JPH0228286Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a compression side damping force adjustment device for a hydraulic shock absorber for a two-wheeled vehicle.

(Prior Art) A dual-tube hydraulic shock absorber used in the front fork of a motorcycle, etc., in which the compression side damping force can be adjusted according to the driving conditions was proposed by the present applicant in Utility Application No. 58-203107. It is proposed as.

As shown in FIG. 3, this double-tube hydraulic shock absorber has a hollow rod 3 interposed inside an outer tube 2, an oil reservoir chamber C inside the hollow rod 3, and an inner tube (not shown) connected to the outer tube 2. During pressure side operation, the hydraulic oil entering between the rods 3 flows out from the lower oil chamber B to the oil reservoir chamber C through the port 45.

A damping valve device 40 that applies resistance to the pressure-side hydraulic oil flowing into the oil reservoir chamber C is provided within the hollow rod 3, and is designed to generate a damping force proportional to the operating speed of the shock absorber.

In this damping valve device 40, a relief valve 27 that is slidably housed in a hollow rod 3 is seated on a valve seat 24 via a spring 31.

The rising pressure in the lower oil chamber B is transmitted to the return spring 31 through a port 45 formed in the hollow rod 3.
The relief valve 27 is opened while compressing the hydraulic fluid in the lower oil chamber B to flow out into the oil reservoir chamber C. At this time, the relief valve 27 applies resistance that is primarily proportional to the flow velocity due to the elastic restoring force of the spring 31.

On the other hand, when operating on the rebound side, check valve 4
3 opens with almost no resistance and feeds hydraulic oil from the oil reservoir chamber C into the expanding lower oil chamber B.

In this damping valve device 40, the opening pressure of the relief valve 27 can be adjusted by inserting a tool such as a screwdriver into the engagement groove 32 of the plug part 14 and rotating the rod 29 with respect to the valve case 19. is displaced in the axial direction via the threaded portion 51 to change the distance between the valve seat 24 provided on the guide 21 and the spring seat 30 provided on the upper end of the rod 29, and the spring 3
This is done by adjusting the initial load of step 1.

(Problem to be solved by the invention) However, in this case, the flow path area before and after the relief valve for the hydraulic oil passing through the relief valve 27 is not appropriately regulated based on the relationship with the maximum opening area of the relief valve 27. If this occurs, the relief valve 27 may overstroke further, causing the spring 31 to become flat, causing fluctuations in valve characteristics, or malfunction.

For example, before and after the relief valve 27, the passage through which the hydraulic oil flows is narrowed in the annular passage a between the outer circumference of the spring seat 30 and the inner circumference of the hollow rod 3, and between the outer circumference of the valve seat 24 and the hollow rod. The annular passage b with the inner periphery of No. 3, etc.
If the preset maximum opening area c of the relief valve 27 is smaller than the area of these passages a and b, the flow rate of hydraulic oil will increase even after the relief valve 27 reaches its maximum opening area. and,
The pressure difference between the front and rear becomes even larger, and the relief valve 27 lifts further.

In this way, when the relief valve 27 strokes beyond the normal lift range, the spring 31 of the relief valve 27 is excessively compressed.
The spring 31 may become flat or the relief valve 27 may malfunction.

To avoid these, the relief valve 27
A stopper or the like is required to forcibly stop the movement of the valve when the relief valve 27 reaches its maximum opening area. Also, if a stopper is provided, it will prevent the relief valve 27 from making abnormal noise every time it collides with the stopper. This creates new problems.

(Means for Solving Problems) The present invention was proposed to solve such problems, and consists of a hollow rod provided inside the outer tube, an oil reservoir chamber formed inside the hollow rod, and an oil reservoir chamber formed inside the hollow rod. A hydraulic shock absorber is equipped with a damping valve located inside the hollow rod that opens in response to the differential pressure across the valve, in the hydraulic oil flow path that connects the oil chamber outside the rod with the oil reservoir chamber inside. A throttle portion having an area smaller than the maximum opening area of the valve at a predetermined stroke position of the valve is provided upstream or downstream of the valve.

Therefore, after the damping valve reaches its maximum opening area after a predetermined stroke, the maximum flow rate will be regulated at the throttle part, and the differential pressure across the damping valve will not increase any further. The valve will stop at the stroke position of maximum opening area.

(Embodiment) In the embodiment shown in FIG. 1, the relief valve 27
an outer periphery of the valve seat 24 located upstream of the
A constriction part 10 having an area smaller than the area when the relief valve 27 reaches its maximum opening area is formed between it and the inner periphery of the hollow rod 3 facing this.

After the relief valve 27 reaches its maximum opening degree, this constriction part 10 restricts the flow of the hydraulic oil beyond the maximum opening degree.

In the embodiment shown in FIG. 2, the relief valve 27
A constricted portion 11 similar to that described above is provided between the outer periphery of the spring seat 30 and the inner periphery of the hollow rod 3 facing the outer periphery of the spring seat 30, which is located downstream of the spring seat 30.

In this way, the area when the relief valve 27 reaches the maximum opening area after a predetermined stroke,
In other words, the area of the flow path 13 between the seat 24 and the relief valve 27 is larger than that of the constricted portion 10 or 1.
Since the area of 1 is set small, the flow rate of the hydraulic oil is controlled by the relief valve 27 until the relief valve 27 reaches its maximum opening area, but when the flow rate attempts to increase further, the constriction part 10 or 11 will close. This becomes the maximum resistance of the flow path, and the differential pressure across the relief valve 27 does not become larger than that.

For this reason, the relief valve 27, which strokes according to the differential pressure across the relief valve 27, increases its stroke amount according to the flow rate until it reaches the maximum opening area, but once the maximum opening area is reached,
It will automatically stop at that stroke position and will not stroke any further.

Therefore, the spring 31 of the relief valve 27 can be prevented from becoming flat due to overstroke and malfunction of the valve can be prevented, and its life can be extended. Furthermore, since there is no need to provide a stopper or the like, the valve can be No abnormal noise is generated due to collision.

(Effects of the invention) As described above, according to the invention, since a constriction part with an area smaller than the maximum opening area of the relief valve is provided upstream or downstream of the relief valve, the relief valve can be opened without providing a stopper or the like. Overstroke can be prevented, and valve malfunction and spring fatigue can be avoided.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views showing embodiments of the present invention, and FIG. 3 is a sectional view of a conventional example. 2... Outer tube, 3... Hollow rod, 1
0,11... Throttle part, 24... Valve seat, 2
7...Relief valve.

Claims (1)

[Scope of utility model registration request] A hollow rod is placed inside the outer tube,
An oil reservoir chamber is formed inside the hollow rod, and a hydraulic oil flow path connecting the oil chamber outside the hollow rod and the oil reservoir chamber inside the hollow rod is provided with a valve located inside the hollow rod that responds to the differential pressure across the valve. A hydraulic shock absorber for a two-wheeled vehicle, characterized in that the hydraulic shock absorber is equipped with a damping valve that opens, and a throttle portion having an area smaller than the maximum opening area of the valve at a predetermined stroke position of the valve is provided upstream or downstream of the damping valve. vessel.