JP2002134804A - Piezo actuator abnormality detection device - Google Patents

Abstract

(57) [Problem] To provide an abnormality detection device for a piezo actuator capable of detecting an abnormality state such as partial disconnection or short circuit of the piezo actuator in more detail. SOLUTION: A high voltage generating circuit 2 for generating a high voltage to be applied to a piezo actuator 1 formed by laminating a plurality of piezoelectric bodies 11 which expand and contract according to an applied voltage, and a high voltage generating circuit 2 when a charging switching element is turned on. And a switching circuit 3 for applying the high voltage generated in the piezo actuator 1 to discharge the electric charge accumulated in the piezo actuator 1 when the discharge switching element is turned on. The abnormality detection circuit 5 detects the piezo actuator voltage after a certain period from when the control circuit 4 outputs the charge or discharge signal to the switching circuit 3, and compares the detected voltage with the normal value of the piezo actuator voltage at that time. An abnormal state of the actuator 1 can be finely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting device for detecting an abnormality of a piezo actuator.

[0002]

2. Description of the Related Art Piezo actuators, which generate displacement in accordance with an applied voltage due to expansion and contraction of a piezoelectric body, have been widely used in a vehicle drive device because of their high response and excellent controllability. On the other hand, in recent years, it has become necessary to establish a failure diagnosis technology for on-vehicle equipment in order to respond to new vehicle regulations. Is required.

As a safety measure against a high voltage of a piezo actuator, for example, Japanese Patent Application Laid-Open No. 3-128679 discloses a first discharge in which a high voltage is applied for a predetermined time when the piezo actuator contracts, and then the accumulated charges are discharged. Means and a second discharge means for detecting whether the discharge has been reliably performed, and prohibiting the subsequent supply of a high voltage and discharging the electric charge of the actuator when the discharge is not performed are provided. .

[0004]

The above-mentioned device is intended to avoid various inconveniences due to the application of a high voltage by stopping the drive when any abnormality (for example, short circuit) occurs in the drive circuit system of the actuator. . However, in the above-described apparatus, it is known that some abnormality has occurred, but the location and type of the abnormality cannot be specified, and there has been a problem that much labor is required to specify these.

[0005] The piezo actuator usually has a multilayer structure in which a plurality of piezoelectric bodies are stacked via electrodes, and abnormalities such as partial disconnection inside the piezo actuator and disconnection of the connector are considered. Therefore, in order to know the occurrence of abnormality quickly and take appropriate measures, for example, in addition to wire breakage or short-circuit in the charge or discharge circuit, various abnormalities such as partial breakage inside the piezo actuator and disconnection of the connector, It is required to detect the location and type of abnormality in more detail.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a piezo actuator capable of detecting finer conditions such as a broken wire or a short circuit, a partial disconnection inside the piezo actuator, or a disconnection of a connector. An object of the present invention is to provide an abnormality detection device.

[0007]

According to a first aspect of the present invention, there is provided an abnormality detecting apparatus for a piezo actuator, comprising a plurality of piezoelectric members which expand and contract in accordance with an applied voltage, wherein a high voltage applied to the piezo actuator is detected. The high voltage generating means and the high voltage generated by the high voltage generating means when the charging switching element is turned on are applied to the piezo actuator, and the charges accumulated in the piezo actuator are discharged when the discharging switching element is turned on. And switching means for causing the switching. The control means controls the ON / OFF of the charging or discharging switching element by outputting a charge or discharge signal to the switching means, and furthermore, after a predetermined period from the output of the charge or discharge signal. Abnormality detecting means for detecting an abnormal state of the piezo actuator by detecting the piezo actuator voltage and comparing the piezo actuator voltage with a normal value of the piezo actuator voltage after the predetermined period.

[0008] The abnormality detecting device having the above-mentioned structure pays attention to the point that the voltage waveform of the piezo actuator at the time of charging and discharging changes according to the capacitance of the piezo actuator. For example, the capacitance of the piezo actuator is maximum during normal operation, and decreases if there is a partial disconnection during lamination, and becomes almost zero when the disconnection occurs. When the capacitance decreases,
The voltage rises quickly, and in the case of insulation failure or short circuit, the voltage rises slowly or does not rise. Therefore, a detailed abnormality determination can be made by knowing the voltage waveform in each state in advance and comparing with the normal state. Specifically, it is sufficient to compare the piezo actuator voltage after a predetermined period of time with a normal value after the above-mentioned predetermined period, and to detect not only the presence or absence of an abnormality but also a more detailed state such as open or partial disconnection. Can be. Therefore, the failure diagnosis is performed promptly, and the trouble and the like required for specifying the abnormal part can be omitted, which is of great practical value.

According to the second aspect of the present invention, the first voltage value which is larger than a normal value of the piezo actuator voltage after a predetermined period from the output of the charging signal to the abnormality detecting means as a comparison reference voltage value at the time of charging. And a second voltage value (first voltage value> second voltage value> the normal value), and a third voltage value and a fourth voltage value (the third voltage value <the fourth voltage value) smaller than the normal value. And the values are sequentially compared with the piezo actuator voltage after the predetermined period, and when the piezo actuator voltage is larger than the first voltage value, it is determined that the open state is abnormal. When the piezo actuator voltage is lower than the first voltage value and higher than the second voltage value, it is determined that the partial disconnection state is abnormal, and when the piezo actuator voltage is lower than the third voltage value, the short circuit state is detected. Determined to be abnormal, and when the piezoelectric actuator voltage is less than the third voltage fourth voltage value greater than the value of is determined that an abnormality of insulation failure state.

As described above, in the case of partial disconnection, the voltage rises earlier than in the normal state, and in the case of open circuit, the voltage rises earlier. Therefore, if the first and second voltage values (first voltage value> second voltage value) which are larger than the normal value after the above-mentioned fixed period are set as appropriate,
Partial disconnection and open state can be distinguished. Further, the voltage rise is slow in the case of insulation failure, and does not rise in the case of short circuit. Therefore, the third and fourth voltage values (third voltage value <fourth voltage value) smaller than the normal value ) Can be distinguished by setting them appropriately.

According to the third aspect of the present invention, the piezo actuator is connected to the switching means by a connector, and a small-capacity capacitor is connected in parallel between the connector and the piezo actuator. When the state where the piezo actuator voltage after the certain period is smaller than the third voltage value and the state where the piezo actuator voltage is larger than the normal value before the certain period is detected, it is determined that the connector is in an abnormal state of the disconnection state. .

When the connector is disconnected, it is difficult to distinguish it from the open state. However, if a small-capacity capacitor is electrically connected in parallel between the connector and the piezo actuator, electric charges are accumulated in the capacitor when the connector is opened and the connector is disconnected. Has a different voltage waveform because it discharges immediately after the voltage rises sharply. So, for example, the above-mentioned certain period,
The connector is determined to be disengaged only when the voltage at which the voltage becomes substantially zero due to discharge is set, and the piezo actuator voltage after the predetermined period is smaller than the third voltage value and a high voltage state is detected before that. I do. As a result, it is possible to distinguish between an open state and a short-circuit state, and more detailed detection is possible.

According to a fourth aspect of the present invention, the fifth voltage, which is smaller than a normal value of the piezo actuator voltage after a predetermined period from the output of the discharge signal, is output to the abnormality detecting means as a comparison reference voltage value at the time of discharge. A value is set, and the piezo actuator voltage after the certain period is compared with this value. When the piezo actuator voltage is smaller than the fifth voltage value, it is determined that the partial disconnection state is abnormal, and the piezo actuator voltage is When it is almost zero, it is determined that there is an abnormality other than the partial disconnection.

At the time of discharging, if there is a partial disconnection, the fall of the piezo actuator voltage is accelerated. Therefore, by comparing the piezo actuator voltage after a certain period of time with a fifth voltage value smaller than a normal value, the partial disconnection is determined. Detection is possible. In the case of other abnormalities, the voltage value does not increase, so if the voltage value at the start of discharge is almost 0,
It can be detected as any abnormality other than the partial disconnection.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of an abnormality detection device for the stacked piezo actuator 1. The high voltage generation circuit 2 is a high voltage generating means for generating a high voltage applied to the piezo actuator 1, and the charging switching element is turned on. A switching circuit 3 serving as a switching means for applying a high voltage generated by the high voltage generating circuit 2 to the piezo actuator 1 and discharging electric charges accumulated in the piezo actuator 1 when the discharging switching element is turned on;
A charge or discharge signal is output to the switching circuit 3 to turn on or off the charging or discharging switching element.
By detecting a piezo actuator voltage after a certain period of time after the charge or discharge signal is output, and comparing it with a normal value of the piezo actuator voltage after the certain period, And an abnormality detection circuit 5 as abnormality detection means for detecting an abnormal state of the piezo actuator 1.

FIG. 2A shows the structure of the laminated piezo actuator 1. The piezo actuator 1 is formed by laminating and integrating a large number of rectangular thin plate-shaped piezoelectric bodies 11 and is charged or discharged via lead wires 12 and 13. The piezoelectric body 11 is made of a piezoelectric material such as PZT,
It has the property of expanding by injecting charges and contracting by removing charges. Lead wires 12, 13
Are connected to + electrodes or −electrodes formed on the left and right side surfaces of the laminate, and are electrically connected to the + electrodes or −electrodes provided alternately with each piezoelectric plate 11 interposed therebetween. The electrical connection state of the piezo actuator 1 is as shown in FIG. 2B, and the stacked piezoelectric bodies 11 are connected in parallel.
FIG. 3A is a diagram in which a connector 6 for electrically connecting the piezo actuator 1 to an external drive circuit is provided.
A small-capacity capacitor 14 is connected in parallel between the piezo actuator 1 and the connector 6, and the electrical connection state including these is as shown in FIG. 3B. The resistance 15 in the D section is representative of the insulation resistance of the piezo actuator 1.

In FIG. 1, a control circuit 4 outputs a charging signal to a switching circuit 3 based on an applied voltage signal input from a CPU, turns on a charging switching element (hereinafter referred to as a charging SW), and generates a high voltage. The high voltage boosted by the circuit 2 is charged to the piezo actuator 1. FIG.
As shown in (a) and (b), the switching uses a multiple switching method in which charging and discharging are performed by switching stepwise, and charging is performed when a rising edge of an applied voltage signal (for example, a 0-5 V rectangular wave signal) is detected. Start. Charge SW
When the charging current of the piezo actuator 1 reaches a predetermined value (for example, 20 A) after turning on, the charging SW is turned off,
After a certain OFF period (for example, 10 μs), the charge SW
Turn ON. This is repeated, and the charging is completed when a predetermined charging voltage (for example, 100 V) is reached.

The discharge is performed by the control circuit 4 when the falling edge of the applied voltage signal is detected.
Is started by outputting a discharge signal. A discharge switching element (hereinafter, referred to as a discharge SW) is turned on, and after the discharge current of the piezo actuator 1 reaches a predetermined value (for example, 20 A), the discharge SW is turned off and a constant OF is set.
The discharge SW is turned on again after the F period (for example, 10 μs). Thereafter, the discharge is continued until the applied voltage signal is input again (a rising edge is detected).

In FIG. 1, the voltage of the piezo actuator 1 at the time of charging passes through a voltage dividing circuit formed by resistors 71 and 72 and is input to the abnormality detecting circuit 5. The abnormality detection circuit 5 compares the piezo actuator voltage T seconds after the input of the applied voltage signal with a predetermined comparison reference voltage value, and outputs a determination result to the control circuit 4. If abnormal, the control circuit 4 turns off the charging SW of the switching circuit 3 to stop the supply of high voltage, and sends diagnostic information to the CPU. An abnormality can be detected during discharging by performing the same processing as during charging. The details will be described below.

The abnormal states detected in the present embodiment include partial disconnection, open, connector disconnection, poor insulation,
There are five items of short circuit. FIG. 4A shows a voltage waveform at the time of charging. In a normal state, a predetermined voltage is reached by charging several times. On the other hand, in the case of a partial disconnection, for example, if the partial disconnection occurs at the portion A in FIG. 3B (that is, a part of the piezoelectric body 11 of the piezo actuator 1 connected in parallel), the capacitance decreases. As shown in the waveform of the partial disconnection in FIG. 4A, the voltage rises earlier than in the normal state. In the case of the open state, for example, in the case of disconnection at the portion B in FIG. 3B, the load of the drive circuit is only the capacitor 14, and the voltage at the time of charging is as shown by the open waveform in FIG. Get up earlier. On the other hand, FIG.
(B) When the connector 6 of the portion C is disconnected, the load on the drive circuit becomes almost zero, and the voltage is as shown in FIG.
Although the connector instantaneously rises as shown by the waveform of the disconnection, it is immediately discharged by the voltage detecting resistor, and the voltage drops rapidly. Thereafter, this voltage rise / fall is repeated. Further, when the resistance 15 of the D portion in FIG. 3B is reduced due to insulation failure, the voltage rise is slowed down as shown by the waveform of the insulation failure in FIG. 4A. Further, when a short circuit occurs, the voltage does not increase.

As described above, since the behavior of the piezo actuator voltage differs depending on the failure state (type of abnormality), the piezo actuator voltage is detected after T seconds from the start of charging, and a plurality of piezo actuator voltages are set in advance based on the normal value after T seconds. It is possible to determine an abnormal state by comparing the comparison with the comparison reference voltage value. Here, a period from the start of charging to the time when the determination is made: T
Although the value of (second) can be set as appropriate, FIG.
As shown in (a), when the period of the voltage rise / fall due to the connector disconnection is matched, the determination of the connector disconnection becomes easy.

The comparison reference voltage value is a value obtained by adding predetermined values A and B (A> B) to a normal value after T seconds from the start of charging: normal value +
A (first voltage value), normal value + B (second voltage value),
Values obtained by subtracting predetermined values C and D (C> D) from normal values: normal value-C (third voltage value) and normal value-D (fourth voltage value). At this time, normal value + A (first voltage value)> normal value + B (second voltage value)> normal value normal value−C (third voltage value) <normal value−D (fourth voltage value) <Normal values> The predetermined values A and B are set to correspond to open and partial disconnection, respectively, and the predetermined values C and D are set to correspond to short circuit and insulation failure, respectively, and the following judgment is made. . That is, when the piezo actuator voltage> normal value + A (first voltage value), it is determined that the open state is abnormal. When the normal value + A> piezo actuator voltage> normal value + B (second voltage value), it is determined. It is determined that the partial disconnection state is abnormal, and when the piezo actuator voltage <normal value−C (third voltage value), it is determined that the short circuit state is abnormal, and the normal value−C <piezo actuator voltage <normal value−D ( 4th
Is determined to be abnormal in the insulation failure state.

In the case of a connector disconnection, the piezo actuator voltage after T seconds becomes almost zero. Therefore, in order to distinguish it from a short circuit state, is there a state where the piezo actuator voltage was larger than the normal value before T seconds. Determine whether For example, each time the charging SW is turned off, the piezo actuator voltage is detected. If the voltage is larger than the normal value at that time, it is determined that there is a possibility that the connector is disconnected. That is, if the piezo actuator voltage before T seconds> normal value at that time and the piezo actuator voltage after T seconds <normal value−C, it can be determined that the connector is disconnected. In the case of a short-circuit state, the voltage does not increase, so that the connector can be distinguished from the disconnection.

FIG. 4 (b) shows waveforms of respective parts at the time of discharge. In a normal state, a predetermined voltage (0 V) is obtained by several discharges.
To reach. In the case where a partial disconnection occurs at the portion A in FIG. 3B, the capacitance decreases, so that the voltage falls earlier than normal. Therefore, as in the case of charging, the abnormal state is determined by detecting the piezo actuator voltage T 'seconds after the start of discharging and comparing it with a comparison reference voltage value based on a normal value after T' seconds. Becomes possible. As the comparison reference voltage value, a normal value −E (fifth voltage value) T ′ seconds after the start of discharge is used, and 0 <piezo actuator voltage after T seconds <normal value−E
(Fifth voltage value), the predetermined value E is set so that it can be determined that the partial disconnection state is abnormal. In the case of opening, disconnection of the connector, insulation failure, or short circuit before the start of discharge, the voltage detection value of the drive circuit is almost zero, so if the piezoelectric actuator voltage after T seconds is ≒ 0 (actual The piezo actuator voltage is gradually charged to zero while it remains charged, and becomes zero.

FIG. 5 shows a control flowchart for driving the actuator and detecting an abnormality. After starting the control, the control circuit 4 first determines in step 1 whether the applied voltage signal (for example, 0-5 V) is at a high level (H) or a low level (L). The applied voltage signal is L for driving the actuator.
When H = 5V from = 0V, the control circuit 4 detects the rising edge in step 2 and starts the charging operation. At this time, in step 3, counting of the abnormality detection timer is started (until T seconds). In the charging, the operation of turning on the charging SW in step 4 and confirming that the charging current has reached a predetermined value (for example, 20 A) in step 5 and then turning off the charging SW in step 6 are repeated. At this time, the ON time of one charging SW is a fixed period (T
_{If the} charging current does not reach a predetermined value (for example, 20 A) in Step 5, the charging switch is turned off after waiting for a certain period (T _CON ) in Step 7. I do.

By repeatedly performing this charging operation, the voltage applied to the piezo actuator 1 reaches a predetermined charging voltage value (for example, 100 V). In the present invention, the charging voltage is reset to a normal value every one charging operation. Compare with After turning off the charge SW in step 6, the abnormality detection circuit 5 compares the charge voltage with a normal value (for example, 50 V) in step 8,
If it is larger than the normal value, it is determined that there is a possibility that the connector is disconnected, and the flag is turned on in step 9. Next, at step 10, it is determined whether or not the count of the abnormality detection timer has reached a predetermined T seconds (for example, 50 μs). Step 10
When the predetermined T seconds are reached, the charging voltage is detected again and compared with a preset comparison reference voltage value. At this time, A> B
Using predetermined values A and B (for example, A = 20 V, B
= 10V) First, in step 11, it is determined whether or not the charging voltage> the normal value + A. When the charging voltage is higher than the normal value + A (for example, 70V), it is detected as an abnormality in the open state. If a negative determination is made in step 11, the process proceeds to step 12, where it is determined whether charging voltage> normal value + B. When the determination in step 12 is affirmative, that is, when the charging voltage is equal to or lower than the normal value + A and higher than the normal value + B (for example, higher than 60 V and lower than 70 V), it is detected as an abnormality in the partially disconnected state.

If the charging voltage is smaller than the normal value + B, the process proceeds to step S13. Here, predetermined values A and B having a relationship of C> D are used (for example, C = 20 V, D = 10
V), Step 13 determines whether or not the charging voltage <normal value−C. If the charging voltage is smaller than the normal value -C (for example, less than 30 V), it is determined in step 14 whether the connector disconnection flag is ON. When the charging voltage is smaller than the normal value -C and the connector disconnection flag is ON, it is detected as an abnormality of the connector disconnection state. If the connector disconnection flag is not ON in step 14, it is detected as a short-circuit state abnormality. If step 13 is negative, the process proceeds to step 15,
It is determined whether or not charging voltage <normal value−D. Step 1
5 is affirmatively determined, that is, the charging voltage is a normal value−
C or higher and smaller than the normal value -D (for example, 30 V
Above 40 V) is detected as an abnormality in the insulation failure state.

When all of steps 11 to 15 are negatively determined, that is, when the charging voltage is equal to or lower than the normal value + B and equal to or higher than the normal value -D, the charging is continued as a normal state. Then, it is determined in step 16 whether or not the charging voltage has reached a predetermined value (for example, 100 V). If not, after waiting for a certain period (T _COff , for example, 10 μs) in step 16, after step 3 repeat. When the charging voltage reaches a predetermined charging voltage value (for example, 100 V) in step 16, the charging is completed.

After the charging is completed, the process returns to step 1. Since the applied voltage signal is at the high level (H) in step 1, the discharging operation is started by detecting the falling edge of the applied voltage signal in step 18. At this time,
In step 19, counting of a timer for abnormality detection is started (until T 'seconds). As in the case of charging, discharging is performed in step 2
This operation is performed by repeating the operation of turning on the discharge SW at 0, turning off the discharge SW at step 21 after the discharge current reaches a predetermined value (for example, 20 A) at step 21. At this time, the ON time of the discharge SW is limited (for example, 20 μs) for a fixed period (T _doN ). Even if the discharge current does not reach a predetermined discharge current in step 21, this fixed period (T _CON ) is determined in step 22. After waiting, the discharge switch is turned off in step 23.

An abnormality is determined for each discharge operation, and it is determined in step 24 whether the charging voltage is substantially zero. If the charging voltage is almost zero, it is detected as any of the following abnormalities: open, connector disconnection, short circuit, or insulation failure. If a negative determination is made in step 24, the process proceeds to step 25, where it is determined whether the count of the abnormality detection timer has reached a predetermined T 'second (for example, 50 μs). If the predetermined T 'seconds have not been reached, the routine returns to step 1, and if the predetermined T' seconds has been reached, the charge voltage is compared again in step 26. At this time, the predetermined value E (for example, 10 V)
It is determined whether or not the charging voltage is smaller than the normal value−E. If the charging voltage is smaller than the normal value−E (for example, less than 40 V), it is detected as an abnormality in the partial disconnection state. If the charging voltage is equal to or higher than the normal value -E in step 26, the process returns to step 1.

This operation is repeated until the voltage applied to the piezo actuator 1 rises again, for example. A method of monitoring the applied voltage of the piezo actuator 1 and repeating the discharge until the voltage is reduced to 0 V or a predetermined voltage value may be adopted. As described above, according to the present invention, an abnormal state can be detected in more detail. Further, since the abnormality detection circuit 5 can use a comparison circuit for determining whether or not the charging voltage has reached a predetermined value in the control circuit of the normal piezo actuator 1, there is an advantage that the circuit configuration is simplified. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the overall configuration of a piezo actuator abnormality detection device according to the present invention.

2A is a diagram showing a configuration of a laminated piezo actuator, and FIG. 2B is a circuit diagram thereof.

3A is a diagram showing a state in which a connector is connected to a piezo actuator, and FIG. 3B is a circuit diagram thereof.

4A is a diagram illustrating a change in a piezoelectric actuator voltage during charging, and FIG. 4B is a diagram illustrating a change in a piezoelectric actuator voltage during discharging.

FIG. 5 is a flowchart for explaining the operation of the abnormality detection device for a piezo actuator of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezo actuator 11 Piezoelectric body 12, 13 Lead wire 14 Capacitor 2 High voltage generation circuit (High voltage generation means) 3 Switching circuit (Switching means) 4 Control circuit (Control means) 5 Abnormality detection circuit (Abnormality detection means) 6 Connector 71 , 72 resistance

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor, Michiyasu Moritsuji, 14 Iwatani, Shimowakaku-cho, Nishio-shi, Aichi Pref. Japan Automobile Parts Research Institute (72) Inventor, Yasuyuki Sakakibara 14th, Iwatani, Shimo-wakaku-cho, Nishio, Aichi, Japan (72) Inventor: Mikio Kumano 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan Inside of DENSO Corporation

Claims (4)

[Claims] A piezoelectric actuator formed by laminating a plurality of piezoelectric bodies that expand and contract in accordance with an applied voltage; a high voltage generating means for generating a high voltage to be applied to the piezoelectric actuator; A switching means for applying a high voltage generated by a voltage generation means to the piezo actuator, and discharging the electric charge accumulated in the piezo actuator when the discharge switching element is ON, and outputting a charge or discharge signal to the switching means. Control means for controlling ON / OFF of the charging or discharging switching element; detecting a piezo actuator voltage after a certain period from when the charge or discharge signal is output; and detecting the piezo actuator voltage after the certain period. By comparing with the normal value, the piezo actuator An abnormality detecting device for a piezo actuator, comprising an abnormality detecting means for detecting an abnormal state. 2. The method according to claim 1, wherein the abnormality detecting means includes a first reference voltage value which is larger than a normal value of a piezo actuator voltage after a predetermined period from when the charging signal is output.
And a second voltage value (first voltage value> second voltage value> the normal value), and a third voltage value and a fourth voltage value (the third voltage value) smaller than the normal value. <Fourth voltage value <Normal value) is set, and the piezo actuator voltage after the certain period is sequentially compared with these values. When the piezo actuator voltage is larger than the first voltage value, the open state is established. When the piezo actuator voltage is smaller than the first voltage value and larger than the second voltage value, it is determined that the partial disconnection state is abnormal. When the piezo actuator voltage is smaller than the third voltage value, 2. The abnormality detection of a piezo actuator according to claim 1, wherein it is determined that the short-circuit state is abnormal, and when the piezo actuator voltage is higher than the third voltage value and lower than the fourth voltage value, it is determined that the insulation failure state is abnormal. apparatus. 3. The piezo actuator is connected to the switching means by a connector, a small-capacitance capacitor is connected in parallel between the connector and the piezo actuator, and the abnormality detecting means is connected to the piezo actuator after the predetermined period. 3. The connector according to claim 2, wherein when the actuator voltage is smaller than the third voltage value and a state in which the piezo actuator voltage is larger than the normal value is detected before the predetermined period, the connector is determined to be abnormal. Abnormality detection device for piezo actuator. 4. A fifth voltage value, which is smaller than a normal value of the piezo actuator voltage after a predetermined period from the output of the discharge signal, is set in the abnormality detecting means as a comparison reference voltage value at the time of discharging, By comparing the piezo actuator voltage after the certain period of time with this value, when the piezo actuator voltage is smaller than the fifth voltage value, it is determined that the partial disconnection state is abnormal, and when the piezo actuator voltage is substantially zero. The abnormality detection device for a piezo actuator according to claim 2 or 3, wherein the abnormality is determined as an abnormality other than partial disconnection.