JP2000179609A - Damping force adjusting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize generating damping force in a low speed area of a piston speed even when an oil temperature of a hydraulic fluid in a hydraulic shock absorber is either of high or low. SOLUTION: A damping force adjusting structure has a damping valve 7 actuated when a piston 3 slidingly moves in a cylinder 1 at a piston speed exceeding a low speed area, a choke characteristic damping part for generating damping force in a low speed area of the piston speed is provided in a bypass passage for bypassing these damping valves 7, 8, this choke characteristic damping part has a choke passage L for generating damping force of a choke characteristic, and the length of this choke passage L can be changed long or short.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force adjusting structure, and more particularly, to a damping force for adjusting a generated damping force when a piston speed is in a low speed range when a hydraulic shock absorber mounted on a vehicle expands and contracts. It relates to improvement of an adjustment structure.

[0002]

2. Description of the Related Art In a hydraulic shock absorber mounted on a vehicle and operated to expand and contract by road surface vibration, the speed of a piston sliding in a cylinder, that is, the damping force when the piston speed is in a low speed range, is controlled by the vehicle. It is important in improving the ride comfort.

[0003] By the way, the damping force when the piston speed is in a low speed region is generated by an orifice in many hydraulic shock absorbers proposed so far.

That is, as is well known, the characteristic of the damping force obtained by the orifice has a hyperbolic characteristic as shown by a solid line a in FIG. 9, so that the piston speed exceeds the low speed region and exceeds the medium speed region. At this point, the desired damping force is obtained.

However, in the low-speed range of the piston speed, that is, when the low-speed range of the piston speed is subdivided into a very low-speed range and a low-speed range exceeding the low-speed range, a sufficient rise of the damping force cannot be expected in the very low-speed range. , The damping force is what is called Darrell.

[0006] When the vehicle travels on a gentle undulating road surface, the occupant's body slowly moves up and down, that is, a so-called fluffy feeling is exhibited, which is not preferable for ride comfort. Will be.

On the other hand, if the diameter of the orifice is made smaller so as to obtain a sufficient damping force as shown by a broken line b in FIG. The damping force is excessively high in the low-speed range exceeding the low-speed range and in the middle-speed range exceeding the low-speed range, so that a so-called lumpy feeling is developed, and the riding comfort is deteriorated.

If the choke is used instead of the orifice when the piston speed is in the low speed range, the generation of a damping force having a proportional characteristic can be expected as shown by a dashed line diagram c in FIG. Will be.

That is, as is well known, when the passage area in the choke orifice not affected by the viscosity of the hydraulic oil is A, the piston speed is V, and the proportional constant is k, the damping force F becomes F = k (V / A) ² , resulting in a hyperbolic characteristic.

On the other hand, in a choke affected by the viscosity of the hydraulic oil, when the viscosity of the hydraulic oil is μ, the piston speed is V, and the proportional constant is k, the damping force F is F = k
μV and a proportional characteristic.

Therefore, if the damping force at the time when the piston speed is in the low speed region is determined by the choke, it is possible to realize a preferable damping force generation condition even when the piston speed exceeds the low speed region and becomes higher than the medium speed region. Therefore, the riding comfort in the vehicle can be improved.

[0012]

However, it is well known that the viscosity of the hydraulic oil in the hydraulic shock absorber varies depending on the level of the temperature. For example, since the oil has been in a stationary state for a long time, Comparing the case of a hydraulic shock absorber with a low temperature and the case of a hydraulic shock absorber with a high oil temperature due to expansion and contraction for a long time, the flowability of hydraulic oil in the choke differs, and Even so, the generated damping force will be different.

That is, in the case of a choke having the same dimensions, when the oil temperature is low, the viscosity of the hydraulic oil is high, so that the flow path resistance in the choke increases, so that a high damping force is generated. When the pressure is high, the viscosity of the hydraulic oil is low, so that the flow path resistance in the choke becomes small, so that a situation where a low damping force is generated is generated.

As a result, when the vehicle that has been in a stopped state for a long time starts running, if the damping force in the low-speed range of the piston speed generated by the hydraulic shock absorber is set to an optimum state, the oil When the temperature rises, there is a concern that the optimum damping force generation state cannot be achieved.

Contrary to the above, when the oil temperature rises, if the setting is made so that the optimum damping force generation state can be realized in the low-speed range of the piston speed, the optimum condition is obtained before the oil temperature rises. There is a possibility that the occurrence of a large damping force cannot be achieved.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a hydraulic shock absorber in which the operating temperature of the hydraulic oil is either high or low.
It is an object of the present invention to provide a damping force adjusting structure which makes it possible to stabilize the generated damping force in a low-speed range of a piston speed and which is optimally used for a hydraulic shock absorber for improving the riding comfort in a vehicle.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention basically provides a damping valve which operates when a piston slides in a cylinder at a piston speed exceeding a low speed range. And a choke characteristic damping section that generates a damping force in a low-speed range of the piston speed in a bypass path that bypasses the damping valve, and the choke characteristic damping section forms a choke path that generates a damping force of the choke characteristic. And the length of the choke path can be changed.

In the above basic configuration,
More specifically, it is assumed that the damping valve is set to operate when the piston speed exceeds the low speed range and becomes equal to or higher than the medium speed range.

The bypass passage is formed in a shaft center portion of a lower end fitting portion of a piston rod in which a piston for partitioning an upper oil chamber and a lower oil chamber is interposed in a cylinder. And a vertical hole that allows communication with

Further, it is assumed that the choke path is formed by a rotary valve rotatably housed in the vertical hole, and that the choke path is changed in length when the rotary valve is rotated.

At this time, the choke path is formed on the outer periphery of the rotary valve, and the length of the helical portion as the component can be changed in length, or the length of the circulating portion as the component can be changed in length. It is assumed that it becomes.

The cross-sectional shape of the choke path may be set to an arbitrary cross-sectional shape as long as it is set to have a sufficient length with respect to its cross-sectional area and function as a choke.

Therefore, in the choke characteristic damping section having the above-described choke path, when the oil from the high pressure side flows out of the bypass path, that is, when the oil flows out to the low pressure side through the choke path, the choke is performed. When the characteristic damping force is generated and the length of the choke path is changed, the generated damping force is changed in height.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. A damping force adjusting structure according to an embodiment of the present invention is a hydraulic pressure mounted on a vehicle and expanded and contracted by road surface vibration. It is said to be embodied in a shock absorber.

The damping force adjusting structure is generated in the above-mentioned hydraulic shock absorber when the speed of the piston sliding in the cylinder is in a low speed range from a very low speed to a low speed. It is described that the damping force can be adjusted in height.

That is, first, as shown in FIG. 1, the hydraulic shock absorber includes a cylinder 1 serving as a lower end member connected to an axle (not shown) side of the vehicle and a vehicle body (not shown) side of the vehicle. And a piston rod 2 as an upper end member to be connected.

The hydraulic shock absorber is slidably housed in the cylinder 1 so that the upper oil chamber R
1 and a lower oil chamber R2. The piston 3 is held in a state in which it is interposed in a lower end fitting portion (not shown) of the piston rod 2.

At this time, the piston 3 has an expansion port 3a for allowing the upper oil chamber R1 to communicate with the lower oil chamber R2, and a pressure side port 3b for allowing the lower oil chamber R2 to communicate with the upper oil chamber R1. And a main compression damping valve 4 that closes the lower end opening of the expansion port 3a so that it can be opened and closed, and a main compression damping valve 5 that closes the upper end opening of the compression side port 3b so that it can be opened and closed.

Incidentally, the main damping valves 4 and 5 on each side operate when the piston 3 slides at high speed in the cylinder 1, that is, when the piston speed is in a high speed range, and a predetermined damping valve is activated. It is set to generate force.

Next, in this hydraulic shock absorber, a disk 6 is arranged above the piston 3, and this disk 6 allows the flow of hydraulic oil to and from the inner periphery of the cylinder 1. It is held in a state of being inserted in the lower end fitting portion of the piston rod 2 like the piston 3 so as to be in series with the piston 3 while having a gap (not shown).

At this time, the disc 6 has a port 6a for allowing communication between the upper oil chamber R1 and the lower oil chamber R2, and a sub extension side for closing the upper end opening of the port 6a so that it can be opened and closed. It has a damping valve 7 and a sub-pressure-side damping valve 8 that closes the lower end opening of the port 6a so that it can be opened and closed.

Incidentally, the sub damping valves 7 and 8 on each side are activated when the piston 3 slides at a medium speed in the cylinder 1, that is, when the piston speed is in a medium speed range. Is set to generate the damping force.

In the illustrated embodiment, the compression-side damping valve 8 has an inner peripheral end fixed as in the case of the extension-side damping valve 4 and the compression-side damping valve 5 disposed on the piston 3 described above. While the outer peripheral end is set to be a flexible end, the extension side damping valve 7 is set to have an inner peripheral end as a flexible end but not an outer peripheral end as a fixed end. As with the compression-side damping valve 8, the expansion-side damping valve 7 may be set in a mode in which the inner peripheral end is a fixed end and the outer peripheral end is a flexible end.

Although not described in detail, the disk 6 is locked by a stopper 10 locked by a C-pin 9 interposed at a so-called upper end of the lower end fitting portion of the piston rod 2. The piston 3 has a piston nut 11
Is maintained in series with the disk 6 by being screwed into a predetermined position.

The damping force adjusting structure according to the present invention has a bypass (not shown) that bypasses the extension damping valve 7 as the above-described damping valve, and includes a piston speed in the bypass. It has a choke characteristic damping portion (not shown) for generating a damping force in a low speed range.

Therefore, the bypass and the choke characteristic damping section will be described below. First, the bypass is provided in the cylinder 1 via the piston 3 which partitions the upper oil chamber R1 and the lower oil chamber R2. The lower end of the lower oil chamber R is formed on the shaft core of the lower end fitting portion of the piston rod 2 to be mounted.
2 has a vertical hole 2a which is open.

The bypass passage is radially opened in the disk 6 and has an outer end formed in the upper oil chamber R1.
And a slit 2b that is radially opened at the lower end fitting portion of the piston rod 2 and faces the horizontal hole 6b and communicates with the vertical hole 2a. Have.

By the way, the above-mentioned horizontal hole 6b and slit 2b
Are set so as to be in full communication with each other via an annular groove 6c formed on the inner periphery of the disk 6.

On the other hand, the choke characteristic damping section has a choke path L which is disposed in the bypass path and generates a choke characteristic damping force, and makes the length of the choke path L variable. .

That is, first, the choke path L is formed on the outer periphery of the rotary valve 12 rotatably housed in the vertical hole 2a.
As shown in FIG. 2, a linear portion L1 extending in the axial direction of the rotary valve 12 and serving as a basic length portion, and a helical shape extending continuously from the linear portion L1 to form a variable length portion. And a spiral portion L2.

Next, the above-mentioned slit 2b is always opposed to the choke path L. Therefore, when the rotary valve 12 is rotated, as shown in FIG.
The aiming position of the slit 2b is different, and as a result, the length is set to be changed.

That is, for example, assuming that the state shown in FIG. 1 is the state indicated by reference numeral a in FIG.
The lower end of b is the upper end of the straight portion L1 and is aimed at the lower end of the spiral portion L2. At this time, the choke path L has the shortest length.

Then, when the slit 2b moves to the position indicated by the symbol b in FIG. 3 by the rotation of the rotary valve 12, the intermediate portion of the slit 2b is aimed at the intermediate portion of the spiral portion L2, At this time, the choke path L has a so-called intermediate length.

Further, when the slit 2b moves to the position shown by the reference numeral c in FIG. 3 by further rotation of the rotary valve 12, the upper end of the slit 2b is aimed at the upper end of the spiral portion L2. At this time, the choke path L has the longest length.

Incidentally, the cross-sectional shape of the choke path L is, of course, set to be substantially rectangular,
The effective length of the choke path L may be freely set as long as the effective length of the choke path L is set to have a sufficient length with respect to the cross-sectional area and function as a choke.

Regarding the number of choke roads L,
Instead of being one as in the illustrated embodiment,
Although not shown, the outer periphery of the rotary valve 12 may be formed on a so-called opposite side to be two.

In this case, the slit 2b is also formed at the lower end fitting portion of the piston rod 2 on the opposite side, as shown by the broken line in FIG. It is.

Further, the base end of the straight portion L1 of the choke path L, that is, the one end which is the lower end in the drawing communicates with a communication hole 12a formed so as to penetrate the thickness of the rotary valve 12. And communicates with the inner peripheral side of the rotary valve 12, that is, the lower oil chamber R2.

Further, the rotary valve 12
Is rotated by the rotation of a control rod 13 rotatably inserted into the shaft core of the piston rod 2. The control rod 13 is driven by an actuator (not shown) held at the upper end of the piston rod 2. Is set to rotate.

Since the rotary valve 12 is housed in the vertical hole 2a forming a bypass which is a predetermined position, the thrust washer 15 is inserted into the support ring 14 press-fitted from below into the vertical hole 2a. It is carried under intervention.

Therefore, in the choke characteristic damping section having the choke path L, when the oil from the high pressure side flows out of the bypass path, that is, to the low pressure side via the choke path L, When the length of the choke path L is changed, the generated damping force is changed in height.

That is, for example, during the extension operation in which the piston 3 rises at a low speed in the cylinder 1, the hydraulic oil from the upper oil chamber R1, which is on the high pressure side, receives the bypass passage and the choke characteristic damping portion disposed in the bypass passage. At the lower pressure chamber R2 through the choke path L at the low pressure side.

At this time, the choke characteristic damping section generates an extension side damping force of the choke characteristic (proportional characteristic) as shown by a broken line a in FIG. , The so-called extension-side damping forces having different heights are generated as shown by solid lines b and c in FIG.

By the way, conversely, at the time of the compression operation in which the piston 3 descends in the cylinder 1 at a low speed, the hydraulic oil from the lower oil chamber R2 on the high pressure side receives the bypass passage and the choke disposed in the bypass passage. The oil flows into the upper oil chamber R1 on the low pressure side via the choke path L in the characteristic damping portion, and also at this time, the length of the choke path L differs in length, so that the pressure side damping force having a different level is generated. Become.

By the way, the rotary valve 12 having the choke path L described in the embodiment shown in FIG.
The communication between the upper oil chamber R1 and the lower oil chamber R2 via the sub damping valves 7 and 8 on each side arranged on the disk 6 is set.

That is, first, in the rotary valve 12, the communication hole 12a communicating with the choke path L is provided.
Communication hole 12b of substantially the same diameter,
have.

The communicating hole 12b communicates with a communicating hole 2c formed in the lower end fitting portion of the piston rod 2 in the radial direction so as to face the communicating hole 12b.
Are connected to an annular groove 6d which is opened in the radial direction in the disk 6 so as to face the opening and is opened to the port 6a.

Therefore, for example, during the extension operation in which the piston 3 rises at a medium speed in the cylinder 1, the hydraulic oil from the upper oil chamber R 1, which is on the high pressure side, is provided on the disk 6 by the extension damping valve 7. And flows into the vertical hole 2a along the inner circumferential route of the annular groove 6d, the communication hole 2c, the communication hole 12b, and the rotary valve 12, that is, to the lower oil chamber R2. .

On the contrary, during the compression operation in which the piston 3 descends at a middle speed in the cylinder 1, the hydraulic oil from the lower oil chamber R2 on the high pressure side flows into the vertical hole 2a and the rotary valve 12 Flows into the port 6a through the route of the inner peripheral side, the communication hole 12b and the communication hole 2c, and flows into the upper oil chamber R1 via the compression side damping valve 8.

At this time, the predetermined damping force when the piston speed is in the middle speed range is generated by the sub damping valves 7 and 8 on each side.

When the piston speed is in the high speed range, the hydraulic oil passes through the main damping valves 4 and 5 on each side of the piston 3 to generate a predetermined damping force. In this case, the damping force is generated as a damping force combined with the damping force generated by the sub damping valves 7 and 8 described above.

The hydraulic shock absorber shown in FIG. 5 has a damping force adjusting structure according to another embodiment. Compared with the damping force adjusting structure according to the above-described embodiment, the choke path is different. There is a difference in the configuration of L and in the configuration of the lower end fitting portion of the piston rod 2 related thereto.

Therefore, in the following, the description will be made focusing on the part having the difference. In the other parts, the structure is the same as that of the above-described embodiment, and is the same as that in the above-described embodiment. And the detailed description thereof will be omitted.

That is, first, the choke path L is formed on the outer periphery of the rotary valve 12, but at this time, in this embodiment, as shown in FIG. A linear portion L1 extending in the direction and serving as a basic length portion, and a circulating portion L3 circulating at the upper end portion of the rotary valve 12 and being a variable length portion continuously from the linear portion L1.

Next, a communication hole 2d which is radially opened at the lower end fitting portion of the piston rod 2 and communicates with a communication hole 6b formed in the disk 6 always faces the choke path L. When the rotary valve 12 is rotated, as shown in FIG. 7, the position where the communication hole 2d is aimed with respect to the orbital portion L3 in the choke path L is different, and as a result, the length is changed. Is set.

That is, for example, when the state shown in FIG. 5 is the state shown by reference numeral a in FIG.
Is located at the upper end of the linear portion L1 and is aimed at the so-called base end of the orbital portion L3. At this time, the choke path L has the shortest length.

When the communication hole 2d moves to the position indicated by the symbol b in FIG.
The communication hole 2d is aimed at the intermediate portion of the orbital portion L3. At this time, the choke path L has a so-called intermediate length.

Further, when the communication hole 2d moves to the position indicated by reference numeral c in FIG. 7 by further rotation of the rotary valve 12, the communication hole 2d is aimed at the so-called tip of the orbital portion L3. At this time, the choke path L has the longest length.

The number of the choke paths L is not limited to one as in the illustrated embodiment, but is formed on the outer periphery of the rotary valve 12 on a so-called opposite side. It may be two.

In this case, the communication hole 2d
As a matter of course, as shown by the broken line in FIG. 5, the lower end fitting portion of the piston rod 2 is also formed on the opposite side.

Therefore, also in the case of this embodiment, in the choke characteristic damping section having the above-described choke path L, oil from the high pressure side passes through the bypass path, ie,
A damping force having a choke characteristic is generated when the choke path L flows out to the low pressure side, and the generated damping force is changed when the length of the choke path L is changed (FIG. 4). reference).

FIG. 8 shows an expanded view of a choke path L according to still another embodiment. In this embodiment, the choke path L does not have a portion serving as a basic length portion, but a variable length portion. It is assumed that only the spiral portion L4 is formed.

In the case of the choke path L, the communication holes 2d formed in the lower end fitting portion of the piston rod 2 are arranged at a plurality of positions so as to be shifted vertically in the circumferential direction and to be vertical. Will be there.

Incidentally, also in the case of this embodiment,
When the oil from the high pressure side is released to the low pressure side through the choke path L, a damping force having a choke characteristic is generated, and when the length of the choke path L is changed, the generated damping force is changed. It goes without saying.

[0075]

As described above, according to the present invention, when the piston slides in the cylinder at low speed in the hydraulic shock absorber, damping force is generated by the choke characteristic, so that the piston slides at a very low speed. It is possible to generate a predetermined damping force even when moving, and it is assumed that the length of the choke path that generates the damping force of the choke characteristic can be changed. It is possible to realize an optimal damping force generation state according to the situation.

According to the present invention, the choke path is formed on the outer periphery of the rotary valve rotatably disposed on the shaft core of the lower end fitting portion of the piston rod. This makes it easier to form an accurate choke path.

As a result, according to the present invention, it is possible to stabilize the damping force generated in the low-speed range of the piston speed regardless of whether the hydraulic oil temperature in the hydraulic shock absorber is high or low. There is an advantage that is most suitable for use in a hydraulic shock absorber for improving ride comfort in the vehicle.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view partially showing a hydraulic shock absorber embodying a damping force adjusting structure according to an embodiment of the present invention.

FIG. 2 is a front view showing the rotary valve in FIG. 1;

FIG. 3 is an expanded view showing a choke path in the rotary valve of FIG. 2;

FIG. 4 is a characteristic diagram showing a state of generation of a damping force with respect to a piston speed by the damping force adjusting structure of the present invention.

FIG. 5 is a diagram showing a hydraulic shock absorber embodying a damping force adjusting structure according to another embodiment, similarly to FIG. 1;

FIG. 6 is a front view showing the rotary valve in FIG. 5;

7 is an expanded view of a choke path in the rotary valve of FIG. 6;

FIG. 8 is a development view of a choke road according to another embodiment.

FIG. 9 is a characteristic diagram showing a state of generation of a damping force with respect to a piston speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston rod 2a Vertical hole which constitutes a bypass passage 2b Slit which constitutes a bypass passage 2c, 2d, 12a, 12b Communication hole 3 Piston 3a Expansion port 3b Compression port 4,7 Expansion port damping valve 5,7 Damping valve Reference Signs List 8 Compression side damping valve as a damping valve 6 Disc 6a Port 6b Side hole constituting a bypass passage 6c Annular concave groove constituting a bypass passage 6d Annular groove 9 C pin 10 Stopper 11 Piston nut 12 Rotary valve 13 Control rod 14 Support ring 15 Thrust Washer L Choke path L1 Straight part forming a choke path L2, L4 Spiral part forming a choke path L3 Circular part forming a choke path R1 Upper oil chamber R2 Lower oil chamber

Continued on the front page (72) Inventor Tomoya Shimose 2-4-1 Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Industry Co., Ltd. F-term (reference) 3J069 AA50 CC13 EE28 EE37

Claims (1)

[Claims] 1. A damping valve which operates when a piston slides in a cylinder at a piston speed exceeding a low speed range, and generates a damping force in a low speed range of the piston speed in a bypass which bypasses the damping valve. Having a choke characteristic damping portion, the choke characteristic damping portion having a choke path for generating a damping force of the choke characteristic,
A damping force adjusting structure characterized in that the length of the choke path can be changed.