JP3607371B2 - Reducer for electric power steering system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a structure of an electric motor speed reducer provided in an electric power steering apparatus.
[0002]
[Prior art]
In the electric power steering apparatus, the magnitude of the input torque input from the steering wheel is detected by a torque sensor, and steering assist by the electric motor is performed according to the detected magnitude and direction of the input torque. In general, the electric motor is provided with a reduction gear in order to reduce its rotation and output it as a large force. As this reduction gear, for example, there is one shown in FIG.
That is, a speed reducer 3 is provided to decelerate the rotation of the motor shaft 2 of the electric motor 1, and the rotation decelerated by the speed reducer 3 is output by the pinion shaft 4. A pinion gear 4 a is formed on the pinion shaft 4 and meshed with the rack gear 5. Therefore, when the pinion shaft 4 rotates, the rack shaft 6 is moved by the gears 4a and 5 and the wheels are steered via a steering link and a knuckle arm (not shown).
[0003]
The case 7 is of an open type at both ends, and an electric motor is provided in one of the openings. In the case 7, the motor shaft 2 of the electric motor 1, the speed reducer 3 that decelerates the rotation of the motor shaft 2, and the pinion shaft 4 that outputs the decelerated rotation are arranged coaxially.
The tip of the pinion shaft 4 is rotatably supported inside the case 7 by a ball bearing 8. A nut 9 is provided at the further tip of the pinion shaft 4 to position the inner race member of the ball bearing 8 in the axial direction. In addition, a plug 11 is provided at the front end opening of the case 7, and the outer race member of the ball bearing 8 is positioned at the end of the plug 11.
In this way, the position of the pinion shaft 4 is determined by the ball bearing 8 supported by the nut 9 and the plug 11.
[0004]
A carrier 10 provided integrally with the pinion shaft 4 is rotatably supported in the case 7 by a ball bearing 12. Further, an oil seal 13 is provided adjacent to the ball bearing 12.
The speed reducer thus assembled is assembled by inserting the pinion shaft 4, the speed reducer 3, and the motor shaft 2 into the case 7 from one opening (upper opening in the figure) of the case. The tip of the inserted pinion shaft 4 is exposed at the tip opening of the case 7. As described above, the ball bearing 8 is assembled to the exposed portion and the nut 9 is tightened. The plug 11 is plugged.
[0005]
[Problems to be solved by the invention]
However, according to the conventional example shown in FIG. 4, in the assembling work, there are a direction in which the electric motor 1 and the pinion shaft 4 are assembled, and a direction in which the ball bearing 8 is assembled to the tip of the pinion shaft 4 and the nut 9 is tightened. Were in opposite directions.
Thus, assembly work must be performed from two directions, and the entire case 7 must be reversed during the work. For this reason, the assembly work is difficult to perform, and the variation in work time has become large. This assembly work has become a bottleneck process for the entire electric power steering apparatus.
Further, a large force is required to tighten the nut 9 and the plug 11.
Furthermore, in order to prevent intrusion of water or the like, it is necessary to apply a seal bond to a joint portion between the case 7 and the plug 11 and perform tightening. For this reason, there is a problem that the seal bond adheres to an operator's hand, an assembling jig or the like, and the working environment is deteriorated.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a speed reducer for an electric power steering apparatus that facilitates assembling work of the speed reducer and can improve the work environment.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a case, a ring gear incorporated in the case in a state in which rotation is restricted, and the center of the ring gear, which rotates as the motor shaft of the electric motor rotates. A pinion shaft comprising a sun gear, a planet gear that rotates by rotation of the sun gear and revolves around the sun gear along the ring gear, a carrier that rotates by revolution of the planet gear, and a pinion shaft provided integrally with the carrier This is based on the assumption that the reduction gear of the electric power steering apparatus in which the pinion gear provided in is engaged with the rack gear of the rack shaft with which the wheels are linked.
In the first invention, a sliding bearing that rotatably supports the tip of the pinion shaft and a carrier that rotates integrally with the pinion shaft are rotated in a case having an opening for mounting the electric motor and having a bottomed end. A rolling bearing for freely supporting, an inner support member attached to the carrier for supporting the inner race member of the rolling bearing from the front end side of the case, and a carrier for supporting the inner race member of the rolling bearing from the opening side of the case Steps formed in the case to support the outer race member of the rolling bearing from the front end side of the case, and a case inner peripheral surface to support the outer race member of the rolling bearing from the opening side of the case It is characterized in that it has an outer support member.
The second invention is characterized in that, in the first invention, the rotation of the ring gear is restricted by the pin, and the pin is inserted obliquely with respect to the outer peripheral surface of the ring gear.
[0007]
[Action]
In the first invention, a rolling bearing is provided on a carrier integrated with the pinion shaft when assembled. That is, one end of the inner race member of the rolling bearing is supported by a retaining ring as an inner support member attached to the carrier, and at the same time, the other end is supported by a stepped portion formed on the carrier.
In this way, the rolling bearing is attached to the pinion shaft, and is inserted into a case having a bottomed end after being in a sub-assy state. At this time, the tip of the pinion shaft is rotatably supported by a bush as a slide bearing.
Further, when inserted into the case in the sub-assy state, the outer race member of the rolling bearing is supported by a step portion formed on the inner side of the case from the front end side of the case. And the outer race member of a rolling bearing is supported by the seal holder as an outer side support member press-fitted from the opening side of the case.
As described above, the pinion shaft is positioned by the rolling bearing, and the position of the rolling bearing can be determined by the inner support member, the outer support member, and the stepped portion. All these members can be assembled from the opening side of the case.
In the second invention, since the pin is inserted obliquely with respect to the outer peripheral surface of the ring gear, the total length of the pin can be shortened.
[0008]
【Example】
An embodiment of the present invention will be described below with reference to FIGS.
[Description of reducer itself]
First, the reduction gear itself will be described.
The reduction gear 3 mainly includes an A-row side gear mechanism 15 located on the electric motor 1 side, a B-row side gear mechanism 16 located on the pinion shaft 4 side, and a ring gear installed on the inner peripheral side of the case 20. 17 and 18.
The A row side gear mechanism 15 meshes with the A row side sun gear 19 fixed to the motor shaft 2 of the electric motor 1 and the A row side sun gear 19 and also with the ring gear 17. The A row side planet gear 21 that revolves around the A row side sun gear 19 while rotating by the rotational force from the A row, and the A row side planet gear 21 are connected to the A row side planet gear 21 via a slidable bush 22. The A row side carrier 23 that allows the rotation of the gear 21 and rotates along with the revolution of the A row side planet gear 21 is configured.
[0009]
Further, the B row side gear mechanism 16 meshes with both the B row side sun gear 24 fixed to the A row side carrier 23 and both the B row side sun gear 24 and the ring gear 18, and rotates from the B row side sun gear 24. The B-row planet gear 25 is rotated by force and revolves around the B-row sun gear 24 along the ring gear 18, and is connected to the B-row planet gear 25 via a slidable bush 26. The B row side planet gear 25 is allowed to rotate, and the B row side carrier 27 rotates as the B row side planet gear 25 revolves.
The pinion shaft 4 is integrally provided on the B row carrier 27. The A row side carrier 23 and the pinion shaft 4 are supported so as to be relatively rotatable via a slidable bush (not shown).
[0010]
The tip of the pinion shaft 4 is rotatably supported by a bush 29, and the B row side carrier 27 side is rotatably supported by a ball bearing 12. An oil seal 13 that prevents fluid leakage is provided on the ball bearing 12 side.
Now, when torque is input from a steering wheel (not shown), distortion occurs. This distortion is detected by a distortion sensor (not shown) and transmitted to the controller. This controller rotates the electric motor 1 in accordance with a signal from the strain sensor.
When the electric motor 1 rotates in this way, the A-row-side sun gear 19 rotates with the motor shaft 2. The rotation of the A row side sun gear 19 causes the A row side planet gear 21 to rotate and revolve around the A row side sun gear 19 along the ring gear 17.
[0011]
When the A-row side planet gear 21 revolves, the A-row side carrier 23 also rotates, so that the B-row side sun gear 24 rotates, and the B-row side planet gear 25 rotates to the ring gear 18 along with the rotation. And revolves around the B row sun gear 24. The B-row side carrier 27, that is, the pinion shaft 4 is rotated by the revolution of the B-row side planet carrier 25.
By such an action, the rotation on the electric motor 1 side is transmitted to the pinion shaft 4 side while being decelerated.
The ring gear is divided into an A row side ring gear 17 and a B row side ring gear 18. The rotation of the B row side ring gear 18 is restricted by a plurality of pins 28. On the other hand, the rotation of the A-row side ring gear 17 is restricted by the friction torque slip mechanism 31.
The friction type torque slip mechanism 31 includes a box 32 formed by projecting a part of the case 20 radially outwardly, and is disposed in the box 32, and an arcuate surface on the inside thereof is arranged on the A-row side ring gear 17. A pad 33 that is in contact with the outer peripheral surface of the spring, a spring 34 that is housed in the box 32 and biases the pad 33 toward the ring gear 17, and an adjustment screw 35 that adjusts the spring force of the spring 34. It is configured.
[0012]
According to the friction type silk slip mechanism 31, the rotation of the A-row side ring gear 17 is normally restricted.
For example, it is assumed that the motor shaft 2 is stuck due to a failure of the electric motor 1 or the like. At this time, the A-row side sun gear 19 cannot move, but if the handle is cut, the A-row side ring gear 17 can slip and rotate against friction based on the urging force of the spring 34, thus preventing the occurrence of a mechanical lock state. it can.
[0013]
[Arrangement structure of each part in case 20]
Now, a structure in which each part constituting such a reduction gear is housed and arranged in the case 20 will be described.
In this embodiment, the case 20 has an opening for mounting the electric motor 1 at the base end and is formed in a bottomed cylindrical shape with the tip closed, and the diameter inside the case 20 becomes smaller toward the tip. The tip is bag-shaped.
In the case 20, the motor shaft 2 of the electric motor 1, the speed reducer 3, and the pinion shaft 4 are arranged coaxially as in the conventional example.
The distal end portion of the pinion shaft 4 is inserted into the distal end portion that becomes the bottomed end of the case 20 and is rotatably supported by a bush 29 as a sliding bearing. That is, the ball bearing 8, the nut 9, and the plug 11 (see FIG. 4) provided in the conventional example are eliminated. And even if these are abolished, the pinion gear 4 can be rotated by the bush 8, and the axial positioning performed by the conventional nut 9 and plug 11 is also performed by a retaining ring 36 and step portions 37 and 38 described later. , And the seal holder 39 or the like.
[0014]
In other words, the outer periphery of the B row side carrier 27 integrated with the pinion shaft 4 is rotatably supported inside the case 20 by the ball bearing 12 as a rolling bearing. The ball bearing 12 has existed conventionally.
And in order to support this ball bearing 12 from the front end side (lower side in the figure) of the case 20, a stepped portion 38 and a retaining ring 36 as an inner support member are provided. That is, a cut 42 is formed on the outer peripheral surface of the B row carrier 27, and a retaining ring 36 is fitted into the cut 42. The retaining ring 36 supports the inner race member 12 a of the ball bearing 12. Further, a stepped portion 38 is formed inside the case 20 to support the outer race member 12b of the ball bearing 12.
[0015]
On the other hand, in order to support the ball bearing 12 from the opening side (upper side in the figure) of the case 20, a step portion 37 and a seal holder 39 as an outer support member are provided. That is, a stepped portion 37 is formed on the B row side carrier 27 to support the inner race member 12 a of the ball bearing 12. Further, the seal holder 39 is press-fitted into the inner peripheral surface of the case 20, and the outer race member 12b of the ball bearing 12 is supported by bringing the lower surface of the seal holder 39 into contact with the upper surface of the outer race member 12b. The cross section of the seal holder 39 has an inverted T shape (see FIG. 3), and the seal holder 39 is attached so that the oil seal 13 is put on the tip of the T shape.
A pin 28 that restricts the rotation of the B row side ring gear 18 is provided obliquely with respect to the outer peripheral surface of the B row side ring gear 18. That is, the lower end of the pin 28 is inserted obliquely downward with respect to the hole provided inside the case 20, and the upper end is inserted obliquely upward with respect to the slit 44 (see FIG. 2) formed on the outer periphery of the ring gear 18. . By using the pins 28 at an angle in this way, the overall length of the pins 28 can be shortened, and the case 20 can be downsized.
[0016]
[Reduction gear assembly work]
Next, the assembling work of the speed reducer in this embodiment will be described.
The pinion shaft 4 and the B row side gear mechanism 16 are inserted into the case 20. At this time, the ball bearing 12 is attached to the outer periphery of the B row side carrier 27. That is, the inner race member 12a of the ball bearing 12 is supported by the stepped portion 37 and the retaining ring 36 of the carrier 27, and is inserted into the case 20 in a sub-assy state. Then, the outer race member 12 b of the ball bearing 12 is brought into contact with the step portion 38 and the tip of the pinion shaft 4 is supported by the bush 26.
Thereafter, the seal holder 39 is press-fitted, and the seal body 13 is attached. Further, the ring gear 18 is assembled through the pin 28 fixed obliquely to the case 20, and then the A-row side gear mechanism 15 is assembled.
[0017]
[Effect of Example]
According to this embodiment, the following effects are obtained.
That is, the pinion shaft 4 is supported by the ball bearing 12 and the bush 29, and the axial positioning is performed by the stepped portions 37 and 38, the retaining ring 36, and the like. For this reason, the ball bearing 8 which has conventionally determined the position of the pinion shaft can be changed to the bush 29, and accordingly, the nut 9 and the plug 11 can be eliminated. Therefore, it is only necessary to work from one direction, and it is not necessary to reverse the entire case 20 during the assembling work. Moreover, since the work content becomes easy, the variation in work time can be reduced.
Furthermore, since the plug 11 is abolished, it is no longer necessary to apply the seal 11 of the connecting portion between the plug 11 and the case, and the seal bond adheres to the operator's hand, assembly jig, etc., and the working environment is deteriorated. Can be avoided.
Further, by using the pins 28 at an angle, the length of the pins 28 can be shortened, and the case 20 can be downsized.
[0018]
【The invention's effect】
According to the speed reducer of the electric power steering apparatus of the first aspect, the position of the pinion shaft is determined by the rolling bearing that supports the carrier that rotates integrally with the pinion shaft.
Therefore, it is only necessary to support the tip of the pinion shaft with a slide bearing, and the work of tightening a nut or a plug from the tip of the case becomes unnecessary.
This eliminates the need to reverse the entire speed reducer during the assembly operation.
Furthermore, since the plug is abolished, a seal bond applied to the joint between the plug and the case becomes unnecessary, and the seal bond does not adhere to the operator's hand or the assembling jig, and the working environment can be improved.
According to the second invention, since the pins can be shortened, the size of the case can be reduced accordingly.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of the present invention.
2 is a partial cross-sectional view taken along line II-II in FIG.
FIG. 3 is an enlarged view of a part III in FIG. 1;
FIG. 4 is a cross-sectional view showing a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric motor 2 Motor shaft 3 Reduction gear 4 Pinion gears 8 and 12 Ball bearing 13 Seal main body 20 Case 29 Bush 36 Retaining ring 37 and 38 Step part 39 Seal holder 12a Inner race member 12b Outer race member

Claims (2)

A case, a ring gear incorporated in the case with restricted rotation, a sun gear that is located at the center of the ring gear and that rotates as the motor shaft of the electric motor rotates, and rotates by the rotation of the sun gear, and the ring gear A rack shaft in which a planet gear that revolves around the sun gear along the axis, a carrier that rotates by the revolution of the planet gear, and a pinion shaft that is integrated with the carrier, and the pinion gear that is provided on the pinion shaft are linked to the wheels. In a reduction gear of an electric power steering device meshed with a rack gear, a sliding bearing that rotatably supports the tip of a pinion shaft in a case having an opening for mounting an electric motor and having a bottomed end, and a pinion shaft, Supports a rotating carrier that rotates together And an inner support member attached to the carrier for supporting the inner race member of the rolling bearing from the front end side of the case, and a carrier for supporting the inner race member of the rolling bearing from the opening side of the case. Stepped portion, stepped portion formed in the case to support the outer race member of the rolling bearing from the front end side of the case, and outer support provided on the inner peripheral surface of the case to support the outer race member of the rolling bearing from the opening side of the case And a reduction gear for an electric power steering apparatus. 2. The speed reducer for an electric power steering apparatus according to claim 1, wherein the rotation of the ring gear is restricted by a pin, and the pin is inserted obliquely with respect to the outer peripheral surface of the ring gear.

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