JPH0243056B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in hydraulic shock absorbers for vehicles.

Hydraulic shock absorbers used in conventional motorcycles and the like generally have an air chamber and an oil reservoir chamber inside, and are designed to compensate for the intrusion volume of the piston rod by contraction of the air chamber. In this case, the damping force during compression side and expansion side operation is generated according to the piston speed, and as the speed increases, a higher damping force can be obtained, but the damping force depends on the piston position, that is, the stroke position. It never changed.

For example, the following problems arose. In other words, in hydraulic shock absorbers for street vehicles, the damping force is set relatively low because the road surface has small undulations.
Improves responsiveness. However, when cornering, the vehicle body sinks, and if the damping force is small in this sunken state, handling becomes extremely poor. Therefore, while reducing the damping force of the front and rear forks at around 1G, it is necessary to improve the ground contact of the larger vehicle body during cornering.

Hydraulic shock absorbers for off-road vehicles have a large stroke and have large undulations on the road surface, so the damping force during normal driving is also set to be relatively large.

However, this damping force also provides resistance to the extension operation from near the maximum compression, so during the extension operation, it picks up bumps on the road surface and can cause the tire to bottom out.

Furthermore, in the case of a loaded vehicle, it is necessary to adjust the damping force between empty and loaded vehicles.

Therefore, in order to solve these problems, the spring load of the suspension is detected and the damping force is variably adjusted according to the spring load, as disclosed in Utility Application No. 57-21730 by the present applicant. It has been proposed to do so.

To explain the configuration with reference to FIG. 1, 1 is an inner tube, 2 is a cylinder connected at its base end to an outer tube (not shown), and 3 is a piston part, and the cylinder 2 is connected to the inner tube 1 via the piston part 3. Slide around.

Next, at an upper position of the piston part 3, a valve holder 12 having a side hole 12a in the upper circumferential surface of the cylinder body receives the elastic force of the detection spring 7 housed between it and a spring receiver 19 (described later). The sheet portion 13 and the guide portion 14 are fitted into the inside thereof.

A passage 15 and a central hole 16 are formed in the seat part 13, and a check valve 8 is disposed on the front side of the passage 15 and is biased by a check spring 17, which opens without resistance when the valve is extended. A bolt 18 is slidably inserted upward into the central hole 16.

The lower part of the bolt 18 is defined by a large diameter part 18a that slides into the central hole 16 of the seat part 13 and a small diameter part 18b above the large diameter part 18a. A spring receiver 19 is inserted in the upper part of the small diameter part 18b, and a relief valve 9 is inserted in the lower part, and an internal spring 11 is housed between them. The relief valves 9 are respectively locked by step portions 18a' of the large diameter portion 18a.

The relief valve 9 is composed of a plate valve portion 21, a washer 24, and a spring receiving portion 22.

On the other hand, the spring receiver 19 is positioned according to the balance between the suspension spring 6 that urges the extension side and the detection spring 7 that urges the compression side, and at the time of maximum extension shown in the figure, the relief valve 9 and A clearance of δ is set between the check valve 8 and the check valve 8.

Further, even if the detection spring 7 is brought into close contact with the inner spring 11 during the compression operation, the internal spring 11 can be further bent. Note that A is the oil sump chamber and B is the inner tube 1.
This is an oil chamber defined between the cylinder 2 and the cylinder 2.

Therefore, now to explain the damping force characteristics of this hydraulic shock absorber with reference to curve B in FIG. 3, the clearance δ between the relief valve 9 and the check valve 8 is large.
When the vehicle is running at around 1G, the relief valve 9 hardly functions, so the generated damping force is small and a soft ride is obtained.

On the other hand, when the spring load increases, such as when loading a vehicle, the inner tube 1 relatively descends, and the clearance δ decreases. That is, if a load exceeding the balance with the detection spring 7 side is applied to the suspension spring 6, the bolt 18 is pushed down via the internal spring 11 of the relief valve 9, so the clearance δ becomes smaller. As a result, the relief valve 9 provides resistance to the hydraulic oil flowing from the oil chamber B to the oil reservoir chamber A via the passage 15, and an appropriate damping force is obtained (region of stroke 1). Even if the clearance becomes δ=0,
Furthermore, since the internal spring 11 is bent, the relief valve 9
The set load is further increased, so that, for example, when the shock absorber is about to bottom out, a very high damping force is generated, which, while effectively preventing this, makes the shock absorber too stiff in the second half of the stroke. This can be effectively avoided using the relief function described above.

In addition, when hydraulic oil flows from oil sump chamber A to oil chamber B during expansion side operation, even if the clearance of relief valve 9 is zero, check valve 8 is pushed downward and opens, so oil can flow smoothly. can be inhaled.

However, when such conventional hydraulic shock absorbers are applied to front forks with long strokes, the above-mentioned relief function is effective in preventing them from becoming too hard in the latter half of the stroke. On the other hand, in the case of a front fork with a short front fork, etc., the above-described relief function unnecessarily complicates the structure, resulting in an increase in assembly man-hours and the number of parts, resulting in high costs.

In other words, in a small stroke type hydraulic shock absorber, the stroke l from the start of effect (marked with *) to the time when it is applied to the oil hole rod (marked with ☆) in Fig. 3 is small, and the change in damping force F does not become that large. Therefore, the relief function described above is not required.

Therefore, the present invention is configured such that the compression side damping force corresponding to the above-mentioned relief valve is simply held in a floating manner between the free ends of the suspension spring and the position detection spring opposing the suspension spring, without using a relief spring. By doing so, we have simplified the structure and made it into a cassette while maintaining the actual functions as before, and our aim is to provide a hydraulic shock absorber suitable for achieving a small stroke that can reduce costs. do.

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 2A, a spool 30 constituting the compression damping force 9' is integrally screwed onto the shaft (bolt) 18 via a collar 37.

This spool 30 is also shown in FIG. 2B, and a notched groove 31 extending in the axial direction is symmetrically formed on the lower outer periphery of the cylindrical body.

The cutout groove 31 has a relatively deep inlet portion 32 at the groove bottom and an outlet portion 32 at the shallow groove bottom.

The outer circumference of the spool 30 is the valve holder 1.
The outlet portion 33 of the notch groove 31 is normally located above the seat portion 36, and a sufficient cross-sectional area of the flow path is ensured.

The spool 30 is connected to a suspension spring 6 whose base end is supported on the end wall of the inner tube 1 via a spring receiving part 19' integrally formed thereon, and a suspension spring 6 whose base end is supported on the end wall of the inner tube 1. is held floating at its free end with the position detection spring 7 carried by the valve holder 12. Normally, it is urged toward the extension side by the position detection spring 7, and the force at this time is maintained by the stepped portion of the collar 37 and a valve stopper 38, which will be described later.

A cylindrical check valve 8a is interposed on the inner periphery of the valve holder 12, and is biased via a check spring 17 so as to come into contact with a valve stopper 38.

A valve hole 39 is opened in the peripheral wall of the valve holder 12, and the check valve 8a is pushed up during the expansion side operation, and hydraulic oil is sucked into the oil chamber B side through the valve hole 39.

Other parts that are the same as those in FIG. 1 are given the same reference numerals, and their functions will be explained next.

During the compression side operation, the hydraulic oil on the oil chamber B side corresponding to the intrusion volume of the inner tube 1 passes through the inside of the cylinder 2, passes through the compression side damping force 9' from below to above, and flows into the oil sump chamber A. .

At this time, as shown in FIG. 2A, when the average load of the hydraulic shock absorber is small and the amount of deflection of the suspension spring 6 is small, the spool 3 of the adjustable damping force 9' is It is pushed back by the position detection spring 7 and is located at the top together with the bolt 18.

In this state, the notch groove 31 is wide open and the generated damping force is around 1G, as shown by curve A in Figure 3.
Provides a small and soft ride.

On the other hand, if the average load of the hydraulic shock absorber increases or the stroke amount increases due to the impact input at that time, the suspension spring 6 will be greatly deflected, and when the position detection spring 7 is pushed down, the bolt 18
At the same time, the spool 30 descends, and the initial opening degree (clearance δ) of the compression side damping force 9' changes.

In other words, the clearance δ of the compression side damping force 9' gradually decreases according to the load difference between the suspension spring 6 and the position detection spring 7, and as a result, the flow path resistance applied to the hydraulic fluid increases in the latter half of the stroke, causing the generated damping. The force is increased by the aperture characteristic without a relief function (see stroke l of curve A in Fig. 3).

In this way, a relatively high damping force is generated in the region where the compression stroke of the hydraulic shock absorber is large, thereby improving maneuverability. Regarding this damping force, the notch groove 31 of the spool 30
By changing the shape, cross-sectional area, etc., various adjustments can be made, and since the insert-type spool 30 moves forward and backward while being guided by the seat portion 36, the damping force generation effect is also stabilized. When operating on the extension side, the check valve 8a opens against the check spring 17 and sucks the hydraulic oil into the oil chamber B side with almost no resistance.

Of course, if the pressure side air chamber 9' is fully open at this time (the state shown in FIG. 2), the hydraulic oil will also flow from this portion.

In this embodiment, the relief function that is unnecessary in the small stroke type hydraulic shock absorber is abolished, so the number of parts is reduced due to the absence of a relief spring, etc. In addition, the ease of assembly is improved by making the compression side damping force 9' into a cassette. Productivity can be improved by inserting and mounting a pre-assembled guide part 14 etc. into the inner tube 1, and this and the reduction in the number of parts can significantly reduce costs.

As explained above, according to the present invention, the substantial function of making the damping force generated in the vicinity of 1G relatively weak, while obtaining a relatively strong damping force in the stroke region when compressed by a load etc. is the same as before. It is possible to further stabilize the compression side damping force characteristics while maintaining the same, and to reduce costs by simplifying the structure, thereby providing a hydraulic shock absorber suitable for a small stroke type.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the main parts of a conventional device, Fig. 2A is a sectional view showing an embodiment of the present invention, Fig. 2B is a front view of the compression side damping valve spool, and Fig. 3 is a sectional view of the compression side damping valve. FIG. 1...Inner tube, 2...Cylinder, 1
5... Passage, 9'... Compression side damping valve, 30... Spool, 31... Notch groove, 19'... Spring receiving part,
36... Tip seat portion, 6... Suspension spring, 7...
Position detection spring, δ... Clearance (initial opening degree).

Claims (1)

[Claims] 1. In a hydraulic shock absorber that has a cylinder in which an inner tube is slidably inserted into an outer tube and has a piston at its upper end that slides into contact with the inside of the inner tube, hydraulic oil flows out as the inner tube contracts. A passage is formed in the piston portion, and a compression damping valve is disposed in the passage, and the compression damping valve is opposed to the suspension spring so that the initial opening degree of the compression damping valve changes depending on the amount of compression of the suspension spring. The compression side damping valve is held floating between the free end portion of the position detection spring, and the compression side damping valve is brought into contact with a spool having a notch groove extending in the axial direction at the lower end portion and the upper end of the piston portion. A hydraulic shock absorber comprising: a valve holder having a tip seat portion that fits into the lower end of the spool;