a windshield. The motor including a planetary gear set having an output shaft, the gear set being coaxially disposed relative to the rotational output and the longitudinal axis of the motor and operatively interconnecting the drive torque and the windshield wiper, the gear set further operable to reduce the speed of the rotational output of the motor to the windshield wiper through the output shaft of the gear set.
Patent Number: 6,944,906 Issued on 09/20/2005 to Moein, et al.
| Inventors:
|
Moein; Arman (Grand Blane, MI);
Peck; David Emery (Rochester Hills, MI)
|
| Assignee:
|
TRICO Products Corporation (Rochester Hills, MI)
|
| Appl. No.:
|
146190 |
| Filed:
|
May 15, 2002 |
| Current U.S. Class: |
15/250.3; 310/66; 310/68R; 310/83; 318/443; 318/444; 318/DIG.2 |
| Intern'l Class: |
B60S 001/08 |
| Field of Search: |
15/2503,250.001,250.12,250.16,250.17
318/DIG.2,443,444
310/83,89,66,77,67.R,272,273,68.B,68.R
|
References Cited [Referenced By]
U.S. Patent Documents
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| 4021714 | May., 1977 | Jones et al.
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| 4072884 | Feb., 1978 | Treadwell.
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| 4095158 | Jun., 1978 | Matsumoto.
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| 4099104 | Jul., 1978 | Muller.
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| 4115715 | Sep., 1978 | Muller.
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| 4125792 | Nov., 1978 | Schmider.
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| 4194184 | Mar., 1980 | Hartmann et al.
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| 4259603 | Mar., 1981 | Uchiyama et al.
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| 4264850 | Apr., 1981 | Cannon et al.
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| 4310790 | Jan., 1982 | Mulet-Marquis.
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| 4529922 | Jul., 1985 | Ono.
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| 4546299 | Oct., 1985 | Veale.
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| 4585980 | Apr., 1986 | Gille et al.
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| 4623831 | Nov., 1986 | Sakamoto et al.
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| 4647827 | Mar., 1987 | Toyoda et al.
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| 4665488 | May., 1987 | Graham et al.
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| 4818907 | Apr., 1989 | Shirotori.
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| 4847527 | Jul., 1989 | Dohogne.
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| 4900995 | Feb., 1990 | Wainwright.
| |
| 4952830 | Aug., 1990 | Shirakawa.
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| 4962331 | Oct., 1990 | Smith.
| |
| 5072179 | Dec., 1991 | Miller et al.
| |
| 5252897 | Oct., 1993 | Porter et al.
| |
| 5355061 | Oct., 1994 | Forhan.
| |
| 5588173 | Dec., 1996 | Battlogg.
| |
| 5747910 | May., 1998 | Haner.
| |
| 6037735 | Mar., 2000 | Janosky et al.
| |
| 6255751 | Jul., 2001 | Hoffmann.
| |
| 6281649 | Aug., 2001 | Ouellette et al.
| |
| 6700279 | Mar., 2004 | Uchiyama et al.
| |
Primary Examiner: Graham; Gary K.
Attorney, Agent or Firm: Bliss McGlynn, P.C.
Claims
1. A direct drive windshield wiper assembly comprising:
at least one brushless DC motor providing a drive torque through an output that
is rotatable about the longitudinal axis of said motor and a windshield wiper that
is driven by said motor about said longitudinal axis in a repeated wiping motion
across the surface of a windshield;
said motor including a motor housing, a gear set housing operatively supported
on one end of said motor housing and an electronics housing operatively supported
on said motor housing opposite said gear set housing, said gear set housing encompassing
a planetary gear set;
said planetary said gear set being coaxially disposed relative to said rotational
output and said longitudinal axis of said motor and operatively interconnecting
said drive torque and said windshield wiper, said planetary gear set further operable
to reduce the speed of the rotational output of said motor to said windshield wiper
through said output shaft of said gear set;
a position sensor disposed within said electronics housing that is adapted to
sense the speed and position of said output shaft of said gear set, said position
sensor includes a flux ring holder that is adapted to support at least one flux
ring thereupon, said position sensor further includes a magnet holder operatively
connected to said output shaft of said a gear set and adapted for rotation therewith,
said magnet holder supporting at least one magnet in spaced parallel relationship
with respect to said flux ring; and
a position sensor circuit adapted for producing signals as to the rotational
speed and position of said output shaft of said planetary gear set.
2. A direct drive windshield wiper assembly as set forth in claim 1 wherein said
motor housing, gear set housing, and electronics housing are formed by an injection
molding process.
3. A direct drive windshield wiper assembly as set forth in claim 2 wherein said
motor housing of said DC brushless motor includes a stator fixedly supported within
said motor housing, a rotor rotatably supported within said motor housing and disposed
about said stationary stator, said rotor operatively connected to said output shaft
of said gear set and controllable to rotate in either direction thereby providing
bi-directional rotation to said output shaft of said gear set.
4. A direct drive windshield wiper assembly as set forth in claim 3 wherein brushless
DC motor includes a latching mechanism for securing said rotor and thus said output
shaft of said gear set in non-rotational disposition when said motor is off.
5. A direct drive windshield wiper assembly as set forth in claim 4 wherein said
rotor includes a plurality of notches, said latching mechanism including an electromagnetic
actuator, a latching member, and a biasing member, said latching member subject
to a biasing force to engage at least one of said notches formed on said rotor
to immobilize same and subject to an electromagnetic force generated by said actuator
to overcome said biasing force to allow rotation of said rotor.
6. A direct drive windshield wiper assembly as set forth in claim 5 wherein said
plurality of notches are defined on at least one end of said rotor and spaced from
said latching mechanism when said electromagnetic device is actuated.
7. A direct drive windshield wiper assembly as set forth in claim 3 wherein said
stator is of a stamped lamination construction being conventionally wound, and
having an end plate that is adapted to retain the ends of the windings while offering
a plurality of quick mounting points for connection to said electronics housing.
8. A direct drive windshield wiper assembly as set forth in claim 1 wherein said
coaxial planetary gear set is disposed within said gear set housing and includes
a sun gear, a ring gear, a carrier, and a plurality of planet gears operatively
supported by said carrier, said planet gears disposed in meshing relationship with
said sun gear and said ring gear and operable to reduce the speed of the rotational
output of said brushless DC motor.
9. A direct drive windshield wiper assembly as set forth in claim 8 wherein said
sun gear is operatively driven by the rotational output of said DC motor, said
carrier is operatively connected to said output shaft of said gear set and said
ring gear is fixedly mounted to said gear set housing in a fixed position relative
to said planet gears such that rotation of said sun gear causes said planet gears
to revolve around said ring gear thereby rotating said carrier and said output
shaft of said gear set about said longitudinal axis of said motor.
10. A direct drive windshield wiper assembly comprising:
at least one motor providing a drive torque through an output and a windshield
wiper that is driven by said motor in a repeated wiping motion across the surface
of a windshield;
said motor further including a position sensor that is adapted to sense the speed
and position of said output, said position sensor including a flux ring holder
fixedly mounted within said motor and adapted to support at least one flux ring
thereupon, a magnet holder operatively connected to said output of said motor and
adapted for rotation therewith, said magnet holder supporting at least one magnet
in spaced parallel relationship with respect to said flux ring, and a position
sensor circuit adapted for producing signals in response to said position sensor
as to the rotational speed and position of said windshield wiper.
11. A direct drive windshield wiper assembly as set forth in claim 10 wherein
said motor includes a gear set having an output shaft that interconnects said drive
torque to said windshield wiper and is adapted to reduce the speed of the rotational
output of said motor to said windshield wiper through said output shaft of said
gear set.
12. A direct drive windshield wiper assembly as set forth in claim 11 wherein
said at least one magnet is disposed within said magnet holder in a manner having
a predetermined angular orientation with respect to said at least one parallel
spaced flux ring, such that the magnetic field emanating from said at least one
magnet presents a specific magnetic flux signal to said at least one flux ring
that is representative of a particular angular displacement of said output shaft
thereby allowing said position sensor to act as an absolute position sensor for
detecting the angular position of said output shaft.
13. A direct drive windshield wiper assembly as set forth in claim 10 wherein
said motor is at least one of a type of motor from a group comprising a brushless
DC motor, a switched reluctance motor, or an induction motor.
14. A direct drive windshield wiper assembly comprising:
at least one brushless DC motor providing a drive torque through an output and
a windshield wiper that is driven by said motor in a repeated wiping motion across
the surface of a windshield;
said motor further including a housing and a stator fixedly supported within
said housing, a rotor rotatably supported within said housing and disposed about
said stationary stator, said rotor includes a plurality of notches and is operatively
connected to said output of said motor and controllable to rotate in either direction
thereby providing bi-directional rotation to said windshield wiper; and
a latching mechanism adapted for securing said rotor and thus said output of
said motor in non-rotational disposition when said motor is off, said latching
mechanism including an electromagnetic actuator and a latching member and a biasing
member, said latching member subject to said biasing member to engage at least
one of said notches formed on said rotor to immobilize same and subject to an electromagnetic
force to activate said actuator thereby disengaging said rotor.
15. A direct drive windshield wiper assembly as set forth in claim 14 wherein
said plurality of notches are defined on at least one end of said rotor and spaced
from said latching mechanism when said electromagnetic device is not actuated.
16. A direct drive windshield wiper assembly comprising:
at least one brushless DC motor providing a drive torque through an output that
is rotatable about the longitudinal axis of said motor and a windshield wiper that
is driven by said motor in a repeated wiping motion across the surface of a windshield;
said motor including a gear set having an output shaft, said gear set being coaxially
disposed relative to said rotational output and longitudinal axis of said motor
and operatively interconnecting said drive torque and said windshield wiper, said
gear set further operable to reduce the speed of the rotational output of said
motor to said windshield wiper through said output shaft of said gear set; and
said motor further including a programmable control circuit that is operatively
supported within an electronic housing and includes a motor driver, a current sensor,
a voltage regulator, a solenoid driver, a microprocessor and at least one serial
communications interface, said interface having a Local Interconnected Network
(LIN) physical layer, said programmable control circuit acting to control the operation
of said brushless DC motor so as to effect the position and speed of said windshield
wiper.
17. A direct drive windshield wiper assembly as set forth in claim 16 wherein
said microprocessor includes a memory that is programmable to retain at least one
predetermined windshield wiper control scheme.
18. A direct drive windshield wiper assembly as set forth in claim 17 wherein
said serial communications interface is in electrical communication with the serial
communications interface of at least one other direct drive windshield wiper assembly
such that said microprocessor of said windshield wiper assembly interfaces with
the microprocessor of said at least one other windshield wiper assembly thereby
allowing said microprocessors to coordinate said at least one predetermined windshield
wiper control scheme.
19. A direct drive windshield wiper assembly as set forth in claim 16 wherein
said solenoid driver is in electrical communication with a latching solenoid disposed
within said motor, said solenoid driver operable to control said latching solenoid
such that said motor is free to rotate when said solenoid driver causes said latching
solenoid to activate.
20. A direct drive windshield wiper assembly as set forth in claim 16 wherein
said programmable control circuit and said brushless DC motor are adapted to be
operable in a 42 volt operating environment.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to windshield wiper systems and, more
particularly, to a windshield wiper system that utilizes individual direct drive
motors for coordinated, but mechanically independent, control of the windshield wipers.
2. Description of the Related Art
Windshield wiper systems commonly employed in the related art include
pivotally mounted wiper blades that are oscillated across a windshield between
an in-wipe position, typically located near the cowl of an automotive vehicle,
and an out-wipe position, usually associated with an A-pillar on the vehicle, in
the case of the driver side wiper blade in this representative example. It is typically
desirable to maximize the angular velocity of the blade assemblies between the
in-wipe and out-wipe positions where the blade assembly is moving across the windshield
in front of the driver to reduce the duration of each wipe cycle. On the other
hand, it is also desirable to limit noise and inertia loading by reducing the velocity
of the blade assemblies as they approach the wipe limits. These are two competing
objectives that must be balanced in order to be successfully and economically obtained.
One long-standing design approach that has been employed in the related art includes
the use of a single motor assembly, driven in one rotational direction, driving
two separate wiper arms across the windshield of a vehicle. This approach requires
a fairly complex linkage system to convert the singular angular motion of the wiper
motor into the two-way linear reciprocal motion to drive both wiper arms. In the
dashboard-firewall area, where these systems are typically installed, this mechanical
linkage required a large amount of underhood space. Moreover, the area near this
moving linkage must be kept clear of wires and other vehicle components. Additionally,
the moving linkage, with its several pivot and rotational points is subject to
mechanical inaccuracies and wear, readily introducing excessive wiper movement.
Nevertheless, for many years, designers and manufacturers were reluctant
to depart from this established approach. However, improved vehicle aerodynamics
that have fostered vehicle designs having longer sloped front surfaces are leading
to windshield designs with more pronounced rake angles that result in larger window
surfaces. A wiper system for such windshields must therefore include longer, more
massive wiper arms and blades to wipe the required percentage of the larger surface.
This has created a number of problems. Most notably, the larger arms and swept
surface area increases the size of conventional wiper systems to such an extent
that it becomes difficult to fit a single motor system within the typically allotted
underhood space. This problem is further aggravated by the same aerodynamic sloped
front surfaces of the newer vehicle designs, which reduce the available underhood
space. Additionally, the larger area to be swept by the wiper system requires more
power and control over the wiper arm that can be provided by a linkage type system.
In response to the changes in vehicle front face design and the loss of available
underhood space, the dual motor wiper system has evolved. Representative examples
of such systems can be found in U.S. Pat. No. 4,585,980 to Gille et al., U.S. Pat.
No. 4,665,488 to Graham et al., U.S. Pat. No. 4,900,995 to Wainwright, and U.S.
Pat. No. 5,252,897 to Porter et al. These wiper systems are generally directly
driven. Additionally, U.S. Pat. No. 5,355,061 to Forham employs a brushless dc
motor to operate a direct drive windshield wiper system, as do others that follow.
The more recent direct drive wiper blade systems employing dual motors have utilized
some hardware and/or software controlled switching scheme to control each individual
motor, in reference to the other, to provide blade control across the windshield
and prevent blade-to-blade contact.
The conventional control approach relies upon intricate software control and
position sensing along the wipe pattern. This undesirably requires separate motor
control circuitry and a reliance on the movement of the wiper motors to provide
positional feedback. Generally, motor position feedback has been used in brushless
dc motors by sensing the changes in the commutation of the motor windings. This
has sometimes been done using Hall Effect sensors, as disclosed, for example, in
U.S. Pat. No. 4,680,515 to Crook, U.S. Pat. No. 4,723,100 to Horikawa et al., and
U.S. Pat. No. 4,897,583 to Rees. The Hall Effect sensors have also been used to
count pulses of a pulse train generated by a rotating toothed wheel to produce
position signals for operational control of the motor. While suitable for use in
windshield wiper systems, the use of the above-noted brushless dc motor controllers
in a windshield wiper system that uses separate position sensors for coordination
of the wipers can result in an unnecessarily complicated design. Also, any loss
of power to the system will disorient and confuse these sensors such that the wiper
arm position becomes an unknown. Thus, windshield wiper systems that employ pulse
train type sensors suffer from the disadvantage that they easily loose the accurate
position of the windshield wiper blade during common operating conditions and therefore
suffer a loss of control in these circumstances.
The build-up of snow and ice on the windshield complicates the control of blade
movement and the ability to accurately determine wiper arm position and can impede
the movement of the blades unevenly, causing one blade to move faster than the
other. When encountering this problem, electronically controlled wiper systems
presently known in the art can often become unsynchronized and may clash as they
become unable to maintain their sense of wiper arm position. Thus, there is a need
in the art for a direct drive motor for a windshield wiper system that has integrated
control circuitry and achieves position sensing such that the wiper arms position
is known regardless of rotation and such that the detected arm position is not
lost during power loss or loss of motion.
Conventional dual direct drive wiper systems use high-speed dc motors.
This is undesirable, as it requires large counter-rotational forces to stop and
then reverse the wiper arm at the end of its sweep. Also, large current draws are
necessary to produce the counter-rotational forces which causes repetitive surges
in the supplied power and induces great amounts of electromagnetic interference
to the immediately surrounding parts of the vehicle. With a high-speed dc motor,
it is also problematic to vary the speed of the wiper arm as it sweeps across the
windshield, if this is desired as part of a sweeping pattern or predetermined clearing
scheme. These drawbacks stem from the conventional construction of direct drive
wiper motors, which have either a one-to-one direct drive or an inefficient gearing
assembly to differ the wiper arm speed from motor speed. Thus, there is also a
need in the art for a direct drive motor for a windshield wiper system that is
efficient and controllable at a lower drive speed and that is electro-magnetically clean.
One other drawback to conventional wiper motor systems has recently emerged.
The conventional direct drive windshield wiper systems employ dc motors that are
of the standard 12-volt operating standard. This is presently adequate, but current
design trends are moving toward more efficient 42 volt based automotive electrical
systems. The change over to a 42 volt automotive electrical systems will be highly
problematic for the prior dual direct drive wiper systems and presents a considerable
drawback as the prior systems are not compatible. Therefore, there is a need to
not only provide a direct drive windshield wiper system that overcomes the above-mentioned
drawbacks but that also has the ability to be employed in the newly emerging 42
volt automotive electrical system environment.
SUMMARY OF THE INVENTION AND ADVANTAGES
Each of the disadvantages that presently exist in the related art as discussed
above is overcome in the direct drive windshield wiper assembly of the present
invention. This direct drive windshield wiper assembly includes at least one brushless
DC motor providing a drive torque through an output that is rotatable about the
longitudinal axis of the motor and a windshield wiper that is driven by the motor
about the longitudinal axis in a repeated wiping motion across the surface of a
windshield. The motor includes a planetary gear set having an output shaft. The
gear set is coaxially disposed relative to the rotational output and the longitudinal
axis of the motor and operatively interconnects the drive torque and the windshield
wiper. The gear set is further operable to reduce the speed of the rotational output
of the motor to the windshield wiper through the output shaft of the gear set.
The direct drive windshield wiper assembly according to the present invention
may also include a position sensor that is adapted to sense the speed and position
of the motor output. The position sensor includes a flux ring holder that is fixedly
mounted within the motor and is adapted to support at least one flux ring thereupon.
A magnet holder is operatively connected to the output of the motor and is adapted
for rotation therewith. The magnet holder supports at least one magnet in spaced
parallel relationship with respect to the flux ring. In addition, the motor includes
a position sensor circuit that produces signals corresponding to the rotational
speed and position of the windshield wiper.
In another alternate embodiment, the direct drive windshield wiper assembly of
the present invention includes at least one brushless DC motor that provides a
drive torque through an output and a windshield wiper that is driven by the motor
in a repeated wiping motion across the surface of the windshield. The motor includes
a housing and a stator fixedly supported within the housing. A rotor is rotatably
supported within the housing and is disposed about the stationary stator. The rotor
is operatively connected to the output of the motor and controllable to rotate
in either direction thereby providing bi-directional rotation to the windshield
wiper. In addition, the direct drive windshield wiper assembly further includes
a latching mechanism that acts to secure the rotor and thus the output of the motor
in a non-rotational disposition when the motor is off.
In still another embodiment of the direct drive windshield wiper assembly of
the
present invention the motor may further include a programmable control circuit
that acts to control the operation of the motor so as to affect the position and
speed of the windshield wiper.
One advantage of the windshield wiper system of the present invention is that
it utilizes individual direct drive motors for coordinated, but mechanically independent
control of the windshield wiper. The present invention acts to maximize the angular
velocity of the blade assemblies between in-wipe and out-wipe positions thereby
reducing the duration of each wipe cycle while limiting the noise and inertia loading
by efficiently structuring a brushless DC motor and by controlling the velocity
of the blade assemblies as they approach the wipe limits when the direction of
the wiper assembly must be reversed.
Another advantage of the windshield wiper system of the present invention
is that the sweep speed and velocity of the wiper assembly within the wipe cycle
may be controlled to reduce the time the wiper assembly spends in the driver's
view area of the windshield thereby reducing the visual obstruction of the wiper assembly.
Another advantage of the windshield wiper system of the present invention
is that it eliminates the complex linkages employed in the related art to convert
single angular motion of the wipe motor into two-way linear reciprocal motion used
to drive one or more windshield wiper arms. Thus, the present invention requires
a smaller operational envelope than devices employed in the related art.
Another advantage of the present invention is that it employs a position
sensor that senses the rotational speed and position of the windshield wiper and
will not loose its position parameter even in the event of a power loss. Thus,
the windshield wiper system of the present invention will not become unsynchronized
and therefore will not clash due to an inability to maintain the sense of wiper
arm position.
Another advantage of the present invention is that it employs a latching
mechanism that secures the motor and thus the output of the motor in a non-rotational
disposition when the motor is off.
Another advantage of the present invention is that it includes an integrated
control circuitry that achieves position sensing such that the wiper arm position
is known regardless of rotation and such that the detected arm position is not
lost during power loss or loss of motion.
Still another advantage of the windshield wiper system of the present invention
is that it may be employed in either a standard 12 volt or the more efficient 42
volt-based automotive electrical system.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the invention will be readily appreciated as the same becomes
better understood by reference to the following detailed description when considered
in connection with the accompanying drawings, wherein:
FIG. 1 is an assembled view of the preferred embodiment of the present invention
of a direct drive windshield wiper assembly;
FIG. 2 is an exploded view of the assemblies of the preferred embodiment of
the present invention;
FIG. 3 is a cross-sectional view of the assemblies of the preferred embodiment
of the present invention and their physical relationship to each other;
FIG. 4 is an exploded view of the motor housing assembly of the preferred embodiment
of the present invention;
FIG. 5 is an exploded view of the rotor assembly of the preferred embodiment
of the present invention;
FIG. 6 is an exploded view of the gear housing assembly of the preferred embodiment
of the present invention;
FIG. 7 is an exploded view of the electronics housing of the preferred embodiment
of the present invention;
FIG. 7A is an exploded detail view of the position sensor assembly of the electronics
housing in the preferred embodiment of the present invention;
FIG. 8 is a block diagram of the programmable control circuit of the preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring now to the figures where like numerals are used to designate
like structure throughout the drawings, a direct drive windshield wiper assembly
of the present invention is generally indicated at
10. As shown in FIG.
1, the direct drive windshield wiper assembly
10 includes at least one motor
12 that rotatably drives a windshield wiper
14 across the surface
of a windshield
16. Generally speaking, the motor
12 provides a drive
torque through an output that is rotatable about the longitudinal axis of the motor
12 so that the windshield wiper
14 is driven about the same longitudinal
axis in a repeated wiping motion across the surface of the windshield
16.
The motor
12 further controllable to rotate in either direction, thereby
providing bi-directional rotation to the windshield wiper
14. In addition,
from the description that follows, those having ordinary skill in the art will
appreciate that the windshield wiper assembly of the present invention may encompass
two or more motors
12, each that drive a windshield wiper
14 in repeated
wiping motion across the surface of a windshield
16. It should also be appreciated
that the motor
12 may be of a brushless DC, a switched reluctance, or an
induction type motor without departing from the spirit and scope of the invention.
However, for purposes of description and not by way of limitation, it will be described
generally as a brushless DC motor in this specification. In the preferred embodiment,
each motor
12 is electronically interconnected and controlled in a manner
that will be described in greater detail below.
Specifically, as best shown in FIG. 2, the motor
12 includes
a motor assembly, generally indicated at
20, a gear set assembly, generally
indicated at
22, operatively supported on one end of the motor assembly
20 and an electronics assembly, generally indicated at
24, operatively
supported on the motor assembly
20 opposite the gear set assembly
22.
In the preferred embodiment, the gear set assembly
22, and the electronics
assembly
24 are made of a plastic material composition formed by an injection
molding process for ease of construction, weight, strength, and environmental considerations.
The motor assembly
20 is made of a magnesium alloy to remove heat and dampen
electromagnetic interference and may be formed by an injection molding process.
It should be appreciated by those of ordinary skill in the art that any of a variety
of materials may be successfully employed in the manufacture of these parts.
As shown in FIGS. 3 and 4, the motor assembly
20 includes a housing
21
that is formed in a general cup shape and encloses a stator
26 that is fixedly
supported within an inner cavity
28 of the motor housing
21, and
a rotor assembly
30 that is rotatably supported within the motor housing
21 and disposed about the stationary stator
26. The stator
26
is formed in the shape of an annular ring having an open center and is disposed
over a hollow cylindrical center hub
32 within the motor housing
20.
The stator
26 is constructed in a known manner having either a plurality
of stamped lamination pieces
34 stacked together or being of a one-piece
molded powder metal. The stator
26 is conventionally wire wound and has
an end plate
36 that is adapted to readily retain the ends of the wire windings
while offering a plurality of connector points
38 for connection to the
electronics assembly
24. The connector points
38 of the stator end
plate
36 are accessible through openings
40 in the base of the motor
housing
21. The center hub
32 of the motor housing
21 also
has a bearing recess
50 (FIG. 4) that receives and retains the rotor bearing
52 (FIG.
3). The rotor bearing
52 serves to rotatively support
the rotor assembly
30 as described below.
As shown in FIGS. 3 and 5, the rotor assembly
30 includes a back iron
60,
a motor magnet
62 that is operatively supported by the back iron
60
and a rotor cap
64. A sun gear
66 is operatively mounted to the rotor
cap
64 as will be described in greater detail below. The back iron
60
is generally shaped as a sleeve having an inner circumference
68 upon which
the motor magnet
62 is molded. Alternately, the motor magnet
62 may
be glued and pressed into the back iron
60. Thus the back iron
60
provides rigid support for the motor magnet
62. In the preferred embodiment,
a molded permanent magnet of a composition of Nb—Fe—B (Niobium, Iron,
and Boron) is desirable for its strength and durability. The Nb—Fe—B
compound is also easy to mass produce and produces tight, short magnetic flux lines,
which generate a magnetic field that is stronger than other moldable magnetic compounds
allowing the magnet to be smaller and lighter. However, it will be appreciated
by those having ordinary skill in the art that any of a variety of magnetic compounds
may be used or that non-molded magnets may also be employed without departing from
the spirit and scope of the present invention.
The disk-shaped rotor cap
64 is fixedly mounted to the upper edge
72
of the rotor back iron
60, so that the rotor assembly
30 forms a
cup-shape that is received by the motor housing
21. The rotor cap
64
has a central opening
74 and a bearing surface
76. The bearing surface
76 is disposed on the inner side of the rotor cap
64 and is received
by and engaged to the rotor bearing
52 that is disposed within the center
hub
32 within the motor housing
21. The central opening
74
of the rotor cap
64 is splined at
78 and adapted to complementarily
receive in splined engagement the gear teeth
80 of a sun gear
66.
Alternately, the sun gear
66 may be operatively interconnected to the rotor
cap
64 using any other suitable means commonly known in the art. The sun
gear
66 also has a central opening
82 and may include a truncated
conical head
84 at one end.
As shown in FIGS. 3 and 6, the gear assembly
22 includes a gear housing
23 that is formed in a general cup shape and includes a planetary gear set,
generally indicated at
86. The gear set
86 is coaxially disposed
relative to the rotational output of the rotor assembly
30 and is thus coaxial
to the longitudinal axis of the motor
12 and operatively interconnects the
motor drive torque and the windshield wiper
14. The gear set
86 is
further operable to reduce the speed of the rotational output of the motor
12
to the windshield wiper
14 through the output shaft
88 of the gear
set
86.
In the preferred embodiment illustrated in these figures, the gear set
86
includes an output shaft
88, a ring gear
90, a carrier
92,
and a plurality of planet gears
94 operatively supported by the carrier
92. The planet gears
94 are supported within a two-piece carrier
92 in meshing relationship with the ring gear
90 of the planetary
gear set
86 and the sun gear
66 of the rotor assembly
30.
The ring gear
90 is fixedly disposed within the inner circumference
96
of the gear housing
22. The output shaft
88 has a wiper end
98
and a sensor end
100. The sensor end
100 defines a predetermined
diameter that can be narrower than the wiper end
98.
The wiper end
98 of the output shaft
88 extends outward through
a central opening
102 of the gear housing
23. The exposed portion
104 of the wiper end
98 is machined in a manner to receive and retain
the end of a windshield wiper
14. It should be appreciated by those of ordinary
skill in the art that the exposed portion of the wiper end
98 of the output
shaft
88 may be splined or otherwise keyed to rotationally secure the wiper
14. However, as will be discussed in greater detail below, there is no necessity
for orienting the wiper
14 to a particular angular position of the output
shaft
88 as the "park", and lower and upper sweep limits of the wiper
14
are programmable and software calibrated on the vehicle once the direct drive windshield
wiper assembly
10 is installed.
As best shown in FIG. 3, the output shaft
88 also has a carrier interface
portion
106 adjacent to the exposed portion
104. The carrier interface
portion
106 is received by, and operatively connected to, a hollow center
sleeve
108 of the carrier
92. It should be appreciated that the carrier
92 may be connected to the output shaft
88 by splines, a keyway,
or any of a variety of connection methods. Thus, the central opening
102
of the gear housing
23 has an inner diameter sufficient to receive the combined
carrier center sleeve
108 and the output shaft
88. As can be seen
in FIGS. 3 and 6, a spring
110 and a spring washer
112 are of an
inside and outside diameter that allows them to be received by the gear housing
central opening
102 while being disposed over the output shaft wiper end
98 above the carrier center sleeve
108. A push nut
114 and
push nut washer
116 are disposed over the wiper end
98 of the output
shaft
88, such that the push nut washer
116 rotatively rides on the
outer end surface
118 of the gear housing central opening
102 while
causing a compressive biasing force to be placed on the spring
110 and spring
washer
112 within the gear housing central opening
102 against the
end of the carrier center sleeve
108. The push nut
114 serves to
lockingly engage the output shaft
88 and hold the push nut washer
116,
the spring
110, and the spring washer
112 in place without the need
of threads. The compressive, or biasing force, imparted by the spring
110
serves to maintain the longitudinal alignment of the components of planetary gear
set
86 with the rotor assembly
30 and the stator
26, as the
carrier
92 is supportively biased against the truncated conical lip
84
of the sun gear
66. Also, the biasing force of the spring
110 bears
against the lip
84 so that the planet gears
94 maintain their alignment
against the sun gear
66, as seen in FIG.
3.
The sun gear
66 is operatively driven by the rotational output of the
brushless DC motor
12 by its direct connection to the rotor cap
64
of the rotor assembly
30. The carrier
92 is operatively connected
to the output shaft
88, the ring gear
90 is fixedly mounted to the
gear set housing
23 in a fixed position. Thus, in operation, rotation of
the sun gear
66 causes the planet gears
94 to revolve around the
ring gear
66 thereby rotating the carrier
92 and the output shaft
88 of said gear set about the longitudinal axis of the motor. The rotor
assembly
30, gear set
86, and output shaft
88 within the motor
12, are all in coaxial relationship to each other.
The motor housing
21 further includes a recess
42 that is designed
to accommodate a portion of a latching mechanism, generally indicated at
44.
The back iron
60 of the rotor assembly
30 includes a plurality of
notches
70 disposed about its lower edge. The latching mechanism
44
acts to secure the rotor assembly
30 and thus the output shaft
88
of the gear set
86 in non-rotational disposition when the motor
12
is off. More specifically, the latching mechanism
44 includes an electromagnetic
actuator
45 and a latching member
46. In the preferred embodiment,
the electromagnetic actuator is a solenoid
45 that operatively drives the
latching member
46 to a retracted position. In addition, the latching mechanism
44 includes a biasing member
48 that produces a biasing force in
a direction opposite of that produced by the solenoid
45 such that the latching
member
46 engages at least one of the notches
70 formed on the back
iron
60 of the rotor assembly
30 thereby immobilizing it. On the
other hand, the electromagnetic force generated by the solenoid
45 is sufficient
to overcome the biasing force to allow rotation of the rotor which allows the latching
member
46 of the latching solenoid
44 to disengage from the notch
70 and thereby releasing the back iron
60 allowing it to rotate.
In the preferred embodiment, the biasing member
48 is a coiled spring that
normally biases the latching member
46 to the engaged position securing
the rotor assembly
30 and thus, the output shaft
88 in non-rotational
disposition when the motor
12 is off.
The gear housing
23 further includes a plurality of recessed bores
120
formed in the outer surface that receive and retain a like number of threaded inserts
122. The treaded inserts
122 provide mounting points for the direct
drive windshield wiper assembly
10 to locate and secure the assembly within
the vehicle. Alternately, the direct drive windshield wiper assembly
10
may be mounted using a flange mount disposed upon the gear housing
23 or
any other suitable mounting method commonly known in the art. A rubber boot
124
is sealingly disposed over the output shaft wiper end
98 and the gear housing
central opening
102 in a manner that prevents environmental elements from
entering the motor assembly
12 but allows the output shaft
88 to
freely rotate as necessary.
As best seen in FIG. 3, the output shaft
88 is received through a central
opening in the sun gear
66 and through the center opening of the bearing
assembly
52, and extends inward into the hollow center hub
32 of
the motor housing
21. The output shaft
88 is not physically connected
to either the sun gear
66 or the rotor bearing
52 but is free to
rotate within them. In this manner, the sensor end
100 of the output shaft
88 is operatively connected to a position sensor as discussed below.
As illustrated in FIG. 7, the electronics assembly
24 of the motor
12
includes a position sensor assembly
126, an end cap
128, and a programmable
control circuit
130. As shown in detail in FIG. 7A, the position sensor
assembly
126 is disposed upon the end cap
128 and is adapted to sense
the speed and position of the output shaft
88. The position sensor assembly
126 includes a flux ring holder, generally indicated at
132, that
fixedly supports at least one flux ring
134, and a magnet holder, generally
indicated at
136, that fixedly supports at least one magnet
138 in
spaced parallel relationship with respect to the flux ring
134. The position
sensor assembly
126 also includes an output shaft coupler, generally indicated
at
140, and a position sensor circuit, generally indicated at
142
for a purpose that will be explained in greater detail below.
The flux ring holder
132 is generally disk shaped having an end face
144.
The flux ring holder
132 is fixedly mounted to the end cap
128 and
has an annular shaped slot
146 in its end face
144 to receive and
retain the at least one flux ring
134. The flux ring
134 is formed
from a magnetically permeable material that is electrically capable of detecting
variations in magnetic flux lines as they pass over and through the ring. The flux
ring holder end face
144 also has an extended cylindrical protrusion
148
that extends toward the magnet holder
136.
The magnet holder
136 is generally cylinder shaped having an end face
150 that is in parallel abutment to the flux ring holder end face
144.
The magnet holder end face
150 has a receiving bore
152 that receives
the cylindrical protrusion
148 of the flux ring holder
132, which
serves as a rotational axis for the magnet holder
136. The magnet holder
136 further includes an annular shaped slot
154 in its end face
150
that is adapted to receive and retain an at least one magnet
138. On the
end opposite to the end face
150, the magnet holder
136 has a recessed
cavity
156 that receives and retains the output shaft coupler
140.
The output shaft coupler
140 serves as the physical connection between the
position sensor assembly
126 and the output shaft sensor end
100
having a magnet holder portion
158 and an output shaft receiving end
160.
The magnet holder portion
158 of the output shaft coupler
140 is
formed in a shape complementary to be received and retained by the recessed cavity
156 of the magnet holder
136 and the output shaft receiving end
160
is formed in a shape to receive and retained the sensor end
100 of the output
shaft
88. A foam insert
162 is disposed within the recessed cavity
156 for shock absorption. It should be appreciated by those having ordinary
skill in the art that the shaped portions of the recessed cavity
156 and
the output shaft coupler
140 may be formed in any suitable geometric shape,
as it is not necessary to have a zero degree orientation based on a physical reference
point for the output shaft
88. As will be discussed in greater detail below,
the "park", and the inner and outer sweep limits to the wiper, and hence the output
shaft
88 of the direct drive windshield wiper system
10, are programmed
into the present invention after it is installed on the vehicle.
The position sensor circuit
142 is supported upon the flux ring holder
132 and is in electrical communication with, and receives electromagnetic
signals from, the flux ring
134. More specifically, the position sensor
circuit
142 measures the flux variations generated within the flux ring
134. The position sensor circuit
142 is also in electrical communication
with the programmable control circuit
130. The flux variations from the
flux ring
134 are sensed as two quadrature electrical signals as the magnet
138, held within the magnet holder
136, is rotated about the stationary
flux ring
134 by the rotating output shaft
88. In the preferred embodiment,
a plurality of flux sectors
135 form the flux ring
134 and are offset
eccentrically from a single magnet
138. The flux ring
134 is positioned
such that the magnetic field induced within the flux ring
134 varies uniquely
for all angular displacements in the rotation of the output shaft
88. In
this manner, the position sensor circuit
142 produces an instantaneous signal
that is representative of a particular angular displacement of the output shaft
88 thereby allowing the position sensor
126 to act as an absolute
position sensor for detecting the angular position of the output shaft
88.
Additionally, as the output shaft
88 moves, the position sensor circuit
142 continuously produces position signals. Dynamically, this series of
signals allows the direction and speed of the output shaft
88 to be determined.
In the preferred embodiment, the magnet
138 is bipolar, however it should
be appreciated that the magnet
138 may also have multiple poles about its circumference.
In another non-limiting embodiment, at least one magnet
138 of an annular
ring shape is offset eccentrically from a singular flux ring
134. In either
case, since the position of the magnet
138 varies the flux, so no power
is required by the position sensor assembly
126 to follow the position of
the output shaft. Thus, if the power to the windshield wiper assembly
10
fails or the power to the vehicle is removed, the windshield wiper assembly
10
does not lose its orientation and can instantly recover its positional information
after power restoration. Therefore, the position sensor circuit
142 interprets
the magnetic flux signals and produces an output denoting the absolute position
of the output shaft
88 and routes that signal to the programmable control
circuit
130.
Alternately, the position sensor assembly
126 may be replaced
by a park sensing assembly. The park sensing assembly includes a magnetic "park
platform" disposed on the output shaft and a "park" hall sensor mounted within
the motor to detect the park platform. When the wiper assembly
10 is mounted
to a vehicle, the wiper assembly
10 is oriented so that during the first
half of the wipe area, the park platform is positioned such that it covers the
park sensor. If the wiper assembly
10 is operating and the power is lost
and then recovered, the park hall sensor will be in a relative position to either
sense the park platform or not. If the park sensor senses the park platform, then
the output shaft is in the first half of the wipe area and it is safe for the microprocessor
to perform an out-wipe. If the park hall sensor does not sense the platform then
the output shaft must be on the second half of the wipe area and it is safe for
the microprocessor to perform an in-wipe. In either case, the park sensor will
detect the platform edge, which is used as the position reference along the wipe
path. This platform crossing provides opportunity for the microprocessor to obtain
correct position. It should be noted that this embodiment must be used with additional
physical sensors positioned about the motor windings that would provide a "pulse
train" of position signals for an accurate determination of wiper arm position.
This pulse train would be available with the "sensored" commutation scheme discussed below.
The programmable control circuit
130, generally indicated in FIG. 7 is
shown in block diagram form in FIG.
8. The control circuit
130 is
a group of circuits mounted on a printed circuit board
164 that is disposed
within the electronics housing
24 that provides electric and electronic
circuits to control the operation of the motor
12 so as to effect the position
and speed of the windshield wiper
14. The programmable control circuit
130
includes a 3 (three) phase motor driver circuit
166, a current sensor
168,
a back-electromotive force (BEMF) sensor
169, a voltage regulator
170,
a solenoid driver
172, a microprocessor
174, and at least one serial
communications interface
176. The circuit board
164 also includes
a 6-pin connector
178 and an 8-pin connector
180 to allow electrical
communication with the other components of the system.
The 3-phase motor driver circuit
166 provides electromotive force to drive
the motor. The 3-phase motor driver circuit
166 is a bridge circuit that
utilizes 6 (six) N-Channel power MOSFET semiconductor devices in three half-bridges
between the input voltage and the return, or ground. The microprocessor
174
provides pulse width modulated (PWM) triggering, or biasing, signals to the 3-phase
bridge driver circuit
166. These signals drive the MOSFETs and produce three
separate voltages to apply to the stator windings. The 3 half-bridges produce the
three output voltages in three separate
