JP3790633B2 - Hydraulic shock absorber for air suspension - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic shock absorber used for automobiles, industrial vehicles, and the like, and more particularly to a damping force variable mechanism suitable for an air suspension hydraulic shock absorber.
[0002]
[Prior art]
The hydraulic shock absorber for the air suspension shown in FIG. 4 has a gas spring G, one end connected to the outer cylinder side of the damper Ao and the other end connected to the piston rod PR side, integrally assembled to the damper Ao. Thus, the weight of the vehicle body is supported by the gas spring G, and the vibration of the vehicle is damped by the damper Ao. The air suspension can adjust the vehicle height by changing the gas pressure of the gas spring G when the sprung weight consisting of the weight of the vehicle body and the loading load changes due to the increase or decrease of the loading load of passengers or luggage. .
[0003]
At this time, when the gas pressure of the gas spring G is increased, the spring constant also increases. On the other hand, even if the sprung weight and the spring constant change, if the relationship of the generated damping force with respect to the expansion / contraction speed of the damper Ao (hereinafter referred to as damping force-speed characteristic) remains constant, the riding comfort of the vehicle will not exceed the target value. It will be lost. In order to prevent this, it is necessary to change the damping force-speed characteristic according to the gas pressure.
[0004]
The specific change of the damping force-speed characteristic is an damping force adjusting actuator AJ (hereinafter abbreviated as actuator AJ) controlled by the output of the controller based on signals from various sensors arranged at important points of the vehicle body. The rotary valve RV coupled to the lower end of the control rod CR is rotated to open and close a bypass oil passage BP provided in parallel with the piston valve PV.
[0005]
When the bypass oil passage BP is in communication, the soft valve SV is composed of SVe that generates an expansion-side damping force in a soft extension stroke and SVc that generates a compression-side rear damping force in a soft contraction stroke. (Hereinafter, abbreviated as soft valve SV) is selected, and a soft mode for generating a low damping force as indicated by S in FIG. 3 is set.
On the other hand, when the bypass oil passage BP is shut off, HVe that generates a large deflection stroke in the hard extension stroke with a large flexural rigidity and a contraction side HVc that generates the compression side rear damping force in the hard contraction stroke. A hard valve HV (hereinafter abbreviated as a hard valve HV) is selected, and a hard mode for generating a high damping force as indicated by H in FIG.
[0006]
Here, the compression-side back damping force of the contraction stroke when the soft valve SV is selected is combined with the compression-side base damping force generated by the base valve BV attached to the lower end of the cylinder CY, and the compression-side damping in the soft mode. It becomes power.
Similarly, the compression-side back damping force in the contraction stroke when the hard valve HV is selected is combined with the base damping force generated by the base valve BV to become the compression-side damping force in the hard mode.
[0007]
As described above, the communication and blocking of the bypass oil passage BP is controlled by the output of the controller based on signals from various sensors arranged at key points of the vehicle body, and the soft mode or the hard mode is automatically set according to the loaded load. This makes it possible to maintain a good ride comfort.
[0008]
[Problems to be solved by the invention]
The actuator AJ in the conventional product is driven as necessary by the controller based on signals from various sensors (not shown), and thus the various sensors and the attached devices such as the controller are necessary.
In addition, in order to change the damping force-speed characteristic, an actuator AJ for selecting the soft valve SV or the hard valve HV is necessary, and there is a problem that the damping force adjusting device becomes greatly complicated. It was.
[0009]
Furthermore, in order to change the damping force-velocity characteristics, a bypass oil passage BP is provided in the piston portion and is opened and closed via the control rod CR. Therefore, a hollow hole is processed in the piston rod PR, and the hollow hole is controlled. There was also a problem that the rod CR and the rotary valve RV had to be mounted.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air suspension hydraulic shock absorber that simplifies the structure of the damping force adjustment system and the damper of the air suspension. is there.
[0010]
[Means for Solving the Problems]
The present invention provides a “cylinder, a piston rod having one end coupled to a piston that divides the cylinder into an upper chamber and a lower chamber and the other end connected to the vehicle body side, and a rod guide that slidably guides the piston rod. And a rod guide and an outer cylinder that accommodates the cylinder. A reservoir is formed between the cylinder and the outer cylinder, and a lower end portion of the outer cylinder is connected to the wheel side, and the piston slides. The air suspension hydraulic pressure has a damper formed so as to generate a predetermined damping force, and a gas spring having one end connected to the outer cylinder side of the damper and the other end connected to the piston rod side. It is premised on a “buffer”.
[0011]
In order to solve the above-mentioned problem, the means adopted by the present invention is that "a relief valve made of a leaf valve is opposed to an annular window on the upper surface of the rod guide communicating with the upper chamber of the cylinder, while the gas spring of the gas spring is A push rod is inserted into a partition wall that accommodates the upper chamber of the ring nut communicated with the lower valve chamber of the ring nut that accommodates the relief valve and communicates with the reservoir, and the pressure difference between the upper and lower chambers causes the push rod to pass through the push rod. The damping force is changed in response to the pressure in the gas chamber corresponding to the load on the vehicle body side by urging the leaf valve from the back and controlling the relief pressure.
[0012]
By reducing the passage area of the communication hole of the ring nut that communicates the gas chamber of the gas spring and the upper chamber of the ring nut, the damping force against slow pressure fluctuations of the gas chamber, such as when adjusting the vehicle height. However, the damping force does not change in response to a severe change in the pressure of the gas spring such as vibration during vehicle travel, so that the riding comfort during travel can be stabilized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Since the basic structure for assembling the gas spring G to the damper Ad is the same as that of the prior art, the present invention will be described by extracting only the vicinity of the rod guide indicated by Z in FIG.
The piston valve PV provided in the piston portion P of the damper Ad mainly generates a damping force in the extension stroke, and is not provided with a damping force variable mechanism that changes the damping force-speed characteristic. Further, the base valve BV at the bottom generates a damping force for the contraction stroke. The upper chamber A, the lower chamber B, and the lower portion of the reservoir R in the hydraulic shock absorber are filled with hydraulic oil.
[0014]
First, the first embodiment shown in FIG. An annular window 4D communicating with the upper chamber A of the damper Ad via the inner passage 4A of the rod guide 4 is guided by the valve guide 5 and an inner peripheral lower end surface of the valve guide and an inner peripheral upper end surface of the rod guide 4 A relief valve composed of a leaf valve 6 sandwiched between the two is opposed. The leaf valve is a hydraulic oil to the lower chamber 9C of the ring nut 9 that communicates with the reservoir R formed between the cylinder 2 and the outer cylinder 3 from the upper chamber A side of the damper Ad through the outer passage 4B of the rod guide. Only allow spillage.
[0015]
In addition to its own rigidity, the leaf valve 6 has a pressing force obtained by multiplying the cross-sectional area of the small-diameter portion 8A of the push rod 8 by (the gas pressure Pg of the gas spring G−the internal pressure Pn of the lower chamber 9C of the ring nut). 7 to control the relief pressure from the upper chamber A side of the damper Ad to the lower chamber 9C of the ring nut.
Here, the spacers 7 are for uniformly applying the pressing force of the push rods 8 distributed in several places on the concentric circles to the leaf valve 6 and may be omitted if the number of dispersions is large.
[0016]
The small diameter portion 8A of the push rod penetrates the partition wall between the upper chamber 9B and the lower chamber 9C of the ring nut, receives the gas pressure Pg of the gas spring G at the upper end surface, and the reservoir at the lower end surface via the outer passage 4B of the rod guide. The inner pressure Pn of the lower chamber 9C of the ring nut communicating with R is received.
[0017]
Next, the operation will be described.
When the loaded load is heavy and the sprung weight is large, the gas pressure Pg of the gas spring G is increased in order to maintain a predetermined vehicle height, so that the spring constant increases. When the gas pressure Pg of the gas spring G increases, the pressure of the upper chamber 9B of the ring nut that communicates with the gas chamber Gc of the gas spring G via the communication hole 9A of the ring nut also increases. As a result, the differential pressure expressed by (gas pressure Pg of the gas spring G−inner pressure Pn of the lower chamber 9C of the ring nut) increases, so that the pressing force of the push rod 8 that urges the leaf valve 6 from the back surface increases. Then, the relief pressure from the upper chamber A of the damper Ad to the lower chamber 9C of the ring nut increases. For this reason, since the pressure in the upper chamber A of the damper becomes high, the extension side damping force in the extension stroke becomes high.
[0018]
As a result of the increased relief pressure, the pressure in the upper chamber A facing the reservoir R together with the lower chamber B in which the base valve BV is mounted increases, so the compression side damping force also increases. That is, it is possible to automatically obtain a high damping force as illustrated in H of FIG. 3 for detecting the gas pressure Pg of the gas spring G by adjusting the vehicle height and maintaining the ride comfort of the target vehicle. Become.
[0019]
When the loaded load is light and the sprung weight is small, the gas pressure Pg of the gas spring G is lowered to maintain the vehicle height, so the spring constant becomes small. When the gas pressure Pg of the gas spring G becomes low, the differential pressure expressed by (the gas pressure Pg of the gas spring G−the internal pressure Pn of the lower chamber 9C of the ring nut) becomes small. From the upper chamber A of the damper Ad to the lower chamber 9C of the ring nut becomes lower. For this reason, the pressure of the upper chamber A becomes low, and the extension side damping force of the extension stroke becomes low.
[0020]
As a result of the lowering of the relief pressure, the pressure in the upper chamber A facing the reservoir R together with the lower chamber B in which the base valve BV is mounted is also lowered, so the compression side damping force is also lowered.
That is, it is possible to automatically obtain a low damping force as illustrated in S of FIG. 3 for detecting the gas pressure Pg of the gas spring G by adjusting the vehicle height and maintaining the riding comfort of the target vehicle. Become.
[0021]
Since the actual loaded load varies depending on the time and the case, the damping force changes between the high damping force H and the low damping force S illustrated in FIG.
As described in detail above, on both the expansion side and the contraction side, it is possible to sense the gas pressure Pg of the gas spring G by adjusting the vehicle height and automatically obtain the necessary damping force-speed characteristics.
[0022]
Next, a second embodiment shown in FIG. 2B will be described.
The difference from the first embodiment is that the passage area of the communication hole 19A of the ring nut that connects the gas chamber Gc of the gas spring G and the upper chamber 19B of the ring nut 19 is reduced. When the pressure in the gas chamber Gc changes slowly at a low frequency, the pressure in the upper chamber 19B of the ring nut 19 changes almost simultaneously with the gas chamber Gc because there is almost no throttling effect of the small diameter communication hole 19A.
[0023]
However, when the pressure in the gas chamber Gc pulsates at a high frequency, such as vibration caused by rough road travel, the pulsating pressure is leveled by the throttling effect of the small diameter communication hole 19A, and the pressure in the upper chamber 19B of the ring nut 19 is increased. The fluctuation will be smaller.
As a result, the damping force-speed characteristic changes correspondingly to the slow pressure fluctuation of the gas chamber Gc as in the vehicle height adjustment, but the intense gas chamber Gc such as vibration caused by running on a rough road. It does not change with respect to fluctuations in pressure. For this reason, the ride comfort at the time of driving | running | working can be stabilized.
[0024]
【The invention's effect】
As described above in detail, according to the present invention, the annular window of the rod guide communicating with the upper chamber of the damper is urged by the pressing force of the bush rod acting on the differential pressure between the gas spring and the upper chamber of the damper. Since the relief valve is made to face and the relief pressure from the upper chamber of the damper is made to respond to the pressure of the gas spring, the pressure of the gas spring can be sensed by adjusting the vehicle height and the necessary damping force-speed characteristics can be obtained automatically. it can. Further, since various sensors and controllers or actuators are not required, the structure of the air suspension hydraulic shock absorber is simplified, and the damping force adjustment system can be simplified.
Furthermore, since the adjusting portion for the damping force-speed characteristic is integrated in the rod guide portion, the conventional adjusting portion for the damping force-speed characteristic of the piston portion becomes unnecessary. For this reason, since a rotary valve coupled to the control rod is not required and the hollow hole processing of the piston rod can be eliminated, a significant cost reduction can be achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a hydraulic shock absorber for an air suspension according to the present invention.
FIG. 2A is a cross-sectional view of the vicinity of a rod guide according to a first embodiment of the present invention.
(B) It is sectional drawing of the rod guide vicinity which concerns on 2nd Embodiment of this invention.
FIG. 3 is an explanatory diagram showing a damping force that changes in response to the pressure of a gas spring.
FIG. 4A is a cross-sectional view of a conventional hydraulic shock absorber for an air suspension.
(B) It is an expanded sectional view of the piston vicinity.
[Explanation of symbols]
A Upper chamber B Lower chamber P Piston R Reservoir G Gas spring Gc Gas chamber Ad Damper 1 Piston rod 2 Cylinder 3 Outer cylinder 4 Rod guide 4D Annular window 6 Leaf valve (Relief valve)
8 Push rod 9, 19 Ring nut 9A, 19A Ring nut communication hole 9B, 19B Ring nut upper chamber 9C, 19C Ring nut lower chamber

Claims (2)

A cylinder, a piston rod having one end coupled to a piston partitioning the cylinder into an upper chamber and a lower chamber and having the other end connected to the vehicle body side, a rod guide for slidably guiding the piston rod, and the rod guide And a cylinder that accommodates the cylinder. A reservoir is formed between the cylinder and the outer cylinder, and a lower end of the outer cylinder is connected to the wheel side, and a predetermined damping force is generated by sliding of the piston. In a hydraulic shock absorber having a damper formed so as to generate, and a gas spring having one end connected to the outer cylinder side of the damper and the other end connected to the piston rod side,
A relief valve comprising a leaf valve is opposed to an annular window on the upper surface of the rod guide that communicates with the upper chamber of the cylinder, while an upper chamber of a ring nut communicated with a gas chamber of the gas spring and the relief valve are accommodated, and By inserting a push rod into the partition that separates the lower chamber of the ring nut that communicates with the reservoir, and energizing the leaf valve from the back via the push rod due to the differential pressure between these upper and lower chambers, and controlling the relief pressure An air suspension hydraulic shock absorber characterized in that the damping force changes in response to the pressure in the gas chamber corresponding to the load on the vehicle body side. By narrowing the passage area of the communication hole that communicates the gas chamber of the gas spring and the upper chamber of the ring nut, the pressure in the upper chamber of the ring nut corresponding to the pulsation of the pressure of the gas spring during vehicle travel is leveled, The hydraulic shock absorber for an air suspension according to claim 1, wherein the ride comfort during running is stabilized.

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