JPS5926817B2 - Vehicle shock absorber - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in hydraulic shock absorbers for vehicles.

More specifically, a fixed orifice and a main orifice are formed in the check valve so as to communicate with first and second oil passages provided through the piston in the axial direction. A large damping force is obtained under the load, and a fixed orifice and a main orifice are used to reduce the damping force in the piston high speed range.The structure is simplified and manufacturing is simplified by forming both a fixed orifice and a main orifice in the check valve. This invention relates to a vehicular shock absorber with improved buffer performance.

Various types of hydraulic shock absorbers that combine a hydraulic damping device and an elastic member such as a coil spring are used as vehicle shock absorbers. Such a shock absorber consists of a piston that slides inside an inner cylinder, a main orifice and a return oil passage bored in the axial direction of the piston, a check valve that is provided on the top surface of the piston and opens during the compression stroke of the piston, and a check valve that opens during the compression stroke of the piston. A type of shock absorber is proposed that includes a slide valve that is provided on the lower surface of the shock absorber and opens during the tension stroke of the shock absorber.

In such a shock absorber, the tension stroke of the piston is caused by the oil in the upper chamber defined by the piston flowing into the main orifice as the piston rises, and this inflowing hydraulic pressure causing the slide to close the lower opening of the main orifice. The valve is opened against the valve spring, and a predetermined damping force is obtained by controlling the amount of movement of the slide valve and the amount of oil by the main orifice, thereby providing a hydraulic damping effect. In addition to the above, such a buffer has also been adopted, in which a groove is provided in the radial direction at the top open end of the return oil passage, and a fixed orifice is provided in the radial direction between check pulps that block the top open end of the return oil passage. . Hydraulic shock absorbers in general, including the above types, have the following problems.

In other words, in damping operation, if the piston stroke is small in the low piston speed range, at the time of initial damping, and the slope of the damping force curve is set small in the piston low speed range as in the piston high speed range, the undulations and undulations of the road surface will be reduced. etc., the shock absorber does not provide sufficient damping, resulting in a so-called fluffy shock, resulting in poor handling and ground contact. Therefore, if the slope of the damping force characteristic curve is set to be large, the spring will be compressed by the impact of small irregularities, and when it returns to its original state, the expansion speed will be regulated by a large damping force. Therefore, the next impact occurs before the vehicle has sufficiently touched the road surface, making it impossible to effectively dampen small impacts.Contrary to the above, bumps in the road surface are directly transmitted to the occupants, which impairs driving safety and ground contact. In addition to reducing ride comfort, this also increases occupant fatigue, which is unfavorable in terms of vehicle safety. In addition, by increasing the damping force of the piston and keeping it constant, the damping force required in this area in the piston high speed range and large stroke range.
Further, desirable damping force characteristics, ie, buffering performance, cannot be obtained. This is the same for the types with check valves and slide valves mentioned above; the main orifice opens with the slide valve during the tension stroke, and damping force is obtained from this main orifice, but if only this main orifice is used, the steady damping force characteristic However, the same problem as above occurs.

Also, in this type, a fixed orifice is provided in the radial direction of the piston between the check valve and the return oil passage that opens on the top surface of the piston, thereby achieving highly accurate and stable damping force characteristics in the low piston speed range. However, since the orifice is provided perpendicular to the direction in which the hydraulic pressure is applied, the oil flow resistance is large, making it impossible to obtain highly accurate and stable damping force characteristics. In this way, hydraulic shock absorbers for vehicles have different damping force characteristics in low piston speed ranges and small strokes, etc., and damping force characteristics in high piston speed ranges and large strokes, etc., and are designed to meet both requirements. Moreover, a hydraulic shock absorber with preferable damping force characteristics has not yet been proposed.

The present inventors have devised the present invention in view of the above-mentioned problems in vehicle shock absorbers, particularly shock absorbers having plate-shaped check valves and slide valves, in order to effectively solve these problems.

The purpose of the present invention is to set a large damping force in the low piston speed range and to reduce the damping force in the high piston speed range, especially in the tension stroke, and to set the damping force in the low and high piston speed ranges. The rate of increase in damping force is increased exponentially in the low-speed range after reaching the halfway point of the predetermined piston speed, and the rate of increase in damping force after the halfway point is decreased. By increasing the speed exponentially, we eliminate the loose feeling of the buffering operation in the low speed range of the piston, such as when a small impact occurs and a small stroke, improving steering stability and ground contact, and improving ride comfort as a whole. We provide shock absorbers for vehicles.

Moreover, as described above, there is provided a shock absorber for a vehicle that is capable of obtaining desirable damping force characteristics in a low piston speed range, but also in a high piston speed range and a large stroke range. I will provide a.

Particularly, it is an object of the present invention that the first and second oil passages provided in the piston are opened and closed by plate-shaped check valves and slide valves arranged on the upper and lower surfaces of the piston, and the check valve A fixed orifice communicating with the first and second oil passages and a main orifice are formed together, and the damping force is set large by the fixed orifice in the low speed range and small stroke of the piston during the piston tension stroke, and the damping force of the piston is increased. To provide a shock absorber for a vehicle in which a main orifice opens a slide valve to allow oil to flow through a second oil passage in a high speed range and a large stroke, and reduces damping force by the main orifice as well as a fixed orifice.

The present invention has a simple structure and easy processing by forming both the fixed orifice and the main orifice that control the damping force into a plate-shaped check valve as described above.
To provide a shock absorber for a vehicle that can be manufactured simply, can improve accuracy, can improve reliability of damping operation, and can reliably set the damping operation to an intended value.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 1 shows a side sectional view of the shock absorber, and although it is shown horizontally in the figure, this is because the shock absorber is long in the axial direction, and in reality it is installed in the vehicle with the left side facing up and the right side facing down. 2 shows an exploded perspective view of the piston portion, and FIG. 3 shows a sectional view taken along line 3-3 in FIG. 1.

The shock absorber 1 is composed of inner and outer double cylinder bodies 2 and 3, with an inner cylinder 2
The upper end of and the upper part of the outer cylinder 3 are closed with a rod guide 4,
The upper end of the outer cylinder is closed with a cover plate 5, and the cover plate 5 and the rod guide 4 are closed.
A rubber seal member 6 is interposed therebetween, and seals between the rod guide 4 of the rod 9 fitted slidably in the axial direction of the inner cylinder 2 and the cover plate 5.

The bottoms of the inner and outer cylinders 2 and 3 are closed with a bottom member 7, and a reservoir chamber S is formed between the inner and outer cylinders 2 and 3, and an oil chamber S2 is formed within the inner cylinder 2. The chambers S1 and S2 communicate with each other through a bottom valve 30, which will be described later. The upper part of the rod 9 extends outside the cover plate 5, and the upper end of the rod 9 is attached to the body side of the vehicle.A bracket 8 is integrally extended in the axial direction at the bottom of the bottom member 7, and this can be attached to a motorcycle or a motorcycle. It is pivoted to the rear wheel axle, etc. A piston block 10 is provided at the lower end of the rod 9 facing into the inner cylinder 2. Specifically, a small diameter mounting portion 9a is provided at the tip of the rod 9, and a valve stopper 1 that also serves as a spring receiver is provided on the tip of the rod 9.
1, then the piston 12, and then the nut 13.
are sequentially fitted and screwed together, and a stopper 11, a piston 12, and a nut 13 are fixed to the rod attachment portion 9a in this order from above, and 14 is a piston ring fitted around the outer periphery of the piston 12. With this piston 12, the chamber S2 in the inner cylinder 2 is the upper chamber S.
It is divided into a lower chamber S4 and a lower chamber S4. A plurality of return oil passages 15, which are first oil passages that penetrate the piston 12 in the axial direction and open on the upper and lower surfaces of the piston, are formed.

As is clear from FIG. 2, the return oil passage 15 has an arcuate and elongated hole shape. A second oil passage 16 is provided in the piston 12 located inside the return oil passage 15, and a plurality of these oil passages 16 are provided. - also penetrates the piston 12 in the axial direction and opens on the top and bottom surfaces of the piston. A second oil passage 16 is provided on the lower surface of the piston 12.
......A ring-shaped slide valve 19 that closes only the lower end opening is fitted so as to be able to slide along the guide portion 13a of the nut 13, and the lower surface of this valve 19 and the nut 13 are connected. A valve spring 20 is compressed between them, and the valve 19 elastically closes the lower end opening of the oil passage 16 due to this spring force. A check valve 21 for opening and closing the return oil passage 15 is disposed on the upper surface of the piston 12 so as to be slidable on the stopper 11, and as is clear from FIG. 2, the check valve 21 is formed of a plate material into a ring shape.

The check valve 21 is connected to the return oil passage 1 outside the oil passage 16.
The valve 21 is formed to have a diameter that can close the valve 5, and is opened by hydraulic pressure acting through the return oil passage 15 during the compression stroke of the piston 12. Check valve 21 and stopper 1
A valve spring 23 is disposed between the valve 21 and the valve 21, and the spring 23 is formed of a ring-shaped plate spring with a V-shaped side surface as shown in FIG. Elastic contact with the top surface of the piston, return oil path 1
Close 5. A fixed orifice 24 penetrating in the axial direction is formed in the above-described plate-shaped check valve 21, and this orifice 24 is preferably a circular hole as shown in the figure.In the illustrated example, one such orifice is provided, but two or more may be provided. In order to obtain the damping force characteristics described later, the piston diameter, cross-sectional area of the orifice, etc. may be determined as appropriate.

This fixed orifice 24 is provided on the same circumference as the upper end opening of the return oil passage 15 that is closed by the check valve 21,
The fixed orifice 24 communicates with a return oil passage 15, which is a first oil passage. Further, a main orifice 25 is formed to pass through the check valve 21 in the axial direction, and the main orifice 25 is also a circular hole, and a plurality of main orifices, three in the illustrated example, are provided. The main orifice 25 is located inside the fixed orifice 24 and on the same inner periphery as the second oil passage 16, so that the main orifice 25 and the second oil passage 16 communicate with each other. In this way, the plate-shaped check valve 21
By providing the fixed orifice 24 and the main orifice 25 in the main orifice 24, the holes 24 and 25 can be easily machined and the dimensional accuracy can be set extremely well.

Furthermore, by providing the main orifice 25 in the check valve 21, the cross-sectional area of the oil passage 16 that opens the slide valve 19 during the piston pulling stroke can be arbitrarily set. That is, the main orifice 25 has a function of setting the damping force range in a low piston speed range due to the fixed orifice 24. In other words, the opening timing of the slide valve 19 is set by setting the orifice effect of the main orifice 25. A bottom valve 30 is provided at the bottom of the inner cylinder 2,
The bottom valve body 31 is located on the bottom member 7 and partitions the inner and outer cylinders 2 and 3, and a communication passage 32 that communicates the inner and outer cylinders 2 and 3 is formed at the bottom and a part of the radial direction of the body 31. has been done.

At the center of the body 31 is a fixed orifice 33 that connects the lower chamber S4 of the piston 12 and the communication passage 32, and on the outer periphery of this orifice, an annular protrusion 31a is formed.
A plurality of passages 34 are provided in a radial manner so as to connect the lower chamber S4 and the communication passage 32. A ring-shaped check valve 35 made of a plate material is disposed on the annular protrusion 31a, and between the ring-shaped clip 37 and the check valve 35 is the naeck valve spring 2.
Similarly to 3, a leaf spring-like spring 36 which is ring-shaped and bent into a V-shape on the side is intervened, and the naeck valve 35 is connected to the passage 34 by the spring 36.
The upper opening of the is closed. In addition, 40 in the drawing is piston 1
This is the second buffer spring.

Next, to explain its operation in detail, the compression stroke is similar to this type of shock absorber, and at the beginning of compression, the piston is in the state of the first surface.
2 moves to the right (descends), and the oil in the lower chamber S4 returns to the oil passage 15...
It flows from the fixed orifice 24 of the check valve 21 into the upper chamber S3 through the fixed orifice 24 of the check valve 21, and flows into the reservoir chamber S through the fixed orifice 33 of the bottom valve 30.
1.

When the oil pressure increases as the stroke progresses, check valve 2
1 is lifted against the spring 23, and as a result, the return oil passages 15 are opened to obtain a predetermined damping force in the compression stroke. Next, to explain the tension stroke, the piston low speed region of the tension stroke, that is, the tension load as a reaction to the initial compression load, the tension load of a small stroke, and the buffering effect of road surface irregularities when driving on a general road surface. In the low piston speed range, oil in the upper chamber S3 as the piston moves up flows into the return oil passage 15 through the fixed orifice 24 provided in the check valve 21.

At the beginning of the pulling stroke of the piston 12, the oil flow is first controlled by the flow cross-sectional area of the fixed orifice 24, and therefore, the oil flow is controlled at a speed that is in the low speed range of the piston and before the slide valve 19 is opened. In the load range, the fixed orifice 24 provides a large damping force.

Therefore, when the piston is in a low speed range, a large damping force is used to provide a buffering effect in this region, and the bouncy feeling caused by the buffering motion caused by small bumps in the road surface is prevented. The damping motion with a small stroke and a small load before the release of the damping force is effectively performed without impairing steering stability, ground contact, and ride comfort. In the high speed range and large stroke range of the piston 12, the amount of oil passing through the main orifice 25 increases and the oil pressure in the oil passage 16 increases, and this oil pressure causes the slide valve 19 to act as a spring. Push open against 20,
Main orifice 25, soil/lower chamber S3 via oil passage 16
, S4 are in communication, and the oil in the upper chamber S3 is connected to the main orifice 25.
By controlling the flow cross-sectional area of the main orifice 25 and obtaining the corresponding damping force characteristic as the sum of the cross-sectional area of the fixed orifice 24, the slope of the damping force characteristic curve is compared to the above. It becomes small.

To explain the above using the graph in Figure 4, the graph shows actual measured values used as a rear shock absorber for a motorcycle, with the horizontal axis showing the piston speed (m/sec) and the vertical axis showing the damping force (Kg). It is something.

As is clear from the figure, in the micro-vibration region where the piston speed is within 0.1 m/sec, the damping force is attenuated in this range, that is, in the low piston speed region, due to the action of the fixed orifice 24, as shown by curve C. It increases exponentially as the rate of increase in force increases. This is main orifice 25
However, the damping force range in the piston low speed range due to the fixed orifice 24, that is, the range up to the so-called mid-break point (C in Fig. 5)
This is because it has a function to set. The opening timing of the slide valve 19 is set by setting the orifice effect of the main orifice 25. Piston speed is 0.1m
/second, the main orifice 25 is
The slide valve 19 that closes the main orifice 25 opens, and the rate of increase in the damping force becomes small in the piston speed range after this point due to the action of the main orifice 25. Increases exponentially. In this way, the damping force increases in a squared manner up to the middle point in the low piston speed range, and the damping force is large in response to small vibrations during normal driving and small impact loads due to road surface irregularities that occur in this region. We suppressed the fluffy feeling by using force, and in response to this, we reduced the damping force in the piston high speed range and large stroke range compared to the above, and were able to obtain optimal damping force characteristics in the entire piston speed range. Although the absolute values are shown in the graph, this is to specifically show actual measured values for motorcycles, and although the values may change for four-wheeled vehicles, the preferred damping force characteristics as shown in the curve in the graph can be obtained. According to the present invention as described above, since the check valve that opens and closes the return oil passage is provided with a fixed orifice that communicates with the oil passage, it is possible to set a large damping force in the low speed range of the piston initial movement range, and the check valve Because the main orifice is provided, the damping force in the high piston speed range can be made smaller than in the low piston speed range, and the damping force can be reduced at the mid-point of the predetermined piston speed in each of the low and high piston speed ranges. The rate of increase in damping force in the speed range can be increased exponentially as it becomes larger, and the rate of increase in damping force after passing the midpoint can be increased exponentially as it becomes smaller. Therefore, according to the present invention, it is possible to perform the buffering effect in the low piston speed range such as small shocks and small strokes that occur when driving on general roads in an optimal state, and to achieve a smooth feeling that is excessive in pursuit of ride comfort. It eliminates the buffering action and prevents the direct propagation of minute vibrations generated in pursuit of steering stability and grounding performance to the occupants, rationalizing the contradictory factors of improving riding comfort and improving steering stability and grounding performance. It is possible to improve ride comfort and handling by matching the

Further, according to the present invention, although it is possible to obtain the above-mentioned preferable damping force characteristics in the low piston speed range,
It is possible to obtain desirable damping force characteristics required even in the high piston speed range and large stroke range, and it is possible to obtain a high-performance shock absorber with optimal damping force characteristics for each region in the entire piston speed range. .

Furthermore, according to the present invention, the check valve for opening and closing the first oil passage provided in the piston is simply provided with a fixed orifice communicating with the oil passage and a main orifice communicating with the second oil passage. It is possible to achieve this and implement it without making any major changes to conventional shock absorbers, and as mentioned above, it is possible to provide a shock absorber with extremely good performance with a simple structure and at low cost. For forming, it is sufficient to simply drill holes in a plate-shaped check valve, which is easy and convenient for maintaining high dimensional accuracy.In addition, the oil passage on the piston side can be freely formed without worrying about diameter accuracy. This makes it easier to manufacture the piston, and the main orifice can be machined at the same time as the fixed orifice, making it easier to manufacture and improving accuracy, ensuring reliable operation and reliability of the slide valve. It also facilitates and ensures the setting of low and high midpoints of low piston speed.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a side sectional view of the entire shock absorber, FIG. 2 is an exploded perspective view of the piston block, and FIG. 3 is a sectional view taken along the line 3-3 in FIG. FIG. 4 is a graph showing the damping force characteristics of the shock absorber according to the present invention in the tensile stroke. In the drawings, 1 is a shock absorber, 2 is an inner cylinder, 3 is an outer cylinder, 9 is a rod, 10 is a piston block, 12 is a piston, 15 is a first oil passage, 16 is a second oil passage, and 19 is a slide. valve,
21 is a check valve, 24 is a fixed orifice, and 25 is a main orifice.

Claims (1)

[Claims] 1 Inner and outer cylinders, a piston provided at the tip of the rod and slidably fitted into the inner cylinder, and a first piston provided in the piston.
an oil passage and a second oil passage; a plate-shaped check valve disposed on the upper surface of the piston to close both the first oil passage and the second oil passage; A slide valve arranged on the lower surface of the piston, a fixed orifice formed as a through hole in the check valve, arranged in the axial direction of the first oil passage, and a main orifice arranged in the axial direction of the second oil passage. A vehicle shock absorber consisting of.