JP3010955B2 - Air suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air suspension for a vehicle such as an automobile, and more particularly to an air suspension control device.

[0002]

2. Description of the Related Art Generally, an air suspension of a vehicle such as an automobile has an air spring provided for each wheel, and the volume of the air chamber of each air spring decreases and increases when the wheel bounces and rebounds. The spring force is increased or decreased by the increase or decrease of the pressure in the air chamber accompanying this.

As one of such air suspension control devices, for example, Japanese Patent Application No. 4-184428 filed by the same applicant as the present applicant discloses an air spring provided for each wheel. An air suspension control device for controlling a posture of a vehicle body by controlling supply and discharge of a working gas to and from a chamber, comprising: running state detecting means for detecting a running state of the vehicle; and an air chamber based on the detected running state of the vehicle. Target gas mass calculating means for calculating the target gas mass Mo in the air chamber, real gas mass calculating means for calculating the real gas mass M in the air chamber, and a target gas mass Mo based on a deviation Mc between the real gas mass M and the target gas mass Mo. Supply and discharge control means for controlling the supply and discharge of the working gas to and from the air chamber so that the deviation is reduced, and the mass of the gas in the air chamber of each air spring is Air suspension control system which is adapted to be fed back control has already been proposed.

[0004] According to the air suspension control device according to the prior proposal, the vehicle body during acceleration / deceleration or turning of the vehicle is compared with a normal air suspension in which the pressure in the air chamber is not actively controlled. This can not only improve the steering stability of the vehicle, but also increase the target gas mass Mo even if the wheels bounce or rebound due to uneven road surfaces.
Is not changed, and the deviation Mc does not change. Therefore, the supply and discharge of the working gas to and from the air chamber are not performed repeatedly and frequently. Therefore, the working gas is supplied to the air chamber by feedback control of the pressure in the air chamber. Energy consumption and cost can be reduced and durability of the air suspension can be improved as compared with the case where the air suspension is exhausted.

[0005]

However, the above-mentioned Japanese Patent Application No. Hei.
In the embodiment of the air suspension control device described in the specification and the drawings, the target gas mass Mo in the air chamber is determined by the reference volume of the air chamber and the target variable volume of the air chamber based on the running state of the vehicle. The target volume of the air chamber calculated as the sum of the target volume of the air chamber calculated as the sum of the reference pressure in the air chamber and the target fluctuating pressure in the air chamber based on the running state of the vehicle; It is calculated according to the gas equation based on the temperature of the working gas in the chamber, and the reference pressure in the air chamber is set as the pressure in the air chamber when the vehicle is stopped and the vehicle height is at the standard vehicle height, During running of the vehicle, the constant value is maintained.

Therefore, when a change in the actual weight of the vehicle due to the consumption of gasoline or the like during the running process of the vehicle or a change in the apparent weight of the vehicle due to the influence of aerodynamics due to the running of the vehicle occurs, the vehicle moves straight ahead at a constant speed. Even when the vehicle is running and no inertial force acts on the vehicle body, the pressure in the air chamber when the vehicle height is the standard vehicle height is the same as the pressure in the air chamber detected when the vehicle is stopped. Therefore, the reference volume of the air chamber also differs from the value when the vehicle is at a standstill.As a result, the vehicle height during traveling of the vehicle deviates from the intended vehicle height, There is a problem that the attitude may deviate from the attitude when the vehicle stops.

The present invention has been made in view of the above-mentioned problems in the air suspension control device according to the above-mentioned proposal, and
In addition to reducing the energy consumption and cost and improving the durability of the air suspension as compared with the case where the pressure in the air chamber is feedback-controlled,
It is an object of the present invention to provide an improved air suspension control device capable of accurately controlling the vehicle height to a target vehicle height and appropriately controlling the posture of the vehicle body even if the weight of the vehicle changes while the vehicle is running. I have.

[0008]

According to the present invention, there is provided, as shown in FIG. 1, an air spring (2) provided for each wheel and having an air chamber therein. A traveling state detecting means for detecting a traveling state of the vehicle; a target gas mass computing means for computing a target gas mass in the air chamber based on the detected traveling state of the vehicle; An actual gas mass calculating means (8) for calculating an actual gas mass M in the chamber; and an operating gas for the air chamber so as to reduce the deviation based on a deviation Mc between the actual gas mass M and the target gas mass Mo. In an air suspension control device having supply / discharge control means (10) for controlling a posture of a vehicle body by controlling supply / discharge, the target gas mass calculating means (6) includes a reference volume of the air chamber and a reference volume of the air chamber. Target volume calculating means (12) for calculating a target volume of the air chamber as a sum of a target variable volume of the air chamber based on a running state of the vehicle detected by the running state detecting means; and a reference pressure in the air chamber. Target pressure calculating means (14) for calculating a target pressure in the air chamber as a sum of a target pressure in the air chamber based on a running state of the vehicle detected by the running state detecting means; Temperature detecting means (16) for detecting the temperature of the working gas in the chamber, and calculating means (18) for calculating the target gas mass based on the target volume and the target pressure and the temperature detected by the temperature detecting means. And the target pressure calculating means (14) calculates the target fluctuating pressure.
0) and reference pressure detecting means (21) for detecting the pressure in the air chamber when the vehicle is stopped as a reference pressure.
A vehicle height detecting means (22) for detecting an actual vehicle height of a portion corresponding to each wheel; and a vehicle height signal smoothing means (23) for smoothing a signal indicating the actual vehicle height detected by the vehicle height detecting means. Target vehicle height calculating means (24) for calculating a target vehicle height of a portion corresponding to each wheel based on the running state of the vehicle detected by the running state detecting means; an actual vehicle height after the smoothing process and the target Vehicle height deviation calculating means (25) for calculating a deviation from the vehicle height, and integrating means (26) for integrating the vehicle height deviation when the sign of the vehicle height deviation between the left and right wheels is the same.
And a reference pressure correcting means (27) for correcting the reference pressure based on the integration result.

[0009]

According to this configuration, the target volume calculating means (1)
According to 2), the target volume of the air chamber is calculated as the sum of the reference volume of the air chamber and the target variable volume of the air chamber based on the running state of the vehicle, and the target pressure calculating means (14)
The target pressure in the air chamber is calculated as the sum of the reference pressure in the air chamber and the target fluctuating pressure in the air chamber based on the running state of the vehicle detected by the running state detecting means. The temperature of the working gas in the air chamber is detected, and the calculating means (18) calculates the target gas mass Mo based on the target volume and the target pressure and the temperature detected by the temperature detecting means.

The target variable pressure calculating means (20) calculates a target variable pressure in the air chamber based on the running state of the vehicle detected by the running state detecting means 4, and the reference pressure detecting means (21) stops the vehicle. The pressure in the air chamber at that time is detected as a reference pressure, the actual vehicle height of a portion corresponding to each wheel is detected by the vehicle height detecting means (22), and the actual vehicle height is indicated by the vehicle height signal smoothing processing means (23). The signal is smoothed, and the target vehicle height calculating means (24)
The vehicle height deviation calculating means (25) calculates the deviation between the actual vehicle height after smoothing processing and the target vehicle height based on the traveling state of the vehicle, and calculates the deviation between the actual vehicle height and the target vehicle height after the smoothing process. When the sign of the vehicle height deviation is the same, the integration means (2
The vehicle height deviation is integrated by 6), and the reference pressure correction means (2)
According to 7), the reference pressure is corrected based on the integration result by the integration means.

Therefore, the reference pressure in the air chamber is corrected based on the integral value of the deviation between the actual vehicle height and the target vehicle height, so that the change in the actual weight of the vehicle due to the consumption of gasoline or the like in the running process of the vehicle or the like. The apparent weight of the vehicle changes due to the effect of aerodynamics due to the running of the vehicle, etc., and the pressure in the air chamber when the vehicle height is the standard vehicle height despite the inertia force not acting on the vehicle body increases the vehicle pressure. Even if the pressure in the air chamber is different from the detected pressure in the stopped state, the reference pressure in the air chamber is corrected to the pressure in the air chamber at that time, whereby the reference volume of the air chamber is reduced. Due to the difference in the reference volume when the vehicle is in a stopped state, the vehicle height during running of the vehicle deviates from the original height, or the body posture is lower than the vehicle's posture when stopped. It can shift It is indeed prevented.

Further, according to the above configuration, the deviation between the actual vehicle height after smoothing processing and the target vehicle height is the same when the sign of the vehicle height deviation between the left and right wheels is the same, that is, when the direction of the vehicle height deviation is both right and left wheels. Therefore, the reference pressure in the air chamber can be appropriately corrected as compared with the case where the deviation between the actual vehicle height after the smoothing process and the target vehicle height is constantly integrated. It is possible to reliably prevent the spring constants of the left and right air springs from being set to different values.

[0013]

Supplementary description of the means for solving the problems In the air suspension control device, the pressure in the air chamber of the air spring, the volume of the air chamber, the temperature of the gas in the air chamber, and the mass of the gas in the air chamber are respectively described. P,
Let V, T, and M be the standard conditions, ie, the pressure in the air chamber when the wheel is in the neutral position, the volume of the air chamber, the temperature of the gas in the air chamber, and the mass of the gas in the air chamber (target gas mass). To P ₁ , V ₁ , T ₁ , M ₁
The pressure in the air chamber, the volume of the air chamber, the temperature of the gas in the air chamber, and the mass of the gas in the air chamber after the wheel receives an external force due to, for example, overcoming a protrusion on the road surface are represented by P ₂ and V ₂ respectively. , T ₂ , M ₂ , the gas is regarded as a complete gas, and R is defined as the gas constant of the gas, and the mass M of the gas calculated in the air suspension controller is defined as the following equation 1.

## EQU1 ## M = (PV) / (RT)

Assuming now that the vehicle is traveling straight, and assuming that the mass of gas in the air chamber is constant,
The target mass M ₁ calculated by the air suspension control device is represented by the following equation (2).

## EQU2 ## M ₁ = (P ₁ · V ₁ ) / (R · T ₁ )

Assuming that the state change occurring in the air spring is a polytropic change and the system of the air chamber is closed, n is a polytropic index and the following equation B
Holds.

## EQU3 ## P ₁ · V ₁ ⁿ = P ₂ · V ₂ ⁿ

From Equation 3, the pressure P ₂ in the air chamber after the air suspension receives an external force is expressed by Equation 4 below.

## EQU4 ## P ₂ = (V ₁ / V ₂ ) ⁿ · P ₁

The volume V ₂ in the air chamber after the external force is applied to the air suspension is represented by S as the suspension stroke (positive displacement in the bound direction from the standard position), and A as the cross-sectional area of the piston of the air suspension. Is represented by the following Expression 5.

## EQU5 ## V ₂ = V ₁ -AS

The pressure P ₂ and the volume V ₂ represented by the equations 4 and 5 are values detected by the pressure detecting means and the volume detecting means, respectively. Is represented by Equation 6 below.

M = (P ₂ · V ₂ ) / (R · T ₂ ) = {(P ₁ · V ₁ ) / (R · T ₂ )} · {V ₁ / (V ₁ −A · S) ｝ ^N-1

Here, the temperature T is smoothed so that the change in the temperature T of the gas in the air chamber detected by the temperature detecting means is sufficiently slower than the change in the volume of the air chamber, and the polytropic index of the temperature change is substantially reduced. , The following equation 7 holds.

## EQU7 ## T ₂ = T ₁

Therefore, equation (6) is represented as equation (8) below.

M = {(P ₁ · V ₁ ) / (R · T ₁ )} · {V ₁ / (V ₁ − (V ₁ AS)} ⁿ⁻¹

Now, the feedback control amount E in the air suspension control device is defined as in the following equation (9).
In the following equation 9, K is a feedback gain.
E <0 corresponds to exhaust for discharging gas from the air chamber, and E> 0 corresponds to air supply for supplying gas to the air chamber.

E = K · (M ₁ −M)

When Equations 2 and 8 are substituted into Equation 9, Equation 9 is expressed as Equation 10 below.

E = K · {(P ₁ · V ₁ ) / (R · T ₁ )} · [1- {V ₁ / (V ₁ − (V ₁ A · S)} ⁿ⁻¹ ]

Assuming that the wheel makes a stroke in the bounding direction by S as it passes through a convex portion of the road surface, V ₁ -A
· S because it is <V _1, the number 11 below is satisfied.

V ₁ / (V ₁ -AS)> 1

When the wheel bounces, the pressure P in the air chamber increases (ie, it is not a constant pressure change), so that the polytropic index n is 1 or more.
Holds.

1− {V ₁ / (V ₁ −A · S)} ⁿ⁻¹ <0

When considering Equation 10 based on Equation 12, the following Equation 13 is established.

E <0

Equation 13 means exhaust as described above, and means that when the wheel receives an input in the bounding direction from the road surface, the gas is exhausted from the air chamber and the spring force of the air spring is reduced.

If it is assumed that the wheel passes through the concave portion of the road surface and makes a stroke of S in the rebound direction,
_{Since 1−} A · S> V ₁ , the following Expression 14 is established.

V ₁ / (V ₁ −A · S) <1

When the wheel rebounds, the pressure P in the air chamber decreases (ie, it is not a constant pressure change).
The polytropic index n is greater than or equal to 1 and therefore:
5 holds.

1− {V ₁ / (V ₁ −A · S)} ⁿ⁻¹ > 0

When Equation 10 is examined based on Equation 15, the following Equation 16 is established.

E> 0

Equation 16 means air supply as described above, and means that when the wheel receives an input in the rebound direction, gas is supplied to the air chamber to increase the spring force of the air spring.

According to one embodiment of the present invention, the actual gas mass calculating means includes a volume detecting means for detecting a volume of the air chamber, a pressure detecting means for detecting a pressure in the air chamber, and an operation in the air chamber. Temperature detection means for detecting the temperature of the gas, temperature signal smoothing processing means for smoothing a signal indicating the temperature of the working gas detected by the temperature detection means,
A calculating means for calculating an actual gas mass based on the volume and the pressure detected by the volume detecting means and the pressure detecting means, respectively, and the temperature smoothed by the smoothing processing means.

According to this configuration, the volume of the air chamber detected by the volume detecting means, the air chamber pressure detected by the pressure detecting means, and the air chamber detected by the temperature detecting means and smoothed by the smoothing processing means The actual gas mass is calculated by the calculating means on the basis of the temperature of the working gas in the vehicle, and when the wheel receives a force in the bounding direction such as when the wheel passes through a convex portion of the road surface as described above, the spring force of the air spring is used. When the wheel is subjected to a rebound direction force such as when the wheel passes through a concave portion of the road surface, the spring force of the air spring is increased, whereby the supply and discharge of the working gas to and from the air chamber are not performed. The ride comfort of the vehicle is improved as compared with a normal air suspension.

[0033]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing one embodiment of the air suspension control device according to the present invention. FIG. 2
In the above, * is a symbol corresponding to each wheel, and members denoted by reference numerals with * are front right wheels (* = fr) and front left wheels (*
= Fl), the right rear wheel (* = rr), and the left rear wheel (* = rl).

In FIG. 2, reference numeral 30 * denotes a shock absorber disposed between an unsprung portion and an unsprung portion, not shown, and 32 * is formed integrally with the shock absorber 30 *. FIG. The air spring 32 * has an air chamber 34 * whose volume decreases and increases as the wheel bounces and rebounds, which are not shown, as is well known.

One end of an air supply conduit 36 * is connected to the air chamber 34 *, and the other end of the conduit is connected to a high-pressure tank 38 for storing high-pressure air therein. An air supply control valve 40 *, which is a solenoid-type normally closed on-off valve, is provided in the middle of the air supply conduit 36 *. Air supply conduit 36
One end of an exhaust conduit 42 * is connected to a portion between the * air spring 30 * and the air supply control valve 40 *, and the other end of the conduit is connected to a low-pressure tank 4 for storing low-pressure air therein.
4 are connected. An exhaust control valve 46 *, which is a solenoid-type normally-closed open / close valve, is provided in the exhaust conduit 42 * in the same manner as the control valve 40 *.

As shown in FIG. 2, in the illustrated embodiment, the control valves 40 * and 46 * include a steering angular speed sensor 48 for detecting the steering angular speed θd, a vehicle speed sensor 50 for detecting the vehicle speed V, and a vehicle body. A lateral acceleration sensor 52 for detecting the lateral acceleration Gy of the vehicle, a longitudinal acceleration sensor 54 for detecting the longitudinal acceleration Gx of the vehicle body, and a vehicle height sensor 56 for detecting the vehicle height H * (deviation from the reference vehicle height) of a portion corresponding to each wheel. *, Electronic control based on signals from a pressure sensor 58 * for detecting the pressure P * in the air chamber 34 of each air spring and a temperature sensor 60 * for detecting the temperature T * of air in each air chamber, as described later. The device 62 is controlled to be opened and closed.

The electronic control unit 62 has a microcomputer 64 as shown in FIG. The microcomputer 64 may have a general configuration as shown in FIG. 3 and includes a central processing unit (CPU) 6.
6, a read only memory (ROM) 68, a random access memory (RAM) 70, and an input port device 72
And an output port device 74, which are connected to each other by a bidirectional common bus 76.

The input port device 72 has a signal indicating the steering angular velocity θd detected by the steering angular velocity sensor 48, a signal indicating the vehicle speed V detected by the vehicle speed sensor 50, and the lateral acceleration Gy of the vehicle body detected by the lateral acceleration sensor 52. And a signal indicating the longitudinal acceleration Gx of the vehicle body detected by the longitudinal acceleration sensor 54, and a vehicle height sensor provided corresponding to each wheel not shown in the figure. 56 *, pressure sensor 58 *, temperature sensor 6
From 0 *, a signal indicating the vehicle height H * of the portion corresponding to each wheel, the pressure P * in each air chamber, and the temperature T * of the air in each air chamber is input.

The input port device 72 appropriately processes the signal inputted thereto, and in accordance with the instruction of the CPU 66 based on the program stored in the ROM 68, the CPU and the RAM.
70, and outputs the processed signal. R
The OM 38 stores the control programs shown in FIGS. 4 to 7 and maps corresponding to the graphs shown in FIGS. The CPU 66 performs various calculations and signal processing based on the control programs shown in FIGS. 4 to 7 as described later. The output port device 74 is a CPU
According to the instruction of 66, a control signal is output to the air supply control valve 40 corresponding to each air spring via the drive circuit 78 *,
The drive circuit 80 * outputs a control signal to the exhaust control valve 46 * corresponding to each air spring.

Next, the control of the air suspension in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The routine shown in FIG. 4 is started by closing an ignition switch (not shown). In the flowcharts shown in FIGS. 4 to 7, * is a symbol corresponding to each wheel, and the control by the routine shown in FIG. 4 is performed by, for example, the right front wheel (* = fr) and the left front wheel (* = fl), right rear wheel (* = rr), and left rear wheel (* = rl) in this order.

First, in step 50, the reference pressure SP * in the air chamber is calculated in accordance with the flowchart shown in FIG. 5, as will be described later. In step 100, as shown in FIG. The target air mass Mo * in the air chamber is calculated according to the flow chart, and in step 200, the actual air mass M * in each air chamber is calculated according to the flow chart shown in FIG. In the above, the mass deviation Mc * (= Mo *-) calculated in steps 100 and 200 is used.
M *) is calculated.

In step 400, it is determined whether or not the deviation Mc * is greater than or equal to -α and less than or equal to α using α (positive constant) as a control threshold value. When it is determined that α is satisfied, the flow returns to step 100 after the air supply control valve 40 * and the exhaust control valve 46 * are closed in step 800, and -α ≦ Mc * ≦ α is not satisfied. When the determination is made, the process proceeds to step 500.

In step 500, it is determined whether or not the deviation Mc * is equal to or more than α. If it is determined that α ≦ Mc * is not satisfied, in step 600, the air supply control valve is determined. After the valve 40 * is opened and the exhaust control valve 46 * is closed, the process returns to step 100. When it is determined that α ≦ Mc *, the air supply control valve 40 * is closed. After the exhaust control valve 46 * is opened, the process returns to step 100.

Next, a routine for calculating the reference pressure SP * in the air chamber performed in step 50 of the flowchart shown in FIG. 4 will be described with reference to the flowchart shown in FIG.

First, in step 52, the steering angular velocity θd
, Vehicle speed V, body lateral acceleration Gy, body longitudinal acceleration Gx
The vehicle height H * of the portion corresponding to each wheel, the pressure P * in the air chamber 34 * of each air spring, and the temperature T * of the air in each air chamber are read. In step 54, it is determined whether or not the vehicle speed V is substantially 0, that is, whether or not the vehicle is in a stopped state. If it is determined that V is not 0, step 66 is performed. Proceed to V = 0
When it is determined that the above is true, the process proceeds to step 56.

In step 56, a later-described step 80 will be described.
The front-wheel-side stroke correction amount Ef and the rear-wheel-side stroke correction amount Er calculated in step (1) are reset to 0, respectively. In step 58, the count value C of the timer is incremented by one, and in step 60, Is the count value C
Is greater than or equal to a reference value Cr (a positive constant integer). When it is determined that C> Cr is not satisfied, the process proceeds directly to step 100, and when it is determined that C> Cr, the count value C is reset to 0 in step 62, and in step 64. The reference pressure Sp * is the pressure P detected by the pressure sensor 58 *.
Is set to *, and then the process proceeds to step 100.

In step 66, a delay compensation value (estimated lateral jerk) G of the lateral acceleration of the vehicle body based on the steering angular velocity θd and the vehicle speed V and based on a map corresponding to the graph shown in FIG.
yo is calculated, and in step 68, the lateral acceleration G of the vehicle body is calculated.
estimated lateral acceleration G of the vehicle body based on y and its delay compensation value Gyo
ym (= Gy + Gyo) is calculated. When the steering angular velocity θd is a negative value, the delay compensation value Gyo is calculated as a negative value.

In step 70, the target roll amount Rm of the vehicle body is calculated based on the estimated lateral acceleration Gym of the vehicle based on a map corresponding to the graph shown in FIG. 9, and in step 72, the longitudinal acceleration of the vehicle body is calculated. Based on Gx, a target pitch amount Pm of the vehicle body is calculated based on a map corresponding to the graph shown in FIG. In step 74, steps 70 and 7
Based on the target roll amount Rm and the target pitch amount Pm calculated in step 2, the target stroke amount S * of each wheel is calculated according to the following equation 17 using Kp and Kr as positive constants. When the vehicle height is controlled according to the vehicle speed V or the like, the heave amount h corresponding to the vehicle speed V or the like may be added in each of the following equations (17).

Sfl = -Kp-Pm-Kr-Rm Sfl = -Kp-Pm-Kr-Rm Srl = -Kp-Pm + Kr-Rm

In step 76, the cutoff frequency is set to, for example, 0.1 Hz, and the signal indicating the vehicle height H * of the portion corresponding to each wheel is subjected to low-pass filter processing, whereby the vehicle height Hlp after low-pass filter processing is performed. * Is calculated, and in step 78, the vehicle is calculated as the deviation between the target stroke amount S * of each wheel calculated in step 74 and the vehicle height Hlp * after the low-pass filter processing calculated in step 76. The high deviation E * is calculated according to the following equation (18).

E * = S * -Hlp *

At step 80, the vehicle height deviation E of the right front wheel is determined.
It is determined whether or not the signs of fr and the vehicle height deviation Efl of the left front wheel are the same, and when these signs are the same, the front wheel side stroke correction amount Ef is integrated according to the following Expression 19, and It is determined whether the signs of the vehicle height deviations Err and Erl of the left and right rear wheels are the same, and when these signs are the same, the stroke correction amount Er on the rear wheel side is integrated according to the following equation (20). You.

Ef = Ef + (Efr + Efl) / 2

[Equation 20] Er = Er + (Err + Erl) / 2

In step 82, Kdjf and Kdkjr are positive constants, and the correction amount Adjf of the pressure in the air chamber of the front wheel air spring and the air chamber of the rear wheel air spring are calculated according to the following formulas 21 and 22, respectively. A correction amount Adjr of the internal pressure is calculated.

[Equation 21] Adjf = Kdjf · Ef

Adjr = Kdjr · Er

In step 84, the reference pressure SP * in the air chamber 34 * of each air spring is corrected according to the following equation (23).

## EQU23 ## SPfr = SPfr + Adjf SPfl = SPfl + Adjf SPrr = SPrr + Adjr SPrl = SPrl + Adjr

Thus, in steps 52 to 84, when the vehicle is stopped, the reference pressure SP * in the air chamber 34 * of each air spring is determined by the pressure P in each air chamber detected by the pressure sensor 58 *. When the vehicle is in a running state, the target stroke S * of each wheel is calculated based on the running state of the vehicle, and the vehicle height after low-pass filtering, that is, the vehicle height Hlp * after smoothing, is calculated. The vehicle height deviation E * is calculated according to the equation (18). When the sign of the vehicle height deviation E * of the left and right wheels is the same, the strokes on the front wheel side and the rear wheel side are calculated based on the vehicle height deviation E * according to the equations (19) and (20). The correction amounts Ef and Er are calculated, and the front wheel side and rear wheel side pressure correction amounts Adjf and Adjr are calculated based on the stroke correction amounts Ef and Er according to the numbers 21 and 22, and these pressure corrections are calculated. Reference pressure SP * is corrected according to based number 23.

Next, the routine for calculating the target air mass Mo * performed in step 100 of the flowchart shown in FIG. 4 will be described with reference to the flowchart shown in FIG.

First, in step 135, the SV * is set to the reference volume of the air chamber 34 * of the air spring 32 * of each wheel (the volume when the corresponding wheel is at the neutral position and the vehicle height H * is the standard vehicle height). ), And the target air chamber volume Vo * of each air spring is calculated according to the following equation 24, where S * is the target stroke of each wheel calculated in step 74 of FIG. In Equation 24, A ₁ and A ₂ are the shock absorbers 30 for the left and right front wheels and the left and right rear wheels, respectively.
Is the cross-sectional area of the cylinder.

[Equation 24] Vofr = SVfr + A ₁ · Sfr Vofl = SVfl + A ₁ · Sfl Vorr = SVrr + A ₂ · Srr Voll = SVrl + A ₂ · Srl

In step 140, step 6 in FIG.
8, based on the estimated lateral acceleration Gym of the vehicle body calculated in
f and Dr are positive constants on the front wheel side and the rear wheel side, respectively.
y * is calculated.

## EQU25 ## Pyfr = Df.Gym Pyfl = -Pyfr Pyrr = Df.Gym Pyrl = -Pyrr

In step 145, based on the longitudinal acceleration Gx of the vehicle body read in step 52, the increase Px * of the pressure in each air chamber is calculated in accordance with the following equation 26, using Dp as a positive constant.

[Equation 26] Pxfr = Dp · Gx Pxfl = Pxfr Pxrr = −Dp · Gx Pxrl = Pxrr

In step 150, the target air chamber pressure Po * is calculated according to the following equation 27, using SP * as the reference pressure of each air chamber pressure calculated in step 64 or 84.

## EQU27 ## Pofl = SPfr + Pyfr + Pxfr Pofr = SPfl + Pyfl + Pxfl Porr = SPrr + Pyrr + Pxrr Porl = SPrl + Pyrl + Pxfl

In step 155, the air temperature T * in each air chamber read in step 52, and the target air chamber volume Vo calculated in step 135
*, Based on the target air chamber pressure Po * calculated in step 150, where R is a gas constant and
, The target air mass Mo * in each air chamber is calculated.

## EQU28 ## Mo * = (Po * Vo *) / (RT *)

Next, the routine for calculating the actual air mass M * performed in step 200 of the flowchart shown in FIG. 4 will be described with reference to the flowchart shown in FIG.

First, at step 220, the cutoff frequency is set to, for example, 0.01 Hz, and the signal indicating the temperature T * is subjected to low-pass filtering to calculate the temperature Tlp * after low-pass filtering.

In step 230, based on the vehicle height H * of the part corresponding to each wheel read in step 52,
K ₁ and the coefficient of K ₂ About each of the left and right front wheels and left and right rear wheels volume (positive constant) as an air chamber of each wheel V
* Is calculated according to the following equation 29.

[Number 29] _{Vfr = SVfr + K 1 · Hfr} Vfl = SVfl + K 1 · Hfl Vrr = SVrr + K 2 · Hrr Vrl = SVrl + K 2 · Hrl

In step 240, the pressure P * in the air chamber of each wheel read in step 52, the temperature Tlp * in each air chamber after the low-pass filter processing calculated in step 220, step 230 Based on each of the air chamber volumes V * calculated in the above, the actual air mass M in each of the air chambers is calculated according to the following equation 30, where R is a gas constant.
* Is calculated.

[Mathematical formula-see original document] M * = (P * .V *) / (R.Tlp *)

Thus, according to the illustrated embodiment, the reference pressure SP * in each air chamber is calculated in step 50, ie, steps 52 to 84, and the vehicle travels in step 100, ie, steps 135 to 155. The target air mass Mo in each air chamber according to the state, that is, turning or acceleration / deceleration
* Is calculated, and step 200, that is, steps 220 to
At 240, the actual air mass M * in each air chamber is calculated, and at step 300, the deviation Mc * between the target air mass Mo * and the actual air mass M * is calculated, and at step 400
The feedback control of the mass of the air in each air chamber is performed so that the deviation Mc * is equal to or more than -α and equal to or less than α in the range from 800 to 800.

Therefore, when the vehicle is not substantially turned or accelerated or decelerated, as in the case of a vehicle traveling at a constant speed, the target air mass Mo is obtained even if the wheels bounce or rebound due to unevenness of the road surface.
* Does not change and the deviation Mc * does not change.
* And 46 * are reliably prevented from being repeatedly opened and closed.

At the time of turning or acceleration / deceleration of the vehicle, the target air mass Mo * is calculated so as to suppress a change in the posture of the vehicle due to the lateral acceleration and the longitudinal acceleration of the vehicle, and the target air mass Mo * and the actual air mass M The deviation Mc * from * is -α or more and α
The control valves 40 * and 46 * are opened and closed as follows, and air is supplied to and exhausted from each air chamber, so that a roll, nose dive, squat, etc. A large posture change is effectively prevented.

According to the illustrated embodiment, when the vehicle is at a standstill, the reference pressure S in each air chamber 34 * is set.
P * is set to the pressure P * in each air chamber detected by the pressure sensor 58 *. When the vehicle is in a running state, the vehicle height Hlp * and the target stroke S * after smoothing processing are set.
And the front-wheel and rear-wheel stroke correction amounts Ef and Er are calculated based on the deviation E *, and the front-wheel and rear-wheel pressure correction amounts Adjf based on the stroke correction amounts Ef and Er. And Adjr are calculated, and the reference pressure SP * is corrected based on these pressure correction amounts.

Therefore, for example, when the vehicle is driven for a long time without stopping and a large amount of gasoline is consumed, the actual weight of the vehicle is changed. The apparent weight of the vehicle changes, and the pressure in the air chamber when the vehicle height is the standard vehicle height despite the inertia force not acting on the vehicle body is the same as the pressure in the air chamber when the vehicle is stopped. Even if the value is different, the reference pressure in the air chamber is properly corrected according to the change in the weight of the vehicle. Is reliably prevented from deviating from the attitude of the vehicle when the vehicle is stopped.

Further, according to the illustrated embodiment, the stroke correction amounts Ef and Er on the front wheel side and the rear wheel side are only obtained when the sign of the vehicle height deviation E * between the right and left wheels is the same, that is, the deviation of the vehicle height. Only when the direction is the same between the left and right wheels, the calculation is performed by integrating the vehicle height deviation E * of the left and right wheels. The reference pressure SP * in the air chamber is appropriately corrected, and the spring constants of the left and right air springs are reliably prevented from being set to different values.

Further, according to the illustrated embodiment, the signal indicating the temperature T * of the air in each air chamber is low-pass filtered to smooth the signal indicating the temperature T *. *, The actual air mass M * in each air chamber is calculated. Therefore, as described above according to the equations (1) to (16), when the wheel receives a force in the bounding direction, the air spring is actuated. When the spring force is reduced and the wheel receives a force in the rebound direction, the spring force of the air spring is increased. Therefore, the actual air mass M * in each air chamber is calculated based on the detected temperature T *. The riding comfort of the vehicle is improved as compared with the case where the driving is performed.

In the above-described embodiment, the vehicle height Hlp * and the temperature Tlp * after the smoothing process are respectively a signal indicating the vehicle height H * and a signal indicating the temperature T * of the air in each air chamber. The smoothing process for the signal indicating the vehicle height H * and the signal indicating the temperature T * is not performed by digital calculation as in the illustrated embodiment, but is performed electronically. The control may be executed in an analog manner by a low-pass filter incorporated in the control device, and FIG. 8 of Japanese Patent Application No. 4-184428 described above.
May be executed by the calculation of the weighted average shown in FIG.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments may be made within the scope of the present invention. The possibilities will be clear to the skilled person.

[0074]

As is apparent from the above description, according to the present invention, even if the wheels bounce or rebound due to the unevenness of the road surface, the target gas mass Mo is not changed and the deviation Mc
Does not change, the supply and discharge of the working gas to and from the air chamber are not performed repeatedly and frequently.Therefore, the pressure in the air chamber is feedback-controlled and the consumption of the working gas to and from the air chamber is reduced. In addition to reducing energy and cost and improving the durability of the air suspension, the reference pressure in the air chamber is corrected based on the integrated value of the deviation between the actual vehicle height and the target vehicle height. Changes in the actual weight of the vehicle due to the consumption of gasoline, etc., and changes in the apparent weight of the vehicle due to the effects of aerodynamics due to the running of the vehicle. Even if the pressure in the air chamber when the height is the standard vehicle height is different from the pressure in the air chamber detected when the vehicle is stopped, The reference pressure is corrected to the pressure in the air chamber at that time, so that the reference volume of the air chamber becomes different from the reference volume when the vehicle is at a standstill, so that the reference volume during the running of the vehicle is changed. It is possible to reliably prevent the vehicle height to be deviated from the original vehicle height and the vehicle body from deviating from the posture when the vehicle is stopped.

According to the present invention, the deviation between the actual vehicle height after smoothing processing and the target vehicle height is the same when the sign of the vehicle height deviation between the left and right wheels is the same, that is, when the direction of the vehicle height deviation is between the left and right wheels. Therefore, the reference pressure in the air chamber can be appropriately corrected as compared with the case where the deviation between the actual vehicle height after smoothing processing and the target vehicle height is constantly integrated. Thus, it is possible to reliably prevent the spring constants of the left and right air springs from being set to different values.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an air suspension control device according to the present invention, corresponding to the description in the claims.

FIG. 2 is a schematic configuration diagram showing one embodiment of an air suspension control device according to the present invention.

FIG. 3 is a block diagram showing one embodiment of the electronic control device shown in FIG. 3;

FIG. 4 is a flowchart showing a main routine of control of an air suspension achieved by the electronic control device shown in FIGS. 2 and 3;

FIG. 5 is a step 50 of the flowchart shown in FIG. 4;
Fig. 6 is a flowchart showing a routine for calculating a reference pressure in the air chamber performed in Fig. 4;

FIG. 6: Step 10 of the flowchart shown in FIG.
5 is a flowchart showing a target gas mass calculation routine performed at 0.

FIG. 7: Step 20 of the flowchart shown in FIG.
9 is a flowchart showing a routine for calculating the actual air mass performed at 0.

FIG. 8 is a graph showing a relationship among a vehicle speed V, a steering angular velocity θd, and a delay compensation value Gyo of a lateral acceleration of a vehicle body.

FIG. 9 is a graph showing a relationship between an estimated lateral acceleration Gym of the vehicle body and a target roll amount Rm of the vehicle body.

FIG. 10 is a graph showing a relationship between a longitudinal acceleration Gx of the vehicle body and a target pitch amount Pm of the vehicle body.

[Explanation of symbols]

 2 ... Air spring 4 ... Running state detecting means 6 ... Target gas mass calculating means 8 ... Actual gas mass calculating means 10 ... Supply / discharge control means 12 ... Target volume calculating means 14 ... Target pressure calculating means 16 ... Temperature detecting means 18 ... Calculation Means 20 ... Target fluctuating pressure calculating means 21 ... Reference pressure detecting means 22 ... Vehicle height detecting means 23 ... Vehicle height signal smoothing processing means 24 ... Target vehicle height calculating means 25 ... Vehicle height deviation calculating means 26 ... Integrating means 27 ... Reference pressure Correction means 30 * Shock absorber 32 * Air spring 34 * Air chamber 40 * Air supply control valve 46 * Exhaust control valve 48 * Steering angular velocity sensor 50 Vehicle speed sensor 52 Lateral acceleration sensor 54 Front and rear Acceleration sensor 56 * ... Vehicle height sensor 58 * ... Pressure sensor 60 * ... Temperature sensor 62 ... Electronic control device

Claims (1)

(57) [Claims] An air spring provided for each wheel and having an air chamber therein, running state detecting means for detecting a running state of the vehicle, and an air spring in the air chamber based on the detected running state of the vehicle. Target gas mass calculating means for calculating a target gas mass Mo; real gas mass calculating means for calculating an actual gas mass M in the air chamber; and a deviation Mc between the actual gas mass M and the target gas mass Mo. Supply / discharge control means for controlling the attitude of the vehicle body by controlling supply / discharge of the working gas to / from the air chamber so as to reduce the deviation, wherein the target gas mass calculating means comprises: The air chamber is defined as a sum of a reference volume of the chamber and a target variable volume of the air chamber based on the traveling state of the vehicle detected by the traveling state detecting means A target volume calculating means for calculating a target volume; and a sum of a reference pressure in the air chamber and a target fluctuating pressure in the air chamber based on a running state of the vehicle detected by the running state detecting means. Target pressure calculating means for calculating the target pressure of the air, temperature detecting means for detecting the temperature of the working gas in the air chamber, and the target volume and the target pressure based on the temperature detected by the temperature detecting means, Calculating means for calculating a target gas mass, wherein the target pressure calculating means calculates the target variable pressure, and detects a pressure in the air chamber when the vehicle is stopped as a reference pressure. Reference pressure detecting means, a vehicle height detecting means for detecting an actual vehicle height of a portion corresponding to each wheel, and a signal indicating the actual vehicle height detected by the vehicle height detecting means. Vehicle height signal smoothing means for smoothing the vehicle, target vehicle height calculating means for calculating a target vehicle height of a portion corresponding to each wheel based on the running state of the vehicle detected by the running state detecting means, and the smoothing processing A vehicle height deviation calculating means for calculating a deviation between a later actual vehicle height and the target vehicle height, an integrating means for integrating the vehicle height deviation when the sign of the vehicle height deviation between the left and right wheels is the same, and the integration result And a reference pressure compensating means for compensating the reference pressure based on the reference pressure.