JP2707500B2 - Vehicle suspension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an improvement of a vehicle suspension device that can select a control mode during roll control according to occupant's preference.

(Prior Art) A suspension unit having an air spring chamber is provided for each wheel, and air is supplied to the air spring chamber of the contraction side suspension unit during turning, and air is set from the air spring chamber of the extension side suspension unit. 2. Description of the Related Art There is known a vehicle suspension device that discharges an amount of a vehicle to reduce a roll of a vehicle body generated during a turn. Further, for example, three control modes of software, auto, and sports can be selected so that the roll control feeling can be changed according to the occupant's preference, and the air supply and exhaust amount can be changed according to each control mode. A suspension device for a vehicle in which the damping force of the shock absorber is changed in accordance with each control mode in addition to the change is considered.

(Problems to be Solved by the Invention) However, in such a vehicle suspension device, for example, when the sport mode is set, the damping force of the shock absorber is fixed to hard, so that it is harder than necessary during straight running. There is a problem that it becomes a ride comfort.

The present invention has been made in view of the above points, and an object of the present invention is to provide a vehicle suspension device in which a roll control mode can be selected according to the occupant's preference. An object of the present invention is to provide a vehicle suspension device that can set a lower damping force during traveling.

[Structure of the Invention] (Means and Action for Solving the Problems) A fluid spring chamber provided for each of the left and right wheels and interposed between the wheel and the vehicle body, and a supply means for each of the fluid spring chambers is provided. A fluid supply means for supplying fluid through the fluid supply means, a fluid discharge means for discharging fluid from each of the fluid spring chambers via a discharge valve means, and a fluid supply means provided for each wheel between the wheel and the vehicle body. And a damping force switching type shock absorber that can select the damping force from soft to hard multi-stage damping force mode.
A roll detecting means for detecting a roll of the vehicle body, and when the roll detecting means detects that the roll of the vehicle body occurs at a set value or more, a required amount of fluid is supplied to a fluid spring chamber on the contracting side in the roll direction to expand the roll. And a roll control means for opening and closing the required supply valve means and the required discharge valve means to discharge a required amount of fluid from the fluid spring chamber on the side, and detects lateral acceleration acting on the vehicle body. An acceleration detecting unit, wherein the roll control unit is configured to detect the shock absorber when the acceleration detected by the acceleration detecting unit does not exceed a predetermined acceleration in a dead zone where the roll detecting unit does not detect a roll equal to or greater than the set value. The damping force is controlled to be switched from the selected damping force mode to a softer damping force mode, and the load detected by the acceleration detecting means is controlled. When the degree exceeds the predetermined acceleration, the damping force of the shock absorber is controlled to be switched from the current damping force mode to a hard damping force mode in a very short time (Embodiment). One embodiment of the present invention will be described. FIG. 1 is a block diagram showing a vehicle suspension device. In the figure, 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. Since these suspension units FS1, FS2, RS1, and RS2 have the same structure as each other, the suspension units FS1, FS2, RS1, and RS2 have the same structure, except for the case where the front and rear wheels or the left and right wheels are separately described. Will be described using the symbol S.

The suspension unit S has a shock absorber 1. The shock absorber 1 includes a cylinder mounted on the wheel side, a piston rod slidably fitted in the cylinder, and a piston rod 2 having an upper end supported on the vehicle body side. Further, the suspension unit S has an air spring chamber 3 having a function of adjusting the vehicle height 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 the vehicle height is increased by supplying and discharging air to and from the air spring chamber 3 through a passage 2 a provided in the piston rod 2. Or it can be lowered.

In the piston rod 2, a control rod 5 having a valve 5a for adjusting a damping force is provided at a lower end. The control rod 5 is a piston rod 2
The valve 5a is rotated by an actuator 6 mounted on the upper end of the valve 5a. By the rotation of the valve 5a, the damping force of the suspension unit is set to four levels of hard (hard), medium (middle), soft (soft), and medium / soft which is intermediate between the medium and the soft.

The compressor 11 compresses the air taken from the air cleaner 12 and sends 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 ecleaner 12 and supplies the compressed air to the dryer 13, the compressed air dried by the silica gel or the like in the dryer 13 is supplied to the high-pressure reserve tank 15a.
It will be stored in. The compressor 16 has a suction port connected to the low-pressure reserve tank 15b and a discharge port connected to the high-pressure reserve tank 15a. Reference numeral 18 denotes a low-pressure switch that is turned on when the pressure in the low-pressure reserve tank 15b is equal to or higher than a first set value (atmospheric pressure), and is turned off when the pressure is larger than the set value. When the compressor 16 outputs an off signal of the low 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 arrow in FIG. That is, the compressed air in the high-pressure reserve tank 15a is sent to the suspension units FS1 and FS2 via the flow rate switching valve 19, the front air supply solenoid valve 20, the check valve 21, the front left solenoid valve 22, and the front right solenoid valve 23. Be paid. Also,
Similarly, the compressed air in the high-pressure reserve tank 15a passes through the flow rate switching valve 19, the rear air supply solenoid valve 24, the check valve 25, the rear left solenoid valve 26, the rear right solenoid valve 26, and the rear right solenoid valve 27. Supplied to suspension units RS1 and RS2.

On the other hand, the exhaust from each suspension unit S
This is performed as indicated by the dashed arrow in the figure. That is, the compressed air in the suspension units FS1 and FS2 is supplied to the low-pressure reserve tank 15 through the exhaust switching valve 28 composed of the solenoid valves 22 and 23 and the three-way valve. Switching valve 28, check valve 2
9, the air may be exhausted to the atmosphere via the dryer 13, the exhaust solenoid valve 31, the check valve 46, and the air cleaner 12. Similarly, suspension units RS1, RS2
The compressed air is supplied to the low-pressure reserve tank 15b through the solenoid valves 26 and 27 and the exhaust switching valve 32, and the compressed air is supplied to the solenoid valves 26 and 27 and the exhaust switching valve 3.
2. In some cases, the air is discharged to the atmosphere via the check valve 33, the dryer 13, the exhaust solenoid valve 31, the check valve 46, and the air cleaner 12. Check valve
A passage provided with a small-diameter throttle L is provided between 29 and 33 and the dryer 13 in comparison with a passage that directly communicates the exhaust switching valves 28 and 32 and the low-pressure reserve tank 15b.

The above-described solenoid valves 22, 23, 26, 27, 28
And 32 are ON as shown in FIGS. 2 (A) and (B).
In the (energized state), the flow of air as indicated by an arrow A is allowed, and when OFF (non-energized), the flow of air as indicated by an arrow B is permitted. As shown in FIGS. 3 (A) and (B), the air supply solenoid valves 20, 24 and the exhaust solenoid valve 31 are ON (energized state) to allow air to flow as indicated by arrow C and OFF.
Prohibit the flow of air in the (non-energized state). When the flow switching valve 19 is in the off state (non-energized), air flows through the orifice o as shown in FIG. 4A, 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.

34F is the lower arm 35 of the front right suspension of the vehicle
A front vehicle height sensor mounted between the vehicle and the vehicle body for detecting the front vehicle height, and a rear vehicle height sensor 34R mounted between the lateral rod 37 of the rear left suspension of the vehicle and the vehicle body to detect the rear vehicle height It is. The signals detected by the two vehicle height sensors 34F and 34R respectively are a control unit 36 having an input circuit, an output circuit, a memory, and a microcomputer.
Supplied to

38 is a vehicle speed sensor built in the speedometer,
The detected vehicle speed signal is supplied to the control unit 36. Reference numeral 39 denotes an acceleration sensor for detecting acceleration acting on the vehicle body.
Supply to 30 is soft roll control mode (SOFT),
Roll control mode selection switch to select between Auto (AUTO) and Sports (SPORTS), 40 is the steering wheel 41
Is a steering sensor that detects the rotational speed of the steering wheel, that is, the steering angular speed.

An accelerator opening sensor 42 detects the depression angle of an accelerator pedal (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. Reference numeral 43 denotes a compressor relay for driving the compressor 11, and the compressor relay 43 is controlled by a control signal from the control unit. Reference numeral 44 denotes a pressure switch that is turned on when the pressure in the high-pressure reserve tank 15a becomes equal to or lower than a ^second set value (for example, 7.5 kg / cm ² ). The signal of the pressure switch 44 is supplied to the control unit 36. Then, when the pressure in the high-pressure reserve tank 15a becomes equal to or less than the second set value and the pressure switch 18 is on even when the pressure switch 44 is on, It is configured to prohibit the driving of the eleventh. 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 rear suspension units RS1 and RS2.

Each of the solenoid valves 19, 20, 22, 23, 2
The control of 4, 26, 27, 28, 31 and 32 is performed by a control signal from the control unit 36.

Next, the operation of the embodiment of the present invention configured as described above will be described. Figure 11 shows the control unit 36
5 is a flowchart schematically showing a series of roll control performed in step (a). First, a so-called rough road determination process is performed in a rough road determination routine (step A1) as a rough road determination unit. In other words, 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 G sensor 39 is determined as the rough road determination.
The width of the dead zone is widened to reduce the malfunction of the roll control. 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, thereby preventing the vehicle body roll control during turning. doing. Further, 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 obtained by correction. Further, in the damping force switching routine (step A4) as the damping force switching means, the damping force of each suspension unit is hard (hard), medium (middle), soft (soft) and medium / soft (between medium and soft). Is set to the most appropriate one. The following steps
The processing of A1 to A4 will be described in detail.

First, referring to FIG. 12, a rough road determination routine (step
The detailed operation of A1) will be described. First, the front vehicle height Hf detected by the front vehicle height sensor 34F is read into the control unit 36 at predetermined time intervals (step B).
1). In the main routine shown in FIG.
It is assumed that various flags IT, A, B, UP, and DN described later are set to “0”. The flag IT is set to "1" when the rough road determination is started, and the flag A is set to "1" from the time when the front vehicle height Hf shifts from the decreasing state to the increasing state until the time when the front vehicle height Hf shifts to the decreasing state again. The flag B is set to “1” from the time when the front vehicle height Hf shifts from the increasing state to the decreasing state to the time when the front vehicle height Hf shifts to the increasing state again,
The flag UP is set to "1" when the front vehicle height Hf is decreasing, and the flag DN is set to "1" when the front vehicle height Hf is increasing.

First, in the first determination of step B2, the flag IT
Is “0”, it is determined as “NO”, and after the flag IT is set to “1”, the current front vehicle height Hf is stored in the register H.
A, and the timer Tc is reset (step B3
~ B5).

Then, the front vehicle height Hf is the control unit
If it is read to 36, “YES” is determined in step B2, and the timer Tc is incremented by the interval time INT (step B6). And the current front vehicle height
Whether Hf is smaller than the stored vehicle height HA (step B
7) Or, it is determined whether it is greater than the vehicle height HA (step B22), and the processing described later is performed according to the determination.
For example, if the front vehicle height signal Hf is input from time t0 as shown in FIG. 14, the front vehicle height Hf tends to increase, so it is determined that “HA <Hf” in step B22. Proceed to step B23. Since the flag UP is set to “0” in the initial setting,
DN = 1 ”and“ Flag B = 0 ”(step
B26, B27), the current front vehicle height Hf is stored in HA (step B13). Then, it is determined whether or not “A × B = 1”, that is, whether or not “A = B = 1” (step B14). This determination is made such that “A = B = 1” when the increasing tendency is reversed when the front vehicle height Hf increases or decreases. Since “A = B = 0” at this stage, “NO” is determined in the step B14.

Next, the process proceeds to step B16, where it is determined whether or not the timer Tc has counted for 2 seconds or more. At this point, since 2 seconds have not elapsed, the process proceeds to step B28. In the determination in step B28, it is determined whether the rough road determination is set. However, since it is not set, the process returns.

Thereafter, at the time t1, the front vehicle height Hf starts to decrease, so that “YES” is determined in the step B7, and the process proceeds to the determination in the step B8. Here, “flag DN = 1” is determined, but since the flag DN is set in step B26, “YES” is determined and “flag B = 1”,
“Flag DN = 0” is set (steps B9 and B10). Thereafter, as in the case of the time t0 described above, steps B13 and B1
Returned via 4, B16, B28. Then, as shown in FIG. 14, the front vehicle height Hf continues to fall from time t1 to time t2, but when it is determined to be “YES” again in step B7 and the determination of step B8 comes, the flag DN =
Since the flag A is 0, as shown in FIG.
UP = 1 is set (steps B11 and B12).

Thereafter, after time t2 in FIG. 14, when the front vehicle height Hf starts to increase, it is determined to be “YES” in step B22,
Proceeds to the determination of step B23, but here the flag is already up
Is set, the flag A = 1 is set, and the flag A is set.
UP is set to 0 (steps B24 and B25).

In this way, when the front vehicle height Hf rises and falls as shown in FIG. 14, the flag B is maintained between the time when the front vehicle height Hf shifts from the rising state to the falling state and the time when the front vehicle height Hf shifts to the rising state again. Is set to "1", and the flag A is set to "1" from the time when the front vehicle height Hf shifts from the falling state to the rising state until it shifts to the falling state again.

Then, after passing through step B13, the process proceeds to step B14. At this stage, since "A = 1" and "B = 1", "A × B = 1", and the process proceeds to step B15. The above-mentioned flags A and B both become “1” only when the increasing tendency of the front vehicle height Hf is reversed, and “A × B = 1” at each reversal. Therefore, in step B1, the counter NCNT is incremented by "+1". That is, the counter NCNT is incremented by “+1” by one increase / decrease of the front vehicle height Hf. The above processing is repeated until the count of the timer Tc exceeds 2 seconds.
If the time exceeds the second, the timer Tc is reset and it is determined whether the count value of NCNT is N or more (steps B16 to B1).
8). That is, when it is detected that the front vehicle height Hf has increased or decreased N times or more in two seconds, it is determined that the road is a rough road, NCNT = 0, rough road determination is set, and the delay timer T
After R = 0 (steps B19 to B21), the routine returns.

If "NO" is determined in step B16 or B18 and the rough road determination is set, the delay timer TR is incremented by the time INT, and the delay timer T
When R becomes larger than 4 seconds, the rough road determination is reset (steps B29 to B31). Thus, the rough road determination is performed four seconds after the last rough road determination is set, that is, step B1.
It will be reset two seconds after it is determined that the road is not a bad road ("NO") at 8.

As described above, in the rough road determination routine A1, every time the increase / decrease in the front vehicle height Hf is reversed, in step B15,
The counter NCNT is incremented by "+1". If the counter NCNT for two seconds is equal to or greater than N, a bad road determination indicating a bad road is set (step B20). And
This bad road determination is “NO” in step B18 (that is,
It is reset two seconds after it is determined that the road is not a bad road (step B31).

Next, the detailed operation of the roll control routine (step A2) will be described with reference to the flowchart of FIG. First, the vehicle speed V and G sensors detected by the vehicle speed sensor 38
The acceleration G in the left-right direction output from 39 and its differential value G ', the steering wheel angular velocity ΘH' detected by the steering sensor 40
Is read into the control unit 36 (step C
1). Then, it is determined that the steering wheel angular velocity ΔH ′ 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 × ΔH ′” is determined to be positive (step C5). That is, it is determined whether the acceleration G in the left-right direction and the steering wheel angular velocity ΘH ′ are in the same direction, and if it is determined to be “positive”, it is turned to the incision side; It means that the steering wheel is being steered. If “YES” is determined in step C5, V-Ｖ in FIGS. 5 to 7 is selected according to the user's preference.
The control level TCH corresponding to the vehicle speed and the steering wheel angular speed is determined by referring to any one of the H 'maps (step C6). In step C6, when the soft mode is selected as the roll control mode by the roll control selection switch 30, the map in FIG. 5 is used, and when the auto mode is selected as the roll control mode, the map shown in FIG. When the sports mode is selected as the roll control mode in the map of FIG. 6, the map of FIG. 7 is selected. Then, the control level TCH of each map
The supply / exhaust time as shown in FIG. The relationship among the steering wheel angular velocity ΔH ′, the vehicle speed V, the control level, the mode, the supply / exhaust time, and the damping force shown in FIGS. 5 to 7 and 9 is stored in the memory in the control unit 36. Then, the supply and exhaust time TCS and TCE for the front and rear wheels are corrected and calculated by a supply and exhaust correction routine described in detail later with reference to FIG. 16, and the supply and exhaust flag SEF is set (step C7). Next, it is determined whether or not the control flag is being set (step C8). Since the roll control has not been started yet, it is determined to be “NO” and the process proceeds to step C9. In step C9, it is determined whether the air supply flag SEF is set. If the supply / exhaust flag SEF is set in the above-described supply / exhaust correction routine (step C7), the control flag is set, and the supply / exhaust timer T is set to 0 (step C10,
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 switching valves 28 and 32 are turned off, and the air discharged from the front or rear is supplied to the low pressure reserve tank 15b.
To be discharged. This is because the exhaust switching valves 28 and 32 are on while the differential pressure is being held,
These exhaust switching valves provide additional air supply and exhaust control.
28 and 32 need to be turned off.

Next, in the air supply / exhaust gas correction routine of step C7, it is determined whether the air supply coefficient Ks = 3 has been set (step C14).
When the coefficient Ks is 1), the flow switching valve 19 is turned on, the large-diameter path D (FIG. 4) is opened, and the supply air flow is increased (step C15). That is, since Ks = 1 is the case where the control level TCH is determined from the vehicle speed-handle angular velocity map as shown in FIG. 17, the air flow rate is increased in order to perform rapid roll control.

Next, the front and rear supply valves 20, 24 are turned on (step C16). Then, the direction of the acceleration G in the left-right direction is determined by the control unit 36 (step 1).
7). 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, it is determined that the acceleration G is a right turn in the traveling direction, that is, a left turn. 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 the air spring chamber 3 of the left suspension unit is discharged to the low-pressure reserve tank 15b via the valves 22 and 26 which are in the ON state, and the air in each air spring chamber 3 of the right suspension unit is also discharged. Air is supplied from the high-pressure reserve tank 15a via the supply valves 23 and 27 that are in the ON state, respectively.

On the other hand, if it is determined that the acceleration G is to the left (turn right), the front and rear right solenoid valves 23 and 27 are turned on (step C19). As a result, the air in each air spring chamber 3 of the right suspension unit is supplied to the low-pressure reserve tank 15b via the valves 23 and 27 which are in the ON state.
Into the air spring chamber 3 of the suspension unit on the left side.
Air is supplied from the high-pressure reserve tank 15a via the valves 0, 24 and the valves 22, 26 in the off state.

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. Until the count value of the timer T becomes equal to or more than the air supply time TCS or the count value of the timer T becomes equal to or more than TCE, a roll for supplying and exhausting air from each air spring chamber of the suspension unit according to the left and right G direction. Control is continued. By the way, when the count value of the timer T becomes equal to or longer than the air supply time TCS, "YES" is determined in the step C26, and the flow rate switching valve 19
Is turned off, the air supply solenoid valves 20, 24 are turned off, and the air supply operation is stopped (steps C27, C28). 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, "YE
Is determined to be "S", the exhaust 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. And the acceleration G in the left-right direction
Is stored in the memory Mg, and if “timer T ≧ TCS”, the control flag is reset, the roll control is stopped, and the state is maintained (steps C32 and C3).
3). In this way, the roll generated on the vehicle body at the turning temple is suppressed. The above processing has been described for the case where the steering wheel is suddenly steered. However, even when “ΘH ′ ≦ 30 deg / sec”, if “G × G ′” is positive (step C3
4), the control level TCG is determined with reference to the G sensor map in FIG. 8, and the same initial operation as when TCH is determined is performed to perform the roll control. In FIG. 8, V1
Is set at 30 km / h and V2 is set at 130 km / h. The supply / exhaust time and damping force corresponding to the control level TCG are obtained from FIG. 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. 8 and 10 is stored in the memory in the control unit 36. As is apparent from FIGS. 8 and 10, the supply / exhaust time finally obtained from the G sensor map also differs depending on the mode selected by the control switch 30. Although there is no storage of the soft mode in FIG. 10, when the soft mode is selected, G
This means that the control level is always zero in the sensor map. As will be described in detail later in the description of the supply / exhaust time correction routine C7, in this apparatus, the supply / exhaust time on the front wheel side and the supply / exhaust time on the rear wheel side are set to be different. Therefore, the counting of the supply / exhaust time and the supply / exhaust control based on the count are performed independently on the front wheel side and the rear wheel side.

By the way, when “G × G ′” is negative, that is, when the steering wheel is on the return side, “N
O ", the map of FIG. 6 is referred to (step C36), the threshold value ΘHM 'is obtained, and it is determined whether or not the return steering wheel angular velocity ΘH' ≧ ΘHM '(step C37). ). If “YES” is determined in step C37, the temporal change G ′ of the acceleration G in the left-right direction is 0.6 / sec.
It is determined whether this is the case (step C38). Here, when it is determined “YES” in the above steps 37 and C38, that is, when shifting from turning to straight running, the steering wheel is suddenly returned toward the neutral position and the temporal change G ′ of the acceleration G is changed. If it is larger, the vehicle body passes through the neutral state and rolls to the opposite side, that is, so-called backlash occurs. To prevent this, the processing after step C39 is performed.

In step C39, the control level TCH is obtained from the steering wheel angular velocity ΘH 'on the return side of the steering wheel 41 and the vehicle speed V with reference to any of the maps shown in FIGS. 5 to 7 corresponding to the mode at that time. A damping force target value is obtained from the control level TCH with reference to the relationship shown in FIG. 9 and set as the damping force target value DST. Next, the process proceeds to the swingback reverse control routine of step C40.

In the swing-back reverse control routine, as shown in FIG. 16, first, it is determined in step E1 whether the swing-back flag is set. Here, when the procedure first arrives at step E1, the swing-back flag is not set, so that it is determined as "NO", the swing-back flag is set, and the swing-back timer TY is set to "0" (step S1). E2, E3). Next, in step E4, it is determined whether or not the sports mode is set. If "NO", the process proceeds to step E5. If it is determined that the acceleration G stored in the memory Mg is left (turn right), the front And the rear right solenoid valves 23 and 27 are turned off. On the other hand, if it is determined that the acceleration G is right (turn left), the front and rear left solenoid valves 22, 2
6 is turned off, and the air spring chambers 3 of the left and right suspension units communicate with each other (steps E6 and E7). Thereby, the air 3 spring chambers 3 of the left and right suspension units are communicated with each other, and the pressure difference between the left and right air spring chambers 3 caused by the roll control is prevented from increasing the unwinding of the vehicle body. . Further, the front and rear air supply valves 20, 24 are turned off, the exhaust switching valves 28, 32 are turned off, the differential pressure holding flag is reset, the control level CL is set to 0, the control flag is reset, and the return is performed. Return to (Steps E8 to E12).

If “YES” in the step E4, the process proceeds to a step E13 to determine whether or not the pressure flag PFLG is “0”. The pressure flag PFLG will be described in detail later, but when the pressure in the low-pressure reserve tank 15b is sufficiently low, "0"
Otherwise, it is "1". In this step E13, if "NO", the process proceeds to the above-mentioned step E5, and if "YES", the process proceeds to a step E14. This step
At E14, the reverse control flag RVC is set to "1", and if the differential pressure is being held, the exhaust switching valves 28, 32 are turned off (steps E15, E16). Further, the flow switching valve 19 is turned on, and the air supply valves 20 and 24 are turned on (steps E17 and E17).
18). Subsequently, if the direction of the acceleration G is on the left side, the left control valves 22 and 26 are turned on, and if the direction of the acceleration G is on the right side, the right control valves 23 and 27 are turned on (steps E19 to E21) and the roll control in the opposite direction is performed. Is started, the process proceeds to Step E10.

On the other hand, if "YES" in the step E1, that is, if the swingback flag is set, the count value of the timer TY is incremented, and it is determined whether the count value of the tire TY is 0.3 seconds or more (steps E22 and E23). ). If “NO” in the step E23, the process returns to the return, and the timer TY is set to 0.3
If the time is equal to or longer than seconds, it is determined whether the differential pressure is being held (step E24). Thus, air supply and exhaust are performed for 0.3 seconds as roll control in the reverse direction. In this step E24, since the differential pressure is not being held at first, the result is "NO", and the step E25
To determine whether the reverse control flag RVC is "1".
If the roll control in the reverse direction has been started via step E14 before reaching step E25, the result is "YES" in step E25, and the reverse control flag RVC is reset to "0". The air supply valves 20, 24 are turned off, and the flow switching valve 19 is turned off (step E26).
~ E28).

Next, if the direction of G is right, the left control valve 22, 26
Is turned on and the right control valves 23 and 27 are turned off. If the direction of G is right, the left control valves 22 and 26 are turned off and the right control valves 23 and 27 are turned on. The switching valves 28 and 32 are turned on and the differential pressure holding flag is set (steps E29 to E35), thereby starting the differential pressure holding state in which the roll control in the reverse direction is performed.

Then, "YES" is given in the step E24, and the step E26
Judge whether the count value of the timer TY is 2.30 seconds or more.
If the time is less than 2.30 seconds, the process returns to the return. If the time is 2.30 seconds or more, the swingback flag is reset in step E37.
Next, if the pressure switch 18 that opens and closes according to the pressure in the low-pressure reserve tank 15b is on (the pressure is higher than the set value), the pressure flag is set (PFLG = 1), and off (the pressure is lower than the set value). ), Reset the pressure flag (PFLG = 0) (steps E38 to E40), and
Proceed to E5. In other words, the differential pressure holding state in which steps E27 to E35 have been started is determined when the timer TY counts 2.3 seconds.
It is canceled by the processing of E5 to E12.

As described above, when the return-side steering angular velocity ΔH ′ is equal to or greater than the threshold value in FIG. 6 and the temporal change G ′ of the return-side lateral acceleration G is equal to or greater than 0.6 g / sec, first, in Step C3
In step 9, a hard damping force target value DST based on the steering angular velocity ΘH 'at that time is set, and then, in the swingback reverse control routine shown in FIG. 16, the sports mode is set and the low pressure reserve tank 15b is set. Only when the pressure is sufficiently low, the left and right air spring chambers 3, 3 are communicated after the above-described reverse control is performed, and otherwise, the left and right air spring chambers 3, 3 are immediately communicated. It is.

By the way, when it is determined to be “NO” in the above step C37 or C38, that is, when the steering wheel is slowly returned when turning from turning to straight running or when the temporal change G ′ of the acceleration G is small, Since the control relating to the above-mentioned swingback is not suitable, the control described below 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-mentioned step C40 and thereafter.

On the other hand, when slowly shifting from the above-mentioned turning traveling to straight traveling, since the swingback flag is not set, it is determined to be "NO" in step C58, and then the acceleration G in the left-right direction is at the dead zone level. Or “G ≦ G0”
(For example, G0 is set to 0.1 g) (step C59). If the level is the dead zone level, it is determined whether the differential pressure is being held (step C60). Proceeding to the processing after step C61, the processing moves 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).
Then, it is determined whether or not the duty timer TD is equal to or longer than Tmn (step C62). Here, initially, both TD and Tmn are “0”, so that the determination is “NO”. But,
If "NO" in the step C62, the duty timer TD is incremented. Next, it is determined whether the return flag RET is set, and if "NO", the return flag is set (RET = 1) (steps C64 and C65). Further, in step C66, it is determined whether the current damping force is MEDIUM (DDST = MED). If “YES”, if the rough road determination is being performed (the rough road determination is set), the target damping force DST is set to MEDIUM. Is set, and HARD is set to the target damping force DST if the rough road determination is not underway (steps C67 to C69). In the above step C66, "N
If it is "O", if the current damping force (DDST) is SOFT, MEDIUM is set to the target damping force DST, and if not, HARD is set to the target damping force DST (steps C70 to C72).

In this manner, when the steering wheel is slowly returned or the temporal change G 'of the acceleration G is small when the vehicle shifts from turning to straight traveling, the occupant does not feel uncomfortable with the return control by the duty control described later. Thus, the target damping force is set to be one step harder. However, when the current damping force DDST is MEDIUM (that is, the damping force during the holding of the differential pressure by the roll control is MEDIUM), the target damping force DST remains at MEDIUM only during rough road determination. This is because if the damping force is too hard during the determination of a rough road, the grounding properties of the wheels are impaired. By the way, during bad road determination such as when driving on a gravel road, the occupants do not feel uncomfortable and improve the ride comfort even if the shock absorber damping force is set low when returning to roll control because the behavior of the vehicle body is large. Can be done.

By the way, if "YES" is determined in the determination in step C62, that is, if the duty timer TD reaches Tmn, the process proceeds to the processes in and after step C73, and the process of intermittently communicating between the left and right air spring chambers 3 is started. You. First, the above steps
The direction Mg of the lateral acceleration G stored in C31 is determined (step C73). If the direction of the acceleration G in the left-right direction is the left side, it is determined in step C74 whether the front and rear right solenoid valves 23, 27 are turned off. Initially, these valves 23 and 27 are on (that is, in a differential pressure state), so they are turned off in step C76. 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 C77 and C78, the duty counter Tn is incremented, and the duty timer Tmn is set to “Tmn + T
m) (Tm is a constant of about 0.1 second) is set, and the process returns to the step C1. After Tm seconds, “Y
ES ”,“ left ”is determined in step C73, and the process proceeds to step C74. In step C74, since the right solenoid valves 23 and 27 have already been turned off, it is determined to be "YES", and step C74 is executed.
Proceeding to 75, the solenoid valves 23, 27 are turned on. Next, the routine proceeds to step C78, where the duty timer Tmn is set to "Tmn
+ Tm ”is set. In this way, when the process of opening the solenoid valves 23 and 27 for Tm seconds and every Tm seconds is executed three times, “YES” is determined in the step C61. Then, in step C79, the return flag is reset (RET = 0), and in steps C80, C81, C82, the front and rear exhaust switching valves 28, 32 are turned off, the differential pressure holding flag is reset, and the control level CL = 0. Then, a series of duty control is ended.

By the way, if it is determined in the above step C73 that it is “right side”, the same processing as steps C74 to C76 is performed on the left solenoid valves 22 and 26. When this process is also performed three times, the process proceeds to the processes after step C79, and a series of processes is ended.

As described above, when the steering wheel is slowly returned when turning from the turning state to the straight traveling state or when the temporal change G 'of the acceleration G is small, the above-described series of duty control controls the distance between the left and right air spring chambers 3. Is gradually eliminated, so that the inside of each air spring chamber 3 can be returned to the state before control very smoothly.

Next, the above-described supply / exhaust correction routine in step A3 will be described in detail with reference to FIG. This correction routine corresponds to step C7 in FIG. 15 (a). First, the internal pressure of the rear suspension units RS1 and RS2 is detected based on a signal from the pressure sensor 45 (step D).
2). Next, the control level CL is compared with the control level TCG determined from the G sensor map in FIG. 8 or the control level TCH determined from one of the steering wheel angular velocity-vehicle speed maps in FIGS. (Steps D3 and D4) If a control level TCG or TCH higher than the control level CL is determined, 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 either the control level TCG or TCH is smaller than the control level CL, the air supply / exhaust flag SEF is reset, the damping force switching position is reset, and the control levels TCG and TCH fall within the dead zone level. "1"
Is set (steps D5 to D7).

By the way, after the control level TCG is set to the control level CL in step D8, if "TCH≤1" (that is, if the lateral acceleration acting on the vehicle body is small), the air supply coefficient Ks is set to "3". Is set (step D10). On the other hand, when "TCH>1" (that is, when the lateral acceleration acting on the vehicle body is large), "1" is set to the air supply coefficient Ks (step D11). When the control level TCH is set to the control level CL in step D17, "1" is set to the air supply coefficient Ks (step D1).
1).

Then, a supply / exhaust flag SEF indicating that the supply / exhaust control needs to be performed after step D10 or D11 is set (step D12), and supply / exhaust is performed by the roll control routine shown in FIG. Then, it is determined whether the rough road determination set by the rough road determination routine of FIG. 12 is set (step D13). In this step D13, when it is determined that the rough road determination is set, it is determined whether the control level TCG is "2" (step D14), and when the control level TCG is "2", The supply / exhaust flag SEF is reset, and the dead zone level “1” is set to the control level TCG (steps D15 and D16). That is, as shown in FIG. 13, the control level T
When the CG is “2”, the roll control is performed during the supply / exhaust time of 150 ms in normal times, but the supply / exhaust time is “0”.
And roll control is not performed. In other words, when a rough road is determined, such as when driving on a rough road, a malfunction of the roll control on a rough road is prevented by widening the dead zone of the G sensor.

By the way, after the processing of the steps D7, D13, D14, D16 is completed, the control levels TCH, TCG are obtained by referring to FIG. 9 or FIG.
The basic time TC of supply and exhaust according to the time is obtained (step D).
18). Next, the internal pressure (rear internal pressure) of the rear suspension units RS1 and RS2 is detected by the pressure sensor 45, and the front internal pressure is estimated from the rear internal pressure by referring to the front internal pressure-rear internal pressure characteristic diagram in FIG. The front internal pressure-rear internal pressure characteristic diagram will be described in more detail as follows. That is, when compared with a general passenger car in which two passengers are in the front seat and one passenger is in the rear seat, the characteristics are not exactly as shown in this characteristic diagram. However, it has been experimentally confirmed that by creating a characteristic diagram that approximates the name pattern in consideration of all riding patterns, a value close to the actual front internal pressure can be obtained from the rear internal pressure. Also, in the characteristic diagram of FIG. 18, three characteristics of a high vehicle height, a normal vehicle height, and a low vehicle height are shown. These are the rear internal pressure at the high vehicle height, the normal vehicle height, and the low vehicle height, respectively. This is because the relationship between the pressure and the front internal pressure is different. As a matter of course, a characteristic diagram suitable for the vehicle height at that time is used. Based on the front internal pressure estimated in this way and the rear internal pressure obtained from the pressure sensor 45, the air supply / exhaust air correction coefficient characteristic diagram in FIG. 19 is referred to, and the front and rear air supply correction coefficients Ps, A rear side exhaust correction coefficient PE is obtained (step D19). In FIG. 19, when the internal pressure of the suspension is high, the air supply time is required to supply the same amount of air as when the internal pressure is low. Since the time is required longer, the correction coefficient Ps is proportional to the internal pressure P0, and when the internal pressure of the suspension is high, the exhaust time is longer than when the internal pressure is lower than when the internal pressure is low. To be short, the correction coefficient PE is inversely proportional to the internal pressure P0.

Next, it is determined whether the compressor 16 (return pump) is stopped (step D20).
That is, the high-pressure reserve tank 15a and the low-pressure reserve tank 15b
Is large, the air flow rate is large even if the supply and exhaust of the suspension is short, so the initial coefficient FK =
It is set to 0.8 (step D21). On the other hand, when the vehicle 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 supply / exhaust time is not corrected (step D2).
2).

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 D2).
3). Further, the corrected exhaust time TCE is obtained by multiplying the exhaust gas basic time TC already obtained by the exhaust gas correction coefficient PE and the initial coefficient FK (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 FIG. 9 and FIG.
A damping force switching position according to G and TCH is obtained, and the position is set to the damping force target value DST (step D25). next,
If the rough road judgment is set, the damping force target value DS
If T is hard, it is changed to medium (steps D26 to D28: these steps correspond to damping force control means). As a result, the ability of the wheels to follow the road surface at the time of determining a rough road is improved.

By the way, in step C9 [FIG. 15 (a)]
If “NO”, the process proceeds to a dead zone damping force switching set routine of step C84. The operation of this set routine will be described with reference to FIG. First, in step F1, it is determined whether G in the left-right direction is larger than a set value G0 (for example, 0.1 g). If "NO" in the step F1, the initial flag is reset (DIN = 0) in a step F2, and if the auto mode is set, the target damping force DST is set to SOFT, and the sport mode is set. MEDIUM to the target damping force DST
Is set (steps F3 to F6).

On the other hand, if “YES” in the step F1, the process proceeds to a step F7 to determine whether or not the initial flag is set (DIN = 1). If "NO" in this step F7, the step
The initial flag is set (DIN = 1) at F8 and F9, and g
The holding timer is set (SDT = 0). If “YES” in the step F7, the g holding timer SDT is updated by adding the interval time INT in a step F10. Then
When the timer SDT counts for 0.3 seconds or more, if the auto mode is set, the target damping force
Set the OFT, and if the sports mode is set, set the target damping force DST to HARD (steps F11 to
F15). As described above, in the auto mode or the sports mode, even when the lateral acceleration G is in the dead zone of the supply / exhaust control, the damping force one step lower is set when the vehicle is going straight. Next, the damping force switching routine (step A4) will be described with reference to FIG. First, in step G1, it is determined whether the target damping force DST is greater than the basic damping force MDST of the manual set. In addition, this basic damping force MDST is SOFT, if the control mode is soft mode or auto mode.
If it is a sports mode, it is MEDIUM. Step G1 above
Is YES in step G2, it is determined whether the target damping force DST is equal to the current damping force DDST. If “NO” in this step G2, the holding timer TDS is set (TDS = 0) and the holding flag is set (DHLD) in steps G3 and G4.
= 1), a control signal is output so that the current damping force DDST becomes the target damping force DST. Thereby, the shock absorber 1 of each suspension unit S is switched to the target damping force DST by each actuator 6.

If “YES” in the step G2, the holding timer TDS is updated by adding the interval time INT in a step G6. Next, when the holding timer TDS counts for 1.0 second or more in step G7, it is determined in step G8 whether the swingback flag is set. If “NO” in this step G8, the holding flag is reset in steps G9 and G10 (DHLD =
0) and the holding timer is set (TDS = 0). Then, it is determined in step G11 whether the differential pressure is being held, and if "NO", it is determined in step G12 whether or not the sport mode is set. If not, the initial flag is set (DIN = 1). A determination is made (step G121). Here, if "DIN = 1", the process skips the next step G13 and returns, but "DIN = 0".
If so, in step G13, SOFT is set to the target damping force DST, and the flow proceeds to step G5. That is, the initial flag DIN = 1
In the case of, since the target damping force DST has been switched in steps F13 and F15 of the dead zone damping force switching set routine in FIG. 20, it is skipped so as not to update the switched target damping force DST. is there.

On the other hand, if "YES" in the step G11, the process proceeds to the step G1.
In step G14, it is determined whether the mode is the soft mode or in step G15 the mode is the auto mode if "NO" in step G14. "NO" in step G15 or "YE" in step G12
If "S", that is, if the sports mode is set, it is determined in step G16 whether the acceleration G in the left-right direction is larger than the set value G0. After setting MEDIUM to the target damping force DST in step G17, the process proceeds to step G5. "YES" in step G16
In step G18, HARD is set as the target damping force DST.

If “YES” in the step G14, that is, if the differential pressure is being held and the soft mode is set, it is determined in a step G19 whether the acceleration G in the left-right direction is larger than the set value G1. If “NO” in the step G19, the process proceeds to a step G5 after setting the target damping force DST to “SOFT” in a step G20.
If “YES” in the step G19, the target damping force DST is set to MEDIUM in a step G21.

If "YES" in step G15, that is, if the differential pressure is being held and the soft mode is set, it is determined in step G2 whether the acceleration G in the left-right direction is larger than the set value G2,
If "YES", HARD is set as the target damping force DST in step G23.

On the other hand, if “NO” in step G22,
At 24, it is determined whether the acceleration G in the left-right direction is greater than the set value G3, and if "YES", the target damping force DST is MED at step G25.
Set the IUM.

On the other hand, if “NO” in the step G24, the step G
At 26, it is determined whether the current damping force DDST is HARD, and if "YES", MEDIUM is set to the target damping force DST at step G27,
If "NO", the target damping force DST is set to SOFT in step G28, and the flow proceeds to step G5. The above set value G0 is 0.1
g and G1 are set at about 0.45 g, G2 at about 0.5 g, and G3 at about 0.3 g.

If "NO" in step G1, it is determined in step G29 whether the damping force is being held (DHLD = 1), and the flow proceeds to the count of the timer TDS in step G6. If “NO” in the step G29, the target damping force DST is added to the current damping force DDST.
Is set (step G30).

Thus, the target damping force DST is obtained by starting the roll control.
Is set to be larger than the basic damping force MDST, and the current damping force is switched to the target damping force, and then the damping force is controlled in the following manner if the swingback state does not occur. That is, in such a case, if the differential pressure is being held, if the magnitude of the acceleration G in the left-right direction is small, the damping force DDST is switched to a value of one-stage software. Are set so as to be suitable for each control mode. If the differential pressure is not being held, the target damping force DST is switched according to the magnitude of the lateral acceleration G when the sports mode is set, and when the mode other than the sports mode is set, as described above. The target damping force is set unconditionally to SOFT.

As a result, regardless of the damping force set manually, the damping force of the shock absorber 1 is appropriately increased when the suspension needs the most roll stiffness at the time of roll control. Is performed more effectively. Also. While the differential pressure is being held, the shock absorber 1 is switched to the damping force one step lower according to the lateral acceleration acting on the vehicle body at that time, so that the riding comfort during that time can be prevented from being extremely deteriorated. Further, after the differential pressure holding is released, the occupant automatically returns to the manually set occupant's desired damping force, so that it is possible to eliminate the trouble of the occupant returning to the damping force each time.

Although the above embodiment is a pneumatic suspension device, the present invention can be similarly applied to other types of suspension devices such as a hydropneumatic suspension device. Further, in the above embodiment, the maps shown in FIGS. 5 to 8 are used as the roll amount detecting means, but the present invention is configured to detect the roll amount from the vehicle speed and the steering angle, for example. It is also possible.

Further, in this embodiment, the supply / exhaust time is obtained from the detected roll amount, and the supply / exhaust control of each air spring chamber 3 is performed based on the supply / exhaust time. However, the present invention provides a pressure sensor for detecting the pressure in each fluid spring chamber, and supplies a fluid in each fluid spring chamber by a servo valve that performs feedback control based on a given control target and a detection value of the pressure sensor. The present invention can be similarly applied to a suspension device of a type configured to perform ejection.

[Effects of the Invention] As described above in detail, according to the present invention, in a vehicle suspension device capable of selecting a plurality of roll control modes in accordance with a user's preference, a mode in which the damping force of a shock absorber is the hardest is selected. If the acceleration in the left-right direction of the vehicle body does not exceed a predetermined acceleration in the dead zone (C84 in FIG. 15) in which the roll detection means does not detect a roll equal to or greater than the set value during traveling, Is controlled in a softer damping force mode than the selected damping force mode (FIG. 20, F1 to F6), and when the acceleration detected by the acceleration detecting means exceeds a predetermined acceleration, a very short time (FIG. 20, F11 ), The damping force of the shock absorber is set to a harder damping force than the current damping force mode (Fig. 20, F10 to F15). In the selected state, the ride comfort in straight running can be improved, and even in the dead zone where the roll control by the roll detection means is not performed, the damping force is immediately reduced to the hard side in a short time when the vehicle body exceeds a predetermined lateral acceleration. Therefore, it is possible to provide a vehicle suspension device that can switch the damping force with good response according to the vehicle body condition.

[Brief description of the drawings]

FIG. 1 is a view showing a vehicle suspension apparatus according to an embodiment of the present invention, FIG. 2 is a view showing a driving and non-driving state of a three-way valve, and FIG. 3 is a drawing showing a driving and non-driving state of a solenoid valve. FIG. 4 is a diagram showing a drive state and a non-drive state of the supply air flow rate switching valve, and FIG. 5 is a diagram showing vehicle speed in soft mode.
Handle angular velocity map, Fig. 6 shows vehicle speed in AUTO mode-steering wheel angular velocity map, Fig. 7 shows vehicle speed-steering wheel angular velocity map in SPORT mode, Fig. 8 shows G sensor map, and Fig. 9 shows control level based on vehicle speed-steering wheel angular velocity map. FIG. 10 is a diagram showing a relationship between a control level and a supply / exhaust time according to a G sensor map,
FIG. 11 is a schematic flowchart showing the operation of one embodiment of the present invention, FIG. 12 is a detailed flowchart showing a rough road determination routine, and FIG. 13 is a diagram showing a G sensor map at normal time and at rough road determination. , FIG. 14 is a diagram showing a change in state according to a change in the output of the vehicle height sensor, FIG. 15 is a detailed flowchart of the roll control routine, FIG. 16 is a detailed flowchart of the swingback reverse control routine, and FIG. Detailed flowchart of the supply / exhaust correction routine, FIG. 18 is a characteristic diagram of the rear internal pressure-front internal pressure, FIG. 19 is a characteristic diagram of the air suspension internal pressure P0 and the supply / exhaust correction coefficient, and FIG. 20 is a detail of the dead zone damping force switching set routine. FIG. 21 is a detailed flowchart of the damping force switching routine. 15a: High pressure reserve tank, 15b: Low pressure reserve tank, 19: Supply air flow rate switching valve, 22, 23, 26, 27 ... Solenoid valve, 36 ... Control unit, 45 ... Pressure sensor.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tetsuya Terada 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-2-155817 (JP, A) JP Hei 2-171311 (JP, A) Japanese Utility Model Showa 62-67816 (JP, U) Japanese Utility Model Showa 59-35106 (JP, U) Japanese Utility Model Hei 1-132408 (JP, U)

Claims (1)

(57) [Claims] A fluid spring chamber provided for each of the left and right wheels and interposed between the wheel and the vehicle body; and a fluid supply means for supplying a fluid to each of the fluid spring chambers via a supply valve means. A fluid discharging means for discharging fluid from each of the fluid spring chambers via a discharging valve means; and a plurality of stages of soft to hard damping force provided for each wheel and interposed between the wheel and the vehicle body. A damping force switching type shock absorber that can be selected to a damping force mode, a roll detecting means for detecting a roll of the vehicle body, and a roll direction when the roll detecting means detects that a roll of the vehicle body is equal to or more than a set value. Roll control means for supplying a required amount of fluid to the contraction-side fluid spring chamber, and opening and closing the required supply valve means and discharge valve means to discharge a required amount of fluid from the extension-side fluid spring chamber. To those with And an acceleration detecting means for detecting a lateral acceleration acting on the vehicle body, wherein the roll control means is detected by the acceleration detecting means in a dead zone region in which the roll detecting means does not detect a roll having the set value or more. If the acceleration does not exceed the predetermined acceleration, the damping force of the shock absorber is controlled to be switched from the selected damping force mode to a soft damping force mode, and the acceleration detected by the acceleration detecting means exceeds the predetermined acceleration. A suspension apparatus for a vehicle, wherein the damping force of the shock absorber is switched from a current damping force mode to a hard damping force mode in a very short time.