JP2903364B2 - Air suspension system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air suspension system for a vehicle, and more particularly to a technique for reducing a spring constant.

[0002]

2. Description of the Related Art Conventionally, as one of suspensions equipped on a bus or a large truck, for example, Japanese Utility Model Laid-Open No.
2. Description of the Related Art An air suspension device for a vehicle that supports a vehicle body by utilizing air elasticity as disclosed in Japanese Patent Application Laid-Open No. 52920 and Japanese Utility Model Application Laid-Open No. 2-141510 is known.

More specifically, as shown in FIG. 5, air springs 3A and 3B are provided on both sides between a sprung portion and a unsprung portion on the front side of the vehicle, that is, between the vehicle body and two front tires. I have. Air springs 3C, 3D, 3E, and 3F are provided on both sides of the rear side of the vehicle between the sprung portion and the unsprung portion, that is, between the vehicle body and the four rear tires. Note that, for the sake of simplicity, the following description will be referred to as an air spring 3.

Next, an air system related to the vehicle air suspension device will be described. That is, the air pressurized by the air compressor 11 is supplied to the air dryer 1.
After the water contained in the air is removed by 2, it is stored in the air reservoir tank 13. The pressure in the air reservoir tank 13 is adjusted to a predetermined pressure by the governor 14. The compressed air stored in the air reservoir tank 13 is sent to the air spring 3 via the leveling valve 4 of the air spring 3.

[0005] The leveling valve 4 adjusts the degree of filling of the air springs 3 with the compressed air in accordance with the increase or decrease of the load. When the vehicle height decreases, the leveling valve 4 moves the air reservoir tank 13 and the air springs 3 to each other. When the vehicle height rises, on the contrary, the leveling valve 4 opens to the exhaust side to exhaust the air in each air spring 3 to lower the vehicle height.

In a bus, a truck, or the like equipped with the above-described vehicle air suspension device, the vehicle body swings during traveling. The supply and exhaust of the compressed air in the spring 3 are performed. On the other hand, in recent years, there has been a need to further improve the riding comfort of the vehicle. For this reason, as shown in FIG. 5, an air suspension device having a sub-tank 6 communicating with the inside of the air spring 3 via a pipe 5 has been proposed. Have been.

That is, by integrating the inside of the air spring 3 and the sub tank 6, the air volume inside the air spring 3 is increased. Since the internal pressure does not increase in response to an external force as the air volume increases, the reaction force of the air spring 3 decreases, thereby reducing the spring constant and improving the riding comfort.

[0008]

However, when the spring constant is reduced in this manner, the ride comfort is improved, but the swing of the vehicle body is increased. For this reason, a stabilizer or the like is mounted as a roll reducing means. However, there is a risk that the ride comfort may be adversely affected, the vehicle weight may increase, and the fuel efficiency may deteriorate.

In view of the above-mentioned conventional problems, the present invention provides an air suspension system having a sub-tank for increasing the air volume inside an air spring, without reducing the riding comfort. The purpose of the present invention is to reduce the roll in the region and increase the roll controllability.

[0010]

According to the first aspect of the present invention, one air spring is provided on each of both sides between a sprung portion and a unsprung portion on the front side of a vehicle and communicates with the insides of the two air springs. The two communication passages are
One communication passage which communicates with each of the two sub-tanks and is provided with two air springs on both sides between a sprung portion and a unsprung portion on the rear side of the vehicle, and joins communication passages which respectively communicate with the insides of the two air springs. Are respectively connected to one sub-tank having a capacity approximately twice the capacity of one sub-tank on the front side, and opening / closing means are provided on each communication path on the front side and one communication path on the rear side of the vehicle. On the other hand, vehicle speed detecting means, steering steering angle detecting means, sprung object roll angular velocity detecting means, stroke detecting means for detecting the expansion / contraction stroke of each air spring, and the vehicle speed, steering steering angle, roll angular velocity and expansion / contraction stroke Control means for controlling each of the opening / closing means based on the above.

According to a second aspect of the present invention, the control means includes:
When the vehicle speed is equal to or higher than a predetermined vehicle speed and the steering angular speed calculated based on the steering angle is equal to or higher than a predetermined value, the opening / closing means is closed, and after closing the opening / closing means, the roll angle calculated based on the roll angular velocity. While the opening and closing means is opened when is less than a predetermined value, the vehicle speed is less than a predetermined vehicle speed,
The opening / closing means is closed when the steering angle is equal to or more than a predetermined value and the stroke is equal to or more than a predetermined value.After closing the opening / closing means, the roll angle calculated based on the roll angular velocity is smaller than a predetermined value. The opening / closing means is opened.

[0012]

According to the first aspect of the present invention, by controlling each opening / closing means based on a vehicle speed, a steering angle, a roll angular speed, and an expansion / contraction stroke, a spring constant is switched according to a vehicle situation and a steering state. Is reduced, driving stability is improved, and riding comfort is also improved.

In particular, by attaching one sub-tank to two air springs on the rear side and making the sub-tank capacity approximately twice the capacity of one sub-tank volume on the front side, in a low frequency range and a high frequency range, Without increasing the pipe diameter or increasing the tank capacity,
The spring constant can be reduced. In the specific control according to the second aspect of the present invention, when the vehicle is running at a high speed and there is a possibility that a sudden roll occurs, the opening and closing of the solenoid valve is controlled based on the steering angular velocity or the roll angle. In the case where the vehicle is running at a low speed, a sudden roll does not occur, and a roll having a small roll angular velocity occurs, the opening and closing of the solenoid valve is controlled based on the steering angle of the steering or the expansion and contraction stroke. In addition, the ride comfort can be improved while reducing the roll as much as possible in all speed ranges to improve running stability.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. First, the system configuration according to the present embodiment will be described. However, since the overall configuration is the same as that of the conventional apparatus in FIG. 5, detailed description thereof will be omitted with reference to FIG.

That is, in this embodiment, the portion indicated by A in FIG. 5 is configured as shown in FIG. 1A, and the portion indicated by B is configured as shown in FIG. 1B. That is, in FIG.
Air springs 15 are provided between the vehicle body as a sprung part on the front side of the vehicle and the front tires as an unsprung part. Each air spring 15 is connected to a communication path 16 that communicates with the inside of the air spring 15.
Each of the communication passages 16 communicates with the inside of the sub tank 17. The communication passages 16 are provided with electromagnetic valves 18 as opening / closing means.

On the other hand, in FIG. 1B, air springs 19 and 20 are provided between the vehicle body as a sprung portion on the rear side of the vehicle and the rear tire as a unsprung portion. The air springs 19 and 20 are connected to communication passages 21 and 22 that communicate with the insides of the air springs 19 and 20, respectively. One communication passage 23 that joins the communication passages 21 and 22 is connected to the front side. Is connected to one sub-tank 24 having a capacity approximately twice the capacity of one sub-tank 17. An electromagnetic valve 25 as opening / closing means is interposed in the one communication passage 23.

In this configuration, each of the solenoid valves 18,
As shown in FIG. 2, 25 is controlled to open and close by a control signal output from a control unit 31 incorporating a microcomputer, and is controlled so as to control opening and closing of the communication paths 16 and 23. The control unit 31 has a vehicle speed V from a vehicle speed sensor 32 as vehicle speed detecting means.
A signal, a steering angle θs signal from a steering angle sensor 33 provided on a steering (not shown) as a steering angle detecting means, a rate gyro provided on a vehicle body (not shown) which is a sprung object as a roll angular velocity detecting means 3
5 and the stroke X from a stroke sensor 36 as stroke detecting means for detecting the expansion / contraction stroke X of each air spring.
A signal is input to the control unit 31 based on the vehicle speed V, the steering angle θs, the sprung object roll angular velocity Vθ, and the stroke X.
Control means for controlling 8, 25 are provided as software.

Next, referring to the flowchart shown in FIG.
5 will be described. That is, in step 1 (abbreviated as S1 in the figure, the same applies hereinafter), the vehicle speed V from the vehicle speed sensor 32, the steering angle θs from the steering angle sensor 33, the roll angular velocity Vθ of the vehicle body from the rate gyro 35, and the stroke sensor 36 Is read.

In step 2, it is determined whether the vehicle speed V is equal to or higher than a predetermined vehicle speed (for example, 40 km / h). Vehicle speed V
If it is determined that the vehicle speed is equal to or higher than the predetermined vehicle speed, the vehicle is traveling at a high speed, and a sudden roll may occur. Therefore, the response is slow in the control based on the steering angle θs or the stroke X. If so, the process proceeds to step 3 and subsequent steps.

In step 3, the steering angular velocity θαs is calculated from the steering angle θs, and the routine proceeds to step 4, in which the steering angular velocity θαs is calculated.
It is determined whether or not αs is equal to or greater than a predetermined steering angular velocity θα,
When the steering angular velocity θαs is equal to or higher than the predetermined steering angular velocity θα,
In other words, when the steering angle suddenly changes due to a sudden steering operation, it is determined that a sudden roll has occurred, and the routine proceeds to step 5, where the solenoid valves 18 and 25 are controlled to be closed, and the inside of the air spring and the sub tank are controlled. Cuts off communication with the Here, when the communication between the inside of the air spring and the sub-tank is cut off, the air volume of the air spring becomes only the inner volume of the air spring and becomes smaller. However, as the air volume becomes smaller, the internal pressure when the air spring receives an external force is reduced. Is greatly increased, the reaction force is increased, and the spring constant is increased, so that a suspension device having a large roll reducing effect is obtained.

In step 6, the current roll angle θ _R is calculated by integrating the roll angular velocity Vθ of the vehicle body from the rate gyro 35. And in step 7,
It is determined whether the roll angle θ _R has become less than the predetermined roll angle θ _{R x} to determine whether the roll of the vehicle body has subsided. If it is determined that θ _R <θ _{R x} , Proceed to step 8. The process proceeds to step 8 when the roll of the vehicle body is reduced and the steering stability is obtained. Therefore, a suspension device that does not significantly reduce the roll may be used.

Therefore, in step 8, the solenoid valves 18, 2
5 is controlled to open, and the inside of the air spring communicates with the sub tank. Here, when the inside of the air spring communicates with the sub tank, the air volume of the air spring becomes the sum of the internal volume of the air spring and the internal volume of the sub tank, and becomes large. As the air volume increases, the internal pressure when the air spring receives an external force does not increase so much, the reaction force also decreases, and the spring constant decreases, so that riding comfort is ensured.

If it is determined in step 7 that θ _R ≧ θ _{R x} , the process returns to step 3. When the process returns to step 3, the roll of the vehicle body is not yet reduced and the steering stability cannot be obtained. Therefore, the process proceeds to step 4 again and the steering angular velocity is determined as described above. . On the other hand, if it is determined in step 2 that the vehicle speed V is lower than the predetermined vehicle speed, the vehicle is traveling at a low speed, a sharp roll does not occur, and a roll having a small roll angular velocity Vθ is generated. Proceed to step 9 and below,
The opening / closing control of the solenoid valves 18 and 25 is performed based on the steering angle θs or the stroke X of the steering.

In step 9, the steering angle θ of the steering wheel
It is determined whether or not s is equal to or greater than a predetermined steering angle θs _x at which there is a risk of generating a roll. If it is determined that θs ≧ θs _x , the vehicle is traveling at low speed, but the steering angle θs is Because of the large size, there is a possibility that a roll is generated.
Proceed to 0, when the stroke X is equal to or a predetermined stroke X ₁ or more, are determined to be X ≧ X _1, the process proceeds to step 11. In step 11, the solenoid valves 18 and 25 are controlled to close, assuming that a roll occurs due to the steering being largely steered while the vehicle is in a low speed state,
Cut off the communication between the inside of the air spring and the sub tank.
In this case, as described above, a spring device having a large spring constant and a large roll reducing effect is obtained.

[0025] At step 12 and 13, as in step 6 and 7, to calculate the current roll angle theta _R, the vehicle body to determine whether the roll angle theta _R is less than a predetermined roll angle theta _{R x} Judge whether or not the roll has subsided, and θ _R <
If it is determined that θ _Rx , the routine proceeds to step 8, where the solenoid valves 18 and 25 are controlled to open, and the inside of the air spring communicates with the sub tank. In step 13, θ
If it is determined that _R ≧ θ _Rx , step 10
Then, the stroke is determined as described above.

In step 9, θs <θs_xso
If it is determined that there is, the process returns to step 1. Theory
As noted, in such an embodiment, the vehicle is running at high speed.
When running and there is a possibility that a sudden roll may occur
Is the steering angular velocity θαs or the roll angle θ _RBased on the
The opening and closing of the magnetic valves 18 and 25 is controlled so that the vehicle travels at low speed.
Roll does not occur and the roll angular velocity is low.
The steering angle θ, the steering angle θ_sSome
Or the solenoid valves 18 and 25 are opened based on the telescopic stroke X.
Closed is controlled, so it is possible in all speed ranges.
While reducing the roll as much as possible to improve running stability,
Comfort can also be improved.

In particular, according to this configuration, one sub-tank 24 is attached to the two air springs 19 and 20 on the rear side, and the capacity of the sub-tank 24 is approximately twice the capacity of the one sub-tank 17 on the front side. Accordingly, there is an advantage that the spring constant can be reduced in the vicinity of 1 Hz and 7 Hz or more, that is, in the low frequency range and the high frequency range (see FIG. 4) without increasing the pipe diameter or increasing the tank capacity. is there.

[0028]

As described above, according to the first aspect of the present invention, each opening / closing means is controlled based on the vehicle speed, the steering angle, the roll angular velocity, and the expansion / contraction stroke. The spring constant can be switched according to the state, and the riding comfort can be improved while reducing the roll and improving the running stability.In particular, in the low frequency range and the high frequency range, the pipe diameter can be increased. There is an advantage that the spring constant can be reduced without increasing the tank capacity.

According to the second aspect of the present invention, the ride comfort can be improved while reducing the roll as much as possible in all speed ranges to improve the running stability.

[Brief description of the drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a control system diagram of the embodiment.

FIG. 3 is a flowchart illustrating control contents of the embodiment.

FIG. 4 is a characteristic diagram for explaining the effect of the embodiment.

FIG. 5 is a system configuration diagram of a conventional vehicle air suspension device.

[Explanation of symbols]

 Reference Signs List 15 air spring 16 communication passage 17 sub tank 18 solenoid valve 19, 20 air spring 21, 22 communication passage 23 communication passage 24 sub tank 25 solenoid valve 31 control unit 32 vehicle speed sensor 33 steering angle sensor 35 rate gyro 36 stroke sensor

Claims (2)

(57) [Claims] An air spring is provided on both sides between a sprung portion and a unsprung portion on a front side of a vehicle, and two communication passages respectively communicating with the insides of the air springs are respectively communicated with two sub-tanks having a predetermined capacity. Further, two air springs are provided on both sides between the sprung portion and the unsprung portion on the rear side of the vehicle, respectively, and one communication passage which joins communication passages respectively communicating with the insides of the two air springs is connected to the front side of the front side.
One sub-tank having approximately twice the capacity of one sub-tank is connected to each sub-tank, and each communication path on the front side and one communication path on the rear side of the vehicle are provided with opening / closing means, respectively. A steering angle detecting means, a sprung object roll angular velocity detecting means, a stroke detecting means for detecting an expansion / contraction stroke of each air spring, and each of the opening / closing based on the vehicle speed, a steering angle, a roll angular velocity and an expansion / contraction stroke. And a control means for controlling the means. 2. The control means according to claim 1, wherein said vehicle speed is a predetermined vehicle speed or more.
When the steering angular velocity calculated based on the steering angle is equal to or greater than a predetermined value, the opening / closing means is closed, and after closing the opening / closing means, when the roll angle calculated based on the roll angular velocity is less than a predetermined value. While the opening / closing means is opened, the opening / closing means is closed when the vehicle speed is less than a predetermined vehicle speed, the steering angle is equal to or more than a predetermined value, and the stroke is equal to or more than a predetermined value. 2. The air suspension device for a vehicle according to claim 1, wherein the opening / closing means is opened when a roll angle calculated on the basis of is smaller than a predetermined value.