JPH0357774A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To reduce the dimension of the outer shape of a rear wheel power steering device by superposing the connection part at the top edge of a working shaft and an assistance delay avoiding mechanism in the axial direction, making the front and rear servovalves substantially same. CONSTITUTION:The boss part 58a of a yoke 58 which is serration-engaged at the top edge of the working shaft 52 of a rear wheel servovalve 50 is prevented from being slipped off by a nut 59 screwed with a screw part formed on the projection part 56a at the top edge of a torsion bar 56, and the dimension of the outer shape can be reduced, and the projection part in the radial direction can be reduced. Therefore, the boss part 58a is coaxially inserted into the second engaging boss 46, and the top edge of the working shaft 52 and an assistance delay avoiding mechanism 40 can be superposed in the axis line direction, and the length of a rear wheel power steering device 20 can be reduced, and the whole device can be made small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering device in which front and rear wheels are steered by front and rear power steering devices that operate in mechanically interlocked manner.

(Prior Art) In this type of four-wheel steering device, a rotary type servo valve is usually used for the front wheel power steering device, and a spool type servo valve is used for the rear wheel power steering device.

(Problem to be Solved by the Invention) The rear wheel power steering device, which operates mechanically in conjunction with the front wheel power steering device, has problems with the interlocking device when the rear wheels fall into a ditch and steering is blocked. In order to prevent the application of force, it is necessary to incorporate an assist delay avoidance mechanism. Furthermore, in order to reduce costs, it is desired to use the same servo valves at the front and rear. However, if the servo valve of the rear wheel power steering device is a rotary type, and the operating shaft that rotates together with the rotor valve member of this servo valve and the output rotation member of the assist delay avoidance mechanism are simply connected via a transmission member,
There is a problem in that the axial length of the rear wheel power steering device becomes long. Further, there is a problem in that the operating shaft and the output rotating member must be assembled with high precision so that they rotate about the same axis.

The present invention reduces the external size of the rear wheel power steering device by making the front and rear servo valves substantially the same, and overlapping the coupling portion at the tip of the operating shaft and the assist delay avoidance mechanism in the axial direction, and also facilitates assembly. The purpose is to

(Means for Solving the Problem) To this end, the four-wheel steering system according to the present invention, as illustrated in the accompanying drawings, includes a front-wheel power steering system 10 that steers the front wheels, and a front-wheel power steering system 10 that is mechanically interlocked with the steering of the front wheels. In a four-wheel steering system comprising a rear wheel power steering device 20 that operates to steer the rear wheels, the rear wheel power steering device 20 is rotatably supported within a housing 21 and rotates together with a rotor valve member 53. a hollow operating shaft 52 that moves; an output shaft 51 that is rotatably provided coaxially with the operating shaft and rotates together with the sleeve valve member 54; and an output shaft 51 that is coaxially provided within the operating shaft 52 and that rotates the stomach end A rotary type rear wheel servo valve 50 comprising a torsion bar 56 connected to the operating shaft 52 and the output shaft 51 in a relatively unrotatable manner, and the housing rotatable coaxially with the operating shaft 52. 21 and rotated mechanically in conjunction with the steering of the front wheels; and an input rotating member supported by the housing 21 so as to be rotatable in the axial direction coaxially with the input rotating member. An annular output rotating member 43 is interposed between the input rotating member 41 and the output rotating member 43, and when the torque transmitted between the two rotating members is less than a predetermined value, rotation of the input rotating member 41 is stopped. It is transmitted as it is to the output rotating member 43, but if the transmitted torque exceeds a predetermined value, it is bent and the input rotating member 4l
an assist delay avoidance mechanism 40 consisting of a spiral spring 44 that prevents the rotation of the output rotation member 43 from being transmitted to the output rotation member 43; and a boss portion 58a that is coaxially inserted into the output rotation member 43 and the spiral spring 44. , a yoke 58 is provided, the boss portion of which is fitted to the tip of the operating shaft 52 so as to rotate therewith, and is prevented from coming off, and a convex portion 58b is provided on one of the yoke 58 and the output rotating member 43; It is characterized in that a groove 43a is formed on the other side of the convex portion to engage with the convex portion in the rotational direction.

(Function) The operation of the front wheel power steering device is based on the assist delay avoidance mechanism,
It is transmitted to the rotor valve member of the servo valve via the convex part and the operating shaft. Misalignment between the output rotating member and the operating shaft is absorbed by the pin and groove. (Effects of the Invention) As described above, according to the present invention, the boss portion of the yoke and the tip end of the actuating shaft are inserted into the output rotating member and the spiral spring, and the coupling portion of the tip of the actuating shaft and the assist delay avoidance mechanism are connected to the axis. Since they can be overlapped in the direction, the external size of the rear wheel power steering device can be reduced in size. Furthermore, since the rotation of the output rotating member is transmitted to the operating shaft by the convex portion and the groove, there is no need to assemble the output rotating member and the operating shaft with high precision so that they are coaxial. Furthermore, since the front and rear servo valves can be made substantially the same, the manufacturing cost of the four-wheel steering system can be reduced.

(Example) The present invention will be explained below using examples shown in the accompanying drawings.

First, the overall structure of the four-wheel steering system will be explained with reference to the fJ2 diagram. A predetermined amount of working fluid sucked in from the reservoir 62 and sent out by the supply pump 60 driven by the engine 63 of the automobile is passed through the diversion valve 61. is divided at a predetermined ratio, 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 rotary type front wheel servo valve 11 provided in the middle of a handle shaft 16 that transmits rotation of a steering handle 15 to a rack and pinion mechanism 12 that converts rotation of a steering handle 15 into reciprocating motion of a front wheel operating rod 3, and a front wheel operating rod. l3
The front wheel power cylinder 14 provided in the front wheel is a main structural member. The front wheel servo valve l1 operates according to the steering wheel torque input from the steering wheel l5, and controls the supply and discharge of the working fluid supplied from the supply pump 60 to the left and right working chambers of the front wheel power cylinder l4 via the diverter valve 61. The amplified steering force is outputted to the front wheel operating rod 13, and the left and right front wheels 19 are steered via the tie rod l7 and knuckle arm 18 provided at both ends of the rod.

As shown in the construction drawings and FIG. 2, 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 avoidance mechanism 40. ing. The rear wheel power cylinder 24 is connected to the housing 2 of the rear wheel power steering device 20.
1, and a piston 26 that is fluid-tightly fitted into 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 a T# cylinder. @〆It protrudes from both ends of the cylinder 25 in a fluid-tight and slidable manner. A rear wheel operating rod 23 is located between both sides of the piston 26 and the inner surface of the end of the cylinder 25.
A pair of return springs are provided to return the rear wheel to the neutral position shown, and both ends of the rear wheel operating rod 23 are connected to the rear wheel 29 via a tie rod 27 and a knuckle arm 28.
As shown in FIGS. 1 and 3, the steering characteristic imparting mechanism 30
are rotational axes 01 and 02 eccentric to each other by a distance A.
It is composed of an input shaft 31 and a driven rotating member 32 that are rotatably supported in the housing 21, and an interlocking mechanism 35 that includes a guide groove 36 and a follower 37.

The follower 37 includes a support pin fixed to the driven rotation member 32 eccentrically by a distance B from the rotation axis 02, and a roller rotatably supported by the support pin. Further, the guide groove 36 includes a central groove portion 36 formed on the rear end surface of the input shaft 3l.
a and a pair of outer grooves 36 extending in an inverted eight shape from both ends thereof.
In the illustrated neutral state, the follower 37 is located exactly in the middle of the central groove 36a.

As shown in Figure 2, the cable length adjustment device 6 is located in the middle part.
The pair of operation cables 65a and 65b provided with the number 6 are made of an inner wire and an outer tube, one end of each inner wire is connected to a protrusion provided at both ends of the front wheel operating rod 13, and the other end of each inner wire is connected to the input shaft 31. The front wheel operating rod 1 is wound around the formed pulley 31a.
The input shaft 3 is rotated in accordance with the reciprocating motion of the input shaft 3. Both ends of each outer tube are connected to a housing (not shown) of a front wheel power steering device 10 and a housing 2, respectively.
It is attached to 1.

The rear wheel servo valve 50 is provided in the housing 21 coaxially with the driven rotating member 32 of the steering characteristic imparting mechanism 30, with an assist delay avoidance mechanism 40 (described later) interposed therebetween, mainly as shown in the first construction drawing.

The output shaft 51 and the hollow operating shaft 52 of the rear wheel servo valve 50 are coaxially supported in the housing 21 so as to be rotatable relative to each other, and a torsion bar is provided coaxially within the operating shaft 52.
56 has one end connected to the tip of the actuating shaft 52 by a locking pin 57, and the other end connected to the output shaft 51 through serrations. A binion 22 formed at the rear of the output shaft 5l meshes with a rank 23a formed on the rear wheel operating rod 23. A boss portion 58a of a yoke 58 is fitted into the serration portion 52a at the front end of the operating shaft 52 so as to rotate together with the serration portion 52a. By bringing the stepped portion 58c of the yoke 58 into contact with the shoulder portion 52b formed on the operating shaft 52, and tightening the nut 59 and the spacer 59a which are screwed into the threaded portion formed on the protruding portion 56a at the tip of the torsion bar 56. , the yoke 58 is fixed to the actuating shaft 52. The yoke 58 is connected to the driven rotating member 32 via an assist delay avoidance device fR40, which will be described later.

The main part of the rear wheel servo valve 50 is a 4-port throttle switching valve consisting of a rotor valve member 53 formed as a part of the operating shaft 52 and a sleeve valve member 54 connected to the output shaft 5l by a pin 55. As mentioned above, the tip of the actuating shaft 52 and the protrusion 56a are clamped using a jig, and the actuating shaft 52 and the output shaft 5 are separated.
The operating shaft 52 and torsion bar 56 are connected by a locking pin 57 after adjusting the relative rotation angle of step 1 so that the phase relationship between the rotor valve member 53 and the sleeve valve member 54 is in a neutral state. . 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 O, the operating flow supplied from the supply pump 60 to the input boat 50a via the diverter valve 61 is The liquid is discharged as it is from the discharge port 50b to the reservoir 62. However, if the input torque applied to the actuating shaft 52 increases and the torsion bar 56 twists, causing relative rotation between the valve members 53 and 54, the input boat 50a will change depending on the direction and relative rotation angle. The working fluid supplied to the rear wheel power cylinder 24 is introduced into one working chamber of the rear wheel power cylinder 24 from either one of the two distribution ports 50c, 50d, and the working fluid in the other working chamber is introduced from the other distribution port to the discharge port 50b. The fuel is then discharged to a reservoir 62 to generate a steering assist force to the rear wheels 29.

The front wheel servo valve l1 is completely the same as the rear wheel servo valve 50, except that the protruding portion 56a at the tip of the torsion bar 56 is removed after being connected by the locking pin 57, and its operating axis is the serration at the tip. The pinion at the tip of the output shaft forms part of the rack and pinion mechanism 12.

As shown in FIG. 1, the assist delay avoidance mechanism 40 is rotatably supported by the housing 21 coaxially with the input rotating member 41 integrated with the driven rotating member 32 and the rear wheel servo valve 50 with a space between them in the axial direction. It has an annular intermediate rotating member 42 and an output rotating member 43, respectively. Each rotating member 4
1. On the inner periphery of 43 are cylindrical first and second engagement bosses 45.
, 46 are coaxially supported, and a spiral spring 44 is wound around the outer periphery of each engagement boss 45, 46. Each spiral spring 44
41, 42. are connected to each rotary member 41, 42. with the initial torque applied, with the inner end via the respective engagement boss 45, 46 and the outer end directly. 43 is engaged with the inside and outside. In this assist delay avoidance mechanism 40, when the torque transmitted between the two rotating members 41, 43 is less than the initial torque of each spiral spring 44, the rotation of the input rotating member 41 is directly transmitted to the output rotating member 43. If the transmitted torque exceeds this value, each spiral spring 44 is bent and the input river turning member 41
This prevents the rotation of the output rotating member 43 from being transmitted to the output rotating member 43.

The boss portion 5 of the yoke 58 is fitted into the serration portion 52a at the tip of the operating shaft 52 and fixed by tightening with a nut 59.
8a is coaxially inserted into the second engagement boss 46.

A pin 58b is embedded in the outward flange at the rear end of the boss portion 58a in the radial direction, and the pin 58b is engaged in the rotational direction in a groove 43a formed in the output rotation member 43 in the radial direction.

The rotation of the output rotation member 43 can be smoothly transmitted to the operation shaft 52 even if there is a misalignment between the output rotation member 43 and the operation shaft 52 due to the pin 58b and the groove 43a.

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

When the steering wheel l5 is rotated clockwise from the neutral position as shown by the arrow in FIG. Steering the front wheels 19 to the right.

As a result, the input lever 31 of the steering characteristic imparting mechanism 30 is rotated in a counterclockwise direction when viewed from behind via the operation cables 65a and 65b. Conversely, if you turn the steering wheel l5 counterclockwise, each part will operate in the opposite direction to the above and move forward! 19 is steered leftward, and the input shaft 31 is rotated clockwise when viewed from the rear. Such an input i[113
Due to the rotation of input shaft 3, the guide groove 36 also rotates counterclockwise or clockwise around the rotation axis ○l from the neutral position shown in FIG. 3
7 remains in the central groove 36a, the follower 37 does not move from the neutral position shown. However, if the rotation angle of the input shaft 31 becomes large and the follower 37 enters the outer groove portion 36b,
The follower 37 is pushed by the outer groove portion 36b and the driven rotating member 3
2 rotates about the rotation axis 02 in the same direction as the input shaft 31, so the driven rotating member 32 rotates in the same direction as the input shaft 3.
It rotates with the characteristics shown in FIG. 4 for a rotation angle of 1.

Under normal conditions, the rear wheel steering torque is small, so the assist delay avoidance mechanism 40 does not operate, and the driven rotating member 32
The rotation is directly transmitted from the yoke 58 to the operating shaft 52 to operate the rear wheel servo valve 50.6 If the front wheel 19 is steered to the right, the input shaft 31, the operating shaft 52 of the rear wheel servo valve 50, and the output shaft 51 rotates counterclockwise when viewed from the rear, 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 steering torque, and the working fluid is supplied from the supply pump 60 via the flow dividing valve 6l to the rear wheel power cylinder 24.
The assist force is applied to the rear wheel operating rod 23 by controlling supply and discharge to the left and right working chambers.

When the front wheel 19 is steered to the left, each part operates in the opposite direction to the above, and 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 characteristics of the steering angle of the rear wing 29 with respect to the front wing 19 are similar to the rotation angle of the driven rotating member 32. Similarly, the fourth
The characteristics are as shown in the figure. That is, the rear wheels 29 are steered in the opposite phase as shown in the characteristics of FIG. 4 in response to the steering of the front wheels 19.

If the rear wheel 29 is unable to be steered due to falling into a groove, etc., and the rear wheel gear 9 is largely steered using the steering wheel 15, the rear wheel steering torque tends to increase, but each spiral spring 44 Since the cables 65a and 65b are bent, there is no fear that excessive force will be applied to each of the operating cables 65a, 65b and cause damage.

According to the embodiment described above, the boss portion 58a of the yoke 58 that is serrated engaged with the tip of the operating shaft 52 of the rear wheel servo valve 50 is the protruding portion 56 at the tip of the torsion bar 56.
Since it is prevented from coming off by a nut 59 screwed into the threaded part provided in a, its external size is small and there is no protrusion in the radial direction. Therefore, the boss portion 58a is connected to the second engagement boss 46.
Since the tip of the actuating shaft 52 and the assist delay avoidance device 140 can be overlapped in the axial direction,
The length of the rear wheel power steering device 20 can be shortened and the size can be reduced. In addition, since the front and rear servo valves 11 and 50 can be the same except for the final stage of the manufacturing process,
The manufacturing cost of the 411k steering system can be reduced by using common parts.

In the above embodiment, the nut 59 is screwed onto the threaded part provided on the protruding part 56a of the torsion bar 56 to prevent the boss part 58a of the yoke 58 from coming off.
An annular groove may be provided on the outer periphery of the boss portion 58a, and a snap ring may be engaged with the annular groove to prevent the boss portion 58a from coming off.

Further, as shown in FIG. 5, the yoke 70 is fitted into the serration portion 52a of the actuating shaft 52, and a part of the yoke 70 is caulked with the stepped portion 71 of the yoke 70 in contact with the shoulder portion 52b of the actuating shaft 52. The yoke 70 may be fixed to the operating shaft 52 by engaging this caulked portion into the recess 52c of the operating shaft 52.

Furthermore, as shown in FIG. 5, a pin 72 may be attached to the output rotating member 43 parallel to the operating shaft 52, and this pin 72 may be engaged with a groove 73 formed in the radial direction of the yoke 70.

[Brief explanation of drawings]

The attached drawings show an embodiment of the four-wheel steering system according to the present invention, in which Fig. 1 is a vertical sectional view of the main parts, Fig. 2 is a schematic plan view of the whole, and Fig. 3 is a cross section of Fig. 1. FIG. 4 is a diagram showing the operating characteristics. FIG. 5 is a partial sectional view of a modified embodiment. Explanation of symbols 10... Front wheel power steering device, 20... Rear wheel power steering device, 21... Housing. 40... Assist delay avoidance mechanism, 41... Input rotating member, 43... Output rotating member, 43a... Groove, 44... Spiral spring. 5
0... Rear wheel servo valve, 51... Output shaft, 52...
Operating shaft, 53...Rotor valve member, 54...Sleeve valve member, 56...Torsion bar 56a...Protrusion part, 58...Yoke, 58a...Boss part, 58
b...Pin (protrusion).

Claims (1)

[Scope of Claims] A four-wheel steering device comprising: a front wheel power steering device that steers the front wheels; and a rear wheel power steering device that operates mechanically in conjunction with the steering of the front wheels to steer the rear wheels; The rear wheel power steering device includes a hollow operating shaft that is rotatably supported within a housing and rotates together with the rotor valve member, and a hollow operating shaft that is rotatably provided coaxially with the operating shaft and rotates together with the sleeve valve member. a rotary type rear wheel servo valve comprising an output shaft, a torsion bar provided coaxially within the operating shaft and having both ends connected to the operating shaft and the output shaft in a relatively non-rotatable manner; and the operating shaft. an input rotating member that is supported by the housing so as to be rotatable coaxially with the housing and rotated mechanically in conjunction with the steering of the front wheels; an annular output rotating member supported by the housing; and an annular output rotating member interposed between the input rotating member and the output rotating member, and when the torque transmitted between the two rotating members is less than a predetermined value, the input rotating member rotates. an assist delay avoidance mechanism comprising a spiral spring that transmits the rotational motion of the input rotational member as is to the output rotational member, but bends when the transmission torque exceeds a predetermined value to prevent rotation of the input rotational member from being transmitted to the output rotational member; A yoke having a boss portion coaxially inserted into the output rotating member and the spiral spring, and the boss portion is fitted to the tip of the operating shaft so as to rotate together with the yoke to prevent removal. A four-wheel steering device, characterized in that one of the yoke and the output rotating member is provided with a convex portion, and the other is provided with a groove that engages with the convex portion in the rotational direction.