JPH0624228A - Hydraulic damper - Google Patents

Abstract

(57) [Summary] [Purpose] In a damping force adjustable hydraulic shock absorber, it is possible to simultaneously select different types of damping force characteristics on the extension side and the contraction side. [Structure] A piston 6 to which a piston rod 7 is connected is fitted in a cylinder 2 in which an oil liquid is sealed. On the piston 6,
First and second communication passages 8 and 9 and third and fourth communication passages 1
2 and 13 are provided, and check valves 14 and 15 are provided in the third and fourth communication passages.
To provide. A disc-shaped movable plate 16 having elongated holes 17 and 18 is rotatably provided in the piston 6. By rotating the movable plate 16 to change the alignment between the third and fourth communication passages 12 and 13 and the elongated holes 17 and 18, the passage areas of the third and fourth communication passages 12 and 13 are increased. adjust. Due to the check valves 14 and 15, the oil liquid in the cylinder 2 flows through the fourth communication passage 12 during the extension stroke,
Since it flows through the third communication passage 13 during the compression stroke, different types of damping force characteristics are selected on the extension side and the compression side by adjusting the passage areas of the third and fourth communication passages 12 and 13, respectively. be able to.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile, it is possible to appropriately adjust damping force characteristics in order to improve ride comfort and steering stability in accordance with road surface conditions, running conditions and the like. There is a damping force adjustable hydraulic shock absorber.

Conventionally, as a damping force adjusting type hydraulic shock absorber,
A piston, to which a piston rod is connected, is slidably fitted in a cylinder in which oil liquid is sealed, one end of the piston rod is extended to the outside of the cylinder, and 2 It is known that the chamber is communicated with a main oil liquid passage provided in a piston portion and a bypass passage, and further a shutter mechanism is provided for switching the passage area of the bypass passage.

With this construction, the damping force characteristic (orifice characteristic) can be adjusted by operating the shutter mechanism to switch the passage area of the bypass passage.

Further, in order to make the damping force on the extension side and the damping force on the contraction side different, a check valve having an orifice which is always in communication in the bypass passage is provided.
No. 92537.

[0006]

However, in the conventional damping force adjusting type hydraulic shock absorber described above, since the oil liquid in the cylinder flows through the same bypass passage in both the expansion and contraction strokes of the piston rod, the passage of the bypass passage is not affected. By switching the area, the same damping force characteristics are switched on both the expansion side and the contraction side. Therefore, different types of damping force characteristics cannot be simultaneously selected for the extension side and the contraction side.

Further, even if a check valve is provided in the bypass passage, it is possible to obtain different damping force characteristics on the extension side and the contraction side, but the oil liquid extends and contracts both in the bypass passage. Because it flows through the same orifice inside,
When the damping force characteristic on the closing side of the check valve is determined, the damping force characteristic on the opening side of the check valve can always obtain only the damping force characteristic lower than the damping force characteristic on the closing side of the check valve. Therefore, the extension side damping force characteristic and the contraction side damping force characteristic cannot be freely set without affecting each other.

The present invention has been made in view of the above points, and is a damping force adjustment type which can freely set the extension side damping force characteristic and the contraction side damping force characteristic without affecting each other. An object is to provide a hydraulic shock absorber.

[0009]

The hydraulic shock absorber of the present invention comprises:
In order to solve the above problems, a cylinder in which an oil liquid is sealed, a piston rod having one end inserted into the cylinder and the other end protruding, and an oil field defining member that defines two chambers inside the cylinder And two communication passages provided in the oil boundary defining member that communicate the two chambers in the cylinder and allow the oil liquid to flow by the movement of the piston rod, and two communication passages provided in each of the two communication passages. It is characterized in that it is provided with a check valve that allows the oil liquid to flow in different directions and a shutter mechanism that adjusts the passage areas of the two communication passages.

[0010]

With this configuration, the two communication passages allow only the flow of the oil liquid in different directions by the check valve, so that the oil liquid in the cylinder flows through the different communication passages during the expansion stroke and the contraction stroke. Therefore, by adjusting the passage area of each communication passage with the shutter mechanism, different types of damping force characteristics can be selected simultaneously on the extension side and the contraction side.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

The hydraulic shock absorber 1 will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, a free piston 3 is slidably fitted in the cylinder 2, and the inside of the cylinder 2 is defined by a free piston 3 into a gas chamber 4 and an oil chamber 5. . The gas chamber 4 is filled with high-pressure gas, and the oil chamber 5 is filled with oil liquid.

A piston 6 as an oil field defining member is slidably fitted in the oil chamber 5, and the oil chamber 5 is provided with a piston 6.
It is divided into a lower chamber R ₁ and an upper chamber R ₂ . A piston rod 7 is connected to the piston 6, and the piston rod 7 extends to the outside of the cylinder 2 through the upper chamber R ₂ .

The piston 6 is provided with a first communication passage 8 and a second communication passage 9 which communicate the lower chamber R ₁ and the upper chamber R ₂ . In the upper part of the piston 6, when the pressure of the lower chamber R ₁ becomes high when the piston rod 7 is shortened and the pressure difference between the lower chamber R ₁ and the upper chamber R ₂ becomes a value, the first communication passage 8 is formed. A normally closed first damping valve 10 that is open is attached, while on the other hand, at the bottom of the piston 6, when the piston rod 7 extends, the pressure in the upper chamber R ₂ increases and the lower chamber R ₁ and the upper chamber R ₂ become When the pressure difference reaches a certain value, the second
A normally closed second damping valve 11 that opens the communication passage 9 is attached.

The piston 6 is formed with third and fourth communication passages 12 and 13 which are opposed to each other with the axis of the piston rod 7 interposed therebetween, and the third and fourth communication passages 12 and 13 are respectively formed. Superior room R ₂
Communicates with the lower chamber R ₁ . Third and fourth communication passages 12, 13
Check valves 14 and 15 are provided respectively, the check valve 14 allows only the flow of oil liquid from the lower chamber R ₁ to the upper chamber R ₂ , and the check valve 15 is from the upper chamber R ₂ to the lower chamber R _2. Only allow oil flow to ₁ .

A disk-shaped movable plate 16 is held inside the piston 6 so as to be rotatable about the axis of the piston rod 7, and the plate surface of the movable plate 16 has third and fourth communication passages 12. , 13 across. The movable plate 16 has a pair of concentric holes 1
7 and 18 are bored, and the pair of long holes 17 and 18 face each other. Each of the long holes 17 and 18 extends in the circumferential direction of the movable plate 16, and one of the long holes 17 has an opening area that increases in the clockwise direction in FIG.
The opening area of 18 is smaller as it goes clockwise in FIG. The movable plate 16 constitutes a shutter mechanism that adjusts the passage areas of the third and fourth communication passages 12 and 13. By rotating the movable plate 16 about its axis, a long hole is formed. The areas 17 and 18 face the third and fourth communication paths 12 and 13, and the area of the paths can be continuously changed. The damping force characteristic at this time is as shown in FIG.

Explaining this concretely, the third communication passage
For example, when the b ₁ point of the long hole 17 is faced to 12 and the b ₂ point of the long hole 18 is faced to the fourth communication passage 13, the rising as shown by B ₁ and B ₂ in FIG. In the case where the third communication passage 12 is faced with the a ₁ point of the long hole 17 and the fourth communication passage 13 is faced with the a ₂ point of the long hole 18, the characteristic curve B ₁ the characteristic curve a ₁ rising rapid than, the characteristic curve B ₂ shows the characteristic curve a ₂ rising gradual than to face the c ₁ point of the elongated hole 17 in the third communication path 12 of the fourth when to face the c ₂ points of the elongated hole 18 in the communication passage 13 of the rising gentle than the characteristic curve B ₁ characteristic curve C ₁
And a characteristic curve C ₂ that rises more rapidly than the characteristic curve B ₂ . Then, when each damping force at the initial rising exceeds a predetermined value, the first and second damping valves 10 and 11 are opened, and the hydraulic shock absorber 1 exhibits each predetermined damping force. The opening times of the first and second damping valves 10 and 11 correspond to the points P ₁ and P _{2 at} which the respective characteristic curves bend.

An operating rod 19 is connected to the movable plate 16 at its axial center, and the operating rod 19 rotatably penetrates the piston rod 7 in its axial direction. An actuator 20 is connected to the operation rod 19, and the actuator 20 allows the operation rod 19 to appropriately rotate about its axis.

With the above structure, the movable rod 16 is rotated by operating the operating rod 19 with the actuator 20 so that the point b ₁ of the elongated hole 17 faces the third communication passage 12 and the fourth communication passage 13 In long hole 18
B ₂ point, the medium characteristic that a moderate damping force (see characteristic curves B ₁ and B ₂ ) is generated on both the expansion side and the contraction side, and the a ₁ of the long hole 17 a _{1 is formed in} the third communication passage 12. When a point is faced and a point a ₂ of the long hole 18 is faced in the fourth communication passage 13, a soft characteristic that a small damping force (see characteristic curve A ₂ ) is generated on the extension side, and a large damping force (a characteristic is generated on the contraction side). (See characteristic curve A ₁ ). Also, the third communication passage 12 is made to face the point c ₁ of the long hole 17, and the fourth communication passage 13 is made to face the point c ₂ of the long hole 18. The expansion side has a hard characteristic that generates a large damping force (see the characteristic curve C ₂ ) and the contraction side has a soft characteristic that generates a small damping force (see the characteristic curve C ₁ ).

As described above, by adjusting the passage areas of the third communication passage 12 and the fourth communication passage 13, respectively, the extension side has a soft characteristic, the contraction side has a hard characteristic, the extension side has a hard characteristic and the contraction side has a soft characteristic. As described above, different types of damping force characteristics can be simultaneously selected on the extension side and the contraction side.

In place of the long holes 17 and 18 of this embodiment, the movable plate 16 is provided with a plurality of orifices having different opening areas which can face the third and fourth communication passages 12 and 13. The damping force characteristics may be switched by selecting.

Next, an example of a suspension system using the hydraulic shock absorber 1 will be described.

4 to 10, a vehicle 21 is connected to a vehicle body 22 and an axle 23 of the vehicle 21 via a suspension device 24, and wheels 25 are connected to the axle 23. Suspension
24 is provided for each wheel 25, and FIG. 1 shows its suspension system.
Shows one of the 24.

The suspension device 24 is roughly composed of a coil spring 26 as a spring, a hydraulic shock absorber 1 as a shock absorber, and a displacement sensor 27 as a detection means. The coil spring 26 has one end side inner side thereof fitted and held by a rubber cushion 28 provided on the axle 23,
Inside the other end of the coil spring 26 is a rubber cushion
It is fitted and held by a cushion receiver 29 provided on the side of the vehicle body 22 opposite to 28.

The displacement sensor 27 is interposed between the vehicle body 22 and the axle 23. The displacement sensor 27 is the distance between the vehicle body 22 and the axle 23 in the reference state, that is, the distance between the axle 23 and the reference length L. The displacement in the expansion / contraction direction of is detected. The reference length L is
The distance between the vehicle body 22 and the axle 23 may be set when the vehicle 21 is left stationary on a flat ground, or the vehicle 21 may be allowed to travel on a predetermined road surface for a predetermined time, and the distance between the vehicle body 22 and the axle 23 at that time. The average value of

Each displacement sensor 27a in each suspension device 24,
27b, 27c, 27d and the actuators 20a, 20b, 20c, 20d in the hydraulic dampers 1 of the suspension devices 24 are connected via a control circuit 30 as shown in FIG. The control circuit 30 has a function of controlling the corresponding actuators 20a to 20d based on the detection signals from the displacement sensors 27a to 27d. That is, the control circuit 30 determines the spring force F _s of the coil spring 26 based on the detection signal from the displacement sensor 27 (hereinafter, one of the displacement sensors and the actuator corresponding to the displacement sensor will be described). And the vehicle direction with respect to the reference length L
Temporal expansion change of the distance between the axle 23, i.e. to calculate the suspension velocity (piston speed), then by the suspension velocity based on the following equation to calculate the damping force F _a of the hydraulic shock absorber 1. F _a = K × gravitational acceleration × piston speed (Kg · m / sec ² ) K = coefficient

Then, the control circuit 30 compares the acting direction of the spring force F _{s with} the acting direction of the damping force F _a . Where the spring force
When the axial length of the coil spring 26 is shorter than the reference length L, the acting direction of F _s is a direction in which the coil spring 26 extends, and the coil spring 26 is longer than the reference length L.
When the axial length of the coil spring is long, the coil spring 26
It becomes the direction of shrinking. Further, the acting direction of the damping force F _a is the direction in which the piston rod 16 is shortened when the piston rod 16 is extended, and the piston rod 16 is shortened when the piston rod 16 is shortened.
16 extension directions.

The control circuit 30 controls the action direction of the spring force F _s and the damping force.
When it is determined that they are the same by comparing the action direction of F _a, the control circuit 30 operates the actuator 20 to rotate the movable plate 16 so that the damping force F _a is not generated. The predetermined position of the predetermined long hole 17 or 18 is made to face the third communication passage 12 or the fourth communication passage 13. When the control circuit 30 compares the acting direction of the spring force F _{s and} the acting direction of the damping force F _a and determines that they are in conflict, the control circuit 30 actuates the actuator 20 to rotate the movable plate 16. A predetermined long hole 17 so that the magnitude of the damping force F _a becomes equal to the magnitude of the spring force F _s.
Alternatively, 18 predetermined positions are exposed to the third communication passage 12 or the fourth communication passage 13. The details will be described later.

Next, the operation of the above configuration will be described by taking as an example the case where the vehicle 21 travels on the convex portion 31a on the road surface 31 as shown in FIG.

In the calculation, the suspension device 24 is modeled as shown in FIG. 7, and in this model, the body mass M = 300 Kg, the spring constant of the coil spring 26, k = 1207 × gravitational acceleration (Kgm / sec ² m) and three types of hydraulic shock absorbers whose damping force F _a is obtained by the following equation are used. _{(a) F a = K a} × gravitational acceleration × piston speed (Kgm / se
c ² ) K _a ＝ −20 (b) F _a ＝ K _b × gravitational acceleration × piston speed (Kgm / se
c ² ) K _b ＝ −200 (c) F _a ＝ K _c × gravitational acceleration × piston speed (Kgm / se
c ² ) K _c = −20 to −300 (a) is when the damping force F _a is almost zero, and (b) is
In the case of the conventional suspension device, (c) shows the range that the damping force F _a can take in the case of the suspension device according to the present invention.

The vertical acceleration α of the vehicle body 22 is calculated by the following equation based on the above relationship. α = (F _a + F _s ) / M For this result, the types of the above hydraulic shock absorbers (a), (b)
, (C) are shown in FIGS. 8, 9 and 10.

Below, four sections A, B, and
A description will be given based on C and D.

(I) Section A When the vehicle 21 rides on the convex portion 31a of the road surface 31, both the coil spring 26 and the hydraulic shock absorber 1 are contracted.
In, the spring force F _s is generated in the coil spring 26, and the damping force F _a is generated in the hydraulic shock absorber 1. At this time, the spring force F _s
7 also acts on the damping force F _a in the upward direction in FIG. 7, the vertical acceleration α of the vehicle body 22 is obtained based on the sum of the damping force F _{a and} the vertical acceleration α of the vehicle body 22 in FIG. It becomes larger than the vertical acceleration α of the vehicle body 22.

On the other hand, in FIG. 10, a coil spring is used.
When 26 and the piston rod 7 of the hydraulic shock absorber 1 start to contract,
Point c1 of the long hole 17 faces the third communication passage 12, and the fourth communication passage 12
The point c2 of the long hole 27 faces 13. Therefore, the hydraulic shock absorber 1
At the time of shortening the piston rod 7, extremely damping force
As F _a becomes smaller (C _{1 in} FIG. 3), the fluctuation of the vehicle body 22 is mostly controlled by the spring force F _s . Therefore, the vertical acceleration α of the vehicle body 22 is determined based on the spring force F _s , and its value is substantially equal to that in the case of FIG.

(II) Section B When the vehicle 21 reaches the boundary between the section A and the section B, the distance between the vehicle body 22 and the axle 23 starts to be restored, and the coil spring 26 is also the piston of the hydraulic shock absorber 1. The rod 7 will also be extended. At this time, the coil spring 26 has a reference length L.
Since the spring force F _s is shorter than the above, the spring force F _s acts upward in the drawing, and in the hydraulic shock absorber 1, as the piston rod 7 extends, the damping force F _a is
In the figure, it acts downward. in this way,
Since the directions of the spring force F _s and the damping force F _a are opposite,
In the case of FIG. 10, the spring force F _s and the damping force F _a try to cancel each other out.

[0036] However, in the case of FIG. 9, since the damping force F _a have completely negate the purpose of the spring force F _s is not set, the sum of the spring force F _s and the damping force F _a increases, the vehicle body twenty two
The vertical acceleration α of becomes larger gradually.

On the other hand, in the case of FIG. 10, in the section A, the point c ₂ of the elongated hole 18 faces the fourth communication passage 13 when the piston rod 7 is extended at this time. The damping force F _a becomes extremely large (C _{2 in} FIG. 3). The damping force F _a is adjusted to be substantially equal to the spring force F _s in Section B, the spring force in order to equalize the damping force F _a to the spring force F _s
The movable plate 16 slightly rotates clockwise in FIG. 2 in response to a change in F _s . Therefore, the total sum of the spring force F _s and the damping force F _a cancels each other out because the respective directions are opposite to each other, and the vertical acceleration α of the vehicle body 22 becomes substantially zero.

(III) Regarding Section C At the boundary between Section B and Section C, the distance between the vehicle body 22 and the axle 23 becomes the reference length L, but when entering Section C, the coil spring 26 also the hydraulic shock absorber 1 The piston rod 7 will also be extended. At this time, in the case of FIG. 9, since the coil spring 26 is longer than the reference length L,
The spring force F _s acts downward in the figure, and since the piston rod 7 extends in the hydraulic shock absorber 1, the damping force F _a acts downward in the figure. It will be. Therefore, the sum of the both F _s and F _a increases, the vertical acceleration α of the vehicle body 22, is larger than that in the case of FIG. 8.

On the other hand, in the case of FIG. 10, when the coil spring 26 and the piston rod 7 of the hydraulic shock absorber 1 start to expand, the movable plate 16 rotates to form the elongated hole 18 in the fourth communication passage 13. a ₂
The point faces, and the point a ₁ of the long hole 17 faces the third communication passage 12. Therefore, in the hydraulic shock absorber 1 is very damping force F _a during extension of the piston rod 7 is reduced, (3
Middle, A ₂ ), fluctuations of the car body 22 are mostly dominated by the spring force F _s . Therefore, the vertical acceleration α of the vehicle body 22 is the spring force F _s.
The value is substantially equal to that in the case of FIG. 8 and smaller than that in the case of FIG.

(IV) Section D When section D is entered from section C, the distance between the vehicle body 22 and the axle 23 starts to be restored, and the coil spring 26 and the piston rod 7 of the hydraulic shock absorber 1 contract. Become. At this time, since the coil spring 26 is longer than the reference length L, its spring force F _s acts downward in the drawing, and the piston rod 7 in the hydraulic shock absorber 1 shortens. Accordingly, the damping force F _a acts upward in the figure. Thus, the spring force F _s and the damping force F _a
Since the directions of and are opposite to each other, in the cases of FIGS. 9 and 10, the spring force F _s and the damping force F _a try to cancel each other out.

[0041] However, in the case of FIG. 9, since the damping force F _a have completely negate the purpose of the spring force F _s is not set, the sum of the spring force F _s and the damping force F _a increases, the vehicle body twenty two
The vertical acceleration α of becomes large.

On the other hand, in the case of FIG. 10, the point a ₁ of the elongated hole 17 faces the third communication passage 12 when the section A has already been reached, and when the piston rod 7 is shortened at this time. The damping force F _a becomes extremely large (A _{1 in} FIG. 3). The damping force F _a is adjusted to be substantially equal to the spring force F _s in the interval D, the spring force in order to equalize the damping force F _a to the spring force F _s
The movable plate 16 slightly rotates counterclockwise in FIG. 2 in response to the change in F _s . Therefore, the total sum of the spring force F _s and the damping force F _a cancels each other out because the respective directions are opposite to each other, and the vertical acceleration α of the vehicle body 22 becomes substantially zero.

As described above, the vertical acceleration α of the vehicle body 22 is made extremely small with the sections A to D as one cycle, and the vertical acceleration α prevents the occupant from feeling uncomfortable.

Although one embodiment has been described above, the following modes are also possible.

In order to detect the spring force F _s , the mounting portion of the coil spring 26 or the strain of the spring itself may be detected.

To detect the piston speed (suspension speed), the speed itself may be directly detected.

Feedback control such that the vertical acceleration α of the vehicle body 22 is detected by using the acceleration sensor utilizing the inertial force of the weight and the damping force F _a of the hydraulic shock absorber 1 is controlled according to the detected state. You may do it.

The vertical acceleration α of the vehicle body 22 may be detected by detecting strain or the like at the mounting portion of the hydraulic shock absorber 1.

The spring may be a leaf spring having a damping action, an air spring or the like.

[0050]

As described above in detail, in the hydraulic shock absorber of the present invention, the oil liquid in the cylinder flows through the different communication passages during the expansion stroke and the contraction stroke, so that the damping on the extension side is performed. It is possible to freely set the force characteristics and the damping force characteristics on the contraction side without affecting each other, and by adjusting the passage area of each communication passage with the shutter mechanism, different types on the extension side and the contraction side can be set. The damping force characteristics can be selected at the same time. As a result, different types of damping force characteristics can be freely selected on the extension side and the contraction side, such as the soft side on the extension side and the hard characteristic on the contraction side, the hard characteristic on the extension side, and the soft side on the contraction side. It has an excellent effect that the selection range of can be expanded.

[Brief description of drawings]

FIG. 1 is a front vertical sectional view of an embodiment of the present invention.

FIG. 2 is a plan view of a movable plate which constitutes a shutter mechanism of the apparatus shown in FIG.

FIG. 3 is a diagram showing damping force characteristics of the device of FIG.

FIG. 4 is an explanatory view showing a suspension system of a vehicle equipped with the hydraulic shock absorber of FIG.

5 is a control system diagram of the apparatus of FIG.

6 is an explanatory diagram showing a traveling state of the vehicle in FIG. 4. FIG.

FIG. 7 is a schematic view showing a coil spring, a hydraulic shock absorber, and a vehicle body mass.

FIG. 8 is a diagram showing characteristics of a suspension system of a vehicle when it depends on a coil spring.

FIG. 9 is a diagram showing characteristics of a conventional vehicle suspension system using a coil spring and a hydraulic shock absorber.

FIG. 10 is a diagram showing characteristics of the suspension device of FIG. 4;

[Explanation of symbols]

1 Hydraulic shock absorber 2 Cylinder 6 Piston (oil field defining member) 7 Piston rod 12 Third communication passage (communication passage) 13 Fourth communication passage (communication passage) 14,15 Check valve 16 Movable plate (shutter mechanism) 29 Actuator R ₁ Lower chamber R ₂ Upper chamber

Claims (4)

[Claims] 1. A cylinder in which an oil liquid is sealed, a piston rod having one end inserted into the cylinder and a protrusion at the other end, an oil boundary defining member defining two chambers in the cylinder, and the oil. Two communication passages that are provided in the boundary defining member to communicate the two chambers in the cylinder, and in which the movement of the piston rod allows the oil liquid to flow, and oils in different directions provided in each of the two communication passages. A hydraulic shock absorber, comprising: a check valve that allows liquid to flow, and a shutter mechanism that adjusts the passage areas of the two communication passages. 2. The hydraulic shock absorber according to claim 1, wherein the shutter mechanism includes one shutter that adjusts both passage areas of the two communication passages and one actuator that controls the shutter. 3. The shutter mechanism, wherein when one of the two communication passages has a large passage area, the other communication passage has a small passage area, and when one of the communication passages has a small passage area, the other communication passage has a large passage area. The hydraulic shock absorber according to claim 1 or 2. 4. The hydraulic shock absorber according to claim 1, wherein the passage area of the communication passage is continuously adjustable.