JP3339234B2 - Shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber used for an automobile shock absorber and the like, and more particularly, to a hydraulic shock absorber in which an electrorheological fluid is used as a working fluid and a damping force is changed by a change in viscosity. .

[0002]

2. Description of the Related Art In recent years, a hydraulic shock absorber that varies damping force by using an electrorheological fluid (hereinafter referred to as ER fluid) whose viscosity increases when a voltage or an electric field is applied thereto has been developed. I have. Hereinafter, as an example thereof,
The one disclosed in Japanese Patent No. 10983 will be described.

As shown in FIG. 10, a shock absorber a includes an inner cylinder d that accommodates a piston b and defines a cylinder chamber c, and an intermediate cylinder that surrounds the outside of the inner cylinder d with a predetermined gap e. Tube f
And an outer cylinder h which surrounds the outside of the intermediate cylinder f at a predetermined interval and partitions a reservoir chamber g with the intermediate cylinder f. Ports i and j are provided in the inner cylinder d and the intermediate cylinder f,
The ports i and j communicate the cylinder chamber c, the gap e and the reservoir chamber g, respectively. These are filled with an ER fluid k, which is a working fluid, except for the upper part of the reservoir chamber g.

When the piston b moves to the extension side, that is, upward, the ER fluid k above the piston b in the cylinder chamber c flows into the gap e through the port i, and the ER fluid k flows from top to bottom in the gap e. The movement occurs, and the movement from the inside of the gap e to the reservoir chamber g through the port j is performed. On the other hand,
Below the piston b of the cylinder chamber c, the ER fluid k from the reservoir chamber g through the passage m by opening the check valve l
Is supplied.

Conversely, when the piston b moves to the contraction side, that is, downward, the supply of the ER fluid k from the lower side of the piston b through the passage o to the upper side of the piston b of the cylinder chamber c by opening the check valve n. Done. At this time, since a large amount of the ER fluid k corresponding to the volume of the rod p is supplied, this surplus is sent into the gap e through the port i. As described above, movement from the top to the bottom in the gap e and discharge to the reservoir chamber g through the port j occur.

[0006] The inner cylinder d and the intermediate cylinder f are insulated and supported by an insulating material q and connected to electric wires s ₁ and s ₂ from a power source r, thereby applying an electric field or voltage to the gap e. Form electrodes. Therefore, the ER fluid k in this gap e
When an electric field is applied to the substrate, its viscosity increases and the damping force increases.

As described above, the damping force can be changed at high speed and continuously by the application / non-application of the electric field to the ER fluid or the strength thereof. In the absorber, it is possible to simultaneously improve the riding comfort and stability of the vehicle.

In addition, as compared with a mechanism that mechanically changes the damping force as disclosed in Japanese Patent Application Laid-Open No. 4-285541, the response is good because the structure is simple and there is no device such as an actuator that causes an operation delay. Therefore, there is an advantage that the damping force can be continuously adjusted.

The change in viscosity of the ER fluid means a change in apparent viscosity, and the viscosity itself does not change. That is, when an electric field is applied, the dispersed particles in the fluid are connected to generate a yield stress, and as a result, the viscosity only appears to increase. FIG. 11 shows the damping force characteristics when an electric field is applied and when no electric field is applied. The vertical axis represents the damping force f, and the horizontal axis represents the piston speed V. As can be seen, the damping force characteristics when an electric field is applied are obtained by shifting the damping force characteristics when no electric field is applied by a yield stress (a fluid having such characteristics is called a Bingham fluid).

[0010]

When the shock absorber is used for suspension of a vehicle, the shock absorber at the time of applying an electric field is used.
In order to increase the viscosity of the R fluid to a value at which a required damping force can be obtained, a narrow inter-electrode distance and a long and wide inter-electrode shape are required. However, the latter has limitations due to restrictions on the dimensions of the shock absorber and the increase in the number of electrodes, and the like. Therefore, the distance between the inner cylinder and the intermediate cylinder is reduced as much as possible, and the gap is reduced to 1 mm.
A narrow distance between electrodes was realized by setting the distance to about mm.

However, in this case, the narrow gap acts as a throttle for the flow of the ER fluid, and there is a disadvantage that the lower limit of the damping force characteristic when no electric field is applied cannot be reduced. Therefore, it was not possible to provide a large width with respect to the damping force characteristics when an electric field was applied, and the adjustment range of the damping force could not be widened.

In general, one of the main causes of deteriorating the riding comfort of a vehicle is a thrust-up input from an unsprung (tire) when the vehicle gets over a protrusion on a road surface. This thrust input contains high frequency components, which results in high piston speeds in the shock absorber. In order to absorb the high-frequency vibration, it is necessary to reduce the damping force generated by the shock absorber with as high a response as possible. Also, when performing skyhook damper control of a vehicle body, which is one of the control rules for improving ride comfort, there are many demands for reducing the damping force as much as possible.

However, also in this case, since a small damping force cannot be obtained, there arises a problem that sufficient vibration cannot be absorbed with respect to a thrust input.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a shock absorber which can obtain a small damping force and have a large change width in damping force characteristics. It is in.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an inner cylinder for accommodating a piston and defining a cylinder chamber, and an intermediate cylinder surrounding the inner cylinder at a predetermined interval. An electric field is applied to the gap between the shock absorber and the damping force by changing the viscosity of the electrorheological fluid as the working fluid passing through the gap. Port and a hole located in the middle of the port, and a protruding portion is formed around the hole of the intermediate cylinder to protrude toward the inner cylinder to reduce a gap with the inner cylinder. is there.

[0016]

When no electric field is applied, the electrorheological fluid in the gap is discharged through the hole in addition to the port of the intermediate cylinder by the movement of the piston. Also, when an electric field is applied, the viscosity of the electrorheological fluid around the protrusion increases more than in other parts, thereby restricting discharge from the holes.

[0017]

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

FIG. 1 is a longitudinal sectional front view showing a shock absorber according to the present invention, and its structure is substantially the same as that of the conventional example. As shown in the drawing, the shock absorber 1 surrounds an inner cylinder 4 that accommodates a piston 2 slidably and reciprocally to define a cylinder chamber 3 and a relatively small gap 5 of about 1 mm around the inner cylinder 4. An intermediate cylinder 6 and an outer cylinder 8 which surrounds the outside of the intermediate cylinder 6 at a relatively large interval and partitions a reservoir chamber 7 are provided coaxially with the intermediate cylinder 6. One end closing plate 9 made of an insulating material such as resin is provided at one end, that is, the upper end opening of the outer cylinder 8, and the other end closing plate 10 is also provided at the other end, that is, the lower end opening. A ring-shaped support member 11 made of an insulating material such as resin is provided on the upper surface of the other end closing plate 10, and both ends of the inner cylinder 4 and the intermediate cylinder 6 are insulated by this and the one end closing plate 9. Supported. One end closing plate 9 has a bearing 12
Is provided, through which the piston rod 13 protrudes.

The inner cylinder 4 is made of a conductive metal, and its lower end surface is in contact with the other end closing plate 10, and its upper end surface is flush with the upper surface of the closing plate 9 and is exposed to the outside. You. As shown in FIG. 2, the inner cylinder 4 is provided at its upper end with an inner cylinder port 14 for communicating the cylinder chamber 3 with the gap 5. Four inner cylinder ports 14 are provided at opposing positions,
It is formed in an elongated hole or slit shape along the circumferential direction of the inner cylinder 4.

The intermediate cylinder 6 is made of a conductive metal.
Has an inner diameter that is about 2 mm larger than the outer diameter of the first member, and its upper end is embedded inside the closing plate 9 and its lower end is embedded inside the supporting member 11 so as not to be exposed or abutted.

As shown in FIG. 3, the intermediate cylinder 6 is provided at its lower end with an intermediate cylinder port 15 for communicating the gap 5 with the reservoir chamber 7. This intermediate cylinder port 15 also
Four are provided at opposing positions, and are formed in an elongated hole or slit shape along the circumferential direction of the inner cylinder 4.

In particular, the intermediate cylinder 6 is provided with a plurality of holes 16 for communicating the gap 5 and the reservoir chamber 7 in addition to the intermediate cylinder port 15. The hole 16 is provided in the middle of the intermediate cylinder 6 or in the entirety thereof so as to be appropriately dispersed.
The R fluid 28 is arranged in a zigzag pattern at appropriate intervals so as to be always below the liquid level, is bored along the radial direction of the intermediate cylinder 6, and has a sufficiently small diameter compared to the outer diameter of the intermediate cylinder. . Further, as shown in detail in FIG. 4, a portion protruding toward the inner cylinder 4
And a projection 17 for reducing the gap 5 between them. The protruding portion 17 is formed in a ring shape surrounding the hole 16, a radially outer edge portion thereof is formed in a square cross-sectional shape, and a radially inner edge portion thereof is cut off in a rounded cross-sectional shape. The facing surface 18 facing the inner cylinder 4 is formed in a round shape so as to be along a concentric cylinder with the inner cylinder 4 or to keep a gap between the inner cylinder 4 and the inner cylinder 4 constant. By doing so, while the distance h ₁ of the gap 5 is set to about 1 mm, distance h ₂ of the gap 19 between the inner cylinder 4 and the surface 18, for example 0.6mm
Degree.

As a method of forming the hole 16 and the projecting portion 17, there is a method in which the projecting portion 17 is provided at the same time as the formation of the intermediate cylinder 6, and the hole 16 is formed at the center of the projecting portion 17.

As shown in FIG. 1, a power supply 20 for generating a high voltage is provided on the upper end face of the inner cylinder 4 exposed at one end from the closing plate 9.
, Or a ground line 21 is electrically connected. The positive wire 22 from the power supply 20 is inserted through the insulating tube 23 and is electrically connected to the intermediate cylinder 6. The insulating pipe 23 penetrates the outer cylinder 8 in an oil-tight manner, passes through the reservoir chamber 7 and is connected to the intermediate cylinder 6 in an oil-tight manner. Thereby, the intermediate cylinder 6
Represents a positive electrode, and the inner cylinder 4 represents a negative electrode.

The piston 2 has therein a piston flow path 24 for communicating the upper cylinder chamber 3a and the lower cylinder chamber 3b, and a piston-side check valve 25 provided at an intermediate portion of the piston flow path. Also, the other end closing plate 10
In the inside thereof, there are provided a closing plate channel 26 for communicating the lower cylinder chamber 3b and the reservoir chamber 7, and a closing plate side check valve 27 provided near the outlet of the cylinder chamber 3b. And inside the shock absorber 1 thus formed,
Except for the upper part of the reservoir chamber 7, an ER fluid 28 as a working fluid is filled. The space above the reservoir chamber 7 is a space for absorbing a change in volume caused by the movement of the piston rod 13 in and out.

Further, the power supply 20 has an output ON / OFF,
A controller 28 for controlling an output voltage value or the like is connected. The controller 28 includes a microcomputer or the like, and is connected to a sensor for detecting a running state (vehicle speed, longitudinal acceleration, lateral acceleration) of the vehicle, a sensor for detecting road surface input (unsprung acceleration, vehicle height sensor), and the like. The controller 28 outputs to the power supply 20 a command value that produces an optimal damping force from the values of these sensors, and causes the power supply 20 to output a high voltage proportional to the command value.

Next, the operation of the embodiment will be described.

First, no voltage is output from the power supply 20,
A normal state (soft state) in which no voltage or electric field is applied to the gap 5 between the intermediate cylinder 6 and the inner cylinder 4 will be described.

Referring to FIG. 1, for example, when the piston 2 moves to the extension side, that is, upward, the piston side check valve 25 is closed and the ER fluid 2 in the upper cylinder chamber 3a is closed.
8 flows into the gap 5 through the inner cylinder port 14. The ER fluid 28 moves from the top to the bottom in the gap 5, and is discharged from the gap 5 to the reservoir chamber 7 through the intermediate cylinder port 15. The ER fluid 28 is supplied to the lower cylinder chamber 3 b from the reservoir chamber 7 through the closing plate channel 26 by opening the closing plate side check valve 27.

Conversely, when the piston 2 moves to the contraction side, that is, downward, the ER fluid 28 from the lower cylinder chamber 3b through the piston flow path 24 is opened in the upper cylinder chamber 3a by opening the piston check valve 25. Is supplied. The closing plate side check valve 27 is closed. At this time, since a large amount of the ER fluid 28 is supplied by the volume of the piston rod 13, the surplus is sent into the gap 5 through the inner cylinder port 14. Then, the ER fluid 28 moves from the top to the bottom in the gap 5, that is, from the inflow side to the discharge side, and is discharged to the reservoir chamber 7 through the intermediate cylinder port 15.

As described above, in the case of this embodiment, the E
The R fluid 28 is of a one-way type that always moves from top to bottom.
6 also discharges to the reservoir chamber 7. That is, the hole 16
Causes the ER fluid 28 to leak out (leak)
Since the passage resistance of the ER fluid 28 can be reduced in the portion of the hole 16, the same effect as when the interval h _{1 of the} gap 5 is increased can be obtained, and the damping force generated by the damper 1 or the damping force can be obtained. The lower limit of the characteristics can be reduced.

Next, the state when the electric field is applied (hard state) will be described. The controller 28 controls the output of the power supply 20
When turned on, the power supply 20 outputs a voltage having an optimum value of, for example, 5 kV as an upper limit, whereby a voltage or a voltage is applied to the gap 5 between the intermediate cylinder 6 as the plus electrode and the inner cylinder 4 as the minus electrode. An electric field is applied. In this way, gap 5
The ER fluid 28 inside increases the viscosity (apparent viscosity) and increases the damping force generated by the shock absorber 1.

In particular, at this time, the interval h ₂ of the gap 19 between the projecting portion 17 and the inner cylinder 4 is smaller than the interval h ₁ of the gap 5 of the other portion, so that the viscosity of the ER fluid 28 is inversely proportional to the interval of the gap. Therefore, the viscosity of the ER fluid 28 in the gap 19 is higher than that in the gap 5. Especially, the interval h _{1 of the} gap 5 is 1
mm, since distance h ₂ is 0.6mm gap 19, it caused an increase in 1.67 times the viscosity in the gap 19. This increase in viscosity results in reduced fluidity and significantly limits or eliminates leakage through holes 16. Accordingly, the main flow of the ER fluid 28 is a flow avoiding the protruding portion 17 as shown in FIG. 5, whereby a sufficient damping force can be secured without impairing the existing performance.

As can be seen, the diameter, position, number, etc. of the holes 16 and the size, shape, etc. of the projections 17 promote the outflow of the ER fluid 28 when no electric field is applied, and limit it when the electric field is applied. Determined optimally. But the distance between the electrodes in this embodiment, i.e. distance h ₁ of the gap 5 is 1 mm, distance h ₂ of the gap 19 is set to 0.6 mm, which was optimally determined in consideration of problems such as the discharge or assembly accuracy is there. It should be noted that other values can be set depending on various conditions. Further, the shape of the hole 16 may be an ellipse other than a circle, a rectangle, or the like.

FIG. 6 shows the shock absorber of the present embodiment in which
6 is a graph for comparing damping force characteristics depending on the presence or absence of the protrusion 6 and the presence or absence of the protruding portion 17, the vertical axis indicates the damping force f, the horizontal axis indicates the piston speed V, the solid line indicates the case, and the broken line indicates no case. As shown in the drawing, the upper limit during the application of the electric field shows a slight decrease due to leakage from the hole 16, but there is almost no significant difference, whereas the lower limit clearly shows a decrease due to the action of the hole 16. In addition, by reducing the lower limit of the damping force in this manner, it is possible to provide a large change width in the damping force characteristics, which can contribute to the improvement of ride comfort and operability for automobiles, and particularly, to absorb vibration against a thrust-up input. This is extremely effective for controlling the skyhook damper of the vehicle body.

Further, the advantage of the shock absorber using the ER fluid which makes the damping force variable without having a complicated structure or deteriorating the responsiveness still remains.

Next, modified examples of the hole 16 and the projecting portion 17 will be specifically described below.

First, in the first modified example shown in FIG.
The hole 16 is formed by pushing a part of the intermediate cylinder 6 toward the inner cylinder 4 in a pinpoint manner. Then, the protruding portion is turned up, and the protruding portion is cut into a predetermined length to form the protruding portion 17. Alternatively, the hole 16 and the projecting portion 17 can be formed by cutting a part of the intermediate tube 6 toward the inner tube 4 and cutting the protruding portion. In this way, processing and production are easy, and production costs can be reduced. The gap 19 between the protruding portion 17 and the inner cylinder 4 is maintained at a constant interval as described above.

Next, in the second modification shown in FIG.
The forming method is the same as that of the first modification, except that the holes 16 and the protruding portions 17 are provided with directivity. This example is a hole 16 and the projection 17 with respect to the radial direction of the intermediate cylinder 6, in which inclined by an angle theta ₁ towards viewed from above (the one end closure plate 9 side) in the counterclockwise direction. This is gap 5
This is because the flow direction of the ER fluid 28 in the inside is taken into account. For example, depending on the positional relationship between the inner cylinder port 14 and the intermediate cylinder port 15, a circumferential component is added to the flow. In the case of the present invention, since the flow is inclined so as to coincide with the flow direction, the outflow from the hole 16 when no electric field is applied becomes smooth, and the damping force can be further reduced. Conversely, it is also possible to incline in the opposite direction to prevent outflow.

The third modification shown in FIG. 9 is similar to the third modification in that it is tilted downward. That is, the hole 16 and the protruding portion 17 are inclined so as to form an angle θ ₂ with respect to the axial direction of the intermediate cylinder 6. In the case of the above shock absorber 1, the ER in the gap 5
Since the fluid 28 always moves from the top to the bottom, this also makes the outflow from the hole 16 smooth.

The present invention is capable of various modified embodiments other than the above.

[0042]

The present invention exhibits the following excellent effects.

(1) A small damping force can be obtained, and the damping force characteristics can have a large variation range.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of a shock absorber according to the present invention.

FIG. 2 is a perspective view showing an inner cylinder.

FIG. 3 is a perspective view showing an intermediate cylinder.

FIG. 4 is a vertical sectional front view showing a hole and a protrusion.

FIG. 5 is a diagram showing a flow of an electrorheological fluid around a hole and a protrusion.

FIG. 6 is a graph showing damping force characteristics.

FIG. 7 is a longitudinal sectional front view showing a first modified example of holes and protrusions.

FIG. 8 is a vertical sectional front view showing a second modification of the holes and the protrusions.

FIG. 9 is a longitudinal sectional front view showing a third modification of the holes and the protrusions.

FIG. 10 is a longitudinal sectional front view showing a conventional shock absorber.

FIG. 11 is a graph showing general damping force characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shock absorber 2 Piston 3 Cylinder chamber 4 Inner cylinder 5 Gap 6 Intermediate cylinder 15 Port 16 Hole 17 Projection 28 Electrorheological fluid

Claims (2)

(57) [Claims] 1. An operation in which an electric field is applied to a gap between an inner cylinder accommodating a piston and defining a cylinder chamber and an intermediate cylinder surrounding the inner cylinder at a predetermined interval and passing through the gap. In a shock absorber in which the damping force is changed by changing the viscosity of an electrorheological fluid as a fluid, the intermediate cylinder is provided with a port located at the discharge side end thereof, and a hole located at the intermediate portion thereof, A shock absorber characterized in that a protruding portion which protrudes toward the inner cylinder and reduces a gap with the inner cylinder is formed in a peripheral portion of the hole of the intermediate cylinder. 2. The shock absorber according to claim 1, wherein the hole is inclined with respect to an axial direction or a radial direction of the intermediate cylinder.