JPH061122U - Rear-wheel steering system for 4-wheel steering vehicle - Google Patents

Abstract

(57) [Summary] [Purpose] Return the rear wheel steering rod to the neutral position and hold it. Reduce the torque when returning the steering wheel to the neutral position after steering both the front and rear wheels. [Composition] On the peripheral surface of the rear wheel steering rod 12 that steers the rear wheels by rotating around the axis and moving in the axial direction,
The flat portion 30 is formed. On the peripheral surface of the rear wheel steering rod 12, a twisted cam-shaped portion 31 having a predetermined length is integrally formed so that the ratio of the movement distance in the axial direction and the rotation angle around the axis is constant. A biasing member (32) that abuts on the cam-shaped portion (31) is provided so that it does not move in the left-right direction but moves in a direction orthogonal to the axis of the rear wheel steering rod (12). Springs 34, 35 for urging the biasing member 32 toward the cam-shaped portion 31 are arranged. Cam portion 31
Part of it is on the flat part 30 and the rest is on the rear wheel steering rod 12
It lies on a cylindrical surface centered on the axis of. When the rotation angle of the rear wheel steering rod 12 from the neutral position is within a predetermined range, the biasing member 32 is brought into contact with the portion of the cam-shaped portion 31 on the flat portion 30.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rear wheel steering system for a four-wheel steering vehicle.

In this specification, the left side of FIG. 7 is the front, the right side is the rear, the lower side of the same figure is the left, and the upper side is the right.

[0003]

[Prior art]

 As a rear-wheel steering system for a four-wheel steering vehicle, the input shaft is supported by a housing so as to rotate around an axis extending in the front-rear direction, and is rotated during steering of the front wheels, and the left-right direction is rotated during rotation of the input shaft. BACKGROUND ART There is known one provided with a rear wheel steering rod which is rotated around an extending axis and is supported by a housing so as to be movable in the axial direction and which steers the rear wheel by moving in the axial direction.

In such a rear wheel steering system, the rear wheel steering rod is held in the neutral position in order to improve the running stability when an external force is applied to the rear wheels when the front wheels are in the neutral position. There is a need. In addition, after steering both front and rear wheels, it is necessary to restore the rear wheel steering rod to the neutral position in order to reduce the torque for returning the steering wheel to the neutral position.

Therefore, conventionally, there is known one in which a device for holding the rear wheel steering rod at the neutral position is provided between the housing and the input shaft (see Japanese Utility Model Laid-Open No. 3-38279).

This conventional device is shown in FIGS. In FIG. 8, a tubular body (51) is fitted and fixed around an input shaft (50) extending in the front-rear direction of the rear wheel steering system. An annular groove (52) is formed on the entire circumference of the cylindrical body (51). In addition, a biasing member (53) that moves in a direction orthogonal to the axis of the input shaft (50) is provided in the housing (not shown) of the rear wheel steering device so as not to move in the axial direction of the input shaft (50). Has been. The urging member (53) is rotatably attached to the roller support member (54) and the roller support member (54) that moves in a direction orthogonal to the axis of the input shaft (50), and the tubular body (51). It is composed of a roller (55) fitted in the annular groove (52) of (1), and is constantly urged toward the input shaft (50) by the compression coil spring (56). When the rotation angle from the neutral position of the input shaft (50) on the bottom surface of the annular groove (52) is within the predetermined range, the part (52a) where the roller (55) contacts holds the input shaft (50) at the neutral position. The urging member (53) is configured to receive the force to act. Further, a recess (52b) into which a part of the roller (55) is fitted is provided in a portion of the bottom surface of the annular groove (52) where the input shaft (50) is in the neutral position and where the roller (55) contacts. Has been formed.

As shown in FIG. 9, when the front wheels are steered and the input shaft (50) rotates around the axis in the direction of the arrow (A), if the rotation angle is within the predetermined range, the annular groove ( By the action of the portion (52a) of 52), the biasing member (53) is moved in the direction away from the input shaft (50) and the spring (56) is compressed. As a result, the elastic force of the spring (56) imparts a rotational force to the input shaft (50) in a direction opposite to the rotational direction, and the input shaft (50) is rotated in this direction to return to the original neutral position. Thus, the input shaft (50) is held in the neutral position.

[0008]

[Problems to be solved by the device]

 However, the above-mentioned rear wheel steering system has the following problems. That is, as shown in FIG. 10, when the front wheels are steered so that the input shaft (50) rotates in the direction of the arrow (A) for almost one lap, the biasing member (53) is located at the portion (52a). It contacts the part on the opposite side of 9. As a result, the elastic force of the spring (56) further acts to rotate the input shaft (50) in the same direction. Therefore, there is a problem in that the input shaft (50) cannot be returned to the neutral position and a large torque is required to return the steering wheel to the neutral position.

An object of the present invention is to provide a rear wheel steering system for a four-wheel steering vehicle that solves the above problems.

[0010]

A rear-wheel steering system for a four-wheel steering vehicle according to the present invention rotates around an input shaft that is rotated during front-wheel steering and an axis that extends in the left-right direction when the input shaft rotates. A rear wheel steering device for a four-wheel steering vehicle, comprising: a rear wheel steering rod that is supported by a housing so as to be movable in the axial direction and that steers the rear wheels by moving in the axial direction. On the circumferential surface of the rod, there is a twisted cam-like part that is fixedly provided over a specified length so that the ratio of the moving distance in the axial direction and the rotation angle around the axis is constant. The housing includes a biasing member that is provided in the housing so as to move in a direction orthogonal to the axis of the wheel steering rod, and that abuts against the cam-shaped portion, and a spring that biases the biasing member toward the cam-shaped portion. Cage, cam-shaped part Of these, when the rotation angle from the neutral position of the rear wheel steering rod is within a predetermined range, the portion where the biasing member abuts receives the force for returning and holding the rear wheel steering rod to the neutral position from the biasing member. In addition to being shaped, the remaining part is located on a cylindrical surface centered on the axis of the rear wheel steering rod.

[0011]

[Action]

 Due to the rotation of the input shaft, the rear wheel steering rod is rotated around the axis extending in the left-right direction and is moved in the axial direction, and the rear wheel is steered by moving in the axial direction.

When the rear wheel steering rod rotates about the axis, and the rotation angle from the neutral position is within the predetermined range, the contact portion of the biasing member with the cam-shaped portion causes the rear wheel steering rod to be neutral. Since the portion is shaped so as to receive the force for returning to the position and holding it from the biasing member, the rotational force in the opposite direction to the above rotational direction is applied to the rear wheel steering rod by the force of the spring. Further, when the rotation angle of the rear wheel steering rod is out of the predetermined range, the contact portion of the biasing member with the cam portion is located on the cylindrical surface centered on the axis of the rear wheel steering rod in the cam portion. Since it is a part that is made to rotate, no rotational force is applied to the rear wheel steering rod.

Therefore, only when the rotation angle when the rear wheel steering rod is rotated from the neutral position is within the predetermined range, the rotational force in the opposite direction to the rotational direction is applied to the rear wheel steering rod, and the rear wheel steering rod is rotated. Returns to the neutral position.

[0014]

【Example】

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

FIG. 7 shows a schematic configuration of a four-wheel steering vehicle equipped with the rear wheel steering device of the present invention. The rear wheel steering system (1) is connected to the front wheel steering system (3) by a connecting shaft (2) extending in the front-rear direction. The connecting shaft (2) is composed of multiple shafts connected by a universal joint.The pinion (5) of the pinion shaft (4) at the front end meshes with the rack rod (6) of the front wheel steering system (3). There is. Both ends of the rack rod (6) of the front wheel steering device (3) are connected to the knuckle arms (8) of the left and right front wheels (7) through tie rods (9). Then, by rotating the steering wheel (10), the rack bar (6) is moved in the left-right direction, and the front wheels (7) are steered. Also, the rack rod (6) is moved in the left-right direction to rotate the connecting shaft (2) by an amount corresponding thereto, and this rotation is transmitted to the input shaft (11) of the rear wheel steering system (1).

The rear wheel steering device (1) includes a rear wheel steering rod (12) corresponding to the rack rod (6) of the front wheel steering device (3). The rear wheel steering rod (12) is supported by a housing (13) fixed to the vehicle body so as to extend in the left-right direction, move in the axial direction (left-right direction), and rotate around the axis. . Both ends of the rear wheel steering rod (12) are connected to the knuckle arms (15) of the left and right rear wheels (14) via tie rods (16). The rear wheels (14) are steered by moving in the left-right direction.

As shown in FIG. 1, the input shaft (11) of the rear wheel steering system (1) extends in the front-rear direction, and two angular ball bearings (17) are provided so that they can rotate but do not move in the front-rear direction. It is supported by the housing (13) via (18), and the front portion thereof projects from the housing (13). A large bevel gear (19) is integrally formed at the rear end of the input shaft (11).

At the left end of the housing (13), a sleeve (21) extending in the left-right direction is supported via a double-row angular contact ball bearing (22) so as to be rotatable about its axis. A rear wheel steering rod (12) is connected to the rear wheel (21) via a spline (23) so as to be movable in the axial direction but not to rotate relative to each other. A small bevel gear (24) that meshes with the large bevel gear (19) is integrally formed at the right end of the sleeve (21), and the rotation of the input shaft (11) is controlled by both bevel gears (19) (24). Is transmitted to the sleeve (21) via the shaft, whereby the rear wheel steering rod (12) is rotated. The backlash between the large bevel gear (19) and the small bevel gear (24) is adjusted by a double-row angular contact ball bearing (22). A guide (25) is fixedly provided at the right end of the housing (13), and the rear wheel steering rod (12) can move in the axial direction and rotate about the axis at the guide (25). Is supported as.

A male screw portion (12a) extending over a predetermined length is formed in the middle of the length of the rear wheel steering rod (12), and a large number of balls (26) are attached to the male screw portion (12a). The ball nut (27) is screwed through. A cylindrical projection (27a) protruding forward is integrally formed with the ball nut (27), and a spherical bush (28) is fitted on the projection (27a) so as to be slidable in the axial direction. ing. The spherical bush (28) is fitted in a hole (11a) formed in the rear end surface of the input shaft (11) so as to be rotatable and tiltable in an arbitrary direction. The axis of the protrusion (27a) is inclined with respect to the axis of the input shaft (11).

The configuration up to this point is known (see, for example, Japanese Patent Laid-Open No. 3-32982), and although detailed description is omitted, the rear wheel (14) is steered as follows.

When the front shaft (7) is steered to rotate the input shaft (11), the large bevel gear (19) and the small bevel gear (24) are meshed with each other to rotate the sleeve (21). The rear wheel steering rod (12) rotates. As a result, the male screw portion (12a) and the ball nut (27) work to move the rear wheel steering rod (12) in the axial direction and steer the rear wheel (14). Since the projection (27a) formed integrally with the ball nut (27) is inclined to the axis of the input shaft (11), the steering angle of the front wheels (7) is small and the input shaft (11) When the rotation amount is small, the rear wheels (14) are not steered, and when the rotation amount is large, the rear wheels (14) are steered in the opposite phase to the front wheels (7), and the front wheels (7) As the steering angle increases, the steering angle of the rear wheels (14) also increases. Therefore, the rear wheels (14) are not steered at high speed when the front wheels (7) have a small steering angle. In addition, the rear wheel (14) is steered when the vehicle is traveling at a low speed such as when the front wheel (7) is steered at a large angle, such as when entering the garage, so that the maneuverability is improved.

As shown in FIGS. 2 and 3, the rear wheel steering rod (12) has a cylindrical shaft shape, and the peripheral surface of the portion at the right end in the housing (13) is cut off tangentially. A flat portion (30) is formed. The length of the rear wheel steering rod (12) in the axial direction of the flat portion (30) depends on the tangential ends of the flat portion (30) and the axis line of the rear wheel steering rod (12). It is determined by taking into consideration the distance to move to the left and right when an angle (X) formed by two straight lines connecting (O) is made. The angle (X) is, for example, the maximum rotation angle predicted when the rear wheel steering rod (12) is rotated by an external force applied to steer the rear wheel (14) in the neutral position. It is decided based on the standard. Further, the flat portion (30) faces rearward when the rear wheel steering rod (12) is in the neutral position. As shown by the curved line in FIG. 3, a twisted cam-shaped portion (31) is integrally formed on the peripheral surface of the rear wheel steering rod (12). The cam-shaped part (31) is located on the flat part (30) and the second part is located on the cylindrical surface centered on the axis (O) of the rear wheel steering rod (12). It consists of part (31b). In FIG. 3, the rear wheel steering rod (12) is extended in the axial direction to show the cam-shaped portion (31) in an exaggerated manner than the actual shape, but in reality, it corresponds to the external thread (12a). It is shaped like this.

As shown in FIG. 1, at a position corresponding to the flat portion (30) of the rear wheel steering rod (12), the housing (13) has a cylindrical portion rearward of the rear wheel steering rod (12). The portion (13a) is formed, and the biasing member (32) is arranged therein so as to be movable in the front-rear direction. The rear end opening of the cylindrical part (13a) is closed by a plug (33) screwed into the cylindrical part (13a), and the plug (33) and the biasing member (32) are formed on the rear end of the outward facing opening. Two compression coil springs (34) (35) are arranged between the flange (32a) and the compression coil springs (34) (35). The biasing member (32) is biased forward by the compression coil springs (34) and (35) toward the axis of the rear wheel steering rod (12).

As shown in FIG. 2, when the rear wheel steering rod (12) is in the neutral position, the biasing member (32) is located in the flat portion (30) of the cam-shaped portion (31). It is in contact with the center of (31a). At this time, the biasing force of the springs (34) (35) does not act on the rear wheel steering rod (12) as a moment around the axis (O), and the rear wheel steering rod (12) is not rotated. Not granted.

In such a neutral position, for example, when an external force is applied to the rear wheels (14) to steer the rear wheels (14), the rear wheel steering rod (12) moves in the axial direction and the axial line (O). Rotate around. The rotation angle at this time is within the range of the angle (X), and as shown in FIG. 4, the urging member (32) has the first portion (3) on the flat portion (30) of the cam-shaped portion (31). It deviates from the center of 1a). Therefore, the urging force of the springs (34) (35) acts on the rear wheel steering rod (12) as a moment about the axis (O), and the rear wheel steering rod (12) is opposed to the above rotation direction. Directional rotational force is applied. As a result, the rear wheel steering rod (12) is returned to and held in the neutral position.

When the steering angle of the front wheels (7) becomes large and the rear wheels (14) are steered in the opposite phase, and the rotation angle of the rear wheel steering rods (12) becomes larger than the angle (X), as shown in FIG. And as shown in FIG. 6, thereafter, the biasing member (32) abuts the second portion (31b) of the cam-shaped portion (31) located on the cylindrical surface. At this time, the urging force of the springs (34) (35) does not act on the rear wheel steering rod (12) as a moment around the axis (O), and the rear wheel steering rod (12) does not apply the rotational force. Not done. Therefore, no large torque is required to return the steering wheel (10) to the neutral position.

[0027]

[Effect of device]

 According to the rear wheel steering system of the present invention, as described above, only when the rotation angle of the rear wheel steering rod when it is rotated from the neutral position is within the predetermined range, the rear wheel steering rod reverses its rotation direction. If the rear wheel steering rod is returned to and held in the neutral position by the application of a rotational force in the direction, and the steering angle of the front wheels becomes large and the rotation angle of the rear wheel steering rod becomes outside the above specified range, No rotational force is applied to the wheel steering rod. Therefore, no large torque is required to return the steering wheel to the neutral position.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view of a rear wheel steering system.

FIG. 2 is an enlarged cross-sectional view taken along the line II-II of FIG. 1 with a part omitted.

FIG. 3 is a perspective view showing a cam-shaped portion of a rear wheel steering rod.

FIG. 4 is a view corresponding to FIG. 2 showing a state in which a rear wheel steering rod has rotated within a predetermined angle range from a neutral position.

5 is a view corresponding to FIG. 2 showing a state in which the rear wheel steering rod has rotated beyond a predetermined angle range from the neutral position.

6 is a view taken along the line VI-VI of FIG.

FIG. 7 is a diagram schematically showing a configuration of a four-wheel steering vehicle including a rear wheel steering device.

FIG. 8 is a transverse cross-sectional view showing a conventional example with an input shaft in a neutral position.

9 is a view corresponding to FIG. 8 showing a state in which the input shaft of the conventional example is rotated within a predetermined angle range from the neutral position.

10 is a view corresponding to FIG. 8 showing a state in which the input shaft according to the conventional example has rotated beyond a predetermined angle range.

[Explanation of symbols]

 7 front wheel 11 input shaft 12 rear wheel steering rod 13 housing 14 rear wheel 31 cam-shaped portion 31a first portion 31b second portion 32 biasing member 34 compression coil spring 35 compression coil spring O rear wheel steering rod axis

Front page continuation (72) Takeshi Goto 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. An input shaft rotated when steering front wheels,
A rear wheel steering rod, which is supported by the housing so as to rotate around an axis extending in the left-right direction and move in the axial direction when the input shaft rotates, and which steers the rear wheel by moving in the axial direction A rear wheel steering device for a four-wheel steering vehicle, which is fixedly provided on a peripheral surface of a rear wheel steering rod for a predetermined length such that a ratio of a moving distance in the axial direction and a rotation angle around the axial line is constant. A twisted cam-shaped portion, a biasing member which is provided in the housing so as not to move in the left-right direction but moves in a direction orthogonal to the axis of the rear wheel steering rod, and which abuts on the cam-shaped portion, A spring for urging the urging member toward the cam-shaped portion, and a portion of the cam-shaped portion with which the urging member abuts when the rotation angle from the neutral position of the rear wheel steering rod is within a predetermined range. , The rear wheel steering rod to the neutral position A rear-wheel steering system for a four-wheel steering vehicle, which is shaped so as to receive a force for returning and holding it from an urging member, and the rest of which is located on a cylindrical surface centered on the axis of the rear-wheel steering rod. .