JP2010148300A - Motor with speed reduction mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To assure a desired positional detection even if an excessive external force is applied to an output shaft. <P>SOLUTION: In a wiper motor having a motor shaft with a worm 32a formed at the end thereof, a worm wheel 32b engaged with the worm 32a, and an output shaft 17 that is provided in the worm wheel 32b and decelerates and outputs the rotation of the motor shaft, a magnet 37 that constitutes a position detection means together with an MR sensor 38 is fixed to an end face of the output shaft 17, and a clutch mechanism 42 is provided between the output shaft 17 and the worm wheel 32b. The clutch mechanism 42 is so set as to allow rotation between the output shaft 17 and the worm wheel 32b when an external force of a predetermined value or more is applied to the output shaft 17. When the external force applied to the output shaft reaches an allowable value for rotation, the clutch mechanism is decoupled and then the worm wheel runs idle with respect to the output shaft, allowing the magnet to keep the positional relationship with the MR sensor. Accordingly, a desired sweeping operation can be maintained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a motor with a speed reduction mechanism.
For example, the present invention relates to a device that is effective when used for a wiper motor that drives a wiper device mounted on a vehicle.

A motor with a worm gear reduction mechanism is used as a wiper motor as a drive source for driving a wiper device mounted on a vehicle.
In this type of conventional wiper motor, the output shaft linked to the wiper arm is coupled to the worm wheel of the worm gear reduction mechanism by the involute part, the magnet is fixed to the worm wheel, and it is arranged opposite to the worm wheel. Some circuit boards are provided with a magnetic sensor for detecting a magnet. For example, see Patent Document 1.

JP 2007-124792 A

  However, in the wiper motor described above, when an external force such as snowfall is applied to the wiper arm, if the involute part of the wiper shaft slips, the recognition position of the wiper arm and the magnet will shift, so the desired wiping operation is performed. There is a risk that it cannot be maintained.

  An object of the present invention is to provide a motor with a speed reduction mechanism that can ensure the desired position detection even when an excessive external force is applied to an output shaft.

Typical means for solving the above-described problems are as follows.
(1) a motor unit having a motor shaft;
A speed reduction mechanism for reducing the rotation of the motor shaft and transmitting it to the output shaft;
A motor with a speed reduction mechanism,
A clutch mechanism that allows rotation between the output shaft and the speed reduction mechanism when an external force greater than or equal to a predetermined value is applied to one end of the output shaft;
Position detection means is provided at the other end of the output shaft.
A motor with a speed reduction mechanism.
(2) The motor with a speed reduction mechanism according to (1), wherein the position detection unit is provided on an end surface of the output shaft.
(3) The electric motor with a speed reduction mechanism according to (1) or (2), wherein the output shaft is linked to a wiper device.

  According to this motor with a speed reduction mechanism, the expected position detection can be ensured even when an excessive external force is applied to the output shaft.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a wiper device 11 is provided below the windshield 13 of the vehicle 12 for wiping rain water and the like attached to the windshield 13 to ensure the driver's field of view.

  The wiper device 11 includes two wiper shafts 14 and 17 that are rotatably supported by the vehicle 12. The wiper shaft 17 is fixed with a wiper arm 15 a on the driver's seat side, and the wiper shaft 14 is fixed with a wiper arm 15 b on the passenger seat side. Wiper blades 16a and 16b are attached to the distal ends of the wiper arms 15a and 15b, and springs (not shown) are attached to the base ends of the wiper arms 15a and 15b. Due to the spring force of the spring, the wiper blades 16a and 16b can be brought into elastic contact with the windshield 13.

  A wiper motor 10 is assembled to the wiper device 11. The wiper motor 10 is constituted by a motor with a worm gear speed reduction mechanism, and can swing at a predetermined angle by performing forward and reverse rotation. A link mechanism 19 is rotatably attached to the wiper shaft 17, and by rotating the wiper shaft 17, the wiper arms 15 a and 15 b can be swung within a predetermined angle range. By the swinging movement of the wiper arms 15a and 15b, the wiper blades 16a and 16b can be operated in the wiping ranges 20a and 20b between the upper reversal position and the lower reversal position. It becomes possible to do.

As shown in FIG. 2, the wiper motor 10 includes an electric motor 22 having a motor shaft 21 and a speed reduction mechanism portion 23 that decelerates and outputs the forward and reverse rotation of the motor shaft 21. The electric motor 22 is a DC motor with a brush. A field magnet (not shown) is fixed inside the motor housing 24, and an armature 25 and a commutator 26 are rotatably accommodated.
Although the brushed DC motor is used as the electric motor 22, the invention is not limited to this, and another type of electric motor such as a brushless DC motor may be used.

On the other hand, the speed reduction mechanism unit 23 includes a gear housing 30 assembled to the motor housing 24, and a worm gear speed reduction mechanism 32 as a speed reduction mechanism is accommodated in the gear housing 30. The motor shaft 21 of the electric motor 22 extending into the gear housing 30 is rotatably supported via a bearing 33, and the output shaft 17 is rotatably supported by a boss portion 30 a of the gear housing 30.
A worm 32 a is fixed to the motor shaft 21, and a worm wheel 32 b that meshes with the worm 32 a is fixed to the output shaft 17. A worm gear reduction mechanism 32 is formed by the worm 32a and the worm wheel 32b.
A housing cover 31 as a cover member is assembled in the opening of the gear housing 30. The housing cover 31 is formed by processing such as pressing using a magnetic material such as iron, steel, and stainless steel.

As shown in FIG. 2, a drive control unit 35 including a circuit board 34 is accommodated in the gear housing 30. The circuit board 34 is disposed so as to cover the worm gear reduction mechanism 32. On the lower surface 34a of the circuit board 34, an FET (field effect transistor) 36 as a power system component that supplies driving power to the electric motor 22 is mounted, and a relay, a diode, a capacitor, and the like (not shown) are mounted. .
A rotation-detecting magnet 37 having a north pole and a south pole magnetized in the circumferential direction is fixed to the output shaft 17 of the worm wheel 32b. (Magnetic resistance sensor) 38 is mounted so as to face the magnet 37. The magnet 37 and the MR sensor 38 constitute position detecting means for detecting the rotational speed and shaft angle of the output shaft 17.
That is, when the wiper motor 10 is driven, the magnet 37 rotates relative to the MR sensor 38, so that the magnetic field change accompanying switching of the N pole and the S pole at this time is changed. By detecting by 38, the rotational state of the wiper motor 10 can be detected. The driving power for the electric motor 22 is controlled based on the operating positions of the wiper blades 16a and 16b grasped by the detection signal from the MR sensor 38.

  Silicone 39 as a heat transfer material is applied to the upper surface 34 b of the circuit board 34, and the circuit board 34 comes into contact with the housing cover 31 through the silicone 39. That is, heat is generated by supplying a drive current to the FET 36, but the generated heat is not stored in the FET 36, and is released from the silicone 39 to the outside air via the housing cover 31.

As shown in FIG. 3, a cap 40 made of a non-magnetic material is put on the end of the output shaft 17 on the side of the circuit board 34 and fixed by a knurled portion 41. A magnet 37 is fixed to the surface of the cap 40 facing the MR sensor 38.
A clutch mechanism 42 is provided between the output shaft 17 and the worm wheel 32b to allow rotation between the output shaft 17 and the worm wheel 32b when an external force greater than a predetermined value is applied from the output shaft 17. .
That is, the clutch mechanism attachment portion 43 is disposed in the vicinity of the cap 40 on the output shaft 17 and protrudes in a circular ring shape. An engagement hole 44 as an engagement portion is formed on the outer peripheral surface of the clutch mechanism attachment portion 43. There are a plurality of (four in the illustrated example) arranged at equal intervals in the circumferential direction. Each engagement hole 44 is formed in a substantially hemispherical shape. A clutch ring 45 is fitted to the outer periphery of the clutch mechanism mounting portion 43 so as to be slidable in the circumferential direction. The clutch ring 45 is arranged concentrically with the worm wheel 32b and is fixed by a key portion 46. The clutch ring 45 has a plurality of holding holes 47 (four in the illustrated example) arranged at equal intervals in the circumferential direction and opened so as to penetrate in the radial direction. Each holding hole 47 holds a ball 48 and a spring 49 as an engaging portion, and the spring 49 always applies a reaction force to the worm wheel 32b to urge the ball 48 radially inward. Yes.
That is, each ball 48 is engaged with each engagement hole 44 by the urging force of the spring 49, whereby the output shaft 17 and the worm wheel 32b are connected to each other. Is applied, the balls 48 come out of the engagement holes 44 against the urging force of the spring 49, thereby releasing the connection between the output shaft 17 and the worm wheel 32b. Therefore, the predetermined value of the external force that allows the clutch mechanism 42 to rotate between the output shaft 17 and the worm wheel 32 b can be set in advance by the elastic force of the spring 49.

Next, operations and effects when an external force of falling snow is applied to the wiper device will be described.
During the wiping operation of the wiper device 11, when an external force such as snowfall is applied to the wiper arms 15 a and 15 b and / or the wiper blades 16 a and 16 b, the output shaft 17 is stopped, but the electric motor 22 moves the motor shaft 21. As the rotation continues, the worm wheel 32b tries to rotate.
When the rotational force of the worm wheel 32b by the electric motor 22 reaches a preset rotation allowable value of the clutch mechanism 42, the connection between the engagement hole 44 of the clutch mechanism 42 and the ball 48 is released. 32 b idles with respect to the output shaft 17.
Accordingly, since the driving force of the electric motor 22 is not transmitted to the output shaft 17, damage to the wiper shafts 14a and 14b, the wiper arms 15a and 15b, the wiper blades 16a and 16b, etc. of the wiper device 11 can be prevented.
On the other hand, the worm wheel 32b idles with respect to the output shaft 17. However, since the magnet 37 is fixed to the output shaft 17, the magnet 37 can maintain the positional relationship with the MR sensor 38.

For example, after an external force such as snowfall is removed from the wiper arms 15a and 15b and / or the wiper blades 16a and 16b, when the electric motor 22 is operated, the worm wheel 32b is rotated by the motor shaft 21 of the electric motor 22. Therefore, the ball 48 of the clutch mechanism 42 moves to engage with the engagement hole 44, and the clutch mechanism 42 is automatically connected.
Alternatively, the wiper arms 15 a and 15 b may be manually moved to a position where the ball 48 of the clutch mechanism 42 engages with the engagement hole 44 with the electric motor 22 stopped.
At this time, since the magnet 37 maintains the positional relationship with the MR sensor 38, that is, the wiper arms 15 a and 15 b are not recognized by the MR sensor 38, the worm wheel 32 b is idle with respect to the output shaft 17. Even after this, the wiper device 11 can maintain the desired wiping operation.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  For example, the clutch mechanism is not limited to the structure of the above-described embodiment, and may be configured using a wire spring or a leaf spring formed in a ring shape.

  The speed reduction mechanism is not limited to the worm gear mechanism, and other types of speed reduction mechanisms such as a speed reduction gear train composed of a plurality of spur gears may be used.

  The MR sensor 38 and the magnet 37 are not limited to be arranged on the rotation center of the worm wheel 32b, but may be arranged at a position shifted from the rotation center of the worm wheel 32b.

  Further, although the MR sensor 38 is employed as a magnetic sensor for detecting the rotation speed and the shaft angle of the output shaft 17, the present invention is not limited to this, and a Hall element may be used as the magnetic sensor.

  In the above embodiment, the case where the electric motor with a speed reduction mechanism is used for the wiper motor has been described. However, the present invention is not limited to this, and the electric motor with the speed reduction mechanism used in power window devices, door opening / closing devices, etc. Can be applied to.

It is a front view which shows the wiper apparatus in which the wiper motor which is one embodiment of this invention was used. It is a longitudinal section showing a wiper motor which is one embodiment of the present invention. The clutch mechanism is shown, (a) is a longitudinal cross-sectional view, (b) is a cross-sectional view taken along line bb of (a).

Explanation of symbols

10 Wiper motor (Electric motor with reduction mechanism)
DESCRIPTION OF SYMBOLS 11 Wiper apparatus 12 Vehicle 13 Windshield 14 Wiper axis | shaft 15a Wiper arm 15b Wiper arm 16a Wiper blade 16b Wiper blade 17 Wiper axis | shaft (output axis)
19 Link mechanism 20a, 20b Wiping range 21 Motor shaft 22 Electric motor 23 Reduction mechanism 24 Motor housing 25 Amateur 26 Commutator 30 Gear housing (housing)
31 Housing cover (cover member)
32 Worm gear reduction mechanism 32a Worm 32b Worm wheel 33 Bearing 34 Circuit board 35 Drive controller 36 FET (power system parts)
37 Magnet (position detection means)
38 MR sensor (magnetic sensor, position detection means)
40 Cap 41 Knurled portion 42 Clutch mechanism 43 Clutch mechanism mounting portion 44 Engagement hole 45 Clutch ring 46 Key portion 47 Holding hole 48 Ball 49 Spring

Claims (3)

A motor unit having a motor shaft;
A speed reduction mechanism for reducing the rotation of the motor shaft and transmitting it to the output shaft;
A motor with a speed reduction mechanism,
A clutch mechanism that allows rotation between the output shaft and the speed reduction mechanism when an external force greater than or equal to a predetermined value is applied to one end of the output shaft;
Position detection means is provided at the other end of the output shaft.
A motor with a speed reduction mechanism.   The motor with a speed reduction mechanism according to claim 1, wherein the position detection unit is provided on an end surface of the output shaft.   The electric motor with a speed reduction mechanism according to claim 1, wherein the output shaft is linked to a wiper device.

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