JP2001041272A - Damping force adjustment type hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable damping force characteristics on the shrinkage side, in a damping force regulation type hydraulic buffer having a pilot type damping valve. SOLUTION: A slidable piston is fitted in a cylinder sealed with oil liquid, and a main oil liquid passage through which oil liquid flows through slide of the piston and an auxiliary oil liquid passage situated in parallel to the main oil liquid passage are provided. A pilot type damping valve 48 and a subvalve 47 are situated in the main oil liquid passage, and a fixed orifice 52 and variable orifices 53 and 56 in the auxiliary oil liquid passage. The effective passage area of an orifice passage 59 situated in the subvalve 47 is increased to a value higher than that of the fixed orifice 52. This constitution directly adjusts damping force before opening of a pilot type damping valve and simultaneously adjusts the opening pressure of the pilot type damping valve by changing a pilot pressure, and prevents the generation of a stiff feeling at the section of a low piston speed area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force-adjustable hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile.

[0002]

2. Description of the Related Art A hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile is provided with a damping force that can be appropriately adjusted in order to improve riding comfort and steering stability in accordance with road surface conditions, running conditions, and the like. There is a damping force adjustable hydraulic shock absorber.

[0003] In general, a damping force adjusting type hydraulic shock absorber slidably fits a piston having a piston rod connected to a cylinder filled with an oil liquid so as to divide the cylinder into two chambers.
The piston section is provided with a main oil passage and a bypass passage for communicating the two chambers in the cylinder. The main oil passage is provided with a damping force generating mechanism comprising an orifice and a disc valve. The damping force adjusting valve for adjustment is provided.

Then, the bypass passage is opened by the damping force adjusting valve to reduce the flow resistance of the oil fluid between the two chambers in the cylinder to reduce the damping force, and the bypass passage is closed to reduce the flow between the two chambers. The damping force is increased by increasing the resistance. As described above, the damping force characteristic can be appropriately adjusted by opening and closing the damping force adjustment valve.

However, when the damping force is adjusted by the passage area of the bypass passage as described above, the damping force depends on the restriction of the orifice of the oil liquid passage in a low piston speed range. Although it can be largely changed, in the middle and high speed range of the piston speed, the damping force characteristic greatly changes because the damping force depends on the opening of the damping force generation mechanism (disk valve etc.) of the main oil liquid passage. Can not.

Therefore, for example, Japanese Patent Application Laid-Open No. 62-220728
As described in Japanese Patent Application Laid-Open Publication No. H11-260, a pressure chamber (pilot chamber) is formed at the back of a disk valve, which is a damping force generation mechanism for a main oil liquid passage common to the expansion and contraction side, and this pressure chamber is connected via a fixed orifice. It is known that the communication is made with the cylinder chamber on the upstream side of the disk valve and with the cylinder chamber on the downstream side of the disk valve via a variable orifice (flow control valve).

According to this damping force adjusting type hydraulic shock absorber, by opening and closing the variable orifice, the area of the communication passage between the two chambers in the cylinder is adjusted, and the pressure in the pressure chamber is reduced by the pressure loss generated in the variable orifice. This can be changed to change the initial valve opening pressure of the disk valve.
In this way, the orifice characteristics (the damping force is approximately proportional to the square of the piston speed) and the valve characteristics (the damping force is approximately proportional to the piston speed) can be adjusted,
The adjustment range of the damping force characteristic can be widened.

[0008]

However, the conventional damping force-adjustable hydraulic shock absorber has the following problems. In the above-mentioned conventional damping force adjusting type hydraulic shock absorber, a spool valve or the like is generally used as a variable orifice.
Variations in the dimensions of the sleeve, spool, port, etc. due to processing accuracy cause a variation in the channel area of the microchannel formed when the damping force specification is adjusted to the hard side, that is, when the variable orifice is closed. It is difficult to obtain stable damping force characteristics on the hard side.

The present applicant has filed Japanese Patent Application No. 10-366657 (hereinafter referred to as a prior application) in order to improve the above-mentioned disadvantages. This application discloses a cylinder filled with an oil liquid, a piston slidably fitted in the cylinder, and a piston rod having one end connected to the piston and the other end extending outside the cylinder. A main oil passage through which the oil flows by sliding the piston, a sub oil passage provided in parallel with the main oil passage, a sub-valve provided in the main oil passage, and a pilot damping member. A valve, a fixed orifice and a variable orifice provided in the sub-oil passage, and a pressure between the fixed orifice and the variable orifice in the sub-oil passage is set as a pilot pressure of the pilot damping valve. A damping force adjusting hydraulic shock absorber, wherein an orifice passage is provided in parallel with the variable orifice.

However, according to the present invention, as shown in FIG. 7, the damping force characteristic on the contraction side becomes as shown by a broken line, and a projection such as a point P is generated in the middle of the orifice characteristic. A defect was found in which a feeling of "lumpy" occurred in the section of the area.

[0011]

In order to solve the above-mentioned problems, the present invention provides a cylinder filled with an oil liquid, a piston slidably fitted in the cylinder, and one end of the piston. , A piston rod having the other end extended out of the cylinder, a main oil passage through which oil flows by sliding the piston, and a sub-oil provided in parallel with the main oil passage. A liquid passage, a pilot damping valve provided in the main oil passage, a fixed orifice and a variable orifice provided in the sub oil passage, a sub-valve provided in the main oil passage, and a sub-valve provided in the main oil passage. An orifice passage whose effective notification area is larger than the fixed orifice. The pressure between the fixed orifice and the variable orifice of the sub-oil passage is controlled by the pilot valve of the pilot damping valve. Are those that set as the Tsu door pressure.

With this configuration, by adjusting the opening of the variable orifice, the damping force before opening the pilot type damping valve is directly adjusted, and at the same time, the pilot pressure is changed to change the pilot type damping valve. When the valve opening pressure is adjusted and the flow area of the variable orifice is reduced, the flow rate of the secondary oil liquid passage is substantially determined by the orifice passage, and the flow rate of the variable orifice is less affected by the variation of the flow area. At the same time as the effect of the request, the feeling of “raggy” in the section of the extremely low piston speed range which the prior application had is eliminated. That is, although the details will be described later, by moving the projection at the point P in FIG. 7 to the position of the point Y2 in FIG. 6, the damping force characteristic in the low piston speed region is improved.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 6 show a first embodiment of the present invention.
This will be described with reference to FIG.

In the drawing, a damping force adjusting type hydraulic shock absorber 1
It has a double cylinder structure in which an outer cylinder 3 is provided outside the cylinder 2, and a reservoir 4 is formed between the cylinder 2 and the outer cylinder 3. A piston 5 is slidably fitted in the cylinder 2, and the piston 5 defines the inside of the cylinder 2 into two chambers, an upper cylinder chamber 2a and a lower cylinder chamber 2b. One end of a piston rod 6 is connected to the piston 5 by a nut 7.
Is passed through a cylinder upper chamber 2b, is inserted into a rod guide and a seal member (both not shown) mounted on the upper ends of the cylinder 2 and the outer cylinder 3, and extends outside the cylinder 1. I have. At the lower end of the cylinder 1, a base valve 8 for partitioning the cylinder lower chamber 2b and the reservoir 4 is provided. An oil liquid is sealed in the cylinder 2, and an oil liquid and a gas are sealed in the reservoir 4.

The piston 5 is provided with oil passages 9 and 10 for communicating between the cylinder upper and lower chambers 2a and 2b. The oil passage 9 is provided with a check valve 11 that allows only the flow of the oil liquid from the cylinder lower chamber 2b side to the cylinder upper chamber 2a side. Oilway 10
Is provided with a relief valve 12 that opens when the pressure of the oil liquid on the cylinder upper chamber 2a side reaches a predetermined pressure, and relieves it to the cylinder lower chamber 2b side. The base valve 8 is provided with oil passages 13 and 14 for communicating the cylinder lower chamber 2b and the reservoir 4. The oil passage 13 is provided with a check valve 15 that allows only the flow of the oil liquid from the reservoir 4 side to the cylinder lower chamber 2b side. In the oil passage 14, the cylinder lower chamber 2b
A relief valve 16 is provided which opens when the pressure of the oil liquid on the side reaches a predetermined pressure and relieves it to the reservoir 4 side.

A substantially cylindrical passage member 17 is fitted on the outer periphery of the cylinder 2, and annular oil passages 18 and 19 are formed between the cylinder 2 and the passage member 17. The annular oil passage 18 is communicated with the upper cylinder chamber 2a via an oil passage 20 provided on a side wall near the upper end of the cylinder 2, and the annular oil passage 19 is provided on a side wall near the lower end of the cylinder 2. The oil passage 21 communicates with the lower cylinder chamber 2b. A damping force generating mechanism 22 is attached to the side surface of the outer cylinder 3, and three connection ports 24, 25, 26 provided in a case 23 of the damping force generating mechanism 22 are connected to connection pipes 27, 28, respectively. It is connected to the annular oil passages 18 and 19 and the reservoir 4 via 29.

The damping force generating mechanism 22 is, as shown in FIG.
Four valve bodies 32, 33, 34, and 35 through which a sleeve 30 is inserted and integrally connected by a nut 31 are fitted into a substantially bottomed cylindrical case 23. 36 (hereinafter referred to as actuator 36) is attached, and the inside of case 23 is a valve body.
The three oil chambers 22a, 22b and 22c are defined by the connection ports 32, 34 and communicate with the connection ports 24, 25 and 26, respectively. The sleeve 30 is screwed to the actuator 36, and the operating rod 37 of the actuator 36 is inserted therein.

The valve body 32 is provided with an oil passage 38 for communicating between the oil chambers 22a and 22b. Oil passage 38 has an oil chamber
A main valve 39 (disk valve), which is a pilot-type damping valve that opens upon receiving the pressure of the oil liquid on the side 22a and generates a damping force corresponding to the opening degree, is provided. A plurality of disk-shaped seal members 40 are laminated on the main valve 39, and the seal members 40 include a plurality of disks 40a,
40b, 40c, 40d, and 40e.
In FIG. 5A, six fixed orifices 43 are formed around the periphery as shown in FIG. And, with this seal member 40,
A pilot chamber 42 is formed on the back side of the main valve 39 by the valve body 33 and an annular seat member 41 externally fitted to the valve body 33. The main valve 39 is closed by a force due to the internal pressure of the pilot chamber 42. Is pressed.
The pilot chamber 42 communicates with the oil passage 38 via the fixed orifice 43 provided on the seal member 40, and communicates with a port 44 provided on the side wall of the sleeve 30. The sleeve 30 is provided with a port 45 communicating with the oil chamber 22b at a position different from the port 44 in the axial direction.

The valve body 34 is provided with an oil passage 46 for communicating between the oil chambers 22b and 22c. The oil passage 46 has an oil chamber
An upstream sub-valve 47 (disc valve) and a downstream main valve 48 (disc valve) for opening the valve under the pressure of the oil liquid on the 22b side and generating a damping force according to the opening degree are provided. I have. A plurality of disc-shaped seal members 49 are laminated on the main valve 48 in the same manner as the seal member 40.
a, 49b, 49c, and 49d, and the uppermost disk 49a
There are six fixed orifices around the perimeter as seen in FIG.
52 are formed. A pilot chamber 51 is formed on the back side of the main valve 48 by the seal member 49, the valve body 35, and the annular seat member 50 externally fitted to the valve body 35. Presses the main valve 48 in the valve closing direction. The pilot chamber 51 communicates with the oil passage 46 through the fixed orifice 52 provided in the seal member 49, and has a sleeve
It is communicated with a port 53 provided on the side wall of 30. The sleeve 30 has an oil chamber at a position different from the port 53 in the axial direction.
A port 54 communicating with 22c is provided. The sub-valve 47 is composed of a plurality of disks 47a, 47b, 47c, and the uppermost disk 47a is formed with a fixed orifice indicated by reference numeral 59, and the fixed orifice 59 has a peripheral orifice as shown in FIG. A plurality of fixed orifices 59 are formed. The sum of the opening areas A (shown by reference numeral A in FIG. 4) of the fixed orifices 59 formed on the disk 47a is equal to the opening area B (shown by reference numeral B in FIG. 4) of the fixed orifices 52 formed on the disk 49a. (Shown) is sufficiently large. Note that the valve opening pressure of the sub-valve 47 is set sufficiently lower than the valve opening pressure of the main valve 48. 3 and 4, reference numerals 60 and 61 denote annular disks. The annular disk 60 has an outer periphery in contact with an annular projection 41a of the sheet member 41, and an inner periphery with the disk 40a and the spacer 62. The outer periphery of the annular disk 61 is in contact with the annular protrusion 50a of the sheet member 50, and the inner periphery is sandwiched between the disk 49a and the spacer 63.

A spool 57 having annular grooves 55 and 56 opposed to the ports 44 and 45 and the ports 53 and 54, respectively, is slidably fitted in the sleeve 30. Spool 57
Has one end in contact with the return spring 58 and the other end in contact with the operating rod 37 of the actuator 36, and moves against the spring force of the return spring 58 in accordance with the thrust of the actuator 36. The flow path areas between the ports 44 and 45 and between the ports 53 and 54 are adjusted. The ports 44, 45 and the annular groove 55 constitute a variable orifice.

In the above configuration, the oil passage 21, the annular oil passage 19, the connection pipe 28, the connection port 25, the oil chamber 22b, the oil passage 46, the oil chamber 22c, the connection port 26, the connection pipe 29, and the reservoir 4 It constitutes the main oil liquid passage on the piston rod 6 contraction side,
Fixed orifice 52, pilot chamber 51, port 53, annular groove
The sub-oil passage is constituted by the port 56 and the port 54.

Next, the operation of the present embodiment configured as described above will be described.

FIG. 6 shows the characteristics of the extension stroke of the piston rod 6.
Is shown by curve E. During the extension stroke of the piston rod 6, the check valve 11 of the oil passage 9 of the piston 5 is closed with the movement of the piston 5, and the oil liquid in the cylinder upper chamber 5a is pressurized.
Before opening the main valve 39, the oil passage 20, the annular oil passage
18 and the connection pipe 27, flows to the connection port 24 of the damping force generating mechanism 22, and further flows into the oil chamber 22a, the oil passage 38, the fixed orifice 43, the pilot chamber 42, the port 44, the annular groove 55, and the port 4.
5, flows through the oil chamber 22b, the connection port 25, the connection pipe 28, the annular oil passage 19 and the oil passage 21 to the cylinder lower chamber 2b side. The characteristic at this time is represented by a curve E1 in FIG. In FIG. 6, the vertical axis represents the damping force, and the horizontal axis represents the piston speed. And
When the pressure on the cylinder upper chamber 2a side reaches the valve opening pressure of the main valve 39 (point X in FIG. 6), the main valve 39 is opened and the oil liquid flows directly from the oil passage 38 to the oil chamber 22b. At this time, the oil liquid corresponding to the piston rod 6 withdrawn from the cylinder 2 is supplied from the reservoir 4 to the cylinder lower chamber 2b by opening the check valve 15 of the oil passage 13 of the base valve 8. This characteristic corresponds to the curve E2 in FIG.
It is represented by

Thus, during the extension stroke, the piston speed is low, and before the main valve 39 is opened, a damping force having an orifice characteristic corresponding to the flow area between the fixed orifice 43 and the ports 44 and 45 of the spool valve is generated. Occurs (curve E in FIG. 6).
1) When the piston speed increases and the pressure on the cylinder upper chamber 2a side increases and the main valve 39 opens, a damping force of valve characteristics is generated according to the opening (curve E2 in FIG. 6). Then, the spool 57 is moved by the actuator 36 to adjust the flow path area between the ports 44 and 45,
Direct adjustment of the orifice characteristics and port 44, 45
By changing the pressure in the pilot chamber 42 (the pressure acting in the valve closing direction of the main valve 39) by the pressure loss between them, the damping force characteristic is changed to the "damping force variable range" on the extension side in FIG.
It can be adjusted to various characteristics as shown by.

On the other hand, during the contraction stroke of the piston rod 6 shown by the curve C in FIG. Since the cylinder upper and lower chambers 2a and 2b have substantially the same pressure by flowing directly into the cylinder upper chamber 2a through the passage, no oil liquid flows between the connection ports 24 and 25 of the damping force generating mechanism 22. Then, as the piston rod 6 enters the cylinder 2, the check valve 11 of the base valve 8 closes. on the other hand,
The oil liquid in the cylinder 2 is pressurized to the extent that the piston rod 6 enters, but the pressure in the lower chamber 2b is higher than the pressure in the upper chamber 2a in the cylinder upper and lower chambers 2a and 2b by the pressure loss of the check valve 15. Therefore, before the main valve 48 is opened, the cylinder lower chamber
From 2b, the oil flows through the oil passage 21, the annular oil passage 19, and the connection pipe 28 to the connection port 25 of the damping force generating mechanism 22.
b, oil passage 46, sub-valve 47, fixed orifice 52, pilot chamber 51, port 53, annular groove 56, port 54, oil chamber 22c,
It flows to the reservoir 4 through the connection port 26 and the connection pipe 29. Then, as the piston 5 moves, the pressure on the cylinder lower chamber 2b side gradually increases, and the oil liquid flows out from the fixed orifice 52. The characteristic at this time is represented by a curve C1 in FIG. When the pressure on the cylinder lower chamber 2b side reaches the valve opening pressure of the main valve 48 (point Y1 in FIG. 6), the main valve 48 is opened and the oil liquid flows directly from the oil passage 46 to the oil chamber 22c. The characteristic at this time is shown by a curve C2. At this time, the sub-valve 47 has not been opened yet. Thereafter, when the movement of the piston 5 progresses and reaches the point Y2, the sub-valve 47 is opened, and thereafter, the characteristic as shown by the curve C3 is obtained. This curve C shows the characteristic M of the main valve 48 and the fixed orifice 52 and the sub valve 47.
And the characteristic S with the characteristic S. As can be seen from FIG. 6, the valve opening position Y2 of the sub-valve 47 is shifted from the valve opening position Y1 of the main valve 48, and this "shift" eliminates the feeling of "raggy" in the section of the extremely low piston speed range. . That is, if the valve opening position Y2 of the sub-valve 47 is located in the middle of the curve C1, the above-mentioned "lumpy" feeling is generated.

As described above, during the contraction stroke, before the main valve 48 is opened, the sub valve
47, fixed orifice 52 and spool valve ports 53, 54
When the damping force of the orifice characteristic is generated in accordance with the flow path area between them (curve C1 in FIG. 6), the piston speed gradually increases, the pressure on the cylinder lower chamber 2b side increases, and the main valve 48 opens. The damping force of the valve characteristics is generated according to the degree (curves C2 and C3 in FIG. 6). The orifice characteristics are directly adjusted by moving the spool 57 by the actuator 36 to adjust the flow path area between the ports 53 and 54, and the pressure (pressure) of the pilot chamber 51 by the pressure loss between the ports 53 and 54. By changing the pressure acting in the valve closing direction of the main valve 48), the damping force characteristic can be adjusted to various characteristics as shown in the "damping force variable range" on the compression side in FIG.

[0028]

As described in detail above, the damping force-adjustable hydraulic shock absorber according to the present invention is provided with a sub-valve in the main oil passage, and the effective passage area of the orifice passage provided in this sub-valve is the effective area of the fixed orifice. Since it is larger than the passage area, the damping force before opening the pilot type damping valve is directly adjusted by adjusting the opening of the variable orifice, and at the same time, the pilot pressure is changed to open the pilot type damping valve. In addition to adjusting the valve pressure, the feeling of "craggyness" in the section of the low piston speed range which the prior application had is eliminated.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a damping force adjusting type hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a damping force generating mechanism of the device of FIG.

FIG. 3 is an enlarged view of a main valve 39 part.

FIG. 4 is an enlarged view of a main valve 48 part.

FIG. 5 is a plan view of the disc valves 40a, 47a, and 49a.

FIG. 6 is a damping force characteristic of the device of FIG.

FIG. 7 shows damping force characteristics of the prior application.

[Explanation of symbols]

 1 damping force adjustable hydraulic shock absorber 2 cylinder 2a upper cylinder chamber 2b lower cylinder chamber 3 outer cylinder 4 reservoir 5 piston 6 piston rod 7 nut 8 base valve 9 oil passage 10 oil passage 11 check valve 12 relief valve 13 oil passage 14 Oil passage 15 Check valve 16 Relief valve 17 Passage member 18 Annular oil passage 19 Annular oil passage 20 Oil passage 21 Oil passage 22 Damping force generation mechanism 22a Oil chamber 22b Oil chamber 22c Oil chamber 23 Case 24 Connection port 25 Connection port 26 Connection Port 27 Connection pipe 28 Connection pipe 29 Connection pipe 30 Sleeve 31 Nut 32 Valve body 33 Valve body 34 Valve body 35 Valve body 36 Proportional solenoid actuator 37 Operating rod 38 Oil passage 39 Main valve 40 Seal member 40a Disc 40b Disc 40c Disc 40d Disc 40e Disc 41 Seat member 41a Annular protrusion 42 Pilot chamber 43 Fixed orifice 44 Port 45 Port 46 Oil 47 Sub valve 48 Main valve 49 Seal member 49a Disk 49b Disk 49c Disk 49d Disk 50 Seat member 50a Annular protrusion 51 Pilot chamber 52 Fixed orifice 53 Port 54 Port 55 Annular groove 56 Annular groove 57 Spool 58 Return spring 59 Fixed orifice 60 Annular disk 61 Annular disk 62 Spacer 63 Spacer

Claims (1)

[Claims] 1. A cylinder filled with oil, a piston slidably fitted in the cylinder, and a piston rod having one end connected to the piston and the other end extending outside the cylinder. A main oil passage through which oil flows by sliding the piston, a sub oil passage provided in parallel with the main oil passage, and a pilot damping valve provided in the main oil passage. A fixed orifice and a variable orifice provided in the sub-oil passage, a sub-valve provided in the main oil passage, and an orifice passage provided in the sub-valve and having an effective passage area larger than the fixed orifice. A damping force-adjustable hydraulic shock absorber, wherein a pressure between the fixed orifice and the variable orifice of the sub-oil passage is used as a pilot pressure of the pilot-type damping valve.