JPS6367056B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a hydraulic shock absorber for a vehicle.

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

For this reason, the following problems arose, for example.
In other words, in the hydraulic shock absorber for street vehicles,
Because the road surface has small undulations, the damping force is set relatively low to improve responsiveness. However, when cornering, the vehicle body sinks, and if the damping force is small in this sunken state, handling becomes extremely poor. Therefore, it is required that the damping force of the front fork and rear fork be reduced around 1G (during steady driving), but increased during cornering to improve the ground contact of the vehicle body.

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 applicant first installed a relief valve at the inlet of the tank in a separate tank type hydraulic shock absorber to provide resistance to the hydraulic oil flowing in during pressure side operation. , one end of the spool supporting the spring of this relief valve faces the atmospheric chamber and the other end faces the oil sump chamber, and a means is provided to prevent the spool from moving toward the atmospheric chamber within a certain limit, thereby reducing the pressure in the oil sump chamber. proposed a hydraulic shock absorber in which the relief setting pressure was changed in proportion to (Japanese Patent Application No. 151029/1982).

According to this, the set pressure (valve opening pressure) of the relief valve changes in response to the pressure in the oil reservoir chamber, which changes in proportion to the stroke position of the piston rod, as shown in Figure 1. position-dependent damping force characteristics can be obtained.

That is, Fig. 1 is a characteristic diagram with the vertical axis as damping force A and the horizontal axis as piston speed B, and shows the settings of the relief valve where the throttling resistance curve C due to the preset orifice changes depending on the piston stroke position. When the pressure is reached, the respective relief valves open and a damping force with linear characteristics D ₁ , D ₂ . . . D _X is obtained.

In this way, the absorbed energy can be increased depending on the stroke position, and as a result, ride comfort and steering stability are further improved.

However, in the case of such conventional shock absorbers, when changing the position dependence of the damping force mentioned above, it is necessary to change the pressure in the tank chamber, where the pressure changes uniquely depending on the stroke position, similar to the oil reservoir chamber. This was done by changing the pressure (that is, gas pressure) and the spring constant of the relief spring, or by changing the gas volume in the tank chamber.

Therefore, it takes a lot of effort to make changes and adjustments.
Furthermore, even if the damping force is changed, as can be seen in Figures 2A and B, it is not possible to change the damping force widely depending on the stroke position (because the nonlinearity is weak), and it is difficult to set it optimally depending on the course, running speed, etc. There was a problem.

Therefore, the present invention provides means for switching the tank chamber pressure in a tank chamber at the back of the free piston that separates the oil reservoir chamber in a multi-stage manner depending on the stroke position, using a combined force of gas pressure and spring force, or using a plurality of chambers. The purpose is to solve the above problems by providing the following.

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

In FIG. 3, 1 is a hydraulic cylinder, 2 is a piston rod, and the hydraulic cylinder 1 is defined into an upper chamber A and a lower chamber B by a freely slidable piston 3. 4 is a spring that biases the piston rod 2 toward the expansion side.

The lower chamber B of the hydraulic cylinder 1 is communicated with a tank 7 shown in FIG. 4 through a port 5 opened at the lower end and a communication oil pipe 6.

The inside of the tank 7 is defined by a free piston 8 into a gas chamber 9 and an oil reservoir chamber 10, which will be described later.
The hydraulic oil in the lower chamber B is introduced into the oil reservoir chamber 10 through a relief valve 24, which will be described later, during compression operation.

The relief valve 24 has a spool 13 slidably inserted into the shaft hole 11 of the body 12 attached to the tank 7, with one end of the spool 13 facing the oil reservoir chamber 10 and the other end facing the atmospheric chamber 20. Atmospheric chamber 20
A relief spring 28 is interposed therein to urge the spool 13 toward the oil reservoir chamber 10. The outer diameter of this spool 13 changes into two stages in the middle, and the small diameter part 14 penetrates the valve case 15 fixed to the body 12 and projects into the oil reservoir chamber 10, and the stepped part 18 is inserted into the oil chamber 19. On the other hand, the large diameter portion 16 freely slides through the shaft hole 11 and projects into the atmospheric chamber 20.

The oil reservoir chamber 10 and the oil chamber 19 are always in communication via an orifice 21 provided in the spool 13. A valve plate 26 is attached to the tip of the small diameter portion 14 located in the oil reservoir chamber 10 to prevent it from coming off with a snap spring 25.
is fitted, and this valve plate 26 is attached to the valve case 1.
The spool 13 is prevented from moving any further toward the atmospheric chamber 20 at the position where it touches the end surface of the spool 5 .

The valve case 15 houses a check valve 27 that opens when operating on the compression side. In this embodiment, the valve plate 30 of the check valve 27, which is held by the flange 29 of the valve case 15 when operating on the compression side, is connected to the valve of the relief valve 24. It forms a valve seat for plate 26. Note that 32 is an opening to which the communication oil feed pipe 6 is connected, and communicates with the oil chamber 19 .

On the other hand, the gas chamber 9 is filled with gas that presses the free piston 8 toward the oil reservoir chamber 10 at a predetermined pressure, and the pressing force (tank chamber pressure) is applied in stages (two stages) depending on the stroke position. ) is housed in a spring 34 for switching.

That is, the base end of the spring 34 is supported by the free piston 8, and the tip end is supported by the stopper of the gas inlet when the piston rod 2 is at its most extended position.
The spring receiver 36 provided at 5 is guided by the stopper 35 etc. in a free state with a predetermined interval (play) l.

Therefore, as the amount of oil flowing into the oil reservoir chamber 10 increases in proportion to the stroke position during pressure-side operation, the pressure in the gas chamber 9 (tank chamber pressure) moves toward the left in the figure of the free piston 8. (that is, the pressure in the oil reservoir chamber 10 also increases uniquely), but when the stroke is made to the extent that the above-mentioned interval l is filled,
This time, in addition to the above-mentioned gas pressure, the set pressure of the spring 34 also acts on the free piston 8, so the pressure in the oil reservoir chamber 10 that opposes this increases more rapidly than in the previous proportional characteristic.

Next, the operation will be explained. In a stationary state, the spool 13 is balanced as shown by the following formula.

P ₂ B=(B-A) P ₁ +F However, P ₁ : Pressure in the oil chamber 19 P ₂ : Pressure in the oil reservoir chamber 10 A: Area relative to the diameter of the large diameter portion 16 of the spool B: Area of the valve plate 26 Area relative to the diameter F: Set load of the spring The valve spring 28 is adjusted in advance so that this balance position reaches the rightward movement limit of the spool 13 (the state shown in Fig. 4) when the piston rod 2 is fully extended. Elastic force, valve plate 26 and large diameter part 1
An effective pressure receiving area of 3 is set.

When the piston rod 2 is compressed from this balanced state, the hydraulic oil entering the piston rod 2 flows from the lower chamber B to the oil chamber 19 through the communication oil pipe 6.
flows into. A portion of the hydraulic oil that has flowed into the oil chamber 19 flows into the oil reservoir chamber 10 through the orifice 21.
Therefore, a pressure difference occurs between the pressures P ₁ and P ₂ in both chambers. Due to this differential pressure, the above-mentioned balanced state is disrupted, and the spool 13 moves toward the oil reservoir chamber 10.
The relief valve 24 is opened. This relief valve 24 provides resistance to the hydraulic oil flowing from the oil chamber 19 to the oil reservoir chamber 10, thereby producing an appropriate damping force.

By the way, the pressure _P2 in the oil reservoir chamber 10 changes depending on the amount of oil, that is, the stroke position of the piston rod 2. Therefore, the relief valve 24 is
The set pressure changes in response to the pressure P2 in the oil reservoir chamber 10, which changes in proportion to the stroke position of the piston rod ₂ . In other words, the pressure in the oil reservoir chamber 10 when the piston rod 2 is at a certain stroke position
The differential pressure between P ₂ and spring 28 is spool 1
3, and the higher the pressure P ₂ , the more the spool 1
3 is strongly pushed toward the atmospheric chamber 20 side, and the valve opening pressure (cracking pressure) increases.

In this embodiment, when the further piston rod 2 reaches a certain stroke position, the set pressure of the spring 34 begins to act on the free piston 8 as described above. From this point on, the rate of increase in the tank chamber pressure relative to the stroke that pushes back the piston 8 increases rapidly, and this causes the pressure in the oil reservoir chamber 10 to increase P ₂
The rate of increase in the damping force also changes or increases rapidly, and as a result, the damping force characteristics change significantly depending on the stroke position, as shown in FIGS. 5A and 5B. In other words, by changing the piston pressing force in stages according to the stroke position, the damping force characteristic changes from the conventional linear characteristic to a curved line with non-linearity.

As a result, by selecting the spring setting force of the spring 34, it becomes possible to easily set the position-dependent damping force characteristic optimally depending on the course and traveling speed.

Next, FIGS. 6 to 8 show other embodiments of the present invention.

In Fig. 6, instead of filling the tank chamber 9 at the back of the free piston 8 with gas, two springs 37A and 37B are housed, which have different spring setting pressures and start moving from different strokes. In addition to the low-pressure gas chamber 9 separated by the free piston 8, there is also a high-pressure gas chamber 39 separated by a free piston 38 that responds to the amount of oil flowing into the oil reservoir chamber 10, and this free piston. Further, in FIG. 8, after the free piston 8 that separates the gas chamber 9 has moved a predetermined stroke, the oil reservoir chamber 10 is further closed.
By installing a free piston 41 that moves into the gas chamber 9 against the spring 40 when the amount of oil increases, the pressure in the oil reservoir chamber 10 balanced with the free piston can be adjusted in stages according to the stroke position. This is an example of switching between

With these, the same effects as in the previous embodiment can be obtained.

As explained above, according to the present invention, the tank chamber at the back of the free piston that separates the oil reservoir chamber is provided with means for switching the piston pressing force in multiple stages according to the stroke position. The effect is that the degree of freedom in changing the damping force characteristics according to the stroke position can be greatly expanded.

[Brief explanation of drawings]

1 and 2A and 2B are operational characteristic diagrams of the conventional example. FIGS. 3 and 4 are partially cut-away overall and main part sectional views showing an embodiment of the present invention, and FIGS. 5A and 5B are operational characteristics diagrams thereof. Figures 6 to 8
The figures are sectional views of essential parts showing other embodiments of the present invention. 1... Hydraulic cylinder, 3... Piston, 2...
Piston rod, 7...Tank, 8...Free piston, 10...Oil reservoir chamber, 24...Relief valve, 28...Relief spring, 13...Spool, 20...Atmospheric chamber, 15...Valve case,
26... Valve plate, 9... Gas chamber (tank chamber),
34... Spring, 37A, 37B... Spring, 38... Free piston, 39... High pressure gas chamber, 40... Spring, 41... Free piston.

Claims (1)

[Claims] 1 A hydraulic buffer in which a piston is housed in a cylinder so that it can slide freely, and as the rod connected to the piston expands and contracts, part of the hydraulic oil is guided inside the tank to an oil reservoir chamber separated by a free piston. In the tank, a relief valve is installed at the inlet of the tank to provide resistance to the hydraulic oil flowing in during pressure side operation, and one end of the spool carrying the spring of this relief valve faces the atmospheric chamber and the other end faces the oil reservoir chamber. , and a means is provided to prevent the spool from moving toward the atmospheric chamber to a certain extent, and the relief setting pressure is changed in proportion to the pressure in the oil reservoir chamber, while a means is provided in the tank chamber at the back of the free piston according to the stroke position. 1. A hydraulic shock absorber, characterized in that the hydraulic shock absorber is provided with means for switching the piston pressing force in multiple stages.