JPH0781525A - Wiper driving device - Google Patents

Abstract

PURPOSE:To prevent the meshing ratio of a gear from being decreased even when rotational load of a worm wheel is high by restraining relief of a worm gear from the worm wheel. CONSTITUTION:A wiper driving device is provided with a wiper motor 10 wherein a worm gear 20 is attached to a rotary shaft 11, a first worm wheel meshed with the worm gear 20, and for reciprocating a wiper arm through a link mechanism by taking the rotary shaft 21a as an output shaft, and a second worm wheel 22 so provided as to be meshed with the worm gear 20 in the position to face the first worm wheel 21 through the worm gear 20, and for restraining relief of the worm gear 20 from the first worm wheel 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiper drive device, and more particularly to improvement of a gear system for transmitting a driving force of a motor.

[0002]

2. Description of the Related Art In a conventional wiper drive device, a worm gear 2 is attached to a rotary shaft 1a of a motor 1 as shown in FIG. 5, and a worm wheel 3 meshing with the worm gear 2 is attached.
Is provided in the housing 4, and the wiper is reciprocated through a link mechanism (not shown) using the rotary shaft 3a of the worm wheel 3 as an output shaft (as a conventional technique of this type, for example, Japanese Utility Model Laid-Open No. 63-51559). There is something to show.).

[0003]

However, in the above-described conventional wiper drive device, since the worm gear 2 is cantilevered, when the rotational load of the worm wheel 3 increases, the worm gear 2 escapes in the direction away from the worm wheel 3, The meshing ratio of the gears may be reduced, and stress may be concentrated on the outer peripheral side of each gear tooth, which may cause a strength problem.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and suppresses the escape of the worm gear from the worm wheel, and even when the rotational load of the worm wheel is high, the gear engagement ratio is high. An object of the present invention is to provide a wiper drive device that does not deteriorate.

[0005]

In order to achieve the above-mentioned object, a wiper drive device according to the present invention is meshed with a wiper motor having a worm gear attached to its rotary shaft, and is linked with the rotary shaft as an output shaft. A first worm wheel that reciprocates the wiper arm via a mechanism, and a worm gear that is provided so as to mesh with the worm gear at a position facing the first worm wheel via the worm gear. And a second worm wheel for restraining.

[0006]

According to the structure of the present invention described above, even when the rotational load of the first worm wheel becomes high, the force acting on the worm gear in the direction of separation from the first worm wheel is applied to the second worm wheel. It is possible to suppress the escape of the worm gear.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wiper drive device according to the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a wiper drive device according to the present invention.

In the wiper drive device of the embodiment, as shown in FIG. 1, a wiper motor 10 having a worm gear 20 attached to a rotary shaft 11 is meshed with the worm gear 20, and a rotary shaft 21a is used as an output shaft for a link (not shown). The first worm wheel 21 that reciprocates the wiper blade via the mechanism.

A second worm wheel 22 that meshes with the worm gear 20 is provided at a position facing the first worm wheel 21 via the worm gear 20. The second worm wheel 22 receives the force in the separating direction from the first worm wheel 21 that acts on the worm gear 20 when the rotational load of the first worm wheel 21 becomes high, and suppresses the escape of the worm gear 20. Has an effect.

The gear system composed of these worm gears 20, first and second worm wheels 21, 22 is
It is provided in the housing 30.

Further, the first worm wheel 21 has
As shown in FIG. 2, a contact board 23 that rotates integrally is provided, and on the contact board 23, contact plates 23a and 23b as shown in FIG. 3 are provided. The lid 31 that covers the open side of the housing 30 is provided with a first contact piece set 24 that contacts the contact plate 23.
The contact plates 23a and 23b and the contact piece set 24 are used in a known auto-stop mechanism that stops the wiper blade at a prescribed storage position even if the wiper switch is turned off at an arbitrary position.

On the other hand, the second worm wheel 22 has
As shown in FIG. 3, the two contact plates 22a, 22b
2 is provided, and as shown in FIG. 2, the lid 31 is provided with a second contact piece set 22c that comes into contact with these contacts. The inner contact plate 22a is continuously provided on the circumference, and the outer contact plate 22b is provided only on a part of the circumference. These contact plates 22a and 22b are electrically connected inside.
The contact plates 22a and 22b and the contact piece set 22c constitute rotation speed detection means for detecting the rotation speed of the second worm wheel 22.

Next, the electric system of the wiper driving device of the embodiment will be described with reference to FIG.

The current from the battery BATT is the resistance R1 and R provided in parallel by the electromagnetic switch SW1.
It is supplied to the wiper motor 10 through a wiper switch SW2 which switches ON / OFF of the wiper by flowing into any of 2, R3 and R4.

The control means for changing the supply voltage to the wiper motor are resistors R1, R2, R3, R4 and an electromagnetic switch S.
It is composed of W1 and W1. The resistance value of the four resistors is R1
>R2>R3> R4.

One pulse is generated from the contact piece set 22c every one rotation of the second worm wheel 22, and the rotation speed detecting means 40 determines the rotation speed of the second worm wheel 22 based on this pulse interval. When the change in the rotation speed due to the load change of the wiper is detected,
The resistance is selected by switching the electromagnetic switch SW1 so as to change the voltage supplied to the wiper motor 10 in the direction of suppressing the change in the rotation speed.

The wiper switch SW2 is connected to the contact B when the wiper is in operation and always supplies a current, and is connected to the contact M when not in operation. Contact plates 23a, 2
When the wiper switch SW2 is connected to the contact M, the auto stop mechanism having 3b and the first contact piece set 24 forms an electric circuit until the wiper blade returns to the fixed position to rotate the wiper motor. At the same time, when returning to the home position, the armature circuit is short-circuited and an electric brake is applied to stop the wiper blade at the home position.

The wiper motor 10 has a constant magnetic field of PM.
Formula, and three brushes 10 that contact the commutator
It has a, 10b, and 10c. First brush 10a
Is connected to the positive electrode and the second and third brushes 10 are connected.
b and 10c are selectively connected to the negative electrode by the speed changeover switch SW3, and the speed of the wiper can be switched between low speed and high speed by the selection.

The electromagnetic switch SW1 has resistors R1 and R, respectively.
The relationship between the rotational speed N and the torque T (NT characteristic) when connected to 2, R3 and R4 is as shown by the thin lines in the graph of FIG.

When the rotation speed N of the second worm wheel 22 exceeds the line of the allowable range ± α with respect to the set rotation speed N1, the electromagnetic switch SW1 switches the switch to change the resistance to be connected to the motor. Change the applied voltage. The change in the NT characteristic due to the switching of the electromagnetic switch SW1 is as shown by the bold line in the graph of FIG.

For example, when the switch S is connected to the resistor R1, the torque T increases due to an increase in the rotation load of the first worm wheel, and the rotation speed N decreases and falls below N1-α. Upon receiving a signal from the rotation speed detecting means, the connection of the electromagnetic switch SW1 is switched to the resistance R2. As a result, the voltage applied to the wiper motor rises and the rotation speed rises to N1 + α. Similarly, as the rotational load increases, the connection of the switch S is sequentially switched to the resistors R3 and R4, so that when the torque is in the range of T1 to T2, the rotational speed is stabilized within the range of N1 ± α. Can be made.

When the torque decreases, the rotation speed can be stabilized by sequentially switching the connection of the switch S to the resistors R3, R2 and R1.

In the above embodiment, only four resistors are provided as control means for changing the voltage supplied to the wiper motor and an electromagnetic switch is provided to switch between them. However, this is not always the case. The number of resistors is not limited, and a variable resistor may be used.

[0024]

As described above, according to the present invention, by providing the second worm wheel facing the first worm wheel via the worm gear, the first worm wheel acting on the worm gear can be removed. It is possible to cancel the moment in the separating direction and prevent a reduction in the meshing ratio due to the escape of the worm gear.

Further, by detecting the rotational speed of the second worm gear and changing the applied voltage so that the rotational speed becomes constant, the reciprocating speed of the wiper blade can be kept within a certain range. Exerts a beneficial effect.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing an embodiment of a wiper drive device according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a circuit diagram showing a drive circuit of a wiper motor.

FIG. 4 is a graph showing a change in NT characteristic due to switching of a switch.

FIG. 5 is a plan view similar to FIG. 1, showing a conventional wiper drive device.

[Explanation of symbols]

Claims (2)

[Claims] 1. A wiper motor having a worm gear mounted on a rotary shaft, a first worm wheel meshing with the worm gear, and reciprocating a wiper blade via a link mechanism with the rotary shaft as an output shaft, and the worm gear. And a second worm wheel that is provided so as to mesh with the worm gear at a position opposed to the first worm wheel via the second worm wheel and that suppresses escape of the worm gear from the first worm wheel. Wiper drive device. 2. A rotation speed detecting means for detecting the rotation speed of the second worm wheel, and based on an output of the rotation speed detecting means, when a change in the rotation speed due to a load change of the wiper is detected, The wiper drive device according to claim 1, further comprising: a control unit that changes a supply voltage to the wiper motor in a direction in which a change in rotation speed is suppressed.