JPH043323B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to an electronically controlled suspension device for an automobile having a vehicle height adjustment function and a vehicle body posture control function, which effectively prevents nose dive particularly during control. This invention relates to an electronically controlled suspension device.

[Technical background of the invention and its problems]

Generally, when an automobile is braked, a so-called nose dive phenomenon occurs, in which the front part of the vehicle body sinks and the rear part rises. Therefore, by using an electronically controlled suspension device that has a vehicle height adjustment function that can set the target vehicle height in three stages (high, medium, and low) and a vehicle attitude control function, when the braking condition is detected, the front wheel suspension It has been considered to reduce the nose dive phenomenon by increasing the spring reaction force of the suspension unit and lowering the spring reaction force of the rear wheel suspension unit.

By the way, when braking for normal stopping or deceleration (excluding emergency stops), the driver first prepares to start braking by lightly applying the foot on the brake pedal, and then calculates the stopping distance or following distance, etc. Generally, the brake pedal is pressed deeper to achieve reliable braking at the appropriate timing.

Therefore, for example, if the on-state of the brake switch that responds to the brake pedal is detected and the above-mentioned nose dive attitude control is started, it will be in a state where the brake pedal is only lightly applied and almost no braking is being performed. However, the control of each of the suspension units described above is executed, causing the front of the vehicle to rise above the normal height of the vehicle, giving the occupants a sense of discomfort.

Furthermore, for example, if the acceleration in the longitudinal direction of the vehicle body during braking is detected by an acceleration sensor and the nose dive attitude control is started when this acceleration exceeds a preset vehicle speed value, the timing of the attitude control in response to the attitude change can be adjusted. Because of the delay, a problem arises that makes the passengers feel uncomfortable.

[Purpose of the invention]

This invention was developed in view of the above-mentioned problems.For example, even when the brake pedal is first lightly applied and then gradually depressed deeper to ensure reliable control, it does not give the occupants a sense of discomfort. An object of the present invention is to provide an electronically controlled suspension device that can prevent nose dive of a vehicle body without causing any damage.

[Summary of the invention]

In other words, the electronically controlled suspension device according to the present invention performs two-stage anti-nose dive attitude control by using both when the brake switch is turned on and when the acceleration sensor detects longitudinal acceleration of a set vehicle speed value or more. This is what I decided to do.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electronically controlled suspension device according to an embodiment of the present invention will be described below with reference to the drawings. In Figure 1, S _FR is a suspension unit for the right front wheel of a car, S _FL is a suspension unit for the left front wheel, S _RR is a suspension unit for the right rear wheel, and S _RL is a suspension unit for the left rear wheel. . Each suspension unit
Since S _FR , S _FL , S _RL , and S _RR have the same structure, only the structure of the suspension unit S _RL is shown. The suspension unit S _RL has a main air spring chamber 11, a sub air spring chamber 12, and a shock absorber 1.
3. Consists of a coil spring (not shown) used as an auxiliary spring. Further, 14 is an actuator for switching the damping force of the shock absorber 13 to hard or soft, and 15 is a bellows. Note that the actuator 14
The main air spring chamber 11 and the sub air spring chamber 12 are
Communication and non-communication are controlled, and the air spring reaction force is switched between hard and soft.

Further, 16 is an air cleaner. The air sent from the air cleaner 16 is sent to the dryer 18 via an outside air cutoff solenoid valve 17. The air dried by the dryer 18 is compressed by a compressor 19 and stored in a reserve tank 21 via a check valve 20. Note that 191 is a compressor relay, and this relay 191 is controlled by a signal from a control unit 36, which will be described later. The reserve tank 21 is equipped with an air supply solenoid valve 221.
224 are connected to the main and auxiliary air spring chambers 11 and 12 of each suspension unit S _RL to S _FL via the air supply piping 23 in which air supply pipes 224 are installed. In addition, the main and sub air spring chambers 1 of the suspension units S _RL and S _RR
1 and 12 are connected by a communication pipe 25 in which a communication solenoid valve 241 is installed, and the main and sub air spring chambers 1 of the suspension units S _FL and S _FR are
1 and 12 are connected by a communication pipe 26 in which a communication solenoid valve 242 is interposed. Also,
The main and auxiliary air spring chambers 11 and 12 of each of the above-mentioned suspension units S _RL to S _FL include an exhaust pipe 28 in which exhaust solenoid valves 271 to 274 are installed, a check valve 29, a dryer 18, a solenoid valve 17, and an air cleaner. 16 to the atmosphere. A piping 31 in which a solenoid valve 30 for selecting an air supply side flow path is interposed is arranged in parallel with the air supply piping 23 . Furthermore, a pipe 33 in which an exhaust side flow path selection solenoid valve 32 is interposed is arranged in parallel with the exhaust pipe 28 . Further, a hard/soft switching solenoid valve 34 is interposed between the air supply pipe 23 and the actuator 14, and the pressure of the compressed air stored in the reserve tank 21 is controlled by a pressure switch 35. Detected. The detection signal of this pressure switch 35 is sent to a control unit 36. Also, 3
A pressure switch 7 is connected to the communication pipe 25 and detects the internal pressure of the main and auxiliary air spring chambers 11 and 12 of the rear wheel suspension units S _RR and S _RL . A detection signal from this pressure switch 37 is sent to the control unit 36. Also, 38F
38R is a front vehicle height sensor attached to the lower arm 39 on the front right side of the automobile to detect the front vehicle height (front vehicle height), and 38R is attached to the lateral rod 40 on the rear left side of the automobile to detect the rear vehicle height (rear vehicle height). This is a rear vehicle height sensor that detects vehicle height.
Vehicle height detection signals output from the vehicle height sensors 38F and 38R are input to the control unit 36. The above sensors 38F and 38R are hall
One of the IC elements and magnets is attached to the wheel side and the other to the vehicle body side, and the distance from the normal vehicle height level and the low or high vehicle height level is detected respectively. Further, 41 is a vehicle speed sensor that detects the vehicle speed, and a detection signal outputted from this vehicle speed sensor 41 is inputted to the control unit 36. Furthermore, 42 is a steering wheel steering angle sensor that detects the steering angle of the steering wheel 43, and this sensor 42 sends a steering wheel steering angle detection signal to the control unit 3.
It is output to 6. In addition, 44 is acceleration (G) as a vehicle body posture sensor that detects changes in vehicle body posture.
The acceleration sensor 44 is designed to detect changes in pitch, roll, and yaw of the vehicle body on the vehicle's springs. For example, when there is no acceleration, the weight is in a hanging state, and the light from the light emitting diode is blocked by the shielding plate and does not reach the photodiode, so that it is detected that there is no acceleration. and,
When acceleration acts back and forth, left and right, or up and down, the weight tilts or moves,
The acceleration state of the vehicle body is detected. Furthermore, 45 is a vehicle height selection switch that sets the vehicle height to high vehicle height (HIGH), low vehicle height (LOW), and vehicle height adjustment (AUTO);
Reference numeral 46 denotes an attitude control selection switch for selecting attitude control to prevent the vehicle from rolling.
Signals from the switches 45 and 46 are input to the control unit 36. Further, numeral 47 is an oil pressure indicator that indicates whether the oil pressure of the engine oil has reached a predetermined value and the amount of oil pressure, and the display operation of this oil pressure indicator 47 is controlled by the control unit 36. A brake switch 48 detects the depression and amount of depression of the brake, and its detection signal is input to the control unit 36. Further, reference numeral 49 denotes an accelerator opening sensor for detecting the opening of the accelerator, and an accelerator opening signal outputted from this sensor 49 is input to the control unit 36. Furthermore, 50 is an engine rotation speed sensor that detects the engine rotation speed, and this sensor 50 outputs an engine rotation speed signal to the control unit 36. Furthermore, 51 is an ignition key switch, the operation signal of which is sent to the control unit 3 mentioned above.
6 is output. A gear position sensor 52 detects the gear position (shift position), and this sensor 52 outputs a gear position signal to the control unit 36.

In addition, the above-mentioned solenoid valves 17, 221 to 2
24, 271 to 274, 30, 32, 34 are normally closed valves, the solenoid valves 241 and 24
2 is a normally open valve. All of these solenoid valves are two-way valves, and their two states are shown in FIG. Figure 2A shows a state in which the solenoid valve is driven, and in this state compressed air moves as indicated by arrows _a1 to _a2 . On the other hand, when the solenoid valve is not driven, the situation is as shown in FIG. B, and there is no flow of compressed air.

Here, FIG. 3 shows a piping system in which this electronically controlled suspension device is applied to an actual vehicle. In this case, the reserve tank 21 in FIG. 1 is divided into a front reserve tank 21a and a rear reserve tank 21b, and at the same time, the air supply side flow path selection valve 30 is also divided into a front reserve tank 30a and a rear reserve tank 30b. Ru. Similarly, the hard/soft switching solenoid valve 34 is also set to the front 34a.
and rear 34b.

Next, the operation of the electronically controlled suspension device configured as described above will be explained. This suspension device is equipped with a vehicle height adjustment function and an attitude control function.Hereinafter, the vehicle height adjustment function and then the attitude control function will be explained with reference to FIG.

This device allows you to set a target vehicle height in three levels: "high,""medium," and "low." First, front vehicle height sensor 3
If the front vehicle height detected by 8F is lower than the target vehicle height, the front vehicle height is raised. In this case, as shown in FIG.
242 is driven. As a result, the compressed air from the reserve tank 21 is transferred to the small diameter air supply pipe L ₁ ,
The air is sent to the front suspension units S _FL and S _FR via the air supply piping 23 and the front side air supply solenoid valves 223 and 224. This raises the front vehicle height.

On the other hand, when the rear vehicle height detected by the rear vehicle height sensor 38R is lower than the target vehicle height, the rear vehicle height is raised. In this case, as shown in FIG. 4, the rear air supply solenoid valves 221 and 22 are controlled by the control unit 36.
2. The front side and rear side communication solenoid valves 241 and 242 are driven. As a result, compressed air from the reserve tank 21 is sent to the rear suspension units S _RL and S _RR via the small-diameter air supply pipe L ₁ , the air supply pipe 23 , and the rear side air supply solenoid valves 221 and 222. Sent. This raises the rear vehicle height.

Next, if both the front and rear vehicle heights are lower than the target vehicle height, the front and rear vehicle heights are raised. In this case, the front side and rear side air supply solenoid valves 221 to 224 and the front side and rear side communication solenoid valves 241 and 242 are controlled by the control unit 36.
is driven. As a result, the reserve tank 21
The compressed air is delivered to each suspension unit S _FL , S _FR , S _RL , through the small-diameter air supply pipe L ₁ , air supply pipe 23 , and air supply solenoid valves 221 to 224.
Sent to S _RR . As a result, the front and rear vehicle heights are raised.

Next, if the front vehicle height detected by the front vehicle height sensor 38F is higher than the target vehicle height, the front vehicle height is lowered. In this case, front side exhaust solenoid valves 273, 274, front side and rear side communication solenoid valve 24
1,242 are driven. As a result, the air discharged from the main air spring chamber 11 of the front suspension units S _FL and S _FR is routed through the front side exhaust solenoid valves 273 and 274 and the exhaust pipe 2.
8, narrow diameter exhaust pipe L ₂ , check valve 29,
It is released to the atmosphere via the dryer 18, valve 17, and air cleaner 16. Here, dryer 18
By passing the exhaust gas in the direction of the dashed arrow x,
The dryer 18 is regenerated.

Next, when the rear vehicle height detected by the rear vehicle height sensor 38R is higher than the target vehicle height, the rear vehicle height is lowered. In this case, the rear exhaust solenoid valves 271, 272 and the communication solenoid valves 241, 242 are driven. As a result, the air exhausted from the main air spring chamber 11 of the rear suspension units S _RL and S _RR is routed through the rear exhaust solenoid valves 271 and 272, the exhaust pipe 28, the small diameter exhaust pipe L ₂ , and the check valve 29. ,
It is released to the atmosphere via the dryer 18, valve 17, and air cleaner 16.

Next, if the front and rear vehicle heights are respectively higher than the target vehicle height, the air is exhausted from the front and rear suspension units S _FL , S _FR , S _RL , and S _RR . In this case, each exhaust solenoid valve 271 to 274 and each communication solenoid valve 241, 242 are turned on. Therefore, the air exhausted from the main air spring chamber 11 of each suspension unit is transferred to each exhaust solenoid valve 271.
~274, exhaust pipe 28, small diameter exhaust pipe _L2 , check valve 29, dryer 18, valve 17,
It is released to the atmosphere via the air cleaner 16. This lowers the front and rear vehicle heights.

Next, vehicle body posture control when the steering wheel is steered to the right will be explained. In this case, the vehicle height on the left side decreases and the vehicle height on the right side increases, so air is supplied to the left suspension units S _FL and S _RL , and air is exhausted from the right suspension units S _FR and S _RR . . In other words, when the steering wheel steering sensor 42 detects steering of the steering wheel 43 to the right by a predetermined angle or more, a control signal from the control unit 36 causes the right air supply solenoid valve 2 to
21, 223, right exhaust solenoid valve 2
72, 274 and each flow path selection solenoid valve 30, 32 are turned on for a certain period of time. As a result, the compressed air sent from the reserve tank 21 is routed through the air supply flow path selection valve 30, the large-diameter air supply pipe 31, the air supply pipe 23, and the left air supply solenoid valve 22.
Air is supplied to the left suspension units S _FL and S _RL via 1,223. Simultaneously with this air supply operation, air is discharged from the main air spring chambers 11 of the right suspension units S _FR and S _RR through the right exhaust solenoid valves 272, 274, the exhaust piping 28, and the exhaust flow path selection. It is released to the atmosphere via the valve 32, large-diameter exhaust pipe 33, check valve 29, dryer 18, valve 17, and air cleaner 16. In this way, the vehicle body can be kept horizontal when the steering wheel 43 is steered to the right. After the valves are opened for a certain period of time, the left air supply solenoid valves 221, 223 and the right exhaust solenoid valves 272, 274 are closed and maintained in that state. When the right steering of the handle 43 is completed, each of the flow path selection valves 30,
32 is turned off and each communication valve 241, 2 is turned off.
42 is turned on and attitude control is canceled. As a result, the vehicle body returns to the neutral position.

Next, vehicle body posture control when the steering wheel 43 is steered to the left will be described. In this case, the vehicle height on the right side decreases and the vehicle height on the left side increases, so air is supplied to the right suspension units S _FR and S _RR , and air is exhausted from the left suspension units S _FL and S _RL . . In other words, when the steering wheel steering angle sensor 42 detects that the steering wheel 43 is being steered to the left by a predetermined angle or more, the control unit 36
The right side air supply solenoid valves 222, 224, the left side exhaust solenoid valves 271, 273, and each flow path selection solenoid valve 30, 32 are turned on for a certain period of time by a control signal from the control signal. As a result, the compressed air sent from the reserve tank 21 is routed through the air supply flow path selection valve 30 and the large diameter air supply pipe 3.
1. Air is supplied to the right suspension units S _FR and S _RR via the air supply piping 23 and the right air supply solenoid valves 222 and 224. Also, at the same time as this air supply operation, the left suspension unit
The air exhausted from the main air spring chamber 11 of S _FL and S _RL is discharged through the left exhaust solenoid valves 271 and 27.
3, exhaust pipe 28, exhaust flow path selection valve 32,
It is released to the atmosphere via the large diameter exhaust pipe 33, check valve 29, dryer 18, valve 17, and air cleaner 16. In this way, the handle 43
The vehicle body can be kept level when the vehicle is steered to the left. After the valve is opened for a certain period of time, the air supply solenoid valve 222, 22 on the right side
4. Left exhaust solenoid valve 271, 27
3 is closed and that state is maintained. When the left steering of the handle 43 is completed, the flow path selection valves 30 and 32 are turned off, and the communication valves 241 and 242 are turned on, thereby canceling attitude control. As a result, the vehicle body returns to the neutral position.

Next, we will discuss the fourth section regarding posture control to prevent nose dive, where the front vehicle height lowers during braking.
This will be explained in detail with reference to the flowchart shown in FIG. 5 along with the drawings.

First, when the ignition key is turned on, the control unit 36 performs the processing shown in FIG. In step S1, vehicle speed data stored in a memory area within the control unit 36 is set to zero. Next, step S2
Then, the contents T _M of the map memory are reset. The process then proceeds to step S3, where it is confirmed that the flow path selection solenoid valves 30 and 32 are open. Then, the process proceeds to step S4, where it is determined whether the brake switch 48 is on, that is, whether the brake pedal is being depressed by the driver.
If the determination in step S4 is ``YES'', the process advances to step S5, where the vehicle speed data is read into a predetermined memory area within the control unit 36. That is, data from the vehicle speed sensor 41 is read into the control unit 36. Then, proceeding to step S6, the vehicle speed sensor 41 is
Based on the vehicle speed data from , it is determined whether the current vehicle speed is running at a preset speed of 3 km/h or higher. “NO” here, i.e. vehicle speed 3km/h
If it is determined that the nose dive prevention control is not necessary, the above steps are performed.
Return to S2. On the other hand, if "YES" is determined in this step S6, that is, if it is determined that the brake pedal has been depressed while the vehicle is running and braking has started, the control unit 36 will first proceed to step S6.
At S7, each flow path selection valve 30, 32 is turned off and closed, and the process proceeds to step S8.
The front air intake valves 223, 224 and the rear exhaust valves 271, 272 are turned on and opened for a certain period of time _T1 seconds. As a result, the compressed air from the reserve tank 21 is transferred to the front suspension units S _FL , S _FR through the small diameter air supply pipe L ₁ , the air supply pipe 23 and the front side air supply valves 223 , 2 .
At the same time, air is gradually supplied through T ₁ second through 24,
The air in the air spring chambers 11 of the rear suspension units S _RL and S _RR is pumped through the rear exhaust valves 271,
272 and exhaust pipe 28, small diameter exhaust pipe _L2 , check valve 29, dryer 18, valve 17,
The atmosphere is gradually released through the air cleaner 16 for T ₁ seconds. As a result, the spring reaction forces of the front suspension units S _FL and S _FR gradually become stronger, and at the same time the spring reaction forces of the rear suspension units S _RL and S _RR gradually weaken, preventing nose dive at the initial stage of braking. The vehicle body is held horizontally.

In this initial braking state, step S9
When the acceleration in the longitudinal direction of the vehicle body (in this case, the rearward acceleration due to deceleration) reaches a predetermined value or more,
When the acceleration (G) sensor 44 is turned on, the step
Proceed to S10. In other words, when the brake pedal is depressed further to start reliable braking, the control unit 36 confirms in step S10 that each flow path selection valve 30, 32 is closed, and proceeds to step S11. Again, the front air intake valves 223, 224 and the rear exhaust valves 271, 272 are operated for a certain period of time.
T It is turned on and opened for only ₂ seconds. Here, it is assumed that T ₁ <T ₂ . As a result, compressed air from the reserve tank 21 is supplied to the front suspension units S _FL , S _FR via the small diameter air supply pipe L ₁ , the air supply pipe 23 and the front air supply valves 223 , 224 . At the same time as the air is gradually supplied for ₂ seconds, the air in the air spring chambers 11 of the rear suspension units S _RL and S _RR is pumped through the rear exhaust valves 271 and 27.
2, the exhaust pipe 28, the small-diameter exhaust pipe _L2 , the check valve 29, the dryer 18, the valve 17, and the air cleaner 16, and then gradually released to the atmosphere for T ₂ seconds. As a result, the spring reaction force on the front suspension units S _FL , S _FR becomes even stronger, and at the same time, the spring reaction force on the front suspension units S _RL , S _RR increases.
The spring reaction force becomes even weaker, preventing nose dive and keeping the car body horizontal even under full-scale braking conditions.

Next, the process returns to step S9 and the acceleration sensor 44 is
is turned off and the determination is “NO”, step S12
If the answer is ``YES'', the process proceeds to step S13. That is, when the amount of depression of the brake pedal becomes weak during braking and the longitudinal acceleration of the vehicle body falls below a predetermined value, the control unit 36 controls each flow path selection valve 3 in step S13.
It is confirmed that 0 and 32 are closed, and
Proceed to step S14 and install front exhaust valve 2.
73, 274 and rear air intake valves 221, 22
2 is turned on and opened for the above-mentioned fixed time T ₂ seconds.
This allows the front suspension unit to
The air in the air spring chamber 11 of S _FL and S _FR flows from the front exhaust valves 273, 274 to the air cleaner 16.
At the same time, the compressed air from the reserve tank 21 is supplied to the rear suspension units S _RL and S _RR via the rear air supply valves 221 and 222 to the atmosphere T _{for 2} seconds. Air is gradually supplied for ₂ seconds. As a result, the attitude control at step S11 due to the acceleration sensor 44 being turned on is canceled, and the attitude control state at the initial stage of braking is returned to at step S8. That is, the lifting of the front part of the vehicle body that occurs when the braking force is weakened, so-called "tilting due to braking relaxation," is prevented, and the vehicle body is kept horizontal.

In this way, the attitude control state is approximately returned to the initial state of braking, or if it is determined as "NO" in step S12, that is, the acceleration sensor 44 remains in the OFF state in step S9. If so, proceed to the next step S15. In step S15, it is determined whether the vehicle is running at a speed of 3 km/h or more in the same manner as in step S6, and the determination is ``YES'' here.
Further, the process proceeds to step S16, and if it is determined that the brake switch 48 is on in the running state, the above step is executed as a braking operation is in progress.
Return to S15.

If the result of step S15 is "NO", that is, the vehicle speed has decreased to less than 3 km/h where nose dive does not occur, or the result of step S16 is
If the answer is "YES", that is, if it is determined that the brake switch 48 is turned off and the braking is released even if the vehicle is traveling at a speed of 3 km/h or more, the step
Proceed to S17. As a result, the control unit 36 confirms that each flow path selection valve 30, 32 is closed, and the process proceeds to step S18, in which the front exhaust valves 273, 274 and the rear air intake valves 221, 222 are fixed time
T Turns on and opens for only ₁ second. As a result, the air in the air spring chambers 11 of the front suspension units S _FL and S _FR is transferred to the front exhaust valve 2.
73,274 to the above via air cleaner 16
T At the same time as the air is gradually released to the atmosphere for ₁ second, compressed air from the reserve tank 21 flows into the rear suspension units S _RL and S _RR through the rear air supply valve 2.
21 and 222, air is gradually supplied for T ₁ seconds. As a result, the posture control at step S8 caused by turning on the brake switch 48 is released, and the vehicle returns to a stopped state at a vehicle speed of less than 3 km/h or to a normal running state. That is, the lifting of the front part of the vehicle body that occurs when the forward load due to braking is completely released, so-called "tilting due to brake release", is prevented and the vehicle body is kept horizontal.

Therefore, based on the flowchart of the anti-nose dive shown in FIG. 5 above, the attitude control for time T ₁ by the brake switch 48 and the attitude control for time T ₂ by the acceleration sensor 44 are performed in combination in stages. This enables fine-grained attitude control in response to all braking conditions, and effectively prevents nose dive from occurring in the vehicle body.

Next, a description will be given of vehicle body attitude control that prevents the front vehicle height from squatting when the accelerator is depressed when the vehicle starts and accelerates. In other words, when you press the accelerator to start accelerating, the front vehicle height rises and the rear vehicle height decreases.
The front vehicle height is lowered and the rear vehicle height is raised. That is, the acceleration in the longitudinal direction of the vehicle body (in this case, forward acceleration) detected by the acceleration sensor 44
is greater than a predetermined value, or when the accelerator opening detected by the accelerator opening sensor 49 is greater than a predetermined value, the control unit 36
, the flow path selection valves 30 and 32 are turned on, and the front exhaust valves 273 and 2 are turned on.
74 and the rear air supply valves 221 and 222 are turned on for a certain period of time. Therefore, the compressed air from the reserve tank 21 is transferred to the air supply side flow path selection valve 3.
0, large diameter air supply pipe 31 and rear side air supply valve 22
1,222 to the main air spring chambers 11 of the rear suspension units S _RL and S _RR . This raises the rear vehicle height. On the other hand, the air discharged from the main air spring chamber 11 of the front suspension units S _FL and S _FR is supplied to the front side exhaust valves 273 and 274, the exhaust side flow path selection valve 32, the large diameter exhaust pipe 33, the dryer 18, It is released to the atmosphere via a valve 17 and an air cleaner 16. This lowers the front vehicle height and keeps the vehicle level. Next, when the squat by depressing the accelerator is completed, the front air intake valve 22 is controlled by the control unit 36.
3,224 and rear exhaust valve 271,272
is turned on. Therefore, the air in the main air spring chambers 11 of the rear suspension units S _RL and S _RR is
Rear side exhaust valve 271, 272 ~ dryer 16
released to the atmosphere through. On the other hand, the compressed air in the reserve tank 21 is sent to the main air spring chambers 11 of the front suspension units S _FL and S _FR via the air supply side flow path selection valve 30 to the front side air supply valves 223 and 224. This prevents tilting from the rear of the vehicle when the starting acceleration state ends.
The vehicle body is returned to normal running condition.

Although the above embodiments have been explained using an air suspension system that uses compressed air, this device can be applied to all fluid suspension systems, such as hydroneumatic suspension systems that use both liquid and gas. Of course, it is possible to implement it.

〔Effect of the invention〕

As described above, according to the present invention, anti-nose dive attitude control during braking is performed in two stages: when the brake switch is turned on and when the acceleration in the longitudinal direction of the vehicle body exceeds a predetermined value. Therefore, even if the braking force changes significantly from the start to the end of braking, the car body will always be kept horizontal, effectively preventing the nose dive that might occur in the car body. , it is possible to significantly reduce the sense of discomfort given to the occupants.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an electronically controlled suspension device according to an embodiment of the present invention, and FIGS. 2A and 2B are respectively on and off states of a solenoid valve used in the electronically controlled suspension device shown in FIG. 1. FIG. 3 is a diagram showing the piping system when the electronically controlled suspension device in FIG. FIG. 5 is a flowchart showing the operation of anti-nose dive attitude control by the electronically controlled suspension device. S _FL , S _FR ...Suspension unit for front wheels, S _RL , S _RR ...Suspension unit for rear wheels, 11...Main air spring chamber, 21
. . . Reserve tank, 221 to 224 . . . Air supply solenoid valve, 271 to 274 . . . Exhaust air solenoid valve, 36 .

Claims (1)

[Scope of Claims] 1. A suspension unit provided for each wheel and provided with a fluid spring chamber, and a supply control valve and a discharge control valve provided for each suspension unit and connected to the fluid spring chamber. A control valve, a vehicle speed sensor that detects vehicle speed, an acceleration sensor that detects acceleration acting in the longitudinal direction of the vehicle body, a brake switch that detects depression of the brake, and a vehicle speed that is equal to or higher than a set vehicle speed is detected by the vehicle speed sensor, and When the brake switch detects that the brake is depressed, the front wheel supply control valve and the rear wheel discharge control valve are activated for a certain period of time.
After _that , if the acceleration sensor detects a deceleration of more than a predetermined value, the front wheel intake control valve and the rear wheel discharge control valve are opened for a certain period of time _T2 . 1. An electronically controlled suspension device comprising: control means for controlling an anti-nose dive by opening the suspension device.