JP2515440Y2 - Variable damping force type hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a hydraulic shock absorber that is suitable for use in a vehicle suspension and that can change damping force characteristics.

(Prior Art) As a conventional damping force variable type hydraulic shock absorber, for example, one described in Japanese Utility Model Laid-Open No. 58-92537 is known.

In such a conventional structure, as a means for generating a damping force at each extension / compression stroke, an extension-side communication hole and a compression-side communication hole that communicate the upper liquid chamber and the lower liquid chamber are formed in parallel with the piston. , A disc valve for opening and closing this communication hole is provided, and on the other hand, a communication passage is formed in the piston rod by connecting the upper liquid chamber and the lower liquid chamber in parallel with the communication hole, and in the middle of this communication passage. The changing means for selectively changing the flow passage cross-sectional area of the communication passage is provided.

As the changing means, it is common to open or close the communication passage or provide a variable orifice having an orifice hole having a plurality of diameters, and selectively change the diameter of the orifice hole in the communication passage. Target.

Therefore, in the low piston speed range, the hydraulic fluid flows through the communication passage to generate a damping force due to the orifice, etc., and in the medium / high piston speed range, the hydraulic fluid opens and flows through the disc valve. A damping force is generated between the seat surface.

Further, when the flow passage cross-sectional area is narrowed by the changing means, the damping force range becomes high, and when the open flow passage cross-sectional area becomes wide, the damping force range becomes low.

(Problems to be solved by the invention) However, in such a conventional damping force variable type hydraulic shock absorber, as described above, the change of the damping force range is a gradual selective switching. There is a problem that the setting of is limited, and it is not possible to set the optimum damping force characteristic according to each situation.

In addition, since the damping force characteristic of the disc valve and the damping force characteristic of the orifice are obtained in parallel, the damping force characteristic greatly changes in the middle of the low speed range to the medium / high speed range,
There is also a problem that a constant characteristic cannot be obtained over the entire piston speed.

The present invention has been made by paying attention to the conventional problems as described above, and it is possible to continuously change the damping force range and obtain a constant damping force characteristic over the entire piston speed. It is an object of the present invention to provide a variable damping force type hydraulic shock absorber.

(Means for Solving the Problems) In the damping force variable type hydraulic shock absorber of the present invention, a piston provided by defining a cylinder filled with hydraulic fluid into two fluid chambers, and at least this piston An inner groove and an outer groove, which are double-sided on one side of the liquid chamber and have a seat surface on the outer periphery of each, and a disc valve provided in contact with the seat surface to open and close both grooves. , A communication path that communicates the inner groove and the other liquid chamber with the piston in between, and a bypass path that communicates the inner groove and the outer groove, and a throttle is formed in the middle of the bypass path in the axial direction of the piston. A slidable spool and driving means for applying a driving force to the spool to slide the spool are provided.

(Operation) In the variable damping force type hydraulic shock absorber of the present invention, the working fluid flows from the other fluid chamber to the one fluid chamber through the communication passage due to the stroke of the piston. The flow path changes, and the damping force characteristics change accordingly.

That is, the hydraulic fluid in the other liquid chamber flows into the inner groove through the communication passage, flows from the inner groove into the outer groove, and the disc valve is opened from the outer groove to flow into the one liquid chamber. When flowing into the outer groove from the inner groove, the second path passes between the first path passing through the bypass path and the seat surface of the inner groove and the disk valve (that is, the disk valve is opened).
There are two parallel paths with

Therefore, in the low piston speed range, the gas flows into the outer groove through the first path (bypass path) and the throttle formed by the spool in the middle thereof.

Therefore, the damping force of the velocity square characteristic is generated in the aperture,
Further, a damping force having a velocity 2/3 power characteristic is generated in series with the disc valve (between the seat surface of the outer groove).

In this way, the damping force of the velocity squared characteristic that the change rate increases as the piston speed increases and the damping force of the velocity 2/3 power characteristic that the change rate decreases as the piston speed increases are obtained in series. By canceling the change in the rate of change, a linear characteristic linearly proportional to the piston speed can be obtained.

On the other hand, in the medium / high piston speed range, the hydraulic fluid that has flowed into the inner groove flows into the outer groove from the second path (disc valve opening) in response to the increase in resistance due to the restriction of the bypass path.

Therefore, in this case, at the disc valve at the seat surface position of the inner groove, a damping force of the speed 2/3 power characteristic is generated, and in series with it, the velocity at the seat surface position of the outer groove becomes 2/3. The damping force of the riding characteristic is generated.

Thus, in the middle / high piston speed range where the rate of change in the damping force of the velocity 2/3 power characteristic with respect to the change in piston speed decreases, this damping force of the velocity 2/3 power characteristic is obtained in series to obtain this change. It is possible to obtain a linear damping force characteristic that is linearly proportional to the piston speed, as in the low piston speed range, by suppressing the decrease in the rate and maintaining a constant rate of change.

Further, when the spool is slid, the aperture of the diaphragm changes continuously. By changing the opening of the throttle in this way, the damping force characteristic of the bypass passage can be changed, and at the same time, the piston speed when the valve is opened in the inner groove also changes, and the damping force characteristic of the disc valve changes. To do.

That is, when the throttle opening is narrowed, a high range damping force characteristic is obtained, and when the throttle opening is opened, a low registration damping force characteristic is obtained. And since this opening change is continuously made steplessly,
This damping force range can also be continuously changed without any step.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

 First, the configuration of the embodiment will be described.

FIG. 1 is a sectional view showing a main part of a damping force variable type hydraulic shock absorber according to a first embodiment of the present invention, in which 1 denotes a cylindrical cylinder. This cylinder 1 has an upper liquid chamber A and a lower liquid chamber B which are slidably mounted by a piston 2.
And two liquid chambers, and both chambers A and B are filled with hydraulic fluid such as oil.

The piston 2 is attached to a tip of a piston rod 3. That is, with respect to the piston rod 3, a rebound stopper 5, a washer 6, a first pressure side disc valve 7,
2nd compression side disc valve 8, piston 2, 1st extension side disc valve 9, 2nd extension side disc valve 10, washer 11, spring seat 12, spring 13 are installed in this order, and finally they are fastened with nut 14 ing.

More specifically, the piston 2 is provided with a piston through hole 2a at the center for inserting the piston rod 3 therethrough,
The piston 2 is attached to the piston rod 3 while being prevented from rotating by forming a D-cut cross-sectional shape of the mounting portion between the through hole 2a and the piston rod 3.

Further, on the upper end surface of the piston 2 on the upper liquid chamber A side,
A pressure-side inner groove 2b and a pressure-side outer groove 2c are formed in the inner and outer double layers. As shown in FIG. 2 which is a plan view of the piston 2, the both grooves 2b, 2c are formed in a substantially annular shape, and an inner seat surface 2d and an outer seat surface 2e are formed on the outer periphery thereof, respectively. Then, as shown in FIG. 1, the pressure side inner groove 2b is formed.
Is communicated with the lower liquid chamber B by six pressure side communication holes (communication passages) 2f formed in the piston 2 in the vertical direction.
The pressure side inner groove 2b is formed through the pressure side communication grooves 2g, 2h formed in the upper end surface of the piston 2, the piston through hole 2a, and the pressure side ports 3a, 3a formed in the piston rod 3 and the pressure side outer groove 2b.
It is in communication with c. That is, the pressure side communication grooves 2g, 2h, the piston through hole 2a, and the pressure side ports 3a, 3a form a pressure side bypass passage By1.

The second pressure side disc valve 8 is brought into contact with both seat surfaces 2d and 2e, and the outer peripheral portion is disposed at the position of the inner seat surface 2d so that the first pressure side disc valve 7 becomes the second pressure side disc valve. 8 are provided in a stack.

On the other hand, the lower end surface of the piston 2 on the lower liquid chamber B side is also symmetrical to the upper end surface side, that is, on the lower end surface,
An extension side inner groove 2j and an extension side outer groove 2k are formed in the inner and outer double layers.

Both grooves 2j, 2k are formed in a substantially annular shape, the outer periphery of which is
An inner seat surface 2m and an outer seat surface 2n are formed respectively.

Then, as shown in FIG. 1, the expansion side inner groove 2j is
The piston 2 is communicated with the upper liquid chamber A by eight expansion-side communication holes (communication passages) 2p formed in the vertical direction, and the expansion-side inner groove 2j is formed on the lower end surface of the piston 2. The extension side outer groove 2k is formed through the side communication grooves 2q, 2r, the piston through hole 2a, and the extension side ports 3b, 3b formed in the piston rod 3.
It is in communication with. That is, the extension side communication grooves 2q, 2r, the piston through hole 2a, and the extension side ports 3b, 3b form an extension side bypass passage By2.

The first extension side disc valve 9 is in contact with both seat surfaces 2m and 2n.
The outer peripheral portion of the extension side disc valve 10 is arranged, and the spring force of the spring 13 is applied to this position via the spring seat 12.

Further, a through hole 3c is formed inside the piston rod 3 so as to pass through the axial center of the piston rod 3 in the vertical direction, and a spool 15 is provided at the lower end of the through hole 3c.

This spool 15 has a male screw portion 15a provided at its lower end.
Is provided by being screwed into a female screw portion 3d provided at the lower end of the through hole 3c, and this spool 15 is slidable in the axial direction within the through hole 3c by rotating. .

Further, on the outer peripheral edge portions of the spool 15 at positions corresponding to the compression side ports 3a, 3a and the expansion side ports 3b, 3b formed on the piston rod 3, respectively, a compression side annular groove 15b and an expansion side annular groove are formed. Since the groove 15c is formed, it is possible to form a throttle between the two annular grooves 15b, 15c in the axial direction of the spool 15 (vertical direction in the drawing) and the compression side ports 3a, 3a and the extension side ports 3b, 3b. There is.

In other words, based on this change in the opening of the throttle, both bypass paths are
It is possible to continuously and steplessly change the cross-sectional area of By1 and By2.

The rotation of the spool 15 is performed by a control rod 16 provided in the through hole 3c. The control rod 16 extends to the upper end of the piston rod 3 as shown in FIG. It is divided into two parts at the upper end through a joint 17. The joint 17 is formed in a tubular shape, and the upper and lower sides of the joint 17 are sandwiched by thrust bushes 18 and 19 and are rotatably provided.
By connecting the upper end portion of the lower rod 16b to the lower end portion thereof by spline connection, the lower rod 16b is connected in a state in which axial sliding of the lower rod 16b and rotation transmission from the upper rod 16a are possible.

The upper rod 16a extends to the upper end portion of the piston rod 3, and a rotational force is applied by an actuator (not shown) provided on the vehicle body mounting portion of the piston rod 3.

An O-ring 20 for sealing the gap between the upper rod 16a and the through hole 3c is provided on the upper thrust bush 18.
The thrust bush is attached to the upper part of the
21 is installed.

 Next, the operation of the embodiment will be described.

(A) During Stroke During the stroke of the piston 2, the hydraulic fluid in the upper liquid chamber A flows into the lower liquid chamber B as the hydraulic pressure in the upper liquid chamber A rises. Is as follows.

First, the hydraulic fluid in the upper liquid chamber A flows into the extension side inner groove 2j through the extension side communication hole 2p. Then, the working fluid flows from the extension side inner groove 2j to the extension side outer groove 2k through two routes, and from there, the first extension side disk valve 9 is opened at the position of the outer seat surface 2n. Flow into the lower liquid chamber B.

The first path of the paths from the expansion side inner groove 2j to the expansion side outer groove 2k is a path from the expansion side inner groove 2j to the expansion side outer groove 2k via the expansion side bypass path By2, and The path is from the extension side inner groove 2j to both disc valves 9 and 10 and the spring.
It is a route that opens the valve at the position of the inner seat surface 2m against the valve closing force of 13 and reaches the extension side outer groove 2k.

Which of these two paths the hydraulic fluid flows through is determined by the piston speed, the rigidity of both disc valves 9, 10, the pressure receiving area, and the like.

That is, when the piston 2 slides at a low speed, the flow rate of the hydraulic fluid per unit time is small, so
The hydraulic fluid flows through 2.

Therefore, in this low piston speed range, the extension side bypass path is
A damping force having a velocity squared characteristic is generated in the throttle by the spool 15 provided in the middle of By2 (portion of the extension side annular groove 15c), and in series with it, between the first extension side disc valve 9 and the outer seat surface 2n. A damping force of the speed 2/3 power characteristic is generated at.

That is, the damping force of the velocity squared characteristic in which the rate of change of the damping force increases with the increase of the piston speed, and symmetrically, the velocity 2/3 with which the rate of change of the damping force decreases with the increase of the piston speed. Since the damping force of the multiplicative characteristic is obtained in series, the change in the rate of change of both damping forces is offset, and a linear characteristic linearly proportional to the piston speed is obtained as shown in FIG.

Next, when the piston 2 slides at medium and high speeds, the flow rate of the hydraulic fluid per unit time increases, and the flow rate of the extension side bypass passage By2 is limited. As a result, the double extension side disk valve It resists the valve closing force of 9,10 and the spring 13, and opens at the position of the inner seat surface 2m to flow.

Therefore, in the medium / high piston speed range, the speed between the inner seat surface 2m and the outer seat surface 2n and both disc valves 9 and 10 is increased.
Damping force with 2/3 power characteristic is generated in series.

In other words, in the case of this speed 2/3 power characteristic, the rate of change decreases with increasing piston speed in the medium and high speed regions, but by suppressing this decrease in the rate of change of damping force by obtaining this characteristic in series. As shown in FIG. 4, a linear damping force can be obtained even in the medium / high piston velocity range.

As described above, in this embodiment, it is possible to obtain a linear damping force characteristic linearly proportional to the piston speed in all speed ranges from low speed to high speed.

The stroke range of the damping force characteristics described above is
Slide in the axial direction to change the opening of the throttle formed in the middle of the expansion side bypass path By2 (expansion side port 3
It can be changed by changing the opening amount of the extension side annular groove 15c corresponding to b and 3b).

That is, when the throttle is maximized (when the entire expansion-side annular groove 15c is matched with the expansion-side ports 3b, 3b), the flow rate of the expansion-side bypass passage By2 becomes maximum, and the expansion-side bypass passage By2 The damping force characteristic becomes a low range characteristic and the inner groove
When the valve opening pressure is generated at 2j, the piston speed increases and the damping force characteristic of the disc valve 9 also becomes a low range characteristic, that is, the characteristic shown in FIG.

Further, when the opening of the throttle is minimized, the flow rate of the extension side bypass passage By2 is reduced and the damping force characteristic is in the high range, and the piston speed when the valve opening pressure occurs in the inner groove 2j becomes low. The damping force characteristic of the disc valve 9 is also a high range characteristic, that is, the characteristic shown in FIG.

Furthermore, by setting the opening amount between and based on the sliding of the spool 15, it is possible to continuously and steplessly change to an arbitrary damping force range within this range.

(B) During the pressure stroke During the pressure stroke of the piston 2, the operation is almost symmetrical to that in the above-described extension stroke. That is, when the pressure stroke is performed and the working fluid flows from the lower fluid chamber B to the upper fluid chamber A, the working fluid flows between the pressure side inner groove 2b and the pressure side outer groove 2c through two routes.

That is, there are two paths: a path that flows through the pressure side bypass path By1 and a path that opens the inner seat surface 2d and flows between this seat surface 2d and the second pressure side disk valve 8.

Therefore, as in the case of the extension stroke, the damping force of the velocity square characteristic and the velocity 2/3 characteristic is generated in series in the low piston velocity range, and the damping of the velocity 2/3 characteristic is generated in the middle / high piston velocity range. By generating forces in series, it is possible to obtain a linear damping force characteristic that is linearly proportional to the piston speed.

Also in the case of this pressure stroke, the spool 15 is slid in the axial direction to change the opening degree of the throttle in the middle of the pressure side bypass passage By1, thereby changing from the low range shown in FIG. 4 to the one shown in FIG. Within the range up to the high range, the damping force range can be continuously and steplessly changed.

As described above, the damping force variable hydraulic shock absorber of the first embodiment is characterized in that it is possible to obtain a linear damping force characteristic of the first order in both the compression strokes. By thus obtaining the linear characteristic, the characteristic does not suddenly change depending on the piston speed,
When applied to the suspension of an automobile, it is possible to obtain both the riding comfort and the steering stability.

Since this characteristic is the same even when the throttle opening degree by the spool 15 (opening area of the annular grooves 15b, 15c) is changed, this linear characteristic is obtained in the entire damping force range.

Further, since the damping force range can be continuously and steplessly changed, it is possible to arbitrarily select the optimum damping force characteristic according to each situation.

Further, the above-mentioned throttle control of the spool is performed by sliding the spool in the axial direction. A throttle control structure by such axial sliding is, for example, a hole for an orifice and its hole. It is easier to set the relative position of the two compared to the one that relatively rotates the member that controls the opening degree, and the control itself is stroke control compared to rotation angle control. Something that is easy,
This has the feature that highly accurate diaphragm control can be performed with a simple structure.

In addition, since the hydraulic fluid flow paths are different between the extension stroke and the pressure stroke, independent damping force characteristics can be obtained on the extension side and the pressure side. The feature is that it can be set and the degree of freedom of setting is high.

Next, a second embodiment shown in FIGS. 5 and 6 will be described. In describing the second embodiment, the first
The same components as those of the first embodiment are designated by the same reference numerals as those of the first embodiment and the description thereof is omitted.

The second embodiment is an example in which the control rod 16 and the spool 15 are directly slid in the axial direction without rotating, instead of a motor actuator as an actuator (not shown).

That is, the end cap 20 is provided at the lower end of the through hole 3c of the piston rod 3. Further, between the end cap 20 and the spool 15, a spring 22 for urging the spool 15 to a position where the spool 15 contacts the stopper 21 with respect to the spool 15 (this position is a position where the diaphragm is closed).
Is provided.

Therefore, in the hydraulic shock absorber of the second embodiment, normally, the highest range is set, and by driving the actuator, the characteristic is changed to an arbitrary damping force range lower than that range. be able to.

In this second embodiment, as shown in FIG. 6, the control rod 16 is of a type that is not vertically divided.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change without departing from the gist of the present invention, the present invention is not limited to this embodiment. included.

For example, in the embodiment, the present invention is applied to both the extension side and the compression side, but it may be suitable for only one of them.

(Effect of the Invention) As described above, in the damping force variable type hydraulic shock absorber of the present invention, the inner and outer double grooves are provided on the liquid chamber side of at least one of the pistons, and both grooves are formed. Since the throttle with the spool is provided in the middle of the communicating bypass path, it is possible to obtain a linear damping force characteristic linearly proportional to the piston speed, which is ideal for controlling the damping force characteristic. can get.

Since this characteristic change is made by sliding the spool to change the flow passage cross-sectional area of the bypass passage, the flow passage cross-sectional area is continuously and continuously changed to reduce the damping force. The range can be changed continuously and steplessly, the damping force range of the linear damping force characteristic can be changed steplessly, and it is easy to set the optimum damping force characteristic.
It is also easy to control.

Furthermore, due to the effect that this linear characteristic can be obtained, when applied to the suspension of the automobile without the characteristic changing rapidly with the piston speed, it is possible to achieve both the riding comfort and the steering stability. can get.

In addition, since the internal and external grooves and the disc valve are provided on one side of the piston, the disk valve for the extension stroke and the pressure stroke, the internal and external grooves and the communication passage can be provided independently on both sides of the piston. Therefore, independent damping force characteristics can be obtained on the extension side and the compression side. Therefore, it is possible to obtain the effect that the damping force characteristics can be set independently on the extension side and the compression side.

[Brief description of drawings]

FIG. 1 is a sectional view showing an essential part of a damping force variable type hydraulic shock absorber according to a first embodiment of the present invention, FIG. 2 is a plan view showing an upper surface of a piston of the embodiment, and FIG. 3 is an upper part of a piston rod. 4 is a sectional view showing the damping force characteristic diagram corresponding to the piston speed during both the extension and compression strokes of the embodiment, and FIG. 5 shows the main part of the damping force variable hydraulic shock absorber of the second embodiment. FIG. 6 is a sectional view showing the upper part of the piston rod. A …… Upper fluid chamber B …… Lower fluid chamber By1 …… Pressure side bypass passage By2 …… Extension side bypass passage 1 …… Cylinder 2 …… Piston 2b …… Pressure side inner groove 2c …… Pressure side outer groove 2d …… Pressure side inner Seat surface 2e …… Pressure side outer seat surface 2f …… Compression side communication hole (communication passage) 2j …… Extension side inner groove 2k …… Extension side outer groove 2m …… Extension side inner seat surface 2n …… Extension side outer seat surface 2p ...... Extension side communication hole (communication passage) 7 ...... First pressure side disc valve 8 ...... Second pressure side disc valve 9 ...... First extension side disc valve 10 ...... Second extension side disc valve 15 ...... Spool

Claims (1)

(57) [Scope of utility model registration request] 1. A piston provided inside a cylinder filled with hydraulic fluid to define two liquid chambers, and at least one of the pistons is formed with a double inner and outer side, and An inner groove and an outer groove having a seat surface on the outer periphery, a disc valve provided in contact with the seat surface to open and close both grooves, and the inner groove and the piston are sandwiched between the other liquid chamber. A bypass passage that communicates the communication passage and the inner groove and the outer groove, a spool provided with a throttle in the middle of the bypass passage so as to be slidable in the axial direction of the piston, and a spool for sliding the spool. A damping force variable hydraulic shock absorber, comprising: a driving unit that applies a driving force to the spool.