JP2639691B2 - Active suspension control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for an active suspension for a vehicle.

2. Description of the Related Art According to a signal from a vehicle height sensor that detects a relative displacement between a sprung portion and a unsprung portion of an air suspension, air is injected into the suspension or air is discharged from the suspension, and the relative displacement amount is determined. Control to zero,
A device for maintaining the vehicle body posture normally has been known (for example, see Japanese Utility Model Application Laid-Open No. 58-167208). In addition to the above-described vehicle height adjusting function, the speed of relative displacement and the speed of spring Active suspensions are also known in the prior art that control the air in and out of the suspension according to the vertical acceleration and the like to control the vibration of the vehicle body (for example,
62-139709).

Problems to be Solved by the Invention In the active suspension as described above,
A high-pressure accumulator for supplying air into the air suspension, a low-pressure accumulator for collecting air discharged from the air suspension, an air compressor for supplying air from the low-pressure accumulator to the high-pressure accumulator, and control for controlling air injection and discharge of the air suspension. A closed circuit of air consisting of a valve (composed of a combination of an injection valve and a discharge valve) is constructed, and signals of relative displacement between sprung and unsprung, relative displacement speed, vertical acceleration on the sprung, etc. In response to the input, the controller determines the flow rate of the air to be discharged from the injection area by calculation, issues a signal to open and close the control valve, controls the injection and discharge of air to the suspension, and controls the high-pressure accumulator and A signal that controls the operation of the air compressor based on a signal that detects the internal pressure of the low-pressure accumulator It emitting adapted to hold the respective set pressure range high and low pressure of the accumulator internal pressure.

In the above control, an error is inevitably generated between the flow rate indicated by the controller and the actual flow rate of the air actually discharged by opening / closing control of the control valve based on the flow rate. There is a problem that control is difficult.

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

Means for Solving the Problems The present invention relates to an active suspension for controlling the injection and discharge of air to and from an air suspension by an air closed circuit including a high-pressure accumulator, a low-pressure accumulator, a control valve, an air compressor, and the like as described above. The change of the loading condition of the vehicle is judged from the signal of the suspension internal pressure sensor that detects the suspension internal pressure of the suspension, and the set pressures of the high-pressure accumulator and the low-pressure accumulator are changed per unit time of the air flowing through the control valve with respect to the change of the suspension internal pressure. A pressure environment control controller that variably controls the flow rate so that the flow rate always has a pressure that should be substantially constant is provided.

Function As described above, even if the load condition of the vehicle changes and the internal pressure of the suspension changes, the pressure relationship between the upstream side and the downstream side of the control valve is always kept almost constant, and the injection and discharge control of air to the air suspension is accurately controlled. And the active suspension performance can be improved.

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

In the figure, 1 is an air suspension, 2 is a high-pressure accumulator, 3 is a low-pressure accumulator, 4 is a flow control valve, and the flow control valve 4 is composed of a combination of an injection valve 41 and a discharge valve 42, and the injection valve 41 is opened. High pressure accumulator 2
Air is injected into the air suspension 1 from the
When the valve 42 is opened, the air in the air suspension 1 flows out into the low-pressure accumulator 3.

Reference numeral 5 denotes an air compressor, which normally sucks and compresses air in the low-pressure accumulator 3 and supplies it to the high-pressure accumulator 2, thereby keeping the internal pressure of the high-pressure accumulator 2 in a set pressure range sufficiently higher than the suspension internal pressure of the air suspension 1. The internal pressure of the low-pressure accumulator 3 is maintained in a set pressure range sufficiently lower than the internal pressure of the suspension of the air suspension 1.

Reference numeral 6 denotes a controller A for controlling the inflow and outflow of air from the air suspension. The controller A6 detects a suspension relative displacement sensor 7 for detecting the vertical displacement of the air suspension 1 above and below the spring, and detects the vertical acceleration on the spring. Based on the detection signals of the vertical acceleration sensor 8 and other various sensors for detecting various behaviors of the vehicle when it is running and when it is stopped, an instruction flow rate of air to be injected or discharged into the air suspension 1 is obtained by calculation. A control valve opening / closing command signal for operating the valve 41 or the discharge valve 42 is issued, and air is injected or discharged according to the indicated flow rate obtained by the above calculation.

In the above, the flow control valve 4 is composed of an injection valve 41 and a discharge valve 4.
Is composed of 2 both solenoid valves, which flows air by a pressure difference between the pressure (secondary pressure) P ₂ on the upstream side of the pressure (primary pressure) P ₁ and the downstream side in the respective open state, per unit time Is expressed by the following equation.

However, P ₁ : Primary pressure (Kgf / cm ² G) P ₂ : Secondary pressure (Kgf / cm ² G) A: Effective area (mm ² ) t: Temperature (° C) (P ₁ , Since P ₂ is a gauge pressure, the absolute pressure can be obtained by adding the standard atmospheric pressure 1.033 to the gauge pressure.) If the effective sectional area A of the injection valve 41 of the flow control valve 4 is 10 mm ²
Assume that the effective sectional area A of the discharge valve 42 is 20 mm ^2, and that t = 20 ° C., and the above equations (1) and (2) are shown in FIGS. 2 (a) and 2 (b). .

Note FIG. 2 (b), in (b), the injection flow rate Q ₁ and discharge flow rate Q ₂ are normal liters per minute (standard state i.e. 20 ° C. The volume of air flowing, 1 atm, relative humidity 65% It is expressed in N / min.

In the case of an active suspension in which air flows into and out of the air suspension 1 by the flow control valve 4 having the above-described flow characteristics, the loading conditions of the vehicle (that is, the number of passengers, the presence or absence of luggage, etc.) change, and the air suspension 1 suspension pressure changes etc., the primary pressure P ₁ and the flow rate per the pressure relationships change unit time and the secondary pressure P ₂ is changed, the indicated flow rate and injection or discharge based thereon the controller a is found in the arithmetic There is a problem that the error between the actual flow rate of the air and the active suspension performance is reduced.

Therefore, in the present invention, the pressure sensors 9 and 10 for detecting the internal pressures of the high-pressure accumulator 2 and the low-pressure accumulator 3, respectively.
In addition to the above, a suspension internal pressure sensor 11 for detecting the internal pressure of the air suspension 1 is provided, and switching valves 12 and 13 are provided in the suction passage and the discharge passage of the air compressor 5, respectively. Control signals for the switching valves 12 and 13 and the air compressor 5 are generated from the pressure signal by control logic as shown in FIG. 3, and the set pressures of the high-pressure and low-pressure accumulators 2 and 3 are changed according to the change in the internal pressure of the air suspension 1. A controller B14 for controlling pressure environment is provided.
The flow rate Q per unit time of the injection valve 41 and the discharge valve 42 is always substantially constant even if the internal pressure of the suspension is changed by the control by the control unit 14.

That is, when the suspension internal pressure is, for example, 4 kgf / cm ² G and the set pressure in the high-pressure accumulator 2 is 6 kgf / cm ² G in the standard loading state of the vehicle (so-called constant load state), the injection valve 41 is opened. the infusion rate to Q ₁ when a 680N / min as indicated by point a in FIG. 2 (b).

Here, for example, if the number of passengers increases and a so-called overload condition occurs and the internal pressure of the suspension becomes 5 kgf / cm ² G, and the pressure in the high-pressure accumulator 2 is 6 kgf / cm ² G, which is the same as that in the constant volume condition, injection is performed. about the flow rate Q ₁ as a 'point of FIG. 2 (b)
When the number of occupants is reduced to 500 N / min and the number of passengers is reduced, for example, and the inner pressure of the suspension becomes 3 kgf / cm ² G, the injection flow rate Q ₁ becomes as indicated by the point a ″ in FIG. About 750N
/ Min, and if the control valve opening / closing command signal of the controller A6 is set so that the constant volume state is issued as a standard, the actual flow rate of the actually injected air is smaller than the indicated flow rate in the overload state, In the stacking state, the injection is more than the indicated flow rate.

In the present invention, as shown in FIG. 3, the controller B14 first determines the vehicle loading conditions, for example, standard, overloaded or lightly loaded, based on the signal of the suspension internal pressure sensor 11, and if it is during injection, FIG. If it is time, the flow rate is the same as the flow rate of 680 N / min at the time of standard loading based on the characteristic map as shown in Fig. 2 (b).
Q ₁ and Q ₂ to determine the internal pressure of the high-pressure accumulator 2 and a low-pressure accumulator 3 to be obtained which was a set pressure of the high-pressure accumulator 2 and a low-pressure accumulator 3 in that state, the newly determined both set pressure and the pressure sensor 9
And the high pressure and low pressure accumulators 2 and 3 obtained from the signals of 10 and 10 are compared, and if overloaded, the switching valve 12 is turned on and the air compressor 5 is turned on.
2 is drawn by sucking the outside air through the compressor 15 and compressing the compressed air to supply the compressed air into the high-pressure accumulator 2 to increase the pressure in the high-pressure accumulator 2 to the newly determined set pressure, for example, 6.7 kgf / cm ² G. As shown in b) of b), the injection flow rate is 680 N / min which is the same as in the standard loading. On the other hand, since no forced air supply is performed in the low-pressure accumulator 3, a new set pressure (for example, 4.5 kgf in FIG.
/ cm ² G) lower than the standard loading condition (for example, 3.4
Kgf / cm ² G), but when the vehicle starts to move, the flow control valve 4 repeats opening and closing by the valve opening / closing command signal of the controller A6 based on the signals of the sensors such as the suspension relative displacement sensor 7, the vertical acceleration sensor 8, and the air. As the switching valve 12 is turned on and the air outlet of the low-pressure accumulator 3 remains closed, the air discharged from the air suspension 1 flows into the low-pressure accumulator 3 and the internal pressure is controlled. The pressure in the low-pressure accumulator 3 reaches a newly determined set pressure (for example, 4.5 kgf / cm ² G) within a relatively short time, the switching valve 12 is turned off, and the state shown in FIG. Then, normal pressure control is performed at the newly determined set pressure.

Switching valve 13 when changing from standard loading state to light loading state
Is turned on and the air compressor 5 is turned on, so that the air in the low-pressure accumulator 3 is sucked out by the air compressor 5 and is discharged from the switching valve 13 to the atmosphere via the muffler 16 to be released into the atmosphere. Set pressure at standard loading condition 3.4Kgf / cm ² G lighter loading condition 2.2
Kgf / cm ² G, and the air in the high-pressure accumulator 2 is injected into the air suspension 1 at the time of injection by the controller A6 to control the injection and discharge of air into the air suspension 1 after the vehicle starts moving as described above. When the pressure drops to a new set pressure (5.5 kgf / cm ² G), the switching valve 13 is turned off.

In the above, the high and low pressure accumulators 2,3
Air compressor 5 and switching valves 12, 1
Needless to say, a certain tolerance (for example, about 0.1 kgf / cm ² G) is given in consideration of the on / off frequency of 3, and in the above, the loading conditions are three stages: standard loading, overloading, and light loading. Although the case where the pressure control is performed separately has been described, the pressure control is actually performed by dividing the loading conditions into more detailed ones.

As described above, the flow rate of the flow control valve 4 per unit time is substantially constant (for example, 68
0N / min), an actual flow rate with an extremely small error with respect to the indicated flow rate can be obtained under any loading conditions, and the active suspension performance can be improved.

In the present invention, the specific structure for controlling the set pressures of the high-pressure and low-pressure accumulators 2 and 3 is not limited to the embodiment shown in FIG. 3 is provided with a switching valve of an air supply path for forcibly supplying air, and a high-pressure accumulator 2 is provided.
An air discharge path and a switching valve for forcibly discharging the air inside are added, and these switching valves are also controlled by the controller B14 in response to changes in the suspension internal pressure, and the internal pressures of the high-pressure and low-pressure accumulators 2 and 3 are adjusted. The change control may be forcibly performed to the newly determined set pressure.

Effects of the Invention As described above, according to the present invention, the pressure environment is maintained substantially constant even when the load condition of the vehicle changes and the suspension internal pressure changes, so that the flow rate per unit time of the flow control valve does not always change. By doing so, the error between the calculated flow rate and the actual flow rate that actually flows through the flow control valve can be made extremely small, and the active suspension performance can always be fully exhibited regardless of changes in loading conditions. Which can bring a great effect practically.

[Brief description of the drawings]

1 is a control system diagram showing one embodiment of the present invention, FIGS. 2A and 2B are flow characteristic diagrams of a flow control valve at the time of air injection and air discharge, and FIG. 3 is FIG. 4 is a flowchart illustrating an example of a control mode of a pressure environment control controller in FIG. 1 ... Air suspension, 2 ... High pressure accumulator, 3 ... Low pressure accumulator, 4 ... Flow control valve, 5
... air compressor, 6 ... air in / out controller, 7 ... suspension relative displacement sensor, 8 ... vertical acceleration sensor, 9, 10 ... pressure sensor, 11 ... suspension internal pressure sensor, 12, 13 ... switching Valve, 14 …… Controller for pressure environment control.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-96113 (JP, A) JP-A-60-152506 (JP, U) JP-A-60-119634 (JP, U)

Claims (1)

(57) [Claims] An air suspension capable of taking in and out of air, a high-pressure accumulator, a low-pressure accumulator, an air compressor for sucking and compressing air in the low-pressure accumulator and supplying the compressed air to the high-pressure accumulator, and an air compressor from the high-pressure accumulator to the air suspension. The above-mentioned flow control valve of the closed circuit for air, which is composed of a flow control valve for controlling air injection and air discharge from the air suspension to the low-pressure accumulator, is supplied to the air suspension based on signals from sensors for detecting various behaviors of the vehicle. In an active suspension controlled by the opening / closing command signal of an air in / out controller for issuing an opening / closing command signal for the flow control valve based on the command flow, the suspension internal pressure of the air suspension is determined. Suspension to detect The load condition of the vehicle is determined based on the signal of the pressure sensor, and the set pressures of the high-pressure accumulator and the low-pressure accumulator are adjusted so that the flow rate of the air flowing through the flow rate control valve per unit time with respect to the change in the internal pressure of the suspension is always substantially constant. A control device for an active suspension, comprising a pressure environment controller for variably controlling a pressure so as to have a desired pressure relationship.