JPH0798491B2 - Rear wheel steering system for front and rear wheel steering vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering system for a front-rear wheel steering vehicle that can steer the rear wheels of a vehicle in conjunction with a steering operation of the front wheels.

[Prior art]

In this type of rear wheel steering device, a rotating shaft that rotates in response to a steering operation of a front wheel is connected to an operating rod of a rear wheel side steering link mechanism, and the operating rod moves in the axial direction in accordance with the rotation of the rotating shaft. Conventionally, for example, a device provided with a connecting mechanism that is displaced to steer the rear wheels to the in-phase side when the front wheels have a small steering angle and to steer the rear wheels to the anti-phase sides when the front wheels have a large steering angle has been proposed. It is proposed in Japanese Laid-Open Publication No. 61-9374.

Then, in the device proposed in the publication,
The coupling mechanism is rotatably assembled to a housing that is assembled to a vehicle body, is coupled to the rotary shaft, has an eccentric shaft at a rear end thereof, and is rotated by the rotary shaft; A tubular member that is rotatably assembled on an eccentric shaft and integrally includes a pinion in the front part and an eccentric cam in the rear part,
The internal gear fixed to the housing and engaged with the pinion, and the eccentricity that is rotatably assembled on the eccentric cam of the tubular member and is slidably guided in the vertical direction by a guide member provided on the operating rod. A slider is provided for transmitting the movement of the cam to the operating rod as a displacement in the axial direction. Therefore, in the same device, the rotation of the input shaft combines the two motions of the eccentric cam, the revolution and the rotation, to be transmitted to the slider, and the slider moves to the operating rod in the left-right direction in the combined motion. Only the rear wheel is steered.

[Problems to be solved by the invention]

By the way, in the above-mentioned conventional device, by combining various tooth ratios of the pinion and the internal gear and the eccentric amount of the eccentric cam, the rear wheel rotation with respect to the front wheel steering angle corresponding to the characteristics of the vehicle that differs depending on the vehicle type. Although the rudder angle can be set, when setting the gear ratio, it is not possible to set steplessly in a limited space due to restrictions in gear manufacturing such as modules. It is difficult to set the optimum rear-wheel steering angle commensurate with the above in a limited space.

When setting the neutral position where the front-rear turning angle is zero, the axis of the input shaft, the axis of the eccentric shaft and the pinion, the center of the eccentric cam, and the center of the internal gear are arranged on the same line in the vertical direction. After that, the eccentric cam and the slider must be connected, which requires high manufacturing and assembling accuracy, resulting in high manufacturing cost.

There is a problem such as.

[Means for solving problems]

In order to address such a problem, the present invention relates to the above-mentioned rear wheel steering system for a front-and-rear wheel steering vehicle, wherein the connecting mechanism is assembled in a housing so as to be rotatable and axially movable via an axial feed mechanism. A conical crankshaft that is connected to a rotary shaft and has a pin portion that is inclined at a set angle in the middle with respect to the axis and that is moved in the axial direction by the shaft feed mechanism, and is freely rotatable on the pin portion of the conical crankshaft. And a rod portion extending in the radial direction of the pin portion, which is connected to the operating rod through a conversion mechanism at the rod portion and swings by the rotation of the conical crankshaft to swing the operating rod. It is configured to include a connecting body that is displaced in the axial direction.

[Operation of the invention]

In the rear wheel steering apparatus according to the present invention, when the rotary shaft rotates in response to the steering when the front wheel is steered, the conical crankshaft is rotated by the rotary shaft and is moved in the axial direction by the shaft feed mechanism. Therefore, the connected body assembled on the pin portion of the conical crankshaft swings in accordance with the rotation of the conical crankshaft and moves in the axial direction in accordance with the axial movement of the conical crankshaft, and the connected body swings. The two movements, the movement and the axial movement, are combined and transmitted to the actuation rod via the conversion mechanism. Therefore, the actuating rod is displaced in its axial direction in response to the above-described combined movement,
The rear wheels are steered to the in-phase side when the front wheels have a small steering angle, and the rear wheels are steered to the reverse phase side when the front wheels have a large steering angle.

Thus, in the rear wheel steering device according to the present invention, by appropriately setting the feed amount per one rotation of the conical crankshaft by the shaft feeding mechanism, by appropriately setting the inclination angle of the pin portion of the conical crankshaft, The axial displacement of the operating rod obtained by the rotation of the conical crankshaft can be appropriately set, and the rear wheel steering angle with respect to the front wheel steering angle that matches the characteristics of the vehicle that differs depending on the vehicle type can be set.

〔The invention's effect〕

By the way, in the rear wheel steering device according to the present invention, the feed amount by the above-mentioned axial feed mechanism and the inclination angle of the pin portion of the conical crankshaft are not restricted by any manufacturing process even if the space is limited. Since each of them can be set steplessly as appropriate, it is possible to extremely easily set the optimum rear wheel steering angle that matches the characteristics of the vehicle that differs depending on the vehicle type, within a limited space.

Further, in the rear wheel steering system according to the present invention, in setting the neutral position where the steering angles of both rear wheels are zero, only the position in the rotational direction of the conical crankshaft with respect to the housing is set to the set position and then the connected body is converted. It suffices to connect it to the actuating rod through a mechanism, and the assembling property is extremely good, and it can be manufactured at low cost.

〔Example〕

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

1 to 8 show a first embodiment of a rear wheel steering system according to the present invention, and FIG. 5 schematically shows a front and rear wheel steering vehicle equipped with the rear wheel steering system according to the present invention. . In the vehicle shown in FIG. 5, the rack bar 11 that constitutes the front wheel side steering link mechanism 10 is displaced in the left and right direction by operating the steering wheel WS, and the knuckle arms 12 and 13 that give a steering angle to each front wheel WF. Are connected via tie rods 14 and 15. Rack bar 11 and knuckle arm 1
A ball joint is provided at each of the connecting portions of the 2/13 and the tie rods 14/15. Further, the rear wheel steering device is connected to the rack bar 11 via the rotary shaft 20.

The rotary shaft 20 is a main shaft 21, a pair of front and rear intermediate shafts 2.
The main shaft 21 is connected to the rack bar 11 via an intermediate shaft 22 and a pinion shaft 24. The main shaft 21 is divided into four shafts 2, 23 and a pinion shaft 24. The main shaft 21 is rotatably supported by the vehicle body, and extends from the front portion of the vehicle body to the rear by a predetermined length. The number of divisions of the rotary shaft 20 can be changed appropriately.

As shown in FIGS. 1 to 5, the rear wheel steering system includes a connecting mechanism A that connects the rotary shaft 20 and the operating rod 30, and both rear wheels.
A link mechanism B that connects WR, and a power steering mechanism C that connects the link mechanism A and the link mechanism B and assists the force transmitted from the link mechanism A to the link mechanism B are provided.

The coupling mechanism A includes an input shaft 41, a conical crankshaft 42, a ball screw mechanism D, a coupling body 43, and a rotor 44 that are assembled in a housing H that is assembled in the vehicle body. The input shaft 41 is
It is mounted on the housing H by a pair of bearings 51, 52 so as to be rotatable but immovable in the axial direction, and has a rotating shaft at its tip.
It is connected to the intermediate shaft 23 of 20 so that it can rotate integrally,
The tip of the conical crankshaft 42 is connected to the rear cylindrical portion 41a via a ball spline 45 so as to be integrally rotatable and slidable in the axial direction. In addition, ball spline 45
Is a known one, whereby the sliding resistance in the axial direction between the input shaft 41 and the conical crankshaft 42 is reduced.

The conical crankshaft 42 has an inclined pin portion 42a that is inclined at a set angle θ with respect to the axis L1 at the middle portion, and has a rear end 42b.
Is assembled to the housing H via the ball screw mechanism D and is rotatable with respect to the housing H and movable in the axial direction. The ball screw mechanism D is an axial feed mechanism that moves the coaxial shaft 42 in the axial direction by a predetermined feed amount when the conical crank shaft 42 rotates.
A screw groove 42c is formed on the outer periphery of the rear end shaft portion 42, and a ball nut 47 is fixed to the housing H and accommodates a large number of balls 46 which are circulated and supplied to the screw groove 42c. In this embodiment, as is apparent from FIG. 5, the intermediate shaft 20 rotates in the same direction as the steering wheel WS, so the ball screw mechanism D has a left-hand thread. 20 is the steering wheel
When the structure is such that it rotates in the direction opposite to WS, the ball screw mechanism D must be a right-hand screw.

The connecting body 43 is rotatably assembled on the pin portion 42a of the conical crankshaft 42 via a pair of bearings 53, 54,
It has a rod portion 43a extending in the radial direction of the pin portion 42a,
The rod portion 43a is connected to the rotor 44 via a ball bearing 48. The ball bearing 48 is slidable with respect to the rod portion 43a, and is tiltably assembled in a spherical mounting hole 44a provided in the rotor 44. The rotor 44 is a member 44A, 4 that is vertically separable and is connected by four bolts 44C.
4B, housing H has a pair of bearings
Sector teeth 4 that are rotatably assembled via 55 and 56 and that mesh with rack teeth 30a formed on one side of the operating rod 30.
Has 4b. The play in both bearings 55 and 56 is
It can be removed by screwing the holder Ha (fixed by the lock nut Hb) screwed to the housing H.

Therefore, in the above-mentioned connecting mechanism A, the conical crankshaft 42 formed by assembling the input shaft 41 via the ball spline 45 is connected to the conical body 43 via the bearings 53 and 54.
And ball nut 47.

A ball bearing 48 is assembled in a spherical mounting hole 44a provided in the upper member 44A of the rotor 44.

The one assembled above and the one assembled above are
The rod portion 43a of the connecting body 43 is fitted into the ball bearing 48 while being fitted together.

The lower member 44B is coupled to the upper member 44A of the rotor 44 by a bolt 44C so that the shaft portions supported by the bearings 55 and 56 are coaxial.

The one assembled in the above steps is incorporated into the housing H in which the bearing 52, the working rod 30 and the like are previously assembled.

After mounting the bearing 56 and stopping with the snap ring,
Bearing 55 is assembled and temporarily tightened by holder Ha.

Bearing 51 is installed and stopped by a snap ring.

Assemble the rear cover Hc on the ball nut 47 in the neutral position, connect the rear cover Hc and the ball nut 47 with the bolt Hd, and use the bolt H to attach the rear cover Hc to the housing H.
Bind to.

Finally, the holder Ha is fixed by the lock nut Hb, and the cap Hf is attached to the housing H. In the above process, the conical crankshaft 42, the connecting body 43, the rotor 44, the ball nut 47 and other members are assembled in the housing H.

The link mechanism B, as shown in FIGS. 3 and 5,
The operating rod 30, the relay rod 71 penetrating the operating rod 30, the tie rods 72, 73 connected to the left and right ends of the relay rod 71 via ball joints, and the tie rods 72, 73 via ball joints. The knuckle arms 74 and 75 are connected to each other, and both rear wheels WR are steered by the lateral displacement of the knuckle arms 74 and 75. It should be noted that the boots 76 and 77 having both ends fixed to the ends of the housing H and the ends of the tie rods 72 and 73, respectively.
The inside of is connected by a pipe 78 so that the lateral movement of the relay rod 71 is not hindered.

The relay rod 71 includes a first rod 71A which penetrates the operating rod 30 and has both ends projecting from the operating rod 30 and a first rod 71A.
The rod 71A is composed of a second rod 71B and a third rod 71C, which are screwed to the left and right ends of the rod 71A, and lock nuts 71D, 71E for fixing the screwing amount of the rods 71B, 71C, and the length can be adjusted. The bearing bushes 61 and 62 mounted on the housing H are slidably supported in the axial direction. A socket 71b1 forming a ball joint with the spherical end portion 73a of the tie rod 73 is integrally formed at the outer end of the second rod 71B. Further, a spring 31 and a pair of left and right flanged sleeves 32, 33 are interposed between the relay rod 71 and the operating rod 30, so that the relative axial movement of both rods 30, 71 is elastically repulsed by a predetermined amount. It is being transmitted.

The power steering mechanism C assists the force transmitted from the operating rod 30 to the relay rod 71, and is composed of a control valve C1, a power cylinder C2, and the like. The control valve C1 is
The spool type control valve is a valve sleeve 34 fitted and fixed in the operating rod 30, and a first one in the relay rod 71.
The valve spool 71a1 formed on a part of the rod 71A is provided, and the supply port 71 formed on the valve spool 71a1.
a2 communicates with an inflow port 71b3 provided in the second rod 71B through a through hole (not shown) provided in the first rod 71A and a through hole 71b2 provided in the second rod 71B, and both formed in the valve spool 71a1. The discharge port 71a3 is a through hole (not shown) provided in the first rod 71A in parallel with the through hole, a through hole 71a4 extending radially outward from the end of the through hole, and a second rod 71B.
Through a through hole 71b4 provided in the second rod 71B. The inflow port 71b3 is connected to the hydraulic pump P, and the outflow port 71b5 is connected to the reservoir T.

On the other hand, the power cylinder C2 forms a left and right pair of oil chambers R1 and R2 by being slidably fitted in the cylinder body Hg formed by using a part of the housing H in the cylinder body Hg. The piston 71c1 is provided, and the piston 71c1 is fixed on the third rod 71C of the relay rod 71. Third
The oil chamber R1 on the left side of the drawing has a through hole 71c2 and an inner hole 71c3 provided on the third rod 71C and a through hole 71a5 provided on the first rod 71A, and a left port 71a6 of the valve spool 71a1 formed on the valve spool 71a1.
The oil chamber R2 on the right side of FIG. 3 is connected to the third rod 71C.
Through a through hole 71c4 provided in the first rod 71A and a through hole 71a7 provided in parallel with the hole 71a5 in the first rod 71A to communicate with a right port 71a8 in FIG. 3 formed in the valve spool 71a1.

In the present embodiment configured as described above, when the steering wheel WS is rotated, the rack bar 11 is displaced in the left-right direction and the front wheels WF are steered. During this steering, the rotary shaft 20 is rotated by the rack bar 11, the input shaft 41 of the coupling mechanism A is rotated and the conical crankshaft 42 is rotated, and at the same time, the ball screw mechanism D moves the shaft in the axial direction. Therefore, the pin portion 42 of the conical crankshaft 42 is
As illustrated in FIG. 6 (when the conical crankshaft 42 rotates 90 degrees right) and FIG. 7 (when the conical crankshaft 42 rotates 180 degrees right), the connecting body 43 mounted on the a is It swings in accordance with the rotation of the conical crankshaft 42, and moves in the axial direction in accordance with the axial movement of the conical crankshaft 42,
Two movements of the connecting body 43, that is, the swing and the axial movement, are combined and transmitted to the operating rod 30 via the ball bearing 48 and the rotor 44. Therefore, the actuating rod 30 moves in the axial direction in accordance with the above-described combined movement by the amount shown by the solid line in FIG. 8 (this amount is the movement obtained by the swing of the connecting body 43 shown by the chain line). Amount and the amount of movement obtained by the axial movement of the connecting body 43 indicated by the chain double-dashed line) are displaced), and when the front wheel WF is at a small steering angle, it is small toward the in-phase side, and the front wheel WF When the steering angle is large, the rear wheel WR is steered to the opposite phase side. In addition, the movement of the operating rod 30
The power is transmitted to the relay rod 71 via 31 and the like, and the power cylinder mechanism C is actuated. Therefore, the rear wheel WR is steered while being assisted by the power cylinder mechanism C.

Therefore, in this embodiment, the feed amount per revolution of the conical crankshaft by the ball screw mechanism D (screw groove 42c
(Determined by the lead of the conical crankshaft 42), and the inclination angle θ of the pin portion 42a of the conical crankshaft 42 is set appropriately.
The axial displacement of the actuating rod 30 obtained by the rotation of the vehicle can be appropriately set, and the rear-wheel steering angle with respect to the front-wheel steering angle that matches the characteristics of the vehicle that differs depending on the vehicle type can be set.

By the way, in the present embodiment, the feed amount by the ball screw mechanism D and the inclination angle θ of the pin portion 42a of the conical crankshaft 42 are not limited by manufacturing even if the space is limited. Since each of them can be set steplessly as appropriate, it is possible to extremely easily set the optimum rear wheel steering angle that matches the characteristics of the vehicle that differs depending on the vehicle type, within a limited space.

Further, in the present embodiment, in the setting of the neutral position where the turning angles of both rear wheels are zero, the rotational direction of the conical crankshaft 42, which is preassembled with the connecting body 43, the ball bearing 48, the rotor 44, etc., with respect to the housing H. It suffices to engage (connect) the sector teeth 44b of the rotor 44 with the rack teeth 30a of the actuating rod 30 after setting only the position to the set position.

In this embodiment, since the power steering mechanism C is arranged on the rear wheel WR side of the coupling mechanism A, when the relay rod 71 is pushed in the axial direction by the external force from the rear wheel WR, the control valve C1 is operated. The power cylinder C2 is operated so as to generate a force that opposes the external force. Therefore, the external force is canceled and the rear wheel steering device is not operated by the external force.

9 and 10 show a second embodiment of the rear wheel steering system according to the present invention.
In this embodiment, the conical crankshaft 42A is assembled to the housing H via the ball screw mechanism D at the front shaft portion and the bearing bush 59 at the rear shaft portion. It is attached to the housing H so as to be rotatable and slidable in the axial direction, and is rotatable with respect to the housing H and movable in the axial direction. Further, in this embodiment, the conical crankshaft 42A is
0 rear intermediate shaft (the intermediate shaft 2 of the first embodiment described above)
(Corresponding to 3) is directly connected to the intermediate shaft, and the intermediate shaft is composed of two shafts having a spline fitting portion that allows axial movement in the intermediate portion. Since the other structure is substantially the same as that of the first embodiment, the same reference numerals are given and the description thereof is omitted. Since the operation of the second embodiment is substantially the same as the operation of the first embodiment, the description thereof will be omitted.

[Modification]

In the above embodiment, the ball screw mechanism D is adopted as the axial feed mechanism for moving the coaxial shaft in the axial direction when the conical crankshaft rotates, but this axial feed mechanism may be another one, for example, the eleventh. A shaft feed mechanism using a cam (having a cam groove) 81 and a cam follower (a pin integrally provided on the conical crankshaft 42) 82 as shown in the figure may be used.

Further, in the above-described embodiment, the rotary shaft 20 that rotates in response to the steering operation of the front wheels WF is connected to the rack bar 11 of the front wheel side steering link mechanism and is rotated by the axial movement of the rack bar 11. However, it is also possible to connect the rotating shaft 20 to the steering main shaft that is directly rotated by the steering wheel WS so that the rotating shaft 20 is rotated by the steering main shaft.

Further, in the above embodiment, the actuating rod 30 and the relay rod 71 are used as separate members so as to be relatively movable in the axial direction, and the power steering mechanism C is arranged coaxially with both rods 30 and 71. It is also possible to integrate the rods 30 and 71 and omit the power steering mechanism C for implementation.

[Brief description of drawings]

1 to 8 relate to a first embodiment of a rear wheel steering system according to the present invention. FIG. 1 is an enlarged vertical sectional view taken along the line I-I in FIG. 3, and FIG. 1 is a partially cutaway plan view of the portion shown in FIG. 1, FIG. 3 is a vertical sectional front view of the rear wheel steering device, and FIG.
FIG. 5 is a plan view of the same, FIG. 5 is a plan view schematically showing an example of a vehicle equipped with the rear wheel steering device, and FIGS. 6 and 7 are operation explanatory views of main parts of the rear wheel steering device. FIG. 8 is a diagram showing the relationship between the rotation angle of the conical crankshaft and the axial displacement of the operating rod obtained by the rear wheel steering system. 9 and 10 relate to the second embodiment of the rear wheel steering system according to the present invention. FIG. 9 is an enlarged vertical side view of the main part, and FIG. 10 is a partially cutaway plan view of the same. . FIG. 11 is a partial cross-sectional view showing a modified example of the shaft feed mechanism of the rear wheel steering system according to the present invention. Explanation of code 10 …… Front wheel side steering link mechanism, 20 …… Rotating shaft,
30 …… Operating rod, 30a …… Rack teeth, 42 …… Conical crankshaft, 42a …… Pin section, 42c …… Screw groove, 43 …… Coupling body, 43a …… Rod section, 44 …… Rotor, 44b… … Sector teeth, 46 …… Ball, 47 …… Ball nut, 48 …… Ball bearing, A …… Coupling mechanism, B …… Rear wheel side steering link mechanism, D …… Ball screw mechanism (shaft feed mechanism), H ......
Housing, L1 …… Conical crankshaft axis, WS ……
Steering wheel, WF ... front wheel, WR ... rear wheel.

Claims (3)

[Claims] 1. A rotary shaft that rotates in response to a steering operation of front wheels is connected to an operating rod of a rear wheel side steering link mechanism,
The actuating rod is displaced in the axial direction in accordance with the rotation of the rotary shaft, and the rear wheels are placed in the in-phase side when the front wheel is at a small steering angle.
Further, in a rear wheel steering system for a front and rear wheel steering vehicle comprising a connecting mechanism adapted to steer the rear wheels to the opposite phase side when the front wheel has a large steering angle, the connecting mechanism is connected to the housing via an axial feed mechanism. A conical crankshaft that is assembled rotatably and axially movable and that is connected to the rotary shaft and that has a pin portion in the middle that is inclined at a set angle with respect to the axis and that is axially moved by the axial feed mechanism. And a rod portion that is rotatably mounted on the pin portion of the conical crankshaft and extends in the radial direction of the pin portion, and is connected to the operating rod at the rod portion via a conversion mechanism. A rear wheel steering system for a front and rear wheel steering vehicle, comprising a connecting body that swings by a rotation of a crankshaft to displace the operating rod in an axial direction thereof. 2. A ball comprising a screw groove formed on an outer periphery of a shaft portion of the conical crankshaft, and a ball nut for accommodating a ball fixed to the housing and internally circulated and supplied to the screw groove. The rear wheel steering device according to claim 1, wherein the rear wheel steering device is a screw mechanism. 3. The conversion mechanism is rotatably assembled to the housing with sector teeth that mesh with rack teeth formed on one side of the operating rod, and the operating rod is displaced in the axial direction by rotation. And a ball bearing that is tiltably assembled to the rotor while fitted on the rod portion of the connecting body and that rotates the rotor by swinging the rod portion. The rear wheel steering device according to claim 1, wherein the front and rear wheel steering vehicle is a rear wheel steering device.