JPS6159410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic shock absorber for preventing nose-down during braking in a motorcycle or the like.

In hydraulic shock absorbers, there is a problem that the buffering characteristics change when air gets mixed in with the hydraulic oil.In normal cases, the air chamber is provided at the top of the oil chamber, so the oil changes as the inner tube expands and contracts with respect to the outer tube. When the surface is suddenly displaced, it is inevitable that some of the air will be drawn into the hydraulic fluid, resulting in so-called aeration.

Therefore, the present applicant formed an oil chamber having an air chamber separated by a free piston in order to compensate for the inflow and outflow of hydraulic oil corresponding to the intrusion volume of the inner tube, separately from the air chamber in the upper part of the inner tube. A hydraulic shock absorber has been proposed that prevents aeration by suppressing the above-mentioned main air oil level fluctuation as much as possible.

Furthermore, when this shock absorber is used as a front fork of a two-wheeled vehicle, in order to prevent the nose from going down during braking, it is designed to cut off communication with the new oil chamber during braking and enhance its action as an air spring. , as shown in FIG. To explain this now, the inner tube 2 is slidably inserted into the outer tube 1, and the piston 3 attached to the insertion end of the inner tube 2 moves around the outer periphery of the hollow rod 4 vertically installed in the center of the outer tube 1. sliding into contact with. A fixed piston 5 with an expanded diameter is formed at the tip of the hollow rod 4.
An oil chamber A is defined between the outer tube 1 and the hollow rod 4, and an oil chamber B is defined between the pistons 3 and 5, the inner tube 2, and the hollow rod 4. Oil chamber C inside the hollow rod 4 and in the upper part of the inner tube 2 communicating therewith
is bounded by the first air chamber 6 above it and the oil level.

The oil chamber A and the oil chamber C selectively communicate with each other via an orifice 7 provided in a hollow rod 4 and a base valve (check valve) 8 fitted at the base end of the hollow rod.

The oil chamber B communicates with the oil chamber A through a check valve and an orifice (both not shown) installed inside the piston 3, and an inner tube 2
When operating on the pressure side where the oil enters, the check valve opens and sucks hydraulic oil from oil chamber A into oil chamber B, and conversely, during operation on the rebound side, hydraulic oil from oil chamber B is sucked into oil chamber A only through the orifice. At this time, a predetermined damping force is generated.

In order to release the hydraulic oil corresponding to the volume entered into the inner tube 2 during the pressure side operation, an auxiliary cylinder 9 is provided outside the outer tube 1, and the oil is passed through the oil chamber D and the passage 11 separated by the free piston 10. A is connected.

The free piston 10 is displaced so that the second air chamber 12, which is partitioned by the free piston 10 to face the oil chamber A, is maintained at the same pressure as the first air chamber 6.

When the total effective volume of oil chambers A and B decreases during the pressure side operation, some of the hydraulic oil flows into oil chamber C through orifice 7, while the rest flows through passage 1 and pushes up free piston 10. It flows into room D.

However, at this time, pressure is applied to the check valve 8 on the valve closing side, so it remains closed.

Since the flow into the oil chamber C is regulated by the orifice 7 (therefore, from this point, the pressures in the first and second air chambers 6 and 12 will temporarily differ). There will definitely be a large influx of escapes.

Then, when operating toward the extension side, the total volume of oil chambers A and B increases, and the pressure decreases (tries to become negative pressure) according to the piston movement speed.
The hydraulic oil then flows into the oil chamber A from the oil chamber D, and depending on the degree of pressure drop, the hydraulic oil in the oil chamber C also flows from the orifice and check valve 8 at the same time.

In this way, during the expansion side operation, the volume compensation amount of the hydraulic oil of the inner tube 2 flows in, but the oil chamber D that supplies the main flow is the free piston 1.
Since the first air chamber 6 is separated from the air chamber 12 by 0, no air is mixed in this backflow hydraulic oil, and the first air chamber 6 is separated from the oil chamber C by the oil surface. As mentioned above, the flow of hydraulic oil is regulated by the orifice 7, so there are very few fluctuations in the oil level.As a result, the hydraulic oil in the oil chambers A and B has air in the first air chamber 6. It is almost impossible for the particles to become mixed in as microbubbles, and fluctuations in the damping characteristics due to so-called aeration are prevented.

By the way, during braking, a force acting on the pressure side is generated on the front fork, causing a nose-down (sinking) phenomenon, but this is countered by the suspension spring and the air compressor sealed in the first and second air chambers 6, 12. It is air pressure.

The repulsive force due to air pressure increases as the volume of the air 6, 12 decreases, and conversely, as the volume increases, the repulsive force decreases because the absorbency is better.

Therefore, in order to prevent nose down, oil chamber A
A relief valve 20 whose relief setting pressure variably increases or decreases depending on the braking state is provided in the passage 11 communicating with and D.
is interposed.

The relief valve 20 allows hydraulic oil to flow only in the direction from the oil chamber A to the D. An annular valve body 23 is arranged around the outer periphery of a cylindrical valve seat body 22 fixed to the passage 11, and a relief spring 24 The valve is pressed onto the valve seat body 22 to close the valve.

In order to adjust the set load of the relief spring 24, the push rod 26 locks the spring receiver 25.
is slidably housed in the cylinder 27, and the pressure of the brake oil, which increases with the braking operation, is transmitted to the end pressure chamber 28 via the pipe 29.

Therefore, during braking, the brake oil pressure acting on the end face pressure chamber 28 of the push rod 26 increases as the brake is applied, causing the push rod 26 to protrude against the return spring 30 and the like.

Therefore, the set load of the spring 24 of the relief valve 20 increases in proportion to the displacement of the push rod 26, and even if the pressure in the oil chamber A increases as the nose down due to braking, the relief valve 20 closes. Leave it alone.

Therefore, the hydraulic oil in the oil chamber A flows into the oil chamber C through the orifice 7 and compresses the small volume of air in the first air chamber 6. This compression pressure acts as a so-called air spring to suppress nose down.

Next, when the pressure in the oil chamber A rises in response to a push-up from the road surface during braking or the compression speed increases, and the pressure in the oil chamber A exceeds the set pressure of the relief valve 20, the valve body 23 is pushed open against the spring 24, causing a portion of the hydraulic oil to flow from the oil chamber A into the oil chamber D.

Therefore, the air in the second air chamber 12 is also compressed via the free piston 10, and in this way both air chambers 6 and 12 simultaneously begin to act as an air spring.

Therefore, the pressure absorption action increases by that amount, and the compression stroke becomes larger, so that the impact during braking can be sufficiently absorbed and alleviated.
Further, since the set pressure of the relief valve 20 increases almost in proportion to the braking force, there is no need to push up the pressure to produce a relief effect during sudden braking.

In this manner, the relief valve 20 operates with an appropriate pressure depending on the braking action, so that nose-down can be effectively prevented, and at the same time, maneuverability against bumping up during braking can be improved.

By the way, except during braking, the push rod 26 is pushed back by the return spring 30, etc.
The spring 24 of the relief valve 20 maintains the relief set pressure at the lowest value.

Therefore, if the pressure side is operated in this state, the relief valve 20 will open due to the pressure in the oil chamber A, allowing oil to flow into the oil chamber D, and this excess oil will also be used to check the check valve 21 during the next rebound side operation. It opens and returns from oil chamber D to A, preventing aeration as usual.

However, when the relief valve 20 is pushed open in this way to allow hydraulic oil to flow in during pressure side operation during normal driving, a certain amount of resistance will occur even if the relief setting pressure is at the lowest value, so strictly speaking, the relief valve 20 Until the valve 20 starts to open, the damping force, which is equivalent to no oil pressure D, increases accordingly.

The higher the damping force during low-speed compression, the worse the riding comfort will be.In contrast, if the characteristics of the relief valve 20 are set taking normal riding comfort into consideration, the relief valve 20 will open faster during braking. A problem arose in that the prescribed nose-down prevention could not be achieved.

The present invention was proposed to solve this problem, and includes an orifice that communicates with the second oil chamber, and the orifice is closed during braking, so that the orifice is closed during normal driving other than during braking. The object of the present invention is to provide a hydraulic shock absorber that improves riding comfort by keeping the damping force low, and that also reliably prevents nose-down during braking.

The present invention will be explained below based on the drawings.

Embodiments of the present invention are shown in FIGS. 2 to 4, and the same parts as in FIG. 1 are designated by the same reference numerals.

Although the mounting direction in FIG. 2 is reversed from that in FIG. 1, there is essentially no difference.

The communication passage 11 that communicates the oil chamber D and the oil chamber A is provided with a relief valve 38 whose relief setting pressure variably increases or decreases depending on the braking state, and a check valve 39 located on the outer periphery of the relief valve 38. be.

The relief valve 38 allows hydraulic oil to flow only in the direction from the oil chamber A to the D. The relief valve 38 is a cylindrical body 41 that is inserted into and fixed to a cylindrical valve seat body 40 that is fixed to the passage 11.
An annular valve body 42 is arranged on the outer periphery of the cylindrical body 41, and a relief spring 43, which is also slidably attached to the outer periphery of the cylindrical body 41, connects the valve seat body 4 via a spring receiver 44.
It is crimped to 0.

In order to adjust the set load of the relief spring 43 to increase during braking, a push rod 47 is coaxially arranged to drive a flanged annular push plate 46 that presses the relief spring 43 via a spring receiver 45.

The push rod 47 is slidably housed in a cylinder 48 and rotates in conjunction with a lever 49 which is interlocked with a brake lever (not shown) via a wire. At this time, a spiral groove 50 is formed on the outer periphery so that the stroke of the push rod 47 is displaced by rotation.
A pin 51 that engages with the cylinder 48 is fixed to the cylinder 48 .

An orifice 52 that short-circuits the oil chamber A and the oil chamber D is passed through the side wall of the cylindrical body 41, and the tip valve part 53 of the push rod 47 is inserted from one end of the cylindrical body 41, and the valve part 53 closes the orifice 52 only during braking. I'm trying to close it. At this time, the push plate 46 is slidably fitted around the outer periphery of the push rod 47 so that the set load of the relief spring 43 increases after the orifice 52 closes during braking, and when the push rod 47 is not braking, the expanded diameter stepped portion 54 of the push rod 47 is fitted. Usually, the relief spring 43 is locked to a flange-shaped stopper 55 provided at the outer peripheral end of the cylindrical body 41.

The check valve 39 is pressed against the annular step 56 of the passage 11 by a spring 57 so as to be in close contact with the valve body 42, and the relief valve 38
Flows hydraulic oil only from oil chamber D to A in the opposite direction to the opening direction.

With the above structure, the push rod 47 is shortened and the orifice 5 is closed except during braking.
2 is open, and the spring 43 of the relief valve 38 maintains the relief set pressure at the minimum value. Therefore, when operating from this state to the pressure side, some of the hydraulic oil in the oil chamber A passes through the orifice 52. Then, the oil flows into the oil chamber D, and the valve body 42 is further bent as shown by the chain line in FIG. 3, and the oil also flows therein.

If the pressure side movement speed of the piston is fast, the valve body 42
After the relief spring 43 is bent more than a predetermined amount, the relief spring 43
begins to contract, and the relief valve 38 is wide open.

For this reason, the compression side damping characteristic under normal conditions is as shown by D in FIG.

In the figure, B shows the characteristic due to only the orifice 52, A shows the characteristic in the range where the valve body 42 bends and opens (works as a so-called leaf valve), and D shows the composite characteristic when these and the relief valve 38 are at the lowest setting value. It is.

Therefore, since the orifice 52 and the valve body 42 are opened in the region where the compression side operating speed is low, the low-speed damping force can be kept small, which helps improve riding comfort.

Next, during braking, the push rod 47 is pushed out to first close the orifice 52, and then the set value of the relief spring 43 is increased from the point beyond the above-mentioned play d in accordance with the braking force.

Therefore, when braking is light enough to simply close the orifice 52, the flow to the oil chamber D is limited to the orifice 52.
Since the relief spring 43 is compressed after the valve body 42 is deflected without passing through the valve body, the damping characteristic as shown by E in FIG. 5 is obtained.

In other words, since the orifice 52 is cut, the resistance to flow into the oil chamber D increases accordingly, increasing the pressure in the oil chamber A and suppressing nose-down during braking.

Due to further braking, the relief spring 43
As the amount of compression increases, the
The opening pressure of the relief valve 38 is increased and the anti-nose down pressure of the oil chamber A is increased, as in the conventional case.

Therefore, according to the present invention, the damping force, especially in the low speed range, can be weakened by the orifice 52 in the pressure side operation when not braking, while the orifice 52 is closed during braking to exhibit a predetermined relief characteristic. This makes it possible to both improve ride comfort in the low-speed operating range and prevent nose-down during braking.

In particular, as the damping force in the low speed range can be determined by the orifice 52, the relief valve 38 can be set to the optimal setting value (for measures against nose down) by considering only the braking time, which is suitable for the applicable vehicle model. Accordingly, an effective nose-down prevention effect can be obtained.

In the above embodiment, the push rod 47 is rotated in conjunction with the brake wire, but it is obvious that the push rod 47 may be moved in the axial direction by brake oil pressure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional device, FIG. 2 is a sectional view of the present invention, and FIG. 3 is a partially enlarged sectional view of a relief valve.
FIG. 4 is an enlarged view of the push rod, and FIG. 5 is a diagram showing the operating characteristics of the present invention. 1... Outer tube, 2... Inner tube, 4... Hollow rod, 6... First air chamber, 7
... Orifice, 10 ... Free piston, 11
... Passage, 12 ... Second air chamber, 38 ... Relief valve, 39 ... Check valve, 42 ... Valve body, 43
... Relief spring, 47 ... Push rod, 50 ... Spiral groove, 52 ... Orifice.

Claims (1)

[Claims] 1. An inner tube is slidably inserted into an outer tube, and a hollow rod that makes sliding contact with the inside of the inner tube is installed in the outer tube, and oil chambers A, B and B are reciprocally expanded and contracted as the inner tube expands and contracts. An oil chamber C is formed which communicates with these and has a first air chamber located at the upper part of the inner tube, while an auxiliary cylinder having a second air chamber is provided at the upper part of the oil chamber D. In this hydraulic shock absorber, a relief valve and an orifice that bypasses the relief valve are interposed in the communication passage between the oil chamber A and the oil chamber B, and the pressure side is connected from the oil chamber A to the oil chamber D. A hydraulic shock absorber characterized in that it is equipped with a push rod linked to a braking means so as to increase the set load of a relief valve that regulates the flow during operation, and to close an orifice during braking.