JPH0710012A - Transmission for power steering - Google Patents

Abstract

PURPOSE:To provide a transmission for power steering which is highly effective in power transmission, achieves a speed reduction rate required for power steering, conforms to non-reciprocal transmission structure, and also does not cause delay in rotation angle. CONSTITUTION:A sun gear comprises the first gear 5 which is provided in a fixed shaft 4 and a second gear 7 comprising its teeth increased by one arranged coaxially side by side, and a planetary gear comprises the pinion gear 12 which is attached to a carrier 11 which can rotate around the sun gear meshed with the first gear and the second gear. The second gear is fixed to an output shaft 6 which transmit steering force to a steering system, and the shaft 9 of a motor 10 is fixed to the carrier 11 to rotate the carrier 11 by the drive force of the motor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering transmission for a vehicle such as an automobile, and more particularly to a transmission suitable for electric power steering.

[0002]

2. Description of the Related Art Four-wheel steering has been actively developed in order to reduce the rotational movement of a vehicle body at high speed to improve stability, or to improve small turning performance at low speed.
Further, this four-wheel steering mechanism also needs a non-reversible power transmission mechanism that prevents the tire from changing its direction when a force is applied to the tire from the road surface. As a conventional non-reciprocal power transmission mechanism, it is common to utilize the characteristics of the meshing mechanism of the worm gear and the worm wheel and transmit the force in the forward direction but not the force in the reverse direction. . However, this mechanism has a transmission efficiency of 20-
Since it is as low as 30%, there is a drawback that the motor becomes large when using electric power steering. In order to solve this drawback, a device using a coil spring clutch and a planetary gear has been proposed, as described in, for example, Japanese Patent Application Laid-Open No. 1-257672. This device is fitted to the steering shaft with a predetermined frictional force, forms torque transmission engagement portions at both ends, and has an input in the coil winding direction with respect to both torque transmission engagement portions. Then, the winding around the steering shaft is loosened and the fastening state is released, and when an input is made in the opposite direction, the winding is strengthened and the fastening state is established. This configuration improves the transmission efficiency.

[0003]

However, the above-mentioned conventional device has a reduction ratio of 1/10 even if the transmission efficiency is high.
However, a large reduction ratio required for power steering, for example, about 1/30 cannot be achieved, and further reduction mechanism is required to achieve this reduction ratio. Also, since the tightening of the coil spring is used,
There is a delay of about 20 degrees in rotation angle from the rotation of the input shaft to the rotation of the output shaft, and a separate control mechanism is required to eliminate this delay. Further, since the coil spring receives the locking force only by the tensile stress of the coil spring, the durability is insufficient.

[0004]

Therefore, the present invention has been proposed in view of the above, and a first gear fixedly provided on the housing side and a second gear having a different number of teeth from the first gear. Are arranged coaxially adjacent to each other and both gears are sun gears, and a pinion gear mounted on a carrier rotatable around the sun gear is meshed with the first gear and the second gear to form the pinion gear. A planetary gear that revolves while rotating on its axis, the second gear is fixed to an output shaft that transmits a steering force to a steering system, a drive source is connected to the carrier, and the carrier is rotated by the drive force of the drive source. It was done like this.

[0005]

When the carrier is rotated, the pinion gear moves to the first position.
The pinion gear revolves around the gear and the second gear, and the pinion gear meshes with the fixed first gear to rotate on its axis. When the pinion gear revolves while revolving, the second gear also meshes with this pinion gear, and the second gear and the first gear have different numbers of teeth. Therefore, the second gear revolves around the revolution of the pinion gear and its rotation. And rotate by the difference in the number of teeth. Therefore, the driving force of the driving source can be transmitted to the output shaft with a large reduction ratio. Even if the output shaft tries to rotate due to an external force due to road surface resistance or the like, the second gear fixed to the output shaft meshes with the pinion gear, and this pinion gear meshes with the fixed first gear to bring the stopped state into a stopped state. I am maintaining. Therefore, even if the second gear tries to rotate due to an external force, the second gear is prevented from rotating by the pinion gear. Therefore, the second gear and the output shaft cannot rotate unless the pinion gear makes a planetary motion due to the rotation of the carrier, and the second gear and the output shaft serve as a nonreciprocal mechanism. Moreover, it is possible to surely stop at a rotation angle of about the backlash of the gear.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. All of the embodiments of the power steering transmission 1 shown in FIGS. 1 to 4 are for rear wheels of four-wheel steering. Figure 1
The first embodiment shown in FIG. 2 has a substantially bottomed cylindrical housing case 2 having an opening at one end and a fixed shaft opening at the other end, and a screw 3 from the outside in the opening of the housing case 2.
Hollow fixed shaft 4 and housing case 2 fixed by
Formed on the tip of the fixed shaft 4 protruding into the room
A gear 5 and an output shaft 6 inserted in the hollow portion of the fixed shaft 4,
The second gear 7 that is fixed to the tip of the output shaft 6 that protrudes into the room and is coaxially adjacent to the first gear 5, and the shaft 9 is inserted through the central opening of the lid member 8 that covers the one end opening of the housing case 2. In this state, the motor 10 as a drive source mounted on the housing case 2, the carrier 11 mounted on the shaft 9 of the motor 10, and the carrier 11 is axially mounted and meshes with the first gear 5 and the second gear 7. It comprises a pinion gear 12 and the like.

The first gear 5 functions as a sun gear together with the second gear 7, and is formed by cutting the end surface portion of the fixed shaft 4 with its center aligned with the center of the fixed shaft 4. The number of teeth is set to 29z. The first gear 5 may be separately prepared and fixed to the fixed shaft 4.

The center of the second gear 7 coincides with the centers of the fixed shaft 4 and the first gear 5, and the outer diameter is the same as that of the first gear 5, but the number of teeth is only one than that of the first gear 5. It is set to a large 30z. As described above, the first gear 5 and the second gear 7 in the present embodiment are dislocation gears having the same meshing center distance but different in the number of teeth by one and are always in correct meshing even if the pinion gear 12 makes a planetary motion. You can keep the state.

The carrier 11 is a bottomed cylindrical body having a circular hollow portion at the center for accommodating the first gear 5 and the second gear 7, and the bottom side is opened by a bearing 13 provided in the lid member 8. The side is supported by a bearing 14 provided at the base end of the fixed shaft 4, and the shaft 9 of the motor 10 is fixed to the center of the bottom portion.
It is configured to rotate coaxially with the gears 5 and 7.
Then, the thick wall portion of the carrier 11 is provided with a mounting cavity portion 15 penetrating from the outer periphery to the circular cavity portion, and the pinion gear 1 functioning as a planetary gear is provided in the mounting cavity portion 15.
2 is attached rotatably by a shaft 16 and a pinion gear 1
The two teeth project into the circular cavity. Therefore, when the carrier 11 is mounted with the first and second gears 5 and 7 accommodated in the circular space, the pinion gear 12 meshes with the first gear 5 and the second gear 7.

The teeth of the pinion gear 12 are set so as to mesh smoothly with the teeth of the first gear 5 and the teeth of the second gear 7, and the number of teeth is set to 14z.

A steering gear 17 is fixed to an end of the output shaft 6 protruding from the housing case 2, and the steering gear 17 meshes with a rack gear connected to a rear wheel steering link.

In the transmission 1 having the above structure,
When the motor 10 is operated and the carrier 11 is rotated, the pinion gear 12 revolves around the first gear 5 and the second gear 7, and the pinion gear 12 meshes with the fixed first gear 5. The meshing with the first gear 5 causes rotation of the body. That is, the pinion gear 12 functions as a planetary gear that revolves while rotating on its axis.

When the pinion gear 12 revolves around its own axis, the second gear 7 is also meshed with the pinion gear 12, and the second gear 7 has one more tooth than the first gear 5. Therefore, the second gear 7 is rotated by the revolution and rotation of the pinion gear 12 by the difference in the number of teeth by the number of teeth.
Will rotate in the same direction as. That is, in the present embodiment, when the motor 10 makes one rotation of the carrier 11, the second gear 7 rotates in the same rotation direction as the carrier 11 by 1/30, in other words, 1/30 of the rotation of the motor 10. The second gear 7 and the output shaft 6 rotate at a reduction ratio of 30.

When the output shaft 6 rotates at a reduction ratio of 1/30 of that of the motor 10, the steering system for the rear wheels can be driven with a torque of about 30 times to steer the rear wheels, and the spur gears mesh with each other. Since it is transmitted, the transmission efficiency is high. Therefore, a sufficient steering driving force can be obtained even with the small motor 10.

When the number of teeth of the first gear 5 is set to 28z and the number of teeth of the second gear 7 is set to 30z, the output shaft 6 rotates in the same direction as the input of the motor 10 at a reduction ratio of 1/15. Further, the number of teeth of the first gear 5 is 30 z, and the number of teeth of the second gear 7 is 2
When set to 9z, the output shaft 6 rotates in the opposite direction to the input of the motor 10 at a reduction ratio of 1/29.

Next, the irreversibility will be described. When a force to steer the rear wheels is applied due to road surface resistance or the like, this force is transmitted to the steering gear 17 via the steering system and tries to rotate the output shaft 6. However, even if the output shaft 6 tries to rotate due to an external force, the second gear 7 fixed to the output shaft 6 meshes with the pinion gear 12, and the pinion gear 12 meshes with the first gear 5 in the fixed state. It keeps stopped. Therefore, the second gear 7
Is prevented from rotating by the pinion gear 12. Therefore, the second gear 7 and the output shaft 6 cannot rotate unless the pinion gear 12 makes a planetary motion due to the rotation of the carrier 11. That is, this speed reducer is realized as a non-reciprocal mechanism. Moreover, it is possible to surely stop at a rotation angle of about the backlash of the gear.

Next, a second embodiment shown in FIGS. 3 and 4 will be described. This transmission 1 is obtained by adding an auxiliary pinion gear 12 'to the opposite side of the pinion gear 12 to the configuration of the transmission 1 shown in the first embodiment. In addition, the same reference numerals are given to common configurations.

Two mounting cavities 15 penetrating from the outer periphery to the circular vacancy are opened in the wall portion of the carrier 11 by changing the phase by 180 degrees (on opposite sides of the center), and one mounting vacancy portion 15a is formed. The pinion gear 12 is rotatably mounted on the shaft 16 so that the teeth of the pinion gear 12 project into the circular cavity, and the auxiliary pinion gear 12 'is rotatably mounted on the other mounting cavity 15b by the shaft 16'. The teeth of the gear 12 'are projected into the circular cavity.

The auxiliary pinion gear 12 'is formed by being divided into a tooth 12a meshing with the first gear 5 and a tooth 12b meshing with the second gear 7, and the phase between one of the divided teeth and the other tooth. Are formed so as to correspond to the phases of the meshed gears. In this embodiment, the number of teeth of the first gear 5 is 29.
z, the number of teeth of the second gear 7 is 30 z, so the pinion gear 1
At the position where 2 meshes, the tooth crests of the first gear 5 and the tooth crests of the second gear 7 are located on the same line in the same phase, but at the position where the auxiliary pinion gear 12 'meshes, The crests of both gears are not in the same phase, but the crests of the teeth of the first gear 5 and the second gear
The valleys of the teeth of the gear 7 are located on a straight line. Therefore, the teeth of the auxiliary pinion gear 12 'are formed such that the crests of one of the divided teeth and the troughs of the other tooth are located on a straight line. The number of teeth of the auxiliary pinion gear 12 'is 14z, which is the same as that of the pinion gear 12.

Therefore, when the carrier 11 is mounted with the first and second gears 5 and 7 housed in the circular cavity,
The pinion gear 12 meshes with the first gear 5 and the second gear 7, and the auxiliary pinion gear 12 ′ has the first gear 5 ′ on the opposite side.
The gear 5 and the second gear 7 mesh with each other without any trouble.

In the transmission 1 having such a structure,
When the carrier 11 is rotated by the operation of the motor 10,
The pinion gear 12 and the auxiliary pinion gear 12 'are the first
It revolves around the gear 5 and the second gear 7,
Moreover, since both pinion gears 12 and 12 'mesh with the first gear 5 in the fixed state, the pinion gears 12 and 12' are rotated by meshing with the first gear 5. That is, the auxiliary pinion gear 12 '
Also functions as a planetary gear that revolves around its own axis.

When both pinion gears 12 and 12 'revolve while revolving, the second gear 7 rotates 1/30 in the same rotation direction as the carrier 11 as in the above embodiment.
In this case, the output of the motor 10 is transmitted through the two pinion gears, the pinion gear 12 and the auxiliary pinion gear 12 ', so that the durability is improved and the load on the rotating carrier 11 is improved. Since it acts on the object, it is well balanced and can suppress vibration.

In this embodiment, even if the output shaft 6 tries to rotate by an external force, the second gear 7 fixed to the output shaft 6 meshes with both the pinion gears 12 and 12 ', and the both pinion gears are engaged. Since the first and second gears 12 and 12 'are meshed with the first gear 5 in the fixed state, the second gear 7 is the double pinion gear 1
The rotation is blocked by 2, 12 '. Therefore, it is realized as a non-reciprocal mechanism, and it is possible to surely stop at a rotation angle of about the backlash of the gear.

Further, in this embodiment, one auxiliary pinion gear 12 'is provided in addition to the pinion gear 12, but the number of the auxiliary pinion gears 12' is not limited to this, and the position is also the pinion. It is not limited to the opposite side of the gear 12.

The third embodiment shown in FIG. 5 is the second embodiment described above.
The transmission 1 of the embodiment is used for front wheels.
The structure of the housing case is slightly different from that of the above embodiment, but the basic structure is the same. In addition, common configurations are denoted by the same reference numerals to avoid duplication of description.
Incidentally, 23 and 24 are bearings, and 25 is an oil seal, which are for ensuring a meshing center distance between the steering shaft 18 and the transmission.

In the case of the front wheels, an electromagnetic clutch 19 is provided in the middle of a steering shaft 18 which is rotated by a driver to steer the front wheels, and the steering shaft 18 and the transmission according to the present invention are provided via the electromagnetic clutch 19. Connect with 1. Specifically, the output side of the electromagnetic clutch 19 is connected to the steering shaft 18, and the electromagnetic clutch 1
The first intermediate gear 20 attached to the input side of 9 and the second intermediate gear 21 attached to the output shaft 6 of the transmission 1 are meshed with each other. In this embodiment, the number of teeth of the first gear 5 is 28z,
The number of teeth of the second gear 7 is set to 30z, the number of teeth of the pinion gear 12 and the auxiliary pinion gear 12 'is set to 14z, and
The number of teeth of the first intermediate gear 20 is set to 34z, and the number of teeth of the second intermediate gear 21 is set to 17z.

When the carrier 11 is rotated by the operation of the motor 10 while the electromagnetic clutch 19 is engaged in the power steering having the above-described structure, both pinion gears 12, 1 are rotated.
2'revolves while rotating. Both pinion gears 12, 1
A second gear 7 is also meshed with 2 ', and the second gear 7 should rotate in the same direction as the carrier 11 by the difference in the number of teeth due to the revolution and rotation of both pinion gears 12 and 12'. become. That is, in this embodiment, the second gear 7 rotates in the same rotation direction as the carrier 11 by 1/15, and the output shaft 6 rotates at a reduction ratio of 1/15 with respect to the rotation of the motor 10.

When the output shaft 6 rotates at a speed reduction ratio of 1/15 of the motor 10, the second intermediate gear 21 and the first intermediate gear 20 mesh with each other and the power is transmitted to the steering shaft 18 at a speed reduction ratio of 1/2. . Therefore, the steering shaft 18 rotates at a reduction ratio of 1/30 of the motor 10,
The steering force of the driver is assisted by this rotational force. It should be noted that in the present embodiment, since only the steering wheel operating force of the driver is assisted, the motor 10 may have a lower output than that for the rear wheels.

When the driver needs the assistance of the steering wheel operating force, for example, when the vehicle is traveling at a low speed or a medium speed such as entering a garage, the electromagnetic clutch 19 is engaged to function as a power steering. However, when driving at high speed, the steering wheel is lighter to operate, so no auxiliary force is required. Therefore, when the auxiliary force is not required, the electromagnetic clutch 19 is turned off to provide an appropriate steering wheel operation resistance force to improve safety.

The carrier 11 of the present invention is not limited to the above-mentioned thick cup shape, but can support the pinion gears 12 and 12 'in a rotatable state, and has a required strength. Any shape may be used as long as it can be secured. The drive source is preferably the electric motor 10 because of its small size and simple structure, but a hydraulic motor or the like may be used if necessary.

[0031]

As described above, according to the present invention, transmission is performed by meshing spur gears without using a worm gear, so that transmission efficiency is high and the reduction ratio required for power steering is simple. Can be achieved. Further, since the first reversibly fixed gear is engaged with the pinion gear to form a specific reversible mechanism, it is possible to reliably stop at a rotation angle of about backlash. Furthermore, the transmission according to the present invention does not receive a force only by the tensile stress of the coil spring, and thus has excellent durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a power steering transmission according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a second embodiment in which an auxiliary pinion gear is provided in addition to the pinion gear.

FIG. 4 is a sectional view taken along line BB of FIG.

FIG. 5 is a sectional view of a main part of an embodiment in which a steering shaft for front wheels is connected via an electromagnetic clutch.

[Explanation of symbols]

 1 Power Steering Transmission 2 Housing Case 4 Fixed Shaft 5 First Gear 6 Output Shaft 7 Second Gear 8 Housing Case Lid 9 Motor Shaft 10 Motor 11 Carrier 12 Pinion Gear 12 'Auxiliary Pinion Gear 17 Steering Gear 18 Steering shaft 19 Electromagnetic clutch 20 First intermediate gear 21 Second intermediate gear

Claims (3)

[Claims] 1. A first gear, which is fixed to the housing side, and a second gear, the number of teeth of which is different from that of the first gear, are arranged coaxially next to each other, and both gears are sun gears. A planetary gear that revolves while rotating the pinion gear by rotating a pinion gear mounted on a carrier that can rotate around the sun gear with the first gear and the second gear, and the second gear serves as a steering system. A power steering transmission, characterized in that it is fixed to an output shaft for transmitting a steering force, and a drive source is connected to the carrier so that the carrier is rotated by the drive force of the drive source. 2. The power steering transmission according to claim 1, wherein the number of teeth of the first gear is set smaller than the number of teeth of the second gear. 3. A carrier is provided with an auxiliary pinion gear,
A tooth for meshing the tooth of the auxiliary pinion gear with the first gear and a second tooth
The transmission for power steering according to claim 1 or 2, wherein the gear is formed by being divided into teeth that mesh with the gear and the phase is different corresponding to the phase of the gear that meshes.