JPH0789319A - Active suspension - Google Patents

Abstract

PURPOSE:To realize moderate feeling of rolling at the time of high, lateral acceleration accompanying quick steering by providing a command operating means with a roll- return-collecting-means, which gradually increases the energy of a spring on the inner- wheel side of turning of an automobile for a period from the start of a decrease of an absolute value of lateral acceleration to an arrival at the prescribed value. CONSTITUTION:Hydraulic cylinders 18 FL to RR are placed between a vehicle-body- side-member 10 and respective wheel-side-members 14 of wheels 11 FL to RR, and the working pressure of these cylinders is adjusted by pressure control valves 20 FL to RR. On the other hand, a controller 30 is provided with a correcting means, which received a signal from a lateral acceleration sensor 26, computes in accordance with a self-contained program, and which corrects a command value to the pressure control valves 20 FL to RR making response to the lateral acceleration when the vehicle body is returning in rolling. This correcting means decreases the energy of a spring on the inner-wheel side of turning by a prescribed amount when the absolute value of the lateral acceleration starts decreasing while the vehicle body is returning in rolling, but gradually increases the energy of the spring until the lateral acceleration reaches a prescribed value. Accordingly, when high, lateral acceleration is generated by quick steering, a moderate feeling of rolling can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active suspension, and more particularly to an active suspension which can provide an appropriate roll feeling when a high lateral acceleration is generated in a vehicle body due to fast steering.

[0002]

2. Description of the Related Art As an active suspension for controlling a vehicle body roll during turning, a fluid pressure cylinder and a spring interposed between a vehicle body and each wheel, and a working fluid pressure of the fluid pressure cylinder according to a command value. A pressure control valve for controlling the lateral acceleration of the vehicle body, a lateral acceleration detecting or estimating means for obtaining a lateral acceleration of the vehicle body, and a control device for outputting a command value according to the detected value or the estimated value of the lateral acceleration detecting or estimating means. There is something.

In such an active suspension, the lateral acceleration y "(the positive value when turning right) is taken as the horizontal axis,
Fluid cylinder operating pressure p (ie output pressure of pressure control valve)
FIG. 12 shows an example of the control characteristic in which the vertical axis represents. The horizontal axis in this figure corresponds to p = _PN (neutral pressure). In other words, "both predetermined neutral pressure P _N becomes the operating pressure p of the right and left wheels when the = 0, the absolute value of the lateral acceleration | y" | lateral acceleration y in straight running such as a predetermined value a _c
If it is less than or equal to the absolute value of the lateral acceleration when the operating pressure p reaches the maximum control pressure P _MAX , the lateral acceleration associated with turning | y ″
As | increases, the operating pressure p on the outer and inner wheel sides of turning
Both have the same rate of change, but increase on the outer wheel side of the turn and decrease on the inner wheel side of the turn, and change symmetrically between right turn and left turn. Thus, when the absolute value of the lateral acceleration | y ″ | is less than or equal to the predetermined value a _c , so-called roll zero control is performed so that no roll occurs in the vehicle body.

However, in such control characteristics,
The absolute value of the lateral acceleration | y "| exceeds a predetermined value a _c (for example, in FIG. 12 | y" | = a a) and the working pressure p is P
_Since the vehicle body is held at ₀ or −P ₀ , the vehicle body rolls and the spring interposed between the vehicle body and each wheel is deformed in a direction in which the outer wheel side turns and the inner wheel side extends. At that time, the spring on the outer ring side has energy corresponding to the amount of deformation (for example, 0 ≦
| Y "| ≦ a output linearity of extension and the straight line of each wheel in the _c | y" | a = pressure indicated by the intersection between a (eg P _A), P
Energy E _a ] corresponding to the difference from ₀ is accumulated.

From this state, the absolute value of the lateral acceleration | y ″ | decreases as the turning converges, and when the rolled vehicle body returns to its original position, the absolute value of the lateral acceleration | At the time when y ″ | changes from a to a _c , the energy (eg, E _a ) stored on the outer ring side is released.

[0006]

However, when the rolled vehicle body returns to its original state, if the energy stored in the turning outer wheel is released on the basis of the conventional control characteristics as described above, the vehicle body is particularly swiftly steered. There is a problem that an appropriate roll feeling cannot be obtained when high lateral acceleration occurs.

The present invention has been made in view of the above problems of the prior art, and provides an active suspension which can provide an appropriate roll feeling when a high lateral acceleration is generated in a vehicle body by a fast steering. The purpose is to do.

[0008]

In order to achieve the above object, a first aspect of the present invention is to provide a fluid cylinder interposed between a vehicle body side member and a wheel side member, as shown in FIG. A spring, a control valve that individually controls each fluid cylinder according to a command value, a lateral acceleration detection or estimation unit that detects or estimates the lateral acceleration of the vehicle body, and a lateral acceleration of the lateral acceleration detection or estimation unit. Command value calculation means for calculating the command value given to each control valve for each wheel based on the detected or estimated value, and command value output means for outputting the command value calculated by this command value calculation means to each control valve. In the active suspension including, the command value calculating means has a roll return correcting means for correcting a command value calculated and set according to the magnitude of lateral acceleration when the vehicle body roll returns. The correction means corrects the command value for reducing a predetermined amount of energy from the spring on the turning inner wheel side at the start of the reduction of the absolute value of the lateral acceleration that occurs when the vehicle body rolls back, and then the absolute value of the lateral acceleration decreases. The active suspension is characterized in that the command value is gradually corrected so that the energy of the spring on the turning inner wheel side is gradually increased until it reaches a predetermined value that does not cause vehicle body roll. provide.

According to a second aspect of the present invention, as shown in FIG. 1, fluid cylinders and springs are provided between the vehicle body side member and the wheel side member for each wheel, and the respective fluid cylinders are individually provided according to command values. Control valve, a lateral acceleration detection or estimation means for detecting or estimating a lateral acceleration of the vehicle body, and a command given to each control valve based on the lateral acceleration detection or estimation value of the lateral acceleration detection or estimation means. In the active suspension including command value calculating means for calculating a value for each wheel and command value outputting means for outputting the command value calculated by the command value calculating means to the control valve, the command value calculating means includes ,
When the vehicle body roll returns, it has a roll return correction means for correcting a command value calculated and set according to the magnitude of the lateral acceleration, and the roll return correction means has a lateral acceleration absolute value generated when the vehicle body roll returns. At the start of the decrease, the command value is corrected to increase the energy of the spring on the turning inner wheel side by a predetermined amount, and then the absolute value of the lateral acceleration is decreased to a predetermined value that does not cause the vehicle body roll. Until then, there is provided an active suspension characterized in that the command value for gradually reducing the energy of the spring on the turning inner wheel side is corrected.

[0010]

In the active suspension according to the first aspect, when the vehicle body roll is returned, the command value on the turning inner wheel side is corrected by the roll return correction means. Therefore, at the start of reduction of the lateral acceleration absolute value generated when the vehicle body roll is returned, As the energy of the spring on the turning inner wheel side decreases, the turning inner wheel side of the vehicle body rises,
After the roll is promoted by the amount corresponding to the decrease in the energy, the vehicle body roll returns until the decreasing lateral acceleration reaches a predetermined value set in advance.

In the active suspension according to the second aspect, when the vehicle body roll is returned, the command value on the turning outer wheel side is corrected by the roll return correction means. Therefore, when the lateral acceleration absolute value generated when the vehicle body roll is returned starts to decrease. The turning outer wheel side of the vehicle body sinks as the energy of the spring on the turning outer wheel side increases, and after the roll is promoted by an amount corresponding to the increase in the energy, the decreasing lateral acceleration becomes a predetermined value set in advance. The car body rolls back in between.

Therefore, according to claims 1 and 2,
When the vehicle body roll returns, the vehicle body returns to the original position after tilting in the direction in which the roll is promoted when the vehicle body roll starts to return. That is, the relationship between the roll angle (absolute value) of the vehicle body and the lateral acceleration is, for example, as shown in FIG. 2, and compared with the conventional case where the roll is returned to the predetermined value a _c of the lateral acceleration as it is, Since the return speed of the vehicle is increased, the return of the roll is felt lightly, and an appropriate roll feeling can be obtained when high lateral acceleration is generated in the vehicle body due to fast steering.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The active suspension of each embodiment shows a case where only roll control of the vehicle body is performed. First, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 3, 1
0 is the suspension arm member on the vehicle body side, 11FL
-11RR indicates front left-right rear wheels, and 12 indicates active suspension.

The active suspension 12 is a hydraulic cylinder 18 as a fluid cylinder that is interposed between the vehicle body side member 10 and the wheel side members 14 of the wheels 11FL to 11RR.
FL to 18RR, pressure control valves 20FL to 20RR for individually adjusting the operating pressures of the hydraulic cylinders 18FL to 18RR, a hydraulic pressure source 22 of this hydraulic system, and a hydraulic pressure between the hydraulic pressure source 22 and the pressure control valves 20FL to 20RR. Accumulators 24, 24 for accumulating pressure, which are interposed by the pipes 22a, 22b, and a lateral acceleration sensor 26 for detecting acceleration generated in the lateral direction of the vehicle body.
And a controller 30 that individually controls the output pressures of the pressure control valves 20FL to 20RR based on the detection signal of the lateral acceleration sensor 26.

Each of the pressure chambers L of the hydraulic cylinders 18FL to 18RR described later is connected to an accumulator 34 for absorbing unsprung vibration via a throttle valve 32. Further, a coil spring 36, which has a relatively low spring constant and supports a static load of the vehicle body, is arranged between the upper and lower springs of each of the hydraulic cylinders 18FL to 18RR.
Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a, and a lower pressure chamber L separated by a piston 18c is formed in the cylinder tube 18a. The lower end of the cylinder tube 18a is attached to the wheel side member 14, and the upper end of the piston rod 18b is attached to the vehicle body side member 10. Further, each of the pressure chambers L has a pressure control valve 20FL via a hydraulic pipe 38.
It is connected to the output port of ~ 20RR.

Further, each of the pressure control valves 20FL to 20RR has a conventionally known three-port proportional electromagnetic pressure reducing valve having a cylindrical valve housing and a proportional solenoid integrally provided therein (for example, Japanese Patent Laid-Open Publication No. Sho. No. 64-74111). Then, by adjusting the command current i (command value) supplied to the exciting coil of the proportional solenoid,
Operation that controls the movement distance of the poppet housed in the valve housing, that is, the position of the spool, and that flows between the hydraulic source 22 and the hydraulic cylinders 18FL to 18RR via the supply port and the output port or the output port and the return port. You can control the oil.

The relationship between the command current i (: i _{FL to} i _RR ) applied to the exciting coil and the control pressure p output from the output port of the pressure control valve 20FL (to 20 _RR ) is shown in FIG. It is like this. That is, when the minimum current value i _MIN taking noise into consideration, the minimum control pressure P _NIM is reached. When the current value i is increased from this state, the control pressure p increases linearly in proportion to the current value i and the maximum current When the value is i _MAX , the maximum control pressure P _MAX corresponding to the set line pressure is obtained. i
_N is the neutral command current and P _N is the neutral control pressure.

On the other hand, a lateral acceleration sensor 26 is fixedly installed on the vehicle body. The lateral acceleration sensor 26 detects lateral (vehicle width) acceleration acting on the vehicle body. For example, the controller controls a voltage signal g corresponding to a displacement amount when a magnetically floated mass is displaced by an inertial force. Output to 30. Then, as shown in FIG. 5, the detection characteristic thereof is as follows. When the lateral acceleration y ″ = 0, the detection signal g = g _N (predetermined neutral lateral G
Detection value), which increases or decreases in proportion to the lateral acceleration y ″ when the vehicle makes a left turn or a right turn from this state.
Here, the lateral acceleration y ″ has a positive value when turning right and a negative value when turning left.

Further, the controller 30 is, as shown in FIG. 6, an A / D converter 70 for converting the detection signal g corresponding to the input lateral acceleration y ″ into a digital quantity,
A microcomputer 72 for arithmetic processing, D / A converters 73A to 73D for individually converting the digital voltage command values V _{FL to} V _RR output from the microcomputer 72 into analog amounts, and the analog amount Voltage command value V
_It has drive circuits 74A to 74D which make command currents i _{FL to} i _RR individually output to the pressure control valves 20 _{FL to 20 RR} with _{FL to} V _RR as a target value follow the target value.

Among them, the microcomputer 72 has at least the interface circuit 76 and the arithmetic processing unit 78.
And a storage device 80 including a RAM and a ROM, and the interface circuit 76 includes an I / O port and the like. Further, the arithmetic processing unit 78 reads the detection signal g through the interface circuit 76 and performs arithmetic processing and other processing described later based on the detection signal g. The storage device 80 stores in advance a predetermined program and fixed data necessary for executing the processing of the arithmetic processing device 78, and also stores a processing result of the arithmetic processing device 78.

Then, in the microcomputer 72,
The programs shown in FIGS. 7 and 8 are stored. Figure 7
In order to control the control pressure to the fluid pressure cylinder of each wheel, the program of the voltage command values V _{FL to} V _RR to the pressure control valves 20FL to 20RR is set in the order of, for example, the front left wheel to the rear right wheel. This is for sequentially calculating each wheel to be controlled.

In this program, the detection signal g of the lateral acceleration sensor 26 is read in step S1, and step S2
Move to. In step S2, the neutral lateral G detection value g _N is subtracted from the detection signal g read in step S1 to obtain the lateral acceleration detection signal Δg. Then step S
3, the lateral acceleration y ″ corresponding to the detection signal Δg is calculated by referring to the storage table stored in the storage device 80 in advance.

Next, in step S4, the pressure command values P _{FL to} P _RR for each wheel are set according to the subroutine shown in FIG. In this program, α is a symbol for identifying the sign of the detected lateral acceleration y ″ _(n) (that is, right turn or left turn). When positive, α = + 1, and when negative, α =
It is set to -1. That is, since the lateral acceleration y ″ during right turn is positive here, α = + 1 during right turn,
When turning left, α is set to −1. β is a symbol for identifying whether the wheel to be controlled is the left or right wheel, and is set to β = + 1 for the left wheel and β = −1 for the right wheel. Therefore, when the wheel to be controlled corresponds to the turning inner wheel, α · β = −1.

Further, P ₀ is a pressure command value for making the working pressure p of the fluid cylinder the maximum control pressure P _MAX, and P _{0 is}
= Maximum control pressure P _MAX - represented by the neutral pressure P _N. a _c indicates the absolute value of the lateral acceleration when the absolute value of the pressure command value P becomes P ₀ . K _G represents the set gain, and P ₀ = K _G
a _c . ΔP is the energy E _a (accumulated in the spring interposed between the turning outer wheel and the vehicle body, depending on the absolute value of the lateral acceleration | y ″ _(n) | when the vehicle rolls. (See FIG. 9 described later), which is the pressure corresponding to
It is represented by P = K _G (| y ″ _(n) | −a _c ).

That is, in step S4, first, in step S401, the previous and current lateral acceleration y "is calculated.
_(n-1) , y " _(n) are read, and the process proceeds to step S402. Here, the sign of the detected lateral acceleration y" _(n) of this time is judged, and if y " _(n) ≥ 0, For example, the process proceeds to step S403 to set α to +1. If y ″ _(n) <0, the process proceeds to step S404 to set α to −1 and then to step S405. In step S405, it is determined whether the wheel to be controlled is the left wheel, and if it is the left wheel, the process proceeds to step S406 and β
Is set to +1 and if the wheel is a right wheel, the process proceeds to step S407, β is set to -1, and then step S408 is performed.
Move to.

In step S408, the previous absolute value of lateral acceleration | y ″ _(n−1) | and the current absolute value of lateral acceleration | y ″.
_(n) | is compared to determine whether the absolute value of the lateral acceleration is in the increasing or decreasing direction. Then, the direction in which the absolute value of the lateral acceleration increases (that is, | y ″ _(n) | − | y ″ _(n-1) |
If ≧ 0), the process proceeds to step S409, the process proceeds to step S410 to calculate the pressure command value P = K _G · y "to _(n).

In step S410, it is determined whether the absolute value | P | of the calculated pressure command value is P ₀ or less. If | P | ≦ P ₀ , the process proceeds to step S411 and β · P Is set to the pressure command value P, and if | P |> P ₀ , the flow shifts to step S412 to set β · P ₀ to the pressure command value P
After setting to, the process proceeds to step S413 and the pressure command value P is output.

In step S408, the absolute value of the lateral acceleration is
Direction of decrease (ie | y ″_(n)｜ − ｜ y ″_(n-1)｜ ＜
If it is determined to be 0), go to step S414.
Transition to absolute value of lateral acceleration | y ″_(n)| Is a_cAnd above
Judge whether or not, ｜ y ″ _(n)│ ≧ a_cIf so
Go to step S415 to determine whether α / β = -1.
It Where α · β = -1 (that is, the wheel is
If it is a wheel, the process proceeds to step S416 and ΔP = K
_G(| Y ″_(n)| -A_c) Is calculated and step S417
To P = α ・ β (P₀−ΔP) = − 1 · (P₀−
ΔP) = − P₀After calculating + ΔP, step S413
Then, this P is output as a pressure command value.

When it is determined that | y ″ _(n) | <a _{c in} step S414 and α · β ≠ −1 in step S415.
If it is determined that the above, the process proceeds to step S409, and the above-described S409 to S413 are executed. Step S413
When the pressure command value is output at, the process returns to the main program shown in FIG.

After that, the arithmetic processing unit 78 proceeds to step S5 of FIG. 7 and voltage command values V _{FL to} V _RR (set at step S4) for achieving the pressure command values P _{FL to} P _RR of each wheel. The pressure command values P _{FL to} P _RR and the neutral pressure P _N are added to calculate the actual operating pressure p). Then, in step S6, the voltage command values V _{FL to} V _RR are individually output to the D / A converters 73A to 73D via the interface circuit 76.

Next, the operation of the above embodiment will be described. It should be noted that here, only the control performed by the vehicle traveling straight or turning and the vehicle behavior are considered. When the ignition switch of the vehicle body is turned on, the controller 30 is activated and the timer interrupt process shown in FIG. 7 is executed at predetermined time intervals (for example, 20 msec) during execution of a predetermined main program.

Now, it is assumed that the vehicle body is traveling straight on a good road having no unevenness at a constant speed. In this state, since lateral acceleration due to turning is not generated, the detection signal g of the lateral acceleration sensor 26 is its neutral value g _N , and the controller 30
The lateral acceleration y ″ calculated by is zero (see steps S1 to S3 in FIG. 7). Also, | y ″ _(n) | − | y ″
_(n-1) | = 0, so each pressure command value P _{FL to} P _RR = 0
(Operating pressure p = _PN ) (step S401 to S401 in FIG. 8)
413). Therefore, the voltage command value V _{FL to} V _RR = V
_N (voltage value for setting the operating pressure p of the hydraulic cylinders 18FL to 18RR to P _N ) is calculated (see step S5 in FIG. 7), and this neutral voltage command value V _N is the D / A converter 73A to.
It is output to 73D respectively.

Then, the voltage command values V _{FL to} V _RR (=) converted into analog amounts by the D / A converters 73 A to 73 D.
V _N) are respectively outputted to the drive circuit 74A~74D as a target value, the target value V _N from the driving circuit 74A~74D
The neutral command current i _N corresponding to the pressure control valves 20FL to 20R
It is supplied to R respectively. As a result, the pressure control valve 20FL
The 20RR controls the working pressure p of each of the hydraulic cylinders 18FL to 18RR to the neutral pressure P _N (see FIG. 4). Therefore, each of the hydraulic cylinders 18FL to 18RR generates a force corresponding to the neutral pressure P _N, and Is held in a neutral posture at a predetermined vehicle height value.

When the constant speed straight traveling state is changed to, for example, a right turning state, an inertial force acts on the right side of the vehicle body to try to generate a roll in which the left side of the vehicle body sinks and the right side floats. At the time of this right turn, the detection signal g of the lateral acceleration sensor 26 is larger than the neutral lateral G detection value g _N by an amount corresponding to the turning speed and the like, so that the controller 30 has a lateral acceleration signal Δg> 0. This Δ in step S3 of FIG.
A positive lateral acceleration y ″ corresponding to g is calculated, and the pressure command values P _{FL to} P _RR for each wheel are set based on the lateral acceleration y ″.

Here, referring to FIG. 9, the left wheel which is the turning outer wheel.
The pressure command value P on the side will be explained.
Since the wheel to be controlled by turning is the left wheel, step S
From 401 to S403 through S405 and S406, α =
After setting +1 and β = + 1, the process proceeds to S408. And
Lateral acceleration y ″ from step S408 to S409_(n)But
In the increasing state, the predetermined value a_cIn the following cases | P | ≦ P
₀Therefore, the pressure command value P is calculated in step S409.
P = (β · that is issued and set in S410 to S411
(K _G・ Y ″_(n)) =) K_G・ Y ″_(n)The straight line represented by
L₁Is controlled to increase along. This allows
Neutralize the operating pressure p of the left wheel hydraulic cylinders 18FL, 18RL
Pressure P_NThe pressure command value P higher than
Does not cause Therefore, the straight line L₁Is roll zero
It is a control curve.

When the lateral acceleration y ″ _(n) from step S408 to step S409 is in the increasing state and is larger than the predetermined value a _c , | P |> P ₀ is established, and therefore step S410 to step S412 are reached, and β · Since P ₀ = + P ₀ is set as the pressure command value P, the operating pressure p is held at P _MAX (that is, on the straight line L ₂ ) in the left wheel that is the turning outer wheel, which further increases the lateral acceleration. Along with this, a roll occurs in the vehicle body, and energy (for example, E _a when y ″ = _a ) is accumulated in the spring interposed between the vehicle body and the left wheel.

Then, from this state, step S408
When the absolute value of the lateral acceleration | y ″ _(n) | from the step S to the step S414 is in a decreasing state, α · β = + 1, and therefore the step S415 to the step S409, the lateral acceleration y ″
_(n) is the out greater than the predetermined value a _c along line L ₂ P
_The pressure command value P is controlled so as to be held at ₀ and decrease along L ₁ when it becomes equal to or less than a _c .

The pressure command value for the right wheel, which is the inner wheel for turning,
For P, the wheels to be controlled by turning this turn to the right
Is a right wheel, steps S401 to S403 to S
405, S407 and α = + 1, β = -1
To S408. Then, steps S408 to S4
Lateral acceleration y ″ reaching 09_(n)Is increasing and the
Value a_cIn the following cases | P | ≦ P₀Therefore, the pressure command
The value P is calculated in step S409 and S410-S
P = (β · (K _G・ Y ″_(n)) =)
-K_G・ Y ″_(n)The straight line L represented by₁₁Increase along
Controlled as. As a result, the hydraulic cylinder on the right wheel side
18FL, 18RL working pressure p is neutral pressure P_NTo pressure command value
Lower by P to prevent rolling on the car body. did
The straight line L₁₁Is the roll zero control curve.

When the lateral acceleration y ″ from steps S408 to S409 is in an increasing state and is larger than the predetermined value a _c , | P |> P ₀ , so that steps S410 to S410.
412 and β · P ₀ = −P ₀ is set as P in S412. Therefore, the working pressure p is maintained at P _MAX (that is, on the straight line L ₂₁ ) in the right wheel that is the turning inner wheel. As the lateral acceleration increases, the body rolls.

From this state, steps S408 to S4
The lateral acceleration y ″ reaching 14 is in a decreasing state, and further S
While the lateral acceleration y ″ _(n) from 414 to S415 is a _c or more, α · β = −1, and thus step S415.
From S416, the pressure ΔP corresponding to the energy (eg, E _a ) accumulated in the spring on the left wheel side, which is the outer wheel for turning, is calculated in S416, and this ΔP is added to −P ₀ in step S417. pressure command value P = -P ₀ + ΔP
Is set, the pressure command value P for the right wheel, which is the inner turning wheel, is set.
Is increased by ΔP along the straight line L ₃ to reduce the energy from the spring on the right wheel side by, for example, E _a, and then becomes a straight line L ₄ until y ″ _(n) = a _c. It is controlled to decrease along.

Then, from this state, step S414
From step S409 to step S409, if the lateral acceleration y ″ is in a decreasing state and is smaller than a _c , steps S409 to S410.
Pressure command value P is controlled to be increased along the Roruzero straight line L ₁₁ reaches the S411 from. As a result, at the start of the reduction of the lateral acceleration that occurs when the vehicle body rolls back, the energy of the spring of the right wheel, which is the turning inner wheel side, is equivalent to the energy (for example, E _a ) stored in the spring of the left wheel that is the turning outer wheel by the roll. However, the right side of the car body rises. That is, when the roll starts returning, after the roll is promoted by the amount corresponding to the decrease in energy, the body roll returns until the decreasing lateral acceleration reaches a _c .

Therefore, the roll angle of the vehicle body (absolute value)
The relationship between the roll acceleration and the lateral acceleration is as shown in FIG. 2, and the roll return speed is higher than that in the conventional case where the roll is returned to the predetermined value a _c of the lateral acceleration as it is.
It feels that the roll returns lightly, and when a high lateral acceleration is generated in the vehicle body due to quick steering, a proper roll feeling can be obtained. Further, since the roll zero control is performed when the lateral acceleration fluctuates in the forward and reverse directions, it is difficult for the rolling back to occur due to the change in the lateral acceleration in the forward and reverse directions.

In this embodiment, the lateral acceleration sensor 2
6, A / D converter 70, and steps S1 to S of FIG.
The process of 3 constitutes the lateral acceleration detecting means, and steps S4 to 5 of FIG. 7 correspond to the command value calculating means, and step S of FIG.
6, D / A converters 73A to 73D, drive circuit 74A
.About.74D constitutes command value output means. Further, in this program, steps S414 to 417 correspond to the roll return correcting means of the present invention.

Next, a second embodiment of the present invention will be described. In this embodiment, the program shown in FIG. 10 is stored in the microcomputer 72 as a subroutine of step S4 in FIG. 7 in place of the program of FIG. 8 in the first embodiment, and other than that is the first embodiment. It has the same structure as. Then, this program corresponds to step S415 in the program of FIG.
Corresponds to the deleted one. That is, when the absolute value of the lateral acceleration is in a decreasing state and is equal to or greater than a _c without judging whether the wheel to be controlled corresponds to the turning inner wheel or not, even if the wheel is the turning outer wheel. The roll return correction control from steps S416 to 417 to S413 is performed.

That is, even if α · β = + 1, the process proceeds from step S414 to S416, where ΔP = K
_{G (| y "(n)} | -a c) is calculated, step S417
And P = α · β (P ₀ −ΔP) = + 1 · (P ₀ −
After calculating ΔP) = + P ₀ −ΔP, step S413
Then, this P is output as a pressure command value. Therefore, even for the left wheel side, which is the turning outer wheel when turning right,
Lateral acceleration y ″ _(n) from step S408 to S414
Is in a decreasing state, and while the lateral acceleration y ″ _(n) from S414 to S416 is _{equal to} or greater than a _c , S416
The pressure ΔP corresponding to the energy (for example, E _a ) accumulated in the spring on the left wheel side, which is the outer turning wheel, is calculated, and the pressure command value P = P _{0 obtained by} subtracting this ΔP from P _{0 in} step S417. because -ΔP is set, the pressure command value P of the left wheel is turning outer, for example E _a to the left wheel side spring by reducing only ΔP along the line L ₃₁ in FIG. 11
After increasing the minute energy, the energy is controlled to increase along the straight line L ₄₁ until y ″ _(n) = a _c .

Then, from this state, step S414
From step S409 to step S409, if the lateral acceleration y ″ is in a decreasing state and is smaller than a _c , steps S409 to S410.
From S to S411, the pressure command value P is controlled so as to decrease along the roll zero straight line L ₁ . As a result, at the start of the reduction of the lateral acceleration that occurs when the vehicle body rolls back, the energy of the spring of the right wheel, which is the turning inner wheel side, is equivalent to the energy (for example, E _a ) stored in the spring of the left wheel that is the turning outer wheel by the roll. And the energy of the left wheel spring, which is the outer wheel turning side, is increased by the amount of energy stored in the left wheel spring (for example, E _a ),
As a result, the right side of the vehicle body floats and the outer ring side sinks.

That is, at the start of the roll return, after the roll is promoted by the amount corresponding to the energy stored in the spring on the left wheel side, which is the outer turning wheel, until the decreasing lateral acceleration becomes a _c. The body roll is returned to and the roll center is not changed at that time. Therefore, the relationship between the roll angle (absolute value) of the vehicle body and the lateral acceleration is as shown in FIG. 2, which is compared with the conventional case where the roll is returned to the predetermined value of the lateral acceleration a _c as it is. Since the speed is increased, the roll returns are felt lightly, and an appropriate roll feeling can be obtained when high lateral acceleration is generated in the vehicle body due to fast steering. Further, since the roll zero control is performed when the lateral acceleration fluctuates in the forward and reverse directions, it is difficult for the rolling back to occur due to the change in the lateral acceleration in the forward and reverse directions. Further, since the vehicle body can be returned to the original position without changing the roll center, the occupant's discomfort is alleviated.

As described above, in each of the above embodiments, the pressure command value is corrected only on the turning inner wheel side or on both the inner wheel side and the outer wheel side when the vehicle body roll is returned, but only the turning outer wheel is corrected. Good. Further, the means for obtaining the lateral acceleration of the present invention is not limited to the one having a structure for directly detecting the inertial force by using the lateral acceleration sensor as described above, and estimates the lateral acceleration based on the vehicle speed and the steering angle, for example. Means (see, for example, JP-A-62-293167). Further, the present invention can of course be applied to an active suspension that also performs pitch control and bounce control of the vehicle body.

Further, the fluid cylinder of the present invention is not limited to the case where the hydraulic cylinder is applied as in the above-mentioned embodiment, and for example, a pneumatic cylinder or the like may be used, and the control valve is the fluid cylinder. It is also possible to control the flow rate of.

[0050]

As described above, according to the active suspensions of claims 1 and 2, when the vehicle body roll is returned, the command value given to the control valve of the fluid cylinder on the turning inner wheel side or the outer wheel side is returned to the roll. Controlled by the correction means, the vehicle body behaves so as to tilt back in the direction in which the roll is promoted at the start of roll return and then return to the original state,
An appropriate roll feeling can be obtained when high lateral acceleration is generated in the vehicle body due to fast steering.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a graph showing the relationship between the roll angle (absolute value) of the vehicle body and the lateral acceleration, for explaining the operation of the present invention.

FIG. 3 is a schematic configuration diagram showing first and second embodiments of the present invention.

FIG. 4 is a graph showing an output characteristic of a pressure control valve.

FIG. 5 is a graph showing the detection characteristics of the lateral acceleration sensor.

6 is a block diagram showing an example of the controller of FIG. 4. FIG.

FIG. 7 is a flowchart showing an example of a processing procedure executed in a controller regarding the first and second embodiments.

FIG. 8 is a flowchart of a subroutine corresponding to step S4 of the flowchart of FIG. 6 regarding the first embodiment.

FIG. 9 is a control characteristic diagram of a pressure command value in the first embodiment.

FIG. 10 is a flowchart of a subroutine corresponding to step S4 of the flowchart of FIG. 6 regarding the second embodiment.

FIG. 11 is a control characteristic diagram of a pressure command value in the second embodiment.

FIG. 12 is a control characteristic diagram of a conventional operating pressure.

[Explanation of symbols]

 10 Body-side member 12 Active suspension 14 Body-side member 18FL-18RR Front left-rear right hydraulic cylinder (fluid cylinder) 20FL-20RR Front left-rear right pressure control valve 26 Lateral acceleration sensor (lateral acceleration detection means) 36 Coil spring (Spring) 70 A / D converter (lateral acceleration detection means) 73A to 73D A / D converter (command value output means) 74A to 74D drive circuit (command value output means)

Claims (2)

[Claims] 1. A fluid cylinder and a spring interposed between a vehicle body side member and a wheel side member for each wheel, a control valve for individually controlling each fluid cylinder according to a command value, and a lateral side of the vehicle body. Lateral acceleration detection or estimation means for detecting or estimating directional acceleration, and command value calculation for calculating a command value given to each control valve for each wheel based on the lateral acceleration detection or estimation value of the lateral acceleration detection or estimation means In the active suspension, including means and command value output means for outputting the command value calculated by the command value calculation means to the control valve, the command value calculation means is capable of controlling the lateral acceleration when the vehicle body rolls back. The roll return correction means has a roll return correction means for correcting a command value calculated and set according to the size, and the roll return correction means is provided for the turning inner wheel side at the start of the decrease of the lateral acceleration absolute value generated when the vehicle body roll is returned. After correcting the command value to reduce a predetermined amount of energy from the spring, until the absolute value of the lateral acceleration decreases to a preset predetermined value that does not cause vehicle body roll, the turning inner wheel side An active suspension characterized in that the command value for gradually increasing the energy of a spring is corrected. 2. A fluid cylinder and a spring interposed between the vehicle body side member and the wheel side member for each wheel, a control valve for individually controlling each fluid cylinder according to a command value, and a lateral side of the vehicle body. Lateral acceleration detection or estimation means for detecting or estimating directional acceleration, and command value calculation for calculating a command value given to each control valve for each wheel based on the lateral acceleration detection or estimation value of the lateral acceleration detection or estimation means In the active suspension, including means and command value output means for outputting the command value calculated by the command value calculation means to the control valve, the command value calculation means is capable of controlling the lateral acceleration when the vehicle body rolls back. The roll return correction means has a roll return correction means for correcting a command value calculated and set according to the size, and the roll return correction means is provided for the turning inner wheel side at the start of the decrease of the lateral acceleration absolute value generated when the vehicle body roll is returned. After the command value is corrected to increase the energy of the spring by a predetermined amount, until the absolute value of the lateral acceleration decreases to a predetermined value that does not cause vehicle body roll, the turning inner wheel side An active suspension characterized in that the command value for gradually reducing the energy of a spring is corrected.