JP2006336713A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lessen the input into a vehicle and to prevent driving comfort from worsening. <P>SOLUTION: A shock absorber is provided with a mass body 5 slidably arranged in the axial direction along a piston rod 4, a first elastomer 6 arranged between an end face at a vehicle side setting point side of the mass body 5 and a stopper fixed to a predetermined position of the longitudinal direction of the piston rod 4, and a second elastomer 7 swingably arranged between an end face at a piston side of the mass body 5 and a swing stopper 8c in the axial direction of the piston rod 4. The piston 8 has a damping force regulating passage 8b for adjusting the damping force. The swing stopper 8c is arranged to block the damping force regulating passage 8b in the position of the mass body 5 side of the piston 8. The mass of the mass body 5 and the spring constants of the first elastomer 6 and the second elastomer 7 are set so that the characteristic frequency of a vibration system composed of the mass body 5, the first elastomer 6 and the second elastomer 7 conforms to the characteristic frequency of a vibration system composed of the piston rod 4, the piston 8 and an elastic support member 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a shock absorber, and more particularly to a shock absorber in which a damping force is reduced to improve riding comfort when a wheel passes over a protrusion on a road surface.

As a conventional shock absorber, Patent Document 1 proposes a shock absorber in which a needle and an armchair, which are slidable mass bodies that change the cross-sectional area of a flow path, are elastically supported by a spring.
In this conventional example, in a shock absorber in which the damping force is variable by controlling the flow area of the working fluid communicating with the upper and lower surfaces of the piston, the pressure in the pilot space exceeds the set pressure of the servo valve and the servo valve is The difference in pressure applied to the two faces of the open main valve causes the main valve to move to the pilot space side, increasing the flow area of the main passage, and the acceleration and deceleration of the piston to the armature and main valve of the proportional magnet The applied inertial force in one direction moves the servo valve and the main valve in the opening direction to increase the flow passage area of the main passage. In other words, it has a mechanism that generates a damping force due to the viscous resistance between the fluid and the flow path through which the viscous fluid moves due to the expansion and contraction of the shock absorber. The damping force is reduced by increasing the movement.
Japanese Patent Laid-Open No. 2-85535

However, in the conventional shock absorber described above, the natural frequency determined by a vibration system in which the piston and piston rod of the shock absorber are mass bodies and the elastic support member (upper mount) that supports the piston rod on the vehicle body side is the elastic body. When the frequency of the external force input to the shock absorber matches, the piston and the piston rod vibrate greatly due to the resonance phenomenon. Therefore, in the above prior art structure, the mass of the needle, armor chair, and proportional magnet is added to the piston and the piston rod, so the amplitude due to the resonance of the piston and the piston rod is further increased, and as a result, the input to the vehicle body is increased. Deteriorate riding comfort. In addition, when resonance occurs, the needle and armor chair, which are mass bodies, vibrate, and as a result, the cross-sectional area of the flow path that adjusts the magnitude of the damping force will fluctuate, making the damping force unstable and riding comfort. There is a problem of worsening.
The present invention has been made in view of the above-described circumstances, and by reducing the amplitude due to resonance of the piston and the piston rod, it is possible to reduce the input to the vehicle body and to avoid the deterioration of riding comfort. The aim is to provide a shock absorber.

  In order to solve the above problems, a shock absorber according to the present invention includes an outer cylinder filled with hydraulic fluid, a piston slidably inserted in the outer cylinder and provided with a hydraulic fluid flow path, and one end of the piston. A shock absorber configured to include a piston rod coupled to a piston and having the other end coupled to a vehicle body side attachment point via an elastic support member. The shock absorber is configured to be slidable in the axial direction along the piston rod. A mass body, a first elastic body disposed between an end surface of the mass body on the vehicle body side attachment point side and a stopper fixed at a predetermined position in a longitudinal direction of the piston rod, and the mass body A second elastic body disposed between an end face on the piston side of the piston rod and a rocking stopper capable of rocking in the axial direction of the piston rod, and the piston is separate from the flow path of the hydraulic fluid, Adjust the damping force A damping force adjusting flow path, wherein the swing stopper is disposed so as to close the damping force adjusting flow path at a position on the mass body side of the piston, and the mass body and the first elastic body The natural frequency of the vibration system composed of the second elastic body matches the natural frequency of the vibration system composed of the piston rod, the piston, and the elastic support member. A mass and a spring constant of the first elastic body and the second elastic body are set.

  According to this configuration, the mass body that is slidable in the axial direction along the piston rod includes the lower portion of the first elastic body whose upper portion is in contact with the stopper and the lower portion whose lower portion is in contact with the swing stopper. Since it is arranged in a state of being sandwiched between the upper parts of the two elastic bodies, the inertial force of the mass body is generated in the direction of the vehicle body (upward in the figure) when overriding the protrusion, and this causes the damping force adjusting flow path to It is opened and the damping force is reduced, and the ride comfort can be improved.

  Further, the oscillation stopper is disposed so as to block the damping force adjusting flow path at the position on the mass body side of the piston, and the natural frequency of the vibration system constituted by the mass body, the first elastic body, and the second elastic body. The mass of the mass body and the spring constants of the first elastic body and the second elastic body are set so as to match the natural frequency of the vibration system composed of the piston rod, the piston, and the elastic support member. Therefore, for the resonance of the piston and the piston rod, the vibration system composed of the mass body, the first elastic body, and the second elastic body functions as a dynamic damper. Can be small.

  As described above, according to the configuration of the present invention, when the projection is overridden, the damping force adjusting flow path is opened by the inertial force of the mass body, the damping force is reduced, and the riding comfort can be improved. Furthermore, the amplitude due to the resonance of the piston and the piston rod can be reduced. As a result, the input to the vehicle body can be reduced, and the damping force adjusting flow path can be kept closed even during the resonance. It is possible to produce an effect that deterioration of riding comfort can be avoided.

Hereinafter, a shock absorber according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a configuration of a shock absorber according to an embodiment of the present invention.
First, the structure will be described. The shock absorber S is basically the same as a conventionally known shock absorber, and includes an outer cylinder 2, a piston 8, and a piston rod 4.

The outer cylinder 2 is filled with a working fluid that is a viscous fluid.
The piston 8 has an outer diameter substantially equal to the inner diameter of the outer cylinder 2, is slidably inserted into the outer cylinder 2, and includes a normally-open hydraulic fluid flow path 8 a.
The piston rod 4 has a lower end connected to the piston 8 and an upper end connected to the attachment point 1 a on the vehicle body 1 side via the elastic support member 3. A stopper 4b having an inner diameter substantially the same as the outer diameter of the piston rod 4 is fixed to the piston rod 4, and a swinging stopper capable of swinging in the axial direction of the piston rod 4 is located near the piston 8 side of the piston rod 4. 8c is provided.

The shock absorber S of the present invention includes a mass body 5, a first elastic body 6, and a second elastic body 7.
The mass body 5 is disposed between the stopper 4b and the swing stopper 8c so as to be sandwiched between the first elastic body 6 and the second elastic body 7 in the vertical direction, and extends in the axial direction along the piston rod 4. It is slidably arranged. The shape of the mass body 5 is formed in a streamline-like shape in which the outer diameter gradually increases from the both end portions toward the central portion.

The first elastic body 6 is a coil spring externally fitted to the piston rod 4, and is disposed between the mass body 5 and the stopper 4b, and has a lower end fixed to the mass body 5 and an upper end fixed to the stopper 4b.
The second elastic body 7 is a coil spring that is externally fitted to the piston rod 4, and is disposed between the mass body 5 and the swing stopper 8c, and has an upper end fixed to the mass body 5 and a lower end fixed to the swing stopper 8c. Yes.

The piston 8 has a damping force adjusting channel 8b for adjusting the damping force at a position inside the hydraulic fluid channel 8a, separately from the hydraulic fluid channel 8a. Except when the mass body 5 is largely moved to the position on the piston 8 side, the damping force adjusting flow path 8b is blocked by the swing stopper 8c at the position on the mass body 5 side of the piston 8. ing.
Further, the rigidity of the second elastic body 7 is made larger than the rigidity of the first elastic body 6, and the force generated by the inertial force generated in the mass body 5 and the pressure difference between the upper chamber and the lower chamber of the piston 8. Is larger than the preload generated by the first and second elastic bodies 6 and 7.

Further, the natural frequency of the vibration system composed of the mass body 5, the first elastic body 6, and the second elastic body 7 is the natural frequency of the vibration system composed of the piston rod 4, the piston 8, and the elastic support member 3. The mass of the mass body 5 and the spring constants of the first elastic body 6 and the second elastic body 7 are set so as to coincide with the frequency.
The stopper 4b, the mass body 5, the swing stopper 8c, the first elastic body 6, and the second elastic body 7 are covered with a cover 4c.
FIG. 2 is a plan view showing the configuration of the swing stopper.
The swing stopper 8c is configured to have a through hole 8d at a location other than the portion blocking the damping force adjusting flow path 8b.

Next, the operation of this embodiment will be described.
The mass body 5 is formed in a streamline-like shape in which the outer diameter gradually increases as it approaches the center portion from both ends, so that the mass body 5 disposed in the working fluid that is a viscous fluid is moved. The accompanying viscous resistance can be reduced, and the mass body 5 can move quickly.
If the rigidity of the second elastic body 7 is smaller than that of the first elastic body 6, the first elastic body 6 and the second elastic body 7 may delay the movement of the swing stopper 8 c relative to the movement of the mass body 5. Alternatively, only the mass body 5 moves and the damping force reduction function deteriorates. However, if the rigidity of the second elastic body 7 is larger than the rigidity of the first elastic body 6, the first elastic body 6 and The natural frequency determined by the rigidity of the second elastic body 7 and the mass of the mass body 5 matches the natural frequency of the vibration system composed of the piston rod 4 and piston 8 and the elastic support member 3 on the vehicle body 1 side. It is possible to set the swing stopper 8c along with the movement of the mass body 5 so that the damping force can be reduced more quickly.

  Further, the natural frequency of the vibration system composed of the mass body 5, the first elastic body 6, and the second elastic body 7 is the natural frequency of the vibration system composed of the piston rod 4, the piston 8, and the elastic support member 3. Since the frequency matches the frequency, the vibration system composed of the mass body 5, the first elastic body 6, and the second elastic body 7 functions as a dynamic damper for the resonance of the piston 8 and the piston rod 4. Therefore, the amplitude due to the resonance of the piston 8 and the piston rod 4 can be reduced. As a result, the input to the vehicle body 1 can be reduced, and the damping force adjusting flow path 8b remains closed even during the resonance. It can be maintained, and deterioration of riding comfort can be avoided. That is, when the wheel passes over the protrusion on the road surface, the inertial force of the mass body 5 is generated in the vehicle body direction (upward in the figure), thereby opening the damping force adjusting flow path 8b, and the wheel gets over the protrusion and returns to the original state. When returning to the height of the vehicle, the damping force becomes smaller and the riding comfort can be improved.

  The cover 4c is a process of generating a damping force which is an original function, and a flow of hydraulic fluid is generated around the piston 8, and depending on the size of the flow, a displacement occurs in the mass body 5 and a damping force adjusting flow is generated. The path 8b opens and closes, and the damping force may fluctuate and ride comfort may deteriorate. However, according to this configuration, the damping force adjusting flow path 8b is opened by the flow of the hydraulic fluid, and the damping force is reduced. It is unlikely to fluctuate and deteriorate riding comfort.

  The rocking stopper 8c needs to move together with the mass body 5 without following the piston rod 8 when the protrusion is passed over. However, the rocking stopper 8c is disposed in the working fluid that is a viscous fluid. For this reason, viscous resistance is generated with movement. However, in this embodiment, as shown in FIG. 2, by having this through hole 8d, it can move without following the piston rod 8, and the viscous resistance can be reduced.

FIG. 3 is a diagram showing a state when no vibration is input from the outside.
As shown in the figure, the damping force adjusting flow path 8b is closed by a swing stopper 8c unless there is an input from the outside. That is, the swing stopper 8 c closes the damping force adjusting flow path 8 b by preload (load toward the piston 8) by the first elastic body 6 and the second elastic body 7.

FIG. 4 is a diagram for explaining the operation when overriding a protrusion.
When the sum of the force generated in the mass body 5 due to the vertical input acceleration when riding over the protrusion and the force generated by the pressure difference between the upper chamber and the lower chamber of the piston 8 is larger than the preload, the swing stopper 8c is The second elastic body 7 lifts the damping force adjusting flow path 8b.
That is, at the time of overriding the protrusion, (the inertial force of the mass body 5 + the force generated by the pressure difference between the viscous fluid in the upper chamber and the lower chamber)> preload is satisfied.
Here, as described above, if the rigidity of the second elastic body 7 is made larger than the rigidity of the first elastic body, the swing stopper 8c follows the piston rod 8 as the mass body 5 moves. It can be moved without.

FIG. 5 is a diagram for explaining the operation at the time of rod resonance.
Regarding the movement of the mass body 5 at the time of the rod resonance, the force generated in the mass body 5 due to the input acceleration at the time of the rod resonance is generally smaller than that at the time of overriding the protrusion, and preloading is performed so that the swing stopper 8c does not lift By acting, the mass body 5 forms a vibration system supported by the first elastic body 6 and the second elastic body 7 in the piston rod 4.

FIG. 6 is a schematic diagram showing a mechanical model of the shock absorber of the present invention.
As easily understood from the mechanical model of FIG. 6, at the time of rod resonance, the dynamic damper effect of the mass body 5 is generated, and the rod resonance gain is reduced. That is, the natural frequency of the vibration system constituted by the mass body 5, the first elastic body 6, and the second elastic body 7 is a vibration constituted by the piston rod 4, the piston 8, and the elastic support member 3 on the vehicle body side. By setting the mass of the mass body 5 and the spring constants of the first elastic body and the second elastic body so as to coincide with the natural frequency of the system, the mass body 5, the first elastic body 6, the second elastic body 7, Since the vibration system constituted by the above functions as a dynamic damper, the amplitude due to the resonance of the piston 8 and the piston rod 4 can be reduced. As a result, the input to the vehicle body can be reduced and the damping force can be adjusted. The use flow path 8b can be kept closed even at the time of resonance, and deterioration of riding comfort can be avoided.

FIG. 7 is a graph showing the dynamic damper effect of the mass body of FIG. The conventional example is indicated by a dotted line, and the present invention is indicated by a solid line.
In this graph, frequency (Frequency) [Hz] is plotted on the horizontal axis and gain (GAIN) [dB] is plotted on the vertical axis, and the conventional example and the present invention are compared.
As shown in the figure, for the resonance of the piston 8 and the piston rod 4, the vibration system composed of the mass body 5, the first elastic body 6 and the second elastic body 7 functions as a dynamic damper. Rod resonance gain is low. That is, according to the shock absorber S of the present invention, the amplitude due to the resonance of the piston 8 and the piston rod 4 can be reduced. As a result, the input to the vehicle body can be reduced and the damping force adjusting flow path can be reduced. 8b can be kept closed even at the time of resonance, and deterioration of riding comfort can be avoided.

FIG. 8 is a longitudinal sectional view showing a configuration of a shock absorber according to another embodiment of the present invention.
This example is different from the embodiment described with reference to FIG. 1 in that the piston rod 4 and the cover 4c described above are integrally molded to form the piston rod 40, and the stopper 4b in the vicinity of the piston rod 4 is omitted. The structure is the same as that of the embodiment shown in FIG. 1, but the piston rod 4 is formed so as to cover the mass body 5, the swing stopper 8 c, the first elastic body 6, and the second elastic body 7. In the vicinity of the piston 8 of the piston rod 40, a flow path 4a is provided. That is, the mass body 5, the swing stopper 8 c, the first elastic body 6, and the second elastic body 7 are part of the piston rod 4 in which a cavity is formed from a predetermined position to the piston 8 and the piston 8 side is opened. Covered by. That is, the piston rod 4 also serves as the cover 4c in the embodiment described above with reference to FIG. 1. Even with this configuration, the damping force adjusting flow path 8b remains closed by the swing stopper 8c, and the riding comfort deteriorates. Can be avoided.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various change is possible without deviating from the meaning of this invention.
For example, in the above-described embodiment, the first elastic body 6 and the second elastic body 7 are coil springs. However, the present invention is not limited to this, and other elastic bodies such as a leaf spring can be used.

Further, in the embodiment shown in FIG. 8 described above, the shape of the cover-like piston rod 40 is formed in a substantially cylindrical shape in the drawing. However, like the cover 4c shown in FIG. As the diameter approaches 8, the outer diameter can be gradually increased.
Further, in the embodiment described above, the shape of the mass body 5 is formed in a streamlined shape so that the outer diameter increases as it approaches the center from both ends. Are equal in outer diameter, but the outer diameters at both ends may be different.

It is a longitudinal cross-sectional view which shows the structure of the shock absorber which concerns on embodiment of this invention. It is a top view which shows the structure of a rocking | fluctuation stopper. It is a figure which shows a state when the vibration is not especially input from the outside. It is a figure explaining the operation | movement at the time of protrusion protrusion. It is a figure explaining the operation | movement at the time of rod resonance. It is the schematic which shows the mechanical model of the shock absorber of this invention. It is a graph which shows the dynamic damper effect of a mass body. It is a longitudinal cross-sectional view which shows the structure of the shock absorber which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle body, 2 ... Outer cylinder, 3 ... Elastic support member, 4 ... Piston rod, 4a ... Flow path, 4b ... Stopper, 4c ... Cover, 5 ... Mass body, 6 ... 1st elastic body, 7 ... 2nd elasticity Body, 8 ... piston, 8a ... flow path, 8b ... damping force adjusting flow path, 8c ... swing stopper, 8d ... through hole, 40 ... piston rod (cover shape)

Claims (7)

An outer cylinder filled with the hydraulic fluid, a piston slidably inserted in the outer cylinder and provided with a hydraulic fluid flow path, one end connected to the piston and the other end via an elastic support member A shock absorber configured to include a piston rod coupled to a side attachment point,
A mass body slidably disposed in the axial direction along the piston rod;
A first elastic body disposed between an end surface of the mass body on the vehicle body side attachment point side and a stopper fixed at a predetermined position in a longitudinal direction of the piston rod;
A second elastic body disposed between an end face on the piston side of the mass body and a swing stopper capable of swinging in the axial direction of the piston rod;
With
The piston has a damping force adjusting flow path for adjusting the damping force separately from the hydraulic fluid flow path, and the swing stopper is used for adjusting the damping force at a position on the mass body side of the piston. A natural frequency of a vibration system arranged so as to close the flow path and configured by the mass body, the first elastic body, and the second elastic body is determined by the piston rod, the piston, and the elastic support member. A shock absorber, wherein the mass of the mass body and the spring constants of the first elastic body and the second elastic body are set so as to coincide with the natural frequency of the vibration system to be configured.   The shock absorber according to claim 1, wherein the mass body is formed such that an outer diameter gradually increases from both ends toward the center.   The shock absorber according to claim 1 or 2, wherein the swing stopper has a through-hole in the axial direction at a place other than a portion blocking the damping force adjusting flow path.   The mass body, the swing stopper, the first elastic body, and the second elastic body are covered with a cover that is open on the piston side. The shock absorber according to item.   The mass body, the swing stopper, the first elastic body, and the second elastic body are formed between a predetermined position and the piston, and the cavity in the piston rod is open on the piston side. The shock absorber according to claim 1, wherein the shock absorber is covered with a shock absorber.   The shock absorber according to any one of claims 1 to 5, wherein the rigidity of the second elastic body is larger than the rigidity of the first elastic body.   The preload applied to the mass body by the first and second elastic bodies is between the inertia force generated in the mass body when the wheel gets over the protrusion on the road surface and the upper chamber and the lower chamber of the piston. The shock absorber according to any one of claims 1 to 6, wherein the shock absorber is smaller than a sum of forces generated by a pressure difference.

Images