JPS6321790Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pressure sensing type hydraulic shock absorber used in motorcycles and the like.

Conventionally, the damping force was made variable by sensing the internal pressure generated in accordance with the stroke of a hydraulic shock absorber, but the present applicant proposed Utility Model Application No. 55-107293, 55
- Proposed as No. 107294.

This is designed to make the initial load of the relief valve variable depending on the internal pressure. However, this may cause bottoming due to insufficient energy consumption of the valve device in the high piston speed range, or if the damping force of the valve device is set to obtain sufficient energy consumption when the piston speed is high, the piston speed There was a problem in that when the damping force was low, the damping force applied became excessive.

This invention was made with an eye on this problem, and its object is to provide a hydraulic shock absorber which provides optimal damping characteristics according to requirements by providing a restriction in the passage connecting the damping valve, which senses the internal pressure, and the oil chamber, thereby increasing energy consumption according to the internal pressure and piston speed.

Hereinafter, embodiments of the present invention will be described based on the drawings.

2 is a damping valve that makes the compression side damping force variable; 3 is the body of this damping valve 2 fixed to the outer periphery of the outer tube 1; Bearings 5 and 6 are disposed concentrically within the body 3, with the bearing 5 being fixed via the base portion 4, and the bearing 6 being fixed to the spring 7.
It is locked through. A spool 8 is inserted into both the bearings 5 and 6 so as to be slidable in the axial direction. In this case, the port 9 formed in the lower bearing 6 communicates the upstream chamber 10 and the downstream chamber 11. The upstream chamber 10 is an oil chamber 12 inside the outer tube 1 that contracts when the inner tube 34 is operated on the pressure side.
The downstream chamber 11 also communicates with an oil reservoir chamber 16 above the hollow pipe 15 through an oil passage 14 provided at the base end portion 13 of the outer tube.

A hollow bolt 17 screwed into the base portion 4
A spring receiver 18 is fixed to the tip of the spool 8, and a return spring 19 is interposed between the spring receiver 18 and the spool 8. This spring 19 moves the spool 8 to the bearing 6 against the hydraulic pressure.
The step portion 8a is urged toward the downstream chamber 11 so as to come into contact with the step portion 8a. The upper end surface of the spool 8 serves as a gas pressure receiving surface that receives pressure from the atmosphere or sealed pressure gas.

A valve plate 21 is attached to the lower end of the spool 8 via a screw-fitted nut 22, and is seated on a seat 23 attached to the bearing 6 to open and close the port 9.

Upstream chamber 1
0 and the downstream chamber 11 are always in communication.

The oil passage communicating the oil passage 14 and the downstream chamber 11 is formed to have a passage diameter d smaller than that of the oil passage 14, thereby forming a throttle passage 26. That is, the throttle passage 26 reduces the cross-sectional area of the flow in the flow path downstream of the damping valve 2 that communicates the downstream chamber 11 and the oil reservoir chamber 16, and increases the upstream pressure due to the throttle resistance.

Next, the effect will be explained.

In a stationary state, the damping valve 2
The opening degree is determined.

When the inner tube 34 is compressed, the oil chamber 1
2 contracts, and the hydraulic oil flows from the oil chamber 12 to the damping valve 2 due to an increase in the inrush volume of the inner tube 34.
The orifice 25, the oil passage 24, and the port 9 are separated from the upstream chamber 10 to the downstream chamber 11 and the throttle passage 2.
6 from the oil passage 14 to the oil reservoir chamber 16, and at the same time, the pressure in the oil reservoir chamber 16 increases according to the compression pressure of the gas chamber (not shown), in other words, according to the stroke position.

This pressure increase in the oil reservoir chamber 16 is caused by the spool 8
The spool 8 is urged upward (leftward in the drawing) until the pressure transmitted to the hydraulic pressure receiving surface and acting on the gas pressure receiving surface and the urging force of the return spring 19 are balanced. At this time, the spool 8 moves the valve plate 21 to the seat 2.
Therefore, the opening load of the damping valve 2 increases in accordance with its internal pressure.

On the other hand, the throttling resistance applied by the throttling passage 26 increases quadratically with respect to the change in the piston (inner tube 34) speed, and accordingly increases the pressure in the downstream chamber 11 upstream of the throttling passage 26. The spool 8 is forced upward by this pressure increase, and the opening load of the damping valve 2 further increases.
Therefore, even if the stroke position is the same, the higher the piston speed, the greater the damping force applied by the damping valve 2. For example, in the high piston speed range where bottoming occurs in a conventional hydraulic shock absorber, in addition to the pressure rise in the oil reservoir 16, the pressure applied by the throttle passage 26 rises rapidly, causing the spool 8 to drop.
This balances the gas pressure and the return spring 19 to greatly increase the initial load of the damping valve 2, thereby effectively preventing the bottoming.

On the other hand, when the piston speed is slow, the pressure increase due to the throttle passage 26 is extremely small, so the damping characteristic depends almost only on the stroke position, ensuring a soft ride.

Also, when the inner tube moves to the expansion side,
A check valve 29 attached to the lower part of the hollow pipe 15 opens against a spring 30, so that hydraulic oil flows from the oil reservoir chamber 16 to the oil chamber 12 through the port 31.

In summary, the present invention provides a restriction in the passageway that communicates with the oil sump chamber downstream of the damping valve that senses internal pressure, so the opening load of the damping valve changes in accordance with the piston speed in addition to changes in internal pressure. This results in the effect that bottoming in the piston high speed range can be prevented and steering stability can be improved without deteriorating the riding comfort in the low piston speed range.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view of a main part showing an embodiment of the present invention. 1... Outer tube, 2... Damping valve,
8... Spool, 10... Upstream chamber, 11... Downstream chamber, 12... Oil chamber, 16... Oil reservoir chamber, 19... Return spring, 21... Valve plate, 26... Throttle passage.

Claims (1)

[Scope of utility model registration request] It has an internal air chamber and an oil reservoir chamber, and is interposed in an oil chamber whose internal volume changes depending on the stroke position, and a passage through which hydraulic oil flows from this oil chamber to the oil reservoir chamber. A hydraulic shock absorber equipped with a damping valve whose opening load changes depending on the generated oil pressure, characterized in that a restriction is provided in the middle of the passage communicating the oil chamber and the oil reservoir chamber and downstream of the damping valve. Hydraulic shock absorber for motorcycles.