JP2580818B2 - Suspension control device - Google Patents

Description

Description: Object of the Invention [Industrial application field] The present invention relates to a suspension control device, and in particular, can detect a failure of a suspension means or the like that can change characteristics such as a generation pattern of a damping force and a spring constant. Suspension control device.

[Prior Art] As a suspension control device capable of changing suspension characteristics, a suspension control device that incorporates an actuator using a piezoelectric element as a drive source in a shock absorber or the like and switches the damping force characteristics of the shock absorber based on a signal from a load sensor is known. It is known (for example, JP-A-64-67407). Since the piezoelectric element is extremely excellent in responsiveness, when used as a characteristic switching actuator such as a shock absorber, the characteristics can be switched at high speed even when the vehicle crosses a step, and the riding comfort can be kept good. . In order to sufficiently bring out the characteristics of such an actuator, a highly responsive sensor is required. Conventionally, a load sensor using a piezoelectric element and a damping force change rate detection sensor integrated with a piezoelectric actuator have been proposed (for example, JP-A-63-6238).

Since the piezoelectric element has a small output voltage per unit element and a small amount of deformation with respect to the voltage, a plurality of elements are generally stacked and used as a stack.

[Problems to be Solved by the Invention] However, if such a piezoelectric element is deteriorated due to aging or abnormal due to cracks, or if a high-voltage circuit for driving the piezoelectric actuator is broken, the suspension characteristics may be reduced to a desired value. There was a problem that the state could not be controlled. In addition, the measures to be taken differ depending on whether the sensor using the piezoelectric element has failed, the actuator has failed, or the drive circuit has failed. Therefore, in many cases, it is necessary to determine not only whether or not the shock absorber has failed, but also to know what part has failed and change the response.

For example, in a sensor unit using a piezoelectric element, even if one element is abnormal, the detection accuracy is greatly reduced, but the suspension characteristics can be switched, and if the ride comfort is considered, the detection result should be corrected. It is desirable to continue the control of the suspension characteristics. On the other hand, the piezoelectric actuator has a relatively small effect on the amount of expansion and contraction such as cracking of one element, but is used under severe conditions because the amount of expansion and contraction due to application of a high voltage is large and used under severe conditions. Things must be avoided. In particular, it is necessary to avoid a situation in which the piezoelectric element is fixed in a state where the damping force characteristic is soft as a result of continued use in a state where an abnormality has occurred, in terms of running stability. Further, when the high voltage application circuit breaks down, the control of the suspension characteristics itself cannot be performed, and in a configuration having a spare circuit, a measure for switching the circuit to the spare side is required.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to accurately determine an abnormality related to a piezoelectric element.

Configuration of the Invention The configuration of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] As shown in FIG. 1, a suspension control device according to the present invention provides a suspension generation device having a damping force generation pattern, a spring constant, and the like of a suspension means M1 provided between a wheel and a vehicle body. A suspension control device for controlling characteristics, wherein the suspension means M1 includes a first piezoelectric element P1 as a drive source for varying the characteristics, and a second signal for outputting a signal based on vibration applied to the suspension means M1. And a predetermined voltage is applied to the first piezoelectric element P1 based on the output of the second piezoelectric element P2, and the first piezoelectric element P1
A voltage applying means M2 for changing the characteristics of the suspension means M1 by controlling the charging state or the discharging state, and an output detecting means for detecting the output of the first piezoelectric element P1.
M3, based on the output of the first and second piezoelectric elements P1 and P2 when the first piezoelectric element P1 is controlled to a discharge state,
Piezoelectric element failure detection means M4 for detecting failure of each element P1, P2
The gist is to have and.

Further, as a second invention, as shown by a broken line in FIG. 1, when the failure of each of the elements P1 and P2 is not detected by the piezoelectric element failure detecting means M4, the first piezoelectric element P1 The first and second when the battery is controlled to a charged state
The voltage applying means M based on the outputs of the piezoelectric elements P1 and P2.
It is also characterized by including a voltage application unit failure detection unit M5 for detecting the second failure.

[Operation] In the suspension control device of the present invention having the above configuration, the voltage applying means M2 applies a voltage based on the output signal of the second piezoelectric element to the first piezoelectric element P1 provided in the suspension means, The first piezoelectric element P1 is controlled to be in a charged state or a discharged state, and characteristics such as a damping force generation pattern and a spring constant of the suspension means M1 are controlled.

Here, the suspension control device of the present invention detects the output of the first piezoelectric element by the output detecting means M3, and based on this and the output of the second piezoelectric element P2, the respective elements P1, P2 and / or The failure of the voltage applying means M2 is detected.

More specifically, the piezoelectric element failure detecting means M4 detects the first and second states when the first piezoelectric element P1 is controlled to be in a discharge state.
Based on the output of the piezoelectric elements P1 and P2, the failure of each element P1 and P2 is detected.

Further, in the second invention, when the failure of each of the elements P1 and P2 is not detected, the voltage application means failure detection means M5
Accordingly, the failure of the voltage applying means M2 is detected based on the outputs of the first and second piezoelectric elements P1 and P2 when the first piezoelectric element P1 is controlled to be charged.

This makes it possible to accurately determine where the suspension control device is defective.

Embodiment In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of a suspension control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the entire configuration of the suspension control device 1. FIG. 3 (A) is a cross-sectional view of the shock absorber partially cut away, and FIG. 3 (B) is a shock absorber. It is a principal part expanded sectional view.

As shown in FIG. 2, the suspension control device 1 of the present embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR capable of changing the damping force in two stages, and is connected to each of these shock absorbers to control the damping force. And an electronic control unit 4. Each shock absorber 2FL, 2FR, 2RL, 2R
R is provided between the suspension lower arms 6FL, 6FR, 6RL, 6RR of the left and right front and rear wheels 5FL, 5FR, 5RL, 5RR and the vehicle body 7 together with coil springs 8FL, 8FR, 8RL, 8RR.

As described later, the shock absorbers 2FL, 2FR, 2RL, 2RR are a piezo load sensor that detects the force acting on the shock absorbers 2FL, 2FR, 2RL, 2RR, and a shock absorber.
A piezo actuator for switching the setting of the generation pattern of the damping force in 2FL, 2FR, 2RL, and 2RR is incorporated in each one set.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, and 2RR will be described.
Since the structures of 2RL and 2RR are all the same, here the left front wheel 5
A description will be given using the shock absorber 2FL on the FL side as an example. Further, in the following description, reference numerals of the respective members provided on the respective wheels indicate, as necessary, the left front wheel 5FL, the right front wheel 5FR, the left rear wheel 5RL,
Subscripts FL, FR, RL, and RR corresponding to the right rear wheel 5RR shall be added, and if there is no difference between the respective wheels, the subscripts will be omitted.

As shown in FIG. 3 (A), the shock absorber 2 is fixed to the suspension lower arm 6 via an axle-side member 11a at the lower end on the cylinder 11 side, while the upper end of a rod 13 inserted into the cylinder 11 , Is fixed to the vehicle body 7 together with the coil spring 8 via the bearing 7a and the vibration isolating rubber 7b.

Inside the cylinder 11, an internal cylinder 15, a connecting member 16, and a cylindrical member 17 connected to the lower end of the rod 13, and a main piston 18 slidable along the inner peripheral surface of the cylinder 11,
It is arranged. A piezo load sensor 25 and a piezo actuator 27 are housed in the internal cylinder 15 connected to the rod 13 of the shock absorber 2.

The main piston 18 is externally fitted to the cylindrical member 17,
A seal member 19 is interposed on the outer periphery fitted to the cylinder 11. Therefore, the main piston 18
Thus, a first liquid chamber 21 and a second liquid chamber 23 are defined. A backup member 28 is screwed into the distal end of the cylindrical member 17, and in conjunction with the cylindrical member 17, together with the main piston 18, the spacer 29 and the leaf valve 30 are arranged on the cylindrical member 17 side, and the leaf valve 31 is The collar 32 is pressed and fixed to the backup member 28 side. Further, a main valve 34 and a spring 35 are provided between the leaf valve 31 and the backup member 28.
The leaf valve 31 is connected to the main piston 18
Biased in the direction.

When the main piston 18 is stopped, the leaf valves 30 and 31 close the extension side and the contraction side passages 18a and 18b provided on the main piston 18 on one side, respectively. It opens to one side as it moves in the A or B direction. Accordingly, the hydraulic oil filled in the two liquid chambers 21 and 23 moves between the two liquid chambers 21 and 23 through one of the two passages 18a and 18b as the main piston 18 moves. In the state where the movement of the hydraulic oil between the two liquid chambers 21 and 23 is limited to the two passages 18a and 18b, the damping force generated for the movement of the rod 13 is large, and the characteristics of the suspension become hard. .

Piezo load sensor 25 housed inside internal cylinder 15
And the piezo actuator 27 is shown in FIG.
As shown in (B), this is an electrostrictive element laminate in which thin plates of piezoelectric ceramic are laminated with electrodes interposed therebetween. Each electrostrictive element of the piezo load sensor 25 is polarized by a force acting on the shock absorber 2, that is, a damping force. Therefore, if the output of the piezo load sensor 25 is extracted as a voltage signal by a circuit having a predetermined impedance, the rate of change of the damping force can be detected.

The piezo actuator 27 is formed by laminating electrostrictive elements that expand and contract with good responsiveness when a high voltage is applied, and increases the amount of expansion and contraction, and directly drives the piston 36. When the piston 36 is moved in the direction of arrow B in FIG. 3 (B), the plunger 37 and the spool 41 having an H-shaped cross section are also moved in the same direction via the hydraulic oil in the oil-tight chamber 33. Thus, the spool 41 at the position (origin position) shown in FIG.
Move in the direction B in the drawing, the sub-flow path 16c connected to the first liquid chamber 21 and the sub-flow path 3 of the bush 39 connected to the second liquid chamber 23
9b will be communicated. Since the sub flow path 39b is further communicated with the flow path 17a in the tubular member 17 via an oil hole 45a provided in the plate valve 45, when the spool 41 moves in the direction of the arrow B, as a result, The flow rate of the working oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases. That is, the shock absorber 2 and the piezo actuator 27
When the battery is expanded as a result of charging by applying a high voltage, the damping force characteristic is switched from a large damping force (hard) state to a small damping force (soft) side, and when the electric charge is discharged and contracted, the damping force characteristic is increased. Hard).

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is regulated by a spring 35 as compared with the leaf valve 30. The plate valve 45 has an oil hole
An oil hole 45b having a diameter larger than 45a is provided outside the oil hole 45a, and when the plate valve 45 moves toward the bush 39 against the urging force of the spring 46, the hydraulic oil passes through the oil hole 45b. And can be moved. Therefore, irrespective of the position of the spool 41, the hydraulic oil flow rate when the main piston 18 moves in the direction of arrow B becomes larger than when the main piston 18 moves in the direction of arrow A. That is, the damping force is changed according to the moving direction of the main piston 18, thereby further improving the characteristics as a shock absorber. Also,
A hydraulic oil supply passage 38 is provided between the oil-tight chamber 33 and the first liquid chamber 21 together with a check valve 38a to keep the flow rate of the hydraulic oil in the oil-tight chamber 33 constant.

Next, the electronic control unit 4 for switching and controlling the generation pattern of the damping force of the shock absorber 2 will be described with reference to FIG.
This will be described with reference to the drawings.

The electronic control unit 4 includes a piezo load sensor 25 of each shock absorber 2, a steering sensor 50 for detecting a steering angle of a steering wheel (not shown), and a traveling speed of the vehicle as sensors for detecting a traveling state of the vehicle. , A shift position sensor 52 for detecting a shift position of a transmission (not shown), a stop lamp switch 53 for detecting operation of a brake pedal (not shown), and the like.

The electronic control unit 4 that outputs a control signal to the piezo actuator 27 based on these detection signals is a known CP.
Arithmetic and logical operation circuits are formed around the U61, ROM62, and RAM64, and input / output with the outside is performed by an input unit 67 and an output unit 68 which are connected to these circuits via a common bus 65. In addition, the CPU 61 has a built-in serial communication function, and a diagnosis device 69 for performing abnormality diagnosis of the entire vehicle is connected to an input / output port thereof.

The electronic control unit 4 further includes a damping force change rate detection circuit 70 connected to the piezo load sensor 25, a waveform shaping circuit 73 connected to the steering sensor 50 and the vehicle speed sensor 51,
An actuator output detection circuit 74 for detecting the voltage of each piezo actuator 27, a high voltage application circuit 75 connected to each piezo actuator 27, and a drive voltage for driving the piezo actuator by receiving power supply from a battery 77 via an ignition switch 76 A high-voltage power supply circuit 79 of a so-called switching regulator type that outputs a voltage, a constant voltage power supply circuit 80 that transforms the voltage of the battery 77 to generate an operating voltage (5 V) of the electronic control unit 4, and the like. Piezo load sensor 25, shift position sensor 52, stop lamp switch
53, the damping force change rate detection circuit 70, the waveform shaping circuit 73, and the actuator output detection circuit 74 are connected to the input unit 67, while the high voltage application circuit 75 and the high voltage power supply circuit 79 are connected to the output unit 68. I have.

The damping force change rate detection circuit 70 is composed of each piezo load sensor 25FL, F
R, RL, and RR are provided for each of the four detection circuits, and each detection circuit is output from a circuit including the piezo load sensor 25 in accordance with the acting force received by the shock absorber 2 from the road surface. Voltage signal is transmitted to shock absorber 2
Is output to the CPU 61 as the damping force change rate V. The waveform shaping circuit 73 and the steering sensor 50
And a circuit that shapes the detection signal from the vehicle speed sensor 51 into a signal suitable for processing in the CPU 61 and outputs the signal. Therefore, the CPU 61 outputs the output signal from the damping force change rate detection circuit 70 and the waveform shaping circuit 73,
The traveling state of the vehicle can be determined based on signals from 53 and the like. The CPU 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel based on the processing.

The high-voltage applying circuit 75 applies the voltage of +500 volts or -100 volts output from the high-voltage power supply circuit 79 to the CPU 6.
This is a circuit applied to the piezo actuator 27 in response to a control signal from 1. Accordingly, the piezo actuator 28 expands (when +500 volts is applied) or contracts (when -100 volts is applied) by this damping force switching signal, and the hydraulic oil flow rate is switched, so that the damping force characteristic of the shock absorber 2 is soft or hard. Is switched to. That is,
The damping force characteristic of each shock absorber 2 is such that when a high voltage is applied to extend the piezo actuator 27, the first fluid in the shock absorber 2 is controlled by the spool 41 (FIG. 3B) described above. When the flow rate of the hydraulic oil flowing between the chamber 21 and the second liquid chamber 23 increases, the damping force is in a small state, and when the piezo actuator 27 is contracted by discharging a charge by a negative voltage, the hydraulic oil Since the flow rate decreases, the damping force becomes large. Note that once the electric charge accumulated in the piezo actuator 27 is discharged, even if the negative voltage is removed, the piezo actuator
27 remains in a contracted state and shock absorber 2
Maintains the state of large damping force.

Since the voltage applied to the piezo actuator 27 and the voltage output by the piezo actuator 2 itself according to the load applied thereto are detected by the actuator output detection circuit 74, the CPU 61 reads the voltage via the input unit 67. Can be.

Next, damping force control performed by the suspension control device 1 of the present embodiment having the above-described configuration will be described with reference to the flowcharts of FIGS. The outline and relationship of the processing routine shown in each figure are as follows.

(1) Damping force control interrupt processing routine (FIG. 5) This routine is performed at regular intervals after resetting each flag FS, Finhb, etc. to 0 in initialization processing (not shown) at power-on. The flag Finhb indicating the prohibition of controlling the damping force to software is set to a value of 0.
During this period, a process of switching the pattern of the damping force generated by the shock absorber 2 is performed based on the damping force change rate V in the shock absorber 2.

(2) Piezoelectric abnormality determination first routine (FIG. 6) This is a routine for determining an abnormality of the piezo load sensor 25 and the piezo actuator 27, and is repeatedly executed at predetermined intervals. When an abnormality is detected, predetermined abnormality detection processing such as setting of a flag Finhb referred to in the damping force control interruption processing routine (FIG. 5) and sending an alarm to the diagnosis device 69 is performed.

Some of these processes are executed for each of the shock absorbers 2FL, FR, RL, and RR of the wheels 5FL, FR, RL, and RR, but the processes for each wheel are the same. Will be explained without any further explanation.

First, a description will be given of a damping force control interrupt processing routine, which is not directly related to the determination of the abnormality of the piezoelectric ceramics, and thus will be briefly described. When the present processing routine is started, it is determined whether or not the flag Finhb is a value 0 (step 100). If the value is not 0, it is determined that the soft control of the damping force of the shock absorber 2 is prohibited. The shock absorber 2 is forcibly controlled to be hard (step 110), and this routine is once ended. The hardware control of the shock absorber 2 is such that, immediately after the setting of the damping force of the shock absorber 2 is switched from software to hardware, 7-100 volts from the high voltage application circuit 75 by the control signal from the output unit 68. Is applied to the piezo actuator 27 to reduce it, and if the piezo actuator 27 is already in a contracted state, it is held as it is.

On the other hand, if the flag Finhb is 0, the damping force change rate V
Is read (step 120), and it is determined whether or not the damping force change rate V is greater than a predetermined switching reference value Vref (step 130). If the vibration of the vehicle is small and the damping force change rate V is equal to or smaller than the switching reference value Vref (step 130), it is determined whether the flag FS is 1 (step 14).
0), it is determined whether or not the setting of the damping force is being controlled by software, and if not already controlled by software (FS ソ フ ト
1) The shock absorber 2 is hard-controlled as it is (step 110).

When the road surface condition becomes a bad road and the damping force change rate V becomes larger than the switching reference value Vref (step 130), a process for setting an initial value to a timer variable Tb and initializing the timer is performed (step 130). Step 160). The timer variable Tb is used to measure the time by software, and is a variable that determines how long the setting of the shock absorber 2 once softened is continued after V ≦ Vref.

After the above processing, the condition (V>
Vref) is satisfied, the value 1 is set to the flag FS (step 170).
Applying a high voltage of volt to the piezo actuator 27,
The damping force of the shock absorber 2 is small (soft)
(Step 180), and this routine ends.

After the damping force of the shock absorber 2 is once switched to a small state, if the damping force change rate V becomes equal to or less than the switching reference value Vref, this is determined from the value of the flag FS (step 140), and subsequently It is determined whether the timer variable Tb has become equal to or less than 0. (Step 200). Timer variable Tb
The process of decrementing the timer variable Tb by 1 (step 210) and the process of continuously controlling the shock absorber 2 by software (step 180) are repeated until the value of the timer variable Tb becomes 0 or less.

After the damping force change rate V becomes equal to or less than the switching reference value Vref,
When the time corresponding to the timer variable Tb has elapsed (step 20
0), the flag FS is reset to a value of 0 (step 220), and the setting of the damping force of the shock absorber 2 is hardly controlled (step 110). That is, according to the control signal from the output unit 68, -100 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 to reduce it. afterwards,
Exit to "RTN" and end this routine.

With the above processing, the setting of the damping force of each shock absorber 2 is switched to software immediately when the damping force change rate V exceeds the switching reference value Vref. Will be maintained.

While continuing the damping force control, the CPU 61 executes a piezoelectric ceramic abnormality determination first routine shown in FIG.
When this routine is started, first, it is determined whether or not a flag FS indicating that the damping force is controlled by software is a value of zero (step 300). It is determined whether 30 msec has elapsed since the switching was performed (step 310). here,
The reason for waiting for 30 msec after the switching to the hardware is to perform detection after the disappearance of the electric charge accumulated in the piezo actuator 27 due to the applied -100 volts, thereby improving the detection accuracy. Except for these conditions, nothing is performed, the process exits to “RTN”, and the routine ends once.

If it is determined that the setting of the damping force of the shock absorber 2 has been switched to soft, then the piezo load sensor 25
The output U2 of the piezo actuator 27 is read (step 320), and the output U1 of the piezo actuator 27 is used as an actuator output detection circuit.
A reading process is carried out via 74 (step 330). Thereafter, a process of calculating average output voltages U1AV, U2AV per one piezoelectric ceramic is performed based on both outputs U1, U2 (step 340). Here, the average output voltage U1AV, U2
The AV is calculated by dividing the outputs U1 and U2 by the number of stacked elements of the piezo load sensor 25 and the piezo actuator 27, respectively, and taking a weighted average of the calculated values up to the previous time. The reason why the average value is obtained is that the load is applied to the piezo load sensor 25 and the like as the vehicle travels, and it is difficult to judge whether the value is abnormal or not with an instantaneous value.

Next, a process of obtaining a voltage ratio α by dividing the output voltage U2AV by the output voltage U1AV is performed (step 350). Since both the piezo load sensor 25 and the piezo actuator 27 use piezoelectric ceramics, when a force is applied, they are distorted, and a voltage signal having a magnitude corresponding to the force can be taken out to an external circuit. Since both receive the same structural force, the ratio α of the two output voltages is substantially constant regardless of the road surface condition.
Therefore, when the voltage ratio α greatly deviates from the design value αref, it can be determined that an abnormality has occurred in the piezoelectric ceramics. Therefore, this voltage ratio α is set to a design value αref
, And the magnitude of the deviation is determined (step 360).

If this deviation is larger than a predetermined upper limit value β1, it can be determined that the output of the piezoelectric ceramics of the piezo load sensor 25 has decreased. Therefore, it is determined that an abnormality has occurred in the piezo load sensor 25, and the abnormality detection processing A is executed. (Step 370). On the other hand, this deviation is equal to a predetermined lower limit-
If it is smaller than β2, it can be determined that the output of the piezoelectric ceramics of the piezo actuator 27 has decreased. Therefore, it is determined that an abnormality has occurred in the piezo actuator 27, and abnormality detection processing B is executed (step 380).

The abnormality detection process A is a process of outputting an alarm signal to the diagnosis device 69, a process of switching the map for obtaining the switching reference value Vref for the shock absorber 2 in which the abnormality is detected to another map having a larger value than the conventional one, Alternatively, only the signal of the damping force change rate V from the piezo load sensor 25 corresponding to the shock absorber 2 in which the abnormality has been recognized is multiplied by a predetermined correction coefficient (> 1) to increase the correction. On the other hand, the abnormality detection process B is a process of outputting an alarm signal to the diagnosis device 69, a process of setting a prohibition flag Finhb relating to the shock absorber 2 that has detected an abnormality to a value of 1, and the like.

Here, the switching of the damping force setting to software is prohibited in response to the abnormality of the piezo actuator 27. When a slight abnormality occurs in the piezo actuator 27, the piezo actuator 27 is continuously used and the piezo actuator 27 is used. This is to avoid a situation in which the vehicle is fixed in an extended state, that is, a state in which the damping force is soft, and to secure sufficient running stability. On the other hand, with respect to the abnormality of the piezo load sensor 25, the switching reference value Vref is increased and corrected to continue the switching control of the damping force, so that the traveling stability and the riding comfort are ensured. As a result, the reliability of the suspension control device 1 of the present embodiment can be significantly improved.

Next, a second embodiment of the present invention will be described. This embodiment is obtained by adding processing to the first embodiment.
In addition to the same apparatus configuration, damping force control, and determination first routine as in the embodiment, a piezoelectric ceramic abnormality determination second routine shown in FIG. 7 is executed. This second routine is executed when the setting of the damping force of the shock absorber 2 is software (flag FS = 1), and the outline of the process is similar to that of the first routine. Therefore, in the same processing, the last two digits of the step number indicating this are the same.

When the present routine is started, it is first determined whether or not the flag FS has a value of 1 (step 400). If the value is not 1, the flow directly goes to "RTN" and the present routine is terminated. In the abnormality determination first routine, it was determined whether or not the flag FS was 0 (step 300 in FIG. 6). In the first routine, the piezoelectric ceramics was checked when the damping force of the shock absorber 2 was hard. Whereas
This is because in the second routine, in addition to this, an attempt is made to check for software.

If the flag FS has the value 1 (step 400), the output U2 of the piezo load sensor 25 is read (step 420) and the output U1 of the piezo actuator 27 is read (step 430), as in the first routine. Further, the average output voltages U2AV and U1AV and the voltage ratio γ are calculated (step 44).
0,450). Even when the damping force of the shock absorber 2 is set to software, the output can be read by the actuator output detection circuit 74 because the piezo actuator 27 outputs a voltage according to the applied force.

Then, it is next determined whether or not the absolute value of the deviation between the voltage ratio γ and the design value γef is greater than a predetermined upper limit η (step 465). If it is determined that there is an abnormality when the setting of the damping force of the absorber 2 is software, it is further determined in the first routine whether or not the abnormality is detected (step S1).
475). If the voltage ratio γ is a normal value or an abnormality has been detected in the first routine, the process exits to “RTN” without any operation, and once ends this routine. Therefore,
In this case, the first routine determines, that is, if there is an abnormality, abnormality detection processing A or B that differs depending on whether the abnormality of the piezo load sensor 25 is the abnormality of the piezo actuator 27.
It does.

On the other hand, if no abnormality has been detected in the first routine, it is determined that the abnormality has occurred in the high voltage application circuit 75, and abnormality detection processing C is executed (step 485), and "RTN"
To end this routine. In the abnormality detection process C,
This includes outputting an alarm signal indicating that the high voltage application circuit is abnormal to the diagnosis device 69, switching the high voltage application circuit 75 determined to be abnormal to a spare circuit, and the like. The high voltage application circuit 75 may be switched to the spare circuit by using a configuration in which a spare circuit is built in each high voltage application circuit and switched to this, or another high voltage application circuit 75 is shared as the spare circuit. In this case, the four-wheel independent damping force control may be stopped and the left and right wheels may be switched simultaneously.

The suspension control device 1 of the second embodiment described above
Then, in addition to the judgment in the first routine,
It is possible to detect an abnormality such as shortage or excess of the applied voltage due to the high voltage application circuit 75, and to take appropriate measures such as switching the high voltage application circuit 75 to the standby state. As a result, similarly to the first embodiment, the reliability of the device is improved, and even if an abnormality occurs in the piezoelectric ceramics or the electric circuit of the shock absorber 2, the ride comfort is kept as good as possible and the running stability is sufficiently improved. Can be secured.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, instead of controlling the setting of the damping force of the shock absorber, the spring constant of the air spring is controlled to control the suspension means. Range that does not deviate from the gist of the present invention, such as a configuration that changes the characteristics of the present invention, a configuration that reads the output voltage immediately after switching the damping force to hardware, and detects an abnormality in the circuit that applies −100 volts inside the high-voltage application circuit 75. Of course, the present invention can be implemented in various modes.

Effect of the Invention As described in detail above, according to the suspension control device of the present invention, it is possible to accurately determine the failure of the piezoelectric element used to switch the characteristics of the suspension means. This is an extremely excellent effect that the abnormality of the voltage applying means for driving the voltage can be accurately determined. As a result, the reliability of the suspension control device that uses a piezoelectric element to change the characteristics of the suspension means can be significantly improved, and the side effects of running stability and riding comfort of the vehicle in the event of an abnormality can be considered. Also play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an overall configuration of a suspension control device as one embodiment of the present invention, FIG. (A) is a partial sectional view showing the structure of the shock absorber 2, FIG. 3 (B) is an enlarged sectional view of a main part of the shock absorber 2, and FIG.
FIG. 5 is a block diagram showing the configuration of the electronic control unit 4 of the present embodiment. FIG. 5 is a flowchart showing a damping force control interrupt processing routine. FIGS. 6 and 7 show piezoelectric ceramics in the first and second embodiments, respectively. 5 is a flowchart showing first and second routines for determining the abnormality of FIG. 1… Suspension controller 2FL, FR, RL, RR …… Shock absorber 4 …… Electronic controller 25FL, FR, RL, RR …… Piezo load sensor 27FL, FR, RL, RR …… Piezo actuator 50 …… Steering Sensor 51 Vehicle speed sensor 69 Ignosis device 70 Damping force change rate detection circuit 75 High voltage application circuit 79 High voltage power supply circuit

Claims (2)

(57) [Claims] 1. A suspension control device for controlling characteristics such as a damping force generation pattern and a spring constant of a suspension means provided between a wheel and a vehicle body, wherein the suspension means varies the characteristic. A first piezoelectric element serving as a driving source; and a second piezoelectric element for outputting a signal based on vibration applied to the suspension means. The first piezoelectric element is provided based on an output of the second piezoelectric element. Voltage applying means for changing the characteristics of the suspension means by applying a predetermined voltage to the element and controlling the first piezoelectric element to a charged state or a discharged state; and detecting an output of the first piezoelectric element Output detection means for detecting the failure of each element based on the output of the first and second piezoelectric elements when the first piezoelectric element is controlled to be discharged. Suspension control equipment with Place. 2. The method according to claim 1, wherein the first and second piezoelectric elements are controlled to be in a charged state when no defective element is detected by the defective piezoelectric element detecting means.
2. The suspension control device according to claim 1, further comprising a voltage application unit failure detection unit that detects a failure of the voltage application unit based on the output of the piezoelectric element.