JPS63279914A - Control method for active suspension device for automobile - Google Patents

Abstract

PURPOSE:To improve performance of active suspension by a method wherein the loading state of a vehicle is discriminated, and an amount of command of a controller to a control valve is varied and controlled responding to the discriminating result. CONSTITUTION:A controller 6 computes a command air flow rate by means of detecting signals from a vertical acceleration sensor 5 and a relative displacement sensor 4. The injecting valve or the discharge valve of a control valve 7 is controlled, and injection and discharge are controlled so that a command flow rate is adjusted to a total value. In this case, a signal detected by a pressure sensor 3 is inputted to a loading condition deciding circuit to decide a loading condition. A gain value is inputted to the gain value switching part of the controller 6 to steppedly switch the gain value to change a command flow rate. This constitution, since a command amount is corrected according to a loading state, enables improvement of performance of an active suspension device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of controlling an active suspension system for an automobile.

Conventional technology In automobiles, the relative displacement (amount of relative displacement) in the vertical direction between the wheel axle and the vehicle body and the time rate of change of this relative displacement (relative displacement speed in the vertical direction) are used to determine the relative displacement of a suspension using a gas-liquid fluid spring. An active suspension in which the damping force characteristics of a gas-liquid fluid spring are variably controlled has been developed and has already been disclosed in Japanese Patent Application Laid-Open No. 59-213510.

Problems to be Solved by the Invention In the active suspension as described above, sensors that detect various behaviors of the suspension when the vehicle is running and when the vehicle is stopped, such as a sensor that detects the relative displacement between the sprung mass and the unsprung mass, and those sensors. By combining a controller that instructs the opening and closing of control valves based on signals from sensors to control the flow of fluid into and out of the suspension, damper characteristics can be adjusted according to various vehicle conditions.

It is possible to obtain an active suspension device that can variably control the quality of the suspension, such as spring characteristics, and can also control the attitude of the vehicle.

In such an active suspension device,
Normally, the command amount determined by the controller is converted into the valve opening time and valve opening amount of the control valves (injection valve and discharge valve), and a valve opening/closing signal is issued.

However, the amount of fluid that actually passes through the injection valve and discharge valve is
It varies depending on the pressure difference between the high-pressure tank and the fluid in the suspension during injection, and the pressure difference between the suspension and the low-pressure tank during discharge.

Therefore, even though the internal pressures of the high-pressure side tank and low-pressure side tank are maintained at approximately the set value by controlling the operation of the combresor based on the signals from the pressure sensors installed in each, the internal pressure of the suspension differs between, for example, when a single passenger is riding and when the vehicle is fully loaded. In particular, the internal pressure of the rear suspension changes greatly between when the driver is alone and when multiple people are in the rear seats and luggage is loaded into the rear trunk, so the loading conditions If they are different, the actual injection and discharge amounts for the same instructed amount will vary greatly, resulting in a problem that the active suspension device cannot fully demonstrate its original function.

Means for Solving the Problems The present invention uses a fluid closed circuit system as described above,
Based on the signals of sensors that detect the behavior of the vehicle, the controller multiplies the signal value by a gain value to calculate the instruction amount,
In an active suspension system for an automobile that controls fluid injection and discharge into a suspension by issuing a valve opening/closing signal based on the instruction amount and controlling opening/closing of a control valve, a sensor detects a loading state of the vehicle;
The controller is provided with a circuit that determines the loading status of the vehicle based on the signal from the senna, and a means for switching the gain value to a value that matches the loading status based on the judgment of the circuit,
This system is characterized by changing and controlling the instruction amount calculated by the controller according to the loading situation.

As a result of the above, in eaves-edge situations such as when one person is riding, the fluid pressure inside the suspension is low and the actual amount of injection passing through the injection valve section is higher than in the planting situation, and the actual amount of discharge passing through the discharge valve section is in a constant volume situation. Therefore, at the edge of the eaves, the amount specified on the injection side should be smaller than when planting, and the amount specified on the discharge side should be larger than when planting. Conversely, when fully loaded, the indicated amount on the injection side is greater than when the load is constant, and the indicated amount on the discharge side is smaller than when planting.

By doing this, under the same vehicle behavior conditions, the actual injection and discharge amounts will always be the same even if the loading situation changes, making it possible to significantly improve the active suspension performance.

Example An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram of a closed air circuit system to which the present invention is applied, where l is an air suspension, and the air suspension l consists of a sprung member, that is, a vehicle body side member 2, and an unsprung member, that is, a wheel axle support member (not shown). The spring is installed between the air suspension and supports the weight of the vehicle using the volumetric elasticity of the air sealed in the air suspension. The vehicle body side member 2 relative to the wheel axle is
The height of the vehicle, that is, the vehicle height, and the spring constant can be changed.

The above-mentioned air suspension l is provided in each of the front, rear, left and right suspensions, and each air suspension section is equipped with a relative displacement sensor 4 that detects the relative displacement in the vertical direction between the sprung member and the unsprung member. , a vertical acceleration sensor 5 that detects vertical acceleration of the sprung member;
Pressure sensor 3 that detects air pressure inside the air suspension
The signals from these sensors 3, 4.5 are input to a controller 6, which will be described later, but in order to simplify the explanation, FIG. Only one of the air suspensions is shown, and the others are omitted.

Reference numeral 7 denotes a flow control valve consisting of an injection valve 71 for injecting air into the air suspension l and a discharge valve 72 for discharging the air inside the air suspension l.The flow control valve 7 has two valves for injection and discharge. 71.72 is taken as one set, and this is 4
The front, rear, left, and right air suspensions each have air injection and exhaust that can be controlled independently.

8 is a high pressure air tank, 9 is a low pressure air tank, and the high pressure air tank 8 is set to a sufficiently higher air pressure than the air pressure inside the air suspension so that air can be immediately injected into the air suspension l when the injection valve 71 is opened. The low-pressure air tank 9 is set at a sufficiently lower air pressure than the air pressure inside the air suspension 1 so that when the discharge valve 72 opens, the air inside the air suspension 1 is immediately discharged into the low-pressure air tank 9.
When the air pressure in the near compressor 10 falls below the set value,
operates to suck out and compress the air in the low-pressure air tank 9 and pressurize it into the high-pressure air tank 8. When the air pressure in the low-pressure air tank 9 exceeds a set value, the near compressor 10 operates to compress the air in the high-pressure air tank 8 in the same way as above. It is controlled so that it is press-fitted inside. High pressure air tank 8. If the balance of the low-pressure air tank 9 is lost and the amount of air in the system is too large, a check valve (not shown) is opened from the high-pressure tank 8 and the air is exhausted to the atmosphere via a silencer. The low-pressure side check valve (not shown) opens, allowing atmospheric air to flow into the compressor lO, but in principle, the air intake and extraction from the air suspension is almost balanced, so depending on that balance, the flow of air into the atmosphere is controlled. High pressure air tank with little venting or replenishment of air from the atmosphere 8. The air pressure in the low-pressure air tank 9 is always maintained substantially within the set pressure range, forming a closed air circuit.

Next, the control mode by the controller 6 will be explained with reference to FIG. 2.

Figure 2 shows a control circuit for one of the four front, rear, left and right suspensions, and the controller 6 is equipped with four sets of control circuits as shown in Figure 2, and each suspension is independently described below. control.

That is, the vertical acceleration signal X of the vertical acceleration sensor 5, which detects the vertical acceleration of the vehicle body and emits a vertical acceleration signal corresponding to the vertical acceleration, is filtered in a low frequency range (for example, a range around 0.1 Hz or less) by the bypass filter 51. The vertical acceleration sensor and the acceleration sensor are cut and passed through the differentiating circuit 5a, and the acceleration sensor is divided into two types, each with a gain GI.
IG2 is multiplied and converted into indicated airflow m Q 1 and G2.

The relative displacement signal (■) of the relative displacement sensor 4, which detects the vertical relative displacement between the vehicle body and the wheels and generates a relative displacement signal according to the relative displacement, is sent to the reference position command circuit 11a by selection of the vehicle height adjustment switch 11, which will be described later. By subtracting the reference position signal VO outputted through the differential circuit 4a, the actual relative displacement signal from the reference position is obtained. It is divided into two groups, each with a gain of G3. G4 is multiplied and converted to the commanded airflow ff1ch and Qs.

The vehicle height adjustment switch 11 is, for example, a changeover switch for switching from normal vehicle height to high vehicle height. When the vehicle height adjustment switch 11 is switched from normal to high, air is injected into the air suspension l and the vehicle body member 2 relative to the wheel axle is injected. Increase the height by the set value and use that height as the standard vehicle height.

When the small height adjustment switch 11 is switched from high to normal, the air inside the air suspension l is exhausted and the vehicle height is set to a low normal standard vehicle height.

Therefore, if the relative displacement sensor 4 is set to detect the relative displacement from the normal reference vehicle height as its reference position, when the vehicle height adjustment switch 7A is switched to high, the relative displacement sensor 4 From the relative displacement detected by
The value obtained by subtracting the difference between the normal reference vehicle height and the high reference vehicle height becomes the actual relative displacement with the high reference vehicle height as the reference position.

In addition to the manual switch, vehicle height adjustment as described above may also be performed automatically using signals such as vehicle speed.

However, if the vehicle is an automatic type that does not have a vehicle height adjustment mechanism such as the vehicle height adjustment switch 11, it goes without saying that the relative displacement signal V of the relative displacement sensor 4 will always be equal to the actual relative displacement signal.

Indicated air flow rate Q+, Q2 obtained as above
, (h and Q4 are added in the adder circuit 12 to obtain the total commanded air flow rate Q, and an output is issued from the valve control signal generation circuit 13 to the flow rate control valve 7, and either the resident valve or the discharge valve of the flow rate control valve 7 One side is opened, and injection or discharge corresponding to the total instructed flow rate Q is performed.

In general, the flow control valve originally has an integral effect as a flow control characteristic, so the air control in the vertical acceleration sensor l, which is one of the control elements of the controller 6, becomes control of the vertical acceleration term in the suspension section, and the inertia force of the vehicle body, that is, the apparent appearance of the vehicle body. Similarly, the control using the vertical acceleration signal Control based on the relative displacement speed signal controls the relative displacement term, which works to change the spring characteristics of the suspension section, and control based on the actual relative displacement signal controls the integral term of the relative displacement, which changes the spring characteristics from the reference position. The function is to eliminate the deviation (relative displacement) and restore the vehicle height to the standard vehicle height.

Therefore, basically, for each wheel suspension, control is performed to exhaust the air in the air chamber of air suspension 1 when both the vertical and maxillary accelerations of the vehicle body are upward, and to inject air into the air chamber when they are downward. The air suspension 1 becomes soft in response to input from the road surface and is controlled in a direction that does not transmit vibrations to the vehicle body, thereby suppressing vertical vibrations of the vehicle body. With respect to the load movement at the time, the air suspension moves one step in the direction that controls the roll and pitching of the vehicle body (apparently in the direction of increasing the rigidity of the air suspension l).

The vertical relative displacement speed and vertical relative displacement of the suspension are
If the air suspension 1 is in the direction of extension, the air in the air chamber is exhausted, and if it is in the direction of contraction, air is injected into the air chamber, thereby working to return the relative displacement of the suspension to the reference position.

For inputs from the vehicle body, such as load movement, control using signals from the vertical acceleration sensor 5 and relative displacement sensor 4 both work in the same direction, making it easy to maintain the vehicle body in a horizontal state at all times.

Using the vertical acceleration sensor 5, when the vertical acceleration and the vertical acceleration are upward as described above, the air suspension l
If the air is discharged and the air is injected into the air suspension l when the vehicle is heading downward, for example, when the vehicle approaches the uphill road and upward acceleration occurs, the air continues to be discharged, or when the vehicle approaches the downhill road. This is extremely inconvenient as it requires continuous air injection, but the frequency of the vertical acceleration of the vehicle body when approaching a slope is extremely low compared to the frequency of vertical acceleration on an uneven road surface. As shown in the second figure, by interposing a bypass filter 51 in the signal circuit of the vertical acceleration sensor 5 to cut extremely low frequency signals, the signal generated by the vertical acceleration sensor 5 when climbing or descending is cut. is,
Only the control function that returns the suspension to its reference position using the signal from the relative displacement sensor 4 operates, allowing the vehicle to travel up and down hills while maintaining a constant vehicle height.

In addition, in FIG. 2, a low-pass filter is provided in the sensor signal input circuit of the lower jaw acceleration sensor 5 or the sensor signal input circuit of the lower jaw speed sensor 5 and the relative displacement sensor 4 to cut high frequency components of, for example, about 4 to 5 Hz. It is also possible to significantly reduce the consumption of air by greatly restricting the air intake/extraction control for vibrations in the Takaoka wavenumber range.

The control described in L can perform the above-mentioned functions by accurately injecting and exhausting the air suspension 1 according to the total flow rate Q commanded by the controller. The actual flow rate passing through the valve 71 and the discharge valve 72 is the same as that of the high pressure air tank 8 and the air suspension 1.
The pressure difference between the air suspension 1 and the low pressure air tank 9 varies considerably depending on the pressure difference between the air suspension 1 and the low pressure air tank 9. Assuming that both the high-pressure and low-pressure air tanks 8 and 9 are always maintained within a substantially constant pressure range, the pressure difference will vary depending on the loading conditions of the vehicle.

Therefore, in the present invention, a pressure sensor 3 is provided in the air suspension, and the signal from this pressure sensor 3 determines, for example, whether the vehicle is in an eaves-edge state such as when a single person is riding, a constant load state, or a fully loaded state. The loading condition determining circuit 3a determines the v1 loading condition of the loading condition determining circuit 3a, and the gain value switching units o, , o2 based on the loading condition determination of the loading condition determining circuit 3a.

03 and 04 to perform control to change the commanded flow rate by changing each gain value in stages.

That is, the vertical acceleration sensor 5. Vertical jerk term based on each output signal from the relative displacement sensor 4.

The respective gain values for determining the indicated flow rates Q+ , G2 , G3 , and Qa of the vertical acceleration term, actual relative displacement velocity term, and actual relative displacement term are, for example, gain values G+ , G2 , G3 , Ga in a constant volume state. , and a gain value GI+cr greater than the gain value in the planted state, G3 1G
4 and a gain value G i smaller than the gain value in the constant volume state
', G2, GN3. Gain value switching unit 01 . 02 103.04 can be set to -17 by selecting one of the three gain values mentioned above.
Q+.

G2, G3, G4 depending on the loading conditions of the vehicle,
For example, in the eaves edge state, the actual air flow rate passing through the injection valve 71 is higher than in the planted state, so the indicated flow rate on the air injection side is set smaller than in the planted state, and in the fully loaded state, the actual air flow rate is lower than in the fixed volume state. Change control is performed such that the indicated flow rate on the air injection side is made higher than in the constant volume state, and the indicated flow rate on the discharge side is reversed.

By changing and controlling the indicated flow rate according to loading conditions in this way, it is possible to obtain an appropriate actual air flow rate under all loading conditions. It is possible to significantly improve the original functions of an active suspension, such as control and vehicle attitude control.

Although the above embodiment shows an example in which the gain value is set in three stages, it may be set in two stages, or it can be set in four stages or more to obtain more detailed loading conditions. Control may be performed accordingly.

Further, the control for changing the indicated flow rate according to the loading conditions of the present invention is a method of omitting the vertical jerk term and calculating the total indicated flow rate by adding the indicated flow rate of the vertical acceleration term, relative displacement velocity term, and relative displacement term.

Alternatively, such as the method of calculating the total indicated flow rate using only the relative displacement speed term and the relative displacement term, the indicated flow rate is calculated by multiplying the gain value based on the signal of any sensor that detects the behavior of the vehicle. It is applicable to any type of active suspension that issues valve opening/closing signals J, K to operate a flow control valve based on a commanded flow rate.

The above embodiment shows an example in which the present invention is applied to a mechanical suspension using air as a spring, but the balance between injection and discharge is sufficiently maintained in a closed air circuit, and air is supplied to the closed circuit. Alternatively, if the configuration is such that almost no discharge is required, any gas other than air can be used instead of air, and although the above embodiment shows an example using a flow rate control valve. , a pressure control valve is provided in addition to the flow control valve, and the pressure control valve calculates the indicated amount of gas to be injected or discharged based on the signals from each sensor, and injects or discharges the amount of gas corresponding to the instruction p. The present invention may be applied to a device configured to emit a signal for variably controlling the pressure setting value.

Furthermore, the present invention can also be applied to automobiles using hydropneumatic suspension. In this case, the oil pump can be operated by opening the injection valve or the discharge valve of the flow control valve in response to a valve opening/closing signal from the controller. The oil stored at a predetermined pressure in the accumulator, which is a high-pressure tank, is injected into the suspension oil cylinder, or the oil in the suspension oil cylinder is drained into the low-pressure tank, which is a reservoir. becomes. In this case as well, calculation of the instructed flow rates for injection and discharge by the controller, opening/closing control of the flow rate control valve based on the calculated flow rate, functions obtained by the control, etc. are the same as in the case of the air suspension.

Effects of the Invention As described above, the present invention includes a fluid suspension into which fluid can be taken in and out, a high pressure tank, a low pressure tank, a compressor, and a control valve that controls the fluid in and out of the suspension. Based on signals from sensors that detect the behavior of the suspension parts of each left and right wheel, the controller multiplies the signal value by a gain to calculate the amount of fluid intake/output instruction, and generates a valve opening/closing signal to open/close the control valve. In an active suspension device configured to emit a signal, a gain value for calculating the instruction amount based on the sensor signal is selected to be a different value depending on the loading conditions of the vehicle, and the instruction amount is changed and controlled according to the loading condition. As a result, the amount of fluid passing through the control valve is the same for the same vehicle behavior under any loading conditions, and the performance of the active suspension system can be significantly improved, and the configuration is simple and inexpensive. Together, they can bring about great practical effects.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention. Fig. 1 is an explanatory diagram of an air control system for controlling air injection and exhaust of an air suspension, and Fig. 2 is a block diagram showing an example of a control mode in a controller. . 1...Air suspension, 3...Pressure sensor. 4...Relative displacement sensor, 5...Vertical acceleration sensor,
6... Controller, 7... Flow rate control valve, 8...
High pressure air tank, 9...Low pressure air tank, 10...
Compressor, 11...Vehicle height adjustment switch. Figure 1

Claims (1)

[Claims] It consists of a control valve that operates based on the amount of instruction from a controller to discharge and inject fluid into the suspension that supports the vehicle body using fluid pressure, a high-pressure tank and a low-pressure tank that store the fluid, and a compressor that pressurizes the fluid. Based on the sensor signal of the sensors that detect the behavior of the suspension section, the signal is multiplied by a gain value to calculate the instruction amount, and the instruction amount is calculated based on the instruction amount. An active suspension system for an automobile is equipped with a controller that issues valve opening/closing signals of a control valve, and includes a sensor that detects the loading status of the vehicle, a circuit that determines the loading status of the vehicle based on the signal from the sensor, and the above-mentioned system based on the judgment of the circuit. A method for controlling an active suspension device for an automobile, characterized in that the controller is provided with means for switching the gain value to a value that matches the loading condition, and the instruction amount calculated by the controller is changed and controlled according to the loading condition.