JPH0899643A - Power steering - Google Patents

Abstract

PURPOSE: To shorten the axial dimension of a screw shaft so as to reduce the size and weight of a device by forming such structure that part of gears forming a first gear group and part of gears forming a second gear group are made common and that the common gears include a driven gear corotated coaxially at least with a nut. CONSTITUTION: When a steering wheel 15 is rotated for steering operation, an input shaft 3 is rotated, and the rotation of the input shaft 3 is transmitted to a ball nut 2 through a first gear group 4. A ball screw shaft 1 is moved in the width direction of a vehicle by the rotation of the ball nut 2 to steer the vehicle. A motor 5 is rotatory-driven according to steering resistance at the time of steering operation, and the rotation of the motor 5 is transmitted to the ball nut 2 through a second gear group 6 so as to exert the steering assist force for moving the ball screw shaft l in the width direction of the vehicle by the rotation of the ball nut 2. A driven gear 35 is included as a common gear in the first gear group 4 and the second gear group 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system for steering a vehicle by moving a screw shaft by rotating a nut.

[0002]

2. Description of the Related Art A power steering device disclosed in Japanese Patent Application Laid-Open No. 1-233164 includes a ball screw shaft arranged so that an axial center direction extends along a vehicle width direction, and a ball nut meshing with the ball screw shaft. An input shaft that rotates by a steering operation, a first gear group that transmits the rotation of the input shaft to the ball nut, an electric actuator that rotates according to steering resistance, and the rotation of the actuator to the ball nut And a second gear group. The rotation by the steering operation of the input shaft is transmitted to the ball nut through the first gear group, and the rotation of the ball nut moves the ball screw shaft in the width direction of the vehicle to steer the vehicle. Further, the actuator rotates according to the steering resistance, and the rotation is transmitted to the ball nut through the second gear group, and the rotation of the ball nut acts as a steering assist force for moving the screw shaft in the vehicle width direction.

[0003]

SUMMARY OF THE INVENTION In the above conventional configuration,
The first gear group and the second gear group are separate and independent, and are provided at intervals along the axial direction of the ball screw shaft. Therefore, the axial dimension of the ball screw shaft is large, which becomes a factor of increasing the size and weight of the device.

The first gear group is composed of a first bevel gear that rotates together with the ball nut coaxially with it, and a second bevel gear that meshes with the first bevel gear, and the input shaft is connected to the second bevel gear. ing. Therefore, the input shaft can only be positioned at a position centered on the axis of the ball screw shaft, and the axis of the input shaft must pass through the axis of the ball screw shaft, which limits the layout and reduces the design. Freedom is hindered.

Further, since the first gear group generally needs to accelerate the rotation of the input shaft and transmit it to the ball nut,
The second bevel gear becomes large. On the other hand, the second gear group generally has a large reduction gear because it is necessary to reduce the rotation of the actuator and transmit the rotation to the ball nut. These large bevel gears and reduction gears increase the manufacturing cost and increase the weight.

It is an object of the present invention to provide a power steering device which can solve the above problems.

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to a screw shaft arranged so that its axial direction extends along the width direction of a vehicle, a nut meshing with the screw shaft, and an input shaft which rotates by a steering operation. A first gear group that transmits the rotation of the input shaft to the nut, an actuator that rotates according to operating conditions, and a second gear group that transmits the rotation of the actuator to the nut, and a screw that rotates the nut. In the power steering device in which the vehicle is steered by the movement of the shaft in the width direction of the vehicle, some of the gears of the first gear group and some of the gears of the second gear group are common. It is characterized in that the common gear includes at least a driven gear that rotates together with the nut coaxially therewith.

A gear common to the first gear group and the second gear group is the driven gear and a counter gear which meshes with the driven gear and rotates about an axis parallel to the axis of the nut. Gears unique to the first gear group are a first intermediate gear that rotates together with the counter gear coaxially with the counter gear, and a second intermediate gear that meshes with the first intermediate gear.
The input shaft is connected to the second intermediate gear, and a gear unique to the second gear group is a pinion gear that meshes with the counter gear and is connected to the output shaft of the actuator, and the driven gear and the pinion gear. Is preferably smaller in diameter than the counter gear.

[0009]

According to the structure and the effect of the present invention, the rotation of the input shaft by the steering operation is transmitted to the nut through the first gear group, and the rotation of the nut causes the ball screw shaft to move in the vehicle width direction. And the vehicle is steered. The actuator rotates in accordance with the driving condition during steering operation, and the rotation is transmitted to the nut through the second gear group, and the rotation of the nut applies a steering assist force that moves the screw shaft in the vehicle width direction. To do.

Since the gear common to the first gear group and the second gear group includes the driven gear that rotates together with the nut coaxially therewith, the first gear group and the second gear group are independent of each other. Compared with the conventional configuration, the axial dimension of the screw shaft can be shortened, and the size and weight of the device can be reduced.

A second intermediate gear connected to the input shaft meshes with a first intermediate gear that meshes with the driven gear and that rotates coaxially with a counter gear that rotates about an axis parallel to the axis of the nut. As a result, the input shaft can be positioned not only at a position centered on the shaft center of the screw shaft but also at a position centered on the shaft center of the counter gear. As a result, the restriction on the layout of the input shaft becomes smaller than that in the conventional example, and the degree of freedom in design is increased.

By making the diameter of the counter gear larger than the diameter of the driven gear, the rotation of the input shaft can be accelerated and transmitted to the nut without increasing the diameter of the intermediate gear. When the pinion gear connected to the output shaft of the actuator meshes with the counter gear, the counter gear can be made larger in diameter than the pinion gear and the rotation of the actuator can be decelerated and transmitted to the nut. As a result, the counter gear can be used both as a gear for increasing the speed of rotation of the input shaft and a gear for reducing the speed of rotation of the output shaft of the actuator, thereby reducing manufacturing costs and weight.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

A forklift power steering system P shown in FIG. 1 includes a ball screw shaft 1 arranged so that its axial direction extends along the vehicle width direction, a ball nut 2 meshing with the ball screw shaft 1, and an input shaft. 3, a first gear group 4 for transmitting the rotation of the input shaft 3 to the ball nut 2, and an electric motor (actuator) 5
And a second gear group 6 that transmits the rotation of the motor 5 to the ball nut 2. A rear wheel 10 is connected to each end of the ball screw shaft 1 via a ball joint 7, a tie rod 8 and a knuckle arm 9. As shown in FIG. 5, the power steering device P is supported by the rear axle 19 that supports the rear wheel 10 via the kingpin 18. The input shaft 3 has a universal joint 11, a connecting shaft 12, a gear mechanism 13 and a handle shaft 1.
The steering wheel 15 is connected via the steering wheel 4, so that the steering wheel 15 is rotated to rotate the input shaft 3. A torque sensor 16 for detecting a torque corresponding to the steering resistance based on the twist of the handle shaft 14,
A controller 17 that controls the motor 5 according to the output of the torque sensor 16 is provided, and
The motor 5 is rotationally driven according to the steering resistance.

As shown in FIG. 2, the power steering device P has a housing 20 fixed to the rear axle 19, and the ball screw shaft 1 moves axially in the housing 20 via bushes 21 and 22. Each end of the ball screw shaft 1 that is movably supported and protrudes from the housing 20 has an elastic cover 2
Covered by 3, 24. Through holes 25 and 26 are formed in the housing 20 to allow air to flow between the inside of one elastic cover 23 and the inside of the other elastic cover 24. Each ball joint 7 has a case 7a and a connecting member 7b, and a male screw portion 7a 'formed on the case 7a is screwed onto each end of the ball screw shaft 1 and fixed by a lock nut 7c. The connecting member 7b is engaged with the case 7a so that only relative rotation of the ball screw shaft 1 about its axis is restricted.
This prevents the ball screw shaft 1 from rotating with the rotation of the ball nut 2.

The ball nut 2 is attached to the housing 2
It is rotatably supported inside bearings 0 and 0 through bearings 30 and 31, and meshes with the ball screw shaft 1 through balls 32.

The first gear group 4 includes the ball nut 2
As shown in FIG. 3, a driven gear 35 that rotates together with the driven gear 35, a counter gear 36 that meshes with the driven gear 35, a first intermediate gear 37 that rotates together with the counter gear 36 coaxially with the counter gear 36, The second intermediate gear 38 meshes with the first intermediate gear 37, and the second intermediate gear 38 is connected to the input shaft 3. The driven gear 35 is a spur gear having a smaller diameter than the counter gear 36,
It is integrated with the outer periphery of the ball nut 2 inside the housing 20. The counter gear 36 is a spur gear, and is integrated with a support shaft 42 that is rotatably supported in the housing 20 via bearings 40 and 41 about an axis parallel to the axis of the ball nut 2. The first intermediate gear 37 is a bevel gear, and its supporting shaft 42
Is integrally provided at one end of the. The second intermediate gear 3
A bevel gear 8 is integrally provided at one end of the input shaft 3 and rotates together with the input shaft 3 coaxially. The input shaft 3 has a bearing 43 in the housing 20,
It is supported via 44, and as shown in FIGS. 3 and 4, rotates about an axis parallel to a plane perpendicular to the axis of the counter gear 36.

As shown in FIG. 2, the second gear group 6 is
The driven gear 35, the counter gear 36, and a pinion gear 52 connected to the output shaft 5a of the motor 5 via a coupling 50 are provided. Figure 3
As also shown, the pinion gear 52 is a spur gear having a smaller diameter than the counter gear 36, and is rotatably supported by the housing 20 via bearings 53 and 54 about an axis parallel to the rotation axis of the ball nut 2. It The motor 5 is connected to the housing 20.

According to the above structure, when the steering wheel 15 is rotated to perform the steering operation, the input shaft 3 rotates, and the rotation of the input shaft 3 is transmitted to the ball nut 2 via the first gear group 4.
The rotation of the ball nut 2 moves the ball screw shaft 1 in the width direction of the vehicle to steer the vehicle. The motor 5 is rotationally driven according to the steering resistance during steering operation, and the rotation is transmitted to the ball nut 2 via the second gear group 6, and the rotation of the ball nut 2 causes the ball screw shaft 1 to move to the width of the vehicle. A steering assist force to move in the direction acts.

Since the driven gear 35 is included as a gear common to the first gear group 4 and the second gear group 6, the structure of the conventional example in which the first gear group and the second gear group are independent of each other. Compared with, the axial dimension of the ball screw shaft 1 can be shortened, and the size and weight of the device can be reduced. Also,
The ball nut 2 meshes with the driven gear 35.
The second intermediate gear 38 connected to the input shaft 3 is meshed with the first intermediate gear 37 that rotates coaxially with the counter gear 36 that rotates about the axis parallel to the input shaft 3 Can be positioned not only at a position centered on the axis of the ball screw shaft 1, but also at a position centered on the center of the counter gear 36. That is, the degree of freedom in design is increased as compared with the conventional case where the axis of the input shaft needs to pass through the axis of the ball screw shaft. Since the diameter of the counter gear 36 is larger than the diameter of the driven gear 35, the first intermediate gear 3
The rotation of the input shaft 3 can be accelerated and transmitted to the ball nut 2 without increasing the diameter of the motor 7, and the diameter of the counter gear 36 is larger than the diameter of the pinion gear 52. Can be decelerated and transmitted to the ball nut 2. As a result, the manufacturing cost can be reduced as compared with the conventional example in which a large gear for increasing the rotation speed of the input shaft and a large gear for reducing the rotation speed of the output shaft of the actuator are individually required. The weight can be reduced.

FIG. 6A shows a ball joint 60 of a first modification of the ball joint 7 of the above embodiment,
The connecting member 61, the pair of support members 62 and 63, the support spring 64, and the holding member 65 of the one support member 62.
And a fixing screw 66. The outer periphery of the one end 61a of the connecting member 61 is spherical and is inserted into the cavity 1a formed at one end of the ball screw shaft 1. Further, the connecting member 61 engages with the peripheral edge of the opening of the hollow portion 1a so that only relative rotation of the ball screw shaft 1 about its axial center is restricted, whereby the ball screw shaft 1 is rotated by the rotation of the ball nut 2. The rotation is prevented. The outer peripheral surfaces of the pair of support members 62 and 63 are cylindrical surfaces, and one end surface thereof is a spherical surface that receives the one end portion 61 a of the connecting member 61. The holding member 65 has a cylindrical shape, the inner peripheral surface of which receives the outer peripheral surface of the one support member 62, and the outer peripheral surface of which is received by the inner peripheral surface of the hollow portion 1a. The support spring 64 is compressed between the inner surface of the cavity 1 a and the one support member 62. The fixing screw 66 is screwed into the hollow portion 1a, and the pair of supporting members 62 and 63 and the one end portion 61a of the connecting member 61 are sandwiched by the spring 64. In addition,
The opening of the cavity 1a is covered with a cover 68. Thereby, the ball screw shaft 1 of the connecting member 61
The relative rotational position of the ball screw shaft 1 with respect to the axis center is fixed at a fixed position by the assembly to the ball screw shaft 1.

FIG. 6B shows a ball joint 60 'of a second modified example of the ball joint 7 of the above embodiment. The difference from the ball joint 60 of the first modified example is that the support spring 64 and the hollow portion are different. The point is that a spacer 70 is interposed between the spacer 1 and the inner surface of 1a, and the fixing screw 66 is locked by a lock nut 71. The spacer 70
The tread and toe-in of the vehicle can be adjusted by changing the thickness of the.

The present invention is not limited to the above embodiment. For example, although the ball screw shaft 1 and the ball nut 2 are used in the above embodiment, the type is not particularly limited as long as it is the screw shaft and the nut. Further, although the present invention is applied to the power steering device for steering the rear wheels of the forklift in the above-described embodiment, the vehicle to which the invention is applied is not particularly limited, and the power steering device for steering the front wheels can also be applied. Further, bevel gears are used as the first intermediate gear 37 and the second intermediate gear 38, but the type of gear is not particularly limited, and for example, a worm gear and a worm wheel may be used. Further, although the motor 5 is rotationally driven in accordance with the steering resistance, it may be rotationally driven in accordance with another driving condition such as a steering angle that is a reference for applying a steering assist force. Further, the actuator is not limited to the electric motor 5.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a configuration of a power steering device according to an embodiment of the present invention.

FIG. 2 is a front sectional view of the power steering device.

FIG. 3 is a plan sectional view of a main part of the power steering device.

FIG. 4 is a side view of the power steering device.

FIG. 5 is an explanatory diagram showing how the power steering device is mounted on a vehicle.

6A and 6B are sectional views of a ball joint of the power steering device, wherein (1) is a sectional view of a first modified example, and (2) is a sectional view of a second modified example.

[Explanation of symbols]

 1 Ball Screw Shaft 2 Ball Nut 3 Input Shaft 4 First Gear Group 5 Motor (Actuator) 6 Second Gear Group 35 Driven Gear 36 Counter Gear 37 First Intermediate Gear 38 Second Intermediate Gear 52 Pinion Gear

Claims (2)

[Claims] 1. A screw shaft arranged so that an axial direction extends along a width direction of a vehicle, a nut meshing with the screw shaft, an input shaft rotated by a steering operation, and rotation of the input shaft by the nut. And a second gear group that transmits the rotation of the actuator to the nut, the screw shaft being moved in the vehicle width direction by the rotation of the nut. In a power steering device in which a vehicle is steered by movement, a part of gears forming a first gear group and a part of gears forming a second gear group are common, and at least the common gear has A power steering device that includes a driven gear that rotates together with the nut. 2. The gear common to the first gear group and the second gear group is the driven gear and a counter gear that meshes with the driven gear and rotates about an axis parallel to the axis of the nut. Gears unique to the first gear group are a first intermediate gear that rotates together with the counter gear coaxially with the counter gear, and a second intermediate gear that meshes with the first intermediate gear.
The input shaft is connected to the second intermediate gear, and a gear unique to the second gear group is a pinion gear that meshes with the counter gear and is connected to the output shaft of the actuator, and the driven gear and the pinion gear. 2. The power steering device according to claim 1, wherein is smaller in diameter than the counter gear.