JP2707508B2 - Vehicle 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 a suspension control system for a vehicle, which suppresses the roll of the vehicle body during a turn.

[0002]

2. Description of the Related Art At the time of turning, air is supplied to an air spring chamber of a suspension unit on the outer wheel side at a steering wheel angle, a steering wheel angular velocity, and the like.
A vehicle suspension device that supplies a set amount according to the vehicle speed, discharges a set amount of air from the inner wheel side, and controls the damping force to be hard, thereby suppressing a roll at the time of turning. It is widely known in, for example, JP-A-64-62108.

[0003]

When a vehicle equipped with such a vehicle suspension device is turned on a high μ road having a high coefficient of road surface friction, the roll generated on the vehicle body during turning can be effectively reduced. Can be suppressed.

However, when a vehicle equipped with the above device is turned on a low μ road having a low coefficient of road surface friction, abrupt load movement by roll control deteriorates tire grip and ground contact, and causes understeer. There was a problem of promoting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to control the supply / discharge control slowly during roll control on a low μ road to suppress abrupt load movement to suppress understeering. It is an object of the present invention to provide a vehicle suspension control device.

[0006]

SUMMARY OF THE INVENTION A suspension control device for a vehicle according to the present invention is provided with a roll detecting means for detecting a cause of a roll on a vehicle body and a support force for the vehicle body which can be independently adjusted. And a control means for changing the supporting force of the left and right suspension units by an amount corresponding to the detection output of the roll detection means so as to suppress the roll of the vehicle body. And a friction coefficient detecting means for detecting a friction coefficient between the road surface and the tire, wherein the control means is adapted to detect the friction coefficient when the friction coefficient detected by the friction coefficient detecting means is lower than a predetermined value. The speed of change in the supporting force of the suspension unit when the vehicle is restrained is reduced.

[0007]

When the friction coefficient .mu. Detected by the friction coefficient detecting means is lower than a predetermined value, the rate of change in the supporting force of the suspension unit during roll suppression, for example, the supply / exhaust speed, is reduced.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, FS1 is a left front wheel side suspension unit, FS2 is a right front wheel side suspension unit, RS1 is a left rear wheel side suspension unit, and RS2 is a right rear wheel side suspension unit. These suspension units FS1, FS2,
Since the RS1 and the RS2 have the same structure as each other, the suspension unit will be described using the reference symbol S, except for the case where the front wheel and the rear wheel or the left wheel and the right wheel are separately described. .

The suspension unit S has a shock absorber 1. The shock absorber 1 includes a cylinder mounted on a wheel side, and a piston rod 2 having a piston swingably fitted in the cylinder and having an upper end supported on a vehicle body side. Also,
The suspension unit S includes an air spring chamber 3 having a vehicle height adjusting function coaxially with the piston rod 2 above the shock absorber 1. A part of the air spring chamber 3 is formed by a bellows 4, and by supplying and discharging air to the air spring chamber 3 through a passage 2 a provided in the piston rod 2, the vehicle height is raised or Can be lowered.

A control rod 5 having a valve 5a for adjusting the damping force is provided at the lower end of the piston rod 2. The control rod 5 is rotated by an actuator 6 attached to the upper end of the piston rod 2 to drive a valve 5a. By the rotation of the valve 5a, the damping force of the suspension unit is set in three stages: hard (hard), medium (middle), and soft (soft).

The compressor 11 compresses the air taken in from the air cleaner 12 and supplies the compressed air to the high-pressure reserve tank 15a via the dryer 13 and the check valve 14. That is, since the compressor 11 compresses the air taken in from the air cleaner 12 and supplies it to the dryer 13, the compressed air dried by the silica gel or the like in the dryer 13 is stored in the high-pressure reserve tank 15a. The compressor 16 has a suction port connected to the low-pressure reserve tank 15 b and a discharge port connected to the high-pressure reserve tank 1.
5a. Reference numeral 18 denotes a pressure switch that is turned on when the pressure in the low-pressure reserve tank 15b exceeds a first set value (for example, the atmospheric pressure). When the compressor 16 outputs an ON signal of the pressure switch 18, the compressor 16 is driven by a compressor relay 17 which is turned on by a signal from a control unit 36 described later. As a result, the pressure in the low-pressure reserve tank 15b is always kept below the first set value.

The air supply from the high-pressure reserve tank 15a to each suspension unit S is performed as shown by a solid line arrow in FIG. That is, the compressed air in the high-pressure reserve tank 15a is supplied to the air supply flow control valve 19, the front air supply solenoid valve 20, the check valve 2
1. Supplied to the suspension units FS1 and FS2 via the front left solenoid valve 22 and the front right solenoid valve 23. Similarly, the compressed air in the high-pressure reserve tank 15a is supplied to the supply flow control valve 1
9. Suspension unit R via rear air supply solenoid valve 24, check valve 25, rear left solenoid valve 26, rear right solenoid valve 27
It is sent to S1 and RS2.

On the other hand, the exhaust from each suspension unit S is performed as shown by a broken arrow in FIG. That is,
The compressed air in the suspension units FS1 and FS2 is supplied to the low-pressure reserve tank 1 through the exhaust direction switching valve 28 including solenoid valves 22 and 23 and a three-way valve.
5b and the solenoid valves 22 and 2
3, exhaust direction switching valve 28, check valve 29,
In some cases, the air is discharged to the atmosphere via the dryer 13, the exhaust solenoid valve 31, the check valve 46, and the air cleaner 12. Similarly, the suspension unit RS
The compressed air in RS1 and RS2 is supplied to solenoid valves 26 and 2
7. The case where the fuel is supplied into the low-pressure reserve tank 15b through the exhaust direction switching valve 32 and the case where the solenoid valve 2
6, 27, the exhaust direction switching valve 32, the check valve 33, the dryer 13, the exhaust solenoid valve 31, the check valve 46, and the air cleaner 12 may be discharged to the atmosphere. The check valves 29, 3
Exhaust direction switching valve 2 between dryer 3 and dryer 13
A passage provided with a small-diameter throttle L is provided as compared with a passage that directly communicates the low-pressure reserve tank 15b with the low-pressure reserve tank 15b.

The above-described solenoid valves 22, 2
5, 26, 27, 28 and 32, as shown in FIGS. 5 (A) and 5 (B), the air flow as indicated by arrow A when ON (energized state) and the arrow B when OFF (non-energized). Such air circulation is allowed respectively. Also, the supply solenoid valves 20, 24 and the exhaust solenoid valve 31 are shown in FIG.
As shown in (B) and (B), the flow of air as indicated by arrow C is allowed when ON (energized state), and the air flow is prohibited when OFF (non-energized state). When the supply air flow control valve 19 is in the off state (non-energized), air flows through the orifice o as shown in FIG. 7A, so that the air flow rate is small. As shown in B), the air flows through the orifice o and the large-diameter path D, so that the air flow rate increases.

Reference numeral 34F denotes a front vehicle height sensor mounted between the lower arm 35 of the front right suspension of the vehicle and the vehicle body to detect the front vehicle height, and 34R denotes a lateral rod 37 of the rear left suspension of the vehicle and the vehicle body. It is a rear vehicle height sensor that is mounted in between and detects the rear vehicle height. The signals detected by the two vehicle height sensors 34F and 34R are supplied to a control unit 36 including an input circuit, an output circuit, a memory, and a microcomputer.

Reference numeral 38 denotes a vehicle speed sensor built in the speedometer, and supplies a detected vehicle speed signal to the control unit 36. An acceleration sensor 39 detects an acceleration acting on the vehicle body, and supplies the detected acceleration signal to the control unit 36. 30 is a soft (SOFT), auto (AUTO), sports (SP)
ORTS) Roll control mode selection switch to select, 40
Is a steering sensor for detecting the rotational speed of the steering wheel 41, that is, the steering angular speed. An accelerator opening sensor 42 detects the depression angle of an accelerator petal of an engine (not shown). The signals detected by the roll control selection switch 30 and the sensors 40 and 42 are supplied to the control unit 36. 43 is compressor 1
1, and is controlled by a control signal from the control unit 36. 44, the pressure in the high-pressure reserve tank 15a is set to a second set value (for example, 7 kg / cm
² ) A pressure switch that is turned on when the following occurs. The signal of the pressure switch 44 is supplied to the control unit 36. Then, even if the pressure in the high-pressure reserve tank 15a becomes equal to or less than the second set value and the pressure switch 44 is turned on,
When the compressor 8 is on, that is, when the compressor 16 is being driven, the driving of the compressor 11 is prohibited. Reference numeral 45 denotes a pressure sensor provided in a passage connecting the solenoid valves 26 and 27 to each other, and detects an internal pressure of the suspension units RS1 and RS2 on the rear side.

The above-mentioned solenoid valves 19, 2
0, 22, 23, 24, 26, 27, 28, 31, and 3
The control of 2 is performed by a control signal from the control unit 36.

The rotation of the steering wheel 41 is transmitted via a steering shaft 51 to a power steering device 52 as a front wheel steering actuator for steering the front wheels. This power steering device 52
Is the pressure PL in the left and right pressure chambers of the front wheel steering actuator.
, PR are provided, respectively. Based on the sensor signals from the pressure sensors 53 and 54, the pressure difference between the two pressure chambers is determined as the power steering pressure.

The pressures PL and PR of the left and right pressure chambers detected by the above-described pressure sensors 53 and 54 are output to a road surface μ estimating unit 55 for estimating the road surface μ. The vehicle speed V detected by the vehicle speed sensor 38 described above is provided to the road surface μ estimating unit 55.
And a steering angle θH from a steering angle sensor (not shown) for detecting the steering angle of the steering wheel 41, that is, the steering wheel angle.

Hereinafter, the detailed configuration of the road μ estimation unit 55 will be described with reference to FIG. In FIG. 2, the pressures PL and P of the left and right pressure chambers detected by the pressure sensors 53 and 54 are shown.
R is sent to the subtraction unit 60, and the power steering pressure ΔP (= PR-P
L) is calculated. The power steering pressure ΔP is supplied via a phase compensation filter 61 to a road surface μ calculating unit 62 serving as friction coefficient detecting means .

Here, the phase compensation filter 61 is a filter for removing noise and compensating for a phase advance of the power steering pressure ΔP with respect to the steering wheel angle θH in the steering transition period of the steering wheel 41. That is, when the steering wheel 41 is turned, the power steering pressure .DELTA.P rises quickly and quickly with respect to the steering wheel angle .theta.H, whereas when the steering wheel 41 is turned back, the power steering pressure .DELTA.P rapidly rises with respect to the steering wheel angle .theta.H. However, the power compensation pressure Δ
By performing a filtering process on P, a phase shift between the steering wheel angle θH and the power steering pressure ΔP can be removed.

The road surface μ calculating section 62 detects or calculates the road surface μ from the power steering pressure ΔP, the steering wheel angle θH, and the vehicle speed V. The principle of the calculation will be described below with reference to FIG. I do.

When the right front wheel 1R is steered and the inclination angle of the right front wheel 1R with respect to the traveling direction R of the right front wheel 1R, that is, the side slip angle is βf, the cornering force CF is expressed by the following equation (1). Can be.

[0024]

(Equation 1) Here, the cornering force CF with respect to the side slip angle βf
Is greatly different depending on the condition of the road surface, as shown in FIG. 4, and the higher the road surface μ, the more the side slip angle βf
It becomes a large value with the increase of. In FIG. 3, L indicates a line along the longitudinal direction of the vehicle body, and δf indicates a front wheel steering angle.

Cornering force CF and power steering pressure ΔP
Is almost proportional from the mechanical relationship as is apparent from FIG. 3, and if the above equation is rewritten with the power steering pressure ΔP, the following equation is obtained.

ΔP = C1 · βf · μ (1) Here, C1 is a constant.

On the other hand, regarding the sideslip angle βf, the vehicle speed V,
It can be expressed by the following equation from the steering wheel angle θH and the road surface μ.

Βf = C3 · V ² · θH / (μ + C2 · V ² ) (2) where C2 and C3 are constants.

From the equations (1) and (2), the power steering pressure Δ
The ratio between P and the steering wheel angle θH, that is, ΔP / θH, can be expressed by the following equation.

ΔP / θH = μ · C1 / C3 · V ² / (μ + C2 · V ² ) (3) Therefore, the power steering pressure Δ supplied to the road surface μ estimating unit 55
By substituting P, the steering wheel angle θH, and the vehicle speed V into the above equation (3), the road surface μ can be calculated.

The road surface μ calculated by the road surface μ estimating section 55 is
Next, the signal is output via the μ variation control unit 63 and the stabilizing filter 64. Here, the μ variation limiting unit 63
When the change rate of the road surface μ is within a predetermined range, the road surface μ is output to the next stabilizing filter 64, and the stabilizing filter 64 is a filter for stabilizing the value of the road surface μ.

The road surface μ estimating section 55 outputs the RMU value as the road surface μ value to the control unit 36 described above.

Next, the operation of the embodiment of the present invention configured as described above will be described. FIG. 14 is a flowchart schematically showing a series of roll control performed by the control unit 36. First, in a rough road determination routine (step A1) as a rough road determination unit, a so-called rough road determination process is performed. That is, in the rough road determination routine, when the output change of the front vehicle height sensor 34F is equal to or higher than MHz (N times or more in 2 seconds), the dead zone of the G sensor 39 is widened and the roll control of the roll control is performed. Erroneous operation is reduced. Then, in a roll control routine (step A2) as roll control means, roll control, that is, air is supplied to the contraction side suspension unit and exhausted from the extension side suspension unit to prevent the body from rolling during turning. ing. The supply / exhaust time during the roll control is corrected in a supply / exhaust correction routine (step A3) as a supply / exhaust time correcting means, and the four-wheel independent supply / exhaust time is determined.
Further, in the damping force switching routine (step A4) as the damping force switching means, the damping force of each suspension unit is set to an optimal one among hard (hard), medium (middle), and soft (soft). You.

Next, the detailed operation of the roll control routine (step A2) will be described with reference to the flowcharts of FIGS. First, the control unit 36 reads the vehicle speed V detected by the vehicle speed sensor 38, the lateral acceleration G output from the G sensor 39, its differential value 2 and the steering wheel angular speed number 3 detected by the steering sensor 40 ( Steps C1 to C3). Then, it is determined whether the steering wheel angular velocity number 4 is greater than 30 deg / sec (step C4). That is, it is determined whether the steering wheel is steered. If “YES” is determined in step C4, “G × number 5” is determined to be positive (step C4).
5). That is, it is determined whether the acceleration G in the left-right direction and the steering wheel angular velocity number 6 are in the same direction, and if it is determined to be “positive”, it is turned to the cutting side, and if it is determined to be “negative”, it is turned to the turning side. It means that the steering wheel is being steered. When it is determined as “YES” in the step C5, the selection is made according to the user's preference.
The control level TCH according to the vehicle speed and the steering wheel angular velocity is obtained by referring to any one of the V-number 7 maps (step C6). In this step C6,
When the soft mode is selected as the roll control mode by the roll control selection switch 30, the map in FIG. 9 is displayed when the auto mode is selected as the roll control mode. When the sports mode is selected, the map in FIG. 10 is selected. Then, the control level TCH of each map
And the supply / exhaust time and the damping force as shown in FIG. 12 are selected. The relationship among the steering wheel angular velocity number 8, the vehicle speed V, the control level, the mode, the supply / exhaust time, and the damping force shown in FIGS.
Is stored in the internal memory.

[0035]

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5)

(Equation 6)

(Equation 7)

(Equation 8) The supply and exhaust times TCS, TCS for the front and rear wheels are independent by a supply and exhaust correction routine which will be described in detail later with reference to FIGS.
CE is corrected and calculated (step C7). Next, it is determined whether the control flag is set or distorted (step C).
8). Since the roll control has not been started yet, "N
"O" is determined, and the process proceeds to step C9. This step C
At 9, it is determined whether the supply / exhaust flag SEF is set. The above air supply / exhaust correction routine (step C
If the supply / exhaust flag SEF is set in 7), the control flag is set and the supply / exhaust timer T = 0
(Steps C10 and C11). Then, the process proceeds to step C12, where it is determined whether the differential pressure is being held, that is, whether a differential pressure holding flag described later is set. If there is a differential pressure, the front and rear exhaust direction switching valves 2
8, 32 are turned off so that air discharged from the front or rear is discharged to the low-pressure reserve tank 15b. This is because the exhaust direction switching valves 28 and 32 are on in the state where the differential pressure is being held.
This is because it is necessary to turn off 8, 32. Next, in the air supply / exhaust correction routine of step C7, it is determined whether the air supply coefficient KS = 3 is set (step C7).
14) If not set (ie, KS = 1)
The air supply flow control valve 19 is turned on, and the large-diameter path D
(FIG. 7) opens to increase the supply air flow (step S).
15). In other words, as shown in FIG. 20, KS = 1 is the case where the control level TCH is determined from the vehicle speed-handle angular velocity map, and therefore, the air flow rate is increased in order to perform rapid roll control.

Next, the front and rear air supply valves 20,
24 is turned on (step C16). Then, the direction of the acceleration G in the left-right direction is determined by the control unit 36 (step C17). That is, it is determined whether the direction of the acceleration G in the left-right direction is positive or negative. Here, when the acceleration G is positive, the acceleration G is on the right side in the traveling direction,
That is, it is determined that the vehicle is turning left. On the other hand, when the acceleration G is negative, it is determined that the acceleration G is a left turn in the traveling direction, that is, a right turn. Therefore, when it is determined that the acceleration G is right (turn left), the front and rear left solenoid valves 22 and 26 are turned on (step C18). As a result, the air in each of the air spring chambers 3 of the left suspension unit is discharged into the low-pressure reserve tank 15b via the valves 22 and 26 which are in the ON state, respectively, and the air spring chambers 3 of the right suspension unit are also discharged. The air supply valves 20, 2 which are in the ON state respectively
Air is supplied from the high-pressure reserve tank 15a via the valves 4 and 4 in the off state.

On the other hand, if it is determined that the acceleration G is left (turn right), the front and rear right solenoid valves 2
3, 27 are turned on (step C19). As a result, the air in each air spring chamber 3 of the right suspension unit is discharged into the low-pressure reserve tank 15b via the valves 23 and 27 which are in the ON state, respectively, and the air in each air spring chamber 3 of the left suspension unit is also formed. Air is supplied from the high-pressure reserve tank 15a via the air supply valves 20, 24 in the on state and the valves 22, 26 in the off state, respectively.

Next, the swingback flag is reset, the above-described differential pressure holding flag is set, and the duty timer TD, the duty counter Tn, and the duty time counter Tmn are set to zero (steps C20 to C24).
Hereinafter, the process returns to step C1. Then, the process proceeds to Step C8 through the processes of Steps C1 to C7.
At this time, since the control flag is being set, "YES" is determined in the step C8, and the process proceeds to the step C25.
Then, in step C25, the timer T is updated by adding the interval time INT. And the timer T
Roll control that supplies and exhausts the air spring chambers of the left and right suspension units according to the left and right G direction until the count value of the timer T exceeds the air supply time TCS or the count value of the timer T exceeds the exhaust time TCE. Is performed continuously. By the way, when the count value of the timer T becomes equal to or longer than the exhaust time TCS, "YES" is determined in step C26, the flow control valve 19 is turned off, the air supply solenoid valves 20, 24 are turned off, and the air supply operation is stopped. (Steps C27 and C27)
28). As a result, the air spring chamber 3 on the air-supplied side is maintained in the high-pressure state where air is supplied for the air supply time TCS. When the count value of the timer T becomes equal to or longer than the exhaust time TCE, "YES" is determined in step C29, the exhaust direction switching valves 28 and 32 are turned on, and the exhaust operation is stopped (step C30). As a result, the exhausted air spring chamber 3 is kept in the exhausted low pressure state for the exhaust time TCE. The direction of the acceleration G in the left-right direction is stored in the memory M
g, and if “timer T ≧ TCS”, the control is reset and the roll control is stopped, and that state is maintained (steps C32 and C33). In this way,
Rolls generated on the vehicle body during cornering are suppressed.

Although the above processing has been described for the case where the steering wheel is suddenly steered, even when "Equation 9≤30 deg / sec", "G × Equation 10" is positive (step C3).
4), the control level TCG is determined by referring to the G sensor map of FIG. 11, and the same processing as when TCH is determined is performed to perform the roll control. In FIG. 11, V1
Is set at 30 km / h and V2 is set at 130 km / h. The supply / exhaust time and damping force corresponding to this control level TCG are shown in FIG.
Required from 3. Similarly, the relationship between the left and right G, the vehicle speed V, the control level, the mode, the supply / exhaust time, and the damping force shown in FIGS. 11 and 13 is stored in the memory in the control unit 36. As is clear from FIGS. 11 and 13, the supply / exhaust time finally obtained from the G sensor map also differs depending on the mode selected by the control switch 30. Although the soft mode is not described in FIG. 13, this means that when the soft mode is selected, the control level is always zero in the G sensor map.

[0040]

(Equation 9)

(Equation 10) As will be described in detail later in the description of the supply / exhaust time correction routine C7, in the present apparatus, the supply time for the front wheels and the supply / exhaust time for the rear wheels are set to be different from each other. Therefore, the counting of the supply / exhaust time and the supply / exhaust time based on the count are performed independently on the front wheel side and the rear wheel side.

By the way, when "G × number 11" is negative, that is, when the steering wheel is on the return side, the map of FIG. 9 is referred to and the vehicle speed-steering wheel angular velocity map on the return side is referenced (step C36). , The threshold number 12 is obtained,
It is determined whether the return side handle angular velocity number 13 ≧ number 14 (step C37). In this step C37, "Y
If "ES" is determined, it is determined whether the temporal change number 15 of the acceleration G in the left-right direction is 0.6 g / sec or more (step C38). Here, the above steps C37 and C3
If it is determined to be “YES” in 8, that is, if the steering wheel is suddenly returned to the neutral position and the temporal change G of the acceleration G is large when shifting from turning to straight running, Since the so-called swingback of rolling to the opposite side after passing through the neutral state occurs, the processing after step C39 is performed to prevent this.

[0042]

[Equation 11]

(Equation 12)

(Equation 13)

[Equation 14]

(Equation 15) In step C39, it is determined whether the swingback flag is set. Here, when the process first comes to step S39, the swingback flag is not set, so that
If the determination is "NO", the swingback flag is set, and the swingback timer TY is set to "0" (step C).
40, C41). When it is determined that the acceleration G stored in the memory Mg is left (turn right), the front and rear right solenoid valves 23 and 27 are turned off, and the acceleration G is right (turn left). When the determination is made, the front and rear left solenoid valves 22 and 26 are turned off, and the air spring chambers 3 of the left and right suspension units communicate with each other (steps C42 to C44). As a result, the communication time between the respective air spring chambers 3 of the left and right suspension units is advanced, so that the pressure difference between the left and right air spring chambers 3 generated by the roll control does not increase the swingback of the vehicle body. Is done. Further, the front and rear air supply valves 20 and 24 are turned off, the exhaust direction switching valves 28 and 32 are turned off, the differential pressure holding flag is reset, the control level CL is set to 0, and the control flag is also reset. Then, the process returns to the step C1 (steps C45 to C49). If “YES” is determined in steps C37 and C38 and the process proceeds to step C39, since the swingback flag has already been set, the process proceeds to the swingback routine from step C50.

That is, the count value of the timer TY is incremented,
It is determined whether the count value of the timer TY is 0.25 seconds or more (steps C50 and C51). If it is determined “NO” in step C51, the above-described step C1 is performed.
When the timer TY is incremented through the subsequent processing and the count value of the timer TY exceeds 0.25 seconds, it is determined again whether the count value of the timer TY is 2.25 seconds or more (step C52). Therefore, when the count value of the timer TY is 0.25 seconds or more and smaller than 2.25, in the above-mentioned step C52,
The determination is "NO", and the flow proceeds to the processing after step 53.
In the determination in step C53, it is determined whether the acceleration G is in the left-right direction, and if it is determined that the direction of the memory Mg is right, the front and rear left solenoid valves 22, 26 are determined.
Is turned on, and when it is determined that the acceleration G in the left-right direction is left, the front and rear right solenoid valves 23, 2
7 is turned on. Further, the exhaust direction switching valve 28,
32 is turned on (steps C53 to C56). The spring constant of the front and rear suspension units can be increased by the processing in step C54.
In this manner, when the handle angular velocity number 16 is equal to or greater than the threshold value in FIG.
When the pressure becomes 0.6 g / sec or more, the left and right air spring chambers 3 are immediately communicated with each other, whereby the pressure difference between the left and right air spring chambers 3 generated by the roll control causes the body to swing back. It is prevented from increasing. Further, 0.25 seconds later, the left and right communication is closed for 2 seconds, so that when the vehicle body returns to the neutral state, the spring constant of each air spring chamber 3 increases and the roll of the vehicle body to the opposite side is reduced. And
After 2.25 seconds, “YES” in the above step C52.
Is determined, the swingback flag is reset, and the swingback processing ends. (Step C57). Hereinafter, the processing after step C42 is performed, and then the processing after step C1 is performed.

[0044]

(Equation 16)

[Equation 17] By the way, in step C37 or C38, "N
If it is determined to be "O", that is, if the steering wheel is slowly returned during the transition from turning to straight running, or if the temporal change number 18 of the acceleration G is small, the above-described control regarding the swing back is not suitable. Therefore, the following control is performed. That is, first, it is determined whether or not the swing-back flag is set (step C58), and if it is set, the process proceeds to the above-described step C50 and thereafter. This may actually be the case in the process of control relating to swingback.

[0045]

(Equation 18) On the other hand, since the swing-back flag is not set when the vehicle slowly shifts from the turning traveling to the straight traveling, the determination is "NO" in step C58, and the lateral acceleration G is at the dead zone level. Or in other words, “G ≦
G0 "(step C59). If the level is the dead zone level, it is determined whether the differential pressure is being held (step C60). If the differential pressure is being held, step C61 is performed.
Proceeding to the subsequent processing, the processing shifts to processing for gradually releasing the differential pressure between the left and right air spring chambers 3 by duty control.

Hereinafter, the processing of the duty control routine performed after step C61 will be described. First, it is determined whether the duty control count Tn is 3 or more (step C61). And the duty timer Td is Tmn
It is determined whether or not this is the case (step C62). Here, initially, since both TD and Tmn are “0”, “YE
S ”is determined. However, "NO" in step C62.
In the case of, the duty timer Td is incremented (step C63), and the processing for making the damping force of the shock absorber 1 one step harder is performed in steps C64 to C67. Although not shown, between steps C63 and C64, after the damping force of the shock absorber 1 is set in step C66 or C67 in one control for releasing the pressure difference between the left and right air spring chambers 3, the step is performed. There is provided a step of returning when the process of C63 is completed.

By the way, the determination in step C62 is "YES", that is, the duty timer Td
Is equal to Tmn, the process proceeds to a process after step C68, and a process of intermittently communicating between the left and right air spring chambers 3 is started. First, the direction Mg of the lateral acceleration G stored in step C31 is determined (step C68).
When the direction of the acceleration G in the left-right direction is the left side,
In step C69, it is determined whether the front and rear right solenoid valves 23, 27 are turned off. At first, these valves 23 and 27 are on (that is,
It is in a differential pressure state), so it is turned off in step C71. Thereby, the left and right air spring chambers 3 communicate with each other, and the air in the left air spring chamber 3 flows into the right air spring chamber 3. Further, in steps C72 and C73, the duty counter Tn is incremented, and the duty timer Tmn is set to "Tmn +
Tm "(Tn is a constant of about 0.1 second) is set, and the process returns to the step C1. After Tm seconds, "YES" is determined in step C62, and "left" is determined in C68, and the process reaches C69. In step C69, since the right solenoid valves 23 and 27 have already been turned off, it is determined to be "YES", and the routine proceeds to step C70, where the solenoid valve 2 is turned off.
3, 27 are turned on. Next, the routine proceeds to step C73, where "Tmn + Tm" is set in the duty timer Tmn. Thus, the solenoid valves 23 and 27 are set to T
If the process of opening for m seconds is performed three times, that is, if the communication between the left and right air spring chambers 3 is performed three times, “YES” is determined in the step C61. Then, Steps C74 and C74
At 75, C76 and C82, the front and rear exhaust direction switching valves 28 and 32 are turned off, the differential pressure holding flag is reset, the control level CL is set to 0, and the series duty control is ended.

By the way, in the determination of the above step C68,
If it is determined to be "right side", steps C69 to C71
Is performed on the left solenoid valves 22 and 26. When this process is also performed three times, the process proceeds to the process of step C74, and a series of processes is ended.

As described above, when the steering wheel is returned slowly or the temporal change G of the acceleration G is small when shifting from turning to straight traveling, the left and right air spring chambers are controlled by the above-described series of duty control. Since the differential pressure between the air spring chambers 3 is gradually eliminated, the inside of each air spring chamber 3 can return to the state before control very smoothly.

Next, with reference to FIGS. 20 and 21, the air supply / exhaust correction routine in step A3 will be described in detail. First, the RMU input from the road surface μ estimation unit 55
The value (road surface μ value) is read (step D1). And
The internal pressure of the rear suspension units RS1 and RS2 is detected based on a signal from the pressure sensor 45 (step D2). Next, the control level CL is compared with the control level TCG determined from the G sensor map in FIG. 11 or the control level TCH determined from one of the steering wheel angular velocity-vehicle speed maps in FIGS. 8 to 10 (step D3). D4) If a control level TCG or TCH larger than the control level CL is obtained, it is stored in the control level CL (steps D8 and D17). Note that the control level register CL is set to “0” as an initial value.

On the other hand, if it is determined that both the control levels TCG and TCH are lower than the control level CL, the supply / exhaust flag SEF is reset, the damping force switching position is reset, and the control levels TCG and TCH are reset. Is set to the dead zone level "1" (steps D5 to D).
7).

By the way, after the control level TCG is set to the control level CL in step D8, "TCH≤
If "1" (that is, if the lateral acceleration acting on the vehicle body is small), "3" is set as the air supply coefficient Ks (step D10).

On the other hand, when "TCH>1" (that is,
When the lateral acceleration acting on the vehicle body is small), step D
If “RMU ≧ 0.4” is determined in the determination of 17a, “1” is set to the air supply coefficient Ks (step D1).
1). In step D17, the control level C
When the control level TCH is set to L, step D1
When it is determined that “RMU ≧ 0.4” in the determination of 7a, “1” is set to the air supply coefficient Ks (step D1).
1) If it is determined that “RMU <0.4” in the determination of step D17a, “3” is set to the air supply coefficient Ks (step D17b).

As described above, the air supply coefficient Ks is set to "3" at the time of the roll control on the low .mu. Road where "RMU <0.4", so that the determination in step C14 in FIG. It is determined as “YES”. Accordingly, the air supply flow control valve 19 is kept off, and air supply is performed slowly through the orifice o. Further, since the air supply time TCS is tripled due to the influence of the "KS" term as shown in step S23 described later, the overall air supply amount is the same as in the case of Ks = 1. That is, the coefficient of friction (RMU) is
When the value is smaller than (0.4), the supply air flow control valve 1
9 remains off and air supply is via orifice o
And slows down the rate of change of support
You. Therefore, since the roll control on the low μ road is performed slowly and slowly, the vehicle body is prevented from skidding due to abrupt load movement.

Then, the above-mentioned step D10 or D1
After 1 the supply / exhaust flag SEF indicating that the supply / exhaust control needs to be performed is set (step D12), and FIG.
Supply and exhaust are performed by the roll control routine of FIG. Then, it is determined whether the rough road determination set by the rough road determination routine (step A1) is set (step D13). If it is determined in step D13 that the rough road determination is set, it is determined whether the control level TCG is "2" (step D1).
4) If the control level is "2", the supply / exhaust flag SEF is reset, and the dead zone level "1" is set as the control level TCG (steps D15 and D16). In other words, when the control level TCG is “2” at the time of determining a rough road, the roll control is performed during a 150 ms supply / exhaust time under normal conditions, but the supply / exhaust time is set to “0” and the roll control is performed. I can't. In other words, when a rough road is determined, such as when traveling on a rough road, a malfunction of the roll control on a rough road is prevented by increasing the dead zone width of the G sensor.

By the way, steps D7, D13, D
After the processing of D14 and D16 is completed, the basic time Tc of supply / exhaust according to the control levels TCH and TCG is obtained from the obtained control level TCH or TCG with reference to FIG. 12 or 13 (step D18). . Next, the pressure sensor 45 detects the rear suspension unit RS.
1, the internal pressure of RS2 (rear internal pressure) is detected, and the front internal pressure is estimated from the rear internal pressure by referring to a front internal pressure-rear internal pressure characteristic diagram (not shown). The front internal pressure-rear internal pressure characteristic diagram will be described in more detail as follows. In other words, when a general passenger car is occupied by one passenger in the front seat and two passengers in the rear seat, and compared with a passenger occupied by two passengers in the front seat and one passenger in the rear seat, it is strictly as shown in this characteristic diagram. Not be. However, it has been confirmed by an experiment that by creating a characteristic diagram that approximates each pattern in consideration of all riding patterns, a value close to the actual front internal pressure can be obtained from the rear internal pressure. Based on the front internal pressure estimated in this way and the rear internal pressure obtained from the pressure sensor 45, an air supply / exhaust air correction coefficient characteristic diagram (not shown) is referred to, and a front side and rear side air supply correction coefficient PS, a front side Then, the rear side air supply correction coefficient PE is obtained (step D19). In this characteristic diagram, when the internal pressure of the suspension is high, the air supply time requires a longer time to supply the same amount of air than when the internal pressure is low.
S is proportional to the internal pressure Po, and when the internal pressure of the suspension is high, the time required to exhaust the same amount of air is shorter than when the internal pressure is low. It is inversely proportional to PO.

Next, it is determined whether or not the compressor 16 (return pump) is stopped (step D20). If it is stopped, that is, if the pressure difference between the high-pressure reserve tank 15a and the low-pressure reserve tank 15b is large, ,
Since the supply and exhaust of the suspension has a large air flow rate even in a short time, the initial coefficient FK is set to 0.8 (step D2).
1). On the other hand, when the engine is not stopped, that is, when the pressure difference between the high-pressure reserve tank 15a and the low-pressure reserve tank 15b is small, the initial coefficient FK is set to 1 and the air supply / exhaust time is not corrected (step D22).

Next, the basic air supply time Tc already obtained is multiplied by the air supply correction coefficient PS, the air supply coefficient KS and the initial coefficient FK to obtain a corrected air supply time TCS (step D23). ). In addition, the exhaust gas correction coefficient PE and the initial coefficient FK are added to the already obtained basic time Tc of the exhaust gas.
Is multiplied to obtain a corrected exhaust time TCE (step D24). Note that the supply time TCS and the exhaust time TCE are respectively obtained because the front wheel side and the rear wheel side have different correction coefficients.

Next, referring to FIGS. 12 and 13, a damping force switching position corresponding to the control levels TCG and TCH is obtained.
The position is set to the damping force target value DST (step D25). Next, when the rough road determination is set, if the damping force target value DST is hard, it is changed to medium (steps D26 to D28). As a result, the ability of the wheels to follow the road surface when traveling on a rough road is improved.

Further, it is determined whether the RMU value (road surface μ value) is smaller than 0.4 (step D29). In this step D29, when it is determined that the road is a low μ road with an RMU value smaller than 0.4, if the damping force target value DST is hard, it is changed to medium (step D3).
0, D31).

On the other hand, if it is determined in step D30 that the target damping force value DST is not hard, it is determined whether the target damping force value DST is medium (step D32). If it is determined in step D32 that the target damping force value DST is medium, the target damping force value DST is changed to soft.

As described above, when the vehicle is traveling on a low μ road where the RMU value is smaller than 0.4, the target damping force DS
T is lowered by one step to secure tire grip. This enables a flexible turn.

As described above, the air supply is performed slowly on the low μ road where the RMU value is 0.4 or less.
As shown by the solid line, the occurrence of the lateral G with respect to the steering wheel angle can be increased. Further, when the steering wheel angle is steered as shown in FIG. 23, the occurrence of the lateral G and the occurrence of the yaw rate can be increased as shown by the solid line. In FIG. 23, the broken line shows the characteristics when the low μ road control is not performed as in the present application.

The present invention is not limited to the above embodiment, but can be applied to a hydraulic active citation.

[0065]

As described above in detail, according to the present invention, when turning on a low μ road, abrupt load movement is suppressed, so that the steering response and turning limit are improved while lowering the vehicle body load. A suspension control device for a vehicle, which can suppress the load on the vehicle, can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a vehicle suspension control device according to one embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a road surface μ estimating unit.

FIG. 3 is a diagram for explaining a principle of calculating a road surface μ.

FIG. 4 is a diagram showing a relationship between a cornering force and a side slip angle.

FIG. 5 is a diagram showing a driving and non-driving state of a three-way valve.

FIG. 6 is a diagram showing a drive state and a non-drive state of a solenoid valve.

FIG. 7 is a diagram showing a drive state and a non-drive state of an air supply flow control valve.

FIG. 8 is a vehicle speed-handle angular velocity map in the SOFT mode.

FIG. 9 is a vehicle speed-handle angular velocity map in the AUTO mode.

FIG. 10 is a vehicle speed in the SPORT mode--a steering wheel angular velocity map.

FIG. 11 is a G sensor map.

FIG. 12 is a diagram showing a relationship between a control level based on a vehicle speed-handle angular velocity map and supply / exhaust time.

FIG. 13 is a diagram showing a relationship between a control level and a supply / exhaust time based on a G sensor map.

FIG. 14 is a schematic flow chart showing the operation of one embodiment of the present invention.
Chart.

FIG. 15 is a part of a detailed flowchart of a roll control routine.

FIG. 16 is a part of a detailed flowchart of a roll control routine.

FIG. 17 is a part of a detailed flowchart of a roll control routine.

FIG. 18 is a part of a detailed flowchart of a roll control routine.

FIG. 19 is a part of a detailed flowchart of a roll control routine.

FIG. 20 is a part of a detailed flowchart of an air supply / exhaust correction routine;

FIG. 21 is a part of a detailed flowchart of a supply / exhaust correction routine;

FIG. 22 is a view showing a steering wheel angle-lateral G characteristic.

FIG. 23 shows lateral G and yaw during step steering of a steering wheel angle.
The figure which shows a late characteristic.

[Explanation of symbols]

15a: high pressure reserve tank, 15b: low pressure reserve tank, 19: supply air flow control valve, 22, 23, 26,
27 ... solenoid valve, 36 ... control unit, 36 ... control unit, 45 ... pressure sensor,
55 ... road surface μ estimation unit

Claims (1)

(57) [Claims] 1. A roll detecting means for detecting a cause of a roll on a vehicle body, left and right suspension units provided so that a supporting force on the vehicle body can be independently adjusted, and a roll on the vehicle body is suppressed. And a control means for changing the support force of the left and right suspension units by an amount corresponding to the detection output of the roll detection means, so as to detect a friction coefficient between a road surface and a tire. And a control means for reducing the speed of change in the suspension force of the suspension unit during roll suppression when the friction coefficient detected by the friction coefficient detection means is lower than a predetermined value. A suspension control device for a vehicle, characterized by being configured as described above.