JPH0537902Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electric power assist device that assists input with an electric motor, and more specifically, to reduce input torque in a steering device of a vehicle, etc. This invention relates to improvements in electric power auxiliary equipment for

[Conventional technology]

An example of an electric power steering device is Utility Application No. 60-189605
This is shown in FIG. 12. This device includes an input shaft 4 into which rotational torque is input, a detection means 14 that detects the input torque, an electric motor 2 that provides a rotational output based on the detection, and a rotational output of the electric motor 2 that is transmitted to an output shaft 6. It consists of gear means 12. The gear means 12 meshes with a first gear 20 on a motor shaft 16 of the electric motor 2, a second gear 22 and a third gear 24 on an intermediate shaft 18 that decelerates the rotation of the motor shaft 16, and a third gear 24. It consists of a final gear 26 that transmits torque to the output shaft 6.

[Problem that the invention attempts to solve]

In the conventional electric power steering system as described above, since a gear mechanism is used to transmit the rotational output of the electric motor to the output shaft, there is a problem caused by bumps that occur in the meshing part of the gears. . When machining gears, dimensional variations cannot be avoided unless the gears are machined with high precision, and it is common practice to provide a suitable backlash to ensure smooth torque transmission. In a gear mechanism having such a backlash, when the torque transmission direction of the motor is reversed, for example, the gears idle by the amount of backlash between the first gear 20 and the second gear 22, and between the third gear 24 and the final gear 26, After that, the gears collide into each other in a collision. The spinning and collisions at this time cause abnormal noises and unpleasant steering sensations.

The present invention aims to eliminate the abnormal noise and unpleasant steering sensation caused by the bumps in the conventional electric power assist mechanism described above.

[Means for solving problems]

In order to achieve the above object, in the present invention, the gear means 112 for transmitting the driving force of the electric motor 102 to the output shaft 106 has a gear means 124 fixed to the electric motor side and a gear means 124 fixed to the output shaft side. It consists of a main gear 126 and an auxiliary gear 127.
The main gear 126 and the auxiliary gear 127 are coaxially attached, and have the same shape and number of teeth 126a and 1.
27a, and is urged in the circumferential direction by the elastic member 128, and the tooth portion 126a and the tooth portion 127a are shifted in the circumferential direction by an amount of meshing clearance.

[Operation] In the above configuration, the gear 124 in FIG. 3 is used to transmit power from the electric motor to the input shaft.
When rotates clockwise, its teeth 124a
The tooth surface 124c of the main gear 126 contacts the tooth surface 126b of the tooth portion 126a of the main gear 126 to transmit torque.

On the other hand, when the gear 124 rotates counterclockwise, the tooth surface 124c of the tooth portion 124a first rotates to the tooth surface 124c of the tooth portion 127a of the auxiliary gear 127.
Touch b and press it. When the transmitted torque exceeds a predetermined value, the auxiliary gear 127 slightly rotates clockwise against the biasing force of the elastic member 128, and the phases of the main gear 126 and the auxiliary gear 127 match. From now on, the tooth surface 12 of the tooth portion 124a of the gear 124 will be explained.
4b to the tooth surface 12 of the tooth portion 126a of the main gear 126
Torque will be transmitted to 6c.

That is, within a predetermined transmission torque during power transmission, the tooth surfaces 124b and 1 of the tooth portion 124a of the gear 124
24c is the tooth surface 1 of the tooth portion 126a of the main gear 126.
26b and the tooth surface 1 of the tooth portion 127a of the auxiliary gear 127
27b, and there is no gap in the circumferential direction between the opposing tooth surfaces.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. In the following embodiment, the present invention is applied to a rack and pinion type steering device for illustrative purposes.

1 to 3 show a first embodiment of the present invention.

A rotational input torque is applied to one end of the input shaft 104 from a handle (not shown). The input shaft 104 is a hollow rod-shaped member, into which a torsion bar 108 is inserted and whose tip end is press-fitted onto the input shaft 104.

The other end of the torsion bar 108 is connected to the input shaft 104.
A pinion shaft 10 as an output shaft extending on an extension of
6 and is fixed with a pin 105. Input shaft 104, torsion bar 10
8. The pinion shaft 106 extends in a straight line within the housing 101, is rotatably supported by a bearing 107, and is sealed by a seal 109. Bearing 107 is preloaded by cap 113. The input shaft 104 is rotated by a torsion bar 10.
8 to the pinion shaft 106, and the torsional displacement of the torsion bar 108 at this time is detected by the detector 114 on the input shaft 104. The detector 114 may be any device that can mechanically or electrically detect the torsional displacement of the torsion bar 108, and a conventionally known detection device can be used.

A pinion shaft 106 is provided with a pinion and meshes with a rack of a rack shaft 110 extending intersectingly. The engagement between the pinion shaft 106 and the rack shaft 110 is maintained by a pressing device 111.

An electric motor 102 is fixed to the housing 101, and its output shaft is connected to a first shaft 116 via a clutch mechanism 103. The first shaft 116 is rotatably supported within the housing 101 by bearings 115 at both ends. A gear mechanism 112 is disposed between the first shaft 116 and the pinion shaft 106, and a gear mechanism 112 is arranged between the first shaft 116 and the pinion shaft 106.
It is transmitted to 06. The gear mechanism 112 includes a first gear 125 on the pinion shaft 106 and a first shaft 116.
a fourth gear 120 on the top, and a second gear 12 on the intermediate shaft 118 between the pinion shaft 106 and the first shaft 116
4. It consists of a third gear 122. 4th gear 1
20 is formed integrally with the first shaft 116 and rotates together with the first shaft 116. The fourth gear 120 meshes with a third gear 122 that is keyed to the intermediate shaft 118 and transmits power. The intermediate shaft 11 is rotatably supported at both ends by bearings 117, and rotates together with the third gear 122 and the second gear 124. The second gear 124 is formed integrally with the intermediate shaft 118 and meshes with the first gear 125 to transmit the output of the electric motor 102 to the first gear 125. The first to fourth gears 125, 124, 122, 120 transmit the output of the electric motor 102 to the pinion shaft 106 at a predetermined reduction ratio.
The gear ratio is set to transmit the

The first gear 125 mainly includes a main gear part 126 fixed to the pinion shaft 106 for receiving torque from the second gear 124, and an auxiliary gear part 127 for eliminating backlash between the second gear 124.
It consists of The auxiliary gear part 127 has the same diameter as the main gear part 126, and the shape of the tooth part 127a,
The dimensions correspond to the shape and dimensions of the teeth 126a, and the number of teeth 126a is the same as the number of teeth 127a. The auxiliary gear part 127 is coaxially and rotatably disposed on the main gear part 126, and is located in a state where it rotates relative to the main gear part 126, as will be described later. Further, the main gear section 126 and the auxiliary gear section 127 are biased in a relative rotation direction by two leaf springs 128 arranged between them. Therefore,
One tooth surface 124c of the tooth portion 124a of the gear 124
can come into contact with the tooth surface 126b of the tooth portion 126a of the main gear 126, and the other tooth surface 124b can contact the tooth surface 126b of the tooth portion 126a of the main gear 126.
It can come into contact with the tooth surface 126c of the tooth portion 126a of No. 26 or the tooth surface 127c of the tooth portion 127a of the auxiliary gear 127. The leaf spring 128 spans between a pin 129 implanted in the auxiliary gear portion 127 and a pin 130 implanted in the main gear portion 126, and its intermediate portion curves along the annular protrusion of the main gear portion 126. It is arranged as follows. Therefore, the curved leaf spring 12
8 transmits the elastic force to the main gear part 126 via the pin 130.
and the auxiliary gear section 127. In FIG. 2, the two-dot chain line shows the state of the leaf spring 128 before attachment, and the solid line shows the state of the leaf spring 128 when the pin 129 and
30 and stops when it hits the pin 131 implanted in the auxiliary gear part 127, and the broken line shows the state where the second gear 124 is engaged with the first gear 125 and the auxiliary gear part 127 is connected to the main gear part 126. On the other hand, it shows a state in which elastic force is generated between the main gear part 126 and the auxiliary gear part 127 by relative displacement.

When in the state shown by the broken line in FIG. 2, the first gear 125 and the second gear 124 are in the meshing state shown in FIG. 3. That is, the main gear part 126 is attached to one of the tooth surfaces of the second gear 124, and the auxiliary gear part 127 is attached to one of the tooth surfaces of the second gear 124.
is pressed against the other tooth surface. Therefore, the first gear 125 and the second gear 124 can mesh without backlash.

In the electric power steering system having the above configuration, when a rotational input is applied to the input shaft 104 from the steering wheel, the detector 114 detects the input torque and sends an electric signal corresponding to the input torque to a control device (not shown). . The control device controls the drive of the electric motor 102 based on information such as input torque and vehicle speed. The rotation of the electric motor 102 is caused by the clutch mechanism 103, the fourth gear 120, the third gear 122, and the second gear 124.
is transmitted to the first gear 125 via.

In FIG. 3, when the second gear 124 rotates clockwise, it pushes the main gear portion 126 of the first gear 125, causing the first gear 125 to rotate counterclockwise.
On the other hand, when the second gear 124 rotates counterclockwise, it pushes the auxiliary gear part 127 that comes into contact with the tooth surface of the second gear 124 on the side opposite to the main gear part 126. When a torque exceeding the elastic force of the leaf spring 128 applied to the auxiliary gear part 127 via the pin 129 is transmitted to the auxiliary gear part 127, the auxiliary gear part 127 is displaced relative to the main gear part 126, and finally The second gear 124 transmits torque via the main gear part 126.

Next, FIGS. 4 to 6 for the second embodiment of the present invention
This will be explained with reference to the figures. The second embodiment differs from the first embodiment only in the first gear 225, and the other configurations are the same, so only the first gear 225 will be described.

The first gear 225 consists of a main gear part 226 and an auxiliary gear part 227, and a coil spring 228 is disposed between the two to provide elastic force. Main gear part 226
is fixed to the pinion shaft 106 and rotates integrally with the pinion shaft 106. The auxiliary gear part 227 is coaxially and rotatably fitted into an annular protrusion provided on the main gear part 226.

The coil spring 228 is stretched around pins 229 and 230 implanted in the main gear part 226 and the auxiliary gear part 227, respectively. The outside of the coil spring 228 is held down by a plate 231 and a ring 232
Fixed by

As also shown in FIG. 3, the first gear 225 is pressed by the elastic force of the coil spring 228 against the tooth surface of the second gear in which the main gear part 226 and the auxiliary gear part 227 are meshed, and both are located at relatively displaced positions. In the case of the second embodiment, the first
The operation is similar to that of the embodiment.

Next, FIGS. 7 and 8 show a third embodiment of the present invention, and the difference from the first embodiment is that the first gear 325
Only.

The first gear 325 consists of a main gear part 326 and an auxiliary gear part 327, and both parts 326 and 327 are coaxially fitted onto the pinion shaft 106. Main gear part 3
The auxiliary gear part 327 is fixed to the main gear part 326 by a pin 329 and is bonded to the main gear part 326 at the contact portion. As shown in FIG. 7, the auxiliary gear part 327 has a rib part 328 extending in the radial direction and is made of an elastic material.

As shown in FIG.
It is meshed with the gear 124 and generates elastic force due to the spring action of the rib portion 328.

9 and 10 show the fourth embodiment of the present invention,
Again, only the first gear 425 is different from the other embodiments.

The first gear 425 consists of a main gear part 426 that is keyed to the pinion shaft 106 and rotates integrally with the pinion shaft 106, and an auxiliary gear part 427 that is coaxially and rotatably fitted into the annular protrusion of the main gear part 426. . The auxiliary gear portion 427 has two recesses 424 extending in the radial direction, and a coil spring 428 and a ball 429 are disposed within the recesses 424 . The ball 429 is inserted into a V-shaped groove 430 provided in the annular protrusion of the main gear portion 426.
It is pressed inward by a coil spring 428. Therefore, as shown in FIG. 3, the first gear 425 is
When the main gear part 426 and the auxiliary gear part 427 are relatively displaced and meshed with the second gear 124, a coil spring 428 is generated between the main gear part 426 and the auxiliary gear part 427.
is given an elastic force.

FIG. 11 shows a part of a fifth embodiment of the present invention, in which the first gear 525 and the second gear 524 are constructed of helical gears.

The first gear 525 is formed so that the main gear portion 526 and the auxiliary gear portion 527 are connected by a pin 529 and can move only in the axial direction.
The auxiliary gear portion 526 and the auxiliary gear portion 527 are disposed with a predetermined gap therebetween, and at this time, the teeth of both portions 526 and 527 are in a state of relative rotational displacement as shown in FIG.

When the second gear 524 rotates clockwise, the main gear section 526 directly transmits torque, but when the second gear 524 rotates counterclockwise, the auxiliary gear section 527 first begins to rotate clockwise. After the tooth trace of the auxiliary gear part 527 matches the tooth trace of the main gear part 526, it becomes an integrated helical gear, and torque is transmitted by both parts 526 and 527.

Although the embodiment in which the present invention is applied to a rack and pinion type steering device has been described above, the present invention is not limited thereto, and can be applied to ball circulation type and other steering devices.

Further, the shaft for outputting the rotational output of the electric motor may be a shaft related to a steered wheel, such as a rack shaft.

Furthermore, the present invention is applicable not only between the first gear and the second gear, but also between the third gear and the fourth gear.

Since the auxiliary gear part does not need to receive large torque, it can be formed from a lightweight material such as resin.

[Effect of idea]

The present invention provides a gear mechanism for an electric power auxiliary device in which either the gear on the electric motor side or the gear on the input shaft that meshes with the gear is connected to the main gear fixed to the shaft on the electric motor side or the input shaft. The main gear and the auxiliary gear have approximately the same shape as the main gear and are loosely fitted on the same axis. energized. As a result, the teeth of the gear are elastically sandwiched from both sides by the teeth of the main gear and the teeth of the auxiliary gear.
Since there is no gap between opposing tooth surfaces, no crushing occurs when rotating in either direction.

The electric power auxiliary device of the present invention solves the problems of the prior art with a simple structure and can operate reliably.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of the first embodiment of the present invention;
The figure is a sectional view taken along the line A-A in Figure 1, Figure 3 is an enlarged partial view of the meshing portion of the first gear and second gear of the first embodiment, and Figure 4 is a cross-sectional view of the meshing part of the first gear and the second gear of the first embodiment. FIG. 5 is a sectional view taken along the line B-B in FIG. 4, FIG. 6 is a sectional view taken along the line C-C in FIG. 4, and FIG. 7 is a front view of the third embodiment. 8 is a sectional view taken along line D-D in FIG. 7, FIG. 9 is a front view of the first gear of the fourth embodiment, and FIG. 10 is a sectional view taken along line DD in FIG. 9. 11 is a partial side sectional view of the fifth embodiment, and FIG. 12 is a side sectional view of a conventional electric power steering device. Explanation of symbols of main parts, 102... Electric motor, 104... Input shaft, 106... Output shaft (pinion shaft), 114... Detector, 112... Gear means, 125, 225, 325, 425, 525 …
...gear, 126, 226, 326, 426, 52
6...Main gear part, 127, 227, 327, 42
7,527... Auxiliary gear section, 124,524...
gear.

Claims (1)

[Claims for Utility Model Registration] An output shaft that rotates when rotational torque is input, a torque detector that detects the rotational torque applied to the input shaft, and a predetermined driving force based on the detection result of the torque detector. and a gear means for transmitting the driving force of the electric motor to the output shaft, the gear consisting of at least a gear fixed to the electric motor side and a gear fixed to the output shaft. an electric power auxiliary device comprising a gear means having a group of gears, at least one pair of gears meshing with each other in the gear means, one of which is composed of a main gear and an auxiliary gear, and the auxiliary gear is connected to the main gear. The main gear and the auxiliary gear are loosely fitted coaxially and have teeth having the same dimensions and the same tooth shape as the main gear in the diametrical direction, and the main gear and the auxiliary gear are relatively biased with a predetermined biasing force by an elastic member. When the pair of gears mesh, the main gear and the auxiliary gear mesh with each other with a displacement in the circumferential direction by a meshing clearance due to the biasing force of the elastic member. Device.