JP3656447B2 - Air suspension device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air suspension device that supports an axle using a pair of left and right air springs disposed asymmetrically with respect to the center in the vehicle width direction of a frame.
[0002]
[Prior art]
In trucks (vehicles), in order to obtain a comfortable ride, an air suspension device that suspends a front axle using an air spring is employed. This air suspension device includes a pair of left and right side frames between the left and right side frames and a lower side of the engine mounted on the frame along the vehicle width direction of the front axle. A structure in which an air spring is interposed is used.
[0003]
In a truck employing such an air suspension device, an air spring is used to maintain the vehicle body ground level at a constant (predetermined) height regardless of the increase or decrease of the load.
[0004]
The air suspension device has a leveling valve (a supply and exhaust valve, a predetermined frame with both valves at the middle point) that allows each air spring to supply and discharge the left and right air springs independently according to the height of the frame. And a structure in which an air tank as a pressure supply source is connected to each leveling valve. With the two independent air supply and discharge systems for each left and right air spring, when the air spring contracts due to loading and the vehicle body including the frame sinks, the air supply built into the leveling valve is displaced by the displacement transmitted from the lever of the leveling valve. The valve opens, guides high-pressure air from the air tank to each air spring, and lifts the vehicle body by the amount of contraction of the air spring due to the increase in air. When the load is reduced and the air spring is extended and the vehicle body including the frame is raised, the displacement transmitted from the lever of the leveling valve opens the exhaust valve built in the leveling valve, and the air in the air spring is released to the atmosphere from the atmosphere opening part. Then, the vehicle body is lowered by the amount that the air spring is extended so that the vehicle body is kept at a certain ground clearance.
[0005]
[Problems to be solved by the invention]
Recently, it has been considered that an air suspension device having such a leveling function is adopted for a front suspension of a truck.
[0006]
By the way, since the front part where the front axle of the frame is arranged includes a lot of equipment such as a traveling engine, auxiliary equipment of the engine, equipment constituting the steering device, and other equipment, the air suspension device Each air spring must be installed between the front axle and the frame, avoiding these devices.
[0007]
For this reason, when adopting an air suspension device at the front, for the sake of avoiding interference with equipment, the mounting of each air spring is not symmetrically arranged with respect to the center of the frame in the vehicle width direction, but asymmetrical left and right Specifically, one air spring may be disposed at a position far from the center of the frame in the vehicle width direction, and the other air spring may be disposed at a position near the center of the frame in the vehicle width direction.
[0008]
However, with such an air spring arrangement, the load acting on the frame is shared by the air spring that is closer to the distance, and is less shared by the air spring that is farther away. The internal pressure of each air spring will be different.
[0009]
In this case, although air springs having the same structure (the other structures including the pressure receiving area are the same) are used, the spring constants of the left and right air springs are different, and the behavior of the track tends to become unstable. In particular, air suspension systems that maintain a constant vehicle ground clearance with the leveling function increase the difference in internal pressure of each air spring as the load increases. It is easy to have many influences on the comfort, and improvement of this point is desired.
[0010]
The present invention has been made paying attention to the above circumstances, and its purpose is to use a leveling function so as to provide good steering stability and good ride comfort when an air spring is installed asymmetrically in the left-right direction. An object of the present invention is to provide an air suspension device that can support the vehicle body at a certain vehicle body ground clearance.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an air suspension device having a leveling function according to claim 1 has a pair of left and right air springs arranged asymmetrically with respect to the center in the vehicle width direction of the frame, with the same pressure receiving area. In addition, the internal volume is varied according to the ratio of the distance from the center of the frame in the vehicle width direction so that the spring constant of each air spring is equalized.
[0012]
As a result, even when the internal pressure of each air spring is significantly different due to the difference in the shared load, the left and right air springs support the vehicle body stably when loading, just as when the left and right air springs are arranged symmetrically. It is possible to obtain good steering stability and good riding comfort.
[0013]
In addition, when the air springs are asymmetrically arranged, the spring constants of the left and right air springs can be set uniformly without using a complicated structure such as changing the left and right independent air supply / discharge systems.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on an embodiment shown in FIGS. 1 and 2.
[0015]
FIG. 1 shows an air suspension device for suspending, for example, a front wheel P of a truck (vehicle), in which 1 is a frame of the truck. The frame 1 is formed in a ladder shape having a pair of side frames 2 extending in the vehicle front-rear direction.
[0016]
An engine 3 is mounted on the front portion (front side) of the frame 1 so as to fit between the left and right side frames 2. Further, below the frame 1 on which the engine 3 is mounted, a front axle 4 (axle) is inserted along the vehicle width direction on the lower side of the engine 3 and the lower side of the side rails 2. A front wheel P is connected to each end portion of the front axle 4 projecting from each side rail 2 in the vehicle width direction via a knuckle (not shown).
[0017]
Between the frame 1 and the front axle 4, an engine 3 attached to the frame 1, an auxiliary machine (not shown) of the engine 3, equipment (not shown) constituting the steering device, equipment of other equipment (not shown), etc. A pair of air springs 5 are attached to avoid many devices. That is, each air spring 5 is asymmetrically attached to the center in the vehicle width direction of the frame 1 in order to obtain an arrangement position that does not interfere with such various devices.
[0018]
Each air spring 5 is attached to each of the upper surface portions of the front axle 4 corresponding to the lower side of the side rails 2 at points that are asymmetrical with respect to the center in the vehicle width direction of the frame 1 to which the air spring 5 is attached. A seat mounting seat (not shown) is formed, and a spring seat member 6 is fastened to each seat mounting seat with a bolt, and a lower end portion of the air spring 5 is attached to a spring seat 6a formed by the spring seat member 6. A structure is used in which the upper end of the air spring 5 is fixed to a bracket 11 attached to the side rail portion immediately above the spring 5.
[0019]
Here, for example, a piston 8 having a surge tank chamber 8a inside is disposed on the lower side of the air spring 5 as shown on the right side in FIG. 2, and a diaphragm 9 is provided so as to cover the upper side of the piston 8. A combined structure is used. An end plate 10 having a predetermined size attached to the upper part of the diaphragm 9 is fixed to the bracket 11 using, for example, a bolt, and the lower part of the piston 8 is fixed to the spring seat 6a using, for example, a bolt. That is, the elastic force of the air spring 5, that is, the air pressure in the diaphragm 9 and the piston 8, supports the load applied from above and below. A shock absorber 7 is attached between each spring seat member 6 and the side rail portion immediately above the spring seat member 6 so as to attenuate the vibration of the air spring 5.
[0020]
A parallel link mechanism 16 using a U-shaped torsion beam 14 and a swing arm 15 is assembled between each spring seat member 6 and each bracket 13 attached to the lower surface of the side frame portion in front of the engine. The link mechanism 16 positions the front axle 4.
[0021]
On the other hand, each air spring 5 is connected with a pair of leveling control air supply / discharge systems 17 and 18 for each air spring 5. Each of the air supply / discharge systems 17 and 18 is formed by an air circuit 20 (mainly one side is shown) using a leveling valve 19 attached to a side frame portion above the swing arm, for example.
[0022]
That is, the leveling valve 19 includes a main body portion 21 with a built-in air supply valve and an exhaust valve (both not shown), and a rotatable lever 22 that switches between both valves (the air supply valve and the exhaust valve) (FIG. 1). And a lever member that is rotatably supported on the front surface of the main body 21. The lever 22 is rotatably connected to the spring seat member 6 on the lower side via the relay shaft 23a and the lever member 23b, and both the valves (the air supply valve and the exhaust valve) are set to a predetermined frame as a middle point. It can be switched according to changes in the ground clearance above the height. The main body 21 has a tank hole 24 connected to an air tank (not shown) serving as a pressure supply source, a spring hole 25 connected to the air spring 5, and an air release part (not shown) that opens to the atmosphere. When the air spring 5 contracts due to the loading, and the vehicle body including the frame 1 sinks, the built-in air supply valve is opened by the displacement transmitted from the lever 22. As a result, high-pressure air from the air tank is guided into the air spring 5 through the tank hole 24 and the spring hole 25, and the vehicle body is lifted by the amount of contraction of the air spring 5 due to the increase in air. Further, when the load is reduced and the air spring 5 is extended and the vehicle body including the frame 1 is raised, the exhaust valve built in the main body 21 is opened by the displacement transmitted from the lever 22. As a result, the air in the air spring 5 is released to the atmosphere through the spring hole 25 and the atmosphere opening portion (not shown), and the vehicle body is lowered by the amount that the air spring is extended.
[0023]
The air supply / discharge operation of each air spring 5 performed by the left and right independent air circuits 20 allows the vehicle body ground height to be maintained at a constant (predetermined) height regardless of the increase / decrease of the loaded load (loading vehicle, empty vehicle). It is. Reference numeral 26 denotes a piping member that connects between the spring hole 25 of the leveling valve 19 and the air spring 5.
[0024]
And the structure of a pair of air spring 5 with the same pressure receiving area is diverted, and the difference of the spring constant by the air spring 5 being arrange | positioned asymmetrically right and left is corrected.
[0025]
Specifically, as shown in FIG. 2, the internal volume of the pair of left and right air springs 5 is changed by an asymmetric ratio (corresponding to the crossed diagonal lines) so that the spring constants of the left and right air springs 5 are equalized. Yes.
[0026]
Here, a method for equalizing the spring constant will be described. The left and right air springs 5 have the following relationship.
[0027]
First, the distance from the center in the vehicle width direction (center of gravity G) of the frame 5 to each of the left and right air springs 5, specifically, the distance to the left air spring 5 is L1, and the distance to the right air spring 5 is When L2, the load W1 applied to the left air spring 5 by the load W applied from the frame 1 is
W1 = W * (L2 / L1 + L2)
The load shared by the right air spring 5 is
W2 = W * (L1 / L1 + L2).
[0028]
The internal pressure P1 of the left air spring 5 and the internal pressure P2 of the right air spring 5 are P1 = W1 / A, P2 = W1 / A (where A is an effective area (corresponding to the pressure receiving area, The same).
[0029]
From these, if the spring constant K1 of the left air spring 5 and the spring constant K2 of the right air spring 5 are obtained,
K1 = nA ² * (P1 + 1) * 1 / V1 * 1/10
K2 = nA ² * (P2 + 1) * 1 / V2 * 1/10 (where n is a polytropic index).
[0030]
By arranging this formula and expressing the condition that the spring constants of the left and right air springs 5 are equal (K1 = K2), V1 / V2 = (P1 + 1) / (P2 + 2). The spring constant of the air spring 5 is the pressure It can be seen that there is a relationship that is proportional to and inversely proportional to the internal volume.
[0031]
Here, since the effective area A of each air spring 5 is the same, in order to equalize the spring constant of the air spring 5 arranged asymmetrically, the ratio of the distance from the center of the frame 1 in the vehicle width direction is used. Thus, the inner volume of the air spring 5 may be changed.
[0032]
Therefore, among the left and right air springs 5 shown in FIG. 2, for example, a separator 27 formed of a partition plate, for example, is attached to the piston 8 of the air spring 5 on the side where the internal pressure becomes low due to asymmetric arrangement. 2, the inner volume of the piston 8, i.e., the piston volume, is decreased to satisfy the above equation, i.e., the spring constants K <b> 1 and K <b> 2 are equal to each other. The internal volume has been reduced. In particular, the spring constants K1 and K2 are set so that the spring constants K1 and K2 of the left and right air springs 5 are equal in a certain region from the empty vehicle to the loaded vehicle, for example, when loading is likely to impair handling stability and riding comfort. It is.
[0033]
The spring constants K1 and K2 of the air springs 5 arranged asymmetrically are made uniform by a structure in which the piston volume is reduced according to the ratio of the offset amount of the left and right springs 5.
[0034]
When the spring constants K1 and K2 of the air spring 5 are equalized in this way, the spring constants K1 and K2 of the asymmetrical air spring 5 are kept substantially equal.
[0035]
Therefore, even when the internal pressure of each air spring 5 is considerably different due to the difference in the shared load that each air spring 5 shares, the leveling function is used as in the case where the left and right air springs 5 are arranged symmetrically. When the vehicle is driven, the vehicle body including the frame 1 can be stably supported by the left and right air springs 5, and good steering stability and good riding comfort can be provided.
[0036]
Moreover, if the internal volume of the air spring 5 is changed, the spring constants K1 and K2 of the left and right air springs 5 can be easily set without using a complicated structure such as changing the left and right independent air supply / exhaust systems 17 and 18. Can be determined evenly.
[0037]
In the embodiment, the example in which the inner volume of the air spring 5 installed at a distance far from the center in the vehicle width direction of the frame 1 is reduced in accordance with the ratio of the offset amount is shown. The internal volume of the air spring 5 installed at a short distance from the center may be increased in accordance with the ratio of the offset amount, so that the spring constants K1 and K2 of the air springs 5 arranged asymmetrically may be made equal.
[0038]
In one embodiment, the present invention is applied to a front suspension of a truck. However, the present invention is not limited to this, and the present invention may be applied to any vehicle air suspension device in which an asymmetrical mounting of an air spring is unavoidable. Good.
[0039]
【The invention's effect】
As described above, according to the first aspect of the present invention, the spring constants of the air springs arranged asymmetrically can be kept uniform, and the internal pressures of the air springs are considerably different due to the difference in the shared load. Even when the left and right air springs are symmetrically arranged, the leveling function can be used to stably support the vehicle body with the left and right air springs when loading, providing good handling stability and good riding. You can get a feeling.
[0040]
In addition, since the internal volume of the air spring is made different according to the ratio of the offset amount of the air spring, the springs of the left and right air springs can be easily used without using a complicated structure such as changing the left and right independent air supply and exhaust systems. Constants can be set evenly.
[Brief description of the drawings]
FIG. 1 is a perspective view for explaining an air suspension device according to an embodiment of the present invention.
FIG. 2 is a view for explaining a structure for equalizing spring constants of left and right air springs arranged in an asymmetrical manner in the apparatus;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Frame 2 ... Side frame 3 ... Engine 4 ... Front axle (axle)
5 ... Air spring 6 ... Spring seat member 8a ... Surge tank chamber 8 ... Piston 9 ... Diaphragms 17, 18 ... A pair of air supply / discharge systems 19 ... Leveling valves.

Claims (1)

A pair of left and right air springs asymmetrically interposed with respect to the center of the frame in the vehicle width direction between the frame and an axle that passes through the lower side of the frame along the vehicle width direction;
A left and right independent air supply / discharge system that is connected to each of the air springs and supplies / discharges air in the air spring according to a change in the frame height so that the frame maintains a predetermined height;
The air suspension device, wherein the pair of left and right air springs have the same pressure receiving area and have different internal volumes according to the ratio of the distance from the center of the frame in the vehicle width direction.

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