JPH0569372B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a performance testing device used in a piezoelectric actuator production line or the like to evaluate the quality of the characteristics of a piezoelectric actuator. [Prior Art] In general, a piezoelectric actuator is constructed by stacking a plurality of thin disc-shaped piezoelectric elements in a columnar manner so that the polarities are alternately opposite to each other, and disposing an electrode plate between the elements. This kind of piezoelectric actuator is
For example, patent application No. 59-147788 dated July 16, 1982.
It can be used for an injection rate control device of a fuel injection device as described in the above issue. In this injection rate control device, a voltage is generated in the piezoelectric actuator due to the piezoelectric effect as hydraulic pressure is applied, and the piezoelectric actuator is contracted by discharging the charge at a predetermined time. The performance of a piezoelectric actuator used in such applications depends on its Young's modulus and the amount of contraction during discharge, and in order to ensure that the device functions properly, it is desirable to evaluate the performance on the actuator production line. Conventional performance testing of piezoelectric elements involves applying a voltage to the element to cause it to expand and measuring the amount of expansion, or compressing the element to generate a voltage and measuring the generated voltage. With such conventional test methods, it has not been possible to measure the Young's modulus of the piezoelectric actuator or the contraction performance during discharge. [Object of the Invention] An object of the present invention is to provide an actuator performance testing device that can accurately and quickly evaluate various performances of a piezoelectric actuator. [Summary of the Invention] The performance testing device of the present invention is comprised of a measurement section, a hydraulic unit, and a measurement control section. The measurement unit includes a hydraulic press device that applies a compressive load in the axial direction to the piezoelectric actuator whose performance is to be evaluated, a contraction amount detection means that detects the amount of contraction of the actuator and outputs a signal corresponding to the amount of contraction, and a means for detecting the amount of contraction of the actuator. The load detecting means detects the applied load and outputs a signal according to the load. The measurement control section has a control circuit and a display means. The control circuit controls the hydraulic control valve of the hydraulic unit, receives signals from each detection means, calculates the amount of contraction and load, and displays them on the display means. In the embodiment of the present invention, the measuring section is configured so that the performance can be accurately evaluated regardless of the parallelism of both end surfaces of the piezoelectric actuator. [Embodiment] As shown in FIG. 1, the test apparatus 10 is composed of a measurement control section 12, a measurement section 14, and a hydraulic unit 16. As can be seen from FIG. 2, the measuring section 14 has a hydraulic press device 20 housed in a constant temperature bath 18 whose temperature can be controlled.
1 so that a load can be applied to it. This press device 20 has built-in shrinkage amount detection means 22 and load detection means 24, and output signals from these detection means 22 and 24 are sent to lead wires 26 and 28.
A/D converters 30, 3 of the measurement control unit 12 via
After being sent to the control circuit 2 and converted into a digital signal, it is sent to the control circuit 34. The control circuit 34 is composed of a microcomputer into which a program can be input from the keyboard 36, and controls the test apparatus 10 according to the program, calculates the load applied to the actuator 21 and the amount of contraction thereof, and displays the result on the display section 3.
8. The data can also be recorded using a floppy disk drive and output to a printer or CRT. As shown in FIGS. 3 and 4, the piezoelectric actuator 21 to be inspected consists of a plurality of disc-shaped piezoelectric elements 44 and electrode plates 46 alternately stacked between insulators 40 and 42. The elements are alternately arranged with opposite polarity, and every other electrode plate is connected to a positive terminal 48 and a negative terminal 50. Referring to FIG. 2, the terminals of the actuator 21 are connected to relays 56 and 58 via a positive lead wire 52 and a negative lead wire 54. The first relay 56 is a normally open relay with one terminal grounded, and is opened and closed by a signal from the control circuit 34. The lead wires 52 and 54 and the first relay 56 constitute a normally open circuit for short-circuiting the positive terminal 48 and the negative terminal of the actuator 21. The second relay 58 is a normally open relay that is opened and closed by the control circuit 34, and supplies a DC voltage of, for example, 500V to the actuator 2 via lead wires 52 and 54.
A voltage application circuit is configured to apply a voltage between the positive terminal and the negative terminal of No. 1. The hydraulic unit 16 is configured to pressurize hydraulic oil in a tank 60 with a hydraulic pump 62, adjust it to a constant pressure with an accumulator 64 and a relief valve 66, and then supply it to the hydraulic press 20 via a hydraulic piping 68. There is. Hydraulic pressure is controlled by a hydraulic control valve 70 operated by a command from the control circuit 34. Referring to FIGS. 5 and 6, a hydraulic cylinder 74 is fixed to a frame 72 of the hydraulic press device 20, and a ram 76 is moved up and down by hydraulic pressure. The piezoelectric actuator 21 is placed on the ram 76 and positioned coaxially by a positioning ring 78. An anvil block 80 having a built-in load cell is fixed to the upper part of the frame 72, and constitutes the load detection means 24. A cylindrical anvil 82 is fitted into the anvil block 80 so as to be able to move forward and backward, and is adapted to transmit an axial load to the load cell. Anvil 82
The lower end of the adapter block 84 has a generally hemispherical shape and engages a hemispherical recess (not shown) formed in the upper surface of the adapter block 84. In this way, since the anvil 82 and the adapter block 84 are engaged with each other through the hemispherical mating surfaces, the adapter block 84 is engaged even when the upper and lower end surfaces of the actuator 21 are not parallel.
swings around the center of curvature of the hemispherical mating surface, and as a result, a compressive load can always be applied to the actuator 21 in the axial direction. The adapter block 84 is swingably supported on the frame 72 by a suitable stay (not shown) so that the adapter block 84 will not fall even if the actuator 21 is removed. In the illustrated embodiment, the contraction amount detection means 22 is
It consists of two sets of gap sensor devices 86 and 88, which are mounted at symmetrical positions with respect to the axis of the hydraulic press device 20. These gap sensor devices 86 and 88 are identical, with gap sensors 92 and 93 fixed to the ram 76 by a lower bracket 90, and metal plates 96 and 9 supported on the adapter block 84 by an upper bracket 94, respectively.
It consists of 7. Each metal plate 96, 97 is secured to a vertically adjustable threaded rod 100 by an adjusting nut 98 and biased downwardly by a spring 102. Therefore, depending on the size of the actuator 21 to be inspected, the metal plate 9
By adjusting the initial positions of 6 and 97, the initial gap between the metal plate and the gap sensor can be set within the measurement range. Further, since the spring 102 is provided, even if the metal plate and the gap sensor unexpectedly collide, the latter will not be damaged. A handle 104 is provided to allow manual lowering of ram 74 and removal of actuator 21 when hydraulic pressure to cylinder 74 is removed. One end of this handle 104 is connected to the frame 72.
It is pivotally connected to a block 108 fixed to a cross member 106 of
It is connected to 6. Next, the operation of this performance testing device 20 will be explained in relation to a method for testing the performance of a piezoelectric actuator using this device. Control circuit 34 of measurement control section 12
is programmed to perform performance tests in the sequence described below. The Young's modulus of the actuator 21 is measured in the following sequence. First, the actuator 21 to be inspected is placed on the ram 7.
6 and aligned using the positioning ring 78. Next, with the relays 56 and 58 open, the control circuit 34 operates the hydraulic cylinder 74 by opening the hydraulic control valve 70. As the ram 76 rises, an axial load is applied to the actuator 21. As the load is applied, the actuator 21 is compressed (from point O to point A in the graph of FIG. 7), and the compressive load is calculated based on the signal from the load cell built into the anvil block 80 and displayed. As it is compressed, a voltage is generated between the positive electrode plate and the negative electrode plate of the actuator 21, but the first relay 56
Since it is in an open state, voltage continues to accumulate. The amount of contraction of the actuator 21 is measured as follows. As described above, the piezoelectric actuator 21 is a laminate of a disc-shaped piezoelectric element and an electrode plate, so its upper end surface and lower end surface may not be completely parallel. In the device of the present invention, the anvil 82 and the anvil block 84 are engaged through a hemispherical mating surface, and since the anvil block 84 is swingable along this mating surface, the upper end surface of the actuator 21 If the parallelism between the anvil block 84 and the lower end surface is not perfect, when an initial load is applied, the anvil block 84 swings and its lower surface aligns exactly with the upper end surface of the actuator. In this state, the gap of the right gap sensor device 86 and the gap of the left gap sensor device 88 will exhibit different values. As the load further increases and the actuator 21 is further compressed, the upper and lower end surfaces of the actuator gradually become parallel, and the values of the left and right gaps become closer. During this time, the left and right gap sensor 9
The output signals of 2 and 93 are sent to the control circuit 34, which calculates the average value of the left and right gaps,
The amount of contraction of the actuator 21 is calculated by calculating the change in the gap based on this average value. The Young's modulus of the actuator is automatically calculated and evaluated from the applied load and the amount of contraction. Since the test device of the present invention uses a pair of left and right gap sensor devices 86 and 88 as the contraction amount detecting means 22, the Young's modulus can be accurately measured regardless of the parallelism of the upper and lower end surfaces of the actuator 21. The following table shows the 10 actuator types.

〔Effect of the invention〕

The actuator performance testing device of the present invention can accurately and quickly evaluate the Young's modulus of a piezoelectric actuator. When a circuit that short-circuits the terminals of the actuator is provided, the contraction performance of the actuator during discharge can be evaluated. When a voltage application circuit is further provided, the shrinkage performance during discharge can be evaluated more accurately. When an adapter block is provided on the anvil of a hydraulic press device and the two are engaged through a hemispherical mating surface, an axial load can be applied regardless of the parallelism of the upper and lower end surfaces of the actuator. When the contraction amount detecting means is composed of a pair of gap sensor devices, which are arranged symmetrically, and the performance is evaluated based on the average value of the contraction amounts detected by both, it is possible to Young's modulus can be accurately measured regardless of parallelism.

[Brief explanation of the drawing]

FIG. 1 is a front view of the test device of the present invention, FIG. 2 is a schematic diagram of the device shown in FIG. The figure is a perspective view of the actuator to be inspected, FIG. 4 is a sectional view taken along the - arrow in FIG. The gap sensor device is omitted from the right side view of the hydraulic press device shown in the figure, and FIG. 7 is a graph showing the relationship between the load and the amount of contraction in the evaluation method using the test device of the present invention. 10... Performance test device, 12... Measurement control section, 14
... Measuring unit, 16... Hydraulic unit, 20... Hydraulic press device, 21... Piezoelectric actuator, 22... Contraction amount detection means, 24... Load detection means, 34... Control circuit, 56... First relay, 58... Second relay ,7
0... Hydraulic control valve, 74... Hydraulic cylinder, 76... Ram, 80... Anvil block, 82... Anvil,
84... Adapter block, 86, 88... Gap sensor device, 92, 93... Gap sensor, 9
6,97...Metal plate.

Claims (1)

[Scope of Claims] 1. A performance testing device for evaluating the performance of a piezoelectric actuator consisting of a laminate of a piezoelectric element and an electrode plate, comprising: (a) applying an axial compressive load to the actuator whose performance is to be evaluated; a hydraulic press device that elastically contracts the actuator; a contraction amount detection means that detects the amount of contraction of the actuator and outputs a signal corresponding to the amount of contraction; (b) a hydraulic unit having a hydraulic control valve and supplying hydraulic oil at a controlled pressure to the hydraulic press device; and (c) the detection means. a measurement control unit comprising: a control circuit that receives signals from the control circuit to calculate the amount of contraction and the load and controls the hydraulic control valve; and a display means that displays the amount of contraction and the load in accordance with commands from the control circuit. A performance testing device for a piezoelectric actuator, comprising: 2. The measurement control unit further includes a normally open circuit that can short-circuit different terminals of the actuator, and the control circuit closes the normally open circuit when the compressive load applied to the actuator reaches a predetermined value. hand,
2. The performance testing device according to claim 1, wherein the voltage generated in the actuator by applying a load is dissipated to cause the actuator to further contract and calculate the amount of contraction. 3. The measurement control unit further includes a voltage application circuit that applies a predetermined DC voltage between different terminals of the actuator, and the control circuit extends the actuator by applying a predetermined voltage between the different terminals of the actuator in advance, and then 3. The performance testing device according to claim 2, wherein the amount of contraction is measured by applying a compressive load to the actuator. 4. The hydraulic press device includes a ram and an anvil member that cooperate with each other to apply a compressive load to the actuator, and an adapter block disposed between the anvil member and the actuator, and the adapter block and the anvil member 2. A performance testing device according to claim 1, wherein the adapter blocks abut each other by substantially hemispherical mating surfaces such that the adapter blocks can be angularly displaced relative to the anvil member. 5. The contraction amount detection means includes a pair of gap sensor devices, each gap sensor device being arranged symmetrically with respect to the axis of the hydraulic press device and spaced apart from the axis, and the control circuit controlling both gap sensor devices. 5. The performance testing device according to claim 4, wherein the average value of the actuator contraction amounts detected by the above is displayed. 6. Each gap sensor device includes a gap sensor and a metal plate that cooperates with the gap sensor, one of the gap sensor and the metal plate is attached to the ram and the other is attached to the adapter block, and the metal plate adjusts its initial position. 6. A performance testing device as claimed in claim 5, wherein the performance testing device is adjustably mounted on the ram or adapter block via an adjustment mechanism.