JPH05155224A - Suspension device - Google Patents

Abstract

PURPOSE:To obviate the need to change over a damping-force adjusting actuator at a high speed for reducing the frequency of changeover, and to enhance the durability of equipment by providing a controller for controlling the amount of rotation of a rotary valve so that the communication holes on the extension and compression sides are opened or closed in response to the magnitude of the vehicle speed. CONSTITUTION:A rotary valve is provided, in which the compression-side communication hole is opened when the extension-side communication hole is closed, and the compression-side communication hole is closed when the extension-side communication hole is opened, and also both the extension-side and compression- side communication holes are opened as occasion demands. Then, a controller 9 controls the amount of rotation of the rotary valve in response to the magnitude of the vehicle speed to open or close the communication holes on the extension and compression sides. By the opening/closing action at that time, the compression-side damping force is softened when the extension-side damping force is hard, while the compression-side damping force is hardened when the extension-side damping force is soft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension device for switching and controlling an extension side damping force and a compression side damping force according to a vehicle speed.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional suspension device. As for this, 1 is the car body,
Reference numeral 2 is a wheel, and a spring 3, a damping force variable damper 4 and a vehicle height sensor 5 are mounted between them, and an acceleration sensor 6 for detecting the vertical acceleration is provided on the vehicle body 1.

Further, a tire 8 as a spring element exists between the wheel 2 and the road surface 7. The signals of the acceleration sensor 6 and the vehicle height sensor 5 are input to the controller 9, and the controller 9 drives the damping force switching actuator provided in the damping force variable damper 4 to switch the damping force between two levels, high and low. ..

Next, the damping force variable damper 4 used in the conventional suspension device will be described with reference to FIG. The inside of the cylinder 11 is partitioned by a piston 12 into two chambers, A and B, which are upper and lower chambers. The cylinder 11 and the outer shell 12 form a C chamber as a reservoir.

Further, the piston 12 is a piston rod 13
Is fastened to one end of the piston rod 13 with a screw, the other end of the piston rod 13 penetrates through the bearing 14 and the seal 15 and projects, and is attached to the vehicle body 1 side.

On the other hand, the outer shell 1 is on the cylinder 11 side.
2 It is attached to the wheel side by an eye 16 welded to the lower part. A base valve including a pressure valve 17 that generates a damping force when compressed and a check valve 18 that sucks oil from the C chamber to the B chamber when the cylinder 11 is extended is provided below the cylinder 11.

Further, the piston 12 is provided with an extension port 19 which serves as a passage when oil flows from the A chamber to the B chamber during extension, and an extension valve 20 which generates an extension side damping force from the B chamber to the A chamber during compression. A pressure port 21 that serves as a passage when oil flows and a pressure valve 22 that generates a compression side damping force are provided.

The inside of the piston rod 13 is hollow, the control rod 23 and the rotary valve 24 are inserted into the inside, and the rotary valve stopper 25 for preventing the rotary valve 24 from falling is press-fitted. ing.

Further, the piston rod 13 is provided with a communication hole 26 on the A chamber side, and the rotary valve 24 is provided with an orifice 27 for opening and closing the communication hole. In the open state, the A chamber and the B chamber are pistons. The orifice 27 provided in the rotary valve 13 communicates with each other through the bypass passage 28 in the rod 13, and regulates the bypass flow rate.

The control rod 23 is sealed by an O-ring 29 provided in the upper piston rod 13, fitted with the shaft of a damping force switching actuator 30, and drives the actuator 30 to rotate the control rod 23. As a result, the bypass passage 28 can be opened and closed.

Next, the operation of the damping force variable damper will be described. First, in order to obtain a high damping force, the damping force switching actuator 30 is driven to rotate the rotary valve 24, and the bypass passage 28 is closed. In the stretching stroke, the oil in the chamber A flows through the stretching port 19 and the stretching valve 20 into the chamber B.

Therefore, the expansion side damping force is generated due to the generated differential pressure between the A and B chambers. Here, the oil corresponding to the volume in which the piston rod 13 projects to the outside of the cylinder 11 is replenished from the chamber C to the chamber B through the check valve 18 of the base valve.

On the other hand, in the compression stroke, the piston rod 13
The oil that has entered the cylinder 11 flows into the C chamber through the pressure valve 17 of the base valve. At this time, the pressure in the chamber B rises due to the differential pressure generated by the pressure valve 17.

On the other hand, the oil in the B chamber also flows through the pressure port 21 and the pressure valve 22 into the A chamber. The pressure side damping force is generated by the pressure difference between the A and B chambers and the pressure in the B chamber that are generated at this time. This is the hard state.

Next, the rotary valve 24 is rotated,
When the bypass passage 28 is communicated, an expansion of the piston 12 and a flow of oil that bypasses the pressure valves 20 and 22 occur during the high damping force.

Since this flow is parallel to each valve, the flow rate of the piston 12 extending and the pressure valves 20 and 22 is reduced by the bypass flow rate, and the extension stroke and the pressure stroke are different between the chambers A and B. The pressure becomes smaller. As a result, the damping force becomes low, that is, the soft damping force, when the damping force is high.

FIG. 7 shows the damping force characteristic at this time. As can be seen from this figure, the contraction-side damping force becomes hard when the extension-side damping force is hard, and the contraction-side damping force becomes soft when the extension-side damping force is soft. This is a characteristic of the conventional damping force variable damper.

Next, a method of controlling the damping force variable damper 4 will be described. As shown in FIG. 1, displacements of the vehicle body 1 and the wheels 2 are defined as x and y for convenience (arrow directions are positive), xa and ya indicate respective velocities, and xb and yb indicate respective accelerations.

Therefore, focusing on the force acting on the vehicle body 1, when x> 0 (the vehicle body 1 is moving upward), xa-y
If a> 0 (the damper is extended), a damping force acts in the direction opposite to the movement direction (lower side) of the vehicle body 1 to provide damping force for the vehicle body, but xa-ya <0 ( When the damper is contracted), the damping force acts in the movement direction of the vehicle body 1, and as a result, the damping force becomes the exciting force. Similarly, when xa <0, the damping force may be the damping force and the exciting force.

Therefore, when xa is taken as the vertical axis and xa-ya is taken as the horizontal axis, it is divided into four quadrants, as shown in FIG. 8A, the first and third quadrants have damping action, and the second and fourth quadrants. Will give a vibrating effect.

Therefore, as shown in FIG. 8 (b), a control method has been proposed in which the damping force is hard when the damping force acts as the damping force and is soft when the damping force acts as the exciting force. ..

When this is expressed by an equation, xa (xa-ya)
When> 0, the damping force is hard, and when xa (xa-ya) <0, the damping force is soft. By controlling in this way, the riding comfort of the vehicle is improved.

Here, the value of xa is the signal xb of the acceleration sensor.
Is obtained by integrating by the integrator 9a in the controller 9, and the value of xa-ya is obtained by differentiating the signal xy of the vehicle height sensor by the differentiator 9b. And
The arithmetic processing / drive circuit 9c outputs a predetermined damping force adjustment signal based on the outputs of the differentiator 9b and the differentiator 9a.

[0024]

However, in general, xa changes at a frequency of 1 Hz, which is a natural frequency determined by the mass of the vehicle body and the suspension spring constant, but xa-ya is an instantaneous input from the road surface 7 or The sign of positive / negative (extension, pressure) changes at a fairly high frequency due to resonance between the wheel 2 and the tire 8.

Therefore, it is necessary to switch the damping force quite frequently. Therefore, unless the damping force adjusting actuator is switched at high speed, the control effect is reduced, which requires considerable durability of the actuator and the damper, and the relative speed between the vehicle body 1 and the wheels 2 during control. Since (xa-ya) is required, a vehicle height sensor (or relative speed sensor) 5 is required for each wheel 2, which causes a problem that the system cost increases.

The present invention has been made in view of the above-mentioned conventional problems and eliminates the need for switching the damping force adjusting actuator at high speed, and reduces the switching frequency to improve the durability of the device. It is an object of the present invention to provide a suspension device that is capable of achieving the simplification of the configuration and the cost reduction by eliminating the vehicle height sensor.

[0027]

SUMMARY OF THE INVENTION A suspension device according to the present invention has a piston that divides a cylinder, which is mounted on the wheel side, into two chambers, an upper chamber and a lower chamber. The piston has one end and the other end is mounted on the vehicle body side. Piston rod
A communication hole that is independently provided on the piston rod for each of the expansion side and the compression side and that communicates the two chambers, and the communication hole on the compression side is opened when the communication hole on the expansion side is closed, and the communication on the expansion side is performed. When the hole is opened, the communication hole on the pressure side is closed, and a rotary valve that opens each communication hole on the extension side and the pressure side is provided if necessary, and a controller is used to change the above according to the magnitude of the vehicle body speed. The rotation amount of the rotary valve is controlled so as to open and close the extension side and pressure side communication holes.

[0028]

According to the controller of the present invention, the amount of rotation of the rotary valve is controlled in accordance with the speed of the vehicle body to open and close the communication holes on the extension side and the compression side. When hard, the compression side damping force is made soft, and when the extension side damping force is soft, the compression side damping force becomes hard.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a vehicle body, 2 is a wheel, and a spring 3 and a damping force variable damper 4 are mounted between them,
Further, the vehicle body 1 is provided with an acceleration sensor 6 that detects vertical acceleration.

Further, a tire 8 as a spring element exists between the wheel 2 and the road surface 7. A signal from the acceleration sensor 6 is input to the controller 9, and the controller 9 drives a damping force switching actuator provided in the damping force variable damper 4 to switch the damping force between high and low stages.

Further, 9a is an integrator for integrating the output of the acceleration sensor 6, and 9c is an arithmetic processing / driving circuit for calculating and outputting the damping force adjustment signal of the damping force variable damper 4 based on the output of the integrator 9a. is there. In the present invention, the differentiator 9b and the vehicle height sensor 5 in FIG. 5 are omitted.

FIG. 2 shows details of the damping force variable damper used in the present invention. The same components as those described with reference to FIG. 6 are designated by the same reference numerals, and the duplicate description thereof will be omitted.

That is, in the present invention, the piston portion is provided with two extension bypass passages 31 and pressure bypass passages 32.
An extension sub-valve 33 and a pressure sub-valve 34 are provided at the ends of the bypass passages 31 and 32, respectively.

Further, the piston rod 13 has an extension communication hole 3
5 and a pressure communication hole 36 are provided, and each is opened and closed by the rotary valve 24. As shown in FIG. 3, the opening of the rotary valve 37 is P-
The P section and the QQ section are provided so that their phases are shifted, and three damping force modes can be taken.

That is, in FIG. 3, the extension communication hole 35 is closed and the pressure communication hole 36 is open in the mode R, the extension and pressure communication holes 35 and 36 are both open in the mode S, and the extension communication hole is in the mode C. It is set so that 35 is opened and the pressure communication hole 36 is closed. In addition, the damping force actuator 38 is 3
It is possible to switch between stages, and each mode can be selected.

Next, the operation will be described. First, the operation of the damping force variable damper will be described. In mode R, the extension communication hole 35 is closed and the pressure communication hole 36 is open.

Therefore, in the extension stroke, oil does not flow into the extension bypass passage 31, and the oil in the A chamber is transferred to the extension port 19 of the piston 12.
It flows through the extension valve 20 into the chamber B. The differential pressure at this time generates an extension-side damping force, and this damping force has a hard characteristic.

On the other hand, since the pressure communication hole 36 is opened in the pressure stroke, the oil flow from the B chamber to the A chamber flows through the pressure port 21 and the pressure valve 22 of the piston 12 and the pressure bypass passage 32. It is divided into a flow through the communication hole 36 and the pressure sub-valve 34. As a result, the pressure difference between the A and B chambers becomes small, and the damping force becomes soft.

Further, in mode S, both the extension communication hole 35 and the pressure communication hole 36 are open, and a flow that bypasses the piston portion is generated in both, so both the extension side and the compression side damping force are in a soft state. In mode C, the extension communication hole 35 is open and the pressure communication hole 36 is closed. Therefore, a flow that bypasses the piston portion occurs only during the extension stroke, and as a result, the extension side damping force becomes soft and the compression side damping force becomes hard.

Further, in any mode, in the extension stroke, the oil corresponding to the protrusion of the piston rod 13 is replenished from the chamber C to the chamber B through the check valve 18 of the base valve, and in the compression stroke, the amount of the piston rod 13 entering. The oil flows through the pressure valve 17 of the base valve to the C chamber, and the pressure difference in the B chamber causes the pressure in the B chamber to rise, as in the conventional case.

Next, the control method will be described. In the conventional control method, when xa> 0, xa-ya> 0 (damper extended state), hard control is performed, and when xa-ya <0 (damper compressed state), soft control is performed.

This is because, when the conventional damping force variable damper is hard in the extension stroke, it is hard in the compression stroke as well, so it is necessary to switch the damper depending on whether xa-ya is positive or negative.

In the damping force variable damper of the present invention, when the extension stroke is hard, the pressure stroke is automatically softened, so that it is not necessary to switch the damping force depending on whether xa-ya is positive or negative, and xa> 0. In this case, the extension side damping force should be controlled hard (mode R). Similarly, xa <
When it is 0, the compression side damping force may be controlled to be hard (mode C).

That is, the relative speed xa between the vehicle body 1 and the wheels 2
Regardless of −Ya, if the mode R or the mode C is selected depending on whether the speed xa of the vehicle body 1 is positive or negative, the same control effect as the conventional one can be obtained. Moreover, since the speed change of the vehicle body 1 is a relatively slow vibration of about 1 Hz, a sufficient effect can be obtained even if the damping force switching speed of the actuator is relatively slow, and the switching frequency is low.

Further, when the input frequency from the road surface 7 becomes high frequency, the lower the damping force, the smaller the transmission force to the vehicle body 1 and the better the riding comfort. At high frequencies, vehicle speed xa
Becomes smaller, the mode is switched to the mode S in which the damping force is low on both the extension side and the compression side.

FIG. 4 shows a summary of the above control rules. By controlling in this way, it becomes possible to improve the riding comfort and the switching frequency can be extremely reduced.

In the above embodiment, the damping force is switched in three steps, but it is switched in two steps and the mode R is set.
It is needless to say that the mode C and the mode C may be switched only by the positive / negative of the vehicle speed xa.

[0048]

As described above, according to the present invention, a piston that divides the inside of a cylinder, which is mounted on the wheel side, into upper and lower chambers, and has the piston at one end and the other end is mounted on the vehicle body side. A piston rod, a communication hole independently provided on the piston rod for each of the expansion side and the compression side, and communicating with the two chambers, and when the communication hole on the expansion side is closed, the communication hole on the compression side is opened to extend the expansion. When the communication hole on the side is opened, the communication hole on the compression side is closed, and a rotary valve that opens each communication hole on the extension side and the compression side as necessary is provided. Accordingly, since the rotation amount of the rotary valve is controlled so as to open / close the extension side and compression side communication holes, the actuating force is changed by switching the damping force only by the magnitude of the vehicle body speed. Since it is not necessary to switch the controller at high speed, a small and inexpensive actuator can be used, and the frequency of switching the damping force is reduced, which improves the durability of the device and eliminates the need for a vehicle height sensor. The practical effect that it can be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a suspension device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a damping force variable damper according to the present invention.

FIG. 3 is an explanatory view showing the relationship between the open / closed state of the expansion force communication hole and the expansion force damping force of the variable damping force damper according to the present invention.

FIG. 4 is an explanatory table showing a vehicle speed limit law in a damper mode according to the present invention.

FIG. 5 is a block diagram showing a conventional suspension device.

FIG. 6 is a cross-sectional view showing the damping force variable damper in FIG.

FIG. 7 is a graph showing damping force characteristics of a conventional damping force variable damper.

FIG. 8 is an explanatory diagram showing a relationship between an acting force on a vehicle body and a control law by a conventional damping force variable damper operation.

[Explanation of symbols]

 1 vehicle body 2 wheels 9 controller 11 cylinder 12 piston 13 piston rod 35, 36 communication hole 37 rotary valve A, B 2 chambers

Claims (1)

[Claims] 1. A piston that divides the interior of a cylinder, which is attached to a wheel side, into two chambers, an upper and a lower chamber, and a piston rod having the piston at one end and the other end attached to the vehicle body side.
The piston rod is provided independently for each of the extension side and the compression side and communicates with the two chambers, and the communication hole on the compression side is opened when the communication hole on the extension side is closed to open the communication on the extension side. A rotary valve that closes the communication hole on the pressure side when the hole is opened and opens each communication hole on the extension side and the pressure side as necessary, and a communication hole on the extension side and the pressure side according to the magnitude of the vehicle body speed. And a controller for controlling the rotation amount of the rotary valve so as to open and close the suspension device.