JPH0758105B2 - Hydraulic shock absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a damping force generation mechanism for obtaining a damping force depending on a stroke position in a hydraulic shock absorber.

(Prior Art) In many hydraulic shock absorbers, an orifice, a valve, or the like is provided in a flow path of hydraulic oil that accompanies expansion and contraction, and a damping force is generated by these resistances to the oil flow. As such a shock absorber, for example, like the hydraulic shock absorber shown in FIG. 8, a piston 3 is formed at the tip of an inner tube 2 inserted into an outer tube 1 and is damped so as to face an oil chamber 5 below the piston 3. Some have valves 20 and orifices 21. In this case, when the piston 3 operates on the pressure side, the hydraulic oil in the oil chamber 5 passes through the damping valve 20 and the orifice 21 to generate a damping force, and at the same time, the oil reservoir chamber 8 provided on the upper portion of the inner tube 2 and the piston It flows into the upper oil chamber 6. In general, the resistance due to the contraction flow of the valve, the orifice, etc. increases with the flow rate, so in such a shock absorber, the damping force generated increases as the sliding speed of the piston 3 increases.

(Problems to be solved by the invention) By the way, when the centrifugal force is applied during cornering or when the weight of the vehicle body is large, the suspension spring 22 interposed between the outer tube 1 and the inner tube 2 is largely bent. Therefore, the piston 3 travels in a state of deeply penetrating into the outer tube 1 as compared with the normal time. However, in this state, the allowable range of the compression side stroke is narrow, and therefore, when the piston 3 penetrates further into the outer tube 1 due to impact or braking, the piston 3 is likely to bottom up and, as a result, the vehicle's grounding performance and maneuverability are reduced. There was a risk of damage. In order to eliminate such an inconvenience, it is sufficient to set the damping force in the latter half of the stroke to a large value, but with the shock absorber having the above structure, the damping force corresponding to the piston speed can be obtained, but the damping force can be changed according to the stroke position. Was difficult to raise.

An object of the present invention is to provide a hydraulic shock absorber in which the damping force increases in the latter half of the stroke regardless of the piston speed, in order to solve such problems in the hydraulic shock absorber.

(Means for Solving Problems) According to the present invention, a piston member is slidably inserted inside a cylinder member, and an oil passage is provided in a hydraulic oil passage that allows hydraulic oil to flow as the piston member slides. In a hydraulic shock absorber having a damping valve that resists, the damping valve is configured to be displaceable with respect to a hydraulic oil passage, and the damping valve is supported by a piston member and has a small maximum spring load.
And a spring B supported by the cylinder member and having a large maximum spring load in opposition thereto, and the spring A comes into close contact with the axial direction of the spring during the compression stroke of the piston member, and the damping valve It was set to be displaced to the pressure side together with.

(Operation) When the piston member slides to the pressure side due to the compression operation of the shock absorber, the springs A and B bend, and the damping valve sandwiched between the two is relatively displaced to the piston member side. However, since the spring A comes into close contact with and becomes the most compressed state in the middle of the compression stroke, the damping valve moves integrally with the piston member at a compression position higher than that. In this way, even if the sliding speed of the piston member is constant, after the relative displacement of the damping valve is restricted, the flow rate of the damping valve increases and the damping valve generated in the damping valve also increases.

(Embodiment) FIGS. 1 to 7 show an embodiment of the present invention.

In FIG. 1, 1 is an outer tube as a cylinder member, 2 is an inner tube having a piston 3 formed on the outer circumference of the tip, an oil chamber 5 is formed below the piston 3, and an oil chamber 6 is formed above. The oil chambers 5 and 6 communicate with each other through a path (not shown), and the oil chamber 5 passes through an oil passage 7 in the inner tube 2 that opens inside the piston 3 to an oil reservoir chamber 8 in which gas is sealed above the inner tube 2. Communicate. Suspension springs A and B are interposed in series between the upper end of the inner tube 2 and the bottom surface of the outer tube 1 through the oil passage 7, and in the oil passage 7 between these suspension springs A and B. The damping valve 9 is sandwiched. In addition,
The spring A has a smaller maximum spring load than the spring B, and has the property of being more easily bent under the same load. The damping valve 9 comprises a valve body 11 biased by a spring 10 in the direction of the oil chamber 5 and a valve seat 12 for seating the valve body 11 around a rod 13. As shown in FIG. It has the property of increasing the pressure difference, that is, the resistance. The spring 10 is supported by a nut 14 that is screwed onto the tip of the rod, and the valve seat 12 is formed in a seat 15 fixed to the outer circumference of the rod 13. The outer peripheral portion of the seat 15 is in sliding contact with the inner peripheral surface of the inner tube 2, and one end of the suspension spring A from the oil reservoir chamber 8 side and one end of the suspension spring B from the oil chamber 5 side contact the seat 15 respectively. The damping valve 9 is held so as to be displaceable in the axial direction. The valve seat 12 also has a function as a check valve for allowing the working oil to flow from the oil reservoir chamber 8 into the oil chamber 5.

Next, the operation will be described.

When the piston 3 slides from the normal balance position to the pressure side, the working oil flows into the oil chamber 6 through a path (not shown) as the volume of the oil chamber 5 shrinks. Since it cannot be completely accommodated in the chamber 6, it flows through the damping valve 9 provided in the oil passage 7 into the oil reservoir chamber 8 while generating a damping force. At the same time, the suspension springs A and B bend, and the spring load gradually increases with the stroke of the piston 3 as shown in FIG. Further, at this time, since the suspension spring A is bent, the damping valve 9 is displaced in the oil passage 7 toward the oil reservoir chamber 8 side. Since this displacement expands the volume of the oil passage 7 on the oil chamber 5 side, the flow rate of the oil flowing from the oil chamber 5 into the oil reservoir chamber 8 through the damping valve 9 is reduced by the volume expansion amount from the intrusion volume of the inner tube 2. Since the flow rate of the damping valve 9 is small despite the contraction of the oil chamber 5, the damping force generated is also small.

However, as the piston 3 slides, the inner tube 2
When the penetrating deep into the outer tube 1, the contraction of the suspension spring A reaches its limit. After that, since the damping valve 9 cannot be further displaced toward the oil reservoir 8 side, it is displaced together with the piston 3 to the compression side while bending only the suspension spring B. Therefore, the spring load is regulated by the suspension spring B having a large maximum spring load as shown in FIG.
Since the entire amount of the hydraulic oil corresponding to the invasion volume of P flows into the oil reservoir chamber 8 through the damping valve 9, the damping force also increases. This increase in damping force is caused by various sliding speeds V ₁ of the piston 3 as shown in FIG.
Appears uniformly with respect to V ₃ with the bending limit of the suspension spring A as a boundary. In this way, a large damping force is obtained in the latter half of the stroke, and the spring load also increases sharply, so the weight of the shock absorber increases and the piston 3 bottoms against impact or braking even when the balance position is biased toward the contraction side. There is no fear of causing damage.

On the other hand, when the piston 3 turns to the extension side operation, the working oil in the oil sump chamber 7 flows back to the oil chamber 5 from a check valve (not shown), and the suspension springs A and B extend to return the damping valve 9 to its original position. .

As shown in FIG. 5, in the shock absorber in which the seat pipe 1A is erected inside the outer tube 1 and the inner tube 2 is inserted between them, the end of the suspension spring B is connected to the seat pipe 1A. You only need to support it at the upper end.

FIG. 6 shows another embodiment in which the present invention is applied to a shock absorber provided with a solid piston rod 16. Here, a piston 17 which is configured to be slidable with respect to both the cylinder 18 and the piston rod 16 is shown. A damping valve (not shown) is provided in the inside of the cylinder to allow the hydraulic oil on the extension and compression sides to pass therethrough. Piston 17 is piston rod 16
It is sandwiched by a spring A having a small maximum spring load on one side and a spring B having a large maximum spring load on the cylinder 18 side. The oil chamber 6 is located above the piston 17 and the oil chamber 5 is located below the piston 17.
Is formed, and the oil chamber 5 communicates with a hydraulic oil tank 19 provided outside the cylinder 18. In this case, the piston 17 is displaced relatively to the oil chamber 6 side with respect to the piston rod 16 in the first half of the stroke at the time of pressure side operation, and the sliding speed of the piston 17 is lower than the intrusion speed of the piston rod 16 so that the damping valve When the spring A is bent to the limit, the speeds of the springs A and B become equal and the flow rate of the damping valve increases, so that the damping force increases. Further, when the piston rod 16 is displaced during the extension side operation, the spring B having the largest maximum spring load first stretches, so that the piston 17 slides integrally with the piston rod 16, but the spring load drops below a certain level. After that, since the spring A begins to expand, the piston 17 is relatively displaced with respect to the piston rod 16 toward the oil chamber 5 side, and the amount of outflow from the oil chamber 6 is reduced. Therefore, as shown in FIG. 7, the damping force on both sides of compression and compression changes depending on the stroke position regardless of the speeds V _{1 to} V ₃ of the piston 3.

(Effect of the Invention) As described above, according to the present invention, since the damping force in the latter half of the stroke is increased compared to the first half of the stroke, the load of the shock absorber increases and the balance position changes to the contraction side. It resists sliding with a large damping force and absorbs shock in a short stroke range. Therefore, the piston does not bottom out due to impact or braking even under the action of centrifugal force during cornering or when the loaded weight increases, so that good grounding and steering stability are maintained, Improves comfort and safety.

[Brief description of drawings]

FIG. 1 is a sectional view of a hydraulic shock absorber for a motorcycle showing an embodiment of the present invention, FIG. 2 is a graph showing a flow rate characteristic of a damping valve in the same example, and FIG. 3 is a graph showing a spring characteristic of the shock absorber. FIG. 4 is a graph showing damping force characteristics, FIG. 5 and FIG. 6 are cross-sectional views of a hydraulic shock absorber for a motorcycle showing another embodiment, and FIG. 7 is damping of the shock absorber of FIG. It is a graph which shows force characteristics. Further, FIG. 8 is a sectional view of a conventional hydraulic shock absorber for a motorcycle. 1 ... Outer tube, 2 ... Inner tube, 3
...... Piston, 7 ...... oil passage, 9 ...... damping valve, A, B ......
Suspension spring.

Claims (1)

[Claims] 1. A hydraulic pressure in which a piston member is slidably inserted inside a cylinder member, and a damping valve for resisting oil passage is interposed in a hydraulic oil passage through which hydraulic oil flows as the piston member slides. In the shock absorber, the damping valve is configured to be displaceable with respect to the hydraulic oil passage, and the damping valve is supported by the spring A supported by the piston member and having a small maximum spring load, and by the cylinder member opposite thereto. It is sandwiched between a spring B having a large maximum spring load, the spring A is closely contacted in the axial direction of the spring during the compression stroke of the piston member, and the spring A and the damping valve are arranged to be displaced to the compression side. Characteristic hydraulic shock absorber.