JPH0735817Y2 - Four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a four-wheel steering system including a mechanical steering characteristic imparting mechanism that imparts a related characteristic between steering angles of front and rear wheels.

(Prior Art) In a four-wheel steering system of this type, as shown in Japanese Utility Model Laid-Open No. 60-50078, for example, an input shaft that rotates in conjunction with steering of the front wheels and a shaft that is coaxial with the input shaft are provided. A mechanical steering characteristic imparting mechanism including a driven rotary member that is arranged and connected to an output shaft that steers the rear wheels and an interlocking mechanism that transmits the rotation of the input shaft to the driven rotary member with a predetermined characteristic is provided. is there.

(Problems to be solved by the invention) In this type of four-wheel steering system, the steering characteristics of the rear wheels with respect to the steering of the front wheels are centered at the steering neutral position at the same time that the rear wheels are in the steering neutral state in the front wheel steering neutral state. Must be symmetrical as Since the symmetry of such characteristics is impaired by the manufacturing error and the assembly error of the parts, it has to be adjusted after the assembling. However, since the above-mentioned prior art does not have an adjusting mechanism for this, such an adjustment is required. Was difficult.

An object of the present invention is to provide a four-wheel steering device in which such adjustment is extremely easy.

(Means for Solving the Problems) For this purpose, the four-wheel steering system according to the present invention has an input shaft that rotates in conjunction with steering of front wheels, as illustrated in the accompanying drawings.
31 and a driven rotary member 32 connected to the output shaft 51 for steering the rear wheels, which has a parallel rotary shaft center including the case of being coaxial with the input shaft, and the rotation of the input shaft 31 is neutralized by steering. In a four-wheel steering system including a steering characteristic imparting mechanism 30 in a housing 21, the steering characteristic imparting mechanism 30 is composed of an interlocking mechanism 35 that transmits the driven characteristic to the driven rotary member 32 with a predetermined characteristic that is symmetrical with respect to the position.
Reference numeral 21 denotes a housing body 21 that supports the driven rotary member 32.
a and a cover 21b rotatably fixed to the housing body so as to be rotatable coaxially with the driven rotary member 32,
When the cover 21b is relatively rotated with respect to the housing body 21a in a state in which the cover 21b is loosely tightened with respect to the housing body 21a, the input shaft 31 is rotated together with the cover 21b to remove the cover 21b. When the front wheels are steered while being fixed to the housing body 21a, the input shaft 31 is covered by the cover so that the input shaft 31 rotates relative to the cover 21b in conjunction with the steering of the front wheels. It is characterized by being rotatably supported by 21b.

(Operation) When both the front and rear wheels are in the steering neutral position,
When the cover 21b is rotated by loosening the tightening to the housing body 21a, the input shaft 31 rotates together with the housing body 21a and relatively rotates with respect to the housing body 21a and the driven rotary member 32 supported by this. It does not rotate with respect to the cover 21b. Therefore, the center position of the characteristics of the steering characteristic imparting mechanism 30 in the state where both the front and rear wheels are in the steering neutral position moves to either the left or right direction according to this relative rotation angle,
The characteristic between 31 and the driven rotary member 32 translates in the left-right direction.

(Effect of the Invention) As described above, according to the present invention, the characteristics between the input shaft and the driven rotary member can be translated in the left-right direction by rotating the cover with respect to the housing body. Even if the center position of the characteristics of the steering characteristic imparting mechanism shifts to the left or right direction due to production error or assembly error, and the steering characteristics of the rear wheels with respect to the front wheels become asymmetrical, this characteristic should be symmetrical. Can be adjusted to.
Moreover, the rotation of the cover with respect to the housing body for this adjustment can be performed by an extremely simple operation of loosening the tightening of the both.

(Embodiment) The present invention will be described below with reference to an embodiment shown in the accompanying drawings.

As shown in FIG. 5, in the present embodiment, power steering devices are used as the front and rear wheel steering devices 10 and 20, respectively. A predetermined amount of working fluid sucked and delivered from the reservoir 62 by the supply pump 60 driven by the engine 63 of the automobile is diverted at a predetermined ratio by the shunt 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, and the used working fluid is returned to the reservoir 62.

The front wheel power steering device 10 includes a rack and pinion mechanism 12 that converts the rotation of the steering wheel 15 into the reciprocating motion of the front wheel operating rod 13.
A known rotary type front wheel servo valve 11 provided in the middle of a handle shaft 16 for transmission to a front wheel power cylinder 14 provided on a front wheel operating rod 13 is a main constituent member. The front-wheel servo valve 11 is substantially the same as the rear-wheel servo valve 50 described later, and operates according to the steering wheel torque input from the steering wheel 15, and feeds the pump 60 from the supply pump 60 to the front-wheel power cylinder 14 via the shunt valve 61. Controlling the supply and discharge of the working fluid supplied to the left and right working chambers, the amplified steering force is output to the front wheel working rod 13, and the tie rods provided at both ends thereof are controlled.
The left and right front wheels 19 are steered via the 17 and the knuckle arm 18.

As shown in FIGS. 1 and 5, the rear wheel power steering device 20 includes a rotary type rear wheel servo valve 50 and a rear wheel power cylinder 24, and further includes a steering characteristic imparting mechanism 30 and an assist delay avoiding mechanism 40. ing. Rear wheel power cylinder 24
As shown in FIG. 5, is a cylinder 25 formed in the housing 21 of the rear wheel power steering apparatus 20, and a piston 26 that is liquid-tightly fitted in the cylinder 25 and separates the inside into left and right working chambers. The rear wheel operating rod 23 fixed to the piston 26 has both ends projecting from both ends of the cylinder 25 in a liquid-tight manner and slidably. Both sides of piston 26 and cylinder
A pair of return springs for returning the rear wheel operating rod 23 to the neutral position shown in the figure are provided between the inner surfaces of both ends of 25, and both ends of the rear wheel operating rod 23 are connected to the rear wheel 29 via the tie rod 27 and the knuckle arm 28. It is connected.

As shown in FIG. 1, the steering characteristic imparting mechanism 30 includes an input shaft 31,
The rotation of the driven rotary member 32 and the former 31 is controlled by the latter 32 with a predetermined characteristic.
It is configured by an interlocking mechanism 35 that transmits to. The housing 21 is composed of a housing main body 21a composed of a plurality of parts and a cover 21b provided at the front end thereof, and the driven rotary member 32 is supported by the front part of the housing main body 21a so as to be rotatable around a rotation axis O2. The cover 21b is fitted to the front end of the housing main body 21a via the spigot portion 21c so as to be rotatable coaxially with the driven rotary member 32, and each of the three elongated holes 21d provided in the flange portion on the outer periphery thereof. And the fastening bolts 21e. As shown in FIG. 2, each elongated hole 21d has a circular arc shape centered on the rotation axis O2, and therefore the cover 21b has a predetermined angle allowed by the elongated hole 21d (in the embodiment, 7 degrees to the left and right from the center position). It can be fastened and fixed to the housing body 21a at any angle within the range. In FIG. 6, 21f is a bending washer having a round hole 21g into which the tightening bolt 21e can be inserted, and both ends are bent and locked to the flange portion of the cover 21b after adjusting the neutral position described later. There is. This has the function of preventing the cover 21b from rotating when the tightening bolt 21e is loosened. The input shaft 31 is rotatably supported by the cover 21b,
The rotation axis O1 is parallel to the rotation axis O2 and is eccentric by a distance A.

The interlocking mechanism 35 of the steering characteristic imparting mechanism 30 is constituted by a guide groove 36 and a follower 37 as shown in FIGS. The follower 37 is fixed to the driven rotating member 32 and is fixed to the input shaft 31.
It comprises a support pin 37a protruding toward and a roller 37b rotatably supported by the support pin 37a. The support pin 37a is provided eccentrically from the rotation axis O2 by a distance B larger than the distance A. Further, the guide groove 36 has a left-right symmetrical shape including a central groove portion 36a formed on the rear end surface of the input shaft 31 and a pair of outer groove portions 36b extending from both ends thereof in an inverted eight shape, and in the neutral state shown, the follower 37 Is located exactly in the center of the central groove 36a. Therefore, the rotation of the input shaft 31 is controlled by the driven rotary member.
The operating characteristic of the steering characteristic imparting mechanism 30 transmitted to 32 is bilaterally symmetric and has a central position.

As shown in FIG. 5, a cable length adjusting device 66 is provided at the middle portion.
The pair of operation cables 65a, 65b provided with is composed of an inner wire and an outer tube, one end of each inner wire is connected to a protrusion provided on each end of the front wheel operating rod 13, and the other end of each inner wire is formed on the input shaft 31. Made pulley
The input shaft 31 is wound around 31a, and the input shaft 31 is rotated according to the reciprocal movement of the front wheel operating rod 13. Both ends of each outer tube are attached to a housing (not shown) of the front wheel steering apparatus 10 and a cover 21b. Therefore, as described above, loosen the tightening bolt 21e and cover 21b.
When is rotated with respect to the housing body 21a, the input shaft 31 is also rotated integrally with the cover 21b.

As shown in FIG. 1, the rear wheel servo valve 50 is a driven rotary member with an assist delay avoidance mechanism 40, which will be described later, interposed therebetween.
It is provided in the housing main body 21a coaxially with 32.
The output shaft 51 of the rear wheel servo valve 50 and the hollow actuation shaft 52 are coaxially and relatively rotatably supported in the housing body 21a and connected by a torsion bar 56, and the pinion 22 formed at the rear portion of the output shaft 51. Engages with a rack 23a formed on the rear wheel operating rod 23. Further, the boss portion of the yoke 57 is engaged with the serration 52a at the front end of the operating shaft 52, and is tightened and fixed by the nut 59 and the spacer 58 which are screwed into the threaded portion 56a at the tip of the torsion bar 56. It is connected to the driven rotation member 32 via the delay avoidance mechanism 40. 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. When the input torque applied to the operating shaft 52 is 0 and the relative rotation angle between the rotor valve member 53 and the sleeve valve member 54 is 0, the working fluid supplied from the supply pump 60 to the input port 50a via the flow dividing valve 61 is transferred. Directly from the discharge port 50b to the reservoir 6
Discharge to 2. However, if the input torque applied to the actuation shaft 52 increases and relative rotation occurs between the valve members 53, 54, the working fluid supplied to the input port 50a is changed according to the direction and the relative rotation angle. One of the two distribution ports 50c, 50d is introduced into one working chamber of the rear wheel power cylinder 24, and the working fluid in the other working chamber is discharged from the other distribution port to the reservoir 62 via the discharge port 50b. The steering assist force to the rear wheels 29 is generated.

In addition, the front wheel servo valve 11 is a screw part at the tip of the torsion bar 56.
Except that 56a is removed, it is exactly the same as the rear wheel servo valve 50, its operating shaft is connected to the handle shaft 16 by serration at the tip, and the pinion at the tip of the output shaft constitutes a part of the rack and pinion mechanism 12. is doing.

As shown in FIG. 1, the assist delay avoidance mechanism 40 includes an intermediate rotation member 41 and an output rotation member 42, which are rotatably supported by the housing body 21a coaxially with the driven rotation member 32 and the rear wheel servo valve 50, and The driven rotary member 32 and the intermediate rotary member 41, and the intermediate rotary member 41 and the output rotary member 42 are composed of spiral springs 43 and 44 which are interposed by applying initial torque, respectively, and the output rotary member 42 is planted in the yoke 57. Actuator shaft 5 with pin 57a
It is connected to rotate with 2. This assist delay avoidance mechanism 40 allows the driven rotary member 32 to rotate as it is from the output rotary member 42 to the operating shaft 52 when the torque transmitted between the rotary members 32 and 42 is less than or equal to the initial torque of the spiral springs 43 and 44. Is transmitted to each spiral spring, but if the transmitted torque exceeds that,
The rotation of the driven rotation member 32 is caused by the bending of the rotation members 43 and 44 and the output rotation member 42.
It is to prevent it from being transmitted to.

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

If the steering wheel 15 is rotated clockwise from the neutral position as shown by the arrow in FIG. 5, the front wheel steering device 10 operates as described above, and the front wheel operating rod 13 moves rightward as shown by the arrow to move the left and right front wheels. Steer 19 to the right. At the same time, the input shaft 31 of the steering characteristic imparting mechanism 30 is connected to the operation cables 65a, 65
It is rotated in the counterclockwise direction when viewed from the rear via b.
On the contrary, when the steering wheel 15 is rotated counterclockwise from the neutral position, each part operates in the opposite direction to steer the front wheel 19 leftward, and the input shaft 31 rotates clockwise when viewed from the rear. Is rotated to.

By such rotation of the input shaft 31, the guide groove 36 is also rotated counterclockwise or clockwise around the rotation axis O1 from the neutral position shown in FIG. 3, but the rotation angle of the input shaft 31 is changed. As long as the follower 37 is small and inside the central groove 36a, the follower 37 does not move from the neutral position shown in the figure. However the input shaft 31
If the follower 37 enters the outer groove portion 36b due to a large rotation angle of the follower 37, the follower 37 is pushed by the outer groove portion 36b, and the driven rotating member 32 is connected to the input shaft 31 about the rotation axis O2. It will rotate in the same direction. That is, the driven rotating member 32
Rotates with the characteristics shown in FIG. 4 with respect to the rotation angle of the input shaft 31.

In a normal state, since the rear wheel steering torque is small, the assist delay avoidance mechanism 40 does not operate, and the rotation of the driven rotating member 32 is transmitted from the yoke 57 to the operating shaft 52 as it is to operate the rear wheel servo valve 50. . If you steer the front wheels 19 to the right,
Input shaft 31, actuating shaft 52 and output shaft 51 of rear wheel servo valve 50
Is rotated counterclockwise when viewed from behind, and the rear wheel 29 is steered leftward via the rear wheel operating rod 23. At this time, the rear-wheel servo valve 50 operates according to the rear-wheel steering torque, and the shunt valve 61
Supply and discharge of the working fluid supplied from the supply pump 60 via the rear wheel power cylinder 24 to the left and right working chambers are controlled to give an assist force to the rear wheel working rod 23. If you steer the front wheel 19 to the left, each part will operate in the opposite direction to the rear wheel.
29 is steered to the right. Since the relative rotation angle between the operating shaft 52 and the output shaft 51 due to the operation of the rear wheel servo valve 50 is small, the characteristic of the steering angle of the rear wheel 29 with respect to the front wheel 19 is as follows.
Similar to the rotation angle of, the characteristics are as shown in FIG. That is, the rear wheels 29 are steered in the opposite phase according to the steering of the front wheels 19 as shown in the characteristic of FIG.

When both the front and rear wheels 19, 29 are in the steering neutral state and the follower 37 is exactly in the center of the central groove portion 37a of the guide groove 36 as shown in FIG. The steering angle characteristic of the rear wheel 29 with respect to the front wheel 19 is symmetrical as shown in FIG.
However, in the illustrated embodiment, the actuating shaft 52 and the yoke 57 can be engaged only every 10 degrees by the serrations 52a, so that the follower 37 is at the center when the front and rear wheels 19, 29 are both steering neutral. In many cases, the operating position of the steering characteristic imparting mechanism 30 deviates from the center of the groove 37a, and the operating position of the steering characteristic imparting mechanism 30 deviates just from the center of the characteristic. In this case the front and rear wheels
The turning angle from the state where both the steering wheels 19 and 29 are in the neutral state until the actuator 37 starts to engage with the left and right outer groove portions 36b has different values, and the central position of the characteristic of the steering characteristic imparting mechanism 30 is left and right. Since it shifts to either direction, the steering angle characteristic of the rear wheel 29 is a lateral translation of the characteristic shown in FIG. 4 and is asymmetrical to the left and right.

In such a case, loosen the tightening bolt 21e and remove the cover 21b.
If the front wheel 19 and the rear wheel 29 are both in the steering neutral position, the input shaft 31 rotates integrally with the cover 21b with respect to the driven rotating member 32, and the position of the follower 37 is set to the central groove portion 36a. Since the central position of the characteristic shown in FIG. 4 moves in the left-right direction, the characteristic of FIG. 4 also moves in parallel in the left-right direction. If the cover 21b is rotated and fixed by the tightening bolts 21e so that the position of the follower 37 is exactly in the center of the central groove 36a, the characteristics of the steering angle of the rear wheel 29 with respect to the front wheel 19 become bilaterally symmetrical. Such adjustments can be made very easily from the outside.

Further, in the present embodiment, since the servo valves 11 and 50 of the front and rear power steering devices are substantially the same, it is possible to reduce the manufacturing cost by sharing the parts.

In the modification shown in FIG. 7, a special washer 222 with a burr is used instead of the folding washer 21f. If the special washer with burrs 222 lightly abuts the cover 21b, screw the tightening bolt 221 with washer into the housing body 21a, adjust the neutral position, and then firmly tighten the tightening bolt 221. Projection 222
a bite locally on both sides of the long hole 21d, and tightening bolt 22
The rotation of the cover 21b when 1 is loosened is prevented. Also the 8th
In another modification shown in the figure, a special tightening bolt 321 having a locking screw portion 321a having a diameter slightly larger than the width of the long hole 21d at the base portion thereof.
Are using. The tip of the locking screw 321a is lightly covered 21
Attach the special tightening bolt 321 to the housing body so that it abuts b.
If the special tightening bolt 321 is strongly tightened after screwing it into the 21a and adjusting the neutral position, the locking screw part 321a is locally self-tapping on both sides of the long hole 21d, and the special tightening bolt 321 is loosened. In this case, the cover 21b is prevented from rotating.

[Brief description of drawings]

The attached drawings show an embodiment of a four-wheel steering system according to the present invention. Fig. 1 is a longitudinal sectional view of an essential part, Fig. 2 is a front view of a cover, and Fig. 3 is a sectional view taken along line III-III of Fig. 1. FIG. 4 is a diagram showing the operating characteristics, FIG. 5 is a schematic plan view of the whole, and FIG. 6 is a diagram showing a cross section in the circumferential direction including the tightening bolt about the rotation axis O2. FIG. 7 is a cross-sectional view near the tightening bolt on the surface including the rotation axis O2 of the modified example, and FIG. 8 is a cross-sectional view corresponding to FIG. 7 of a further modified example. Reference numeral 21 …… Housing, 21a …… Housing body, 21b …… Cover, 30 …… Steering characteristic imparting mechanism, 31 …… Input shaft, 32 ……
Driven rotary member, 35 …… Interlocking mechanism, 51 …… Output shaft.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bunro Ukai 1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd. (72) Inventor Akira Onishi 1-1-chome Asahi-cho, Kariya city, Aichi prefecture Co., Ltd. (72) Inventor, Ryo Oda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. An input shaft that rotates in conjunction with steering of front wheels,
A driven rotary member having a parallel rotary shaft center including a coaxial shaft with respect to the input shaft and connected to an output shaft for steering the rear wheels,
A four-wheel steering system comprising a steering characteristic imparting mechanism in a housing, the steering characteristic imparting mechanism including a interlocking mechanism that transmits the rotation of the input shaft to the driven rotary member with a predetermined characteristic that is bilaterally symmetrical with respect to a neutral steering position. Is a housing main body that supports the driven rotary member, and a cover that is fixed to the housing main body so as to be rotatable coaxially with the driven rotary member. In the state where the cover is loosened with respect to the housing main body, When the cover is rotated relative to the housing body, the input shaft is rotated together with the cover, and when the front wheels are steered while the cover is clamped and fixed to the housing body, the front wheels are The input shaft is rotatably supported by the cover so that the input shaft rotates relative to the cover in conjunction with the steering of the. A characteristic four-wheel steering system.