JPH07165090A - Variable spring rate mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to solve the inconvenience that the motion characteristics of the vehicle are uniquely defined by the setting of the spring constant, and to make the characteristics in conflicting relations compatible with each other at a higher level. Improve the spring device to allow. A first shaft and a second shaft which are rotatable relative to each other about the same shaft, and the first shaft and the second shaft are interlockingly connected to at least one of the rotation directions. It is assumed to have a coil spring whose ends are respectively connected to the first shaft and the second shaft, and a drive means for changing the axial length of the coil spring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable spring rate mechanism, and more particularly to a variable spring rate mechanism constructed so that the relationship between the torsion angle and the torsion torque of a coil spring can be changed.

[0002]

2. Description of the Related Art Motor vehicles are provided with various spring devices. For example, a power steering device for assisting the steering force of the steering device is provided with a torsion bar for connecting between the steering wheel and the pinion, and a relative force corresponding to the difference between the steering force and the road reaction force is provided. A rotation angle deviation is generated between the steering wheel and the pinion. Then, by converting this rotational angle deviation into hydraulic pressure applied to the power cylinder using a servo valve, an appropriate auxiliary steering force is applied to the steering rack.

In the above conventional power steering system, when the torsional rigidity of the torsion bar is set high, the relative rotational angle deviation between the steering wheel and the pinion becomes small, and the servo valve for the input from the steering wheel side is reduced. Since the responsiveness of is reduced, it becomes impossible to sufficiently generate the auxiliary steering force in the low speed traveling range. On the contrary, when the torsional rigidity of the torsion bar is set to be low, the response of the servo valve is excessively increased, which causes an inconvenience that the steering response in the high speed traveling range becomes too sensitive.

On the other hand, in a suspension system of an automobile, a structure is known in which a torsion bar is provided between a suspension arm supporting wheels and a vehicle body. In this case, it is preferable to increase the torsional rigidity in order to improve the ground contact property during turning, but if the torsional rigidity is excessively increased, the riding comfort tends to deteriorate.

[0005]

As described above, in the conventional spring device, the relationship between the displacement of the spring used and the reaction force is fixed, so that the low steering force in the case of the power steering device is used. It is extremely difficult to satisfy both characteristics that are in a mutually conflicting relationship, such as the feeling of high rigidity and the relationship between maneuverability and riding comfort in the case of a suspension system, and it is difficult to satisfy certain characteristics. However, there was a point that we had to sacrifice another characteristic to some extent.

The present invention has been devised in order to eliminate such disadvantages of the prior art, and its main purpose is to:
A place where the spring device is improved so as to solve the inconvenience that the motion characteristics of the vehicle are uniquely defined by the setting of the spring constant, and to make the characteristics having mutually contradictory relationships compatible with each other at a higher level. It is in.

[0007]

According to the present invention, such an object is provided for at least one of a first shaft and a second shaft which are rotatable relative to each other about the same shaft, and at least one of rotation directions. A coil spring whose ends are respectively connected to the first shaft and the second shaft so as to interlockly connect the first shaft and the second shaft, and a drive means for changing the axial length of the coil spring. This is accomplished by providing a variable spring rate mechanism having

[0008]

According to this structure, the relationship between the torsion angle and the torsion torque can be changed by changing the axial length of the coil spring in accordance with the running condition. Therefore, for example, stepwise or continuous. The apparent spring rate can be changed. Thus, for example, when applied to a power steering device, a coil spring that can obtain a relative rotation angle that can sufficiently enhance the responsiveness of a servo valve in a low speed traveling range is used, and a desired value in a high speed traveling range is used. A feeling of rigidity can be obtained. When applied to a suspension system, a coil spring with a spring constant that emphasizes riding comfort can be used, and the spring can be shortened regardless of the stroke between the vehicle body and the wheels, so the spring reaction force can be reduced as necessary. It is possible to suppress the change in the vehicle attitude by increasing the height.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to specific embodiments shown in the accompanying drawings.

FIG. 1 is a perspective view of an essential part of a vehicle 2 having a steering device 1 to which the present invention is applied. The left and right front wheels 3 of the vehicle 2 are connected to a steering wheel 7 via a tie rod 4, a rack and pinion type steering gear box 5, and a steering shaft 6.

As shown in FIG. 2, the steering gear box 5 includes a rotary valve unit 11 for controlling a flow path of power steering oil, an input shaft 12 connected to a steering shaft 6, and a pinion 1.
3 and a steering rack 14 meshed with the pinion 13
It consists of The steering rack 14 is integrally provided with a power cylinder 15 that generates an assist axial force.

The rotary valve unit 11 has a return port 17 for returning oil to an oil tank 16, a feed port 20 to which oil pressure is directly supplied from an oil pump 19, and two oils separated by a piston 21 of a power cylinder 15. Two cylinder ports 23a and 23b for supplying hydraulic pressure to the chambers 22a and 22b are provided. The rotary valve unit 11 is integrally connected to a variable spring rate mechanism, which will be described later, and is provided with a control port 18 to which a vehicle speed responsive control hydraulic pressure is supplied from an oil pump 19. The rotary valve unit 11 and the variable spring rate mechanism are integrally connected to the steering gear box 5.

The oil passage 24 for supplying the oil pumped from the oil tank 16 by the oil pump 19 is divided into two, one is connected to the control port 18 via the cutoff valve 25 and the other is the main orifice 26.
Is connected to the feed port 20 via. Further, the oil pump 19 includes a flow control valve 27 and a relief valve 2
8 are connected in parallel so that the discharge flow rate of the oil pump 19 and the pressure of the oil passage 24 are always kept in a constant range.

The control port 18 and the cutoff valve 25 have a vehicle speed composed of a trochoid type hydraulic motor 29, a relief valve 30, and a check valve 31 which are driven by a speedometer drive gear meshed with a differential gear to respond to the vehicle speed. The sensor unit 32 is connected. According to this, when the engine is started and stopped, the hydraulic motor 29 does not rotate, so that the flow of oil from the cutoff valve 25 is blocked, and when the vehicle runs, the hydraulic motor 29 rotates and the oil tank 16 The oil flow rate to the vehicle increases as the vehicle speed increases. Here, the check valve 31 prevents an excessive amount of oil passing through at high speed and prevents the inlet of the vehicle speed sensor unit 32 from being negative pressure, and the relief valve 30 prevents the hydraulic motor 2 from moving when the vehicle moves backward.
Since 9 serves as a pump, it serves to release the hydraulic pressure generated at this time.

As shown in FIG. 3, the rotary valve unit 11 includes a variable spring rate mechanism 41 according to the present invention.
And an input shaft 12 coupled to the steering shaft 6 inside the housing 11a,
A valve element 34 fitted to the outer periphery of the input shaft 12 so as to be rotatable relative to each other is coaxially incorporated.

Housing 11a, input shaft 12, valve body 34
Between the input shaft 12 and the valve body 34, an oil passage whose degree of communication changes in accordance with the amount of relative rotational displacement between the input shaft 12 and the valve body 34 is formed, and the torsion torque applied to the pinion 13, that is, the magnitude of the road surface reaction force. The amount of oil from the two cylinder ports 23a and 23b changes according to the height. Since the basic structure of the oil passage of the rotary valve unit 11 is the same as that of a known rotary valve unit, its detailed description will be omitted.

The variable spring rate mechanism 41 includes a rotary valve unit 11 between the input shaft 12 and the pinion 13.
It is provided in series with. This variable spring rate mechanism 41
Is a housing 11a of the rotary valve unit 11.
An output member 42 that is built in a housing 41a that is integrally connected with the output member 42 and that has a pinion 13 integrally formed on the lower end side, and is bolted to the upper end on the outer peripheral side of the output member 42, and the valve is attached to the upper end. A cap member 43 that connects the body 34, an input member 44 that is rotatably combined with the cap member 43, and has an input shaft 12 integrally formed on the upper end side thereof, and is rotatable inside the input member 44. The upper retainer 45 provided, the lower retainer 46 that is rotatable and axially displaceable in the output member 42, and the upper retainer 45 and the lower retainer 46 are non-rotatable with pins 47 at their respective ends. And a coil spring 48 connected to the. These members are arranged such that their axes are on a common axis by a support shaft 49 inserted through the center of the hollow input shaft 12.

As shown in FIG. 4, each of these members is provided with axial leg portions at positions where the circumference of the member is divided into four equal parts. In this leg portion, the output member 42 and the lower retainer 46 project upward, and the cap member 43, the input member 44, and the upper retainer 45 project downward, respectively.

The leg portions 50 and 51 of the output member 42 and the cap member 43 are aligned with each other, and the leg portions 5 of both of them are aligned.
The bolts B (FIG. 3) are screwed into bolt holes 50a and 51a formed in the leg portions 50 and 51, respectively, by joining together 0.5 and 51, so that they are integrated with each other. The leg portion 50 on the side of the cap member 43 has only a connecting function with the output member 42, and the inner peripheral contour thereof does not interfere with all other members.

The input member 44 is rotatable within the inner circular contour of the leg 50 of the cap member 43, and the leg 52 thereof.
Are opposed to the axial end surface of the inner peripheral side portion of the leg portion 51 of the output member 42 with a minute gap. Here, a relative rotation angle defining means (not shown) is provided between the cap member 43 and the input member 44, and is integrally formed with the valve body 34 connected to the cap member 43 and the input member 44. The relative angular displacement with respect to the input shaft 12 is regulated within a predetermined angular range.

The leg portion 53 of the upper retainer 45 faces one circumferential surface of the leg portion 52 of the input member 44. Further, the length thereof is longer than that of the leg portion 52 of the input member 44, so that the leg portion 51 of the output member 42 is projected by a predetermined dimension.

The lower retainer 46 is integrally formed with a piston 56 that slides into a cylinder hole 55 formed integrally with the output member 42. The legs 54 of the lower retainer 46
Faces the other circumferential surface of the leg portion 52 of the input member 44. Further, the length thereof is always opposed to the leg portion 52 of the input member 44 within the stroke range of the piston 56.

Next, the operating principle of the variable spring rate mechanism 41 will be described with reference to FIG.

The piston 56 of the lower retainer 46 is adapted to be pushed up by the hydraulic pressure supplied from the control port 18 provided in the housing 41a.
Normally, the lower end position shown in FIG. 3 is maintained by the elastic force of the coil spring 48 mounted between the upper and lower retainers 45 and 46. In the neutral state of the torsional torque of the coil spring 48 in this state, the output member 42 and the input member 44 are
The circumferential positions of the leg portions 51 and 52 are aligned with each other, and the initial torsion torque of the coil spring 48 causes the leg portion 53 of the upper retainer 45 to move to the leg portion 52 of the input member 44 shown in FIG. The leg portion 54 of the lower retainer 46 abuts on the facing surface of the leg member 51 of the output member 42 when it moves counterclockwise when viewed from above. Touching (see Figure 5a).

When the input member 44 is rotated counterclockwise in this state, the torque applied to the input member 44 is transferred to the upper retainer 45 via the leg portion 52 of the input member 44 and the leg portion 53 of the upper retainer 45. First transmitted, the upper retainer 45
Rotates with the input member 44. And the upper retainer 4
The torque transmitted to the lower retainer 46 is transmitted to the lower retainer 46 via the coil spring 48.
The output member 42 abutting on is rotated. At this time, the coil spring 48 bends in the twisting direction in accordance with the balance between the rotation resistance acting on the output member 42 side and the torsional rigidity of the coil spring 48, so that the relative circumferential displacement between the input member 44 and the output member 42 occurs. Will occur (see FIG. 5b).

When the input member 44 is rotated in the opposite direction, the torque applied to the input member 44 is first transmitted to the lower retainer 46, and the lower retainer 46 rotates together with the input member 44. The torque transmitted to the lower retainer 46 is transmitted to the upper retainer 45 via the coil spring 48, and the output member 42 that abuts the lower end of the leg portion 53 of the upper retainer 45 rotates. This causes relative circumferential displacement between the input member 44 and the output member 42, as in the above.

When hydraulic pressure is supplied to the cylinder hole 55 of the output member 42, the lower retainer 46 is pushed up and the coil spring 48 is compressed (S dimension in FIG. 5c). As a result, the initial torsional reaction force of the coil spring 48 changes from the characteristic shown by the solid line in FIG. 6 to the characteristic shown by the broken line, and the relative circumferential displacement between the input member 44 and the output member 42 for the same input torque and rotation resistance. The amount is reduced (see Figure 5c). Therefore, the apparent spring constant can be changed as indicated by the chain double-dashed line in FIG. 6 by continuously changing the axial position of the lower retainer 46.

Next, the operation procedure of the power steering apparatus to which the variable spring rate mechanism 41 is applied is mainly shown in FIG.
Will be described with reference to.

In the initial state where the engine is stopped, the cutoff valve 25 is opened by the spring force of the built-in coil spring, and the oil passage from the oil pump 19 to the control port 18 is in communication.

When the engine is started, the oil pump 19
The hydraulic pressure acts on the oil passage 24 from the cutoff valve 25 to the cutoff valve 25. When the vehicle is stopped, the hydraulic motor 29 of the vehicle speed sensor unit 32 is stopped, so the oil passage from the sensor orifice 33 to the oil tank 16 is closed. Therefore, hydraulic pressure acts on the right end of the cutoff valve 25 in FIG. 2, the cutoff valve 25 moves leftward, and the oil passage to the control port 18 is closed. In this state, hydraulic pressure is sealed in the right end of the cutoff valve 25, and the closed state of the cutoff valve 25 is maintained.

In this state, since the hydraulic pressure applied to the lower retainer 46 forming the hydraulic piston is insufficient, the lower retainer 46 is at the lower end position shown in FIG. 3, and the axial dimension of the coil spring 48 is the maximum value. Has become.

When the steering wheel 7 is steered in this state, the coil spring 48 is generated by the road surface reaction force from the front wheels 3.
A twisting torque acts on the shaft to cause a circumferential displacement between the input shaft 12 and the valve body 34. Here, since the axial dimension of the coil spring 48 has the maximum value, the torsional rigidity of the coil spring 48 becomes the minimum, and the angular deviation between the input shaft 12 and the valve element 34 with respect to the torsional torque becomes large.

In this way, when the steering wheel 7 is turned to the left, for example, when the road surface reaction force is large, the input shaft 12
And the valve body 34, the oil passage to the left chamber 22a of the power cylinder 15 is widened, and conversely, the right chamber 2 of the power cylinder 15 is expanded.
The oil passage to 2b becomes narrow. Therefore, the oil pump 19
The amount of oil flowing from the right chamber 22b to the left chamber 22a increases, and at the same time, the oil passage communicating from the right chamber 22b to the oil tank 16 widens.
Therefore, the pressure of the left chamber 22a becomes relatively high, and the thrust for turning the steering wheel to the left is applied to the steering rack 14, and the steering force of the steering wheel 7 is reduced.

On the other hand, at the time of steering to the right, the angular deviation between the input shaft 12 and the valve element 34 has the opposite relationship to the above, and the steering rack 14 is applied with a thrust force for steering to the right.

During high-speed traveling in which the road surface reaction force on the steering wheel 7 is small, the hydraulic motor 29 of the vehicle speed sensor unit 32 rotates at high speed, so that the oil tank 1
The flow rate to 6 increases. Therefore, the cutoff valve 2
The pressure acting on the right end of 5 is reduced, and the spring force causes the cutoff valve 25 to move to the right. Then, the oil passage to the control port 18 is opened, and the lower retainer 46 is pushed up against the elastic force of the coil spring 48. This reduces the axial dimension of the coil spring 48 and increases the torsional rigidity. When the coil spring 48 receives a twisting torque in this state, the coil spring 48 becomes difficult to twist due to the increase in the torsional rigidity, and the rotation angle between the input shaft 12 and the valve body 34 becomes relatively small. Thereby, the input shaft 12 and the valve body 3
The difference between the left and right of the oil passage between No. 4 and 4 is suppressed, and the power assist amount becomes relatively small.

The hydraulic motor 29 is used when the vehicle is running at medium or low speeds.
Since it also rotates according to the vehicle speed, the pressure acting on the right end of the cutoff valve 25 changes depending on the balance between the amount of oil flowing in from the sensor orifice 33 and the amount of oil pumped out by the hydraulic motor 29. Since the communication degree of the cutoff valve 25 changes due to the balance between this pressure and the spring force, the hydraulic pressure according to the vehicle speed acts on the lower retainer 46, and the assist amount is appropriately controlled.

FIG. 7 shows a front wheel suspension system 61 to which the variable spring rate mechanism 41 is applied. In this front wheel suspension device 61, the hub carrier 62 of the front wheel is pivotally supported on the vehicle body at its inner end via a torsion bar 64 inserted in a torque tube 63 rigidly connected to the vehicle body and has a vehicle width. Is supported by an arm 65 extending in the direction.
It can be displaced up and down by the turning motion of 5. The variable spring rate mechanism 41 is internally provided at the end of the torque tube 63 on the side opposite to the arm pivot,
The cap member 43 shown in FIG. 4 is connected to the torsion bar 64, and the output member 42 is fixed to the vehicle body together with the torque tube 63.

In this case, the length of the coil spring 48 is usually set to be the longest to enhance the riding comfort, and the brake hydraulic pressure during braking is guided to the cylinder hole 55 to reduce the length of the coil spring 48. During braking, the spring rate of the front wheel suspension device 61 increases, and changes in the vehicle attitude are suppressed. Further, for example, if the hydraulic pressure to the cylinder hole 55 is controlled according to the lateral acceleration during turning, it is possible to suppress the sinking of the wheels outside the turning circle and improve the turning performance.

Although the embodiment in which the present invention is applied to the power steering device and the suspension device has been described above, the present invention is not limited to the configuration of the above embodiment, and may be, for example, the lower retainer 4.
As the drive means of 6, a rack and pinion mechanism or a screw mechanism combined with an electric motor may be used, or a drive means by electromagnetic means may be used.

[0040]

As described above, according to the present invention, since the torsional rigidity of the coil spring can be changed as necessary, both reduction of steering force and improvement of rigidity, or ride comfort and maneuverability can be achieved. It is possible to achieve a very remarkable effect in achieving both compatibility.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a vehicle to which the present invention is applied.

FIG. 2 is an overall hydraulic circuit diagram of a power steering device to which the present invention is applied.

FIG. 3 is a vertical cross-sectional view of a rotary valve unit combined with a variable spring rate mechanism.

FIG. 4 is an exploded perspective view showing the configuration of a variable spring rate mechanism.

FIG. 5 is an operation principle diagram of the device of the present invention.

FIG. 6 is a characteristic diagram of a spring rate.

FIG. 7 is a perspective view of a main part of a front wheel suspension device to which the present invention is applied.

[Explanation of symbols]

 1 Steering Device 2 Vehicle 3 Front Wheel 4 Tie Rod 5 Steering Gear Box 6 Steering Shaft 7 Steering Wheel 11 Rotary Valve Unit 12 Input Shaft 13 Pinion 14 Steering Rack 15 Power Cylinder 16 Oil Tank 17 Return Port 18 Control Port 19 Oil Pump 20 Feed Port 21 Piston 22a / 22b Oil chamber 23a / 23b Cylinder port 24 Oil passage 25 Cut-off valve 26 Main orifice 27 Flow control valve 28 Relief valve 29 Hydraulic motor 30 Relief valve 31 Check valve 32 Vehicle speed sensor unit 33 Control orifice 34 Valve body 41 Variable Spring rate mechanism 42 Output member 43 Cap member 44 Input member 45 Upper retainer 46 Lower retainer 4 Pin 48 coil spring 49 pivot 50-54 leg 55 the cylinder bore 56 the piston 61 front wheel suspension device 62 the hub carrier 63 torque tube 64 the torsion bar 65 arm

Claims (3)

[Claims] 1. A first shaft and a second shaft which are rotatable relative to each other about the same shaft, and the first shaft and the second shaft are interlockingly connected to at least one of the rotation directions. A variable spring rate mechanism comprising: a coil spring whose ends are respectively connected to the first shaft and the second shaft; and a drive unit that changes the axial length of the coil spring. 2. The variable spring rate mechanism according to claim 1, wherein one of the first shaft and the second shaft is connected to a steering wheel, and the other is connected to a steering gear box. . 3. A variable spring rate mechanism, wherein one of the first shaft and the second shaft is connected to a vehicle body, and the other is connected to a pivotal support end of a suspension arm that supports wheels. .