JPH04296234A - Hydraulic shock absorber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 used in a suspension system for a vehicle such as an automobile, which adjusts damping force in accordance with vertical acceleration.

0002

[Prior Art] As a general hydraulic shock absorber, for example, FIG.
There is a double cylinder structure as shown in the figure. This hydraulic shock absorber will be explained based on the drawings.

In FIG. 9, a piston 5 to which a rod 4 is connected is slidably fitted into the inner cylinder 1 of a cylinder 3 having a double cylinder structure consisting of an inner cylinder 1 and an outer cylinder 2. Inside the inner cylinder 1 is a cylinder upper chamber 3a and a cylinder lower chamber 3b.
It is defined as A reservoir chamber 3 that communicates with the cylinder lower chamber 3b at the lower end of the cylinder 3 between the inner cylinder 1 and the outer cylinder 2
The cylinder upper chamber 3a and the lower cylinder chamber 3b are filled with oil, and the reservoir chamber 3c is filled with oil and gas. The piston 5 includes a damping force generation mechanism 6 consisting of an orifice and a disc valve that generates a damping force during the extension stroke, and a cylinder lower chamber 3 during the contraction stroke.
A check valve mechanism 7 is provided that allows oil fluid to flow from b to the cylinder upper chamber 3a.

A base valve mechanism 8 is provided on the bottom side of the cylinder 3 to communicate the cylinder lower chamber 3b and the reservoir chamber 3c. A damping force generating mechanism 9 is provided, and a check valve mechanism 10 that allows oil fluid to flow from the reservoir chamber 3c to the cylinder lower chamber 3b during the extension stroke is provided. The tip of the rod 4 is connected to the vehicle body side, and the attachment eye 11 provided at the lower end of the cylinder 3 is connected to the wheel side. In the figure, 12a is a rod guide, and 12b is a dust seal.

With this configuration, during the extension stroke, the rod 4
As the piston 5 slides as the piston 5 moves, the oil in the cylinder upper chamber 3a flows into the cylinder lower chamber 3b, and the damping force generating mechanism 6 generates a damping force. At this time, the amount of oil that the rod 4 has withdrawn from the inner cylinder 1 passes through the check valve mechanism 10 of the base valve mechanism 8 and flows into the cylinder lower chamber 3b from the reservoir chamber 3c.

During the retraction stroke, as the piston 5 moves with the movement of the rod 4, the oil in the lower cylinder chamber 3b flows into the upper cylinder chamber 3a through the check valve mechanism 7. Furthermore, the amount of oil that the rod 4 has entered into the cylinder upper chamber 3a flows from the cylinder lower chamber 3b through the base valve mechanism 8 to the reservoir chamber 3c. At this time, the damping force generation mechanism 9
A damping force is generated.

In this manner, the damping force is generated by the damping force generating mechanism 6 of the piston 5 during the extension stroke, and by the damping force generating mechanism 9 of the base valve mechanism 8 during the retracting stroke.

When the piston speed is low, the orifice exhibits a damping force characteristic (orifice characteristic) in which the damping force changes quadratically according to the piston speed, and when the piston speed exceeds a predetermined value, the piston speed is reduced by the disk valve. This shows the damping force characteristics (valve characteristics) in which the damping force changes linearly according to the That is, the damping force characteristics change depending on the piston speed.

[0009] By the way, in response to unsprung vibrations that have relatively large accelerations and frequencies caused by uneven road surfaces while the vehicle is running, it is possible to improve ride comfort by reducing the damping force of the hydraulic shock absorber. Can be done. In addition, the damping force of the hydraulic shock absorber is increased to suppress changes in the posture of the vehicle body against sprung vibrations that occur due to the inertia of the vehicle body when the vehicle starts, brakes, or turns, and whose acceleration and frequency are relatively small. This can improve steering stability.

[0010] Therefore, in order to improve the ride comfort and handling stability of a vehicle, various hydraulic shock absorbers have been proposed in which the damping force characteristics change according to expansion/contraction acceleration or vibration frequency as shown below.

Japanese Patent Laid-Open No. 62-106138 discloses that a part of the oil that generates the damping force is introduced into the volume chamber through an orifice passage, and the oil that flows through the damping force generation mechanism according to the input frequency is introduced. A hydraulic shock absorber is disclosed in which damping force characteristics are made frequency dependent by adjusting the flow rate of liquid.

[0012] Furthermore, in Japanese Utility Model Application Publication No. 62-838 and Japanese Utility Model Application Publication No. 62-46039, an operating member (weight) that is biased by the acceleration acting on the hydraulic shock absorber is provided, and the movement of this operating member is A hydraulic shock absorber is disclosed in which the damping force characteristics are made acceleration dependent by adjusting the damping force according to the acceleration.

[0013]

However, the conventional hydraulic shock absorber described above has the following problems. That is, in the method disclosed in JP-A-62-106138, the damping force characteristics are adjusted depending on the input frequency.
There is a problem in that the damping force is not sufficiently adjusted in response to sudden acceleration input due to bumps on the road surface while the vehicle is running.

[0014] Furthermore, in the devices disclosed in Japanese Utility Model Application Publication No. 62-838 and Japanese Utility Model Application Publication No. 62-46039, the actuating member is changed in order to switch the damping force mainly using only the inertia of the actuating member. There is a problem that the weight needs to be increased and the hydraulic shock absorber becomes heavy.

The present invention has been made in view of the above points, and an object of the present invention is to provide a hydraulic shock absorber that adjusts damping force in accordance with acceleration.

[0016]

[Means for Solving the Problems] The present invention provides an oil passage that communicates between two chambers defined by an oil chamber defining member by expanding and contracting a rod inserted into a cylinder filled with oil. In a hydraulic shock absorber that generates a damping force by controlling the flow of oil fluid that is generated, a bypass passage that communicates between the two chambers and a bypass passage that is provided in the oil chamber defining member, that is movable in the vertical direction, and that a weight that blocks the bypass passage when positioned and connects the bypass passage by moving downward; a spring means that biases the weight upward; and a spring means that causes the rod to contract within the two chambers. The oil chamber has an expandable and contractible oil chamber that communicates through an orifice passage with a chamber on the side that receives compression when the oil chamber is turned in the direction, and as the oil chamber expands, an upward biasing force on the weight is increased. It is characterized by the provision of a force mechanism.

Furthermore, the hydraulic shock absorber of the present invention is characterized in that, in addition to this, an orifice is provided in the bypass passage to constantly communicate between the two chambers defined by the oil chamber defining member. shall be.

[0018]

[Operation] With this configuration, the bypass passage is normally blocked by the weight that is biased upward by a spring means, and upward acceleration acts on the hydraulic shock absorber, causing the weight to act as an inertial force. When it moves downward, the bypass passage is communicated. At this time, during the contraction stroke, the oil in the compressed chamber is pressurized and flows into the oil chamber through the orifice passage, expanding the oil chamber and increasing the biasing force of the biasing mechanism. The flow rate of the oil flowing into the oil chamber through the passage is determined by the damping coefficient of the orifice passage and the bulk elasticity coefficient of the oil chamber, and is small for large frequency inputs and small for small frequency inputs. It gets bigger. Therefore, the larger the input vibration frequency, the easier the weight will move, and the smaller the input frequency, the more difficult it will be to move the weight.

[0019]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

A first embodiment of the present invention will be explained using FIGS. 1 and 2. The hydraulic shock absorber of this embodiment differs from the conventional example shown in FIG. 9 only in the base valve part 13 (oil chamber defining member), so the same numbers are given to the same parts and only the different parts will be described in detail. explain.

In FIGS. 1 and 2, a bottomed cylindrical passage member 14 is provided on the bottom side of the cylinder 3 to define a cylinder lower chamber 3b and a reservoir chamber 3c forming two oil chambers. 14 has a cylinder lower chamber 3b and a reservoir chamber 3.
An oil passage 15 communicating with c is bored. Inner cylinder 1
A bottomed cylindrical guide member 16 is fitted to the lower end of the guide member 16 , and the bottom of the guide member 16 is fitted to the passage member 14 . A small cylinder 17 is formed on the lower end side of the bottom of the guide member 16, and an oil passage 18 that communicates the inside of the guide member 16 and the inside of the small cylinder 17 is bored. Further, the lower end side of the small cylinder communicates with the reservoir chamber 3c via an oil passage 19 and an oil passage 15 formed between the small cylinder and the passage member 14. A cap 20 is attached to the upper end of the guide 16, and the cap 20 is attached to the inside of the guide 16 and the lower cylinder chamber 3.
A communication hole 21 communicating with b is bored.

A weight 22 is fitted into the guide member 16 so as to be slidable in the vertical direction, and a spring 23 is provided to bias the weight 22 upward. A valve portion 24 is provided at the upper end of the weight 22 so as to face the communication hole 21.
By sliding, the valve portion 24 is seated and removed from the communication hole 21 to open and close the communication hole 21. The weight 22 has one end opened at the tip of the valve portion 24 and the other end opened at the lower end of the weight 22, and has a cylinder lower chamber 3b and a chamber below the weight 22 in the guide member 16. An orifice passage 25 is bored to communicate with the two, and an orifice portion 26 is provided in the middle of this orifice passage 25.

Holes 27a and 27b are bored in the side surfaces of the guide member 16 and the inner cylinder 1 to communicate the upper chamber of the weight 22 in the guide member 16 and the reservoir chamber 3c, and the communication hole 21 and the guide member A bypass passage 27 that communicates the cylinder chamber 3b and the reservoir chamber 3c is formed by the upper chamber of the weight 22 in the cylinder 16 and the holes 27a, 27b.

A small piston 28 is slidably fitted into the small cylinder 17, and a spring 29 is provided for urging the small piston 28 upward. The chamber below the weight 22 in the guide member 16 and the small piston 2 in the small cylinder 17
An oil chamber that can be expanded and contracted is formed with the upper chamber of 8.
This oil chamber has bulk elasticity due to the spring 29, and constitutes a biasing mechanism that increases the upward biasing force against the weight 22 as it expands.

A plurality of oil passages 30 are bored through the side wall of the guide member 16 in the axial direction.
The lower cylinder chamber 3b and the reservoir chamber 3c are communicated with each other by the oil passage 15 and the lower cylinder chamber 3b. A damping force generating mechanism 31 consisting of an orifice 31a and a disc valve 31b is provided at the lower end of the guide member 16 to control the flow of oil generated in the oil passage 30 during the retraction stroke to generate a damping force. A hole 32a is provided in the side wall of the inner cylinder 1 and the guide member 16 to communicate the reservoir chamber 3c and the oil passage 30.
and 32b are drilled, and these holes 32a, 32
b and an annular valve member 32d provided in the groove 33c formed on the outer periphery of the guide member 16, a check valve mechanism that allows oil fluid to flow from the reservoir chamber 3c to the cylinder lower chamber 3b during the extension stroke. 32 are configured.

The operation of the first embodiment constructed as above will now be explained. During the extension stroke, as in the conventional example shown in FIG. A damping force is generated. At this time, the amount of oil that the rod 4 has withdrawn from the inner cylinder 1 passes through the check valve mechanism 32 and flows into the cylinder lower chamber 3b from the reservoir chamber 3c.

During the retraction stroke, as the piston 5 moves, the oil in the lower cylinder chamber 3b flows into the upper cylinder chamber 3a through the check valve mechanism 7, and the rod 4 moves into the upper cylinder chamber 3a.
The amount of oil that has entered the cylinder flows from the cylinder lower chamber 3b to the reservoir chamber 3c through the base valve mechanism.

During the retraction stroke, the valve portion 24 of the weight 22 is normally seated in the communication hole 21 due to the elastic force of the spring 23, and the bypass passage 27 is blocked, so that the oil in the lower cylinder chamber 3b is Reservoir chamber 3c passes through oil passage 30
The damping force generation mechanism 31 generates a large damping force.

During the retraction stroke, when an upward acceleration of more than a predetermined value is applied to the hydraulic shock absorber, the weight 22 moves downward within the guide member 16 due to inertia, and the valve portion 24 moves from the opening of the communication hole 21. The bypass passage 27 is opened at a distance, and the oil in the cylinder lower chamber 3b flows into the reservoir chamber 3c through the bypass passage 27, and a small damping force is generated by the communication hole 21.

At this time, during the contraction stroke, the oil in the cylinder lower chamber 3b is pressurized by the sliding of the piston, and the weight 2
2 through the orifice passage 25 into the lower chamber of the weight 22 in the guide member 16, and the small piston 28 is moved by the spring 29.
The weight 22 is pushed down against the elastic force of the small piston 28, and a pressure having a bulk elastic coefficient k acts upward on the weight 22 in accordance with the amount of displacement of the small piston 28. At this time, the oil flowing through the orifice passage 25 of the weight 22 is subjected to a pressure loss by the orifice portion 26 with a damping coefficient c. Therefore, the pressure P in the cylinder lower chamber 3b
1 and the pressure P2 in the chamber below the weight 22 in the guide member 16.
The transfer function showing the relationship with is a first-order lag system P2(s)/P1(s) = 1/(1+cs/k) and has frequency dependence. Therefore, by appropriately setting the elastic force of the spring 29 and the diameter of the orifice portion 26, the pressure P1,
For example, as shown in Fig. 3, P1 is easily transmitted to P2 when a small frequency is input, and P1 is difficult to be transmitted to P2 when a large frequency is input, so that the sprung resonance frequency is 1. For input with a frequency of ~2Hz, the P2/P1 gain is approximately 0 dB, and P1 and P2 have approximately the same pressure, so the weight 22 has a large set load and becomes difficult to move downward. On the other hand, for large frequency input due to unsprung vibration, P2/
Since the P1 gain is small, the increase in P1 is difficult to be transmitted to P2, and P2 becomes smaller than P1, and the set load of the weight 22 becomes smaller, making it easier to move downward.

Therefore, not only the inertia force of the weight 22 and the elastic force of the spring 23 but also the elastic force of the spring 29 and the diameter of the orifice portion 26 cause the weight 22 to change depending on the input frequency.
Since the set load can be adjusted, the weight of the weight 22 can be reduced and the weight of the hydraulic shock absorber can be reduced. Since the damping force is immediately switched depending on the acceleration acting on the hydraulic shock absorber, it is possible to effectively absorb vibrations without delay in response to sudden vibration inputs such as bumps from the road surface while the vehicle is running.

Next, a second embodiment of the present invention will be explained using FIGS. 4 and 5. The hydraulic shock absorber of this example is
The only difference from the conventional example shown in FIG. 9 is the base valve portion 33 (oil chamber defining member), so the same members are given the same numbers and only the different parts will be described in detail.

In FIGS. 4 and 5, a bottomed cylindrical guide member 34 is fitted to the lower end of the inner cylinder 1 with its bottom facing downward, and the guide member 34 forms two oil chambers. A lower cylinder chamber 3b and a reservoir chamber 3c are defined. A small cylinder 36 is formed at the bottom of the guide member 34 and communicates with a cylindrical guide portion 35 . A cap 37 is attached to the upper end of the guide member 34, and a communication hole 38 is bored in the cap 37 to communicate the inside of the guide member 34 and the lower cylinder chamber 3b.

A weight 3 is attached to the guide portion 35 of the guide member 34.
9, a small piston 40 is fitted into the small cylinder 36 so as to be slidable in the vertical direction, and a spring 41 is interposed between the weight 39 and the small piston 40. and,
The lower chamber of the small piston 40 forms an expandable and contractible oil chamber, and this oil chamber has bulk elasticity due to the spring 41, and as it expands, it increases the upward biasing force against the weight 39. It constitutes a biasing mechanism to A valve member 42 is provided at the upper end of the weight 39 so as to face the opening of the communication hole 38 , and as the weight 39 slides, the valve member 42 seats and leaves the opening of the communication hole 38 . It is designed to open and close. The weight 39 is provided with an oil passage 43 that communicates between an upper chamber and a lower chamber of the weight 39 in the guide member 34 .

The guide member 34 is attached to the side surface of the guide member 34.
An oil passage 44 is bored through which the lower chamber of the weight 39 and the reservoir chamber 3c communicate with each other. A bypass passage 45 is formed that communicates the chamber 3b and the reservoir chamber 3c.

The lower cylinder chamber 3 is provided on the side wall of the guide member 34.
An oil passageway 46 is bored through which the oil passageway 46 communicates with the reservoir chambers 3c and 3, and a disc valve 47a and an orifice 47b face the end of the oil passageway 46 on the side of the reservoir chamber 3c.
A damping force generating mechanism 47 is provided.

The guide member 34 is provided with an orifice passage 48 that communicates the chamber below the small piston 40 in the small cylinder 36 with the oil passage 46 . Holes 49a and 48b are formed in the side walls of the inner cylinder 1 and the guide member 34 to communicate the reservoir chamber 3c and the oil passage 46. An annular valve member 49d provided in the groove 49c constitutes a check valve mechanism 49 that allows oil to flow from the reservoir chamber 3c to the cylinder lower chamber 3b during the extension stroke.

The operation of the second embodiment constructed as above will now be described. During the extension stroke, the explanation is omitted because it is the same as in the first embodiment.

During the retraction stroke, the valve member 42 of the weight 39 is normally seated at the opening of the communication hole 38 due to the elastic force of the spring 41, and the bypass passage 45 is blocked, so that the lower cylinder chamber 3b is closed. The oil flows into the reservoir chamber 3c through the oil passage 46, and a large damping force is generated by the damping force generating mechanism 47.

During the retraction stroke, when an upward acceleration of more than a predetermined value acts on the hydraulic shock absorber, the weight 39 moves downward within the guide member 34 due to inertia, and the valve portion 42 is separated from the communication hole 38. The bypass passage 45 is opened, and the oil in the cylinder lower chamber 3b flows into the reservoir chamber 3c through the bypass passage 45, and a small damping force is generated by the communication hole 38.

At this time, during the retraction stroke, the oil in the lower cylinder chamber 3b is pressurized by the sliding of the piston and passes through the oil passage 46 and the orifice passage 48 into the small cylinder 36.
The small piston 40 is pushed up against the elastic force of the spring 41. At this time, the bulk elastic coefficient k of the lower chamber of the small piston 40 of the small cylinder 36 due to the elastic force of the spring 41
' and the damping coefficient c' of the orifice passage 48, the relationship between the pressure P1' in the lower cylinder chamber 3b and the pressure P2' in the lower chamber of the small piston 40 depends on the vibration frequency as in the first embodiment. . Then, pressure P2' and small piston 4
Since it is proportional to the displacement amount of 0, the set load of the spring 41 that biases the weight 39 upward depends on the frequency of vibration. The set load becomes large, making it difficult to move downward, and in response to a large frequency input, the set load becomes small, making it easy to move downward. Therefore, the same effects as in the first embodiment can be achieved.

Next, a third embodiment of the present invention will be described in detail with reference to FIGS. 6 to 8, with the same reference numerals being given to the same members as in the second embodiment, and only different parts. A weight 51 shown in FIG. 7 is provided in a base valve section 50 having the same structure as the base valve section 33 of the second embodiment. A notch 52 is provided in the protruding valve portion 51A on the upper part of the weight 51, and this notch 52 is formed when the weight 51 closes the communication hole 38 and blocks the bypass passage 45. This serves as an orifice that constantly communicates the chamber 3b and the reservoir chamber 3c.

[0043]Thus, although the third embodiment configured in this way can also obtain the same functions and effects as the second embodiment, in particular, in this embodiment, the valve portion 51A of the weight 51 is Even if the weight 51 is seated in the communication hole 38, the notch 52 does not completely block the oil flowing back and forth within the bypass passage 45. Therefore, the damping force characteristics when the weight 51 is vibrated at a frequency large enough to move are This is the characteristic shown by the solid line in FIG. Therefore, as shown by the broken line in FIG. 8, when the oil flowing back and forth through the bypass passage 45 is completely shut off, it is possible to eliminate the occurrence of surprise strikes that occur every time T1 immediately after the shutoff, and the occurrence of surprise strikes that occur due to surprise strikes. Vibration and abnormal noise can be prevented.

[0044] In the third embodiment, the notch 52 is provided in the weight 51, but the invention is not limited to this, and even when the bypass passage 45 is blocked by the weight 51, the bypass passage 45 can be closed. In order not to completely block the oil flowing back and forth,
It is sufficient to provide an orifice that constantly communicates the bypass passage 45 and the lower cylinder chamber 3b. For example, a communication hole may be provided near the periphery of the communication hole 38 of the cap 37 or the outside thereof to serve as the orifice.

In addition, in this embodiment, the case where the damping force adjustment mechanism according to the present invention is applied to the base valve mechanism has been described, but it is also possible to For example, the damping force adjustment mechanism according to the present invention may be applied to the piston by using the piston fitted in the cylinder as the oil chamber defining member, or the reservoir chamber may be provided separately from the cylinder. It is also possible to apply it between the cylinder and the reservoir.

[0046]

[Effects of the Invention] With the hydraulic shock absorber of the present invention configured as detailed above, the weight moves in accordance with acceleration, but the set load is large in response to a small vibration frequency input. This makes it difficult to move, and when a large vibration frequency is input, the set load becomes smaller, making it easier to move. Further, since the damping force is immediately switched depending on the acceleration acting on the hydraulic shock absorber, vibrations can be effectively absorbed without delay in response to input. As a result, the damping force characteristics can be set not only by the weight of the weight but also by the elastic force of the spring and the diameter of the orifice, making it possible to reduce the weight of the weight and the weight of the hydraulic shock absorber. can. Furthermore, it is possible to effectively absorb vibrations without delay in response to sudden vibration inputs such as those caused by bumping up from the road surface while the vehicle is running, and has the excellent effect of improving riding comfort.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the first embodiment of the present invention.

FIG. 3 is a diagram showing frequency-dependent characteristics of the weight set load of the apparatus of FIGS. 1 and 2;

FIG. 4 is a vertical cross-sectional view of a main part of a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a second embodiment of the invention.

FIG. 6 is a vertical cross-sectional view of a main part of a third embodiment of the present invention.

FIG. 7 is a perspective view of the weight of the device of FIG. 6;

8 is a diagram showing damping force characteristics when the device of FIG. 6 is vibrated at a constant frequency; FIG.

FIG. 9 is a longitudinal sectional view of a conventional hydraulic shock absorber.

[Explanation of symbols] 3...Cylinder 3a...Cylinder upper chamber 3b...Cylinder lower chamber 3c...Reservoir room 4...Rod 13...Base valve mechanism 14...Passage member 16...Guide member 17...Small cylinder 21...Communication hole 22... Weight 23...Spring 24... Valve member 25...Orifice passage 26...Orifice part 27...Bypass passage 28...Small piston 29...Spring

Claims (2)

[Claims] [Claim 1] Controlling the flow of oil fluid generated in an oil fluid passage communicating between two chambers defined by an oil chamber defining member by the expansion and contraction of a rod inserted into a cylinder in which oil fluid is sealed. In a hydraulic shock absorber that generates a damping force, the hydraulic shock absorber is provided with a bypass passage communicating between the two chambers and the oil chamber defining member, is movable in the vertical direction, and blocks the bypass passage when located at the upper limit. a weight that connects the bypass passage by moving downward; a spring means that biases the weight upward; and a weight that compresses when the rod moves in the contraction direction within the two chambers. A biasing mechanism is provided, which has an expandable and contractible oil chamber communicating with the receiving side chamber via an orifice passage, and increases an upward biasing force on the weight as the oil chamber expands. A hydraulic shock absorber featuring: 2. The hydraulic shock absorber according to claim 1, wherein an orifice is provided in the bypass passage to constantly communicate between the two chambers defined by the oil chamber defining member.