JP2522177Y2 - Four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) In the present invention, a front wheel steering device and a rear wheel steering device are interlocked via a mechanical transmission means to steer a rear wheel according to a steering angle of a front wheel. And a four-wheel steering device.

(Prior Art) As this type of four-wheel steering device, there is a type using a power steering device as a rear wheel steering device, as disclosed in Japanese Patent Application No. 1-250033 previously proposed by the applicant. In this technique, as shown in FIGS. 4 and 15, the operation of the front wheel power steering device 10 is controlled by mechanical transmission means including operating cables 35a and 35b, a steering characteristic imparting mechanism 30, an assist delay avoiding mechanism 40, and the like. The operating oil is transmitted to the operating shaft 52 of the rear wheel servo valve 50 of the rear wheel power steering device 20 and operated by the rear wheel servo valve 50 which operates according to the input torque. The steering assist force is applied to the rear wheel 29 by controlling the supply and discharge of the vehicle.

(Problems to be Solved by the Invention) In this conventional technology, when the steering wheel 15 is rotated greatly, the rear wheel rack bar 3 of the rear wheel power steering device 20 hits the stopper before the operation of the front wheel steering device 10 is stopped. Stopped. In this state, irrespective of the steering reaction force from the rear wheels, a considerable torque corresponding to the steering of the front wheel steering device 10 is applied to the operating shaft 52, so that the rear wheel servo valve 50 remains largely operated, and the supply pump 60 Oil pressure rises to the relief pressure. This causes problems such as energy loss due to an increase in engine load, increase in pump noise, increase in oil temperature, and the like. In a power steering device other than the hydraulic type, if the rear wheel rack bar 23 or a portion corresponding thereto is first stopped by hitting a stopper, the control mechanism operates to generate unnecessary force on the booster mechanism. Problems such as heat loss, temperature rise, and parts consumption.

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to enable the front wheels to be steered even after the rear wheels are stopped.

(Means for Solving the Problems) To this end, the four-wheel steering device according to the present invention includes, as illustrated in the accompanying drawings, a front wheel steering device 10 for steering front wheels.
A rear wheel steering device 20 for steering rear wheels, and mechanical transmission means for transmitting the operation of the front wheel steering device 10 to the rear wheel steering device 20.The rear wheel steering device 20 controls the rear wheels. An operating member 23 to be steered, a booster mechanism 24 for applying an assist force to the operating member, and the booster mechanism which operates in response to an input given to an input member 52 through the mechanical transmission means.
In a four-wheel steering device comprising a rear wheel power steering device provided with a control mechanism 50 for increasing and decreasing the assist force by the 24, a part of the mechanical transmission means includes a front wheel steering device 10 if the transmission force is equal to or less than a predetermined value. Is transmitted to the input member 52, but if the transmission force exceeds a predetermined value, it bends and the front wheel steering device
A transmission force limiting mechanism M that stops transmitting the operation of 10 to the input member 52 is provided, and a part of the movable portion of the rear wheel power steering device 20 is a fixed portion between the transmission force limiting mechanism M and the input member 52. And a stopper mechanism 70 for stopping the operation of the input member 52 before the steering of the rear wheel is stopped.

Further, the mechanical transmission means of the four-wheel steering device according to the present invention includes:
A driven rotation member 34 provided in the housing 21 of the rear wheel power steering device 20 and connected to the input member 52, and is fixed to the housing 21 so as to be rotatable and coaxial with the driven rotation member 34. The input shaft 31 supported by the cap portion 21a, and an interlocking mechanism for transmitting the rotation of the input shaft 31 to the driven rotation member 34 with predetermined characteristics, and the rotation of the cap portion 21a with respect to the housing 21 The rear wheel power steering device 20 includes a steering characteristic imparting mechanism 30 for adjusting a neutral position, and the stopper mechanism 70 is rotatably fitted to the housing 21 and is rotatably engaged with the cap portion 21a in a rotational direction. 371a may be provided.

(Operation) By turning the steering wheel, the front and rear steering devices 10, 20
Are operated in conjunction to steer the front and rear wheels. If the front wheel steering device 10 is largely operated by the steering wheel, the stopper mechanism 70 is operated and the input member 52 is stopped before a part of the movable portion of the rear wheel power steering device 20 comes into contact with the fixed portion. Accordingly, the control mechanism 50 operates mainly in response to the steering reaction force from the rear wheels to generate an assist force in the booster mechanism 24.
Since the stopper mechanism 70 is provided between the transmission force limiting mechanism M and the input member 52, even after the input member 52 of the control mechanism 50 is stopped by the stopper mechanism 70 and the steering of the rear wheels is stopped, the transmission is stopped. The front wheel steering device 10
Works.

In addition, the neutral position of the rear wheel power steering device 20 is adjusted by the rotation of the cap portion 21a with respect to the housing 21, and the projection 371a of the stopper mechanism 70 is engaged so as to rotate with the cap portion 21a. The change in the maximum steering angle of the left and right rear wheels due to the adjustment of the neutral position is compensated by the rotation of the stopper mechanism 70.

(Effects of the Invention) As described above, according to the present invention, even at the rear-wheel maximum steering position, the booster mechanism only generates the necessary assist force mainly in accordance with the steering reaction force, and generates an unnecessary force. Energy loss and temperature rise,
In addition, the durability of the component can be improved. Further, since the stopper mechanism is provided between the transmission force limiting mechanism and the input member, the front wheels can be steered even after the steering of the rear wheels is stopped. Further, according to the engagement of the stopper mechanism so as to rotate together with the cap portion, the maximum steering angle of the left and right rear wheels does not become different values by adjusting the neutral position, and the adjustment of the neutral position can be largely performed. Even when the steering is performed, the rear wheel rack bar or a corresponding portion may hit the stopper before the stopper mechanism is operated during one of the steering operations, and the control mechanism may operate to generate unnecessary force on the booster mechanism. Absent.

Embodiment First, a first embodiment shown in FIGS. 1 to 6 will be described. The overall structure of the four-wheel steering system will be described with reference to FIG.
A predetermined amount of working fluid sucked out of the reservoir 62 and sent out is divided at a predetermined ratio by the flow dividing valve 61, one of which is supplied to the front wheel steering device 10, the other is supplied to the rear wheel steering device 20, The used working fluid is returned to the reservoir 62.

The front wheel steering device 10 includes a front wheel servo valve 11 provided in the middle of a handle shaft 16 that transmits a rotation of a steering wheel 15 to a rack and pinion mechanism 12 that converts the rotation of a steering wheel 15 into a reciprocating motion of a front wheel rack bar 13.
And a power steering device having a front wheel power cylinder 14 provided on a front wheel rack bar 13 as a main component. The front wheel servo valve 11 operates according to the steering wheel torque input from the steering handle 15, and controls the supply and discharge of the working fluid supplied from the supply pump 60 to the front wheel power cylinder 14 via the shunt valve 61, thereby amplifying it. The steering force is output to the front wheel rack bar 13, and the left and right front wheels 19 are steered via tie rods 17 and knuckle arms 18 provided at both ends thereof.

The rear wheel steering device 20 is a power steering device including a rotary type rear wheel servo valve 50 and a rear wheel power cylinder 24, as shown in FIGS. The rear wheel rack bar 23, which is an operating member of the rear wheel 29, is connected to the rear wheel power steering device 20.
Of the rear wheel servo valve 50, the shaft 21 is rotatably supported by the housing 21 and is interlocked with the output shaft 51 via the pinion 22 and the rack 23a. Is connected to a knuckle arm 28 supporting the knuckle.
The rear wheel power cylinder 24 includes a cylinder 25 formed in the housing 21 and a piston 26 which is inserted into the cylinder 25 in a liquid-tight manner to separate the inside into left and right working chambers. Both ends are cylinders fixed to the piston
It protrudes from both ends of 25 in a liquid-tight and slidable manner. A pair of return springs is provided between both side surfaces of the piston 26 and inner surfaces of both ends of the cylinder 25 to return the rear wheel rack bar 23 to a neutral position in the drawing.

As shown in FIG. 4, a mechanical transmission means for connecting the front and rear steering devices 10 and 20 has a cable length adjusting device at an intermediate portion.
A pair of operation cables 35a, 35b provided with 36 and a steering characteristic imparting mechanism provided in the housing 21 of the rear wheel steering device 20
30 and an assist delay avoidance mechanism 40.
As shown in FIGS. 1 and 2, a stopper mechanism 70, which is a main part of the present invention, is provided in the housing 21.

Each operation cable 35a, 35b is composed of an inner wire and an outer tube, one end of each inner wire is connected to a projection provided at each end of the front wheel rack bar 13, and the other end of each inner wire is formed at an input end 31 described below. It is wrapped around and fixed to the input pulley 31a. Both ends of each outer tube are attached to a housing (not shown) of the front wheel power steering device 10 and a cap portion 21a of the housing 21, respectively. Thus, the input shaft 31 is rotated according to the reciprocating motion of the front wheel rack bar 13.

As shown in FIG. 1, the steering characteristic imparting mechanism 30 includes a housing 21, an input shaft 31 and a driven rotary member 34 supported eccentrically and eccentrically and rotatably in a cap 21a fixed thereto. V formed on the rear surface of the input shaft 31
A follower 33 eccentrically provided on a driven rotation member 34 is engaged in the cam groove 32 having the shape. The follower 33 is a driven rotary member.
It comprises a support pin 33a fixed to 34 and a roller 33b rotatably supported at the front of the support pin 33a. The rear end of the support pin 33a protrudes rearward from the driven rotary member 34. The roller 33b of the follower 33 is located in the cam groove 32 with a certain gap. As a result, as shown in FIG. 6, the characteristic of the rotation angle of the driven rotary member 34 with respect to the input shaft 31 is such that when the input shaft 31 rotates from the neutral steering state, the driven rotation until the roller 33b contacts the cam groove 32. The member 34 does not rotate, and thereafter, as the rotation angle of the input shaft 31 increases, the rate of increase in the rotation angle of the driven rotation member 34 gradually increases.

As shown in FIG. 1, the assist delay avoiding mechanism 40 includes an input rotary member 41 formed coaxially and integrally with the driven rotary member 34 of the steering characteristic imparting mechanism 30, and an axial direction coaxial with the input rotary member 41. Intermediate rotating member 42 and output rotating member
43, and each of the rotating members 41, 42, 43 is supported by the housing 21. A spiral spring 44 is wound around a first engagement boss 46 supported between the rotating members 41 and 42 via a bearing. The spiral spring 44 is formed by spirally winding a strip of spring steel or the like, and in a state where no torque is applied between the input and intermediate rotating members 41 and 42, an initial torque is given to the outer end bent portion thereof. Are simultaneously engaged from the circumferential direction with the respective engagement pins 41a, 42a press-fitted and fixed to both the rotating members 41, 42, and the inner end bent portion is engaged with the engagement boss 46. At the same time,
The support pin 33a and the engagement pin 42b press-fitted and fixed to the two rotating members 41 and 42 are simultaneously abutted from the circumferential direction by projections formed on both sides of the first engagement boss 46 by the biasing force of the spiral spring 44. ing.

A spiral spring 45, which is the same as the spiral spring 44, is provided on the second engagement boss 47 supported between the rotating members 42 and 43 via a bearing. Like the spiral spring 44, the spiral spring 45 has its outer bent portion engaged with each of the engagement pins 42c, 43a press-fitted and fixed to both the rotating members 42, 43, and the inner bent portion as the second engagement boss. 47
Are engaged with both rotating members 42, 43 via the.

The assist delay avoiding mechanism 40 transmits the rotation of the input rotary member 41 to the output rotary member 43 as it is when the transmission torque between the rotary members 41 and 43 is equal to or less than the initial torque of the spiral springs 44 and 45. Spiral spring 4 if torque exceeds
4, 45 are bent so that the rotation of the input rotary member 41 is not transmitted to the output rotary member 43. In the present embodiment, the assist delay avoiding mechanism 40 includes an input and an intermediate rotating member.
41, 42, a spiral spring 44, a transmission force limiting mechanism M including a first engagement boss 46, etc., and intermediate and output rotary members 42, 43, a spiral spring 4
5. Although the transmission force limiting mechanism M including the second engagement boss 47 and the like is arranged in series, one or three or more transmission force limiting mechanisms M may be used.

As shown in FIG. 1, the rear wheel servo valve 50 has an operating shaft 52 and an output shaft 51, which are input members, supported in the housing 21 so as to be relatively rotatable coaxially with each other. It is elastically connected by a torsion bar 56 that is provided in a separate manner. The pinion 22 formed on the rear portion of the output shaft 51 is engaged with a rack 23a formed on the rear wheel rack bar 23. The yoke 58, which is serration-coupled to the tip of the operating shaft 52 and fixed so as not to come off, has a notch formed in the radial direction engaged with the rear end of the engaging pin 43b of the output rotary member 43, and the assist delay avoiding mechanism 40 is provided. It is connected to.

A main part of the rear wheel servo valve 50 is a four-port throttle switching valve including a rotor valve member 53 formed on a part of the operating shaft 52 and a sleeve valve member 54 connected to the output shaft 51 by a pin 55.
If the torsion bar 56 is twisted by the transmission torque applied to the operation shaft 52 from the assist delay avoidance mechanism 40 and a relative rotation occurs between the two valve members 53 and 54, the input port 50a is connected to the input port 50a according to the direction and the relative rotation angle. The supplied working fluid is supplied from one of the two distribution ports 50c and 50d to the rear wheel power cylinder 24.
Of the other working chamber, and the working fluid in the other working chamber from the other distribution port through the discharge port 50b to the reservoir 62.
To generate a steering assist force to the rear wheel 29.

The stopper mechanism 70 which is a main part of the present invention is an intermediate rotating member.
It is provided between 42 and the housing 21. As shown in FIG. 1 and FIG.
An annular groove 73 is formed, and a locking pin 74 slightly projecting from the outer peripheral surface is implanted and fixed to the intermediate rotating member 42 in the axial direction so as to coincide with the annular groove 73 in the axial direction. .
The collar 71 fitted on the inner peripheral surface of the housing 21 is fixed by a push screw 77 for pressing a flat part 71a formed in a part, and a part elongated on the opposite side to the flat part 71a along the circumferential direction. A guide hole 72 having a constant width (see FIG. 3) is formed in alignment with the annular groove 73. Between the inner peripheral surface of the housing 21 and the annular groove 73, a steel stopper ball 75 is provided with a guide hole 72.
It is held movably along the inside. The collar 71 also has a spacer function for bearings that support the input and output rotary members 41 and 43.

At the rear wheel steering neutral position, as shown by the solid line in FIG.
The locking pin 74 is located just opposite the guide hole 72.
From this position, the intermediate rotation member 42 is rotated clockwise by an angle α.
(220 degrees in the present embodiment).
When the position of 4A is reached, the locking pin 74 is moved to one end face 72a of the guide hole 72 through a stopper ball 75 indicated by a two-dot chain line 75A.
Therefore, the further rotation of the intermediate rotating member 42 is prevented. Similarly, if the intermediate rotation member 42 rotates the angle α in the counterclockwise rotation direction from the steering neutral position, the locking pin 74 that has reached the position of the two-dot chain line 74B is moved via the stopper ball 75 to the other end surface 72b of the guide hole 72. And further rotation is prevented.

The maximum stroke of the rear wheel rack bar 23, which is a movable portion of the rear wheel power steering device 20, is regulated by contact with a fixed portion (for example, the piston 26 contacts the inner end surface of the cylinder 25). Reference numeral 42 is such that the rear wheel steering stopper reaches the angle α before contact with the rear wheel steering stopper, and further rotation is prevented. Therefore, even if the input rotary member 41 rotates by more than the angle α, the rear wheel rack bar 23 does not move more than the value corresponding to the angle α, and the rear wheel steering stopper does not abut.

The components mounted on the housing 21 are assembled such that the rear wheel rack bar 23 is also at the neutral position when the steering characteristic imparting mechanism 30 is at the neutral position. The subassembly assembled in this manner needs to be kept in a neutral state in order to facilitate the work of assembling the vehicle body. For this purpose, as shown in FIG. 1, the input shaft 31 is attached to the cap 21a.
The neutral lock pin 38 is screwed so as to be able to move forward and backward. If the neutral lock pin 38 is advanced at a position where the input shaft 31 of the steering characteristic imparting mechanism 30 is in the neutral state, the tip 38a engages with a conical hole formed in the input shaft 31 as shown in FIG. The shaft 31, and thus the entire sub-assembly, is held neutral. In a normal use state, the neutral lock pin 38 is retracted to allow the input shaft 31 to rotate freely.

 Next, the operation of the first embodiment will be described.

When the steering wheel 15 is rotated clockwise from the neutral position as shown by the arrow in FIG. 4, the front wheel power steering device 10 operates as described above, and the front wheel rack bar 13 moves rightward as shown by the arrow. The left and right front wheels 19 are steered rightward. As a result, the input shaft 31 of the steering characteristic imparting mechanism 30 is connected to the operation cable 35.
Via a, 35b, it is rotated in the counterclockwise rotation direction when viewed later. Conversely, when the steering wheel 15 is rotated counterclockwise, each part operates in the opposite direction to the above, the front wheel 19 is steered leftward, and the input shaft 31 is rotated clockwise when viewed from behind. In response to the rotation of the input shaft 31, the driven rotary member 34 rotates with characteristics as shown in FIG.

In a normal state, since the rear wheel steering torque is small, the assist delay avoiding mechanism 40 does not operate, and the rotation of the driven rotary member 34 is transmitted from the yoke 58 to the operating shaft 52 as it is to operate the rear wheel servo valve 50. When the front wheel 19 is steered to the right, the input shaft 31 and the operating shaft 52 and the output shaft 51 of the rear wheel servo valve 50 rotate counterclockwise as viewed from the rear, and the rear wheel 29 passes through the rear wheel rack bar 23. Steer to the left. On this occasion,
The rear wheel servo valve 50 operates in accordance with the rear wheel steering torque applied to the input member 52 as described above, and the left and right operations of the rear wheel power cylinder 24 of the working fluid supplied from the supply pump 60 via the branch valve 61. The rear rack bar 23
To assist power. If you steer the front wheel 19 to the left,
Each part operates in the opposite direction to the above, and the rear wheel 29 is steered rightward. In other words, the rear wheels 29 respond to the steering of the front wheels 19,
Steering is reversed (with the characteristics shown in FIG. 6).

If the input shaft 31 rotates in response to the steering of the front wheel 19, the rear wheel rack bar 23 is not rotated until the rotation angle of the input shaft 31 reaches the rear wheel maximum steering position R which is the angle α at which the stopper mechanism 70 operates. It moves with the characteristics shown in FIG. If the steering wheel 15 is further rotated from this position, the front wheels 19 are further steered and the input shaft 31
Is also rotated to reach the maximum handle rotation position H, during which the transmission force limiting mechanism M of one of the assist delay avoiding mechanisms 40 is
The spiral spring 44 is bent and the intermediate rotating member 42 does not rotate, and therefore the operating shaft 52 does not rotate, so that the rear wheel rack bar 23 remains stopped before reaching the rack bar stopper position S in contact with the fixed portion. .

In this state, only the torque generated by the return spring of the rear wheel power cylinder 24 and the steering reaction force from the rear wheel 29 is applied to the operating shaft 52, so that the relative rotation angles of the two valve members 53 and 54 have a normal value. Kept within range. As a result, the pressure generated by the supply pump 60 with respect to the stroke of the rear wheel rack bar 23 does not significantly increase near the end of the stroke as shown in FIG. 5, and does not reach the relief pressure. Therefore, there is no problem of energy loss and noise increase due to the supply pump 60, the rise in oil temperature is small, and there is no danger of the supply pump 60 burning.

When the steering wheel 15 is turned with force in a state where the rear wheel 29 is dropped into a groove or the like and the steering is blocked, the spiral springs 44 and 45 bend and the rotation of the input rotary member 41 does not occur. Transmission to the operating shaft 52 is stopped, and an increase in transmission torque is prevented. As a result, there is no danger that an excessive force will be applied to the mechanical transmission means or each part of the rear wheel power steering device 20.

7 and 8 show a first modification of the stopper mechanism 70. FIG. On the outer periphery of the intermediate rotating member 142 supported by the housing 21 and connected to the spiral springs 44 and 45 similarly to the intermediate rotating member 42, a spiral groove 173 of about one turn is formed. A guide hole 172 is formed in the collar 171 which is fitted on the inner periphery of the housing 21 and is positioned and fixed by a locking pin 177 instead of the push screw 77, and is guided and supported by the guide hole 172 so as to be movable only in the axial direction. The sliding stopper 174 has a spiral groove 173
A protrusion 174a slidably engaged with is formed integrally. When the intermediate rotating member 142 rotates, the sliding stopper 174 moves slightly in the axial direction along the guide hole 172.

At the rear wheel steering neutral position, as shown in FIG.
174a is located at the center of the spiral groove 173 in the circumferential direction.
From this position, the intermediate rotating member 142 is rotated clockwise by an angle α.
When rotated, the protrusion 174a of the sliding stopper 174 is
Abuts against one end surface 173a, so that further rotation of the intermediate rotating member 42 is prevented. Similarly, if the intermediate rotation member 142 rotates the angle α in the counterclockwise rotation direction from the steering neutral position,
The projection 174a comes into contact with the other end surface 173b, and further rotation is prevented.

9 and 10 show a second modification of the stopper mechanism 70. FIG. On the outer periphery of the intermediate rotating member 242 supported by the housing 21 and connected to the spiral springs 44 and 45 in the same manner as the intermediate rotating member 42, an annular groove 272 having a semi-circle less than a deep groove portion 272a is formed. Intermediate rotating members on the walls on both sides of the deep groove 272a
A pair of arc-shaped guide holes 273 centered on the rotation axis of 242
Are formed. Sliding stopper 274 with a substantially convex side
The two protruding ends of a pair of sliding pins 275 press-fitted and fixed on both lower sides are guided and supported by each guide hole 273, and the
a can be moved in an arc shape.
75 stops at a position where it contacts the ends 273a and 273b of the guide hole 273. On the other hand, a locking projection 271a integrally formed with the collar 271 fitted and fixed to the inner surface of the housing 21 similarly to the collar 171
Are located in the annular groove 272. The protrusion 274a projecting outward from the slide stopper 274 can contact the locking protrusion 271a in the circumferential direction.

At the rear wheel steering neutral position, as shown by the solid line in FIG.
The locking projection 271a is located just opposite the deep groove 272a and the guide hole 273. If the intermediate rotation member 242 rotates the angle α in the clockwise direction from this position, the locking protrusion 271a comes into contact with the protrusion 274a of the sliding stopper 274 that has reached the position indicated by the two-dot chain line 274A and stopped. Further rotation of the rotating member 42 is prevented. Similarly, when the intermediate rotation member 42 rotates the angle α in the counterclockwise rotation direction from the steering neutral position, the two-dot chain line
The protrusion 274a stopped at the position of 274B is the locking protrusion 27.
In contact with 1a, further rotation is prevented.

In the state where the sub-assembly is locked by engaging the neutral lock pin 38 with the input shaft 31 as described above, if there is a manufacturing error or an assembly error of each part, the steering characteristic imparting mechanism 30 and the rear wheel rack bar 23 Some deviation of the neutral position occurs during the operation. For this reason, the cap 21a is rotatable coaxially with the input rotating member 41 with respect to the housing 21, and the hole 21b through which the tightening bolt 21c for fixing the cap 21a to the housing 21 passes is defined as an arc-shaped elongated hole. It is necessary to adjust this deviation by changing the mounting angle of the cap portion 21a with respect to. However, with such adjustment, the left and right maximum stroke positions of the rear wheel rack bar 23 with respect to the steering neutral position may change, and the maximum steering angle of the rear wheel 29 may differ between the left and right. The second embodiment shown in FIGS. 11 and 12 solves such a problem.

In the second embodiment, a collar 371 corresponding to the collar 71 of the first embodiment, which is a fixed-side member of the stopper mechanism 70, is rotated according to the rotation of the cap portion 21a for adjusting the deviation of the neutral position.
Also rotate. As shown in FIGS. 11 and 12, a recess 322 is formed in a part of the inner peripheral surface of the housing 21 on the side of the cap portion 21a in the circumferential direction.
A projection 3 inserted into the recess 322 is partially provided on the end face of the portion 1a.
21 are integrally formed. A circumferential gap is provided between the protruding portion 321 and the concave portion 322 to allow rotation of the cap portion 21a (see the angle β in FIG. 12) for adjusting the neutral position. The collar 371 is partially cut away on the 211 side and bent outward to form a projection 371a, and the projection 321
The projection 371a is engaged with the notch 321a formed at the tip without any play in the circumferential direction.

In addition, a locking pin 37 corresponding to the first embodiment
4 is provided not parallel to the radial direction but parallel to the axial direction. Since the structure of the second embodiment other than the above is the same as that of the first embodiment, the same portions are denoted by the same reference numerals and detailed description thereof will be omitted.

If the cap portion 21a is rotated to adjust the deviation of the neutral position, the collar 371 is also rotated accordingly, so that the stop position of the intermediate rotating member 42 by the stopper mechanism 70 is also changed to the cap portion.
It changes in the same direction by the same angle as the adjustment angle of 21a. Since the maximum stroke position of the rear wheel rack bar 23 also changes accordingly, the change in the maximum stroke position due to the rotation of the cap portion 21a is compensated. Therefore, even when the turning angle of the cap portion 21a for adjusting the neutral position increases, the maximum steering angles of the left and right rear wheels 29 do not become different values. In addition, along with this, the rear wheel rack bar 23 abuts on the fixed side and is stopped before the stopper mechanism 70 operates in any one of the steering operations, so that the discharge pressure of the supply pump 60 increases to the relief pressure. No fear.

In the first embodiment, since the round locking pin 74 is implanted in the radial direction, the stopper ball 75 is
When the locking pin 74 and the stopper ball 75 are sandwiched between the a (or 72b), the locking pin 74 and the stopper ball 75 may be displaced in the axial direction, and axial thrust may be generated in the intermediate rotating member 42. When such thrust occurs, the spiral spring 44 or 45 is sandwiched between the intermediate rotating member 42 and the rotating member 41 or 43, and the operation of the assist delay avoiding mechanism 40 is hindered by friction, and the operation cables 35a, 35
Problems such as an increase in the tensile force applied to b occur. However, according to the second embodiment in which the locking pin 374 is parallel to the axial direction, the axial thrust is not applied to the intermediate rotary member 42 due to the contact between the locking pin 374 and the stopper ball 75. Problems are solved.

The operation of the second embodiment other than the above is the same as that of the first embodiment.

FIGS. 13 and 14 show a modification of the structure in which the collar 71 is rotated in accordance with the rotation of the cap portion 21a. A rectangular projecting piece 471 curved in an arc shape is welded to a part of the outer periphery of the collar 71 having the same structure as that of the first embodiment on the side of the cap 21a. A recess 422 for rotatably accommodating the protruding piece 471 together with the collar 71 is formed in a part of the inner peripheral surface on the cap portion 21a side of the housing 21. Cap part 21a
A concave portion 422 is formed in a part of the end surface of the protruding piece 471 so that the tip of the protruding piece 471 is engaged without play in the circumferential direction.

Even in such a modified example, since the collar 71 is rotated according to the rotation of the cap portion 21a, similarly to the second embodiment, the change in the maximum stroke position of the rear wheel rack bar 23 due to the rotation of the cap portion 21a. Is compensated. In addition, the collar 71 to which the protruding piece 471 is welded is easier to manufacture than the collar 371 formed with the protruding portion 371a of the second embodiment. Less fear.

In each of the above embodiments, two sets of transmission force limiting mechanisms M are provided in series, and the stopper mechanism 70 is provided between the two sets of transmission force limiting mechanisms M. However, the number of transmission force limiting mechanisms M may be one or more. The stopper mechanism 70 may be provided on the operating shaft 52 side of any one of the transmission force limiting mechanisms M. In each of the above embodiments, the angle α of the stopper is set to 180 degrees or more to the left and right, so that the structure of the stopper mechanism 70 is slightly complicated. However, depending on the specification of the rear wheel power steering device 20, the stopper having a simple structure is used. Mechanism 70 can also be used.

In the present invention, instead of providing the transmission force limiting mechanism M in the housing 21 of the rear wheel power steering device 20 as in the above embodiment,
It may be provided in the housing of the front wheel power steering device 10 or at an intermediate portion between the operation cables 35a and 35b. Further, the present invention is not limited to the hydraulic power steering apparatus as in the above embodiments, but can be applied to, for example, a four-wheel steering apparatus using an electric power steering apparatus.

[Brief description of the drawings]

1 to 6 show a first embodiment of a four-wheel steering system according to the present invention. FIG. 1 is a longitudinal sectional view of a main part, and FIG. 2 is a II-II in which a central portion of FIG. 1 is omitted. FIG. 3 is a plan view of the collar, FIG. 4 is a schematic plan view of the whole, FIG. 5 is a characteristic diagram of the discharge pressure of the supply pump, and FIG. 7 and 8 show a first modification of the stopper mechanism. FIG. 7 is a partial longitudinal sectional view, and FIG. 8 is VIII-VI of FIG.
9 and 10 show a second modification of the stopper mechanism. FIG. 9 is a partial longitudinal sectional view, and FIG. 10 is a sectional view taken along line XX of FIG. 11 and 12 show a second embodiment, FIG. 11 is a longitudinal sectional view of a main part, and FIG.
FIG. 11 is a sectional view taken along the line XII. FIGS. 13 and 14 show a modification of the structure in which the collar is rotated in accordance with the rotation of the cap portion.
FIG. 13 is a partial longitudinal sectional view, and FIG. 14 is a sectional view taken along the line XIV-XIV of FIG. FIG. 15 is a longitudinal sectional view of a main part of the prior art. Explanation of reference numerals 10 ... front wheel steering device, 20 ... rear wheel power steering device, 21
... housing, 21a ... housing, 23 ... operating member (rear wheel rack bar), 24 ... booster mechanism (rear wheel power cylinder), 30 ... steering characteristic imparting mechanism, 31 ... input shaft, 34 ...
… Driven rotating member, 50… control mechanism (rear wheel servo valve), 52
…… Input member (operating shaft), 70 …… Stopper mechanism, 371a…
... Projection, M ... Transmission force limiting mechanism.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Akira Onishi 1-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Koki Co., Ltd. (72) Inventor Jun Jun Onoda 1-1-1 Asahi-cho, Kariya-shi Aichi Prefecture Inside the company (72) Inventor Satoru Oda 1 Toyota Town, Toyota City, Aichi Prefecture Inside the Toyota Motor Corporation (56) References Japanese Utility Model No. 3-96277 (JP, U)

Claims (2)

(57) [Scope of request for utility model registration] A front wheel steering device for steering front wheels, a rear wheel steering device for steering rear wheels, and mechanical transmission means for transmitting an operation of the front wheel steering device to the rear wheel steering device; The rear wheel steering device is an operating member that steers the rear wheel, a booster mechanism that provides an assisting force to the operating member, and an operating member that operates in response to an input provided to an input member via the mechanical transmission unit to operate the boosting mechanism. In a four-wheel steering system including a rear-wheel power steering device having a control mechanism for increasing and decreasing the assist force, a part of the mechanical transmission means may control the operation of the front wheel steering device if the transmission force is equal to or less than a predetermined value. A transmission force limiting mechanism that transmits to the input member but deflects when the transmission force exceeds a predetermined value and does not transmit the operation of the front wheel steering device to the input member is provided, and between the transmission force limiting mechanism and the input member, After said Contact with four-wheel steering system, characterized in that a stopper mechanism for stopping the operation of the input member before the steering of the rear wheels is stopped in a part fixed portion of the movable portion of the power steering system. 2. The driven transmission member, wherein the mechanical transmission means is provided in a housing of the rear wheel power steering device and connected to the input member, and the housing rotates coaxially with the driven rotation member. An input shaft supported by a cap fixed to be adjustable, and an interlocking mechanism for transmitting the rotation of the input shaft to the driven rotation member with predetermined characteristics, and the rearward rotation of the cap with respect to the housing causes the rearward rotation. A steering characteristic imparting mechanism for adjusting a neutral position of the wheel power steering device, wherein the stopper mechanism includes a protrusion rotatably fitted to the housing and rotatably engaged with the cap portion. 4. The four-wheel steering device according to 1.