JPS634052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in hydraulic shock absorbers for vehicles and the like.

(Prior art and its problems to be solved) Generally, a shock absorber that does not have a free piston at the interface between an air layer 1A and an oil layer 1B sealed inside a cylinder 2 as shown in FIG. 3, aeration (cavitation) occurs due to the reasons described below, which disturbs the damping force characteristics and produces a swishing sound.

In the figure, reference numeral 4 designates a piston rod, and a bracket 5 at the tip of this rod is fixed to the axle side, and a cylinder tip bracket 6 on the opposite side is fixed to the vehicle body, so that the piston rod is used in an inverted state.

In other words, the conventional piston part valve is
It is configured as shown in the figure.

A port 7 is formed through the piston 3, and an annular leaf valve 8 opens and closes this port 7.

An orifice 10 is formed in a part of the annular seat portion 9 formed on the piston 3, and hydraulic oil flows through this orifice 10 until the leaf valve 8 opens, thereby damping the piston in the low speed range. generate force.

Therefore, in this conventional piston valve, the hydraulic oil that has passed through the port 7, especially when it is extended (the inside of the leaf valve 8 is bent), reaches the stepped hole 11, which suddenly expands.
At this point, large turbulence is caused in the flow, which tends to cause cavitation, which causes many air bubbles to exist in the hydraulic fluid.

As a result, fluctuations in the damping force characteristics and swishing noise are observed due to the generation of air bubbles as described above.In addition, a band 12 made of synthetic resin or the like is fitted into the outer peripheral groove of the piston 3 for the purpose of reducing friction. band 12 due to temperature changes in the hydraulic oil.
In a device that expands or contracts and adjusts the clearance with the inner circumference of the cylinder to perform temperature compensation to obtain stable damping force characteristics, using a band 12 with a large required expansion coefficient will cause sliding problems. It also has the disadvantage that it is prone to wear due to heat and that sufficient temperature compensation function cannot be obtained over a long period of time, making it impossible to stabilize the damping force characteristics.

In response, the applicant has devised a piston structure as shown in FIG.

To explain this, 3 is a piston, 4 is a piston rod, 7 is a piston port, 8 is an annular leaf valve as a damping valve, 11 is a stepped hole concentric with the piston 3, and these are basically the parts shown in Fig. 2. It is the same as the thing.

However, in this piston part structure, an orifice passage 20 is formed in the piston 3 by penetrating it in the axial direction, and the end 20A of this passage 20, which is on the downstream side when the piston is operated on the extension side, is inserted into the stepped hole 11. It is opened along the wall.

In other words, the axis of the passage end 20A is coaxial with the piston 3, and the passage is bored so that the inner wall surface of the stepped hole 11 and the inner wall of the passage 20 almost exactly coincide with each other.

As a result, in the expansion side operating region where the piston speed is not so high, the axial jet jet flow passing through the orifice passage 20 flows out as a laminar flow along the inner wall of the stepped hole 11.

Generally, in laminar flow along a cylinder wall, bubbles in the fluid are pulled against the wall surface due to strong viscous resistance, making it difficult to form bubbles.

Therefore, when the flow of oil from the orifice passage 20 is made into a laminar flow, air bubble separation (cavitation) is less likely to occur, and disturbances in the attenuation waveform can be reliably suppressed. At the same time, this also reduces the swishing noise to some extent.

However, with this piston structure, laminar flow cannot necessarily be obtained in the piston speed range after the leaf valve 8 opens, so there is still room for further improvement in terms of performance in the high speed range. It was hot.

Therefore, the present invention can reliably prevent the occurrence of cavitation in the piston part especially during extension, and can sufficiently suppress the occurrence of swishing noise.
Another object of the present invention is to provide a piston structure in a hydraulic shock absorber that can stabilize damping force characteristics.

(Means for Solving the Problems) In order to achieve the above object, first of all, as a first invention, an oil chamber is formed mutually defined through a piston housed in a cylinder, and as the piston moves, In a hydraulic shock absorber that imparts resistance to the flow of hydraulic oil through an orifice or damping valve provided in a piston, the hydraulic oil flows after passing through the orifice or damping valve so as to follow the inner wall of the piston. A piston part structure in a hydraulic shock absorber is provided with a means for regulating the axial flow and a means for converting the axial flow into a radial flow along the end surface of the piston.

In addition, as a second invention, oil chambers separated from each other are formed through a piston housed in a cylinder, and as the piston moves, the flow of hydraulic oil is resisted through an orifice or a damping valve provided on the piston. In the hydraulic shock absorber, a means for regulating the flow of hydraulic oil after passing through the orifice or the damping valve so as to follow the inner wall of the piston, and a means for regulating the flow of hydraulic oil along the inner wall of the piston, and a means for regulating the flow of hydraulic oil along the inner wall of the piston along the end face of the piston. A piston part structure in a hydraulic shock absorber is provided with a temperature compensating means that is disposed between the oil pressure absorber and the oil pressure absorber and expands and contracts the flow path between the oil pressure absorber and the oil pressure absorber.

(Function) In the first invention, the flow of the hydraulic oil that has passed through the orifice or the damping valve becomes a laminar flow along the inner wall of the piston, so that aeration is prevented, but furthermore, the flow is converted to a radial flow. Since the flow is diffused, part of the energy of the flow is consumed, and as a result, even in the high-speed operation range where the flow velocity of the hydraulic oil is high, the occurrence of swishing noise is suppressed, and the aeration prevention effect is more reliable. Become something.

Furthermore, according to the second aspect of the invention, in addition to the above-described effects, the damping force characteristics are compensated for changes in the temperature of the hydraulic oil, so that aeration is prevented and more stable damping force characteristics are obtained.

(Example) Hereinafter, an example of the above-mentioned present invention will be described based on the drawings.

First, the embodiment shown in FIG. 4 will be described as corresponding to the first aspect of the invention. In the figure, substantially the same parts as in FIG. 3 and the like are designated by the same reference numerals.

In FIG. 4, 3 is a piston, 4 is a piston rod, 7 is a piston port, 8 is an annular leaf valve as a damping valve, and 11 is a stepped hole concentric with the piston 3.

In this embodiment, a guide cap 24 having two diameter portions 25A, 25B and a flange portion 23 is inserted into the stepped hole 11, and is fastened to the piston 3 with a piston nut 27.

The guide cap 24 is connected to the orifice passage 2.
The small diameter portion 25A is formed to guide the flow from the port 7 to the gap between the stepped hole 11 and the guide cap 24 for the flow through the port 7.
The small-diameter portion 25 of the guide cap 24 is
The flow is laminar along the inner wall surface of A.

This guide cap 24 bends and diffuses the jet jet in the axial direction in the radial direction of the piston 3 to absorb energy, reduce the swiss noise, and at the same time turn the flow into a laminar flow again along the inner wall surface of the cylinder 2. to prevent aeration.

Note that the guide plate 29 is formed using an inclined piece with a hole 28 punched out, leaving only a part. Therefore,
In this embodiment, since the region after the leaf valve 8 is opened is also laminarized, it is possible to achieve a higher cavitation (aeration) prevention function, and for example, as shown in FIG. 9, the attenuation waveform can be corrected so that it is symmetrical on the extension and compression sides.

Further, the swiss noise is suppressed by absorbing energy by diffusing the jet flow after the orifice flows out into the flow in the radial direction of the piston by the flange portion 23.

In this case, as in the embodiment shown in FIG.
If a guide cap 30 is provided to allow the oil flowing out from the port 28 to flow along the inner wall of the small diameter portion 25A, and then to be diffused and divided in the radial direction by the flange portion 31, even better countermeasures against swish noise can be achieved. can be achieved.

However, in this example, the guide plate 29 is unnecessary.
The embodiment shown in FIG. 6 has the same structure as the embodiment shown in FIG. 4, but the structure of the applied piston valve is different.

In this case, the leaf valve 8' is seated on the seat part 9 via the disk 34 pressed by the spring 33, and the leaf valve 8' is bent inward during the expansion side operation.
When operating on the compression side, the spring 33 is compressed to the left in the figure and fully opened.

Next, the embodiment shown in FIG. 7 corresponds to the second invention, in which a temperature compensating ring 35 made of synthetic resin, aluminum, etc. is installed in the annular groove 35 formed on the inner surface of the stepped hole 11 of the piston 3. A flow path (not shown) whose opening area changes depending on the temperature is formed in the annular passage formed between the outer periphery of the small diameter portion 25A of the guide cap 24 and the inner wall of the stepped hole 11.

The temperature compensation ring 36 has a notch formed in a part thereof, and this notch corresponds to the above-mentioned flow path.

As the oil temperature increases, the viscous force decreases and the damping force weakens, but by narrowing the flow path with the temperature compensation ring 36, this damping force can be corrected as shown in FIG.

In this case, unlike the conventional installation on the sliding surface of the piston's outer periphery, there is no fear of wear or the like, so a stable temperature compensation function can be obtained over a long period of time, and the material of the temperature compensation ring 36 can be freely selected. You can choose the best one depending on the conditions.

Furthermore, in the embodiment of FIG. 8, the stepped hole 36'
A ring 36' is inserted directly into the inner periphery of the ring 36', and is held in contact with the piston 3 and the guide cap 24, respectively, by the legs 38A and 38B formed at the shaft end, and the annular annular groove 35 shown in FIG. It has been omitted. In the figure, numeral 39 is a piston band which functions only as a sliding member.

(Effects of the Invention) As described above, according to the present invention, first, in the first invention, the orifice flow of hydraulic oil is made to flow along the inner wall of the piston, that is, the hydraulic oil flow is made laminar, and By converting this axial flow into a radial flow along the piston end face and absorbing the energy of the flow, it is possible to realize laminar flow of the hydraulic oil over a wider area, that is, to Whether the speed is low or high,
Aeration can be suppressed, more stable damping force characteristics can be obtained, and swiss noise can be eliminated, and driving noise can be reduced.

In the second invention, in addition to the constituent elements of the first invention, a temperature compensating means that expands and contracts depending on the oil temperature between the regulating means and the inner wall of the piston is added. In addition to this effect, a temperature compensation effect can be obtained, and since this temperature compensation means is mounted inside the piston, it does not wear out due to sliding of the piston (no need to replace it) and is thermally stable. Since a stable temperature compensation function can be obtained over a long period of time, more stable damping force characteristics can be obtained.

[Brief explanation of the drawing]

Figure 1 is an overall sectional view of a normal inverted hydraulic shock absorber, Figure 2 is an enlarged sectional view of a conventional piston structure,
FIG. 3 is an enlarged sectional view showing another prior art example of the piston structure. 4 to 8 are enlarged cross-sectional views of the piston portion showing embodiments of the present invention, FIG. 9 is an explanatory diagram showing improved damping force characteristics, and FIG. FIG. 6 is an explanatory diagram in the case of correction. 2...Cylinder, 3...Piston, 4...Piston rod, 7...Piston port, 8...Leaf valve, 11
...Stepped hole, 20... Orifice passage, 23... Flange section, 24... Guide cap, 25A, 25B...
Diameter portion, 28...Port, 30...Second guide cap, 36...Temperature compensation ring.

Claims (1)

[Claims] 1. Oil chambers separated from each other are formed through a piston housed in a cylinder, and as the piston moves, the flow of hydraulic oil is resisted through an orifice or damping valve provided on the piston. In the hydraulic shock absorber, there is provided a means for regulating the flow of hydraulic oil after passing through the orifice or the damping valve so that it follows the inner wall of the piston, and a means for regulating the flow of hydraulic oil so that it follows the inner wall of the piston, and a means for regulating the flow of hydraulic oil so that it follows the inner wall of the piston. A piston part structure in a hydraulic shock absorber, characterized in that it is provided with means for converting the flow into a directional flow. 2. A piston portion structure in a hydraulic shock absorber according to claim 1, wherein the converting means is a guide cap having a flange portion for radially guiding the axial flow along the inner wall of the piston. 3. The hydraulic shock absorber according to claim 1, wherein the conversion means is two guide caps arranged in a double cylindrical shape and having a flange portion that guides the axial flow along the inner wall of the piston in the radial direction. Piston part structure. 4. A piston portion structure in a hydraulic shock absorber according to claim 1, wherein the converting means is a guide cap provided with a skirt portion having a smaller diameter than the piston outer diameter for directing the axial flow of the piston end surface along the cylinder inner wall. 5 Oil chambers separated from each other are formed through a piston housed in a cylinder, and as the piston moves, resistance is imparted to the flow of hydraulic oil through an orifice provided with the piston or a damping valve. In the hydraulic shock absorber, means for regulating the flow after passing through the orifice or damping valve so as to follow the inner wall of the piston, means for similarly converting this axial flow into a radial flow along the end face of the piston, and the above-mentioned regulation. interposed between the means and the inner wall of the piston,
A piston part structure in a hydraulic shock absorber, characterized in that a temperature compensating means for expanding and contracting a flow path between these parts according to oil temperature is provided. 6. The piston portion structure in a hydraulic shock absorber according to claim 5, wherein the upper air temperature compensating means is a temperature compensating ring disposed circumferentially between the inner wall of the piston and the guide cap.