JP2906210B2 - Vehicle suspension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for a vehicle, and more particularly to a technique for controlling suspension characteristics according to a running state of a vehicle.

[0002]

2. Description of the Related Art As one of suspensions mounted on a bus or a large truck, for example, Japanese Utility Model Laid-Open No. 64-529.
2. Description of the Related Art A vehicle air suspension device that supports a vehicle body by utilizing air elasticity as disclosed in Japanese Patent Application Publication No. 20 and Japanese Utility Model Application Laid-Open No. 2-141510 is known.

That is, as shown in FIG. 7, air springs 23A and 23B 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.
Is installed. Also, on both sides between the sprung and unsprung sides on the rear side of the vehicle, that is, between the vehicle body and the four rear tires,
Air springs 23C, 23D, 23E and 23F are provided respectively. Note that, for the sake of simplicity, the following description will be referred to as an air spring 23.

Next, an air system related to the vehicle air suspension device will be described. That is, the air pressurized by the air compressor 31 is supplied to the air dryer 3.
After the water contained in the air is removed by 2, the water is stored in the air reservoir tank 33. The pressure in the air reservoir tank 33 is adjusted to a predetermined pressure by the governor 34. The compressed air stored in the air reservoir tank 33 is supplied to the leveling valve 2 of the air spring 23.
4 to the air spring 23.

[0005] The leveling valve 24 adjusts the degree of filling of the air springs 23 with the compressed air in accordance with the increase or decrease of the load. When the vehicle height decreases, the leveling valve 24 moves the air reservoir tank 33 and the air springs 23.
To increase the vehicle height, and conversely, when the vehicle height increases,
The leveling valve 24 opens to the exhaust side to exhaust the air in each air spring 23 to lower the vehicle height.

In a bus or a truck equipped with the above-described air suspension device for a vehicle, the height of the vehicle fluctuates due to a change in a loaded load, air leakage, or the like. Operates to supply and exhaust the compressed air in each air spring 23. On the other hand, in recent years, there is a need to cope with rolling of the vehicle without reducing the riding comfort of the vehicle. For this reason, a spring constant variable mechanism of an air spring and a damping force switching mechanism of a shock absorber are provided, and an air spring is provided. Is known in which the spring constant and the damping force of the shock absorber are controlled in accordance with the presence or absence of rolling of the vehicle (see Japanese Patent Application Laid-Open No. 5-193324).

In this conventional example, the rolling operation state of the vehicle is detected based on the difference between the detection values of two vertical acceleration sensors (upper and lower G sensors) installed near the front left and right wheels, respectively. When the rolling operation state of the vehicle is detected in the straight running state of the vehicle, at least one of the air springs or shock absorbers provided at both left and right ends between the sprung and unsprung state of the vehicle is in a hard state for all axles. Switching control.

[0008]

Conventionally, when a vehicle is traveling straight, only one of the left and right wheels is traveling on an irregular portion or a protruding portion of a road surface. There is a problem that vibration occurs on one of the left and right sides of the vehicle, resulting in poor ride comfort. In the above-described prior art, when only one of the left and right wheels of the vehicle is traveling on an irregular portion or a protruding portion of the road surface, two upper and lower wheels installed near the front left and right wheels are used. If the difference between the detected values of the acceleration sensors (upper and lower G sensors) is equal to or larger than a predetermined value, at least one of the air spring and the shock absorber is controlled to be switched to the hard state for all the axles. Suspension characteristics on the side where no occurrence occurs are also made hard, and conversely, there is a possibility that riding comfort will be degraded.

In view of the above-mentioned conventional problems, the present invention improves the riding comfort when only one of the left and right wheels of a vehicle is traveling on an irregular portion or a protruding portion of a road surface. The purpose is to do.

[0010]

According to the present invention, an air spring and a shock absorber are provided at both front and rear left and right ends between a sprung portion and a unsprung portion of a vehicle, respectively.
In a vehicle suspension device including a switching mechanism for switching at least one of an air spring and a shock absorber to hardware or software,
Air springs or shock absorbers provided on both the left and right ends of the vehicle, provided with vertical acceleration detecting means for detecting vertical acceleration generated in the vehicle, and provided on the same side as the side provided with the acceleration detecting means on the side where the vertical acceleration detected value is large. Is switched to the hard state, and the switching mechanism is switched to switch at least one of the air spring or the shock absorber provided on the same side as the side provided with the acceleration detecting means on the side having the smaller vertical acceleration detection value to the soft state. Control means for controlling is provided.

According to a second aspect of the present invention, the control means includes:
When the detected values of the vertical accelerations of the pair of vertical acceleration detecting means are both large, at least one of the air springs or shock absorbers provided at the front and rear left and right ends between the sprung and unsprung portions of the vehicle is switched to the hard state. For this purpose, the switching mechanism is controlled to be switched. According to a third aspect of the present invention, there is provided a straight running state detecting means for detecting a straight running state of the vehicle, and the control means switches the switching mechanism when the straight running state detecting means detects the straight running state of the vehicle. The control was performed.

[0012]

According to the first aspect of the present invention, the left or right side of the vehicle, on which vibration is generated, is made of a hard suspension to suppress vibration, and the non-vibrated side of the vehicle is kept soft by keeping the suspension soft. , The ride comfort can be improved. According to the second aspect of the present invention, occurrence of pitching or bouncing of the vehicle can be prevented.

According to the third aspect of the present invention, when the vehicle is traveling straight, for example, when only one of the left and right wheels is traveling on an irregular portion or a protruding portion of the road surface, the ride comfort is improved. Can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an overall system configuration of a suspension device for all wheels of a vehicle, and FIG. 2 shows an air suspension device for one wheel of the vehicle, for example, a left wheel on a front shaft.
That is, in these figures, an air spring 2 (2a to 2f) and a damping force switching mechanism are incorporated between the vehicle body 18 as a sprung portion of the vehicle and the tire 1 (1a to 1d) as a unsprung portion. And shock absorbers 7 (7a to 7f). An air reservoir tank 3 storing compressed air and the air springs 2 (2a to 2f) are provided with leveling valves 4 (4a to 4) for supplying and discharging compressed air to and from the air springs 2 (2a to 2f).
c). The air spring 2
(2a to 2f) The inside and the sub tank 5 (5a to 5d) are communicated via a spring constant switching valve 6 (6a to 6f) which is an electromagnetic valve as an opening and closing means for switching the spring constant.

Here, in the first aspect of the present invention,
Vertical acceleration sensors (vertical G sensors) 15a and 15b as vertical acceleration detecting means for detecting vertical acceleration generated in the vehicle are provided at both left and right ends of the vehicle, respectively (see FIG. 3).
At least one of the air spring or the shock absorber provided on the same side as the side where the vertical acceleration detection value is larger than the side where the vertical acceleration detection value is larger is switched to the hard state, and the upper and lower G sensor with the smaller vertical acceleration detection value is provided. The spring constant switching valve 6 (6a-6) as a switching mechanism for switching at least one of an air spring and a shock absorber provided on the same side as
f) and control means for switching control of the damping force switching mechanism of the shock absorbers 7 (7a to 7f).

Specifically, the spring constant switching valve 6 (6a
6f) and the damping force switching mechanism of the shock absorbers 7 (7a to 7f) are controlled by control signals output from a control unit 9 having a built-in microcomputer. The control unit 9 includes a changeover signal from a mode changeover switch 10 described later, a vehicle speed V signal from a vehicle speed sensor 17 as vehicle speed detection means, and a steering angle sensor 1.
1, a steering angle θ signal from the two upper and lower G sensors 15a, 1
A vertical acceleration signal is input from the control unit 9 to the control unit 9 based on the mode switching signal M, the vehicle speed V, the steering angle θ, and the vertical accelerations Z _R and Z _L. And the shock absorber 7 (7a-
Control means for controlling the actuator 7A of the damping force switching mechanism 7f) is provided as software.

FIG. 4 shows a detailed control block diagram. A mode switching signal output from the mode switching switch 10 is supplied to a control means B via a mode switching signal input means A.
Is input to The signal output from the vehicle speed sensor 17 is
It is input to the control means B via the vehicle speed signal input means C.
The signal output from the steering angle sensor 11 is input to the control means B via the steering angle signal input means H. Furthermore,
The signals output from the vertical G sensors 15a and 15b are input to the control means B via vertical acceleration signal input means D and E, respectively.

The control signal output from the control means B is supplied to the spring constant switching valve 6 (6a to 6f) via the spring constant switching valve switching signal output means F and to the shock absorber via the shock absorber switching signal output means G. 7 (7a-7f)
Is input to each of the actuators 7A of the damping force switching mechanism. Next, referring to the flowchart shown in FIG.
The spring constant switching valve 6 (6a) by the control unit 9
6f) and the control contents of the actuator 7A of the damping force switching mechanism of the shock absorber 7 (7a to 7f) will be described.

That is, in step 1 (abbreviated as S1 in the figure, the same applies hereinafter), the mode switching signal M, the vehicle speed V, the steering angle θ, and the vertical accelerations Z _R and Z _L are read. Step 2
Then, the mode switching signal M is determined, and when the auto mode is selected, the process proceeds to step 3. In step 3, it is determined whether or not the vehicle speed signal V from the vehicle speed sensor 17 is zero.
If it is determined that the vehicle speed V is not 0, step 4
And comparing | θ | with the steering angle threshold value θ _T ,
If θ | <θ _T (the vehicle goes straight ahead), the routine proceeds to step 5. In step 5, | Z _R |
_T, and if | Z _R | ≦ Z _T , the process proceeds to step 6 where | Z _L | is compared with the vertical acceleration threshold value Z _{T. If} | Z _L |> Z _T , And proceed to step 7. In this step 7, the spring constant switching valve corresponding to the left air spring of each of the front and rear axes is closed to increase (hard) the spring constant, and switch the shock absorber on the left to hard, and proceed to step 8, The spring constant switching valve corresponding to the air spring on the right side of each of the front and rear shafts is opened to reduce (soft) the spring constant and to softly switch the shock absorber on the right side.

On the other hand, in step 5, | Z _R |> Z
_{If T} , go to step 9 and compare | Z _L | with the vertical acceleration threshold Z _{T. If} | Z _L | ≦ Z _T ,
Proceed to step 10. In step 10, the spring constant switching valve corresponding to the right air spring of each of the front and rear axes is closed to increase (hard) the spring constant and switch the shock absorber on the right to hard, and proceed to step 11, The spring constant switching valve corresponding to the left air spring of each of the front and rear shafts is opened to reduce the spring constant (soft) and to switch the left shock absorber to soft.

In step 9, | Z _L |> Z _T
If so, proceed to step 12. In this step 12, the spring constant switching valves corresponding to the left and right air springs of the front and rear shafts are closed to increase the spring constant (hard) and to switch the left and right shock absorbers to hard. Here, in steps 5 to 8 of the flowchart, the vertical acceleration on the left side is larger than a predetermined value,
When the vertical acceleration on the right side is smaller than a predetermined value and vibration is generated on the left side of the vehicle as shown in FIG. 6 (A), the left air spring and the shock absorber are hardened,
This control is for softening the right air spring and shock absorber.

In steps 5, 9 to 11, the vertical acceleration on the right side is larger than a predetermined value, and the vertical acceleration on the left side is smaller than a predetermined value, and vibration is generated on the right side of the vehicle as shown in FIG. In this case, the right air spring and the shock absorber are hardened, and the left air spring and the shock absorber are softened. Further, steps 5, 9, and 12 are performed when the left and right vertical accelerations are both greater than a predetermined value and vibration is generated on both sides of the vehicle as shown in FIG. 6C. And the shock absorber are hardened, so that pitching or bouncing of the vehicle can be prevented.

As is apparent from the above description, the upper and lower G sensors 15a and 15b for detecting the vertical acceleration generated in the vehicle are provided at both the left and right ends of the vehicle, respectively. The air spring and shock absorber provided on the same side as the provided side are switched to the hard state, and the air spring and shock absorber provided on the same side as the side provided with the upper and lower G sensor with the smaller vertical acceleration detection value are in the soft state. When only one of the left and right wheels of the vehicle is running on irregular roads or bumps on the road surface, the left or right side of the vehicle where vibration is occurring By making the suspension hard, vibration is suppressed, and on the side that is not generating vibration, the suspension is kept soft, so that the ride comfort can be improved. That.

In the above embodiment, both the air spring and the shock absorber are controlled by hardware or software, but at least one of them may be switched by hardware or software.

[0025]

As described above, according to the first aspect of the present invention, the vertical acceleration detecting means for detecting the vertical acceleration generated in the vehicle is provided at each of the left and right ends of the vehicle. At least one of the air spring or the shock absorber provided on the same side as the side provided with the large acceleration detection means is switched to the hard state, and the vertical acceleration detection value is set on the same side as the side provided with the small acceleration detection means. Since at least one of the provided air spring or the shock absorber is switched to the soft state, for example, when only one of the left and right wheels of the vehicle is traveling on an irregular portion or a protruding portion of the road surface, Comfort can be improved, and it is possible to flexibly respond to road surface input to the vehicle thereafter.

According to the second aspect of the invention, the occurrence of pitching or bouncing of the vehicle can be prevented. According to the invention described in claim 3, when the vehicle is traveling straight, for example, when only one of the left and right wheels is traveling on an irregular portion or a protruding portion of the road surface, the riding comfort is improved. be able to.

[Brief description of the drawings]

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

FIG. 2 is a partial system configuration diagram of the embodiment.

FIG. 3 is a perspective view illustrating an installation position of an upper and lower G sensor.

FIG. 4 is a control block diagram of the embodiment.

FIG. 5 is a flowchart illustrating control contents of the embodiment.

FIG. 6 is a schematic diagram illustrating a state of occurrence of vibration of the vehicle.

FIG. 7 is a system configuration diagram of an example of a conventional vehicle suspension device.

[Explanation of symbols]

 1 (1a-1d) Tire 2 (2a-2f) Air spring 5 (5a-5d) Subtank 6 (6a-6f) Spring constant switching valve 7 (7a-7f) Shock absorber 9 Control unit 15a, 15b Vertical acceleration sensor ( Vertical G sensor) 18 Body

Claims (3)

(57) [Claims] An air spring and a shock absorber are provided at both front and rear left and right ends between a sprung portion and a unsprung portion of a vehicle, and a switching mechanism for switching at least one of the air spring and the shock absorber to a hard or soft state. A vehicle suspension device provided with a pair of vertical acceleration detecting means for detecting vertical acceleration generated in the vehicle at each of the left and right ends of the vehicle, and having the acceleration detecting means on the side where the vertical acceleration detection value is large. At least one of the air spring or shock absorber provided on the same side as
Control means is provided for switching control of the switching mechanism to switch at least one of an air spring or a shock absorber provided on the same side as the side on which the acceleration detection means on the side with the smaller vertical acceleration detection value is provided to the soft state. Vehicle suspension device. 2. The control device according to claim 1, wherein when the vertical acceleration detection value of each of the pair of vertical acceleration detection devices is large, the control means includes an air spring provided on each of the front and rear left and right ends between the sprung and unsprung portions of the vehicle. 2. The vehicle suspension device according to claim 1, wherein the switching mechanism controls the switching mechanism to switch at least one of the shock absorbers to a hard state. 3. The vehicle according to claim 1, further comprising a straight traveling state detecting means for detecting a straight traveling state of the vehicle, wherein the control means controls the switching mechanism when the straight traveling state detecting means detects the straight traveling state of the vehicle. The vehicle suspension device according to claim 1 or 2, wherein: