JPH0328011A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To positively restrict pitching phenomenon by correcting a target value for a specified time from the time of detecting the range-position switching so that a phenomenon opposite to a pitching phenomenon being prone to occur due to the range-position switching may be generated. CONSTITUTION:Based on a difference between car height of the front and rear parts of a car body detected by first, second car height detecting means, a detecting means detects an amount of pitch, and a pitching control means controls cylinder devices of the front and rear parts through supply-discharging control valve so that the detected amount of pitch reaches a specified target value, and controls pitching. In this case, when a range-position switching detecting means detects that the range-position is switched from P- or N range to a traveling range, a correction means corrects a target value so that a pitching in the opposite direction to a pitching phenomenon being prone to occur due to the range-position switching is generated for a specified time. Thus, a vehicle can be maintained in a stable position in response to various disturbances.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension device for a vehicle.

(Prior art) The suspension of a ton vehicle, which is generally called a passive suspension, has a damper unit consisting of a hydraulic shock absorber and a spring (or a coil spring in some cases), and the suspension is based on preset characteristics of the damper unit. Suspension characteristics are uniformly set. Of course, the damping force of the hydraulic shock absorber is made variable, but this does not significantly change the suspension characteristics.

On the other hand, recently, active suspensions have been proposed in which the suspension characteristics can be changed arbitrarily, so that the suspension characteristics can be changed arbitrarily. A cylinder device is installed between the unsprung weight and the suspension characteristics are controlled by controlling the supply and discharge of hydraulic fluid to the cylinder device (Japanese Patent Application Laid-Open No. 63-1304
(See Publication No. 18).

In this active suspension, by supplying and discharging hydraulic fluid from the outside, suspension characteristics can be significantly changed for various controls such as vehicle height control, roll control, and pitch control. In such an active suspension, a vehicle height sensor that detects the vehicle height is basically used for attitude control.

(Problem to be Solved by the Invention) By the way, in a truck equipped with an automatic transmission, the so-called Scott phenomenon occurs when the range position is changed when transitioning from a stopped state to a running state. This will cause pitching. More specifically, for example, in the case of a rear-wheel drive vehicle, when switching from P or N range when stopped to D range as the driving range, engine torque is transmitted to the rear wheels. While the wheels try to move forward, the vehicle body tries to stay stationary due to its large inertia. As a result, a Scott phenomenon occurs in which the east height of the rear part of the vehicle body temporarily decreases and the vehicle height of the front part of the vehicle body increases. The degree of this Scott phenomenon is expressed, for example, as a pitch angle indicating the inclination angle of the vehicle body.

On the other hand, it is naturally conceivable to incorporate an active suspension device into a vehicle equipped with an automatic transmission. In this case, it is conceivable that the pitching phenomenon caused by the above-mentioned range position switching can be suppressed by pitching control by the active suspension device. However, since this pitching control is activated to suppress pitching after it has actually occurred, there is a delay in response, and pitching caused by range position switching cannot be sufficiently suppressed.

Therefore, an object of the present invention is to prevent the pitching phenomenon that is about to occur when switching from P range or N range to driving range, assuming that a vehicle equipped with an automatic transmission is equipped with an active suspension system. 5. To provide a suspension device for a vehicle that can reliably suppress the (Structure of the Invention) In order to achieve the above-mentioned object, the present invention basically provides that when the P range or the N range is switched to the driving range, the problem that occurs due to this switching is A pseudo signal that causes pitching in the opposite direction to the pitching to be caused is temporally applied. Specifically, assuming that the vehicle is a vehicle in which the output of the engine is transmitted to the drive wheels via an automatic transmission, as shown in the block diagram in FIG. A cylinder device is installed between the spring 1, the heavy spring and the unsprung heavy device 1, and changes the vehicle height by supplying and discharging hydraulic fluid, and a cylinder device that independently supplies and discharges hydraulic fluid to each cylinder device. a first vehicle height detection means for detecting the vehicle height at the front of the east body; a second vehicle height detection means for detecting the vehicle height at the rear of the vehicle; and the first vehicle. pitch amount determining means that receives outputs from the height detection means and the second vehicle height detection means and determines an actual pitch amount based on the deviation between the vehicle height at the front of the vehicle body and the vehicle height at the rear of the vehicle body; and the pitch amount. pitching control means for suppressing pitching by controlling the supply/discharge control valve so that the bit depth determined by the determination means becomes a predetermined target value; and a range position of the automatic transmission is set to P range or N range. a range position change detection means for detecting that the range position has been changed from the range position to the running range; and a correction means for correcting the target value so as to cause pitching in the opposite direction to the pitching phenomenon. Preferably, the pitching control is performed not only based on the vehicle height signal, but also based on the vehicle height displacement speed signal, as shown in claim 2. (Operations and Effects of the Invention) In the present invention configured as described above, the pitching phenomenon that is about to occur due to range position switching is controlled in a prospective control manner using a corrected target value serving as a pseudo signal. Since pitching control is performed to cancel the occurrence of pitching, it is possible to reliably prevent pitching from occurring without causing a response delay. Furthermore, as described in claim 2, if the pitching control is also performed based on the displacement speed of the vehicle height, the value of the pseudo signal to be given can be reduced, that is, the target value can be corrected. It is possible to prevent pitching with even better response while reducing the pitch. In addition, the function of maintaining the vehicle in a stable posture in response to various disturbances that cause pitching is improved.

(Example) Examples of the present invention will be described below based on the attached drawings. In addition, in the following explanation, the code "F" used with numbers is for the front wheel, rRJ is for the rear wheel, rFRJ is for the right front width, rFLJ is for the left front wheel, rRJ is for the right rear wheel, and rRLJ is for the left rear wheel. Therefore, when there is no need to distinguish between these, these identification symbols will not be used in the explanation.

In Figure 1, 1 (IFR, IFL. IRR, I
R1) is a cylinder device provided for each front, rear, left, and right wheel, which consists of a cylinder 2 connected to the unsprung mass, and a piston rod extending from inside the cylinder 2 and connected to the sprung mass. 3. Inside the cylinder 2, a liquid chamber 5 is defined above by a piston 4 integrated with a piston rod 3, and this liquid chamber 5 and a lower chamber are communicated with each other. As a result, when the hydraulic fluid is supplied to the liquid chamber 5, the piston rod 3 extends and the vehicle height increases, and when the hydraulic fluid is discharged from the liquid chamber 5, the vehicle height decreases.

For the liquid chamber 5 of each cylinder device l, a gas spring 6 (
6FR, 6FL, 6RR, 6R1) are connected.

Each of the gas springs 6 is constituted by four cylindrical springs 7 having a small diameter, and the cylindrical springs 7 are connected to the liquid chamber 5 through an orifice 8 that is parallel to each other.

Of these four cylindrical springs 7, except for one, the remaining three are connected to the liquid chamber 5 via a switching valve 9. As a result, when the switching valve 9 is in the switching position as shown, the four cylindrical springs 7 are communicated only through the orifice 8, and the damping force at this time is small. Furthermore, when the switching valve 9 is switched from the illustrated position, the three cylindrical springs 7 are also communicated with the liquid chamber 5 through the orifice 10 built into the switching valve 9, resulting in a large damping force. Become something. Of course, by changing the switching position of the switching valve 9, the spring characteristics of the gas spring 6 are also changed. The suspension characteristics can also be changed by changing the amount of hydraulic fluid supplied to the fluid chamber 5 of the cylinder device 1.

In the figure, reference numeral 11 denotes a bomb driven by the engine, and high-pressure hydraulic fluid pumped up by the bomb 11 from a reservoir tank l2 is discharged into a common passage l3.

The common passage 13 is branched into a front passage 14F and a rear passage 14R, and the front passage 14F is further divided into a right front passage 14F.
R and a left front passage 14FL. The front right passage 14FR is connected to the liquid chamber 5 of the front right wheel cylinder device IFH, and the front left passage 14FL is connected to the liquid chamber 5 of the front left wheel cylinder device IFH. This front right passage 14FR includes, from the upstream side, a supply flow rate control well 15FR and a pilot valve 16FR as a delay valve.
is connected. Similarly, in the left front passage 14FL,
A supply flow control valve l5FL and a pilot valve 16FL are connected from the upstream side.

A first relief passage 17FR for the right front passage is connected to the front right passage 14FH from between both valves 15FR and 16FR, and this first relief passage 17FR is finally connected to the reservoir via the front wheel relief passage 18F. It is connected to tank l2. And in the first relief passage 17FH,
A discharge flow rate control well 19FR is connected. Further, the passage 14FR downstream of the pilot valve 16FR is connected to the first relief passage 17FH via the second relief passage 20FR, and the relief valve 2 1 FR is connected to this. Furthermore, the passage 1 4F closest to the cylinder device IFR
H is provided with a filter 29FR. This filter 29FR is located between the cylinder device IFR and the valves 16FR and 21PR located closest to the cylinder device IFR, and wear caused by sliding of the cylinder device IFR is removed from the valve 16FR. Prevent soil from flowing to the 2lFR side.

The configuration of the left front transport passage is the same as the right front transport passage, so a redundant explanation will be omitted. A main accumulator 22 is connected to the common passage l3, and an accumulator 23F is also connected to the front wheel relief passage 18F. This main accumulator 22 serves as a pressure accumulation source for hydraulic fluid together with a sub-accumulator 24 to be described later, and is used to prevent insufficient supply of hydraulic fluid to the cylinder device 1. Further, the accumulator 23F is provided to prevent the high-pressure hydraulic fluid in the front wheel cylinder device l from being suddenly discharged to the low-pressure reservoir tank l2, that is, to prevent the water hammer phenomenon. The hydraulic fluid supply and discharge passages for the rear wheel cylinder devices IRR and IRL are also configured in the same manner as for the front wheels, so a redundant explanation thereof will be omitted. However, there is no equivalent to pilot valves 21FR and 21FL in the rear wheel passage.
In addition, the main accumulator 22 is located in the rear wheel passage 14R.
A sub-accumulator 24 is provided in consideration of the fact that the passage length from the front wheel is longer than that for the front wheel.

The common passage l3, that is, each passage 14F for the front and rear wheels.
14R is connected to the front wheel relief passage 18F via a relief passage 25, and a control valve 26 consisting of an electromagnetic on-off valve is connected to the relief passage 25. In FIG. 1, 27 is a filter, and 28 is a pressure regulating valve for adjusting the discharge pressure from the bomb 11 within a predetermined range.
is configured as a variable displacement swash plate piston type and is integrated into the bomb 11 ([}t output pressure 120-160 kg/am2). The pilot valve 16 is opened and closed depending on the pressure difference between the pressure in the front and rear passages 14F or 14R, ie, the common passage 13, and the pressure on the cylinder device i side. For this reason, the front wheel pilot valve 16FR. For 16FL, there are 4 common pilot passages 31F branched from passage 14F.
2 branched from the common pilot passage 31F.
Among the main branch pilot passages, one passage 31FR is connected to the pilot valve 16FH, and the other passage 3IFL is connected to the pilot valve 16FH.
is connected to the pilot valve 16FL.

An orifice 32F is provided in the common pilot passage 31F. The pilot passage for the rear wheels is also configured in the same way. Each of the above pilot valves 16
is constructed as shown in Fig. 2, for example, and the one shown is for the right front wheel. This pilot valve l6
In the casing 33, a main flow path 34 forming a part of the passage 14FH is formed, and for the main flow path 34,
Passage 1 4FR is connected. A valve seat 35 is formed in the middle of the main flow path 34, and an opening/closing piston 36 slidably fitted into the casing 33 is seated on the valve seat 35, thereby opening and closing the pilot valve 16FR. Ru. The opening/closing piston 36 is integrated with a control piston 38 via a valve shaft 37. The control piston 38 is slidably inserted into the casing 33 to define a liquid chamber 39 within the casing 33, and the liquid chamber 39 is connected to a branch pilot passage via a control flow path 40. Connected to 31FR.

The control piston 36 is connected to the return spring 4l.
, the direction in which the opening/closing piston 36 is seated on the valve seat 35,
That is, the pilot valve 16FR is biased in the closing direction. Furthermore, the pressure of the main flow path 34 is applied to the control piston 38 through the communication port 42 on the side opposite to the liquid chamber 39 . As a result, inside the liquid chamber 39 (common passage l)
3 side) becomes 1/4 or less of the pressure in the main flow path 34 (cylinder device IFR side), the opening/closing piston 36 seats on the valve seat 35 and the pilot valve 16FR is closed. Here, when the pressure on the common passage 13 side drops significantly from the state where the pilot valve 16FR is open, this pressure drop is delayed by the action of the orifice 32F, and the liquid chamber 3
9 and therefore the said pilot valve 1 6FR
is closed after a delay from the above pressure drop (in the example, this delay time is set to about 1 second). Next, the operation of each valve mentioned above will be explained. ■Switching valve 9 In the embodiment, the switching valve 9 is operated to increase the damping force only during turning. ■Relief valve 2l The relief valve 21 is normally closed and the cylinder device l
When the pressure on the side is above a specified value (160 to 200 kg in the example)
/cm2), it is opened.

In other words, it serves as a safety valve that prevents the pressure on the cylinder device 1 side from rising abnormally. Of course, the relief valve 2l is a cylinder device IRR for the rear wheels.
, can also be provided for the IRL, but in the example, it is assumed that the vehicle has a weight distribution set to be considerably larger on the front side than on the rear side, and the pressure on the rear wheel side is In consideration of the fact that the pressure does not exceed the pressure, the relief valve 2l is not provided on the rear wheel side.

(2) Flow rate control valves 15, 19 Both the supply and discharge flow rate control valves 15 and 19 are electromagnetic Suburd valves, and can be switched between an open state and a closed state as appropriate. However, when it is in the open state, it has a differential pressure adjustment function that keeps the differential pressure between the upstream and downstream sides almost constant (due to flow rate control, this differential pressure must be kept constant). ). More specifically, the displacement position or opening degree of the flow control valves 15 and 19 is changed in proportion to the supplied current, and this supplied current is determined according to a flow rate-current correspondence map created and stored in advance. Determined based on In other words, the supplied current corresponds to the required flow rate at that time. By controlling the flow rate control valves 15 and 19, the supply and discharge of hydraulic fluid to the cylinder device 1 is controlled, thereby controlling the suspension characteristics.

In addition to this, when the ignition is OFF, this O
For a predetermined period of time (2 minutes in the embodiment) from the time of FF, only the control in the direction of lowering the vehicle height is performed. In other words, it takes into account changes in the payload caused by getting off the vehicle, etc., and prevents the vehicle height from becoming partially high (maintaining the standard vehicle height).
.

■Control Valve 26 The control valve 26 is normally closed by being energized, and is opened in the event of a failure. This failure can occur, for example, when a part of the flow control valves 15 and 19 becomes stuck, when the sensors described below fail, when the hydraulic pressure of the hydraulic fluid fails, or when the bomb 11 fails. There are cases where

In addition, in the embodiment, the control valve 26 is opened after a predetermined period of time (for example, 2 minutes) has elapsed since the ignition was turned off.

Note that when this control valve 26 opens, the pilot valve l
As mentioned above, 6 is closed later. ■Pilot valve l6 As already mentioned, due to the action of the orifices 32F and 32R, the pilot valve 16 is opened with a delay after the pressure in the common passage 13 has decreased. This means that, for example, in the event of a failure where a part of the flow rate control valve 15 remains open, the passage 14FR-14R is
L is closed to confine the hydraulic fluid in the cylinder devices IFR-IRL and maintain the vehicle height. Of course, at this time,
The suspension characteristics are fixed to so-called passive characteristics. Figure 3 shows the control system of the hydraulic fluid circuit shown in Figure 1.In the vehicle shown in Figure 3, although not shown, the engine output is controlled by the torque converter and automatic transmission. It is said to be a rear-wheel drive car, with power transmitted to the rear wheels via the engine.

In FIG. 3, WFR is the right front wheel, WFL is the left front wheel, WRR is the right rear wheel, WRL is the left rear wheel, and U is a control unit configured using a microcomputer. This control unit U includes each sensor 51FR to 51R.
L, 52FR~52RL, 53FR. 53FL, 53R
Signals from the control unit U are input to the switching valve 9 and the flow rate control valve 15 (15).
FR~15R1), 19 (19FR~19R1) and the control valve 26.

The sensors 51FR to 51RL are connected to each cylinder device IF.
It is provided at R to IRL to detect the amount of extension, that is, the vehicle height at each wheel position. Sensor 52FR~5
2RL detects the pressure in the liquid chamber 5 of each cylinder device IFR-IRL (see also Figure 1). sensor 5
3FR, 53FL, and 53R are G sensors that detect acceleration in the vertical direction. However, on the front side of vehicle B, there are two G sensors 53FR at approximately symmetrical positions on the front axle,
53FL, but at the rear of vehicle B, only one G sensor 53R is provided at the middle position between the left and right sides on the rear axle. In this way, one virtual plane representing the vehicle body B is defined by the three G sensors, and this virtual plane is set to be a substantially horizontal plane. The sensor 6l is for detecting vehicle speed. The sensor 62 detects the operating speed of the steering wheel, that is, the steering angular speed (actually, the steering angle is detected and the steering angular speed is calculated from the detected steering angle). The above-mentioned sensor 63 detects the lateral G acting on the vehicle body (in the embodiment, there is one sensor on two axes of the vehicle body).
(only one is provided). The sensor 64 is for detecting the position of the operating lever for changing the range position of the automatic transmission, and is for detecting that the range position has been changed from the P range or the N range to the driving range. The control unit U basically performs active control conceptually shown in FIGS. 4A and 4B, that is, in the embodiment, the vehicle attitude control fil (vehicle height signal control and vehicle height displacement speed control) and the vehicle height control. Performs comfort control Il (vertical acceleration signal control) and vehicle torsion control fil (pressure signal control 1). The results of each of these controls are finally expressed as the flow rate of the hydraulic fluid flowing through the flow rate control valves 15 and 19 as flow rate adjusting means.

Next, an example of how to control the suspension characteristics based on the output of each sensor is shown in Fig. 4A.
This will be explained with reference to FIG. 4B.

The content of this control can be roughly divided into control systems x1 and x2, which control the attitude of the vehicle body B based on the output of the most basic vehicle height sensor and its differential value (vehicle height displacement speed);
Control system x3 that performs ride comfort control based on sensor output
and a control system x4 that performs torsion suppression control of the vehicle body B based on the output of the pressure sensor, and will be explained in detail below.

(Left below) ■ Control f11 The feedback control is based on the control method m).

First, reference numeral 70 calculates the bounce component of the vehicle by summing the outputs XFR, XFL of the left and right front wheels of the vehicle height sensors 51FR to 51RL, and summing the outputs XRR, XRL of the left and right rear wheels. This is a bounce component calculation unit that performs calculations. The code 71 is the output XFR, XF on the left and right front wheels.
From the total value of L, the output XRR of the left and right rear wheels. XRL
This is a pitch component calculation unit that calculates the pitch component of the vehicle by subtracting the total value of . Reference numeral 72 denotes a roll component calculation unit that calculates the roll component of the vehicle by adding the difference XFR-XFL between the outputs of the left and right front wheels and the difference XRR-XRL between the outputs of the left and right rear wheels. be. Reference numeral 73 receives the bounce component of the vehicle calculated by the bounce component calculation unit 70 and the target vehicle height signal TH from the target average vehicle height determination unit 9l, and calculates each bounce control based on the gain coefficient KBI. This is a bounce control unit that calculates the control amount for the wheel flow control valve. The code 74 is
The pitch component of the vehicle calculated by the pitch component calculation unit 7l,
and the target pitch amount Tp from the target pitch amount determination unit 92
is input and is a pitch control unit that calculates the control amount of each flow control valve in pitch control based on the gain coefficient KPI so that the vehicle height corresponds to the target pitch amount Tp. Reference numeral 75 indicates the roll component of the vehicle calculated by the roll component calculation unit 72 and the target roll ilTR from the target roll amount determination unit 93, and the gain coefficients aKRFl, KRR are calculated manually.
This is a roll control unit that calculates the control amount of each flow control valve in roll control based on I so that the vehicle height corresponds to the target roll amount TR.

In order to control the vehicle height to the target vehicle height, each control section 7
The respective control m quantities calculated in steps 3, 74, and 75 are reversed for each wheel (reversed so as to be opposite to the positive and negative values of the vehicle height displacement signals of the vehicle height sensors 51FR to 51RL), and then , the bounce, pitch, and roll control amounts for each wheel are added, and in the control system x1, the flow rate signal QFRI . QFLI, QRR
I. QRLI is obtained. Here, the target vehicle height TH can be kept at a certain constant value, such as 150 mm in terms of the minimum ground clearance of the vehicle. In addition, the target vehicle height TI can be changed, and in this case, TH can be changed stepwise or continuously depending on the vehicle height (for example, when the vehicle speed is 80 km/h or higher). (minimum ground clearance is set to 130mm).

Note that the target pitch amount Tp and target roll ffiTH will be described later. ■Control system X2 (vehicle height displacement speed component) Control system x2 performs pitch control and roll control. First, the pitch control section 78 receives the pitch component from the pitch component calculation section 7l and the target pitch! TP is input. This pitch control unit 78 controls the rate of change of the pitch component (which is the deviation between the vehicle height at the front of the vehicle body and the vehicle height at the rear of the vehicle body) in the direction away from the target pitch amount TP, that is, the change rate from the vehicle height sensors 51FR to 51RL. The amount of change in each signal sampling time (10 msec in the example) is determined.

Then, the control flow rate for each flow rate control valve is determined using the control gain KP2 so that the rate of change in the direction of increasing the pitch amount is reduced.

In addition, the roll amount (roll angle) ゛· from the roll amount calculation section 72 and the target roll amount TR from the target roll amount determining means are input to the roll control section 79. The roll control unit 79 controls a control gain K RF2 so that the rate of change of the actual roll amount in the direction away from the target roll amount TR is reduced for each set of left and right front wheels and left and right rear wheels.
Alternatively, KRR2 is used to determine the control flow rate for each flow control valve.

The control am determined by each of the control units 78 and 79 is added for each flow rate control valve (each cylinder device IFR to IR1) after the respective positive and negative values are reversed, and the controlled flow rate Q FR2QFL2 in the control system x2 is calculated. , QRR2. Q
RL2 is determined. Note that "S" shown in each of the control units 78 and 79 is an operator showing differentiation. ■Control system X3 (vertical acceleration component) First, reference numeral 80 indicates three vertical acceleration sensors 53FR,
53FL. This is a bounce component calculating section that calculates the bounce component of the vehicle by summing the outputs GFR, GFL, and GR of the 53R. The code 8l indicates three vertical acceleration sensors 53F.
R. Output GF for left and right front wheels among 53FL and 53R
This is a pitch component calculation unit that calculates the pitch component of the vehicle by subtracting the rear wheel side output GR from the total value of each half value of R, GFL. Reference numeral 82 is a roll component calculation unit that calculates the roll component of the vehicle by subtracting the output GFL of the left front wheel from the output GFR of the right front wheel. A bounce control unit 83 receives the bounce component of the vehicle calculated by the bounce component calculation unit 80 and calculates the amount of control m for each wheel flow control valve in bounce control based on the gain coefficient KB3. It is. Reference numeral 84 denotes a pitch control unit to which the pitch component of the vehicle calculated by the pitch component calculation unit 81 is input, and calculates the control amount of each flow control valve in pitch control based on the gain coefficient KP3.

Reference numeral 85 receives the vehicle roll component calculated by the roll component calculation unit 82, and calculates gain coefficients KRF3 and KR.
This is a roll control unit that calculates the control amount of each flow rate control valve in roll control based on R3.

In order to suppress the vertical vibration of the vehicle with a bounce component, a vibration component, and a roll component, each control fit amount calculated by each of the control units 83 to 85 is reversed in sign for each wheel, and then The bounce, pitch, and roll control amounts for the wheels are added, and in the control system X3, the flow rate signal QFR3 . QFL3
, QRR3, and QRL3 are obtained.

(2) Control System x4 First, a warp control section 90 is provided, which includes a front wheel side hydraulic pressure ratio calculation section 90a and a rear wheel side hydraulic pressure ratio calculation section 90b.

The front wheel side hydraulic pressure ratio calculating section 90a calculates the hydraulic pressure signals PFR, P of the two front wheel side hydraulic pressure sensors 52FR, 52FL.
When FL is input, the total hydraulic pressure on the front wheel side (P FR+
Left and right fluid pressure difference (P FR - PF
1) ratio (PFR − PF1) / (PFR+
Calculate PF1). Also, the rear wheel side hydraulic pressure ratio calculation section 90b
is the same hydraulic pressure ratio on the rear wheel side (PRR-PR1) /
Calculate (PRR+PR1). Then, after multiplying the rear wheel side hydraulic pressure ratio by a predetermined value by a gain coefficient ωF, this is subtracted from the front wheel side hydraulic pressure ratio, and the result is multiplied by a predetermined value by a gain coefficient ωF, and for the front wheels, a predetermined value is obtained by a gain coefficient ωC. Then, in order to equalize the control amount for each wheel between the left and right wheels, in the control system x4,
Flow rate signals of the corresponding flow rate control valves QFR4, QFL4
．． QRR4. QRL4 is obtained. ■Vehicle height displacement components QFRI, QFLI, QRR of the flow rate signal determined for each flow rate control valve as described above for each control system XI-X4
I. QRLI Vehicle height displacement speed component Q FR2QF
L2 QRR2, QRL2, vertical acceleration component Q
FR3. QFL3, QRR3, QRL3
, and pressure components QFR4, QFL4, QRR4
．． QRL4 is finally added to obtain final total flow signals QFR, QFL, QRR, and QRL.

Further, the control gain of the control formula used in the explanation of FIGS. 4A and 4B above is switched and controlled by a control system as shown in FIG.

First, the steering angular velocity θM is multiplied by the vehicle speed V, and a reference value G1 is calculated from the result θM-V, and a value Sl is input to the turning determination section. Also, the current lateral acceleration G of the vehicle
A value S2 obtained by subtracting the reference value G2 from S is input to the turning determination section. Then, in the turning determination section, input S1 or S2≧0
In this case, it is determined that the vehicle is turning, and a suspension characteristic hardening signal Sa is output, and each hydraulic cylinder l
In order to improve the followability of the flow rate control, the damping force switching valve lO is switched to the throttle position, each of the above control gains Ki is set to KHard, and the target roll angle TR at that time is determined from a map stored in advance. Lateral acceleration G
Set to the value corresponding to s. An example of this map is shown in
It is shown in the figure. Incidentally, in the case of a passive suspension vehicle, as shown in FIG. 7, the roll angle (positive roll) increases as the lateral G increases.

On the other hand, in the case of the inputs Sl and O in the turning determination section, it is determined that the vehicle is traveling straight, and the suspension characteristic softening signal sb
is output, the damping force switching valve IO is switched to the open position, the control gain Ki is set to the normal value Ksoft, and the target roll angle TR is set to O. Scott: ``Positive 1 is also 1'' Next, change the range position, that is, P range or N range.
Control points for preventing the Scott phenomenon that occurs when switching from the range to the travel range will be explained.

This Scott phenomenon appears as a phenomenon in which the vehicle height at the front of the vehicle body becomes high and the vehicle height at the rear of the vehicle body decreases because the rear wheels WRR and WRL are used as driving vehicles in the embodiment. From this point of view, in this explanation, the pitching control in the control systems XI and high to low,
The target pitch amount Tp is corrected so as to increase the height of the rear portion of the vehicle body.

The correction of the pitch amount TP mentioned above will be explained with reference to FIG. 8. In FIG. 8, ! 20, ffl.
I22 indicates the longitudinal direction of the vehicle, α indicates the position of the front wheel,
β indicates the position of the rear wheel, and O indicates the center point between the front and rear wheel positions α and β. Under such a premise, the target pitch amount TP is usually zero, that is, the position α and the position β are at the same height (
vehicle height), and the line in the longitudinal direction of the heavy body at this time becomes 0°C.

Now, if we consider that the Scott phenomenon occurs and the front part of the car body becomes higher by FS and the rear part of the car body becomes higher by RS (I
FSI=lRSI). The vehicle body longitudinal direction line changes as shown by f21. The actual pitch amount at this time is
When expressed as a stroke value, it is SP, and when expressed as an angle, it is expressed as θP. In the present invention, in order to prevent the pitch from changing from 20 to 121, the target pitch amount TP is corrected to provide pitching in a direction that cancels out the pitching that occurs during pitching. In other words, the target pitch M is maintained for a predetermined time in synchronization with the range position switching.
Correct TP in the direction shown by 22. As a result, the 4th A
The pitch control section 74 shown in the figure performs control to lower the front part of the vehicle body and raise the rear part of the vehicle body, so that the Scott phenomenon is canceled out as a result.

On the other hand, in the pitch control unit 78 of FIG. 4A, when the corrected target bit value TP corresponds to 122, control is performed to make I20 match β2. The control amount is increased as the amount of change per unit time from 20 to 122, that is, the rate of change is larger. Since the change from CO to 22 is made immediately with the switching of the range position, in other words, it is made in an extremely short period of time, that is, the sampling interval of the output signals of the vehicle height sensors 51FR to 51RL, so that the above change rate is becomes extremely large. Also, I2
The change from 0 to β2 is performed immediately in synchronization with the range position switching, and the pitch control section 78 immediately starts controlling the Scott phenomenon prevention. Therefore, the amount of correction from CO to the 22 directions (the amount of correction of the target pitch amount TP) is actually sufficiently small. Of course, the fact that this correction amount is small and uniform is also advantageous from the viewpoint of preventing hunting in control after correction of the target pitch voltage is stopped.

Flowchart Next, the control for changing the target pitch amount TP will be explained with reference to a flowchart. Note that in the following explanation, S indicates a step.

(2) Figure 9 In the example shown in Figure 9, the target pitch amount TP is corrected to a constant value for a predetermined period of time.

First, in SL, it is determined whether it is time to switch from the P range or the N range to the driving range. This Sl
If the determination is NO, TP is set to zero in S2 and the control is ended.

On the other hand, when the determination in S is No, the target pitch amount TP is -3 (indicates the degree of correction in the 122 direction in FIG. 8, and is expressed in mm as the vehicle height displacement amount in the example). ).

Thereafter, in S4, it is determined whether a predetermined period of time (for example, 2 seconds) has elapsed since the determination in S1 was YES. If the determination in S4 is No, the process returns to S3, and the control ends when the determination in S4 becomes YES (1=11).

■Figure 10 In the example shown in Figure 10, the initial value immediately after the range position switching described above is set to a large value, and then this initial value is decreased exponentially as time passes. .

First, in Sl1, it is determined whether or not it is time to switch the range position, as in S1 described above.

If this Sll judgment is No. After the target pitch gTp is reset to 0 at Sl2, it is reset to a flag O at Sl3, and the control ends.

If the determination at Sl1 is YES, it is determined at Sl4 whether the flag is 1 or not. Immediately after transitioning from Sl+ to 314, the flag is 0, so at this time, after resetting the timer count value to O in S5,
A flag is set to 1 at I6. After this, Sl
At step 7, the target pitch f'l T P is set to an initial value A (which corresponds to the value set at S3 in FIG. 9 and corresponds to the actually occurring pitch collapse, which is 10 mrn).

After Sl'7, at Sl8, it is determined whether a predetermined time has elapsed from the time when the determination at Sl1 became YES (actually, from the time when the timer was reset at Sl5). This 3
If the determination in step 18 is No, the process returns to SI4, but at this time, the determination in SI4 is YF. Became S, 319
will be moved to In this Sl9, after counting up the timer, in S20. According to the attenuation formula shown therein, the target bit ITP is set (TP decrease).

Note that the equations in the attenuation equation (h) are as shown in FIG. I1. After this S20, the process moves to SI8. And S18
If the determination becomes YES, the control ends.

The above-mentioned FIG. 9 is suitable for cases where there are few supplementary 1E bits, that is, when pitching control using a displacement speed signal is also used. Further, FIG. 10 is suitable when the correction pitch amount is large and the pitching is controlled using only the displacement signal.

Although the embodiments have been described below, the present invention is not limited thereto, and includes, for example, the following cases.

■It can be similarly applied to moe-wheel drive vehicles. In this case, the correction direction of the L1 mark bitch may be set in the opposite direction to that in the embodiment.

■The present invention can also be applied when switching to the R range, which is the selection of the reverse gear. good.

■Supply control valve 15 and discharge control valve? (separately from 19)
7, but for example, by using one solenoid valve with 3 boats and 3 positions, both valves can be installed in one
5, 19 can also be configured.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the overall circuit of an active suspension. FIG. 2 is a sectional view showing an example of the pilot valve in FIG. FIG. 3 is a diagram showing a control system of the circuit shown in FIG. FIGS. 4A, 4B, and 5 are overall system diagrams showing examples of active control. FIG. 6 is a diagram showing an example of roll characteristics in an active suspension vehicle. FIG. 7 is a diagram showing an example of roll characteristics in a passive suspension vehicle. FIG. 8 is a simplified explanatory diagram schematically showing the control contents of the present invention. 9 and 10 are flowcharts showing control examples of the present invention. FIG. 11 is a diagram that does not show the meaning of the damping formula used for the control in FIG. 10. FIG. 12 is a block diagram showing the overall configuration of the present invention. FIG. 9 IFR-IRL. : Cylinder device +5PR-15Rl: Supply control valve 19FR-19Rl-: Discharge control valve 5 1 F' R ~ 5 1 R I. :Vehicle height sensor U
: Control unit 5: Liquid chamber 64: Sensor (range position detection) 7l: Bitch component calculation section 74: Pitch control section (vehicle height displacement component) 78: Pitch control section (vehicle height displacement speed component) 92: Target pitch arrival determination Section Patent Applicant Mazda Motor Corporation 40 39 Figure 6 Figure 7 Horizontal G Figure 8 Figure 9 Figure 10

Claims (2)

[Claims] (1) In a vehicle in which the output of the engine is transmitted to the drive wheels via an automatic transmission, a
Each is installed between the sprung weight and the unsprung weight,
A cylinder device that changes vehicle height by supplying and discharging hydraulic fluid; A control valve for supplying and discharging hydraulic fluid to each of the cylinder devices independently, and detecting vehicle height at the front of the vehicle body. a first vehicle height detection means for detecting the vehicle height at the rear of the vehicle; a second vehicle height detection means for detecting the vehicle height at the rear of the vehicle body; pitch amount determining means for determining an actual pitch amount based on the deviation between the vehicle height and the vehicle height at the rear of the vehicle; pitching control means for suppressing pitching by controlling a control valve; range position switching detection means for detecting that the range position of the automatic transmission has been switched from P range or N range to travel range; Correction for correcting the target value for a predetermined period from the time when the range position switching is detected by the range position switching means so as to cause pitching in the opposite direction to the pitching phenomenon that is about to occur due to the range position switching. A suspension device for a vehicle, comprising: means; (2) In claim 1, pitching is performed by controlling the supply/discharge control means so that the rate of change of the pitch amount determined by the pitch amount determining means in a direction away from the target value is reduced. A suspension device for a vehicle, further comprising second pitching control means for suppressing pitching.