JPH05272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle in which both front wheels and rear wheels are steered.

(Prior Art) Recently, four-wheel steering systems for vehicles in which both front wheels and rear wheels are steered have been designed to change the steering ratio of the rear wheels relative to the steering angle, that is, to change the steering ratio of the rear wheels to the steering angle. There is a growing demand for changing the steering angle of the rear wheels in several stages for a certain steering angle, and for this purpose, a steering wheel is required between the steering mechanism and the rear wheel steering mechanism. A steering ratio changing device is required to change the steering ratio of the rear wheels with respect to the angle. Conventionally, this steering ratio changing device utilizes a swing lever, as shown in Japanese Patent Laid-Open No. 55-91457. In this device, one end of the swing lever is linked to the steering mechanism, while the other end is linked to the rear wheel steering mechanism, and the swing fulcrum of the swing lever is changed to achieve the above-mentioned steering ratio. This is what I decided to change.

However, in the above-mentioned conventional device, since the swinging fulcrum of the swinging lever must also serve as a sliding part, this sliding/swinging fulcrum is likely to cause wobbling. On the other hand, since a lever ratio reaction force is applied to this sliding/swinging fulcrum, there is a problem in that it is difficult to ensure sufficient steering rigidity. In addition, since a swinging lever is used, input according to the steering angle of the steering wheel inevitably acts as a large bending force on the long swinging lever. This was also considered undesirable in terms of increasing steering rigidity.

In addition, in the above conventional device, when the angle between the axial direction of the swing lever and the direction of input from the steering mechanism becomes small (approaching parallel), this sliding
There is a problem in that the swing lever tends to be displaced relative to the swing fulcrum, which is undesirable for ensuring an accurate steering ratio.

(Object of the Invention) The present invention has been made in consideration of the above-mentioned circumstances, and provides a vehicle four-wheel vehicle that can accurately obtain a desired steering ratio and has sufficiently high steering rigidity. The purpose is to provide a steering device.

(Structure of the Invention) In the present invention, a rotating member that is rotated according to the operational displacement of the steering mechanism, that is, the steering angle of the steering wheel, is used as a substantial input member of the steering ratio changing device. The rotating member is provided with an inclination angle changing means for changing the inclination angle that the rotating orbital surface makes with respect to a predetermined reference plane.
Thereby, the rotational eccentric position of the rotational member is displaced in accordance with the rotational angle and the inclination angle of the rotational member with respect to the axial direction perpendicular to the reference plane.
By linking such a rotational eccentric position to the rear wheel steering mechanism, the steering angle of the rear wheels is controlled in accordance with the rotation angle and inclination angle.

(Example) In Fig. 1, 1R is a right front wheel, 1L is a left front wheel, 2R is a right rear wheel, and 2L is a left rear wheel.The left and right front wheels 1R and 1L are linked by a front wheel steering mechanism A, and Left and right rear wheels 2R and 2L are rear wheel steering mechanism B
It is linked by.

In the embodiment, the front wheel steering mechanism A includes a pair of left and right knuckle arms 3R, 3L and tie rods 4R, 4L, and a pair of left and right tie rods 4R, 4L, respectively.
It is composed of a relay rod 5 that connects the 4Ls. A steering mechanism C is linked to the front wheel steering mechanism A, and the steering mechanism C is of a rack-and-pinion type in this embodiment. In other words, relay rod 5 has rack 6.
A pinion 7 meshing with the rack 6 is connected to the handle 10 via a shaft 8. As a result, when the handle 9 is turned to the right, the relay rod 5 is displaced to the left in FIG. The steering wheel is steered clockwise in the figure by an amount corresponding to the amount of operation displacement 9, that is, the steering angle of the steering wheel. Similarly, when the steering wheel 9 is operated to the left, the left and right front wheels 1R, 1L are steered to the left in accordance with the amount of displacement of this operation.

Similarly to the front wheel steering mechanism A, the rear wheel steering mechanism B also has a
A pair of left and right knuckle arms 10R, 10 respectively
In this embodiment, the rear wheel steering mechanism B is equipped with a hydraulic power steering mechanism D. . To explain this power steering mechanism D, a cylinder device 13 is attached to the relay rod 12, and a piston 13d defines the inside of the cylinder 13a into two chambers 13b and 13c.
is integrated into the relay rod 12. Two chambers 13b and 13c within this cylinder 13a are connected to a control valve 1 via piping 14 or 15.
6. Further, pipes 18 and 19 extending from the reservoir tank 17 are connected to the control valve 16, respectively, and an oil pump 20 driven by an engine (not shown) is connected to one pipe 18, which serves as an oil supply pipe. There is. The control valve 16 includes an input shaft 16 that serves as an input member of the power steering mechanism D.
a, and an output shaft 16b serving as an output member connected to the input shaft 16a. A pinion 21 attached to the output shaft 16b is meshed with a rack 22 formed on the relay rod 12.

In such a power steering mechanism D, as is known, when the input shaft 16a is rotated in one predetermined direction, the pinion 21 is rotated accordingly.
are rotated in the same direction, displacing the relay rod 12, for example, to the left in FIG.
Rotate clockwise in Figure 1 around 10L',
The rear wheels 2R and 2L are steered to the right. During this steering, oil is supplied into the chamber 13b of the cylinder device 13 according to the amount of rotation of the input shaft 16a to assist in driving the relay rod 12 (boosting effect). Similarly, when the input shaft 16a is rotated in the opposite direction, depending on the amount of rotation, the rear wheels 2R, 2L are will be steered to the left.

Note that reference numerals 13e and 13f in FIG. 1 are return springs that urge the relay rod 12 to the neutral position.

The steering mechanism C and the rear wheel steering mechanism B are linked via the front wheel steering mechanism A and the steering ratio changing device E. An intermediate rod 23 extends forward from the steering ratio changing device E, and a pinion 24 attached to the front end of the intermediate rod 23 is engaged with a rack 25 formed on the relay rod 5 of the front wheel steering mechanism A. Also, the input shaft 16a of the control valve 16 is connected to the rack 27 formed on the rod-shaped moving member 26 extending from the steering ratio changing device E.
A pinion 28 attached to the pinion 28 is engaged with the pinion 28.

An example of the steering ratio changing device E will be explained with reference to FIGS. 2 and 3. The moving member 26 is held slidably in the vehicle width direction with respect to the vehicle body F, and its axis of movement is l ₁ It is shown as. Further, this steering ratio changing device E has a rotating member 29, and in the embodiment, this rotating member 29 is connected to an intermediate member 32 rotatably connected to a holder 30 by a pin 31. and a second member 33 slidably fitted to the tip of the first member 32. The holder 30 is held by the vehicle body F so that its rotation shaft 30a can rotate about an orthogonal line _l2 orthogonal to the movement axis _l1 of the moving member 26. The pin 31 passes through the intersection of both lines _l1 and _l2 and extends in a direction perpendicular to the orthogonal line _l2 .

A connecting portion between the holder 30 and the first member 32 is shown in FIG. 3, and a pin 31 is installed between the U-shaped upper forked portion of the holder 30.
The first member 3
The base end portions of the two are rotatably fitted. This 3
In the figure, 35 is the first
A hub 36 is a lock nut for preventing the member 32 from coming off, and a hub 37 is a lock nut for preventing the pin 31 from coming off the holder 30 in cooperation with a retaining ring 38. Therefore, the rotating member 29 is rotatable about the pin 31, and by rotating the holder 30, the movement axis l of the rotating orbital surface about the pin 31 can be adjusted. The inclination angle with respect to a plane perpendicular to ₁ (in the embodiment, this plane is referred to as a "reference plane") is variable.

The tip of the second member 33 of the rotating member 29 and the moving member 26 are connected by a connecting member 40. This connecting member 40 is connected to the axis of movement in the embodiment.
It has a first arm 41 that is parallel to l ₁ and a second arm 42 that is inclined with respect to the movement axis l ₁ . The two arms 42 and the moving member 26 are connected by ball joints 44 to 46, respectively. The second arm 42 is
It is constructed by screwing together the components 42a and 42b of the second arm 42 of the book, and using a lock nut 47, the connection length, that is, the distance between the ball joints 44 and 46, is adjusted to a predetermined length. It has been adjusted and maintained. In addition, the second
The component 42b of the arm 42 is bent to avoid interference with the movable member 26, but a ball joint 46 (connection between the movable member 26 and the second arm 42) is formed on the axial extension line of the linear component 42a. part) is located.

The rotating member 2 is connected by the connecting member 40 as described above.
Ball joint 44 which is the rotational eccentric position of 9
The distance between the ball joint 46 and the ball joint 46 is always kept constant. Therefore, if the ball joint 44 is displaced in the left-right direction in FIG. 2, the moving member 26 will be displaced in the left-right direction in FIG. 2 in accordance with this displacement.

The rotation of the rotating member 29 about the pin 31 is as follows:
This is done in accordance with the operational displacement of the steering mechanism C, that is, the steering angle of the steering wheel. For this reason, in the embodiment, a rotation imparting arm 48 is provided for the first arm 41. This rotation imparting arm 48 has a rotation shaft 48a formed at its base end.
is rotatably held relative to the vehicle body F so as to be on the movement axis _l1 , and a cylindrical portion 48 provided at the tip thereof
The first arm 41 is slidably passed through the inside of b. The rotation shaft 48a of the rotation imparting arm 48
A bevel gear 50 attached to the rear end of the intermediate rod 23 meshes with a bevel gear 49 attached to the intermediate rod 23. With such a rotation imparting arm 48, the rotation member 29 is rotated about the pin 31 by an amount corresponding to the steering angle, but the axis of the pin 31 and the axis of movement _l1 are When tilted, the ball joint 44 is displaced in the left _- right direction in FIG. The moving member 26 will be displaced.
The displacement of this ball joint 44 in the left-right direction in FIG.
Even if the rotation angles of the pins 31 and 9 are the same, the angle of inclination between the pin 31 and the aforementioned reference surface, that is, the angle of inclination of the holder 3
If the rotation angle of 0 changes, it will be changed.

In order to change the inclination angle, a sector gear 51 is attached to the rotating shaft 30a of the holder 30, and a pinion 5 meshing with the sector gear 51 is attached.
2 is an actuator 5 such as a solenoid or motor
3, it is designed to be rotationally driven. The rotation angle, that is, the inclination angle of this holder 30 is
It is designed to be detected by a steering ratio detection sensor 54.

Here, the above-described rotation angle of the rotation member 29 about the pin 31 and the inclination angle of the rotation member 29 (the inclination angle of the pin 31) are the movement axis l ₁ of the ball joint 44 (moving member 26). The influence on the displacement in the direction will be explained with reference to FIGS. 5 and 6.
9. The connecting member 40, etc. are shown in mock form).
In FIGS. 5 and 6, the rotating member 2
9, the rotation angle around pin 31 is θ, and the movement axis
If the reference plane perpendicular to l ₁ is δ, the angle of inclination of the rotating orbital surface of the rotating member 29 with the reference plane δ is α, and the eccentric distance of the ball joint 44 from the pin 31 is r, then this ball joint The displacement X in _one direction of the movement axis l of the point 44 is X=r tan α・sinθ,
It is a function with α and θ as parameters. Therefore, if the inclination angle α is fixed to a certain value,
is a function of θ, that is, it depends on the steering angle of the steering wheel, and if the value of this inclination angle α is changed, the value of X will change even if the steering angle of the steering wheel is the same. Then, this change in the inclination angle α directly results in a change in the steering ratio.

As described above, there is a case as shown in FIG. 4 as an example of changing the steering ratio by adjusting the inclination angle. In this Fig. 4, the steering ratio is changed according to the vehicle speed, and in the embodiment, 6 of β ₁ to β ₆ are used.
The steering ratio characteristic curves of various types are obtained. Note that in FIG. 5, β ₁ and β ₂ are in the case of so-called reverse phase steering in which the rear wheels 2R and 2L are steered in the opposite direction to the front wheels 1R and 1L, and β ₄ to
β ₆ is the case of in-phase steering in which the rear wheels 2R, 2L are steered in the same direction as the front wheels 1R, 1L. Of course, in the case of the opposite phase and the same phase, the inclination angle α shown in FIGS. 5 and 6 is + in the case of the same phase, and becomes − in the case of the opposite phase. Note that β ₃ is a case where the rear wheels 2R and 2L are not steered regardless of the steering operation.

FIG. 7 shows an example of control in which the steering ratio is changed according to the vehicle speed as described above. That is, the control circuit 55 includes a discrimination circuit 56, a comparison circuit 57, and a drive circuit 5.
8, and the vehicle speed signal from the vehicle speed sensor 59 is input to the discrimination circuit 56. The comparison circuit 57 receives the determination signal from the determination circuit 56 as well as the steering ratio signal from the steering ratio detection sensor 54 that detects the actual inclination angle α. Based on the comparison result with the steering ratio signal, the drive circuit 58 outputs the signal to the actuator 53. In this way, the inclination angle α of the rotating member 29, that is, the steering ratio, is set according to the vehicle speed while performing feedback control (as shown in the steering ratio characteristic curves β ₁ to β ₆ in FIG. 4). selection).

Note that 60 in FIG. 1 is a battery.

FIGS. 8 and 9 show other embodiments of the steering ratio changing device E, and the same components as those in the previous embodiment are given the same reference numerals and their explanations will be omitted (this will be explained below). The same applies to other embodiments).

In this embodiment, unlike the above embodiment, the second arm 42 of the connecting member 40 is composed of one rod, and a length adjusting member 26a screwed to the moving member 26 is provided. , Locknut 6
1 is used to adjust and maintain the connection length. Along with this, the second arm 42
and the length adjusting member 26a are coupled by a ball joint 62. Further, the rotation imparting arm 48 has its tip connected to the first end through the ball joint 63.
While connected to the arm 41, a hollow slider 64 is fitted into the forked portion 48c provided at the intermediate portion thereof, as shown in FIG. 9, so as to be slidable in the left and right directions in FIGS. The rotating member 29 is slidably passed through the hollow slider 64. Note that this rotating member 29 is made by integrating the first member 32 and the second member 33 in the embodiment shown in FIG.

In this embodiment, as the rotating member 29 rotates, the hollow slider 64 moves inside the forked portion 48c into the eighth position.
The moving member 2 slides in the left-right direction in the figure, and the first arm 41 swings slightly around the ball joint 63.
6 will be displaced in the left-right direction in FIG. Of course, the steering ratio is changed by changing the rotation angle, that is, the inclination angle, of the holder 30, as in the previous embodiment.

FIGS. 10 and 11 show still another embodiment of the steering ratio changing device E. FIG. In this embodiment, in addition to the first arm 41 and the second arm 42, the connecting member 40 shown in FIG.
Furthermore, it has a third arm 43, and the rotating member 29 and the third arm 43 are connected by a ball joint 44.
Further, the first arm 41 and the third arm 43 are connected to the pin 6.
5. Further, the rotation imparting arm 48 has a cylindrical portion 48b through which the first arm 41 is slidably passed, and a forked portion 48c that clamps the connecting portion of the pin 65 from the axial direction of the pin 65. have Furthermore, a motor 53 (not shown in FIGS. 10 and 11) serving as an inclination angle changing means includes a pinion 52, a swinging crank mechanism 6
6, the rotation angle, that is, the inclination angle of the holder 30 is changed. That is, one end of the arm 68 is connected by a pin 69 to the eccentric position of the gear 67 meshing with the pinion 52, while the other end of the arm 68 is connected to the holder 30.
(This swing crank mechanism is omitted in the 11th example).

In FIG. 12, a steering mechanism C and a steering ratio changing device E, which are separated from each other in the longitudinal direction of the vehicle body, are linked via fluid. That is, compared to the one shown in FIG. 1, the intermediate rod 23 for mechanically interlocking the front wheel steering mechanism A and the steering ratio changing device E is omitted, and the pinion 24 is also omitted. , rack 25 are omitted. And the relay rod 5 of the front wheel steering mechanism A
A front cylinder device 71 is attached to the front cylinder device 71, and a piston 71d that defines the interior of the cylinder 71a into two chambers 71b and 71c is integrated with the relay rod 5. On the other hand, near the steering ratio changing device E,
A rear cylinder device 72 is provided, the cylinder 7
A piston rod 72e is integrated with a piston 72d that defines two chambers 72b and 72c inside the piston 2a. Both cylinder devices 71 and 72 are
One of the chambers 71b and 72b is connected to the piping 73,
In addition, the other chambers 71c and 72c are connected to each other by piping 74.
are connected to each other, and thereby the front wheel steering mechanism A
The piston rod 72 of the rear cylinder device 72 is moved in accordance with the displacement of the relay rod 5 in the left-right direction in FIG.
e is adapted to be displaced in the left-right direction in FIG. The displacement of the piston rod 72e in the left-right direction in FIG. 12 is linked to the rotation imparting arm 48 of the steering ratio changing device E via a rack 75 formed on the piston rod 72e and a pinion 76 meshing with the rack 75. (This rod 77 corresponds to the rear end of the intermediate rod 23 shown in FIG. 1).

In addition, the control valve 16 shown in FIG.
This is a so-called booster valve type in which the input and output shafts are sliding types, and the input member of the control valve 16 is also used by a moving member 26, and the output member of the control valve 16 is also used by this moving member 26. 16b is integrated into the relay rod 12 of the rear wheel steering mechanism B. As a result, the structure of the linking portion between the moving member 26, the control valve 16, and the rear wheel steering mechanism B becomes much simpler than that shown in FIG. 1. The operation of the power steering mechanism D itself equipped with such a control valve 16 is substantially the same as that shown in FIG. 1, so detailed explanation thereof will be omitted.

Furthermore, in the case of FIG. 12, for each chamber 71b, 71c of the front cylinder device 71, piping 79, 8 extending from the reservoir tank 78, respectively, near the piston 71d in the neutral position.
0 is connected to compensate for changes in volume of the piping system between the front cylinder device 71 and the rear cylinder device 72 due to changes in temperature or the like.

In addition, 72f and 72g in FIG. 12 indicate the piston 7.
2d, that is, a return spring that urges the handle 9 to the neutral position.

Here, when a stepping motor is used as the actuator 53, the motor rotation angle can be kept small, so the tilt angle can be precisely controlled, and the steering ratio characteristic curve can be changed continuously, that is, steplessly. Furthermore, there is no longer a need to supply a holding current to maintain a predetermined steering ratio. Power consumption can be reduced. In addition, when a DC motor is used as the actuator 53, the rotational torque is large, so the device can be made smaller, and it is highly reliable against heat, vibration, and voltage drop. Ba,
This also allows for precise control.

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases.

The steering ratio can be changed not only by the vehicle speed, but also by the magnitude of lateral acceleration acting on the vehicle body, or by manual selection by the driver. The steering ratio may be changed by combining a plurality of elements such as.

Rear wheel steering mechanism B is power steering mechanism D
On the other hand, the front wheel steering mechanism A may have a power steering mechanism.

The steering ratio changing device E may be linked directly to the steering mechanism C without going through the front wheel steering mechanism A.

The reference plane that serves as a reference for setting the inclination angle of the rotating member 29 is not limited to a plane perpendicular to the movement axis _l1 , and can be set as appropriate.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
Since the steering ratio is changed by changing the inclination angle of the rotating member that rotates according to the steering angle, sufficient rigidity is ensured in the steering ratio changing part itself, and the steering system The overall rigidity can be improved, and a desired steering ratio can be accurately obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram showing one embodiment of the present invention.
FIG. 2 is a diagram showing a specific configuration example of the steering ratio changing device. FIG. 3 is a sectional view showing a specific example of the structure of the rotating portion of the rotating member. FIG. 4 is a characteristic diagram showing an example of changing the steering ratio according to vehicle speed. Figures 5 and 6
The figure is a simplified explanatory diagram for explaining the principle of changing the steering ratio in the present invention, and FIG. 6 is shown as a side view of FIG. 5. FIG. 7 is a circuit diagram showing an example of control for changing the steering ratio. FIG. 8 is a diagram showing another specific example of the configuration of the steering ratio changing device. FIG. 9 is a sectional view taken along the - line in FIG. 8. FIGS. 10 and 11 show still other specific configuration examples of the steering ratio changing device,
FIG. 10 is a plan view of FIG. 11. FIG. 12 is an overall system diagram showing another embodiment of the present invention. A: Front wheel steering mechanism, B: Rear wheel steering mechanism, C: Steering mechanism, D: Power steering mechanism,
E: steering ratio changing device, l ₁ : moving axis, δ: reference plane, α: tilt angle, θ: rotation angle, 1R, 1L: front wheel, 2R, 2L: rear wheel, 26: moving member, 29:
Rotating member, 30a: rotating shaft (axis center for changing inclination angle),
31: Pin (rotation axis of rotation member), 40: Connection member.

Claims (1)

[Scope of Claims] 1. A steering ratio changing device that is interposed between a rear wheel steering mechanism and a steering mechanism linked to a front wheel steering mechanism and that changes the steering ratio of the rear wheels with respect to the steering wheel steering angle. A four-wheel steering device for a vehicle, wherein the steering ratio changing device is rotated in accordance with the steering angle, and the angle of inclination of the rotational track surface relative to a predetermined reference plane is variable. a rotating member; an inclination angle changing means for changing the inclination angle of the rotating member;
The rotation eccentric position of the rotation member and the rear wheel steering mechanism are linked, and the rotation eccentric position is determined according to the rotation angle and the inclination angle of the rotation member. A four-wheel steering system for a vehicle, characterized in that the steering angle of the rear wheels is controlled. 2. In claim 1, the rear wheel steering mechanism includes a power steering mechanism,
The displacement of the rotational eccentric position is transmitted as an input to the power steering mechanism.