JP2862134B2 - Shock absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shock absorber interposed between a vehicle body and wheels of a vehicle to attenuate vibrations from a road surface.

[Conventional technology]

As a method for improving the riding comfort of a vehicle, for example, a suspension system shown in FIG. 4 has been developed.

In this method, a spring 2 and a variable damping type hydraulic shock absorber 3 are provided between a vehicle body 1 and wheels, a displacement of the vehicle body 1 is detected by a sensor 4, a signal thereof is inputted to a controller 5, and a signal from the controller 5 is used for hydraulic pressure damping. This is for adjusting the damping force of the vessel 3.

FIG. 5 shows a structural diagram of the shock absorber 3 having a variable damping force used in the semi-active suspension. The piston portion 6 is provided with an expansion valve 7 for restricting oil flowing from the chamber A to the chamber B and a pressure valve 8 for restricting oil flowing from the chamber B to the chamber A. Further, a base valve 9 provided with a check valve for restricting oil flowing from the chamber B to the chamber C and sucking oil from the chamber C to the chamber B without resistance is provided below the cylinder. A passage 11 that bypasses the piston portion 6 is provided inside the piston rod 10 so that the opening area of the variable orifice can be opened and closed by a rotary valve 12 in a stepless manner. The rotary valve 12 is driven via a control rod 13 by a stepping motor 14 provided above the piston rod.

The operation of the variable damping type shock absorber will be described.

To obtain the highest damping force, the stepping motor 14 is driven to bring the variable orifice into a fully closed state. In the extension stroke, the oil in the chamber A flows through the extension port and the extension valve 7 to the chamber B, and due to the resistance at that time, a differential pressure is generated in the chambers A and B to generate an extension-side damping force. The oil corresponding to the rod discharge volume passes through a check valve provided in the base valve 9 and is sucked from the room C into the room B without resistance. The damping force characteristic at this time is as shown in FIG. In the compression stroke, the oil corresponding to the rod entry volume flows from the chamber B to the chamber C through the base valve 9, and the pressure in the chamber B is increased by the resistance. On the other hand, the oil in the chamber B flows to the chamber A through the pressure port and the pressure valve 8, and the resistance causes
A differential pressure is generated between the chamber and the A chamber to generate a compression damping force. The damping force characteristic at this time is as shown in FIG.

To obtain the lowest damping force, the variable orifice is fully opened. As a result, a passage is formed that bypasses the expansion valve 7 during the expansion stroke and the pressure valve 8 during the compression stroke, and the resistance when flowing from the chamber A to the chamber B or from the chamber B to the chamber A is reduced, and between the chambers A and B is reduced. , The differential pressure becomes smaller and the damping force becomes lower. The damping force characteristic at this time is as shown in FIG.

By rotating the rotary valve 12, the area of the variable orifice can be obtained in an infinite range between the fully closed and fully opened positions, so that the damping force characteristics are not changed between FIGS. You can get to the stage.

When the semi-active control shown in FIG. 4 is performed using the above-described shock absorber 3, the damping force is F, the vehicle speed is (-), the relative speed between the vehicle body and the road surface is (-), the damping force coefficient is Ce, and the optimum damping force is Ce. When the coefficient giving force is C Thus, the vehicle speed and the relative speed (-) between the vehicle body and the road surface are detected by the sensor 4, and are controlled momentarily according to the magnitude.

[Problems to be solved by the invention]

However, in the suspension system using the above-described shock absorber, the actual damping force characteristic has a strong nonlinearity, the error between the damping force (control force) obtained by control and the optimal control force is large, and the large damping coefficient is large. When it comes to Ce, it is necessary to control the small orifice area with high accuracy, which is difficult as a practical matter. To calculate Ce, the vehicle speed and relative speed (-)
When the value of (−) is small, the error of Ce becomes large (to divide), and a high-precision relative velocity detector is required.

Therefore, an object of the present invention is to provide a shock absorber in which the optimum damping force can be easily and accurately obtained in performing semi-active control of the suspension of a vehicle, and which can be controlled even by a relative speed detector with low accuracy. is there.

[Means for solving the problem]

In order to achieve the above object, a means of the present invention includes a piston rod movably inserted into a cylinder via a piston, wherein the piston defines a rod side chamber and a counter rod side chamber in the cylinder, and the cylinder and the outside of the cylinder. A reservoir is provided between the outer tube and the outer tube, and a check valve is provided on the piston to allow oil to flow only from the rod-side chamber to the rod-side chamber.The lower base valve of the cylinder is provided with oil only from the reservoir to the rod-side chamber. In a shock absorber provided with a check valve that allows the flow of air, a pipe is arranged on the upper outer peripheral portion of the cylinder via upper and lower seals, and this pipe is provided with a housing that penetrates the outer tube, and the pipe and the inside of the housing are provided. Is provided with a passage communicating between the rod side chamber and the reservoir. In which it characterized in that a proportional electromagnetic relief valve pressure is changed.

(Operation)

When the piston rod expands and contracts, the oil in the rod-side oil chamber pushes and opens the valve of the electromagnetic proportional relief valve through the passage connecting the rod-side oil chamber and the reservoir, and flows into the reservoir. At this time, the control signal applied to the electromagnetic proportional relief valve For example, a damping force proportional to the current is generated.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

A piston rod 17 is inserted into a cylinder 15 through a piston 16.
The piston 16 divides a rod side chamber 32 and an anti-rod side chamber 33 in the cylinder 15, and the two chambers 32, 33
Are connected via a check valve 30 provided on the piston 16.

The piston rod 17 passes through the center of the bearing 18 and the seal 19.

The check valve 30 allows oil to flow only from the anti-rod side chamber 33 to the rod side chamber 32.

An outer tube including an outer shell 20 and a lower cap 34 is disposed outside the cylinder 15.
A reservoir 34 is defined between 15 and the outer shell 20,
The reservoir 34 communicates with the anti-rod side oil chamber 33 via a check valve 31 provided in the base valve 22, and the check valve 31 allows oil to flow only from the reservoir 34 to the anti-rod side oil chamber 33.

A pipe 21 is disposed on the upper outer peripheral portion of the cylinder 15 via upper and lower seals, and a housing 24 is provided below the pipe 21 so as to penetrate the outer shell 20 in a lateral direction. A, a passage B and a passage C are formed, and the passage A is opened to the rod side chamber 32 through the hole 23,
Thus, these passages A, B, and C connect the rod side chamber 32 with the reservoir 34.

A case 26 is attached to the housing 24, and a plunger 27 and a poppet-type valve body 29 provided at the end thereof are movably inserted into the case 26, and a coil 25 is provided around the outer periphery of the plunger 27. Numeral 29 abuts on the exit side end sheet of the passage B so as to be freely opened and closed. Case 26 and Plunger 27
And the valve body 29 and the coil 25 constitute an electromagnetic proportional relief valve 28,
The valve element 29 is controlled by a control signal such as a current applied to the coil 25, and the pressure in the passage B is kept constant in proportion to the control signal.

The shock absorber 36 itself is connected to the wheel side via an eye 35, and the upper part of the piston rod 17 is connected to the vehicle body side.

In the extension stroke, the oil in the rod side chamber 32 flows through the passage A, the passage B, and the passage C to the three reservoirs. The flow rate Qr at this time is Qr =
(Ap−Ar) · Vp. Where Ap is the cross-sectional area of the piston,
Ar indicates the piston rod cross-sectional area, and Vp indicates the piston speed.
On the other hand, from the reservoir 34, the anti-rod side chamber 33 is
Is sucked through the check valve 31 so that the oil is filled with oil. At this time, a differential pressure is generated at the outlet of the passage B by the electromagnetic proportional relief valve 28. As a result, a differential pressure is also generated in the chambers 32 and 33. The pressure of the reservoir 34 is approximately atmospheric pressure,
Assuming that the relief pressure of the electromagnetic proportional relief valve 28 is Pr, the extension damping force Fr becomes Fr = (Ap-Ar) · Pr.

In the pressure stroke, the oil in the chamber 33 flows through the check valve 30 to the chamber 32, and the oil that has entered the rod further flows from the chamber 32 through the passages A, B, and C to the reservoir 34, and to the electromagnetic proportional relief valve 28. The oil flows in the same direction as the extension stroke, and similarly a differential pressure is generated. The flow rate Qc at this time is Qc = Ar · Vp. At this time, the pressures in the chambers 32 and 33 are the same, and the relief pressure is
Since it is equal to Pr, the compression side damping force Fc becomes Fc = Ar · Pr.

As for the characteristics of the relief valve 28, the change in the differential pressure with respect to the change in the flow rate is extremely small, so that the relief pressure Pr hardly depends on the piston speed. As a result, the relationship between the damping force and the piston speed is as shown in FIG.

On the other hand, since the relief pressure Pr is proportional to the current flowing through the coil 25, the relationship between the damping force and the current has a proportional characteristic as shown in FIG. 3 regardless of the piston speed.

〔The invention's effect〕

As described above, when the semi-active control is performed by using the shock absorber that generates the damping force proportional to the current regardless of the piston speed, the following merits occur.

Since the damping force proportional to the current is obtained, the error between the damping force (control force) obtained by the control and the optimum control force is extremely small, and accurate control can be performed.

Control It is not necessary to know the magnitude of (-), and only the sign (direction of expansion / contraction) need be known, so that control can be performed with a simple relative speed detector.

A pipe is provided on the outer periphery of the upper part of the cylinder, a housing is provided in this pipe, an oil passage is provided in the pipe and the housing, and an electromagnetic proportional relief valve is provided in the middle of the oil passage. Regardless of the cylinder length, the piston slides freely by the length of the cylinder, and can exert a hydraulic buffering force. Further, since the electromagnetic proportional relief valve can be installed at an arbitrary position with respect to the pipe, the degree of freedom of attachment to the vehicle body is large.

[Brief description of the drawings]

FIG. 1 is a longitudinal front view of a shock absorber according to one embodiment of the present invention, FIG. 2 is a graph showing a relationship between a piston speed and a damping force, FIG. 3 is a graph showing a relationship between a current and a damping force,
FIG. 4 is a schematic view of a conventional suspension system, and FIG.
The figure is a longitudinal front view of the shock absorber used in the system of FIG. 4, and FIG. 6 is a graph showing the damping force characteristics of the shock absorber of FIG. 15 …… Cylinder, 16 …… Piston, 17 …… Piston rod, 22 …… Base valve, 28 …… Electromagnetic proportional relief valve,
30, 31 ... check valve, 32 ... rod side chamber, 33 ... anti rod side chamber, 34 ... reservoir.

Claims (1)

(57) [Claims] A piston rod is movably inserted into a cylinder via a piston. The piston defines a rod side chamber and a counter rod side chamber in the cylinder, and is located between the cylinder and an outer tube provided outside the cylinder. A reservoir is provided.The piston is provided with a check valve that allows oil flow only from the rod-side chamber to the rod-side chamber.The lower valve of the cylinder is provided with a check valve that allows oil flow only from the reservoir to the rod-side chamber. In the shock absorber, a pipe is arranged on the upper outer peripheral portion of the cylinder via upper and lower seals, and this pipe is provided with a housing that penetrates the outer tube, and the pipe communicates with the rod side chamber and the reservoir. To provide a passage
A shock absorber characterized in that an electromagnetic proportional relief valve whose relief pressure changes in proportion to the current is provided in the middle of this passage.