JP2906634B2 - Active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an active suspension that suppresses a change in posture of a fluid cylinder such as a hydraulic cylinder interposed between a vehicle body and wheels in the longitudinal direction of the vehicle body.

[Conventional technology]

As a conventional active suspension, there is known a suspension disclosed in Japanese Patent Application Laid-Open No. 62-295714, which has been proposed by the present applicant.

This conventional device includes a fluid pressure cylinder interposed between a vehicle body and each wheel, a pressure control valve for controlling a working fluid pressure of the fluid pressure cylinder according to a command value, and detecting or detecting longitudinal acceleration of the vehicle body. There is provided a means for estimating, and a control means for calculating a command value according to a detection value or an estimated value of the means, and outputting the calculated value to the pressure control valve. Specifically, the control means includes a process of multiplying the detected value or the estimated value of the longitudinal acceleration by the control gain, thereby calculating the control output in the anti-pitch direction, that is, the command value.

[Problems to be solved by the invention]

However, in the conventional active suspension described above, since the force control is performed in accordance with the occurrence of longitudinal acceleration, when braking and acceleration are performed, an anti-pitting moment is obtained along with the occurrence of longitudinal acceleration, and the load transfer Will occur. The timing at which the load shift occurs is earlier than that of a conventional suspension in which a load shift occurs after pitching, which mainly includes a shock absorber and a spring. As a result, sudden braking during turning,
When the vehicle is accelerated, there is a possibility that the steering characteristics change, for example, a tack-in occurs during braking and an under characteristic occurs in an initial state during acceleration.

The present invention has been made in view of such a situation,
The problem to be solved is to surely prevent a change in the steering characteristics when sudden braking and acceleration are performed during turning.

[Means for solving the problem]

In order to solve the above-mentioned problem, the invention described in claim (1) is, as shown in FIG. 1 (a), a fluid cylinder interposed between a vehicle body-side member and a wheel-side member, and an operation for supplying the fluid cylinder to the fluid cylinder. A control valve for controlling a fluid in accordance with a command value; a longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle; and a suppression of a vehicle pitch based on a product of a detected value of the longitudinal acceleration detecting means and a pitch control gain. Turning state detecting means for detecting a signal corresponding to a turning state of a vehicle in an active suspension including a command value calculating means for calculating a command value and outputting the calculated value to the control valve; Control gain changing means for changing the pitch control gain according to the detection value of the means. It is desirable that the control gain changing means is means for reducing the control gain as the detection value of the turning state detecting means increases.

According to a second aspect of the present invention, as shown in FIG. 1 (b), a fluid cylinder interposed between a vehicle body-side member and a wheel-side member and a working fluid supplied to the fluid cylinder are changed according to a command value. A control valve for controlling the vehicle, longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle, and a command value for suppressing the pitch of the vehicle based on a product of a detected value of the longitudinal acceleration detecting means and a pitch control gain. In an active suspension having command value calculating means for outputting a calculated value to the control valve, a turning state detecting means for detecting a signal corresponding to a turning state of the vehicle, Control delay means for delaying the output of the command value from the command delay means to the control valve is provided.

[Action]

In the invention described in each claim, when the vehicle is going straight,
A command value is calculated based on the product of the longitudinal acceleration of the vehicle and the pitch control gain, and the control valve controls the operation of the fluid cylinder based on the command value. As a result, an anti-pitch moment is generated, the wheel load moves between the front and rear wheels before pitching, and a substantially flat body posture is obtained.

On the other hand, according to the invention described in claim (1), when accelerating or decelerating in the turning state, as the lateral acceleration corresponding to the turning state increases, for example, the pitch control gain is reduced by the control gain changing means, for example. For this reason,
Even in the same acceleration / deceleration state in the front-rear direction, the deeper the turning state, the smaller the anti-pitch moment due to the decrease in pitch control gain.Although slight pitching is allowed, the amount of load movement between the front and rear wheels is small. Decrease. Due to the decrease in the wheel load movement amount, the change in the steering characteristic at the time of sudden acceleration and sudden deceleration is eliminated.

In the invention described in claim (2), when accelerating or decelerating in the turning state, as the lateral acceleration corresponding to the turning state increases, for example, the output of the command value to the control valve is delayed by the control delay means. For this reason, the load transfer between the front and rear wheels is actively delayed during braking and driving during turning,
Tack-in during braking and changes to understeer at the beginning of driving are eliminated.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First Embodiment A first embodiment will be described with reference to FIGS. 2 to 6 of the accompanying drawings.

In FIG. 2, reference numeral 10 denotes a vehicle body-side member, and 11FL to 11RR.
Indicates front left to rear right wheels, and 12 indicates an active suspension.

The active suspension 12 includes a vehicle body-side member 10 and wheels 11FL.
Hydraulic cylinders 18FL to 18RR as fluid cylinders interposed between the respective wheel-side members 16 to 11RR, and a pressure control valve 20FL as a control valve for individually adjusting the operating oil pressure of the hydraulic cylinders 18FL to 18RR. ~ 20RR and the hydraulic source 22 of this hydraulic system
And a pressure accumulator 24, 24 interposed between the hydraulic pressure source 22 and the pressure control valves 20FL to 20RR, a lateral acceleration sensor 26 as turning state detecting means, and a longitudinal acceleration sensor as longitudinal acceleration detecting means. It has an acceleration sensor 27 and a controller 30 for individually controlling the output pressures of the pressure control valves 20FL to 20RR. A coil spring 31 having a relatively low spring constant and supporting a static load of the vehicle body is provided between the wheel and the vehicle body.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a.
A lower pressure chamber L separated by 18c is formed. The lower end of the cylinder tube 18a is
6, and the upper end of the piston rod 18b is attached to the vehicle body side member 10. Also, each of the pressure chambers L
A part of the hydraulic pressure passes through the output ports of the pressure control valves 20FL to 20RR via a hydraulic pipe 38 provided in the axial direction inside the piston rod 18b, whereby the working oil pressure in the pressure chamber L can be controlled. ing. Each pressure chamber L is connected to a vibration absorbing accumulator 34 via a throttle valve 32 as shown.

Each of the pressure control valves 20FL to 20RR is a pilot type proportional electromagnetic pressure reducing valve (for example, Japanese Patent Laid-Open No. 62-2957).
The output pressure P supplied from the output port to the hydraulic cylinder 18FL (~ 18RR) by controlling the command current i (: i _{FL to} i _RR ) supplied to the proportional solenoid.
Can be controlled in proportion to the value of the command current i as shown in FIG. In FIG. 2, pipes 40 and 42 connect the hydraulic pressure source 22 and the pressure control valves 20FL to 20RR.

The lateral acceleration sensor 26 and the longitudinal acceleration sensor 27 are provided at predetermined positions on the vehicle body. Among them, the lateral acceleration sensor 26 detects as the vehicle body in the transverse direction Figure 4 the analog voltage signal Y _G corresponding to the acceleration (vehicle width direction) (a), the controller 30
Output to Longitudinal acceleration sensor 27 detects as analog voltage signals X _G to FIG. 4 (b) and in accordance with the longitudinal acceleration of the vehicle body, similarly output to the controller 30.

The controller 30, as shown in FIG. 5, enter the longitudinal acceleration detection signal X _G, a gain adjuster 50 which multiplies the input signal X _G can be changed to control gain K _X, inverter for inverting the sign of the signal 52 and an absolute value circuit 54 for calculating the absolute value of the signal
And drive circuits 56FL to 56RR for outputting a current signal corresponding to the input voltage signal. The gain adjuster 50 uses the lateral acceleration detection signal | Y _G | that has passed through the absolute value circuit 54 as a gain adjustment signal, and according to the magnitude of the gain adjustment signal | Y _G |, as shown in FIG. K _X is to be changed. That is, the gain adjustment signal | Y _G | = 0 to Y _G1
Until the control gain K _X = predetermined value K _X1 , the control gain K _X is reduced as | Y _G | exceeds Y _G1 .

The output terminals of the gain adjuster 50 are the drive circuits 56FL and 56F as they are.
Connected to the front left and front right pressure control valves 20FL and 20FR via R, and connected to the rear left and rear right pressure control valves 20RL and 20RR via an inverter 52 and drive circuits 56RL and 56RR. I have. Therefore, the proportional solenoid of the pressure control valve 20FL~20RR is command current i _FL through i _RR values corresponding to "X _G · K _X" and "-X _G · K _X" is output.

In the first embodiment, the gain adjuster 50, the inverter 52, and the driving circuits 56FL to 56RR constitute a command value calculating means, and the gain adjuster 50 and the absolute value circuit 54 constitute a control gain changing means. .

 Next, the operation of this embodiment will be described.

First, it is assumed that the vehicle is traveling straight ahead at a constant speed. In this running state, the longitudinal acceleration sensor 27 and the lateral acceleration sensor
Since the 26 detection signals X _G and Y _G both become zero, the pitch control gain K _X = K _X1 of the gain adjuster 50 is set by Y _G = 0, but the output signal “Y _G K _X becomes zero, and the command signals i _{FL to} i _RR from the drive circuits 56 _FL to 56 _RR also become zero. For this reason, the four-wheel pressure control valves 20FL-20RR
Output pressure P = P ₀ (predetermined pressure), and each hydraulic cylinder 18
Because operating pressure of FL~18RR is controlled to the pressure P _0, the vehicle body is kept constant at a height determined on the basis of the operating pressure P _0.

During this traveling straight, for example, performs a rapid acceleration, while maintaining the lateral acceleration detection signal Y _G = 0, a negative value according to the acceleration degree take longitudinal acceleration signal X _G. Accordingly, pitch control gain K _X of the gain adjuster 50 K _X = K _X1 is maintained, the product "-X _G · K _X1" of the gain K _X1 and longitudinal acceleration X _G is calculated in the form of a voltage signal You. Therefore, the drive circuits 56FL and 56F for the front wheels
R is the command current −i _FL , −i corresponding to the product “−X _G · K _X1 ”.
_FR (−i _FL = −i _FR ) is output to the pressure control valves 20FL and 20FR, respectively, and the drive circuits 56RL and 56RR on the rear wheel side provide command currents i _RL and i _RR corresponding to the product “X _G · K _X1 ”. (I _RL = i _RR ) with the pressure control valve 20RL, 20
Output to RR respectively. Therefore, the front wheel side pressure control valve 20FL, 2
Output pressure P of 0FR, i.e. hydraulic cylinders 18FL, working pressure of the 18FR is lowered by an amount corresponding to the "X _G · K _X1" than the predetermined value P _0, the pressure control valve 20RL for the rear wheels in the opposite, the 20RR output pressure P, that the hydraulic cylinders 18RL, working pressure of the 18RR is than the predetermined value P ₀ "X _G · K
_X1 ". As a result, with such rapid acceleration, the hydraulic cylinders 18RL and 18RR on the rear wheel side generate a force against sinking of the vehicle body, and the hydraulic cylinders 18FL and 18FR on the front wheel side do not promote the lifting of the vehicle body. As a result, an anti-pitch moment is generated that faces the scut when the rear of the vehicle body sinks. This anti-pitch moment occurs before the actual pitching occurs, and allows a load transfer between the front and rear wheels to maintain a substantially flat body posture.

On the other hand, if the sudden braking is performed during straight ahead vehicle is to about to fail a nose dive, since the longitudinal acceleration signal X _G for positive is detected, the anti subduction of the front wheel side in the same manner as described above A counter-pitch moment occurs. As a result, the wheel load moves before the actual pitching of the vehicle body occurs, and the nose dive is actively suppressed, so that the vehicle body is held substantially flat.

On the other hand, acceleration and braking are performed during turning.
Now, the lateral acceleration Y _G generated with the turn is a predetermined value | Y _G1 |
Load movement amount of the vehicle body lateral If not reach relatively small, it is determined that the case so different no loose pivoting of straight running, the pitch control gain K _X of the gain regulator 50 to the predetermined value K _X1 Hold. Therefore, when subjected to an accelerated and braked during such turning, occur substantially simultaneously anti pitch moment and the occurrence of longitudinal acceleration X _G, occurs a load moving between the front and rear wheels, flat like the straight running of the aforementioned The body posture is maintained.

However, when the lateral acceleration Y _G accompanying the sharp turn exceeds a predetermined value | Y _G1 |, the pitch control gain K _X is inversely proportional to the excess.
Is lowered. Therefore, even in the event of the same longitudinal acceleration X _G, by an amount gain K _X is lowered gain adjuster
Since the relative values of the 50 operation signals "X _G · K _X" becomes smaller, the absolute value of the command signal i _FL through i _RR can be suppressed small. As a result, the counter pitch moment generated by each of the hydraulic cylinders 18FL to 18RR in the same manner as described above becomes smaller in accordance with the decrease in gain, so that a slight pitch movement occurs, but the amount of load movement between the front and rear wheels decreases. Accordingly, if a relatively large lateral acceleration Y _G makes a sudden braking in turning state occurring, without causing the tuck-load movement amount is too large between the front and rear wheels, and if subjected to rapid acceleration, the Initial understeer changes are eliminated.

Second Embodiment Next, a second embodiment will be described with reference to FIGS. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

In the second embodiment, the intended purpose is achieved by actively delaying the supply of the command currents i _{FL to} i _{RR to} the pressure control valves 20 _{FL to 20 RR} .

Specifically, the controller 30 is configured as shown in FIG. That is, the input side of the controller 30, gain adjuster 60 multiplies the pitch control gain K _X of the constant value to the input longitudinal acceleration signal X _G input signal X _G is provided, the output side of the gain adjuster 60 Is provided with a low-pass filter 62 as a delay element. The low-pass filter 62 has a lateral acceleration signal | Y formed by passing through the absolute value circuit 6.
_G | is supplied as a cutoff frequency adjustment signal.
The low-pass filter 62 determines that the adjustment signal | Y _G |
As the value exceeds Y _G1 , the cutoff frequency f _C is gradually reduced from the predetermined value f _C1 as shown in FIG. At this time, the cutoff frequency f _C = f _C1 in the state of the lateral acceleration | Y _G | ≦ predetermined value Y _G1 is selected to be substantially equal to the change frequency of the command value so that the low-pass filter 62 is not inserted. .

The output side of the low-pass filter 62 reaches the pressure control valves 20FL and 20FR via the drive circuits 66FL and 66FR as in the first embodiment, and the pressure control valves 20RL and 20RR via the inverter 68 and the drive circuits 66RL and 66RR. Leads to.

 Other configurations are the same as those of the first embodiment.

In the second embodiment, the gain adjuster 60, the inverter 68, and the driving circuits 66FL to 66RR constitute a command value calculating means, and the low-pass filter 62 and the absolute value circuit 64 constitute a control delay means.

For this reason, in a gentle turning state and a straight traveling state in which the lateral acceleration | Y _G | is smaller than the predetermined value Y _G1 , the low-pass filter 62
_Is set to be cutoff frequency f _C = f _C1 . This cut-off frequency f _C1 is higher than the upper limit frequency of the command value "X _G · K _X", the command value "X _G · K _X" for most phase lag and gain reduction without passing to the drive circuit 66FL~66RR Sent. From this, in such a moderate turning and straight state, since the anti-pitch moment in response to occurrence of the longitudinal acceleration X _G is obtained, by moving the wheel load, the vehicle body posture is almost held flat.

On the other hand, in a sharp turning state where the lateral acceleration | Y _G | exceeds the predetermined value Y _G1 , the cutoff frequency f _C of the low-pass filter 62 is reduced according to the magnitude | Y _G |. Therefore, the command value to be input to the low pass filter 62 to the "X _G · K _X", since the phase delay and gain reduction amount corresponding to the decrement of the cut-off frequency f _C is generated, is output from the drive circuit 66FL~66RR that the command current i _FL through i _RR also with a phase delay with respect to the longitudinal acceleration X _G, and becomes a smaller value than when not inserted filter 62.

As a result, the hydraulic cylinders 18FL to 18RR generate the anti-pitch moment with a delay, and the moment is also smaller by the filter gain reduction than when the filter 62 is not inserted. Therefore, acceleration during a sharp turn,
Although a slight pitch is generated due to the deceleration, the movement of the wheel load in the front-rear direction is also positively delayed, so that a sudden change in the steering characteristic can be reliably avoided.

In the above-described second embodiment, the lateral acceleration | Y _G | ≦ Y _G1
, The cut-off frequency f _C is equal to the predetermined value f _C1 . However, when | Y _G | ≦ Y _G1 , the output of the gain adjuster 60 is “X _G · K _X "drive circuit
Direct output to 66FL to 66RR (including inverter 68), | Y _G |> Y _G1
, A low-pass filter 62 is inserted between the gain adjuster 60 and the driving circuits 66FL to 66RR (including the inverter 68), and
The cutoff frequency f _C may be reduced in inverse proportion to | Y _G |. As a result, in the state of | Y _G | ≦ Y _G1 , the pitch control can be prioritized without a slight phase delay and gain reduction due to the filter.

In addition, the turning state detecting means of the present invention may be configured to detect the vehicle speed V and the steering wheel steering angle θ and to estimate the lateral acceleration from the detected values, in addition to the above-described configuration. Alternatively, the turning state may be determined directly using the steering wheel angle θ.

Further, the working fluid of the active suspension according to the present invention is not limited to the working oil, but may be a gas. Further, the control valve may be configured to control the operation flow rate of the fluid cylinder.

〔The invention's effect〕

As described above, according to the invention described in the claims, a signal such as a lateral acceleration corresponding to the turning state is detected, and the pitch control gain is changed according to the detected value (for example, when the signal such as the lateral acceleration increases). The pitch control gain is reduced) and the output of the command value to the control valve is delayed in accordance with the detected value. Therefore, the pitch motion that occurs during acceleration / deceleration running during straight traveling is accurately suppressed, and the vehicle is almost flat. While the posture is maintained, the amount of load movement between the front and rear wheels can be positively reduced or delayed during acceleration or deceleration during a turn, which allows for steering such as tack-in during braking and understeer during initial acceleration. Changes in properties are reliably eliminated.

[Brief description of the drawings]

1 (a) and 1 (b) are views corresponding to claims of the present invention. 2 to 6 are views showing a first embodiment,
FIG. 2 is a schematic configuration diagram of an active suspension, FIG. 3 is an output pressure characteristic diagram of a pressure control valve, FIG. 4 (a) is a detection characteristic diagram of a lateral acceleration sensor, and FIG. 4 (b) is a longitudinal acceleration sensor FIG. 5 is a block diagram of a controller, and FIG.
The figure is a graph showing an example of a change in the pitch control gain with respect to the lateral acceleration. 7 and 8 show the second embodiment. FIG. 7 is a block diagram of the controller, and FIG. 8 is a graph showing an example of a change in the cutoff frequency of the low-pass filter with respect to the lateral acceleration. The main symbols in the figure are: 10: body side member, 12: active suspension, 16: wheel side member, 18FL-18RR ... hydraulic cylinder, 20FL-20RR ... pressure control valve, 26 ... lateral acceleration Sensor, 27: longitudinal acceleration sensor, 30: controller, 50: gain adjuster, 52: inverter, 54: absolute value circuit, 56: FL to 56RR: drive circuit, 60: gain adjustment , 62 …… Low-pass filter, 64 …… Absolute value circuit, 66FL
6666RR: a drive circuit; 68: an inverter.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Itaru Fujimura 2nd Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Kensuke Fukuyama 2 Takaracho, Kanagawa-ku Yokohama-shi, Kanagawa (56) References JP-A-62-295714 (JP, A) JP-A-63-11408 (JP, A) JP-A-2-95911 (JP, A) JP-A-63-232014 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) B60G 17/015

Claims (2)

(57) [Claims] 1. A fluid cylinder interposed between a vehicle-side member and a wheel-side member, a control valve for controlling a working fluid supplied to the fluid cylinder in accordance with a command value, and a front and rear for detecting a longitudinal acceleration of the vehicle. Acceleration detection means, command value calculation means for calculating a command value for suppressing the pitch of the vehicle based on the product of the detected value of the longitudinal acceleration detection means and the pitch control gain, and outputting the calculated value to the control valve; An active suspension comprising: a turning state detecting means for detecting a signal corresponding to a turning state of a vehicle; and a control gain changing means for changing the pitch control gain in accordance with a detection value of the turning state detecting means. Active suspension characterized by that. 2. A fluid cylinder interposed between a vehicle body-side member and a wheel-side member, a control valve for controlling a working fluid supplied to the fluid cylinder in accordance with a command value, and a front and rear for detecting a longitudinal acceleration of the vehicle. Acceleration detection means, command value calculation means for calculating a command value for suppressing the pitch of the vehicle based on the product of the detected value of the longitudinal acceleration detection means and the pitch control gain, and outputting the calculated value to the control valve; A turning state detecting means for detecting a signal corresponding to a turning state of the vehicle, and a command value output from the command value calculating means to the control valve in accordance with a detection value of the turning state detecting means. An active suspension characterized by comprising a control delay means for delaying the delay.