JP2611446B2 - Active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention includes a control valve for controlling the operation of a fluid cylinder inserted between a vehicle body and wheels in accordance with a change in posture, and supplies a control valve with a solenoid for the control valve. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active suspension in which a high-frequency dither signal is superimposed on a command current to be performed, and more particularly to a device having a mechanism for detecting an abnormal state of a solenoid and a solenoid drive circuit.

[Conventional technology]

An example of this type of active suspension is disclosed in Japanese Patent Application No. 1-10082 (not disclosed) filed by the present applicant.

This active type suspension includes a fluid cylinder such as a hydraulic cylinder arranged on each wheel, a control valve such as a pressure control valve for controlling the operation of the fluid cylinder, and a posture change such as an acceleration detector for detecting a posture change of the vehicle body. A detection means, and a posture change control means for calculating a command value for suppressing a change in the posture of the vehicle body based on the detection value of the detection means and supplying the calculated command value to the solenoid of the control valve in the form of a command current. Here, the attitude change control means may supply a high frequency dither signal D superimposed on the command current i as shown in FIG. 14, for example, with a view to reducing hysteresis and avoiding the fluid sticking phenomenon. The solenoid thrust generates a force proportional to the average current of the command current (excitation current) i. Further, in such an active suspension, a state in which the specified pressure value S is constant (for example, when the vehicle is stopped) is detected by the constant current detecting means, and the actual value of the command current i flowing through the solenoid is detected by the current detecting means. When the constant current detecting means detects a constant value of the command current, the detection value i of the current detecting means and the command value S of the attitude change control means are changed in a state where the superposition of the dither signal D is interrupted. If the difference between the two is greater than or equal to the set value, the apparatus is provided with an abnormality detecting unit that determines that the state is abnormal.

As described above, when the abnormality (failure) is detected, the dither signal is turned off, so that the failure of the solenoid and the solenoid drive circuit can be accurately determined.

[Problems to be solved by the invention]

In the above-described configuration, even when the dither signal D is superimposed, if the load supplying the command current i is a pure resistance load, the command current i and the load current have the same waveform as shown in FIG. Is equal to the current value corresponding to the command value S, and there is no problem.

However, in actuality, the command current i changes as shown in FIG. 14 due to the inductive load component of the solenoid, and the rounding is not symmetrical in the increasing / decreasing direction. Since a difference ΔI is generated from the command current i (average value) when the signal D is superimposed, a failure detection timing, for example, when the vehicle is stopped, has arrived. In this case, the solenoid thrust, that is, the cylinder pressure changes stepwise due to the above-mentioned difference value ΔI, and the vehicle body posture changes suddenly, which may cause discomfort and anxiety to the occupant.

The present invention has been made in view of the above-mentioned unsolved problems, and maintains the high-precision failure (abnormality) detection described in the prior application as it is, and also prevents a sudden change in the vehicle body attitude at the time of such failure detection. That is the problem to be solved.

[Means for solving the problem]

In order to solve the above-mentioned problems, each invention of this application is a first invention.
As shown in the figure, a fluid cylinder inserted between the vehicle body and wheels, a control valve having a solenoid for receiving a command current and controlling the working fluid supplied to the fluid cylinder in accordance with the command current, Attitude change detection means for detecting a change in attitude of the vehicle body, attitude control means for calculating a command value for suppressing the attitude change of the vehicle body based on the detection information of the attitude change detection means, and outputting a command current to the control valve, A command for detecting an actual value of a command current supplied to a solenoid of the control valve in an active suspension including a dither signal superimposing means for superimposing a high frequency dither signal on a command current output from the attitude control means. Current detection means, non-control state detection means for detecting a non-control state of the attitude control means, and when the non-control state detection means detects a non-control state of the attitude control means. Dither signal reducing means for gradually reducing the amplitude value of the dither signal to zero, and after the dither signal is reduced to zero by the dither signal reducing means, the detection value of the command current detecting means is compared with the command value. An essential part thereof is provided with abnormality determination means for determining whether or not the state is abnormal based on whether or not the difference between the two is equal to or more than a predetermined value.

[Action]

The main part of the operation in each invention of the present application is as follows. The non-control state detecting means is the non-control state of the attitude control means,
For example, when a stop is detected, the dither signal reducing unit gradually lowers the amplitude value of the dither signal to zero, thereby cutting off the superposition of the dither signal. Thereafter, the abnormality determining means compares the detected value of the command current detecting means, that is, the value actually supplied to the solenoid of the control valve with the command value, and determines whether the difference between the two is greater than or equal to a predetermined value. It is determined with high accuracy whether or not the means is in an abnormal state. For this reason, a sudden change in posture caused by cutting off the dither signal stepwise when determining an abnormal state is reliably prevented.

〔Example〕

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 2, 10FL to 10RR indicate front left to rear right wheels,
Denotes a wheel side member connected to each of the wheels 10FL to 10RR, and 14 denotes a vehicle body side member. A hydraulic active suspension 16 is provided between each wheel side member 12 and the vehicle body side member 14.

The active suspension 16 includes a hydraulic pressure supply device 18 as a fluid pressure supply device, an operating pressure holding unit 20 and a fail-safe valve 22 interposed on the load side of the hydraulic pressure supply device 18, and a load of the fail-safe valve 22. Accumulators 24, 24 mounted on the front and rear wheel sides, pressure control valves 26FL-26RR mounted on wheels 10FL-10RR, and hydraulic cylinders (fluid cylinders) 28FL-28RR as loads And Also, the active suspension 16 is an acceleration detector
30, a vehicle speed detector 31, and command currents i,..., I to the pressure control valves 26FL to 26RR based on the detection signals of the two detectors 30, 31, and the fail-safe valve 22 via a drive circuit 32. It has a controller 33 for controlling and a warning light 34 connected to the controller 33. In the drawing, reference numeral 39 denotes a coil spring for supporting a static load of the vehicle body.

The hydraulic supply device 18 includes a reservoir tank 40 that stores hydraulic oil, and a hydraulic pump 42 that uses an engine as a rotational drive source.
And a relief valve 44 for setting a predetermined line pressure.
That is, the supply pipe 48s and the return pipe 48r are provided in the tank 40.
Is connected, and the supply-side pipe line 48s reaches the operating pressure holding unit 20 at the next stage via the hydraulic pump.

Operating pressure holding unit 20 includes a check valve 50 inserted into the supply-side pipe 48s, operate check valve the load side pressure and are inserted in the return side pipe 48r said fail-safe valve 22 and pilot pressure P _P 52 And Operate check valve
52, the pilot pressure P _P is the set value (in this case, working neutral pressure
(P _N : see Fig. 3). The pilot-operated check valve has a structure in which the valve is opened and the check is released when it exceeds the value.

Also, a return line 48 upstream of the operation check valve 52 is provided.
r is provided with a bypass path 48B that is inserted through the stop 54 and bypasses the stop 54.

As shown, the fail-safe valve 22 is a check valve.
At a position downstream of 50, its pump port P and port A
Is connected to the supply line 48s and the tank port T
And a 4-port 2-position solenoid-operated directional control valve connected to the bypass line 48B. When the switching signal CS given to the electromagnetic solenoid 22 is off (when an abnormality occurs), the pump port P and the port A and the port B and the tank port T are shut off, and the port A and the port B are disconnected. On the other hand, when the switching signal CS is ON (during normal operation), the pump port P to the port A and the port B to the tank port T are connected to each other.

Therefore, when the engine is not rotating, the discharge pressure of the hydraulic pump 42 is also zero, and the operating check valve
Since 52 is closed, the load-side hydraulic path is enclosed in the neutral pressure P _N by operate check valve 52 and the check valve 50. Further, when the suspension is in a normal control state and the fail-safe valve 22 individually communicates the supply pipe 48s and the return pipe 48r as described later, the discharge that rises with the rotation of the engine is increased. pressure becomes operate check valve 52 is opened at the time of exceeding the working neutral pressure P _N, the line pressure which is determined by the relief valve 44 is supplied to the load side.

Supply side pipeline 48s downstream of the fail-safe valve 22
Are branched corresponding to the front wheels 10FL and 10FR and the rear wheels 10RL and 10RR. Then, after each pipe 48s is connected to the accumulator 24 having a relatively large capacity, the pipes further branch off corresponding to the left and right wheels to reach the supply ports of the pressure control valves 26FL to 26RR. As shown in the figure, the return ports of the pressure control valves 26FL to 26RR join the left and right wheels and then join the front and rear wheels to reach the operation check valve 52.

On the other hand, each of the pressure control valves 26FL to 26RR includes a valve housing having a spool slidable in the insertion hole, and a pilot pressure applied to the other end corresponding to the feedback pressure applied to one end of the spool. And a proportional solenoid valve (for example, see Japanese Patent Application Laid-Open No. 1-122717) having a well-known proportional solenoid valve having a proportional solenoid that can adjust the pressure. Of the three ports, the supply port and the return port are connected to hydraulic pipes 48s and 48r, and the output port is connected to the pressure chambers L of the hydraulic cylinders 28FL to 28RR via the hydraulic pipe 60. Therefore, by adjusting the command current i supplied to the proportional solenoid, the position of the spool can be controlled, and the control pressure P output from the output port P can be controlled.

Here, the relationship between the command current i and the control pressure P is as shown in FIG. The control pressure P also becomes zero when the command current i is zero, the command current i from this state increases, the control pressure P also increases in proportion thereto, when the maximum command current i _M, the set line pressure the maximum control pressure P _L corresponding. i _N and P _N are the command current and control pressure during neutral operation.

As shown in FIG. 2, each of the hydraulic cylinders 28FL to 28RR has a cylinder tube 28a, in which a lower pressure chamber L separated by a piston 28c is formed. And the cylinder tube 28a
Is attached to the wheel side member 12 and the piston rod
The upper end of 28b is attached to the vehicle body side member 14. Each pressure chamber L is connected to an unsprung resonance region (e.g.
10 Hz) is connected to a small-capacity accumulator 63 for absorbing hydraulic vibration.

On the other hand, the acceleration detector 30 is provided at a predetermined position on the vehicle body, detects accelerations in the lateral, front and rear, and vertical directions of the vehicle body, and outputs an acceleration signal G (positive / negative) corresponding to these accelerations having positive and negative analog voltage amounts. In this case, the detection signal G is also zero) is output to the controller 33. Vehicle speed detector 31
Detects the rotational speed of the output shaft of the transmission magnetically and optically, and outputs a pulse signal VL corresponding to the vehicle speed to the controller 33.

The controller 33 includes a microcomputer 66 for arithmetic processing, an A / D converter 68 on the input side of the microcomputer 66 for A / D converting the acceleration detection signal G, and a waveform shaping circuit 70 for the vehicle speed detection signal VL. On the other hand, the pressure command values SA,.
D / A converters 72A to 72D for D / A conversion, and the D / A converters 72A to 72D
Drive circuits 74A to 74, each of which is a constant current circuit that supplies a command (excitation) current i,..., I corresponding to the target value to the solenoid 26A of each of the pressure control valves 26FL to 26RR, using the converted output of 72D as a target value.
D and command currents i,..., I supplied by the drive circuits 74A to 74D.
A voltage signal v _R corresponding to A / D conversion and an A / D converter 76A~76D supplied to the microcomputer 66.

The microcomputer 66 has an interface circuit 7
6, comprising a main processing unit 78, a sub-processing unit 79, a storage unit 80, and a clock generator 82.
The main and sub processing units 78 and 79 read a program stored in the storage device 80 in advance, and perform calculation and control (to be described later).
(See Figures 6 and 7) individually.

As shown in FIG. 5, each of the drive circuits 74A to 74D
An operational amplifier 84 receiving the output voltage of the A converter 72A (to 72D) at a non-inverting terminal, an NPN transistor 85 having a base connected to the output side of the operational amplifier 84, and an emitter connected to the emitter of the transistor 85 and ground. And the collector of the transistor 85 is connected to the pressure control valve 26FL.
Via a proportional solenoid 26A of (~26RR) is connected to the positive power supply V _B. The connection point between the emitter of the transistor 85 and the resistor R is connected to the inverting terminal of the operational amplifier 84 and to the microcomputer 66 via the A / D converter 76A (-76D). Therefore, the proportional solenoid 26
A voltage v _R corresponding to an exciting current (command current) i flowing through A is obtained on the power supply side of the resistor R, and this voltage v _R is fed back to the microcomputer 66 and the operational amplifier
84 is controlled so that the detection voltage v _R and pressure specified value SA (analog value) is equal.

A drive circuit 32 for driving the fail-safe valve 22
Includes a transistor which is turned on and off by receiving a switching signal CS controller 66 outputs, thereby interposed a solenoid 22A between the transistor and the positive power supply V _B.

 Next, the operation of this embodiment will be described.

First, when the key switch is set to the accessory position, the controller 33 is activated, whereby the main processing unit 78 executes the processing shown in FIG. 6, and in parallel with this, the sub-processing unit 79 The program for determining the carrier frequency is driven, and the processing shown in FIG. 7 is executed.

First, the processing in FIG. 6 will be described. Main processor 78
Is the switching signal CS =
On, the initial value is set to the maximum voltage amplitude value d _m = α (> 0) and the determination end flag FS = 0.

Next, the process proceeds to step S, where the main processing unit 78 reads the vehicle speed detection signal VL via the interface circuit 76, calculates the vehicle speed V by measuring the number of pulses per unit time, and stores the value. Then, the process proceeds to a step, where it is determined whether or not the vehicle is stopped based on the vehicle speed calculation value V. This determination is made based on whether or not the vehicle speed V has reached a set value (for example, 2 km / h) that can be regarded as a value at the time of stopping. As a result, when the vehicle is in the stopped state, the process of the step is performed.

In the step, it is determined whether or not a determination end flag FS indicating whether or not an abnormality (failure) determination process described later has been completed is "1". If FS = 0, it is determined that the abnormality determination process has not been performed yet. Move to step.

In the step, the main processing unit 78 determines whether or not the dither signal D is zero by determining whether or not a half-cycle maximum voltage amplitude value d _m = 0, which will be described later, is “NO”, that is, If it is assumed that the amplitude value d _{m 、} 0 and the dither signal D is superimposed, the process proceeds to the next step. In this step, after reducing the maximum voltage amplitude value d _m by a predetermined small amplitude [Delta] d _1, the flow returns to step. Here, small amplitude [Delta] d ₁ is the vehicle height change rate due to changes in the average current command current i, the value at the same time becomes gentle and normal vehicle height adjustment speed is selected (see FIG. 8) .

Decreased dither amplitude d _m gradually by repeating the process of step ~ "YES" in step, i.e. when the dither signal D is determined to become zero, then the process of step ~. First, in the step, the determination end flag FS = 1, and in the step, the voltage detection signals v _R ,..., V _R corresponding to the actually supplied command currents i,.
The values are read via the A / D converters 76A to 76D and the interface circuit 76, respectively, and the values are temporarily stored. In the step,
Readings of step v calculates a command current i based on _R. Further, in the step, a pressure designation value S,.
, I (current value) corresponding to the (voltage value) are calculated by referring to a table or the like.

Further, in the step, the operation value I, i of the step
Is obtained from the calculation of | I−i | = ΔI, and in a step, it is determined whether or not the obtained difference value ΔI is smaller than a predetermined reference value e. Here, the reference value e is a minute value that can discriminate an abnormal (failure) state in which the pressure command is not made as commanded by the command value S due to a failure of the drive circuits 74A to 74D, a disconnection of each solenoid 26A and a harness, or the like. Is set to a value. Note that the abnormality determination in the step may be performed with the voltage value unchanged.

Therefore, when the determination of “YES” is made in the step, the normal operation state is determined, and the switching signal CS to the fail-safe valve 22 is kept on in the step, and the warning light 34 is kept turned off in the step. Return to If “NO” is determined in the step, it is determined that an abnormal condition has occurred, the switching signal CS is turned off in the step, the warning light 34 is turned on, and then the control is stopped.

On the other hand, if the vehicle is in a stopped state during the repetition of the above-described processing, but the abnormality determination processing has already been completed, the determination of “YES” is made in step and the processing proceeds to step. In the step, contrary to the above step, the processing of the maximum voltage amplitude value d _m = d _m + Δd ₁ is performed, and the amplitude value d _m is slightly increased for each processing. Thereafter, the maximum voltage amplitude value d _m is determined whether reaches a predetermined set value α in step, "N
As in the case of O "is being slightly the amplitude value d _m, the flow returns to step. Conversely, if “YES”, step,
Is performed.

That is, the main processing unit 78 reads the acceleration detection signal G via the A / D converter 68 and the interface circuit 76 at the step, and at step S, the pressure command value S for each wheel.
.., S are calculated using voltage values. In this calculation, the lateral acceleration and the longitudinal acceleration are multiplied by a predetermined control gain, respectively, and the vertical acceleration is integrated to obtain the vehicle speed. The vehicle speed is multiplied by the control gain, and the vehicle speed is multiplied by the control gain. Is added together with the vehicle height adjustment command value for each wheel. At this time, regarding the attitude control, each command value is added so that the cylinder operating force is in a direction against the attitude change. Thereafter, the process returns to the step.

On the other hand, if it is determined in the above step that the determination is "NO", that is, the vehicle is in the running state, the determination end flag FS is determined in the step.
Is cleared and the process proceeds to the step. In this step, similarly to the step, as the maximum voltage amplitude value d _m is determined whether reaches a predetermined set value alpha, the case of "NO" is insufficient amplitude value d _m, in step, adding a large amplitude [Delta] d ₂ than the small amplitude value [Delta] d _1. Thus, after increasing the increasing speed of the dither amplitude, the processing of the above-described steps is performed.

 Next, the processing of FIG. 7 will be described.

The sub-processing unit 79 operates independently in the step shown in the figure from the time of startup, and has logical values “1” and “1” corresponding to the carrier frequency (for example, 100 Hz to 400 Hz) of the dither signal D. The rectangular wave signal CR taking "0" is read, and the process proceeds to the step. In this step,
Secondary processing unit 79 reads the main processor 78 is the value of the latest dither amplitude value d _m set in the process of Figure 6. Further, the process proceeds to step S, where the main processing unit 78 reads the latest pressure command values S,..., S set in the processing of FIG.

Next, the process proceeds to a step where the dither signal D is superimposed on each pressure command value S. That is, the square wave signal CR has the logical value “1”.
Is taken, the latest pressure command value S is replaced with the latest amplitude value.
adding d _m, when a logical value "0", by subtracting the latest amplitude value d _m from the latest pressure command value S, the total pressure command value SA obtained by superposing the dither wave, ..., each wheel the SA Ask every time.

Next, the process proceeds to the step, and after outputting the total pressure command values SA,..., SA obtained in the step to the D / A converters 72A to 72D, returns to the step and repeats the above processing until the power is turned off. This repetition is performed at the same or faster cycle as the carrier of the dither signal D.

In this embodiment, the acceleration detector 30, the A / D converter 68 and the sixth
The processing in the figure steps constitutes a posture change detecting means,
Steps in FIG. 7 and FIG. 7 and D / A converter 7
2A to 72D and the driving circuits 74A to 74D constitute the attitude control means, and the processing of Steps 1 to 7 in FIG. 7 constitute the dither signal superimposing means. The processing in the vehicle speed detector 31, the waveform shaping circuit 70 and the steps in FIG. 6 constitute the non-control state detecting means, and the processing in the steps in FIG. 6 constitute the dither signal reducing means. 6 constitutes the dither signal increasing means, and the processing of the A / D converters 76A to 76D and the step of FIG. 6 constitute the command current detecting means. Is composed.

 Next, the overall operation will be described.

Now, it is assumed that no abnormality such as disconnection has occurred in the system that gives the command current i, and the system is traveling straight at a constant speed on a good road. During this traveling, the switching signal CS is kept on by the above-mentioned initial setting in FIG. 6, and the maximum amplitude value d _m of the dither signal = the set value α.
It has become. That is, the port P of the fail-safe valve 22
-A and the ports BT are connected respectively, and a predetermined line pressure is supplied to the supply port side of each of the pressure control valves 26FL to 26RR, according to a command current i on which a dither wave D having a predetermined amplitude α is superimposed. Thus, the cylinder pressure can be controlled.

In this state, the main processing unit 78 outputs the vehicle speed detection signal VL
Is higher than the set value, so that the processing is performed through the steps of FIG. In other words, when traveling straight at a constant speed on a good road, the pressure command value that includes only the vehicle height command value
S, ..., S are set. Then, the sub-processing unit 79 calculates and outputs the total pressure command value SA in which the dither wave D is superimposed on each pressure command value S by executing the processing of FIG.

Each of the total pressure command values SA is a D / A converter 72A to 72D.
Are individually converted to analog quantities and set as the target value in the drive circuit
Output to 74A-74D. Therefore, the driving circuits 74A to 74D
The command current i supplied to the proportional solenoids 22A of the pressure control valves 26FL to 26RR is made to follow the value corresponding to the target value. For this reason, in the current constant speed straight traveling state, the command current i becomes a value corresponding to the vehicle height control command value, and the control pressure P corresponding to the command current i is supplied to each of the hydraulic cylinders 28FL to 28RR. A flat vehicle posture is maintained by the control pressure P.

In addition, the vehicle travels around the road or accelerates or decelerates, and the acceleration signal G
Is detected, a posture control command value in a direction against a change in posture is also added to the pressure command value S, and the cylinder pressure is controlled. As a result, the roll, pitch, and bounce are controlled, and a flat vehicle height value is maintained.

Further, it is assumed that the vehicle stops in the idling state from the running state. In this state, the switching signal CS = ON and the dither amplitude d _m = α are still held, the command current i according to the vehicle height command value is being output, and vehicle height control is maintained.

Therefore, the main processor 78, "YES" in step sixth view, steps in determining the "NO", the dither amplitude d _m is decreased by [Delta] d ₁ in step. This process
The process is repeated until the dither amplitude d _m = 0, that is, the dither signal D becomes zero, so that the decreasing rate of the dither amplitude becomes small as shown in FIG. That is, the vehicle height change accompanying the decrease in the average value of the command current i becomes very slow, and as described in the prior application, the dither wave D is suddenly reduced to zero, so that the presence or absence of the dither wave D Abrupt changes in the command value can be eliminated, and as a result, the occupant is not given unnecessary discomfort and anxiety.

Then, when the dither wave D becomes zero, an abnormality (failure) determination process of steps 1 to 6 in FIG. 6 is performed. That is,
When the detected command (excitation) current i substantially coincides with the current command value I corresponding to the pressure command value S, it is determined that there is no abnormality, the switching signal CS is turned on, the warning lamp 34 is kept off, and control is continued. .

On the other hand, if a disconnection or a contact failure has occurred and the command current i deviates from the allowable value e, it is regarded as an abnormal state and the switching signal
CS is turned off, and the warning light 34 is turned on. As a result, the cylinder ports A and B of the fail-safe valve 22 are connected, and the high-pressure hydraulic oil remaining in the supply pipe 48s and the accumulator 24 is diverted to the return pipe 48r. At this time, due to the presence of the restrictor 54, a back pressure is generated in the pressure control valves 26FL to 26RR, and the high-pressure hydraulic oil is temporarily sealed. afterwards,
Since the hydraulic oil gradually flows into the tank 40 via the throttle 54 and the operation check valve 54, the operating pressure on the load side also gradually decreases. Then, when the supply pressure to the pressure control valve 26FL~26RR is lowered to the neutral value P _N, confines the load side is closed operate check valve 52 substantially state of the neutral pressure P _N. As a result, the subsequent posture and vehicle height control are not effective, but the next best posture at the time of a failure occurrence is maintained, and traveling can be continued by the function of the conventional passive suspension. This abnormal occurrence,
When the warning light 34 is lit, the occupant is notified.

That is, in this embodiment, similarly to the description of the prior application, the abnormality determination is performed in the stopped state where the attitude control is not necessary and in the state where the dither wave D is discontinued. As a result, it is needless to say that the attitude control is not hindered at all, and the threshold value e of the abnormality determination can be set small because it is not affected by the inductance of the solenoid, the variation of the high-frequency response of each component, and the like. Accordingly, highly accurate abnormality detection can be performed.

On the other hand, if there is no abnormality in the abnormality determination, the control is continued unless the power is turned off. Then, once an abnormality determination is made in the stopped state, the determination end flag FS = 1, so the processing of FIG. 6 is performed via steps. Therefore, the dither amplitude value d _m is gradually increased as shown in Figure 8 back to its original value alpha, also performs normal attitude control after returning.

However, if the vehicle starts suddenly while the amplitude of the dither wave D is slightly increasing, the vehicle speed V increases.
, And enters the normal attitude control. That is, the dither amplitude value is rapidly increased by Δd ₂ in steps, and the posture control is performed while increasing the change speed. As a result, the dither amplitude quickly returns to the normal value α, and more accurate attitude control can be performed quickly, so that attitude changes such as scat can be accurately suppressed. At this time, since the vehicle height change caused by the sudden increase of the dither amplitude is under posture control, there is an advantage that the occupant does not feel uncomfortable in most cases.

By the way, cutting off the dither wave even when the vehicle is stopped as in this embodiment is also effective in suppressing the generation of sound caused by the dither wave. In other words, superimposing a dither wave means that a small pressure change is always occurring, and this pressure change may cause the hydraulic piping system to vibrate and generate sound. In particular, when the resonance point of the hydraulic piping system changes due to hardening of the mount member or the like, the vibration noise may increase. However, while driving, it is masked by other noises, such as road noise, so it is hardly noticed by the occupants. However, the generation of such noises when the vehicle is stopped in a quiet environment is particularly unpleasant. give. On the other hand, in the present embodiment, the dither amplitude is temporarily reduced and the state of zero is maintained for the purpose of diagnosing a failure when the vehicle is stopped. Therefore, it is effective for suppressing such noise and contributes to improvement of the vehicle performance.

In this embodiment, it is also possible to adopt a mode in which the decreasing speed and the increasing speed of the dither amplitude are made the same by setting Δd ₁ = Δd ₂ as necessary. Further, by minimizing the minute values Δd ₁ and Δd ₂ as much as possible, it becomes equivalent to the monotone decrease and the monotone increase shown in FIG. 9 (corresponding to the operation in FIG. 8 described above).

Second Embodiment Next, a second embodiment will be described. The hardware configuration is the first
The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.

In the second embodiment, the amplitude of the dither signal D is adjusted by adjusting the carrier frequency of the dither signal D. To explain this principle, each drive circuit 74A
Since the load of .about.74D is inductive by the proportional solenoid 26A, the step response of the command current i to the rectangular change of the total pressure command value SA is a response that changes gradually as shown in FIG. That is, if the carrier frequency f of the dither wave is low, the peak value of the command current i increases, and the dither amplitude can be increased.
Is higher, the cycle changes before the peak value reaches the predetermined peak value due to the response delay of the load, and eventually the peak value of the command current i is low, and the dither amplitude can be reduced.

Therefore, in the second embodiment, while performing the processing shown in FIG. 6 showing the operation of the first embodiment, in that step, the carrier frequency f is changed from a predetermined frequency to a level where the pulsation of the command current i can be almost ignored. executing instructions gradually increasing in width Delta] f _1, as opposed to in step, may be performed an instruction to gradually reduce in width Delta] f ₁ carrier frequency f to the original predetermined value (also in this case the sixth In the processing corresponding to the steps in the figure, the carrier frequency f is set to the width Δf ₂
(> Δf ₁ ). On the other hand, the 7 performs processing diagram Ban therewith (at step corresponding to process in the figure, a dither amplitude value d _m is always a constant value α is read).

Therefore, the dither amplitude can be substantially increased or decreased by increasing or decreasing the carrier frequency f, that is, the frequency of the rectangular wave signal CR, and the same operation and effect as in the first embodiment can be obtained.

In addition, as the control method particularly considering the prevention of the noise in the stopped state described above, in addition to the control method of each embodiment described above,
Some are shown in Figure 2. In FIG. 11, the dither amplitude is reduced by Δd at the same time as when the vehicle is stopped, and the dither amplitude is set to a level at which the sound is not bothersome. Thereafter, the dither amplitude is smoothly reduced. In FIG. 12, after shifting to the stop state, the carrier frequency f of the dither wave is increased or decreased, and once the resonance point of the hydraulic piping system is removed to prevent the generation of sound, the dither is gradually reduced. The amplitude is reduced.

Further, the inventions of this application are not limited to those using hydraulic oil as the working fluid, but may use, for example, air. An electromagnetic flow control valve for controlling the flow rate of the liquid may be applied.

Further, the non-control state detecting means in each invention of this application detects a stop state as in the above-described embodiment, and further, a command value to a control valve such as when the vehicle is traveling straight, when turning a steady circle, or the like, has a fixed value. The state to be maintained may be detected, and an abnormality may be determined when such a state is detected.

Furthermore, the dither signal superimposing means in each invention of this application is realized by analog electronic circuits such as a dither signal generator, a variable gain amplifier, and an addition circuit in addition to those realized by the software of the computer as in each of the above embodiments. Then, the amplitude value may be adjusted by changing the gain of the variable gain amplifier, or a variable frequency dither signal generator and an addition circuit may be used to increase or decrease the carrier frequency of the dither signal generator.

〔The invention's effect〕

As described above, according to the invention of the present application, the amplitude value of the dither signal superimposed on the command value is gradually reduced, and after the dither signal is reduced to zero, the solenoid of the control valve and the attitude control means are controlled. Abnormality (failure) of solenoid drive circuit etc.
Is determined, the highly accurate abnormality detection described in the prior application can be maintained, and a sudden change in the vehicle body posture due to the cutoff of the dither signal at the time of the abnormality detection can also be prevented. Note that the amplitude value of the dither signal can be reduced by directly changing the amplitude by a small value or by changing the carrier frequency, thereby increasing the range of choices at the time of design.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims common to each invention, FIG. 2 is a schematic configuration diagram showing one embodiment of each invention, FIG. 3 is a graph showing an output characteristic with respect to a command current of a pressure control valve, and FIG. FIG. 5 is a block diagram of the controller, FIG. 5 is a circuit diagram showing a drive circuit for one system, FIGS. 6 and 7 are schematic flowcharts showing an example of processing by the microcomputer of the controller, and FIG. 9 is a graph showing another example of the degree of adjustment of the dither signal, FIG. 9 is a graph showing another example of the degree of adjustment of the dither signal, FIG. 10 is a step response graph showing the principle of adjusting the dither amplitude in the second embodiment, and FIG. FIGS. 12 and 13 are graphs showing other examples of the degree of adjustment of the dither signal, FIG. 13 is a graph showing the state of a dither signal flowing to a pure resistance load, and FIG. 14 is a state of a dither signal flowing to an inductive load. FIG. In the figure, 12 is a wheel side member, 14 is a vehicle body side member, 16 is an active suspension, 26FL to 26RR are pressure control valves (control valves), 28
FL to 28RR are hydraulic cylinders (fluid cylinders), 30 is an acceleration detector, 31 is a vehicle speed detector, 33 is a controller, 66 is a microcomputer, 78 is a main processing unit, and 79 is a sub-processing unit.

Claims (3)

(57) [Claims] 1. A control valve having a fluid cylinder interposed between a vehicle body and wheels, a solenoid for receiving a command current, and controlling a working fluid supplied to the fluid cylinder in accordance with the command current; Attitude change detecting means for detecting a change in the attitude of the vehicle body, attitude control means for calculating a command value for suppressing the change in the attitude of the vehicle body based on the detection information of the attitude change detection means and outputting a command current to the control valve, A command current for detecting an actual value of a command current supplied to a solenoid of the control valve, in an active suspension including a command current output from the attitude control means and a dither signal superimposing means for superimposing a high-frequency dither signal. Detecting means, a non-control state detecting means for detecting a non-control state of the attitude control means, and when the non-control state detecting means detects a non-control state of the attitude control means, Dither signal reducing means for gradually reducing the amplitude value of the dither signal to zero, and after the dither signal is reduced to zero by the dither signal reducing means, the detection value of the command current detecting means is compared with the command value. And an abnormality judging means for judging whether or not there is an abnormal state based on whether or not the difference between them is equal to or more than a predetermined value. 2. The active suspension according to claim 1, wherein said dither signal reducing means is configured to reduce the amplitude of the dither signal by a predetermined width. 3. The active suspension according to claim 1, wherein said dither signal reducing means gradually increases the carrier frequency of the dither signal.