JP2005226772A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the generation of abnormal noises when switching a damping performance of a shock absorber capable of changing its damping force at numerous steps. <P>SOLUTION: A bypass passage 90 for bypassing a damping force generating device 16 provided at a piston 14 is arranged in a piston rod 36, and a damping force switching device 18 is also provided. The damping force switching device 18 is capable of moving a screw shaft 210 by turning a nut 212 with a stepping motor 180, and opening and shutting the bypass passage 90 by moving a spool 110, and permitting or blocking connection between a head-side chamber 38 and a rod-side chamber 40, and adjusting a flow rate of liquid by means of opening control of the connection of both chambers. A closing chamber 230 and an opening chamber 232 arranged on both sides of a screw shaft 210 and a nut 212 are interconnected with an interconnecting hole 240 arranged in the screw shaft 210, and the screw shaft 210 can be moved by the operation of the interconnecting hole 240. A nozzle 20 is arranged inside the interconnecting hole 240, and the nozzle 20 gives resistance into operating liquid flowing the interconnecting hole 240 when switching the damping performance of the shock absorber so as to restrain overshooting and restrain the generation of abnormal noises by controlling vibrations. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shock absorber, and more particularly to a shock absorber capable of controlling damping performance.

A shock absorber capable of controlling the damping performance is already known as described in Patent Document 1 below, for example. In the shock absorber described in Patent Document 1, a piston is liquid-tightly and slidably fitted to a cylindrical main body extending in the vertical direction, a piston rod is extended on the upper side, and a damping force generator is applied to the piston. Is provided. The piston rod is provided so as to penetrate the piston in the axial direction, and a bypass passage is provided in the piston passage to connect the head side chamber and the rod side chamber formed on both sides of the piston, and a valve device is provided in the bypass passage. The communication between the head side chamber and the rod side chamber is allowed or prevented. The valve device includes a spool fitted in the bypass passage so as to be movable in the axial direction. When the spool is moved by the drive device, the bypass passage is opened and closed, and the head side chamber and the rod side chamber communicate with each other. The cross-sectional area of the flow path when this is allowed is changed according to the position of the spool, and the flow rate is changed. If the valve device opens the bypass passage and connects the head side chamber and the rod side chamber, the flow rate of the hydraulic fluid flowing through the damping force generator provided in the piston is reduced, the damping force is reduced, and the flow rate of the bypass passage is reduced. In some cases, the damping force is set to zero.
Japanese Patent Laid-Open No. 5-60165

However, this shock absorber has a problem that abnormal noise is generated when the damping performance is controlled. When the damping force is changed, the screw shaft is moved and the spool is moved to a position where a predetermined damping force can be obtained. For example, if the spool suddenly starts or stops moving, the spool shaft moves. Sound is generated. Further, if an overshoot occurs when the spool is stopped, the spool is moved in the opposite direction to that at the time of change, or is reciprocated in both the forward and reverse directions to be positioned at a predetermined position. As a result, vibration is generated and abnormal noise is generated.
An object of the present invention is to suppress the occurrence of abnormal noise at the time of change in a shock absorber that can change damping force.

In order to solve the above problems, a shock absorber according to the present invention includes (a) a generally cylindrical body extending vertically, and (b) liquid-tight and slidably fitted in the body. And a piston rod extending on one side and forming a head side chamber and a rod side chamber on both sides of the main body in cooperation with the main body, and (c) an operation provided between the head side chamber and the rod side chamber provided on the piston. A damping force generator that generates a damping force by applying resistance to the flow of the liquid; (d) a bypass passage that bypasses the damping force generator; and a flow of hydraulic fluid in the bypass passage that is provided in the bypass passage. A damping device for controlling the damping force, and a driving device for driving the valve device, and controlling the damping force in cooperation with the damping force generator;
(e) The damping force control device includes a vibration suppressing device that suppresses vibration when the damping force is changed.

The piston rod may be extended to the upper side of the piston or may be extended to the lower side. When the shock absorber is provided in a vehicle suspension device, the piston rod extended upward is connected to a vehicle body side member as a sprung member, and the main body is connected to a wheel side member as an unsprung member. The piston rod extended downward is connected to the wheel side member, and the main body is connected to the vehicle body side member.
In the shock absorber according to the present invention, the damping force is changed by the damping force control device, and the vibration at that time is suppressed by the vibration suppressing device. Therefore, vibration does not occur or is small even if it occurs, and generation of abnormal noise due to vibration is suppressed. The start or stop of the rapid movement of the actuating member is also suppressed, and thereby the generation of abnormal noise is also suppressed.
Even if the valve device and the drive device can be switched between a communication-permitted state that allows communication between the head-side chamber and the rod-side chamber and a blocking state, the flow rate of the hydraulic fluid in the communication-permitted state is determined in multiple stages (continuous). The change may be considered adjustable in an infinite number of stages), but it is desirable that both be possible.

Aspects of the Invention

  In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

  In each of the following paragraphs, (1) corresponds to claim 1, (2) corresponds to claim 2, and (3) and (4) are combined in claim 3, The combination of paragraphs (5) and (6) corresponds to claim 4, and the combination of paragraphs (5), (7) and (9) corresponds to claim 5.

(1) A main body that is generally cylindrical and extends in the vertical direction;
A piston that is fitted in a liquid-tight and slidable manner in the main body and a piston rod extends on one side, and forms a head side chamber and a rod side chamber on both sides of the main body together with the main body,
A damping force generating device that is provided in the piston and generates a damping force by applying resistance to the flow of the hydraulic fluid between the head side chamber and the rod side chamber;
A bypass passage that bypasses the damping force generator, a valve device that is provided in the bypass passage and controls the flow of hydraulic fluid in the bypass passage, and a drive device that drives the valve device, and generates the damping force A damping force control device for controlling the damping force in cooperation with the device;
A shock absorber including a vibration suppression device that suppresses vibration when the damping force is changed in the damping force control device.
(2) The valve device is operably provided, and includes a valve body that controls a flow of hydraulic fluid in the bypass passage by the operation, and the vibration suppression device is operable with the valve body, At least one volume change chamber whose volume changes in accordance with the operation of the operation member, and allows the hydraulic fluid to flow into and out of the volume change chamber in communication with the volume change chamber and restricts the flow of the hydraulic fluid The shock absorber according to item (1), including a throttle passage.
The actuating member may be, for example, a rotating member or an axially moving member (axial member) that moves in the axial direction. For example, when the valve device is a rotary valve in which the valve body is a rotating body and the communication state between the head side chamber and the rod side chamber is controlled by the rotation, the operating member is a rotating member that rotates together with the valve body. The rotating member includes, for example, a rotating shaft portion and a partition wall portion extending in the radial direction therefrom, and at least one side of the partition wall portion has a volume change chamber whose volume changes as the rotating member rotates. Is formed, and a throttle passage is formed for communicating the volume change chamber with another space (which may be another volume change chamber, a head side chamber or a rod side chamber). When the hydraulic fluid flows into and out of the volume change chamber through the throttle passage, the rotation member is allowed to rotate and the valve body is allowed to rotate, but the hydraulic fluid flowing through the throttle passage is restricted. As a result, resistance is imparted to the rotation of the valve body, overshoot is suppressed, and vibration is suppressed.
The throttle passage may have a small cross-sectional area over its entire length (especially suitable when the passage itself is short), and the whole passage may function as a throttle. May be provided. The diaphragm may be a fixed diaphragm whose amount of diaphragm does not change or a variable variable diaphragm. The variable aperture may be an electromagnetic variable aperture or a manual variable aperture.
(3) The valve device is provided so as to be movable in the axial direction, and includes a valve body that controls the flow of hydraulic fluid in the bypass passage by the movement, and the drive device moves the valve body in the axial direction. The shock absorber according to item (1) or (2), including a valve body driving device.
Assuming that the flow of the hydraulic fluid in the bypass passage is controlled by moving the valve body in the axial direction, for example, the valve body can have a simple configuration or a diameter compared to the case where the valve device is a rotary valve. The valve device can be configured simply.
(4) The shock absorber according to (3), wherein the valve body driving device includes an electric rotary actuator and a motion conversion device that converts the rotation of the electric rotary actuator into a linear movement in the axial direction of the valve body.
For example, an electric rotary motor such as a stepping motor or a servo motor is used as the electric rotary actuator. The stepping motor and the servo motor are motors capable of accurately controlling the rotation angle, but other electric rotary motors may be used.
By actuating the electric rotary actuator, the valve body is linearly moved in the axial direction. If an electric rotary actuator is used as the drive source, for example, the movement of the valve element can be easily controlled by controlling the supply current, and the drive device can be configured compactly.
(5) The shock absorber according to (4), wherein the motion conversion device includes a screw shaft and a nut.
(6) The shock absorber according to (5), wherein the screw shaft and the nut are slip-fitted.
When the nut and the screw shaft are rotated relative to each other and moved relative to each other in the axial direction, slip occurs between them, and the friction caused thereby reduces the overshoot of the valve body and suppresses vibration. Further, it is easy to reduce the gap between the nut and the screw shaft as compared with the ball screw.
(7) The screw shaft is provided so as to be movable concentrically and integrally with the valve body, and in the screw shaft, two screw shafts positioned on both sides of the fitting portion of the screw shaft and the nut in the axial direction. A communication hole for communicating the liquid chamber is provided, one of the two liquid chambers is an open chamber opened to one of the head side chamber and the rod side chamber, and the other is not opened to either the head side chamber or the rod side chamber The shock absorber according to (5) or (6), which is a closed room.
When the shock absorber is contracted, the piston is moved to the head side chamber side, the hydraulic pressure in the head side chamber becomes higher than the hydraulic pressure in the rod side chamber, and when the shock absorber is extended, the hydraulic pressure The height is reversed. In both the head side chamber and the rod side chamber, the fluid pressure changes with the operation of the shock absorber, but the two fluid chambers located on both sides of the fitting portion between the screw shaft and the nut are communicated with each other through the communication holes. Therefore, the hydraulic pressures of these two liquid chambers are kept equal to each other. Further, when the damping force is changed, the hydraulic fluid flows through the communication hole between the open chamber and the closed chamber, and the movement of the screw shaft is allowed.
(8) The electric rotary actuator includes a stator that can move integrally with the piston, and a rotor that can rotate relative to the stator but cannot move relative to the axial direction. The shock absorber according to item (7), wherein the shock absorber is provided on an inner peripheral side so as to be rotatable integrally with the rotor, and the closed chamber is formed in the stator.
If the electric rotary actuator and the screw mechanism as the motion conversion device are configured to overlap each other in the axial direction and a closed chamber is formed in the stator, the overall length of the shock absorber can be shortened or the stroke can be lengthened. it can. The electric rotary actuator can be provided on the side opposite to the piston rod with respect to the piston. However, it is desirable that the electric rotary actuator be provided on the piston rod side because the wiring for supplying the current is easy.
(9) The shock absorber according to (7) or (8), wherein the vibration suppressing device includes a throttle provided in the communication hole.
When this term is dependent on the term (2), the screw shaft functions as an operating member, the closed chamber functions as a volume change chamber, and the communication hole and the throttle function as a throttle passage.
When the screw shaft is moved, the hydraulic fluid flowing through the communication hole is squeezed by the throttle, so that resistance is given to the movement of the screw shaft and the overshoot of the screw shaft and the valve body is suppressed. Therefore, it is not necessary to adjust the position of the valve body, or even if it is necessary, the vibration is reduced when the valve body is stopped, and the generation of abnormal noise is suppressed.
Since one of the two fluid chambers located on both sides of the fitting part between the screw shaft and the nut is a closed chamber, in order for the screw shaft to move, inflow and outflow of hydraulic fluid in the closed chamber are necessary. A hole is provided. Therefore, vibration can be easily and reliably suppressed by providing a restriction in the communication hole and imparting resistance to the flow of the hydraulic fluid.
In the shock absorber of this section, resistance is given to the flow of hydraulic fluid, but friction resistance against rotation and movement of nuts and screw shafts is not given like the friction resistance application device described in (10). Therefore, the screw shaft can be moved without increasing the driving force of the electric rotary actuator. Further, compared with the frictional resistance applying device, there are few components of the vibration suppressing device and the structure is simple.
(10) The vibration suppressing device includes a frictional resistance applying device that applies a frictional resistance to rotation or axial movement of at least one of the screw shaft and the nut. The listed shock absorber.
The frictional resistance imparting device includes, for example, a frictional resistance imparting member that contacts the screw shaft and the nut, and a contact state maintaining device that maintains the frictional resistance imparting member in contact with the nut and the screw shaft. If friction resistance is applied to the rotation and movement of the screw shaft and nut, overshoot and vibration of the screw shaft and nut are suppressed, and generation of abnormal noise is suppressed. According to the shock absorber of this section, vibration can be suppressed by mechanically imparting resistance to the screw shaft and the nut.

  Several embodiments of the claimable invention will now be described in detail with reference to the drawings. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do.

  FIG. 1 shows a shock absorber 10 which is an embodiment of the claimable invention. The shock absorber 10 is provided in a vehicle and has a function as a strut, and is also used as a link member of a suspension device. The shock absorber 10 is provided between a vehicle body side member (not shown) that is a sprung member and a wheel side member (not shown) that is an unsprung member, and attenuates vibrations of the vehicle body. The shock absorber 10 is of a twin tube type, and as shown in FIGS. 1 and 2, a main body 12, a piston 14, a damping force generator 16, a damping force switching device 18 as a damping force control device, and a vibration suppressing device. A diaphragm 20 is included.

  The main body 12 extends in the vertical direction and includes an outer cylinder 30 and an inner cylinder 32 as shown in FIG. The inner cylinder 32 is concentrically fitted and fixed in the outer cylinder 30, and a reservoir chamber 34 is provided between them. The piston 14 is fitted in the inner cylinder 32 in a fluid-tight and slidable manner, and a piston rod 36 is extended on the upper side. A head side chamber 38 is formed on the upper side, and a rod side chamber 40 is formed on the upper side. The main body 12 can also be called a cylinder main body because the piston 14 slides in the inner cylinder 32. The main body 12 is attached to an unsprung member at a mounted portion 42 provided on the outer cylinder 30, and an upper end portion of the piston rod 36 protruding from the main body 12 is attached to the sprung member. The piston rod 36 is kept liquid-tight by a seal member 44 provided between the outer cylinder 30 and the inner cylinder 32 and is guided to move by a guide member 46. The outer cylinder 30 is also provided with a spring retainer 48, and a suspension spring (not shown) is provided between the outer cylinder 30 and the sprung member.

The reservoir chamber 34 and the head side chamber 38 are communicated with each other via a base valve 54. The reservoir chamber 34 is filled with hydraulic fluid and low-pressure gas. The base valve 54 generates a damping force due to the flow of hydraulic fluid between the head side chamber 38 and the reservoir chamber 34 and is well known, and thus the description thereof is omitted.
It is not essential for the base valve 54 to have a damping force generation function. What is necessary is just to have the function which compensates the excess and deficiency of the hydraulic fluid resulting from the volume change of the head side chamber 38 at least.

The damping force generator 16 will be described.
The damping force generator 16 is provided on the piston 14 as shown in FIG. The damping force generator 16 includes an extension damping force generator 60 and a contraction damping force generator 62. In this embodiment, the extension damping force generator 60 penetrates the piston 14 in the axial direction, connects the rod side chamber 40 and the head side chamber 38, and communicates with each other by a plurality of connection passages 66 (FIG. 2). Only one is shown), and a valve 68 and a spring 70 as an elastic member which is a kind of biasing means. In this embodiment, the valve 68 has a disk shape and is made of an elastic material. The valve 68 is arranged in contact with the surface of the piston 14 on the head side chamber 38 side, and is in contact with the piston 14 by a spring 70. The opening on the head side chamber 38 side of the connection passage 66 is blocked.

  Similarly, the compression damping force generating portion 62 penetrates the piston 14 in the axial direction, connects the rod side chamber 40 and the head side chamber 38, and communicates with each other, and a disk-like shape made of an elastic material. And a spring 80. The plurality of connection passages 76 are provided at positions that are different from the connection passage 66 in the radial direction of the piston 14, and in the present embodiment, on the outer peripheral side of the connection passage 66 and away from the valve 68. The head side chamber 38 is always in communication. The valve 78 contacts the surface of the piston 14 on the rod side chamber 40 side, is arranged in a state of closing the opening of the connection passage 76 on the rod side chamber 40 side, and is biased in a direction to contact the piston 14 by a spring 80 to be connected. The opening of the passage 76 is blocked. The opening on the rod side chamber 40 side of the connection passage 66 is provided away from the valve 78, is not blocked by the valve 78, and is always communicated with the rod side chamber 40.

  Accordingly, when the sprung member and the unsprung member are moved relative to each other in a direction approaching each other, the shock absorber 10 contracts, and the hydraulic pressure in the head side chamber 38 becomes higher than the hydraulic pressure in the rod side chamber 40. The hydraulic fluid flows from the head side chamber 38 to the rod side chamber 40 through 76, and at that time, the valve 78 is bent against the biasing force of the spring 80, opens the connection passage 76, flows in, and the flow of the hydraulic fluid As a result, resistance is applied to the slag and a damping force is generated. Further, when the sprung member and the unsprung member are moved relative to each other in a direction away from each other, the shock absorber 10 extends, and the hydraulic pressure in the rod side chamber 40 becomes higher than the hydraulic pressure in the head side chamber 38, the working fluid is It flows into the head side chamber 38 from the rod side chamber 40 through the connection passage 66. At this time, the valve 68 is bent against the biasing force of the spring 70, and the connection passage 66 is opened to flow into the head side chamber 38. Resistance is applied to the flow of the hydraulic fluid, and a damping force is generated. In addition, the said base valve 54 is comprised similarly to the damping force generator 16, for example.

The damping force switching device 18 will be described.
As shown in FIG. 2, the damping force switching device 18 includes a bypass passage 90, a spool valve 92 as a valve device, and a spool driving device 94 as a valve body driving device. , Provided in the piston rod 36. In this embodiment, the lower end of the piston rod 36 is concentrically fitted to the piston 14, protrudes downward from the piston 14 and faces the head side chamber 38, and is fixed by appropriate fixing means such as screws and nuts. While being fixed so that attachment or detachment is possible, it is extended from the piston 14 to the upper side, and the bypass channel | path 90 is provided in the inside. The bypass passage 90 is opened at the lower end surface of the piston rod 36 and is opened in the head side chamber 38, and an axial passage 98 provided concentrically with the piston rod 36 and an axial passage 98 of the piston rod 36 are provided. And includes a plurality of radial passages 100 that connect the axial passage 98 and the rod side chamber 40, and bypass the damping force generator 16.

  As shown in FIG. 2, the spool 110 as the valve body of the spool valve 92 is concentrically fitted in the axial passage 98 and is substantially liquid-tight and slidably fitted in the axial direction. Annular grooves 112 and 114 that open to the surface are provided, and an annular land 116 is provided between the grooves 112 and 114. The lower end portion of the spool 110 is slightly smaller in diameter than the inner diameter of the axial passage 98, and a gap is provided between the inner periphery of the axial passage 98. An opening on the axial passage 98 side of the radial passage 100 is an annular passage 120, and another annular passage 122 that opens to the axial passage 98 is formed below the annular passage 120. An annular land 124 is provided between the annular passages 120 and 122.

  Therefore, when the spool 110 is located at a position where the land 116 is fitted to the land 124, the radial passage 100 is closed, and the spool valve 92 communicates with the head side chamber 38 and the rod side chamber 40 to prevent communication. It becomes a blocking state. From this state, the spool 110 is in a direction in which the land 116 is disengaged from the land 124, and in this embodiment, the spool 110 is moved downward from the position shown in FIG. 2 and the land 116 faces the annular passage 122. Then, the radial passage 100 is opened and communicated with the axial passage 98, and a communication permission state in which communication between the head side chamber 38 and the rod side chamber 40 is permitted is obtained. The flow rate of the hydraulic fluid flowing through the bypass passage 90 in the communication-permitted state is adjustable, and increases as the gap (cross-sectional area) between the land 116 and the land 124 increases. In the communication-permitted state, the hydraulic fluid can flow not only through the piston 14 but also through the bypass passage 90 between the head side chamber 38 and the rod side chamber 40, and at least a part of the hydraulic fluid is supplied to the damping force generator 16. The flow resistance is not given and the damping force is reduced. The larger the gap between the land 116 and the land 124, the smaller the damping force generated by the damping force generating device 16, and all the hydraulic fluid flows only through the bypass passage 90. The damping force generating device 16 It is also possible to obtain a state where no occurrence occurs. In the present embodiment, the spool valve 92 and the spool driving device 94 can be switched between a communication permission state and a communication blocking state, and, as will be described later, the flow rate of the hydraulic fluid in the communication permission state is a plurality of stages. In the embodiment, it can be adjusted in two stages.

In addition, resistance is also given to the hydraulic fluid flowing through the bypass passage 90 by the damping force generator 130, and damping force is generated.
As shown in FIG. 2, the damping force generation device 130 is provided outside the piston rod 36, the device main body 132 fixed to the piston rod 36, the extension damping force generation unit 134 provided in the device main body 132, and A shrinkage damping force generator 136.

  The extension damping force generator 134 includes a plurality of connection passages 140 and valves 142 that are open on the lower surface of the apparatus main body 132 and extend in the axial direction. Each upper part of these connection passages 140 is opened to an annular liquid chamber 146 provided in the apparatus main body 130. The valve 142 has a circular plate shape made of an elastic material, and is provided in a state of covering the upper opening of the connection passage 140 and the opening facing the liquid chamber 146. The liquid chamber 146 is communicated with a plurality of other passages 148 provided radially in the apparatus main body 132, and is communicated with the radial passage 100 of the bypass passage 90 by the passage 148 and the annular passage 150. .

  The contraction damping force generator 136 includes a plurality of connection passages 160 and a valve 162 that are open on the upper surface of the apparatus main body 132 and extend in the axial direction. Each of these connection passages 160 communicates with the passage 148. The valve 162 has a disk shape made of an elastic material, is provided in contact with the upper surface of the apparatus main body 132, and closes the upper opening of the connection passage 160. The apparatus main body 130 is formed by assembling a plurality of members integrally with each other, and thereby a liquid chamber 146 is provided.

  Therefore, when the shock absorber 10 is contracted in a state where the spool valve 92 is in the communication-permitted state, the hydraulic fluid in the head side chamber 38 is connected through the axial passage 98, the radial passage 100, and the passages 150 and 148. It flows into the passage 160, flows into the rod side chamber 40 while elastically deforming the valve 162, is given resistance, and a damping force is generated. Further, when the shock absorber 10 is extended, the hydraulic fluid in the rod side chamber 40 flows into the liquid chamber 146 from the connection passage 140 while elastically deforming the valve 142, and further flows into the bypass passage 90 from the passages 148 and 150. To do. At that time, resistance is applied to the flow of the hydraulic fluid, and a damping force is generated. The damping force generated by the damping force generator 130 is smaller than the damping force generated by the damping force generator 16 provided in the piston 14, and the bypass passage 90 is opened and the damping force generator 16 is bypassed to operate. The damping force obtained is smaller when the liquid flows than when the bypass passage 90 is closed.

The spool driving device 94 will be described.
In this embodiment, the spool driving device 94 is a stepping motor 180 that is an electric motor as a type of electric rotary actuator as a driving source, and a motion conversion device that converts the rotation of the stepping motor 180 into a linear motion in the axial direction of the spool 110. 182. In the piston rod 36, as shown in FIG. 2, a chamber 184 is provided following the upper end of the axial passage 98 of the bypass passage 90, and a spool driving device 94 is disposed.

  In this embodiment, the stepping motor 180 includes a stator 190 and a rotor 192 that is provided so as to be relatively rotatable with respect to the stator 190 and not to be relatively movable in the axial direction. The chamber 184 is partitioned by a seal member 194 into a liquid chamber 196 that is communicated with the axial passage 98 and filled with hydraulic fluid, and a space 198 that is kept airtight, and a coil 200 is provided in the space 198. The stator 190 is disposed so as not to move and concentric with the piston rod 36. The stator 190 can move integrally with the piston 14 via the piston rod 36. The rotor 192 includes a plurality of permanent magnets 202 and is disposed concentrically with the piston rod 36 in the liquid chamber 196 together with the motion converter 182. The stepping motor 180 is controlled by a control device (not shown) mainly composed of a computer.

  The motion conversion device 182 includes a screw shaft 210 and a nut 212 in this embodiment. The nut 212 is provided on the inner peripheral side of the rotor 192 so as to be rotatable integrally with the rotor 192, and is an axis of the piston rod 36 by the piston rod 36 through bearings 214 and 216, and It is supported so as to be rotatable about the same axis as the axis. In this embodiment, the screw shaft 210 and the nut 212 are slip-fitted.

  The screw shaft 210 is screwed into the nut 212, and a shaft portion 220 having no thread is provided concentrically and integrally at a lower portion protruding from the nut 212, and a lower end portion of the screw shaft 210 is formed on the spool. 110 is fitted concentrically. The spool 110 is biased in the direction to be pulled out from the screw shaft 210 by a spring 222 as an elastic member which is a kind of biasing means disposed between the spool 110 and the spool 110 is prevented from being pulled out by a retaining ring 224. And is moved integrally with the screw shaft 210. In addition, a protrusion 226 protrudes radially outward from the shaft 220 and is fitted into a groove 228 provided in parallel to the axis of the piston rod 36 to prevent relative rotation. . Therefore, when the nut 212 is rotated by the stepping motor 180, the screw shaft 210 is moved in the axial direction and the spool 110 is moved in the axial direction, so that the communication state between the head side chamber 38 and the rod side chamber 40 is switched. And the flow rate is adjusted. Each of the protrusion 226 and the groove 228 constitutes an engaging portion and constitutes a relative rotation blocking device.

  By thus providing the rotor 192 and the motion conversion device 182, the liquid chamber 196 is partitioned into an upper side and a lower side of the fitting portion between the screw shaft 210 and the nut 212, and on both sides of the fitting portion. Liquid chambers 230 and 232 are located. A clearance in the radial direction is provided between the spool 110 and the shaft portion 220, the lower liquid chamber 232 is an open chamber opened to the head side chamber 38, and the upper liquid chamber 230 is a head This is a closed chamber that is not open to either the side chamber 38 or the rod side chamber 40. Hereinafter, the liquid chamber 232 is referred to as an open chamber 232, and the liquid chamber 230 is referred to as a closed chamber 230. The closed chamber 230 is located above the fitting portion and is formed in the stator 190.

  As shown in FIG. 2, the screw shaft 210 has both ends opened to the closed chamber 230 and the open chamber 232, and a communication hole 240 for communicating the closed chamber 230 and the open chamber 232 is provided. As shown in FIG. 3, the throttle 20 is provided in the communication hole 240. In this embodiment, the throttle 20 is a passage having a circular cross section whose diameter is smaller than the inner diameter of the communication hole 240 and whose cross-sectional area is smaller than the cross-sectional area of the communication hole 240, and has a passage 241 shorter than the communication hole 240. The member 242 is provided by being press-fitted into the communication hole 240.

Next, the operation will be described.
The shock absorber 10 attenuates the vibration of the vehicle body by applying resistance to the hydraulic fluid flowing between the head side chamber 38 and the rod side chamber 40 during expansion and contraction. For example, it is switched to three stages and changed. As shown in FIG. 4, the damping force mode can be switched to three stages of a soft mode with a minimum damping force, an intermediate medium mode, and a maximum hard mode. Is set.

  If the hard mode is selected, the screw shaft 210 is moved and the spool 110 is moved to the hard position set for the hard mode. The driving amount and driving direction of the stepping motor 180 are determined based on the position of the screw shaft 210 when the damping performance mode is selected and the position where the selected damping performance mode is obtained, and a predetermined current is supplied to the nut 212. It is rotated and the screw shaft 210 is moved. Thereby, the spool 110 is moved to the hard position shown in FIG. 4 and the bypass passage 90 is closed. Therefore, when the shock absorber 10 is expanded and contracted, the working fluid in the rod side chamber 40 and the working fluid in the head side chamber 38 are provided in the piston 14 as indicated by a solid arrow when extended and by a broken arrow when contracted. All the hydraulic fluid flowing through only the connecting passages 66 and 76 and flowing between the chambers 38 and 40 is given flow resistance by the damping force generator 16. This flow resistance is large and vibration is greatly damped. The screw shaft 210 is kept in a position where the selected attenuation mode is obtained.

  If the soft mode is selected, the spool 110 is moved to the soft position set for the soft mode. As shown in FIG. 4, the spool 110 is moved downward as compared with the case where the spool 110 is located at the hard position, and the bypass passage 90 is moved to the fully opened position where the flow rate is maximized. Therefore, when the shock absorber 10 is expanded and contracted, the hydraulic fluid in the rod side chamber 40 and the hydraulic fluid in the head side chamber 38 are connected to the connection passage 66 provided in the piston 14 as indicated by solid arrows and broken arrows, respectively. 76 does not pass and flows only through the bypass passage 90. This flow rate is the largest among the three modes, the applied flow resistance is minimum, and the vibration damping force is minimum.

  If the medium mode is selected, the spool 110 is moved to the medium position set for the medium mode. The medium position is a position between the hard position and the soft position, and the bypass passage 90 is opened, but its flow rate is less than that in the soft position. Therefore, when the shock absorber 10 is expanded and contracted, the working fluid in the rod side chamber 40 and the working fluid in the head side chamber 38 are connected to the connection passages provided in the piston 14 as indicated by solid arrows and broken arrows, respectively. 66 and 76 and the bypass passage 90, and the flow rate of the working fluid flowing through the piston 14 is smaller than that in the hard mode selection, and the damping force generated by the damping force generator 16 is accordingly selected in the hard mode. Although it is reduced from the time, it is larger than when the soft mode is selected.

  Regardless of which mode is selected, when the shock absorber 10 is contracted, the piston 14 is moved to the head side chamber 38 side, and the hydraulic pressure in the head side chamber 38 is changed to the hydraulic pressure in the rod side chamber 40. When it becomes higher and the shock absorber 10 is extended, the hydraulic pressure is reversed. In both the head side chamber 38 and the rod side chamber 40, the hydraulic pressure changes with the operation of the shock absorber 10, the hydraulic fluid flows between the head side chamber 38 and the rod side chamber 40, and the damping force according to the selected damping performance mode is applied. Although generated, the closed chamber 230 and the open chamber 232 which are two liquid chambers located on both sides of the fitting portion between the screw shaft 210 and the nut 212 are communicated with each other through the communication hole 240. The hydraulic pressures in the chamber 230 and the open chamber 232 are kept equal to each other and do not affect the damping performance.

  When the screw shaft 210 is moved to switch the damping performance, the working fluid flows through the communication hole 240 between the closed chamber 230 and the open chamber 232, and the movement of the screw shaft 210 is allowed. The flow of the hydraulic fluid is throttled by the throttle 20 to provide resistance. Therefore, when the spool 110 is moved to a position where the selected damping performance can be obtained, overshoot is suppressed, it is difficult to overshoot, it is small even if overshoot occurs, the position adjustment of the spool 110 is easy, and damping is performed. When the performance is switched, vibration when the spool 110 is stopped is suppressed, and generation of abnormal noise is suppressed. The stepping motor 180 is controlled by the control device to move the screw shaft 210 and move the spool 110 to a position where the selected damping performance is obtained. The position of the spool 110 is detected by a position detection device (not shown). If the position is deviated from the selected position, the spool 110 is moved in the opposite direction to that when the damping performance is switched, or is reciprocated in both the forward and reverse directions to be adjusted. This adjustment is unnecessary or less, and the vibration of the hydraulic fluid is transmitted from the piston rod 36 to the vehicle body, thereby suppressing abnormal noise in the vehicle.

The vibration suppressing device may be a frictional resistance applying device that applies a frictional resistance to the movement of the screw shaft. The embodiment will be briefly described with reference to FIGS.
The frictional resistance imparting device 302 of the shock absorber 300 according to the present embodiment has at least one, for example, three frictional resistance imparting pieces 304 as frictional resistance imparting members and a frictional resistance imparting member holding member or a frictional resistance imparting member in contact state. A spring 306 which is an elastic member, which is a kind of biasing means as a member, is provided on the inner peripheral side of the nut 212 as shown in FIG. Each of the three frictional resistance imparting pieces 304 has a generally rectangular plate shape, and is made of, for example, felt. The spring 306 has an endless annular shape, and the three frictional resistance imparting pieces 304 are held at equal angular intervals by the spring 306. In the state where the frictional resistance applying device 302 is removed from the nut 212, the spring 306 does not hold the frictional resistance applying piece 304 at the portion where the three frictional resistance applying pieces 304 are held as shown in FIG. 6. Located on the center side of the part. When the frictional resistance applying device 302 is assembled to the nut 212, the spring 306 is elastically deformed in a circular shape from the state shown in FIG. As a result, the three frictional resistance imparting pieces 304 are brought into elastic contact along the screw shaft 210 to impart a frictional resistance.

  In the present shock absorber 300, similarly to the shock absorber 10, the screw shaft 210 is moved, the spool 110 is moved, and the damping performance is switched. At that time, the screw shaft 210 is given frictional resistance by the frictional resistance applying piece 304, and overshoot is suppressed and vibration is suppressed. Even if the contact surface brought into contact with the screw shaft 210 is worn, the frictional resistance applying piece 304 is kept in contact with the screw shaft 210 by the urging of the spring 306, and provides friction resistance when the screw shaft 210 moves. To do.

  The damping force switching device may be provided separately from the piston rod.

  The throttle may be provided by fixing the throttle forming member in the middle of the communication hole by an appropriate fixing means such as press fitting, but may be provided integrally with the communication hole.

  Further, the shock absorber may be other than a twin tube type, for example, a mono tube type. Furthermore, the structure of the suspension device to which the shock absorber is attached does not matter. For example, the claimable invention can be applied to a shock absorber not serving as a strut.

It is a front view (partial cross section) which shows the shock absorber which is an Example of claimable invention. It is front sectional drawing which shows the damping-force generator of the said shock absorber, a damping-force switching apparatus, etc. It is front sectional drawing which shows the aperture | diaphragm | restriction provided in the screw shaft of the spool drive device of the said shock absorber. It is a figure explaining the 3 step | paragraph attenuation | damping performance obtained by the said shock absorber. It is front sectional drawing which shows the frictional resistance provision apparatus of the shock absorber which is another Example of claimable invention. It is a top view which shows the said frictional resistance provision apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10: Shock absorber 12: Main body 14: Piston 16: Damping force generator 18: Damping force switching device 20: Restriction 36: Piston rod 38: Head side chamber 40: Rod side chamber 90: Bypass passage 92: Spool valve 94: Spool drive device 110: Spool 180: Stepping motor 182: Motion conversion device 190: Stator 192: Rotor 210: Screw shaft 212: Nut 230: Liquid chamber (closed chamber) 232: Liquid chamber (open chamber) 240: Communication hole 300: Shock absorber 302 : Friction resistance applying device

Claims (5)

A generally cylindrical body extending vertically,
A piston that is fitted in a liquid-tight and slidable manner in the main body and a piston rod extends on one side, and forms a head side chamber and a rod side chamber on both sides of the main body together with the main body,
A damping force generating device that is provided in the piston and generates a damping force by applying resistance to the flow of the hydraulic fluid between the head side chamber and the rod side chamber;
A bypass passage that bypasses the damping force generator, a valve device that is provided in the bypass passage and controls the flow of hydraulic fluid in the bypass passage, and a drive device that drives the valve device, and generates the damping force A damping force control device for controlling the damping force in cooperation with the device;
A shock absorber, comprising: a vibration suppressing device for suppressing vibration when the damping force is changed in the damping force control device.   The valve device is provided so as to be operable, and includes a valve body that controls the flow of hydraulic fluid in the bypass passage by the operation, and the vibration suppressing device is operable with the valve body, and the operation member At least one volume change chamber whose volume changes in accordance with the operation of, and a throttle passage which communicates with the volume change chamber and allows the hydraulic fluid to flow into and out of the volume change chamber and restricts the flow of the hydraulic fluid. The shock absorber according to claim 1, comprising:   The valve device is provided so as to be movable in the axial direction, and includes a valve body that controls the flow of hydraulic fluid in the bypass passage by the movement, and the drive device includes an electric rotary actuator and rotation of the electric rotary actuator A shock absorber according to claim 1 or 2, further comprising a valve body drive device for moving the valve body in the axial direction. .   The shock absorber according to claim 3, wherein the motion conversion device includes a screw shaft and a nut, and the screw shaft and the nut are slip-fitted.   The motion conversion device includes a screw shaft and a nut, the screw shaft is provided so as to be movable concentrically and integrally with the valve body, and the screw shaft and the nut are fitted in the screw shaft in the axial direction. A communication hole for communicating two liquid chambers located on both sides of the section, one of the two liquid chambers is an open chamber opened to one of the head side chamber and the rod side chamber, and the other is also a head side chamber The shock absorber according to claim 3 or 4, wherein the shock absorber is a closed chamber that is not open to the rod side chamber, and the vibration suppressing device includes a throttle provided in the communication hole.

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