JPH0345473A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To obtain always favorable rear wheel steering properties with a simple structure by installing a steering property giving mechanism, which is operated according to the output of a front wheel steering device, between input and output shafts positioned on the same axis inside the housing of a rear wheel steering device. CONSTITUTION:A rear wheel power steering device 20 has a rear wheel servo valve 50 for limitting the supply and exhaust of pressure oil for a rear wheel power cylinder, and is equipped with a steering property giving mechanism 30 and an assist delay avoiding mechanism 40 on the axis same as the output shaft 51. The steering property giving mechanism 30 has an eccentric shaft 32 coupled with the rear side of an input shaft 31 to which the steering motion of a front steering device is transmitted through operation cables 65a and 65b, and it makes a driving gear 34 (the number of teeth, n), which is supported freely in rotation by the eccentric shaft 32, engage with the inner tooth gear(the number of teeth, n+1) of a following rotation member 33 opposed to the input shaft 31. A locking pin 36 projecting at the driving gear 34 locks in a guide groove 37 in the radial direction, being formed at the inner end face of a housing 31.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a front wheel steering device and a rear wheel steering device via a pair of wires to steer the rear wheels according to the steering angle of the front wheels. This invention relates to a four-wheel steering system.

(Prior art) As this type of four-wheel steering device, for example,
No. 52,578, this technology includes a complicated coupling mechanism and drive mechanism in order to change the rear wheel steering characteristics according to the vehicle speed.

(Problem M to be solved by the invention) For this reason, the above-mentioned conventional technology has an extremely structure as a whole!
! It gets messy. The present invention solves these problems and obtains the necessary rear wheel steering characteristics with a simple structure.
% fist rafu 艷 n ding 1 ° Hatake Shito 4 ^ 6 So 9 Kunershi the 1 no exclusive 9wL-Renigo-like.

(Means for Solving the Problems) For this purpose, the four-wheel steering device according to the present invention has a front wheel steering device 1 that steers the front wheels, as illustrated in FIGS. 1 to 4.
0, and a rear wheel steering device 20 that steers the rear wheels. , in a four-wheel steering device comprising an output shaft 51 connected to the input shaft to steer the rear wheels in conjunction with the front wheels, the input shaft 31 and The output shafts 51 are rotatably arranged and supported in the axial direction, and an eccentric shaft 32 is fixedly provided at the end of the input shaft 31, and the eccentric shaft 32 is coaxially opposed to the input shaft 31 with the eccentric shaft in between. a driven rotating member 33 connected to the tip side of the output shaft 51; a drive gear 34 rotatably supported by the eccentric portion 32a of the eccentric shaft 32; and a drive gear 34 fixed near the pitch circle of the drive gear. an engagement pin 36 that protrudes parallel to the eccentric shaft 32 and whose distal end engages with a guide m37 formed along a radial direction in a part of the rear wheel side housing 21; and teeth larger than the drive gear 34. an internal gear 3 having a number of internal teeth, which is provided integrally and coaxially with the driven rotating member 33 and meshes with the driving gear;
Added steering characteristics consisting of 5! The lfi structure 30 is provided.

(Function) In the front wheel steering neutral state, the center of the eccentric portion 32a is
It is located in the direction of the engagement pin 36 engaged with the guide groove 37. As the front wheels are steered from this state and the eccentric shaft 32 rotates according to the front wheel steering angle, the drive gear 34 revolves around the center of the eccentric shaft 32 and the engagement pin 36 that is engaged with the guide groove 37 rotates. Due to the action, it initially rotates in the opposite direction,
It then rotates in the same direction as its revolution. Therefore, drive gear 3
The internal gear 35 meshing with the eccentric shaft 32 rotates at an angular velocity of O at first, but as the eccentric shaft 32 rotates, the angular velocity increases continuously. The output shaft 51 to which the driven rotating member 33 to which the internal gear 35 is integrally fixed also rotates in the same way as the internal gear 35, so when the front wheels are steered from the neutral steering position, the rear wheels are initially is the steering angular velocity (O), and the vehicle is steered so that it increases continuously as the front wheel steering angle increases.

(Effects of the Invention) As described above, according to the present invention, the steering angle of the rear wheels is approximately at fO when the front wheels are near the neutral steering position, and increases continuously as the front wheel steering angle increases. Therefore, when driving at high speeds with a small front wheel steering angle, the rear wheels are hardly steered.
Favorable rear wheel steering characteristics can be obtained in which the rear wheel steering angle increases during low speed driving where the front wheel steering angle becomes large. Also, steering characteristics added 8! The structure has a small number of parts, and each part has a relatively simple shape, so it is easy to manufacture, and the manufacturing cost only increases slightly.

(Example) The present invention will be explained below using examples shown in FIGS. 1 to 4.

As shown in FIG. 2, in this embodiment, power steering devices are used as the front wheel and rear wheel steering devices 10 and 20, respectively. A predetermined amount of working fluid sucked in from a reservoir 62 and sent out by a supply pump 60 driven by an automobile ennon 63 is divided at a predetermined ratio by a diversion valve 61, one of which is supplied to the front wheel power steering device 10. , the other is supplied to the rear wheel power steering device 2o,
After use, the working fluid is returned to the reservoir 62.

The front wheel power steering device j7It10 includes a known rotary type front wheel servo valve 11 provided in the middle of a handle shaft 16 that transmits the rotation of the steering handle 15 to a luff/coubinion mechanism 12 that converts the rotation of the steering handle 15 into reciprocating motion of the front wheel operating rod 13. The front wheel power sill 14 provided on the front wheel operating rod 13 is the main W component. The front wheel servo valve 11 operates according to the steering wheel torque input from the steering wheel 10, and controls the supply and discharge of working fluid supplied to the left and right working chambers of the front wheel power cylinder 14 from the supply pump 60 via the flow dividing valve 61. The amplified steering force is applied to the front wheels. +1
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■=bel1wcurnwl''-J-The left and right front wheels 19 are steered via tie rods 17 and knuckle arms 18.

As shown in FIGS. 1 and 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 driven rotating member 33, an output rotating member 45, and a steering characteristic imparting member. A mechanism 30 and an assist delay avoidance mechanism 40 are provided. Steering characteristics added 8! The input shaft 31 of the mechanism 30 and the output shaft 51 of the rear wheel servo valve 50 are installed in the rear wheel housing 21 (see FIG. 1) through bearings, and are relatively rotatable around a common rotation axis #aO. The other members 50, 24, 30° 33 are supported at intervals in the direction.
．． 40 and 45 are also provided within the rear wheel side housing 21. A pair of operating cables 65a and 65b each having a cable length adjustment device 66 in the middle thereof are made of an inner wire and an outer tube, and one end of each inner wire is connected to a protrusion provided at both ends of the front wheel operating rod 13, respectively.
The other end of each inner wire is attached to a pulley 3 formed on the input shaft 31.
1a, and rotates the output shaft 31 in accordance with the reciprocating motion of the front wheel operating rod 13. Although not shown, both ends of the seven ends of each of the operating cables 65a and 65b are attached to a housing (not shown) of the front wheel power steering device 10 and a rear wheel side housing 21, respectively. Note that each of the operating cables 65a, 65& does not have an outer tube, but is stretched between each protrusion of the front wheel operating rod 13 and the pulley 31a through a plurality of intermediate pulleys (not shown) provided on the vehicle body. Good too.

The steering characteristic imparting mechanism 30 is provided within the front end portion of the rear wheel housing 21. As shown in Figures 1 and 3,
An eccentric shaft 32 is coupled to the rear side of the input shaft 31 via a key, and a driven shaft coaxially faces the input shaft 31 with the eccentric shaft 32 in between. The rotating member 33 is a servo valve 501 which will be described later.
6 and an assist delay avoidance fi mechanism 40.

The eccentric portion 32a formed in a part of the eccentric shaft 32 is connected to the input shaft 31.
A drive gear 34 having seven teeth is rotatably supported on this eccentric portion 32a. An engagement pin 36 is fixed to this drive gear 34 and projects forward from near the pitch circle in parallel with the eccentric shaft 32. The guide member 37 is substantially movably engaged with a guide member 37 formed along the radial direction on a part of the inner end surface of the wheel housing 21 . On the other hand, on the @ side of the driven rotating member 33, an internal gear 35 having eight teeth that meshes with the drive gear 34 is coaxially and integrally formed. In this embodiment, as mainly shown in FIG. 3, a fairly large gap is provided between the tooth surfaces of both gears 34 and 35, which is the same in both rotational directions in the neutral state.

In the front wheel steering neutral state, as shown in FIG. From this state, the front wheel 19
is steered, and as the input shaft 31 and the eccentric shaft 32 rotate in response to an increase in the front wheel steering angle, the drive gear 34
1st turn @MI line O in 71"A 5-Eggplant 4 line 2 line etc. -As the engagement pin 36 fixed to the Utasen 1 gear 34 slides along the guide groove 37, , drive gear 34
also rotates around its central axis 0. The direction of this rotation is initially opposite to the revolution, but as the eccentric shaft 32 rotates, the angular velocity gradually decreases, and when the rotation angle of the eccentric shaft 32 passes a position of slightly less than 90 degrees, the direction becomes the same as that of the revolution, and the angular velocity gradually increases. The internal gear 35 that meshes with the drive gear 34 is
If the drive gear 34 only revolves, it will rotate in the same direction as the revolution with a reduction ratio of 8, and if the drive gear 34 only rotates, it will rotate in the same direction as the revolution with a reduction ratio of 7/8. . In this embodiment, the range of the rotation angle of the input shaft 31 is approximately 210 degrees left and right from the neutral position shown in the figure, and as described above, there is a considerable gap between the two gears 34 and 35. Therefore, the characteristics of the rotation angle of the driven rotating member 33 with respect to the rotation angle of the input shaft 31 are as shown in FIG.
Until the rotation angle of the input shaft 31 is small and both gears 34 and 35 adjacent to the engagement pin 36 come into contact, the driven rotating member 33
does not rotate, but both gears jJ, i-2, etc.
+The rotation angle of the driven rotating member 33 increases as the number of frost increases.

As shown in FIG. 1, the driven rotating member 33 has a thin cylindrical box shape consisting of two parts, front and rear, and an output rotating member 45 is supported coaxially and relatively rotatably in the rear half of the box. A rear end portion of the output rotation member 45 that protrudes rearward from the rear wheel is coupled to a front end portion of an operating shaft 52 of a rear wheel servo valve 50, which will be described later, via a speed increasing mechanism 46. Speed increase 8! Structure 46
The first gear 47 is fixed to the rear end of the output rotating member 45 via a key and a ring nut, and the intermediate shaft 48 is fixed to the rear wheel housing 7 ring 21 in parallel with the rotating shaft #IO. Consisting of second and tItJ3 gears 48a, 48b and a fourth gear 49 splined to the front end of the actuation@52, the first and second gears 47.48a and the third and PjI
The J4 gears 48b and 49 are meshed with each other, and the overall speed increasing ratio is 6.

This speed increasing mechanism 46 causes the operating shaft 52 of the rear wheel servo valve 50 to
The rotation angle is approximately the same as the rotation angle of the input shaft 31.

As shown in FIG. 1, the assist delay avoidance machine VT40 provided between the driven rotating member 33 and the output rotating member 45 includes a spiral coil h41 and an engagement boss 42 coaxially and rotatably provided on the output rotating member 45. The central shaft 43 coaxially fixed to the output co-rotating member 45 is the main component, and both rotating members 3
When no torque is applied between 3.45 and 45,
The spiral flaps 41 are provided with an initial torque so that both ends of the spiral flaps 41 are simultaneously engaged with parts of both rotating members 33, 45, respectively. That is, the inner end of the spiral spring 41 engages with the engagement boss 42 from one direction in the circumferential direction, and the forward and inward protrusions 42a and 42b provided on the engagement boss 42 simultaneously engage the driven rotation member 33. Semicircular recess 33 formed on the rear surface
a and a semicircular notch 43a formed at the front end of the central shaft 43.
is engaged with the end face from one direction in the circumferential direction. Further, the outer ends of the spiral flaps 41 are simultaneously engaged with protrusions 33b and 45a formed on the respective outer peripheries of both rotating members 33, 45 from opposite directions in the circumferential direction.

According to the upper beat assist delay avoidance mechanism 40, when the transmitted torque between the driven and output rotating members 33, 45 is less than the initial torque of the spiral spring 41, the rotation of the driven rotating member 33 is limited to that level. ) The rotation of the driven rotation member 33 is transmitted to the output rotation member 45, but if the transmission torque exceeds the initial torque, the assist delay avoidance mechanism 40 is activated, that is, the spiral flap 41 is bent, and the rotation of the driven rotation member 33 is transmitted to the output rotation member 45. It disappears.

As shown in FIG. 2, the rear wheel power cylinder 24 includes a cylinder 25 formed in the rear wheel housing 21, and a piston that is fluid-tightly fitted into the cylinder 25 and separates the inside thereof into left and right working chambers. 26, the rear wheel operating rod 23
is fixed to the piston 26, and its both ends protrude from both ends of the cylinder 25 in a fluid-tight and slidable manner. A pair of return levers for returning the rear wheel operating rod 23 to the illustrated position are provided between both side surfaces of the piston 26 and the inner surfaces of both ends of the cylinder 25, and both ends of the rear wheel operating rod 23 are connected to the tie rod 27 and the knuckle 7. -If 291.
Totogami et al. The f-color rotary type rear wheel servo valve 50 is provided in the rear wheel side housing 21 coaxially with the assist delay avoidance fi 140, mainly as shown in FIG. The output shaft 51 and the hollow operating shaft 52 of the rear wheel servo valve 50 are coaxially supported by the rear wheel housing 21 and connected to each other by a torsion bar 56 so as to be relatively rotatable. A binion 22 formed at the rear of the output shaft 51 meshes with a rack 23a formed on the rear wheel operating rod 23, and a fourth gear 49 of a speed increasing mechanism 46 is spline-coupled to the front end of the operating shaft 52. The rotor valve member 53 of the rear wheel servo valve 50 is formed in a part of the operating shaft 52, and the inner and outer circumferences of the sleeve valve member 54 of the rear wheel servo valve 50 are the outer circumference of the rotor valve member 53 and the rear wheel housing 21, respectively. It is rotatably fitted on the inner periphery and connected to the output shaft 51 via the pin 55. These two valve members 53 and 54 form an open center type 4-port throttle switching valve, and when the input torque applied to the operating shaft 52 is 0, the rotor valve member 5
1 when the relative surface movement angle between 3 and the sleeve valve member 54 is 0;
Input capo) 50 from the supply pump 60 via the branch valve G1
The working fluid supplied to a is directly discharged from the discharge boat 50b to the reservoir 62. However, the operating shaft 52
If the input torque applied to the input boat 50a increases and a relative rotation occurs between the two valve members 53, 54, the working fluid supplied to the input boat 50a is divided between the two distribution boats depending on the direction and relative rotation angle. 50c, 50d is introduced into one working chamber of the power cylinder 24, and the working fluid in the other working chamber is discharged from the other distribution boat to the reservoir 62 via the discharge boat 50b, and then to the rear wheel 29. The steering force is amplified.

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

When the steering wheel 15 is rotated clockwise as shown by the arrow in FIG. One of the left and right front wheels is steered to the right via the knuckle arm 18. At the same time, the inner wires of the operating cables 65a and 65b move in the direction shown by the arrow to control the rear wheel power steering device 20.
a and the input shaft 31 are rotated in a counterclockwise direction when viewed from the rear in response to the steering of the front wheels 19. When the steering wheel 15 is rotated counterclockwise in the opposite direction to the arrow, each part operates in the opposite direction to the above, the front wheel 19 is steered to the left, and the pulley 31a and input shaft 31 are rotated in a clockwise direction when viewed from the rear. be done.

No matter which direction the input shaft 31 is rotated, the driven rotating member 33 does not rotate while the rotation angle of the input shaft 31 is small, as described above, and after that, the angular velocity increases according to the rotation of the input shaft 31. gradually increases from 0 and rotates in the same direction. In a normal state, the torque transmitted between the driven rotating member 33 and the output rotating member 45 is small, so the assist delay avoidance device VT40 does not operate, and the rotation of the driven rotating member 33 is directly transmitted to the output rotating member 45. , the rear wheel servo valve 50 is operated via the speed increasing mechanism 46. If the front wheels 19 are steered to the right from the neutral steering state and the input shaft 31 is rotated in the same counterclockwise direction when viewed from the rear, the rear wheels pass through the steering characteristic imparting mechanism 30, the assist delay avoidance device VT40, and the speed increasing mechanism 46. The operating shaft 52 and output shaft 51 of the wheel servo valve 50 also rotate in the counterclockwise direction, and the rear wheel operating rod 23 is moved rightward as shown by the arrow via the rack 22 and the pinion 23a. *
At this time, the rear wheel servo valve 50 operates according to the operating torque input to the operating shaft 52, and the working fluid from one distribution valve 50c is supplied to the left working chamber of the rear wheel power cylinder 24. The rightward steering force generated on the rear wheel operating rod 23 is amplified. The left and right rear wheels 29 are steered leftward in response to rightward steering of the front wheels 19 via tie rods 27 and knuckle arms 28 provided at both ends of the rear wheel operating rod 23. Furthermore, if the front wheels 19 are steered to the left, each part operates in the opposite direction to the above, and the two rear wheels are steered to the right. With the operation of the rear wheel servo valve 50, the operating shaft 5
2 and the output shaft 51 rotate relative to each other in proportion to the operating torque, but the relative rotation angle is small, so the characteristics of the steering angle of the rear wheels 29 with respect to the steering angle of the front wheels 19 are
As with the rotation angle, the characteristics are as shown in FIG. That is, the rear wheels 29 are not steered near the front wheel steering neutral position, but if the front wheel steering angle becomes larger than a predetermined value, the steering angular velocity of the rear wheels 29 increases continuously from around 0 in response to the front wheel steering. It is steered in the opposite phase.

As described above, according to the above embodiment, when the front wheels 19 are running at high speeds with a small steering angle, the two rear wheels are hardly steered and are held in the middle state, and when running at low speeds when the front wheels have a large steering angle, the rear wheels A favorable rear wheel steering characteristic is obtained in which the steering angle is increased.

Note that the engagement pin 36 does not need to be provided exactly on the pitch circle of the drive gear 34, but may be provided near the pitch circle, and in the above embodiment, it is not necessary to provide a gap between the two gears 34 and 35. Although the dowel pin 36 was engaged with the guide groove 37 without substantial interference, even if the gap between both gears 34 and 35 was made smaller and the gap between the engagement pin 36 and the guide groove 37 was increased. often,
Alternatively, if the position of the engaging pin 36 is appropriately selected, the backlash can be reduced to substantially zero.

Note that when the rear wheel 29 has fallen into a groove or the like and its steering is blocked, rotation of the output shaft 51 is also blocked, so if the rotation angle of the steering handle 15 is increased, the output shaft 51 and the operating shaft are The stopper between the actuating shafts 52 immediately comes into contact with each other, and the rotation of the actuating shaft 52 is also prevented. In this state, if the rotation angle of the steering handle 15 is increased further, the driven rotating member 33 will rotate further, but this rotation is caused by the spiral spring 41.
Therefore, an unreasonable force exceeding that due to the spring force of this spiral spring 41 is absorbed by the deflection of each operating cable 65a, 6.
It does not join the inner wire of 5b. Therefore, there is no risk of each inner wire being stretched or damaged. The initial torque of the spiral coil h41 is set to be as large as possible within a range that does not interfere with the above operation.

Note that the present invention can also be implemented using front and rear wheel steering devices that do not rely on a power steering device.

[Brief explanation of drawings]

1 to 4 show an embodiment of a four-wheel steering system according to the present invention, in which FIG. 1 is a vertical cross-sectional view of the main part, FIG. 2 is a schematic plan view of the whole, and FIG. FIG. 4 is a cross-sectional view showing the operating characteristics. Explanation of symbols 10... Front wheel steering device (front wheel power steering device), 2
0... Rear wheel steering device (rear wheel power steering device), 21
... Rear wheel side housing, 30... Steering characteristic imparting mechanism, 31... Input shaft, 31a... Pulley, 32...
Eccentric shaft, 32a... Eccentric portion, 33... Driven rotating member, 34... Drive gear, 35... Internal gear, 36...
・Engagement pin, 37... Guide groove, 51... Output shaft, 6
5a, 65b...operation cable.

Claims (1)

[Claims] A front wheel steering device includes a front wheel steering device that steers the front wheels, and a rear wheel steering device that steers the rear wheels, and the rear wheel steering device includes an input shaft to which the operation of the front wheel steering device is transmitted via a pair of operating cables and a pulley. In a four-wheel steering device comprising an output shaft connected to the input shaft to steer the rear wheels in conjunction with the front wheels, the input shaft and the output shaft are respectively rotated within a rear wheel side housing of the rear wheel steering device. an eccentric shaft arranged and supported in the axial direction and fixedly provided at the distal end of the input shaft; A connected driven rotating member, a drive gear rotatably supported by the eccentric portion of the eccentric shaft, and a drive gear fixed near the pitch circle of the drive gear and protruding parallel to the eccentric shaft, with a tip end facing the rear wheel. an engagement pin that engages with a guide groove formed along a radial direction in a part of the housing; and an engagement pin that has a larger number of teeth than the drive gear and is provided integrally and coaxially with the driven rotation member. A four-wheel steering device comprising a steering characteristic imparting mechanism comprising an internal gear meshing with a drive gear.