JPH09177864A - Hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably generate a damping force by effectively suppressing the excessive increase of a damping force in a region where a piston speed is extremely high. SOLUTION: When a piston speed is 1.0m/s or more, oil liquid is caused to flow through a bypass passage 11 and a generating damping force is reduced in such a way that a bypass passage 11 and a spring valve 12 to cut off the bypass passage 11 when a piston speed is 1.0 or less and communicate the bypass passage 11 when a piston speed exceeds 1.0m/s or more are arranged in a piston rod 6.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, a hydraulic shock absorber mounted on a suspension system of an automobile is a cylinder defined by a piston in which a piston rod is connected slidably fitted in a cylinder filled with oil liquid. The two inner chambers are communicated with each other by a main oil liquid passage, and a damping force generating mechanism including an orifice and a disc valve arranged in series in the main oil liquid passage is provided. In this hydraulic shock absorber, the damping force generating mechanism consisting of an orifice and a disc valve controls the damping force by controlling the flow of the oil liquid generated in the main oil liquid passage due to the sliding of the piston in the cylinder accompanying the expansion and contraction of the piston rod. Generate.

Now, the damping force characteristic of the conventional hydraulic shock absorber will be described with reference to the damping force diagram of FIG. For example,
In an area where the piston speed is low (an area below vA in FIG. 3) such as a change in vehicle attitude such as a roll that occurs during turning,
A damping force is generated by the orifice, and the damping force characteristic is set so as to have a characteristic (orifice characteristic) in which the damping force increases in a quadratic curve as the piston speed increases. In addition, a region where the piston speed is large, such as when passing over unevenness of the road surface (region of vA to vB 'in Fig. 3)
Then, the disc valve opens and the flow passage area of the oil liquid is expanded to generate a damping force, and the damping force characteristic becomes a characteristic (valve characteristic) in which the damping force linearly increases as the piston speed increases. Is set.

The orifice characteristic is set by the area of the orifice, and the valve characteristic is set by the spring constant of the disc valve and the passage area of the main oil liquid passage. By setting the orifice characteristic and the valve characteristic to desired characteristics for each vehicle type, the steering stability and riding comfort of the vehicle are improved.

However, in the conventional hydraulic shock absorber having the orifice and the disc valve, the piston speed is extremely high when the vehicle passes through a large step or a depression (the area of vB 'or more in FIG. 3). Then, since the disc valve is fully opened and the main oil liquid passage acts as an orifice, the damping force generated as the piston speed increases increases in a quadratic curve. For this reason,
When the piston speed is extremely high (in the range of vB or more in FIG. 3), there is a problem that the damping force becomes too large and the shock absorber hardly expands or contracts, and the shock is transmitted to the vehicle body to impair the ride comfort of the occupant.

In order to solve such a problem, there is a hydraulic shock absorber disclosed in JP-A-55-27552. In the hydraulic shock absorber, a piston having a main oil liquid passage having a large passage area is connected to a piston rod, and the piston has an annular member having a through hole smaller than the passage area of the main oil liquid passage. , And a disk valve for closing the through hole are assembled in order.

With such a configuration, the piston speed is v
In the region A or above, the flow path of the oil liquid is secured by bending the disc valve through the main oil liquid passage and the through hole. When the piston speed is equal to or higher than vB, the flow path resistance of the through hole becomes large, and the annular member in addition to the disc valve bends, so that a large passage area of the oil liquid is secured and an excessive damping force is generated. Is being prevented.

[0008]

However, in the hydraulic shock absorber as disclosed in Japanese Patent Laid-Open No. 55-27552, the main oil liquid passage is formed in the piston, so that a large passage area can be secured. However, since the main oil liquid passage acts as an orifice in the end, the damping force cannot be reduced sufficiently.

Further, since the annular member and the disc valve are assembled adjacently to each other, friction occurs when they are bent, and due to this effect, the damping force varies and the desired damping force is obtained. There is a problem that it cannot be obtained. In addition, there is a possibility that a wrong assembly may occur when the piston is assembled to the piston.

Therefore, a structure in which the piston portion is processed and the damping force is reduced when the piston speed is high by using a disc valve or the like is not desirable.

The present invention has been made in view of the above points, and can effectively suppress an excessive increase of the damping force in a region where the piston speed is very high, and stably generate the damping force. An object of the present invention is to provide a hydraulic shock absorber that can be used.

[0012]

In order to solve the above problems, a hydraulic shock absorber according to the present invention includes a cylinder in which an oil liquid is sealed, and a cylinder slidably fitted in the cylinder. A piston defining an inner space into two chambers, a piston rod having one end penetrating and connecting the piston and the other end extending to the outside of the cylinder, and a main oil liquid for communicating the two chambers in the cylinder. A hydraulic shock absorber comprising a passage and a damping force generating mechanism for controlling a flow of the oil liquid in the main oil liquid passage to generate a damping force, the cylinder being bored in the piston rod in the axial direction, A bypass passage communicating the two chambers therein, a small diameter portion provided in the bypass passage, large diameter portions provided on both sides of the small diameter portion, and a bypass passage movably provided in the bypass passage. , When it is fitted in the small diameter portion, A valve body for communicating the bypass passage when the bypass passage is cut off, moved to the large diameter portion,
When the moving speed of the piston is less than a predetermined value, the valve body is held in the small diameter portion, and when the moving speed of the piston is a predetermined value or more, the valve element is located on the side of the large diameter portion where the pressure of the oil liquid is low. At least one spring that allows movement in the large diameter portion is provided.

With the above structure, when the piston speed is higher than a predetermined value, the valve element in the bypass passage moves to the large diameter portion to communicate with the bypass passage, thereby promoting the flow of the oil liquid. To reduce the damping force.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below in detail with reference to the drawings. 1 and 2, the right side shows the state during the expansion stroke of the piston rod, and the left side shows the state during the contraction stroke.

As shown in FIG. 1, in a hydraulic shock absorber 1 according to this embodiment, a piston 3 is slidably fitted in a cylinder 2 in which an oil liquid is sealed.
The inside of the cylinder 2 is divided into two chambers, a cylinder upper chamber 4 and a cylinder lower chamber 5. The piston 3 has one end of a piston rod 6 penetratingly connected thereto, and the other end of the piston rod 6 has a rod guide and an oil seal (both not shown) attached to an end portion of the cylinder 2 inserted therethrough. Is extended to the outside of the cylinder 2. The piston rod 6 is composed of a rod portion 6a that slides on the rod guide and a connecting portion 6b that connects the piston 3 therethrough. Inside the piston rod 6, a bypass passage 11 and a spring valve 12 described later are provided. .

An outer cylinder (not shown) is provided on the outer circumference of the cylinder 2, and a reservoir chamber (not shown) is formed between the cylinder 2 and the outer cylinder. Are communicated with each other through a base valve (not shown) provided at the bottom of the cylinder 2 with an appropriate flow resistance. The reservoir chamber is filled with oil liquid and gas, and the volume change in the cylinder 2 due to the intrusion and retreat of the piston rod 6 is compensated by the compression and expansion of the gas.

The piston 3 is slidably fitted in the cylinder 2, and the piston 2 has a first chamber 4 and a lower chamber 5 which communicate with each other.
The communication passage 7 and the second communication passage 8 are provided. First
The communication passage 7 and the second communication passage 8 do not intersect with each other, and the first communication passage 7 and the second communication passage 8 form a main oil liquid passage.

Disc valves 9 and 10 are provided on the upper chamber 4 side and the lower chamber 5 side of the piston 3, respectively, and a notch is provided on the outer peripheral portion between the disc valves 9 and 10 and the piston 3. Thin disks 9a, 10a are provided which form the orifices 9b, 10b. The disk valves 9 and 10 and the orifice 9
b and 10b constitute a damping force generating mechanism.

The bypass passage 11 has an opening 11b opening to the upper chamber 4, an opening 11c opening to the lower chamber 5, and an axial bore in the piston rod 6 to form the opening 11b and the opening 11c. And a communication portion 11d that communicates with each other. The communication portion 11d is provided with a small diameter portion 11a and large diameter portions 11e and 11f located on both sides of the small diameter portion 11a.

The spherical valve body 12a is movably fitted in the small diameter portion 11a, and its diameter is made substantially equal to the inner diameter of the small diameter portion 11a. In addition, the valve body 12a includes a small-diameter portion 11 due to the upper chamber side spring 12b and the lower chamber side spring 12c.
It is held in a. The valve body 12a is the small diameter portion 1
When fitted in 1a, the bypass passage 11 is blocked so that the oil liquid does not flow. Further, when the valve body 12a is moved to the large diameter portions 11e and 11f, the bypass passage 11 is communicated with each other, allowing the oil liquid to flow.

The spring valve 12 comprises a valve body 12a, an upper chamber side spring 12b, a lower chamber side spring 12c and a small diameter portion 11a. The valve opening pressure during the compression stroke of the spring valve 12 (the pressure difference between the lower chamber 5 and the upper chamber 4 when the valve body 12a moves to the large diameter portion 11e) is larger than the valve opening pressure of the disc valve 9, Valve opening pressure during extension stroke (upper chamber 4 and lower chamber 5 when the valve body 12a moves to the large diameter portion 11f)
Pressure difference) is set to be larger than the valve opening pressure of the disc valve 10.

Here, in general, the piston speed does not exceed 0.9 m / s during normal traveling in a passenger car, so that the desired damping force can be obtained up to 1.0 m / s due to the characteristics of the disc valve. It has become. However, 1.0
Since the damping force becomes excessively larger than the desired damping force at m / s or more, the pressure difference generated between the upper chamber 4 and the lower chamber 5 at 1.0 m / s (predetermined moving speed) is used here. The spring valve 12 was set to open.

Next, the operation of the present embodiment configured as described above will be described with reference to FIG. When the vehicle turns and rolls, and the posture of the vehicle changes,
In a small region where the piston speed of the hydraulic shock absorber 1 is 0.15 m / s or less (region of vo to vA in FIG. 3), as shown in FIG. The first flow A ₁ flowing into the lower chamber 5 side through the first communication passage 7 and the orifice 10b, and the first flow A ₁ flowing into the lower chamber 5 side through the second communication passage 8 through the orifice 9b. Two streams B ₁ and ₁ occur. At this time, a damping force having an orifice characteristic is generated by the orifices 10b and 9b, and the damping force changes in a quadratic curve according to the piston speed, as indicated by O-A in FIG.

Similarly, during the contraction stroke, the oil liquid on the lower chamber side 5 passes through the second communication passage 8 and the orifice 9b to the upper chamber 4.
A first flow A ₂ flowing into the side of the upper chamber 4 and a second flow B ₂ flowing into the side of the upper chamber 4 through the first communication passage 7 via the orifice 10b are generated. At this time, a damping force having an orifice characteristic is generated by the orifices 9b and 10b, and the damping force is as shown in FIG.
Like the middle O-D, it changes like a quadratic curve according to the piston speed.

Further, when the vehicle is traveling on a bumpy road surface, the piston speed of the hydraulic shock absorber 1 is 0.15 to 0.15.
In an area as large as 0.7 m / s (area from vA to vB ′ in FIG. 3), the disk valve 10 opens due to the pressure increase on the upper chamber 4 side during the extension stroke, and the first flow A ₁ is 1 through the communication passage 7 and the flow through the disc valve 10,
The damping force of the valve characteristic is generated. At this time, the disc valve 10 is in a state where it is not fully opened, and the damping force changes linearly according to the piston speed as indicated by AB ′ in FIG.

Similarly, in the compression stroke, the disc valve 9 opens due to the pressure increase on the lower chamber 5 side, and the first flow A ₂ flows through the second communication passage 8 and the disc valve 9. , The damping force of the valve characteristic is generated. At this time, the disc valve 9 is in a state where it is not fully opened, and the damping force changes linearly according to the piston speed as indicated by D-E 'in FIG.

Next, in a region where the piston speed of the hydraulic shock absorber 1 is extremely high (a region of vB 'or more in FIG. 3), such as when the vehicle passes through a large gap or a depression during traveling, during the extension stroke. Then, the flow rate of the oil liquid is such that the piston speed is vA to vB '.
However, the disc valve 10 is fully opened, the first communication passage 7 acts as an orifice, and the damping force is a quadratic curve according to the piston speed as shown by B'-C '. Changes to.

Similarly, during the compression stroke, the disc valve 9
Is fully opened, the second communication passage 8 acts as an orifice, and the damping force changes in a quadratic curve according to the piston speed as indicated by E'-F '.

However, when the piston speed exceeds the predetermined moving speed of 1.0 m / s (vB in FIG. 3), the pressure on the cylinder upper chamber 4 side causes The valve body 12a in the bypass passage 11 is pushed to the lower chamber 5 side to move from the small diameter portion 11a to the large diameter portion 11f, the bypass passage 11 is communicated, and the oil liquid on the upper chamber 4 side flows into the lower chamber 5 side. A third flow C ₁ is generated. The damping force at this time is as shown by B-C in FIG. 3, and the damping force is cut (reduced) as compared with B-C '.

Similarly, during the compression stroke, as shown on the left side of FIG. 2, the pressure on the cylinder lower chamber 5 side rises, and this pressure pushes the valve body 12a in the bypass passage 11 to the upper chamber 4 side. A third flow C ₂ that moves from the small-diameter portion 11a to the large-diameter portion 11e, the bypass passage 11 is communicated, and the oil liquid on the lower chamber 5 side flows into the upper chamber 4 side is generated. The damping force at this time becomes like EF in FIG. 3, and the damping force is cut as compared with EF ′.

As described above, when the piston speed is equal to or higher than vB, the spring valve 12 is opened to allow the oil liquid on the high pressure chamber side to escape to the low pressure chamber side via the bypass passage 11, so that the damping force becomes excessive. It is possible to suppress the rise of the vehicle, prevent the shock from propagating to the vehicle without expanding and contracting the shock absorber when the vehicle passes through a large step or depression of the road surface, and improve the riding comfort of the vehicle.

Further, since the bypass passage 11 is provided inside the piston rod 6, the processing is easy. Further, since a large passage can be provided, the damping force can be sufficiently cut even when the piston speed becomes extremely high.

Further, since the valve body 12a is movable in the vertical direction, it is possible to connect the bypass passage 11 in the expansion stroke and the compression stroke with one valve, and therefore it is necessary to provide a plurality of bypass passages and valves. Absent. Also,
Since the extension process and the contraction process are used in common, the number of parts can be reduced, and the risk of misassembly or the like can be reduced.

In this embodiment, since the valve body 12a has a spherical shape, it can be fitted into the small diameter portion 11a smoothly, and if the communicating portion 11d of the bypass passage 11 is formed into a circular tube shape in accordance with the valve body 12a. Since it is good, the piston rod 6 can be easily processed.

Although it is desirable that the valve body 12a is spherical as described above, the bypass passage 11 is blocked when it is fitted into the small diameter portion 11a, and is bypassed when it is moved to the large diameter portions 11e and 11f. May be communicated with each other, and may be a column or a cone. In this case, the bypass passage may be processed according to the shape of the valve body.

It is also possible to improve the cut-off property of the bypass passage by forming the valve body as a column and covering the contact portion with the small diameter portion with a sealing material or the like.

Further, when the valve body 12a is fitted in the small diameter portion 11a, a slight clearance may be positively provided to interrupt the communication of the bypass passage 11,
In this case, the clearance portions are the orifices 9b, 1
Acts as a substitute for 0b.

Further, the spring valve 12 may be either the upper chamber side spring 12b or the lower chamber side spring 12c. When only the upper chamber side spring 12b is used, the upper end of the bypass passage (11g in FIG. 1) is used. One end of the upper chamber side spring 12b is fixed and the other end is fixed to the valve body 12a.
Fixed to At this time, the upper chamber side spring 12b is retained by fitting the valve body 12a into the small diameter portion 11a when the upper chamber side spring 1b is in its natural length, and when the hydraulic shock absorber 1 is in the extension stroke.
2b extends so that the valve body 12a moves from the small diameter portion 11a to the large diameter portion 11
In the contraction stroke, the upper chamber side spring 12b contracts and the valve element 12a moves from the small diameter portion 11a to the large diameter portion 11e.

Similarly, when only the lower chamber side spring 12c is used, one end of the lower chamber side spring 12c is fixed to the nut 6c and the other end is fixed to the valve body 12a. At this time, when the lower chamber side spring 12c has a natural length, the valve body 12a is retained by being fitted into the small diameter portion 11a, and during the extension stroke of the hydraulic shock absorber 1, the lower chamber side spring 12b contracts and the valve body 12a.
Moves from the small-diameter portion 11a to the large-diameter portion 11f, and the lower chamber side spring 12c extends during the contraction stroke to move the valve body 12a from the small-diameter portion 11a to the large-diameter portion 11e.

In the above embodiment, the damping force at which the predetermined moving speed of the piston starts to change greatly is 1.0 m.
However, the present invention is not limited to this, and when the hydraulic shock absorber of the present invention is used in a passenger car, the piston speed is 0.9 m / s or more in normal traveling, and the piston speed is too large. You can set it to.

[0042]

As described above, the hydraulic shock absorber of the present invention is
A bypass passage that connects two chambers in the cylinder to the piston rod and has a small diameter portion and large diameter portions located on both sides thereof; a valve body provided in the bypass passage; and a valve body in the small diameter portion of the bypass passage. By providing a spring to hold,
When the piston speed becomes equal to or higher than a predetermined value, the valve body moves from the small diameter portion in the bypass passage to the large diameter portion to communicate the two chambers in the cylinder via the bypass passage, and to promote the flow of the oil liquid, Suppresses excessive increase in damping force. As a result, the shock absorber does not expand or contract when the vehicle passes through a large step or depression on the road surface, and the impact is prevented from propagating to the vehicle, and the riding comfort of the vehicle can be improved.

Further, in the hydraulic shock absorber of the present invention, since the bypass passage is provided in the piston rod, a large passage can be provided and the increase of damping force can be sufficiently suppressed.

Further, since a bypass passage and a valve body are provided in the piston rod, a stable damping force can be obtained, unlike the one in which the piston portion is processed to reduce the damping force. Since it is movable, the bypass passages for the expansion stroke and the contraction stroke can be communicated with each other by using one valve, so that it is not necessary to provide a plurality of bypass passages and valves. For this reason, the number of parts is small, and the risk of incorrect assembly is reduced.

[0045]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing a normal operating state of a hydraulic shock absorber 1 according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an essential part showing an operating state in the apparatus of FIG. 1 when the piston speed is very high (1.0 m / s or more).

FIG. 3 shows respective damping force diagrams of the conventional hydraulic shock absorber and the hydraulic shock absorber 1 according to the embodiment of the present invention.

[Explanation of symbols]

A ₁ first flow A ₂ extension stroke the second stream B ₁ second flow of the first stream C ₁ contraction during stroke when the third flow B ₂ compression stroke of the elongation stroke at the time of the extension stroke C ₂ Third flow during compression stroke 1 Hydraulic shock absorber 2 Cylinder 3 Piston 4 Upper chamber 5 Lower chamber 6 Piston rod 6a Rod part 6b Connecting part 6c Nut 7 First communication passage (main oil liquid passage) 8 Second Communication passage (main oil liquid passage) 9 disk valve (damping force generating mechanism) 9a disk 9b orifice (damping force generating mechanism) 10 disk valve (damping force generating mechanism) 10a disk 10b orifice (damping force generating mechanism) 11 bypass passage 11a small diameter portion 11b opening portion 11c opening portion 11d communication portion 11e large diameter portion 11f large diameter portion 11g bypass passage upper end portion 12 spring valve 12a valve body 12b upper chamber side spring (spring) 12c Lower chamber side spring (spring)

Claims (1)

[Claims] 1. A cylinder in which an oil liquid is sealed, and a cylinder slidably fitted in the cylinder so that the inside of the cylinder is 2
A piston defining a chamber, a piston rod having one end penetrating and connecting the piston and the other end extending to the outside of the cylinder, and a main oil liquid passage communicating two chambers in the cylinder, A hydraulic shock absorber comprising: a damping force generating mechanism that controls a flow of the oil liquid in the main oil liquid passage to generate a damping force. A bypass passage communicating with the chamber; a small diameter portion provided in the bypass passage; large diameter portions provided on both sides of the small diameter portion; and a small diameter portion provided in the bypass passage so as to be movable in the axial direction. A valve body that blocks the bypass passage when fitted into a portion, and communicates the bypass passage when moving to the large diameter portion, and the valve body to the small diameter portion when the moving speed of the piston is less than a predetermined value. Retention And at least one spring that allows the valve element to move to a large diameter portion of the large diameter portion on the side where the pressure of the oil liquid is low when the moving speed of the piston is equal to or higher than a predetermined value. Hydraulic shock absorber.