JPS6216340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shock absorber whose damping characteristics can be automatically changed in accordance with the loaded weight of a vehicle.

For shock absorbers used in vehicles including two-wheeled vehicles and four-wheeled vehicles, especially vehicles with large body load fluctuations such as light vans and trucks,
A damping force that changes depending on the loading status of the vehicle is required.

For this reason, conventionally, for example, the piston has a port equipped with a damping valve that allows flow only from the upper chamber to the lower chamber, and a sleeve (spool) that changes the effective area of the port according to changes in the relative position of the piston. ), so that the port resistance can be made variable and the damping force on the rebound side when the vehicle is loaded can be increased.There was a shock absorber with a so-called variable rear aperture structure.

However, since such conventional shock absorbers use a single rebound-side damping valve, the pressure itself when the damping valve starts to open does not change even if the loading status of the vehicle changes. The disadvantage is that it is not possible to increase the rate of change in the damping force on the rebound side when the car is empty and when the car is loaded in the slow range (for example, 0.3 m/sec or less), and as a result, the required damping characteristics cannot be fully achieved. It was hot.

Therefore, the upper chamber and the lower chamber are communicated through first and second damping valves, which are arranged in series with the piston and allow flow only from the upper chamber to the lower chamber during the expansion side operation. A side passage that short-circuits the middle of the damping valve and the lower chamber is provided, and a sleeve is provided that opens and closes this side passage depending on the relative positional displacement of the piston. The applicant proposed a shock absorber in which the set load of the damping valve No. 2 was set to a large value (Utility Application 1983-
92555). This shock absorber can exhibit damping characteristics that match the required damping characteristics d by setting the set load of the first damping valve to match the required damping characteristics d when the vehicle is running on the rebound side when the vehicle is empty. Furthermore, by setting the set load of the second damping valve to match the required damping characteristic c during the expansion side operation when loading a vehicle, a large damping characteristic matching the required damping characteristic c can be obtained. However, it is difficult both in terms of space and mechanically to provide a mechanism that can freely set the damping characteristics during contraction side operation in the piston together with the above-mentioned rebound side mechanism. The characteristics are almost the same as in the past, with the port area being changed depending on the loaded weight, and the compression side damping characteristics being switched between when the vehicle is empty and when the vehicle is loaded due to the rear throttling effect created by the port resistance. Therefore, for example, if the compression side damping characteristic when the car is empty is set to match the required damping characteristic b during the contraction side operation when the car is empty as shown in Fig. 1,
There is a problem in that the compression side damping characteristic when the vehicle is loaded is only a', which is much lower than the required damping characteristic a during the compression side operation when the vehicle is loaded, as shown in FIG.

The present invention was proposed in order to solve this problem, and provides a shock absorber in which damping characteristics on the compression side can be freely set when the vehicle is empty and when the vehicle is loaded.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4 of the accompanying drawings.

First, to explain the structure, in the figure, 1 is an outer cylinder, 2 is an inner cylinder, 3 is a base valve, 4 is a reservoir chamber, 5 is a piston, and 6 is a piston rod. The reservoir chamber 4 is divided into a lower chamber 8 and is formed between the inner tube 2 and the outer tube 1.

As shown in FIGS. 3 and 4, the base valve 3 has a base valve case 9 when the shock absorber is operated on the compression side (compression side stroke).
The lower part is supplied through a first damping valve 11 and a second damping valve 12 which are arranged in series inside the cylindrical guide 10 fixed through the lower part chamber 8 and allow flow only from the lower part chamber 8 to the reservoir chamber 4 direction. Transfer the oil from chamber 8 to reservoir chamber 4.
A contraction side passage 13 is provided which flows toward the flow, and a passage 13' between the first and second damping valves 11, 12 is provided.
13 and the lower chamber 8 are connected to the guide 1.
0 and opens into the guide outer circumferential wall 10a. A flanged cylindrical sleeve (spool) 15 opens and closes the side passage 14 according to the relative positional displacement of the piston 5, which varies depending on the loaded weight of the vehicle.
is slidably fitted into the guide outer peripheral wall 10a.

The first damping valve 11 includes an annular valve body 11a that fits into and slides on a stepped cylindrical sub-guide 16, and a valve body 1 of the annular valve body 11a.
Coil spring 11 that biases 1a in the valve closing direction
b, and opens and closes the passage 13 downstream of the side passage 14. The second damping valve 12 includes a spherical valve body 12a and a truncated conical coil spring 12b that biases the valve body 12a in the valve closing direction, and opens and closes a passage upstream of the first damping valve 11. The annular valve body 11a is seated on the valve seat surface 17a of the protrusion 17 on the inner wall of the guide 10, and the spherical valve body 12a is seated on the valve seat surface 18a of the disk 18 fixed to the upper inner wall of the guide 10. Parts of the valve seat surfaces 17a and 18a are cut out to form constant orifices 19 and 20, respectively, to smooth the rising damping characteristics when the piston 5 is in a low speed region (for example, 0.1 m/sec or less). .

In order to open and close the side passage 14, a position detection spring (control spring) 21 that detects the relative position of the piston 5 and drives the sleeve 15 is disposed in the lower chamber 8, and its rear end is connected to the outer step of the sleeve 15. Fix it. Also, a coil spring (return spring) that opposes this position detection spring 21 and urges the sleeve 15 toward the lower chamber 8.
22 is interposed between the lower end of the sleeve 15 and a stopper 23 fixed to the outer peripheral wall of the guide 10. However, the spring constant of the position detection spring 21 is set to be stronger than that of the opposing spring 22.

Furthermore, in order to prevent the disturbance of the damping force waveform (hunting phenomenon) that occurs when switching from a loaded state to an empty state, an oil sump chamber (douche pot) 2 is created between the sliding surfaces of the sleeve 15 and the guide 10 only when the vehicle is loaded.
4 is provided, and this oil reservoir chamber 24 is communicated with the lower chamber 8 via a minute gap or narrow passage (not shown).

It should be noted that the extension side passage 26 that allows oil in the reservoir chamber 4 to flow toward the lower chamber 8 via the check valve 25 only when the shock absorber is operated on the extension side is connected to the outside of the guide 10, that is, between the sleeve 15, the stopper 23, and the inner cylinder 2. is formed between. The check valve 25 consists of an annular valve body 25a seated on the base valve case 9 and a disc spring 25b that biases the valve body 25a in the valve closing direction. A plurality of ports 27 are provided.

When the vehicle is empty and the loaded weight is small, the piston 5 strokes at the top of the inner cylinder 2, so the unfixed tip of the position detection spring 21 separates from the back surface of the piston 5, as shown in FIG. Since the sleeve 15 becomes a free length and the biasing force on the sleeve 15 is cut off, the sleeve 15 is pushed up toward the lower chamber 8 by the opposing spring 22 until it comes into contact with the end surface of the large-diameter stepped portion 28 of the guide 10. As a result, the side passage 14 provided in the guide 10 opens, and the lower chamber 8 and the contraction side passage 13 are short-circuited via the side passage 14 without passing through the second damping valve 12.

Therefore, when the shock absorber is operating on the contraction side when the vehicle is empty, as the piston 5 descends, the oil in the lower chamber 8 flows through the piston 5 to the upper chamber 7, as shown by the thick solid arrow A in FIG. As the oil flows, oil corresponding to the volume of entry of the piston rod 6 passes from the lower chamber 8 through the side passage 14 to the contraction side passages 13', 13 intermediate between the first and second damping valves 11, 12.
It flows into the reservoir chamber 4 through the constant orifice 19 in a region where the speed of the piston 5 is very slow (for example, 0.1 m/sec or less), but in a region where the speed of the piston 5 is faster (for example, 0.1 m/sec or more). Then, at the same time, the first damping valve 11
is pushed open and flows into the reservoir chamber 4. At this time, the oil that has passed through the constant orifice 19 and the first damping valve 11 enters the reservoir chamber 4 through the port 29 provided in the sub-guide 16, the filter 30, and the annular stop pin 31. The damping force generated at this time is determined by the set load of the first damping valve 11, and therefore, the set load of the first damping valve is adjusted to the required damping characteristic b during compression side operation when the vehicle is empty as shown in FIG. By setting it accordingly, it is possible to exhibit a damping characteristic that meets the required characteristic b.

On the other hand, when the vehicle is loaded with a large load, the piston 5 strokes at the bottom of the inner cylinder 2, as shown in FIG. The sleeve 15 is pressed down against the biasing force of the opposing spring 22 until it comes into contact with the end of the stopper 23. As a result, the side road 14
is closed by the inner peripheral wall of the sleeve 15.

Therefore, the loaded weight increases and the sleeve 15
When the side passage 14 is closed as shown in FIG. 4, as the piston 5 descends, the oil in the lower chamber 8 passes through the piston 5 and flows into the upper chamber 7, as shown by the thick solid arrow A' in FIG. At the same time, oil corresponding to the entering volume of the piston rod 6 flows from the lower chamber 8 to the constant orifice 20 during the contraction side operation in the region where the speed of the piston 5 is slow. Sometimes, the second damping valve 12 is pushed open at the same time to open the compression side passage 1 between the first and second damping valves 11 and 12.
3', 13. The oil entering the passage 13' flows into the reservoir chamber 4 through the constant orifice 19 as described above, or simultaneously by pushing open the first damping valve 11. Therefore, the generated damping force characteristics at this time are determined by the sum of the set load of the second damping valve 12 and the set load of the first damping valve 11. That is, the second damping valve 12 is responsible for generating the difference in damping force between when the vehicle is empty and when the vehicle is loaded. Therefore, by setting the combined set load of the second damping valve 12 and the first damping valve 11 so as to match the required damping characteristic a during the contraction side operation when loading a vehicle as shown in FIG. A large damping characteristic matching characteristic a can be obtained.

Of course, the damping characteristics during the contraction side operation can be freely set by appropriately selecting the set loads of the first and second damping valves 11 and 12. Compared to a method in which the port area is changed and the characteristics are relatively changed by the rear aperture effect due to the port resistance, the required damping characteristics can be brought closer to the required attenuation characteristics. In particular, when the piston 5 moves at low speeds (e.g., 0.3 m/sec or less), the damping force on the compression side when the vehicle is empty and when the vehicle is loaded can be varied over a wide and arbitrary range. This can significantly improve performance and ride comfort when the vehicle is empty.

Note that when the shock absorber is operating on the rebound side, oil equivalent to the rod charge (volume of regression) of the piston rod 6 flows from the reservoir chamber 4 to the base valve case 9, whether the vehicle is empty or loaded.
The water passes through the port 27, pushes open the check valve 25, and flows into the lower chamber 8. In the present invention, the compression side damping force generation mechanism provided on the piston 5 can be shared with the mechanism provided on the base valve 3, which simplifies the mechanism and facilitates shock reduction. Can be incorporated into an absorber.

As described above, according to the present invention, two damping valves with different characteristics are arranged in series at the bottom of the lower chamber, and a side passage communicating between them is opened and closed depending on the loaded weight. Therefore, compression-side damping characteristics can be provided depending on the requirements when the vehicle is empty and when the vehicle is loaded.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the damping characteristics, Fig. 2 is a schematic sectional view of the shock absorber of the present invention, Fig. 3 is an enlarged sectional view of the base valve portion of Fig. 2 when the vehicle is empty, and Fig. 4 is a graph showing the damping characteristics. FIG. 6 is an enlarged cross-sectional view of the base valve portion when the vehicle is loaded. 1... Outer cylinder, 2... Inner cylinder, 3... Base valve, 4... Reservoir chamber, 5... Piston, 6...
Piston rod, 7... upper chamber, 8... lower chamber,
10... Guide, 11... First damping valve, 12...
Second damping valve, 13... Contraction side passage, 14... Side passage, 15... Sleeve, 21... Position detection spring, 22... Spring, 23... Stopper,
24...oil reservoir chamber, 25...check valve, 26...extension side passage.

Claims (1)

[Claims] 1 A base valve is provided at the bottom of the inner cylinder, and this base valve is equipped with first and second damping valves arranged in series so as to allow only flow from the lower chamber to the reservoir chamber during contraction side operation. A shock absorber is provided with a side passage that short-circuits the middle of these damping valves and a lower chamber, and is also provided with a sleeve that opens and closes this side passage in accordance with the relative positional displacement of the piston.