WO2001025064A1

WO2001025064A1 - Wiper motor system

Info

Publication number: WO2001025064A1
Application number: PCT/US2000/026903
Authority: WO
Inventors: Robert F. Birkenstock
Original assignee: McCord Winn Textron Inc
Current assignee: McCord Winn Textron Inc
Priority date: 1999-10-01
Filing date: 2000-09-29
Publication date: 2001-04-12
Anticipated expiration: 2002-04-01
Also published as: AU7738700A

Abstract

A wiper motor system has a motor controller (32A) for controlling an output shaft (14A, 14B) of a motor (12A, 12B) based on information received from a rotational position sensor (36A, 36B) and a mechanical resistance sensor (38A, 38B). The motor controller (32A) is capable of changing the instantaneous RPM or output torque of the motor (12A, 12B) based on the rotational position of the wiper arm (16A, 16B) or the amount of mechanical resistance coupled to the output shaft (14A, 14B) of the motor (12A, 12B). A wiper system having two non-mechanically linked motors (12A, 12B) includes a motor controller (32A) to prevent the wiper arms (16A, 16B) coupled to each motor (12A, 12B) from colliding. A linkage coupled to a motor (12A, 12B) converts the rotation of the output shaft (14A, 14B) of the motor (12A, 12B) to a reciprocating motion of a wiper arm (16A, 16B).

Description

WIPER MOTOR SYSTEM The present invention relates to a wiper motor system for use in motor vehicles. Particular utility of the present invention is in windshield wiper motors, including front and rear windshields, although other utilities, for example, headlamp wiper motors, are contemplated herein. Wiper motors have been utilized almost since the inception of the automobile. Traditional wiper motors typically utilize a dc motor (brush or brushless) that is attached to linkage to drive one or more wiper blades. This linkage is often expensive to manufacture (complex tooling requirements, etc.) and install. The linkage also has inherent mechanical resistance, which must be overcome by using a larger motor, and is a high warranty. Typical dc brush or brushless motors in wiper applications are required to be large for the torque necessary to drive a wiper blade or blades, and to overcome the mechanical resistance of the blade on a surface and the linkage resistance. Since these motors are mostly found in the firewall area of an automobile, real estate is often at a premium. External control circuitry is usually included, thereby ^' requiring extra space. Additionally, traditional wiper motor control systems have not included control circuitry that permits acceleration/deceleration to occur within a single stroke. Accordingly, it is an object of the invention to overcome the disadvantages of the prior art and to provide a wiper motor system which offers strong torque characteristics, electronic control and a relatively low profile (flat) motor design to facilitate placement in a motor vehicle. In addition, it is also an object of the present invention to provide a wiper motor system wherein a motor can be used to directly operate each wiper, wherein the path of the wipers and the syncl ronizatoin of the wipers are controlled electronically from a motor controller along with a separate signal sent to another controller to guide the wiper path. In one aspect, the present invention accomplishes the above objectives, and includes a wiper motor system for a front or rear windshield that includes an electrically commutated dc motor having a lower profile than conventional dc motors. The system also includes a wiper arm that is directly coupled to the output shaft of the motor, thereby eliminating the need for linkage, and providing direct drive for the wiper arm. In another aspect of the present invention, a cam mechanism is utilized to permit the wiper motor to spin in a single direction, while translating that rotation to impart a forward and/or reverse motion of the wiper blade along a predetermined arc. In another aspect, the present invention includes a wiper motor control system that includes a motor controller that receives position feedback information, mechanical resistance feedback information, and operator input data as inputs thereto and supplies power to the motor. The control system also preferably includes additional circuitry to permit user-selectable or automatic acceleration/deceleration control within a single stroke. In additional embodiments, a dual-wiper system is disclosed wherein the controller is adapted to provide synchronized motion of each wiper, which also preferably includes independently controllable wiper motors. It will be appreciated by those skilled in the art that although the following description of the invention will proceed with reference being made to preferred embodiments, and the present invention is not intended to be limited to these preferred embodiments. Other features and advantages of the present invention will become apparent as the following description of the invention proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and wherein: FIG. 1A is a side view of a direct drive wiper motor consistent with the present invention; FIG. IB is an isometric view of a wiper arm consistent with the present invention; FIG. 2 is a block diagram of a control system for a wiper motor system consistent with the present invention: FIG. 3 is an overall view of a linked wiper motor system consistent with the present invention; FIG. 4A is a front view of a windshield cleared by a single wiper motor system consistent with the present invention; FIG. 4B is a front view of a windshield cleared by a two-wiper motor system consistent with the present invention: FIG. 5 is a block diagram of a control system for a two-wiper motor system consistent with the present invention; It should be noted that the preferred motor 12 of the present invention employs so-called "vertical" dc brushless motor technology. Vertical dc brushless motors differ from traditional dc brushless motors in that individual stator pole pieces, each having field windings, are arranged about the periphery of the motor to drive an alternating magnet arrangement, thereby defining a working flux gap that can be parallel or perpendicular to the axis of rotation. One clear advantage of vertical dc brushless motors over conventional dc motors is the ability to increase the torque strength by adjusting the distance from the axis of rotation to the stator pole pieces. Another advantage is the increased torque per unit volume of the motor. Also, since the working gap can be arranged perpendicular to the axis of rotation, the vertical motor technology can be made having a smaller profile over conventional dc motor designs. A more detailed discussion of vertical dc brushless motors can be found in U.S. Patent Nos. 4,745,345; 4,837,474; 4,949,000; 5,659,217 and 5,874,796, and each is incorporated herein by reference in its entirety. Figs. 1A and IB illustrate an exemplary configuration of a wiper motor system 10. The system includes a dc motor 12, in one embodiment a vertical brushless motor, driving a shaft 14. The wiper arm section 16 includes a blade 20 and an opening 18 to mate with shaft 14. To that end. shaft 14 and opening 18 are in one embodiment rotatably affixed using a keying slot on the shaft and opening or blot arrangement, or other means to ensure that the wiper ami 16 moves with the shaft 14. It will be understood by those skilled in the art that placement of the motor 10 within a vehicle can be chosen in accordance with the given space requirements and/or restrictions. For example, motor 12 can be mounted around the firewall of an automobile, for use in a direct drive windshield wiper system. Turning to Fig. 2, a block diagram of an exemplary control system 30 is depicted. The block diagram shows a single motor 12 for driving a single wiper blade drive 42. The control system can be used to control the single wiper motor system depicted in Figs. 3 and 4A. Essentially, control system 30 is a closed-loop design that includes a motor controller 32 to provide controlled power to motor 12. The control system also includes a position sensor 36 and a mechanical resistance sensor 38 producing feedback signals to controller 32. Position sensor 36 can include Hall- effect and/or rotary capacitive-type position sensors and/or other types of position sensors (e.g., optical) known in the art. Essentially, the position sensor 36 provides position information of the wiper arm 16 as the shaft 14 rotates. Position sensor 36 preferably includes fixed-range rotation sensing to indicate when the wiper arm 16 has reached the end of the stroke, in which case the motor reverses direction (i.e. by reversing polarity of power delivered to motor 12), or rotation of wiper arm 16 is translated to the opposite direction via a cam mechanism, discussed below. Mechanical resistance sensor 38 can include strain-gauge resistive networks or other similar sensor sufficient to indicate a resistance measurement of the wiper blade 20 relative to the wiper surface (e.g., windshield, headlamp, etc.). Preferably, controller 32 includes appropriate circuitry to permit automatic or user-selectable variable acceleration/deceleration within a stroke. This can be preferable to overcome, for example, variances in mechanical resistance in the travel path. Also, controllable deceleration can be advantageous as the wiper arm nears the end of its travel path to prevent undue wear on the system. Controller 32 preferably permits operator data 40 to be input into the controller 32 using, for example, intermittent switch, variable speed switch, etc. In a two-wiper motor system as shown in Figs. 4B and 5, it is preferable to employ a direct drive system as described above, i.e., one motor for each wiper blade. In this system, the controller 32A is preferably adapted to control the two wiper arms 16A and 16B so that motion occurs according to a preset (or user-supplied) pattern. The controller 32A can be adapted to receive feedback position information from both motors through position sensors 36A and 36B and may be further adapted to independently supply controllable power to each motor. As can be seen from the above discussion, Fig. 5 ultimately provides a block diagram of an exemplary control system 30A . The block diagram shows two motors 12A and 12B, each motor for driving a single wiper arm 16A and 16B. The block diagram can be used to control the two wiper motor system depicted in Fig. 4B. Essentially, control system 30A is a closed-loop design that includes a motor controller 32A to provide controlled power to motors 12A and 12B. The system also includes a pair of position sensors 36A and 36B. The sensors 36A and 36B generate signals relating to the rotational position of the output shafts 14A and 14B respectively. The sensors 36A and 36B can continuously send signals to the controller 32A as the output shaft rotates through its range of travel or only at discrete positions, such as the beginning of the range and the end of the range. The system may also include a pair of mechanical resistance sensor 38A and 38B. The sensors 38A and 38B generate signals relating to the amount of mechanical resistance the output shafts 14A and 14B encounter. Objects such as snow on the windshield can affect the resistance. Position sensors 36A and 36B can include Hall-effect and/or rotary capacitive-type position sensors and/or other types of position sensors (e.g., optical) known in the art. Essentially, the position sensors 36A and 36B provide position information of the wiper arms 16A and 16B as the shafts 14A and 14B rotate. Position sensors 36A and 36B preferably include fixed-range rotation sensing to indicate when each wiper arm has reached the end of the stroke, in which case the motor reverses direction (i.e. by reversing polarity of power delivered to motor 12), or rotation of wiper arms 16A and 16B is translated to the opposite direction via a cam mechanism, discussed below. Mechanical resistance sensors 38A and 38B can include strain-gauge resistive networks or other similar sensor sufficient to indicate a resistance measurement of the wiper blade 20A and 20B relative to the wiper surface (e.g., windshield, headlamp, etc.). As can be seen in Figure 4B, wiper blade 20A covers an area labeled A of windshield W as it rotates through its complete travel path and wiper blade 20B covers an area B of windshield W as it rotates through its complete travel path. The area A covered by wiper blade 20A overlaps the area B covered by wiper blade 20B. When two wiper motors 12A and 12B are used to control two w ipers 20A and 20B respectively, there is a possibility of a collision of the wiper blades. The motor controller 32 receives signals from each of the sensors 36A and 36B and adjusts the rotational speed of the output shaft 14A or 14B. or both to prevent the wiper blades 20A and 20B from colliding. Alternatively, the motor controller 32 can adjust when the motors 12A or 12B turn on or reverse direction in order to prevent the wiper blades 20A and 20B from colliding. Alternatively, the motor controller 32 can adjust the rotational speed of either or both of the output shafts 14A and 14B and adjust the time at which the motors 12A or 12B turn on or reverse direction. The motor controller 32A can be used in direct drive wiper motor systems and wiper motor systems that includes a cam mechanism, discussed below. Turning now to Fig. 3, an alternative to the direct drive system of Figs. 1A and IB is disclosed. In this embodiment, a linkage system and'or cam mechanism is employed between the motor output shaft 14 and the wiper aπn 46. In this system, complex control circuitry is avoided, since single-direction rotation of the motor is translated into dual-direction motion of the wiper blade, via linkage, discussed below. In this embodiment, the wiper motor 12 preferably includes a cam disk 42 coupled to the output shaft 14 (not shown). Coupled to the cam disk 42 is linkage member 44 and wiper ami 46, as shown. More specifically, member 44 is mounted to the cam disk 42 and wiper aπn 46 via links 48 and 50, respectively. Preferably, links 48 and 50 permit unencumbered movement of the relative pieces. In other words, it is preferred that the links 48 and 50 do not contribute appreciable drag to the system. To translate the rotation of the disk 42 into the oscillating motion of the wiper, boss pin 52 is provided. Boss pin 52 is stationary with respect to the linkage member 44 and wiper arm 46, thereby permitting wiper arm 46 to pivot about the boss pin 52, as directed by member 44. Those skilled in the art will recognize that the length of member 44 and wiper arm 46, the position of boss pin 52. and the diameter of cam disk 42. either alone or in combination, will dictate the sweep area of the wiper blade 20. Thus, these components can be sized accordingly to provide a desired sweep area. Likewise, the rotational speed of the motor 12 and the radius at which member 44 is off center will dictate the nominal speed at which the wiper rotates through one cycle. Additionally, control circuitry can be provided (as described above in Fig. 2) to permit intcπnittent operation and/or speed control of the motor. In sum, as described herein, the present invention provides a wiper motor system having a lower profile over traditional motor designs, and which includes a controller that permits automatic or user-selectable acceleration and deceleration control within a stroke of rotation of the wiper blade. In one embodiment, a direct drive system is utilized in which a motor is attached directly to a wiper arm. In a wiper motor system having two or more wiper blades, a controller prevents collisions of the two wiper blades. In another embodiment, a cam/linkage system is employed which peπnits single direction motion of the motor, while translating the rotation of the motor into a predetermined oscillation of a wiper arm. Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

We claim: 1. A wiper motor system, comprising: (a) a motor 12 having an output shaft 14 coupleable to a wiper arm 16, 46, said output shaft 14 positioned relative to a surface, said motor 12 providing a selected rate of movement and selected direction of movement for said output shaft 14; (b) a first sensor 36 for determining said output shaft position; (c) a second sensor 38 for determining mechanical resistance to said output shaft 14; (d) a motor controller 32 for controlling said direction and said rate of movement of the output shaft 14 based on a signal received from said first sensor 36 and a signal received from said second sensor 38.

2. The wiper motor system of claim 1, wherein said motor 12 is a vertical dc brushless motor.

3. The wiper motor system of claim 1, wherein said mechanical resistance comprises frictional resistance.

4. The wiper motor system of claim 1, further comprising a memory 102 for storing said output shaft position and said mechanical resistance to said output shaft.

5. The wiper motor system of claim 1, wherein said motor controller 32 also provides a selected output torque for said output shaft 14.

6. The wiper motor system of claim 1, further comprising a memory 102 for storing a relationship between said output shaft position, said mechanical resistance, and said rate of movement.

7. The wiper motor system of claim 1, wherein said motor controller 32 provides a selected output torque to said output shaft 14 in response to a signal received from said second sensor 38.

8. The wiper motor system of claim 1, wherein the system generates a signal if the mechanical resistance to said output shaft 14 exceeds a predetermined level.

9. The wiper motor system of claim 8, wherein said signal is communicated to an operator of a vehicle.

10. The wiper motor system of claim 1 , wherein said wiper arm 16, 46 travels from a first position to a second position, reverses direction, and travels back to said first position when said output shaft moves from a first output position to a second output position, reverses direction, and travels back to said first output position.

1 1. The wiper motor system of claim 10, wherein said controller 32 decreases the rate of movement of said output shaft 14 as said output shaft 14 approaches said first output position or said second output position.

12. A wiper motor system, comprising: (a) a motor 12 having an output shaft 14 coupleable to a wiper arm 16, 46, said output shaft 14 positioned relative to a surface, said motor 12 providing a selected rate of movement and selected direction of movement for said output shaft 14; (b) a first sensor 36 for detennining said position of said output shaft 14; (c) a motor controller 32 for controlling said direction and said rate of movement of said output shaft 14 based on a signal received from said first sensor 36.

13. The wiper motor system of claim 12, wherein said motor 12 is a vertical dc brushless motor.

14. The wiper motor system of claim 12, further comprising a second sensor 38 for determining the mechanical resistance to said movement of said output shaft 14, and wherein said motor controller 32 provides a selected torque to said output shaft 14 based upon a signal received from said second sensor 38.

15. The wiper motor system of claim 12, wherein said wiper arm 16, 46 travels from a first position to a second position, reverses direction, and travels back to said first position when said output shaft moves from a first output position to a second output position, reverses direction, and travels back to said first output position.

16. The wiper motor system of claim 15, wherein said controller 32 decrease the rate of movement of said output shaft 14 as said output shaft 14 approaches said first output position or said second output position.

17. A wiper motor system for coordinating the cleaning action of two wiper blades, comprising: (a) a first motor 12A having a first output shaft 14A coupleable to a first wiper arm 16A; (b) a second motor 12B having a second output shaft 14B coupleable to a second wiper aπn 16B; (c) a first sensor 36A for determining the position of said first output shaft 14A; (d) a second sensor 36B for determining the position of said second output shaft 14B; (e) a motor controller 32A for controlling the position of said output shaft 14A of said first and said second motors 12A, 12B based on signals received from said first sensor 36A and said second sensor 36B.

18. The wiper motor system of claim 17 wherein said motor 12 A, 12B is a vertical dc brushless motor.

19. The wiper motor system of claim 17. further comprising a third sensor 38A and a fourth sensor 38B for determining the mechanical resistance to said first and said second output shafts 14A, 14B, and wherein said motor controller 32A controls the torque of said first and second output shafts 14A, 14B based upon a signal received from said third and fourth sensors 38A, 38B.

20. The wiper motor system of claim 17, wherein said wiper arm 16A, 16B travels from a first position to a second position, reverses direction, and travels back to said first position when said output shaft 14A, 14B moves from a first output position to a second output position, reverses direction, and travels back to said first output position.

21. The wiper motor system of claim 20, wherein said controller 32A decrease the rate of movement of said output shaft 14A, 14B as said output shaft 14A, 14B approaches said first output position or said second output position.