JP3270647B2 - 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 vehicle suspension device.

[0002]

2. Description of the Related Art In order to achieve a high level of comfort and operability of a vehicle at the same time, the spring constant of an air spring and the damping force of a shock absorber are usually kept in a soft state, while the operability during turning is maintained. An electronically controlled suspension is known that switches to a hard drive in driving situations where emphasis is placed (Mitsubishi Motors Technical Review 199
3 NO.5 "Development of electronically controlled suspension for large buses"
reference).

As one of such suspension controls, there has been proposed a technique for suppressing body vibration in a low frequency range such as pitching and bouncing and body vibration in a whole frequency range on a rough road by a simple arithmetic processing. (Japanese Patent Application No. 6-61322). In this case, a sensor for detecting the vertical acceleration of the vehicle body is provided. The sprung resonance level is calculated from the absolute value of the detection signal, and the unsprung resonance level is calculated from the absolute value of the temporal change. , A sprung resonance state and a rough road running state are determined, and the switching of the spring constant and the damping force of each suspension is controlled according to the determination result.

[0004]

By the way, the frequency of the vehicle body vibration changes according to the vehicle speed and the load even if the vehicle travels on the same road surface. The body vibration increases as the vehicle speed increases, and decreases as the load capacity increases. However, in the conventional example, since each threshold value is constant, the sensitivity of control differs depending on the running condition of the vehicle, and there is a problem that a stable vibration damping effect cannot be obtained in all vehicle speed ranges.

An object of the present invention is to solve such a problem.

[0006]

In the first invention, FIG.
Means for switching the spring constant and damping force of the suspension in two or more steps, means for detecting the vertical acceleration of the vehicle body, and means for calculating the sprung resonance region level from the absolute value of the detection signal of the vertical acceleration. Means d for calculating the unsprung resonance band level from the absolute value of the temporal change of the vertical acceleration detection signal, and comparing these resonance band levels with respective thresholds to determine the sprung resonance state and the rough road running state E, means f for controlling switching between the spring constant and the damping force of the suspension according to the result of the determination,
A means g for detecting the vehicle speed and a means h for changing each of the threshold values according to the detection signal of the vehicle speed are provided.

In the second invention, means a for switching the spring constant and damping force of the suspension in two or more steps, respectively, and means b for detecting the vertical acceleration of the vehicle body in FIG.
Means c for calculating the sprung resonance region level from the absolute value of the vertical acceleration detection signal, means d for calculating the unsprung resonance region level from the absolute value of the temporal change of the vertical acceleration detection signal, Means e for comparing the resonance area level with the respective thresholds to determine a sprung resonance state and a rough road running state;
Means f for controlling the switching of the spring constant and damping force of the suspension according to the determination result, means i for detecting the load of the vehicle, and changing each of the threshold values according to the detection signal of the load. Means h.

[0008]

[Function] When the vehicle body (spring-up) vibrates due to pitching or bouncing during normal running, only the vibration level in the low frequency range increases, but when traveling on a rough road, the high-frequency range due to the vertical vibration under the spring such as tires causes the vibration level. Vibration level also increases. Therefore, by comparing the absolute value of the vertical acceleration and the absolute value of its temporal change with the respective threshold values, the sprung resonance state in which only low-frequency vibration is required to be damped and the vibration level in the high-frequency band are also suppressed. It is possible to determine a rough road traveling state that requires a swing.

According to the first aspect of the present invention, the spring constant of the suspension is enhanced so as to enhance the vibration suppression effect of low-frequency vibration based on the determination of the sprung resonance state, and to enhance the vibration suppression effect of all-frequency vibration based on the determination of rough road running. By controlling the damping force, the vehicle body vibration can be effectively damped. In this case, since each threshold value of the control is not constant and changes according to the vehicle speed, sprung mass damping and bad road damping suitable for the running condition of the vehicle are performed, so that excellent body vibration with less body vibration in the entire vehicle speed range. Ride comfort can be secured.

According to the second aspect of the present invention, since each control threshold value changes in accordance with the load amount, the sprung mass damping and the rough road damping are appropriately performed, so that even if the load amount of the vehicle changes. In addition, excellent ride comfort with less body vibration can be secured.

[0011]

1 and 2, reference numeral 20 denotes a vehicle body as a sprung system of the vehicle, 1a to 1d denote tires as unsprung systems of the vehicle, and air springs 2a to 2f and shock absorbers 7a to 7f. Interposed. Although not shown, the shock absorbers 7a to 7f include a damping force variable mechanism (including an actuator) that switches between a hard and soft stage by opening and closing the orifice of the piston.

The air springs 2a to 2f are connected to the air reservoir 3 via leveling valves 4a to 4c for controlling air supply and exhaust so as to maintain a desired vehicle height. Since the rear wheel has one leveling valve 4c, the left and right air springs 2c, 2e and 2d, 2f communicate with each other.
On / off valves 8a and 8b are provided in each pipe.

The sub-tanks 5a to 5d are connected to the air springs 2a to 2f via the switching valves 6a to 6f, respectively. When the opening and closing of the valves 6a to 6f are controlled, the substantial air volume changes. The spring constant of ２2f is switched between two stages (hard and soft). 1 is an overall system configuration diagram, and FIG. 2 is a configuration diagram of a front wheel side representing a suspension for one wheel.

A vehicle speed sensor 17 for detecting the running speed of the vehicle, a lateral acceleration sensor 14 for detecting the lateral acceleration of the vehicle body, Vertical acceleration sensors 15a and 15b for detecting acceleration (in this case, disposed at left and right symmetrical positions sandwiching the center of the front wheel axle), a steering angle sensor 11 for detecting a steering angle of a steering wheel, and a braking state of the vehicle Brake switch 12, back lamp switch 16, side brake switch 13, and mode changeover switch 1 for selecting manual control or automatic control
0 is provided.

The controller 9 controls rolls, brake dives, pitching and bouncing of the vehicle body based on input signals from these sensors and switches.
A functional block configuration of control for performing sprung mass damping and rough road damping is represented by a vertical acceleration sensor 1 as shown in FIG.
5a, 15b and input means 30, 31 for inputting the detection signals of the vehicle speed sensor 17, respectively; and a control threshold for discriminating a sprung resonance state and a rough road running state from a data map (see FIG. 5) according to the vehicle speed signal. Means for determining 32, means for comparing the product of the absolute value of the vertical acceleration signal and the product of the absolute value of the temporal change of the vertical acceleration signal with the respective control thresholds to determine the sprung resonance state and the rough road running state And means 34 and 35 for outputting control signals to the switching valves 6a to 6f of the air springs 2a to 2f and the damping force variable mechanism of the shock absorber in accordance with the result of the determination.

FIG. 4 is a flowchart for explaining the contents of control for performing sprung mass damping and bad road damping, and is repeatedly executed at a predetermined control cycle. First, after initialization, the detection signals Gzr and Gzl of the vertical acceleration sensors 15a and 15b and the detection signal V of the vehicle speed sensor 17 are read (steps 1 and 2). When the vehicle speed signal V is zero (stop state), the switching valves 6a to 6f of the air springs 2a to 2f are "opened" and the damping force variable mechanism of the shock absorbers 7a to 7f is switched to a "soft" state (step 3 →). Step 12,
Step 13).

If the vehicle speed signal is not zero, the control decision value Z
s (sprung resonance level) and control determination value Zu (unsprung resonance level) are calculated (step 4). The control decision value Zs represents the magnitude of the vibration level in the entire frequency range, and is given by Zs = | Gzr | × | Gzl |, and the control decision value Zu represents the magnitude of the vibration level in the high frequency range. Zu = | Gzr−Gzr _i−1 | × | Gzl−Gzl
_i-1 |. Here, Gzr _i-1 and Gzl _i-1 indicate the previous detected values of the vertical acceleration.

When the vehicle body vibrates due to pitching or bouncing during normal running, only the vibration level in the low frequency range increases. On the rough road, however, the vibration level in the high frequency range due to the unsprung vertical vibration of tires and the like also increases. growing.
Therefore, if these control threshold values Zs and Zu exceed the respective control thresholds, it is possible to determine the sprung resonance state where vibration suppression in the low frequency range is required and the rough road traveling state where vibration suppression in the high frequency range is also required. is there.

To make the determination, control thresholds Za, Zb
Are read from the data map of FIG. 5 (step 5). In this case, since the data map is set using the vehicle speed as a parameter, the threshold values Za, Zb according to the vehicle speed signal V are set.
Is required.

The control judgment value Zs is compared with the control threshold value Za, and the control judgment value Zu is compared with the control threshold value Zb, respectively (steps 6 and 7). If Zs> Za is not satisfied, it is determined that sprung mass damping and bad road damping are not required, and the switching valves 6a to 6f of the air springs 2a to 2f are "opened", and the damping force variable mechanism of the shock absorbers 7a to 7f. Is kept in a "soft" state (step 6 → step 12, step 13).

When Zs> Za but not Zu> Zb, only the vibration level in the low frequency range is large and it is determined that sprung mass damping is required, and the switching valves 6a to 6f of the air springs 2a to 2f are determined. 6f is kept "open", and only the damping force variable mechanism of the shock absorbers 7a to 7f is switched to the "hard" state (steps 8 and 9).

When Zs> Za and Zu> Zb,
The vibration level in the high-frequency range is also large, and it is determined that a bad road control vibration is required, and the switching valves 6a to 6f of the air springs 2a to 2f are determined.
6f is closed, and the damping force variable mechanisms of the shock absorbers 7a to 7f are switched to the "hard" state (step 1).
0, step 11).

With such a configuration, when sprung mass damping is required, the air springs 2a to 2f are soft and only the shock absorbers 7a to 7b are switched to hard, so that the damping force of the suspension is increased. Can be effectively damped. When bad road control vibration is required, the air springs 2a to 2f and the shock absorber 7 are used.
Since both a to 7f are switched to hard, the stroke of the suspension can be suppressed to a small value, so that it is also possible to avoid a shock or the like generated at the time of bottoming by the bound stopper.

In this case, since the control thresholds Za and Zb are not constant but change according to the vehicle speed, the sprung mass damping and the rough road damping suitable for the running condition of the vehicle are performed. Excellent ride comfort with less vibration can be secured.

FIG. 6 shows a functional block configuration of control relating to sprung mass damping and rough road damping of the control unit 9 as another embodiment, and detects the load of a vehicle in the above embodiment. A load sensor 18; a means 36 for inputting a detection signal from the load sensor 18;
A means 37 for switching the data map of Zb is added.

Here, means 3 for switching the data map
7, a load range (0 ≦ W <W ₁ ,..., W _n) as shown in FIG.
A plurality of (n + 1) data maps having different settings for each .ltoreq.W) are provided, and a data map in a load range corresponding to the load signal W is selected as a control map at that time. Note that the same units as those in FIG. 3 are denoted by the same reference numerals.

FIG. 7 is a flowchart for explaining the contents of control for performing sprung mass damping and bad road damping, and is repeatedly executed at a predetermined control cycle. Vertical acceleration sensor 15 after initialization
a, 15b and the vehicle speed sensor 1
7 and the detection signal W of the load sensor 18 are read (Step 1, Step 2).

When the vehicle speed signal V is zero (stop state), the switching valves 6a to 6f of the air springs 2a to 2f are "opened",
The damping force variable mechanisms of the shock absorbers 7a to 7f are switched to the "soft" state (step 3 → step 1).
3, step 14). When the vehicle speed signal V is not zero, the control determination value Zs is set to Zs = | Gzr |
× | Gzl |, and the control determination value Zu is changed to Zu = | Gzr-G
zr _i-1 | × | Gzl−Gzl _i−1 | (step 4).

Then, a data map of a corresponding load range is selected based on the load signal W, and the control threshold values Za and Zb corresponding to the vehicle speed signal V are read from the map. , The control determination value Zu
and b (steps 6 to 8). When Zs> Za is not satisfied, it is determined that sprung mass damping and bad road damping are not required, and the air springs 2a to 2a
f, the switching valves 6a to 6f are "opened" and the shock absorber 7 is opened.
The variable damping force mechanisms a to 7f are kept in the “soft” state (step 7 → step 13, step 14).

When Zs> Za but not Zu> Zb, only the vibration level in the low frequency range is large and it is determined that sprung mass damping is required, and the switching valves 6a to 6f of the air springs 2a to 2f are determined. 6f is kept "open", and only the damping force variable mechanisms of the shock absorbers 7a to 7f are switched to the "hard" state (steps 9 and 10).

When Zs> Za and Zu> Zb,
The vibration level in the high frequency range is also large, and it is determined that the vibration control on the rough road is required, and the switching valves 6a to 6f of the air springs 2a to 2f are determined.
f is "closed" and the damping force variable mechanisms of the shock absorbers 7a to 7f are switched to the "hard" state (step 1).
1, Step 12).

According to such a configuration, the respective thresholds Za and Zb of the control for performing sprung mass damping and bad road damping change according to the load W in addition to the vehicle speed. In addition, excellent ride comfort can be secured in all vehicle speed ranges. In addition,
In the case of a commercial vehicle having a large load capacity, the threshold values Za and Zb can be changed only in accordance with the load W of the vehicle regardless of the vehicle speed V. Can greatly contribute to

The change of the control thresholds Za and Zb according to the load W is performed by shifting the comparison range of the vehicle speed V based on one data map as shown in FIG. 9 without depending on a plurality of data maps. You may do it. In that case, control thresholds Za and Zb corresponding to the vehicle speed V are obtained within a comparison range corresponding to the load W. In a bus or the like, a photo sensor may be provided at the entrance instead of the load sensor 18 to count the number of passengers.

[0034]

According to the first aspect, means for switching the spring constant and damping force of the suspension in two or more stages, means for detecting the vertical acceleration of the vehicle body, and means for detecting the spring from the absolute value of the detection signal of the vertical acceleration. Means for calculating the upper resonance band level, means for calculating the unsprung resonance band level from the absolute value of the temporal change of the vertical acceleration detection signal, and comparing these resonance band levels with respective thresholds to determine the sprung resonance. Means for judging the state and the rough road traveling state, means for controlling switching of the spring constant and damping force of the suspension according to the result of the judgment, means for detecting the vehicle speed, and Since there is a means to change the threshold,
Since the control thresholds are not constant and change according to the vehicle speed, sprung mass damping and bad road damping suitable for the running conditions of the vehicle are performed, so that excellent riding comfort with less body vibration in all vehicle speed ranges is achieved. Can be secured.

According to the second aspect, means for switching the spring constant and damping force of the suspension in two or more steps respectively, means for detecting the vertical acceleration of the vehicle body, and sprung resonance based on the absolute value of the detection signal of the vertical acceleration Means for calculating the band level, means for calculating the unsprung resonance band level from the absolute value of the temporal change of the vertical acceleration detection signal, and comparing these resonance band levels with respective thresholds to determine the sprung resonance state and Means for determining a rough road traveling state, means for controlling switching of a spring constant and a damping force of a suspension according to a result of the determination, means for detecting a load amount of a vehicle, and a method for detecting a load amount of the vehicle. Since means for changing each threshold value are provided, each threshold value of the control changes according to the load capacity.
Since the sprung mass damping and the rough road damping are appropriately performed, an excellent ride comfort with less vehicle body vibration can be ensured even if the load of the vehicle changes.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram illustrating a suspension for one wheel.

FIG. 3 is a functional block diagram showing a part of a control unit.

FIG. 4 is a flowchart illustrating control contents of a control unit.

FIG. 5 is a data map of a control threshold.

FIG. 6 is a functional block diagram showing another embodiment.

FIG. 7 is a flowchart illustrating control contents of a control unit.

FIG. 8 is an explanatory diagram related to a data map change process.

FIG. 9 is an explanatory diagram relating to a data map change process.

FIG. 10 is a diagram corresponding to claims of the present invention.

[Explanation of symbols]

 1a-1d Tires 2a-2f Air springs 4a-4c Leveling valves 5a-5d Sub-tanks 6a-6f Switching valves 7a-7f Shock absorbers 9 Control units 15a, 15b Vertical acceleration sensor 17 Vehicle speed sensor 18 Load sensor

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masami Hagiwara Nissan Diesel Kogyo Co., Ltd. (72) Inventor Sadahiro Takahashi Nissan Diesel Kogyo 1 JP-A-5-58129 (JP, A) JP-A-5-178044 (JP, A) JP-A-6-143965 (JP, A) JP-A-4-108016 (JP, A) A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B60G 1/00-25/00

Claims (2)

(57) [Claims] 1. A means for switching a spring constant and a damping force of a suspension in two or more stages, a means for detecting a vertical acceleration of a vehicle body, and a means for calculating a sprung resonance region level from an absolute value of a detection signal of the vertical acceleration. Means for calculating the unsprung resonance band level from the absolute value of the temporal change of the vertical acceleration detection signal, and comparing these resonance band levels with respective thresholds to determine the sprung resonance state and the rough road traveling state Means for controlling the switching of the spring constant and the damping force of the suspension according to the determination result, means for detecting the vehicle speed, and means for changing each of the thresholds according to the vehicle speed detection signal. A suspension device for a vehicle, comprising: 2. A means for switching a spring constant and a damping force of a suspension in two or more stages, a means for detecting a vertical acceleration of a vehicle body, and a means for calculating a sprung resonance region level from an absolute value of a detection signal of the vertical acceleration. Means for calculating the unsprung resonance band level from the absolute value of the temporal change of the vertical acceleration detection signal, and comparing these resonance band levels with respective thresholds to determine the sprung resonance state and the rough road traveling state Means for controlling the switching between the spring constant and the damping force of the suspension according to the result of the determination, means for detecting the load of the vehicle, and changing each of the thresholds according to the detection signal of the load. A suspension device for a vehicle, characterized by comprising means.