JP7058030B1 - Drive circuit of wireless vibration device and piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration exciter which can be easily used when measuring the dynamic rigidity of a work. A wireless vibration device 10 is connected to a battery 1, and a piezoelectric element 2 that vibrates a work piece 90 by an inverse piezoelectric effect when a drive voltage is applied, and a work piece 90 are vibrated. While there is a force sensing unit 3 that senses the force received from the workpiece 90, and a control unit 4 that wirelessly transmits information indicating the sensed force to the control device 29 that controls the machining of the workpiece 90. To prepare for. [Selection diagram] Fig. 1

Description

The present invention relates to a vibration exciter used by being attached to a spindle of a machine tool when measuring the dynamic rigidity of a work.

Machine parts such as automobiles and aircraft are manufactured by processing workpieces (hereinafter referred to as workpieces) using machine tools such as NC milling machines and machining centers. When machining a work using a machine tool, vibration is generated in the spindle and the work of the machine tool. When vibration occurs, the machining accuracy decreases and the productivity decreases. Therefore, at the manufacturing site using a machine tool, various efforts are made to measure and evaluate the vibration characteristics of the spindle and the workpiece of the machine tool. For example, Patent Document 1 below discloses a technique for measuring dynamic characteristics in a vibration system including a rotary tool.

In addition, there is dynamic stiffness as one of the evaluation parameters in the machine tool. Among the dynamic stiffness, for example, those based on displacement and force include mechanical compliance. For example, Patent Document 2 below discloses a technique for measuring the dynamic rigidity of a spindle of a machine tool.

Japanese Unexamined Patent Publication No. 2014-14881 Japanese Unexamined Patent Publication No. 2013-188827

While manufacturing machine parts using a machine tool, a plurality of machining processes such as roughing and finishing are applied to the workpiece. If the work is cut off and the thickness of the work changes as the processing process progresses, there is a problem that the dynamic rigidity of the work changes in each processing process. When the dynamic rigidity of the work changes, the vibration characteristics of the work also change, and the vibration of the work that was suppressed in one machining process is not suppressed in the subsequent machining process and vibration is generated in the work, and the machining accuracy of the work Decreases. In particular, when manufacturing mechanical parts that are required to be thin and light, such as aircraft engine parts, changes in the dynamic rigidity of the work are important problems related to the processing accuracy and productivity of the parts.

Conventionally, in order to measure the dynamic rigidity, an impact test using an impulse hammer and an accelerometer is carried out. However, for workpieces that are applying the machining process installed in the machine tool using jigs, the machining process is interrupted and accelerometers are installed at some measurement points on the workpiece in order to carry out an impact test. Is very time-consuming. Furthermore, if a workpiece with low rigidity is manually vibrated using an impulse hammer, double hammering may occur, which may reduce the reproducibility of the measurement result of the dynamic rigidity. For these reasons, it is not practical to measure and evaluate the dynamic rigidity of the work by performing an impact test for each machining process at the machining site using a machine tool. Neither of the techniques of Patent Documents 1 and 2 described above is a technique for measuring the dynamic rigidity of a work.

The machining conditions of the machine tool include the rotation speed of the spindle, the depth of cutting by the rotary tool, the feed rate of the spindle, and the like. In each of multiple machining processes, in order to apply the machining process to the workpiece under appropriate machining conditions that can suppress the vibration of the workpiece, the dynamic rigidity of the workpiece can be easily adjusted before each machining process is started. It is desired to measure.

An object of the present invention is to provide a vibration exciter that can be easily used when measuring the dynamic rigidity of a work.

The present invention for solving the above problems includes, for example, the following aspects.
(Item 1)
A piezoelectric element that is connected to a battery and vibrates the workpiece by the inverse piezoelectric effect when a drive voltage is applied.
A force sensing unit that senses the force received from the workpiece while the workpiece is being vibrated.
A control unit that wirelessly transmits the detected information indicating the force to a control device that controls the processing of the workpiece.
A wireless vibration exciter equipped with.
(Item 2)
The capacitive element connected to the piezoelectric element and
It is switched between applying the voltage due to the electric energy stored in the capacitive element to the piezoelectric element or applying the voltage generated by the piezoelectric element receiving the force from the workpiece to the capacitive element. Switching part and
Item 1. The wireless vibration exciter according to Item 1.
(Item 3)
Item 2. The wireless vibration exciter according to Item 1 or 2, wherein the control unit drives the piezoelectric element while changing the drive frequency.
(Item 4)
Item 2. The wireless vibration exciter according to any one of Items 1 to 3, wherein the control unit transmits information on communication quality of wireless communication with the control device to the control device.
(Item 5)
The control unit
The dynamic rigidity of the work piece is calculated based on the information indicating the force and the information on the displacement of the work piece caused by the vibration.
Item 2. The wireless vibration exciter according to any one of Items 1 to 4, wherein the calculated information indicating the dynamic rigidity is wirelessly transmitted to the control device.
(Item 6)
Capacitive elements connected to the piezoelectric element and
A switching unit that switches between applying a voltage due to the electric energy stored in the capacitive element to the piezoelectric element or applying a voltage generated by the piezoelectric element receiving a force from a workpiece to the capacitive element. When,
A drive circuit for piezoelectric elements.

According to the present invention, it is possible to provide a vibration exciter that can be easily used when measuring the dynamic rigidity of a work.

It is a figure which shows the schematic structure of the wireless vibration apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the voltage of a piezoelectric element and the voltage of a capacitive element. It is a figure which shows typically the structure of the machine tool to which the wireless vibration exciter which concerns on one Embodiment of this invention is attached. It is a perspective view which shows the appearance of the wireless vibration apparatus which concerns on one Embodiment of this invention. It is a measurement result of the tip displacement of the piezoelectric actuator which concerns on Example 1. It is a graph which shows the measurement result of the compliance which concerns on Example 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and thus duplicate description of the same or similar components will be omitted.

[Device configuration]
FIG. 1 is a diagram showing a schematic configuration of a wireless vibration exciter according to an embodiment of the present invention.

The wireless vibration device 10 (hereinafter, also simply referred to as a vibration device 10) according to an embodiment is shown in FIG. 3, which will be described later, when measuring the dynamic rigidity of the workpiece 90 (hereinafter, referred to as a work 90). It is used by being attached to a machine tool 20 such as an NC milling machine or a machining center. The vibrating device 10 is connected to the battery 1 and has a piezoelectric element 2 that vibrates the work 90 by the inverse piezoelectric effect when a driving voltage is applied, and a force received from the work 90 while the work 90 is vibrated. It is provided with a force sensing unit 3 for sensing the force, and a control unit 4 for wirelessly transmitting information indicating the sensed force to the control device 29 for controlling the machining of the work 90.

The battery 1 is provided in the vibration device 10, and supplies a power supply voltage to an electrical or electronic configuration of the piezoelectric element 2, the force sensing unit 3, the control unit 4, and the like included in the vibration device 10. Preferably, the battery 1 is a secondary battery, and can be charged by being connected to an external charging device 28 via a charging connector 11 provided in the housing of the vibration device 10. As the battery 1, for example, a commercially available lithium ion battery can be used. For the charging connector 11 and the charging device 28, for example, a commercially available USB-type C connector and a charger compatible with the USB Power Delivery standard can be used.

The piezoelectric element 2 vibrates the work 90 due to the inverse piezoelectric effect when a driving voltage is applied. The displacement output when the piezoelectric element 2 vibrates the work 90 changes according to the waveform of the drive voltage applied to the piezoelectric element 2. The piezoelectric element 2 vibrates the work 90 based on the drive signal from the control unit 4. The drive signal contains information about the drive voltage of the piezoelectric element 2. The information about the drive voltage includes at least the information about the magnitude of the drive voltage and the information about the waveform of the drive voltage. Illustratively, the waveform of the drive voltage applied to the piezoelectric element 2 can be an impulse waveform, a sine wave, a triangular wave, a rectangular wave, a sweep sine wave, a sweep triangular wave, and a sweep rectangular wave. For the piezoelectric element 2, for example, a commercially available laminated piezoelectric actuator can be used.

The force sensing unit 3 senses the force received from the work 90. The force sensing unit 3 is arranged so as to sense a force along the displacement axis of the piezoelectric element 2. In the present embodiment, the analog-type force signal sensed by the force sensing unit 3 is amplified by the amplifier 12, and information indicating the force converted to the digital format through an analog-to-digital conversion circuit (not shown) is transmitted to the control unit 4. Entered. A commercially available force sensor or load cell can be used for the force sensing unit 3.

The control unit 4 wirelessly receives a drive signal of the piezoelectric element 2 including information on the drive voltage of the piezoelectric element 2 from the control device 29 of the machine tool 20, and drives the piezoelectric element 2 based on the received drive signal. While the piezoelectric element 2 vibrates the work 90 based on the drive signal from the control unit 4, the force sensing unit 3 senses the force received from the work 90. The control unit 4 wirelessly transmits information indicating the force sensed by the force sensing unit 3 to the control device 29 of the machine tool 20 that controls the machining of the work 90.

The control unit 4 controls the waveform of the drive voltage applied to the piezoelectric element 2. Illustratively, the waveform of the drive voltage applied to the piezoelectric element 2 can be an impulse waveform, a sine wave, a triangular wave, a rectangular wave, a sweep sine wave, a sweep triangular wave, and a sweep rectangular wave. The control unit 4 can drive the piezoelectric element 2 while changing the driving frequency of the piezoelectric element 2. As a result, the waveform of the drive voltage applied to the piezoelectric element 2 can be, for example, a sweep sine wave, a sweep triangle wave, and a sweep square wave.

For wireless communication between the control unit 4 and the control device 29, various wireless methods such as Wi-Fi (registered trademark) and Bluetooth (registered trademark) can be used. The control unit 4 can transmit information regarding the communication quality of wireless communication with the control device 29 to the control device 29. As information on communication quality, for example, an RSSI (Received Signal Strength Indicator) value or a dBm (decibels reactive to a milliwatt) value, which expresses the signal strength of wireless communication, can be used. As a result, the control device 29 can grasp in advance the possibility of a communication error between the vibration exciter 10 and the control device 29, and the control device 29 warns, for example, the operator of the machine tool 20. You can issue an error.

As the control unit 4, a commercially available single board computer such as the arduino (registered trademark) series, which has a CPU and a memory and has a wireless data communication function, can be used.

The vibration exciter 10 is provided with a drive circuit 5 for driving the piezoelectric element 2. The drive circuit 5 is generated by applying a voltage due to the capacitive element 6 connected to the piezoelectric element 2 and the electric energy stored in the capacitive element 6 to the piezoelectric element 2, or when the piezoelectric element receives a force from the work 90. A switching unit 7 for switching whether or not to apply a voltage to be applied to the capacitive element 6 is provided. The drive circuit 5 operates based on the drive signal of the piezoelectric element 2 transmitted from the control unit 4, and applies a drive voltage to the piezoelectric element 2. In the present embodiment, the drive circuit 5 further includes a voltage control unit 8 that controls a voltage applied to the switching unit 7.

The capacitive element 6 supplies the drive voltage of the piezoelectric element 2. The capacitive element 6 is connected to the battery 1 in parallel, and is discharged or charged according to the switching operation (push-pull operation) of the switching unit 7. When the capacitive element 6 is discharged, a voltage due to the electric energy stored in the capacitive element 6 is applied to the piezoelectric element 2, and the piezoelectric element 2 vibrates the work 90 by the inverse piezoelectric effect. When the piezoelectric element 2 receives a force from the work 90, a voltage generated in the piezoelectric element 2 is applied to the capacitive element 6 due to the piezoelectric effect, and the capacitive element 6 is regeneratively charged. The capacitive element 6 may be configured by connecting a plurality of capacitive elements in parallel or in series. A commercially available electric field capacitor can be used for the capacitive element 6.

The internal resistance of the capacitive element 6 is preferably lower than the internal resistance of the battery 1. The internal resistance of the capacitive element 6 means AC impedance. As a result, the capacitive element 6 can regeneratively store electric energy having a frequency higher than that of the electric energy stored in the battery 1. When the vibration device 10 includes the capacitive element 6, the vibration device 10 can regeneratively store electric energy having a higher frequency, and the piezoelectric element 2 can be installed at a higher drive frequency (for example, about 50 Hz or more). It becomes possible to drive. This makes it possible to use the vibration exciter 10 for measuring the dynamic rigidity at a higher frequency.

The switching unit 7 applies a voltage due to the electric energy stored in the capacitive element 6 to the piezoelectric element 2 and an operation of applying a voltage generated by the piezoelectric element receiving a force from the work 90 to the capacitive element 6. Alternately. The details of the switching operation (push-pull operation) by the switching unit 7 will be described later. In the present embodiment, the switching unit 7 is composed of a push-pull circuit in which the NPN transistor 71 and the PNP transistor 72 are connected in two stages. A rectifying element 73 is connected in the forward direction from the emitter to the collector between the emitter and the collector of the NPN transistor 71, and rectified in the reverse direction from the emitter to the collector between the emitter and the collector of the PNP transistor 72. The element 74 is connected.

The voltage control unit 8 controls the voltage applied to the switching unit 7 based on the drive signal of the piezoelectric element 2 transmitted from the control unit 4. In the present embodiment, the drive signal of the piezoelectric element 2 transmitted from the control unit 4 to the voltage control unit 8 is converted into an analog format through a digital-analog conversion circuit (not shown) and input to the voltage control unit 8. For example, an operational amplifier can be used for the voltage control unit 8. In order to control the drive voltage of the piezoelectric element 2, the output of the output node N1 of the switching unit 7 is fed back input to the voltage control unit 8 (op amp).

In this embodiment, the power supply voltage from the battery 1 is boosted by the booster circuit 13 and supplied to the drive circuit 5. Illustratively, the output voltage of the battery 1 is about 5V (DC) and the output voltage of the booster circuit 13 is about 100V (DC). Since the output voltage of the battery 1 can be increased by connecting a plurality of internal cells in series inside the battery 1, for example, the booster circuit 13 can have an arbitrary configuration.

FIG. 2 is a diagram showing the relationship between the voltage of the piezoelectric element and the voltage of the capacitive element. In the figure, the drive voltage (piezo voltage) of the piezoelectric element 2 is designated by a reference numeral 31 and is indicated by a solid line, and the voltage of the capacitive element 6 (capacitor voltage) is indicated by a reference numeral 32 and is indicated by a broken line.

The switching operation (push-pull operation) by the switching unit 7 will be described with reference to FIGS. 1 and 2. As shown in FIG. 2, the drive voltage 31 of the piezoelectric element 2 and the voltage 32 of the capacitive element 6 change in opposite phase due to the switching operation (push-pull operation) of the switching unit 7. In FIG. 2, the section indicated by reference numeral 33 is a section in which the capacitive element 6 is discharged and the piezoelectric element 2 vibrates the work 90 due to the inverse piezoelectric effect. The section indicated by reference numeral 34 is a section in which the piezoelectric element 2 receives a force from the work 90 and the capacitive element 6 is regeneratively charged by the voltage generated by the piezoelectric effect.

In the section 33, the NPN transistor 71 is turned on and the PNP transistor 72 is turned off in the switching unit 7, and the push-pull circuit of the switching unit 7 performs a push operation. The voltage due to the electric energy stored in the capacitive element 6 is applied to the piezoelectric element 2 through the nodes N2 and N3, the NPN transistor 71, and the node N4 shown in FIG.

In the section 34, the NPN transistor 71 is turned off and the PNP transistor 72 is turned on in the switching unit 7, and the push-pull circuit of the switching unit 7 performs a pull operation. The voltage generated when the piezoelectric element 2 receives a force from the work 90 is applied to the capacitive element 6 through the node N4, the rectifying element 73, and the nodes N3 and N2 shown in FIG.

As described above, in the vibration device 10 according to the embodiment, the operation due to the inverse piezoelectric effect and the operation due to the piezoelectric effect of the piezoelectric element 2, the charging / discharging of the electric energy of the capacitive element 6, and the push-pull operation of the switching unit 7 are performed. Works in harmony with each other. As a result, the burden on the power supply voltage of the battery 1 when operating the vibration exciter 10 is reduced, and the miniaturization of the rated capacity and dimensions of the battery 1 is promoted. When the battery 1 is miniaturized, the vibrating device 10 is also miniaturized and lightened.

When the miniaturization and large capacity of the battery 1 are promoted due to the advancement of the technology related to the secondary battery, the vibration exciter 10 does not use the capacitance element 6 and the switching unit 7 while keeping its size miniaturized. The piezoelectric element 2 can be continuously driven in a short period of time by using only the power supply voltage supplied from the battery 1. The drive circuit 5 including the capacitive element 6 and the switching unit 7 has an arbitrary configuration.

[Usage of the device]
FIG. 3 is a diagram schematically showing a configuration of a machine tool to which a wireless vibration exciter according to an embodiment of the present invention is attached. FIG. 4 is a perspective view showing the appearance of the wireless vibration exciter according to the embodiment of the present invention. As shown in FIG. 3, the wireless vibration exciter 10 according to the embodiment is used by being attached to a machine tool 20 such as an NC milling machine or a machining center when measuring the dynamic rigidity of the workpiece 90 (work 90). To.

The machine tool 20 of the exemplary embodiment is a machine tool having three drive axes (X-axis, Y-axis and Z-axis) orthogonal to each other. The machine tool 20 has a bed 21, a column 22 that can move in the Y-axis direction on the bed 21, a saddle 23 that can move in the Z-axis direction along the column 22, and a saddle having a rotatable spindle 241. It includes a spindle device 24 attached to 23, a tool holder 25 attached to the tip end side of the spindle 241, a table 26 movable in the X-axis direction on the bed 21 and on which a work 90 is placed, and a control device 29. .. The operation of the machine tool 20 including the control of each drive shaft and the control of the spindle 241 is controlled by the control device 29. In an exemplary embodiment, the control device 29 is, for example, a personal computer and is communicably connected to the machine tool 20. While the machine tool 20 processes the work 90, the position of the work 90 on the table 26 is fixed by the jig 27.

While the machine tool 20 performs a machining process on the work 90, a rotary tool such as an end mill or a milling cutter corresponding to each machining process is attached to the tip of the tool holder 25. The vibration exciter 10 is used as one step in the machining process of the work 90 using the machine tool 20 by attaching it in place of the rotary tool before each machining process is started. For example, when the machine tool 20 is a machining center, the vibration exciter 10 is usually stored or mounted in a tool magazine (not shown) of the machine tool 20, and the automatic tool change of the machining center is performed before each machining process is started. (Automatic Tool Changer, ATC) It can be installed in place of a rotary tool by the function. In the exemplary embodiment, the vibrating device 10 is attached to the tool holder 25, and the vibrating device 10 is replaced with a rotary tool as a set with the tool holder 25.

The control device 29 wirelessly transmits information regarding the drive voltage of the piezoelectric element 2 to the control unit 4 of the vibration device 10. The control device 29 operates each part of the machine tool 20 to bring the piezoelectric element 2 of the vibration device 10 into contact with the measurement point 91 of the work 90. In an exemplary embodiment, the work 90 is a cylindrical hollow component and the measurement point 91 is a thin side wall of the work 90. The control unit 4 of the vibration device 10 drives the piezoelectric element 2 based on the information regarding the drive voltage of the piezoelectric element 2 transmitted from the control device 29, and vibrates the measurement point 91 of the work 90. The vibrating device 10 measures the force received from the measuring point 91 while vibrating the measuring point 91. The vibration of the measurement point 91 is performed by the piezoelectric element 2 of the vibration device 10, and the force is measured by the force sensing unit 3 of the vibration device 10.

After the force is measured by the vibrating device 10, the control device 29 wirelessly receives information indicating the force obtained by the measurement from the control unit 4 of the vibrating device 10. Generally, the correspondence between the drive voltage and the displacement amount in the piezoelectric element is grasped in advance as the performance characteristic of the so-called piezoelectric element. That is, the information regarding the displacement of the work 90 caused by the vibration caused by the piezoelectric element 2 corresponds to the information regarding the drive voltage of the piezoelectric element 2 transmitted by the control device 29 to the vibration device 10, and the control device 29 has received the information. The data 291 regarding the dynamic rigidity of the work 90 is calculated based on the information indicating the force and the information regarding the drive voltage of the piezoelectric element 2 transmitted to the vibration exciter 10. In this embodiment, the mechanical compliance is calculated from the displacement and the force as the values used for evaluating the dynamic rigidity of the work 90.

The control device 29 evaluates the vibration characteristics of the work 90 based on the calculated dynamic rigidity data 291. As a result, the control device 29 reexamines the machining conditions such as the rotation speed of the spindle 241 and the cutting depth by the rotary tool, and the feed rate of the spindle 241 suitable for the next machining step to be applied immediately afterwards. The machining process can be applied to the work 90 under the appropriate machining conditions examined just before the start of each machining step. For example, the control device 29 applies the machining process to the work 90 under the machining conditions of the machine tool 20 in which the vibration frequency at which the displacement of the work 90 becomes large can be avoided. As a result, the work 90 is cut off as the processing process progresses, and even if the thickness of the work 90 changes in each processing process, it is possible to suppress a decrease in the processing accuracy of the work 90.

As described above, according to the present invention, it is possible to provide a vibration exciter that can be easily used when measuring the dynamic rigidity of a work.

According to the vibration device 10 according to the embodiment, the vibration device 10 is used by being attached to the spindle 241 of the machine tool 20 instead of the rotary tool, and the machine tool 20 is used for measuring the dynamic rigidity of the work 90. It is performed as one step in the processing process of the work 90. The measured information indicating the force of the work 90 is wirelessly transmitted from the vibration exciter 10 to the control device 29. As a result, the vibration exciter 10 can easily measure the dynamic rigidity of the work 90 before each processing step is started. Since the communication between the vibration exciter 10 and the control device 29 is made wireless, even when the vibration exciter 10 is automatically attached instead of the rotary tool by the automatic tool change function of the machining center, the communication cable is used. There is no need to consider handling, and replacement work can be performed smoothly.

Further, the vibration exciter 10 includes the drive circuit 5, and the drive circuit 5 includes the capacitance element 6 and the switching unit 7, so that the capacitive element can be operated according to the operation due to the inverse piezoelectric effect of the piezoelectric element 2 or the operation due to the piezoelectric effect. Electrical energy is charged and discharged to 6. As a result, the piezoelectric element 2 can use the voltage due to the electric energy stored in the capacitive element 6 as the drive voltage in addition to the power supply voltage supplied from the battery 1. As a result, the battery 1 can be miniaturized, and the miniaturization and weight reduction of the vibration exciter 10 are promoted. When the dimensions of the vibrating device 10 are reduced, for example, in a machine tool 20 such as a machining center, the vibrating device 10 can be easily stored or mounted in a tool magazine in the same way as other rotary tools, and the machine tool As one step in the machining process of the work 90 using 20, it becomes possible to more easily evaluate the vibration characteristics of the work 90 before each machining step is started.

[Other forms]
Although the present invention has been described above by the specific embodiment, the present invention is not limited to the above-described embodiment.

In the above-described embodiment, the control device 29 that has received the information indicating the force from the vibration device 10 calculates the data 291 regarding the dynamic rigidity of the work 90, but the calculation of the data 291 regarding the dynamic rigidity is the control device 29. Instead of, the control unit 4 of the vibration device 10 may perform the operation. That is, the control unit 4 calculates the dynamic rigidity of the work 90 based on the information indicating the force and the information regarding the displacement of the work 90 caused by the vibration, and transfers the calculated dynamic rigidity information to the control device 29. It may be transmitted wirelessly. As described above, the correspondence between the drive voltage and the displacement amount in the piezoelectric element is grasped in advance as the performance characteristic of the piezoelectric element, and the information regarding the displacement of the work 90 caused by the vibration is transmitted by the control device 29 to the vibration device. It corresponds to the information regarding the drive voltage of the piezoelectric element 2 transmitted to 10.

In the above-described embodiment, the mechanical compliance is calculated from the displacement and the force as the value used for the evaluation of the dynamic rigidity of the work 90, but the apparent stiffness is calculated as the value used for the evaluation of the dynamic rigidity. , The calculated apparent stiffness may be used for the evaluation of the dynamic rigidity of the work 90. Further, mobility and inertia may be calculated as values used for evaluating the dynamic rigidity of the work 90. Velocity can be calculated from velocity and force by deriving velocity from the derivative of displacement. The inertia can be calculated from the acceleration and the force by deriving the acceleration from the derivative value of the velocity.

In the above-described embodiment, the waveform of the drive voltage applied to the piezoelectric element 2 controlled by the control unit 4 is exemplified by an impulse waveform, a sine wave, a triangular wave, a rectangular wave, a sweep sine wave, a sweep triangular wave, and a sweep rectangular wave. However, the waveform of the drive voltage applied to the piezoelectric element 2 is not limited to these examples. The control unit 4 can apply the drive voltage of the piezoelectric element 2 to the piezoelectric element 2 with an arbitrary waveform.

In the above-described embodiment, the control device 29 is a personal computer and is communicably connected to the machine tool 20, but the aspect of the control device 29 is not limited to this. The control device 29 may be provided separately from the machine tool 20, or may be integrated with the machine tool 20. For example, a computerized numerical control device (Numerical Control, NC) provided in a general machine tool can be used as the control device 29. It suffices that the control device 29 can directly or indirectly control the operation of the machine tool 20 and can communicate wirelessly with the control unit 4 of the vibration device 10.

In the above-described embodiment, the control device 29 uses the information regarding the drive voltage of the piezoelectric element 2 transmitted to the vibration exciter 10 when calculating the data 291 regarding the dynamic rigidity of the work 90, but the control device 29 uses the information. , Data 291 may be calculated using the measured value of the applied voltage actually applied to the piezoelectric element 2 instead of the information regarding the drive voltage transmitted to the vibration apparatus 10. In this case, for example, a voltage detector is provided in the piezoelectric element 2, the applied voltage actually applied to the piezoelectric element 2 is actually measured, and the measured value of the applied voltage to the piezoelectric element 2 is measured by the control unit 4 from the control device 29. It is good to send wirelessly to. The control unit 4 may store the measured value of the applied voltage in the memory.

[Example]
In the following examples, a prototype of the vibration exciter according to the present invention was manufactured and its performance was evaluated. Table 1 shows an outline of the manufactured prototype.

As the battery, a thin, large-capacity (rated capacity 1.5 AH), laminated sheet type lithium-ion battery with low internal resistance was used. The internal resistance of the battery used was 6.5 mΩ when a high frequency of 1 kHz was applied. As the piezoelectric element, a laminated piezoelectric actuator "TOKIN ASL170C801" series manufactured by Tokin Corporation was used. For the force sensing unit, a crystal piezoelectric force sensor "9134B" manufactured by KISTLER Group, Switzerland was used. For the control unit, "Raspberry Pi 3 Model B +" by the Raspberry Pi Foundation in the United Kingdom was used. Eight commercially available electric field capacitors having a capacitance of 1000 μF were connected in parallel to the capacitive element. The combined capacitance was about 8000 μF. For the switching unit, "Si7172ADP" and "Si7431DP", which are N-Channel MOSFETs and P-Channel MOSFETs manufactured by Vishay Siliconix of the United States, were used.

In Example 1, the vibration displacement was measured by measuring the displacement of the tip of the piezoelectric actuator in the vibration under no load, in which the piezoelectric actuator is not pressed against the object. The displacement of the tip of the piezoelectric actuator was measured using a triangulation type laser displacement meter. The measurement conditions were an applied voltage of 50 V, a vibration frequency of 1 Hz to 2000 Hz, a vibration time of 10 seconds, and a sampling frequency of 100 kHz. The measurement results are shown in FIG.

FIG. 5A is a graph showing a time waveform of the tip displacement of the piezoelectric actuator, and FIG. 5B is a spectrogram of the tip displacement of the piezoelectric actuator. In the spectrogram shown in (B), the frequency data in which the power / frequency (dB / Hz) ratio is high and is displayed in white in the figure is the data of the frequency component contained in a large amount during the vibration.

As shown in (A), it was confirmed that the tip of the piezoelectric actuator was displaced by about 8 μm during the vibration time of about 10 seconds. As shown in white in the figure in (B), it was confirmed that the frequency changed linearly from about 0 Hz to about 2000 Hz and was swept during the vibration for about 10 seconds.

In Example 2, a prototype of the vibration exciter was attached to the spindle of the machining center, and a flat plate vibration experiment was conducted on the machining center to measure compliance. In addition, an impact test (hammering test) using an impulse hammer and an accelerometer was performed on the flat plate on the machining center to measure compliance. Compliance measurements in both measurements were compared. The thickness of the flat plate was about 10 mm. The comparison result of the measured values is shown in FIG.

FIG. 6 is a graph showing the measured values of compliance. As shown in (A) to (E), the compliance was measured a plurality of times by changing the combination of the static pressing amount by the exciter and the amplitude of the operating voltage (applied voltage) of the piezoelectric actuator. .. The dark line data indicated by reference numeral 61 is the measurement data obtained by the prototype of the vibration exciter, and the light line data indicated by the reference numeral 62 is the measurement data obtained by the impact test (hammering test). (A) is a graph of measured values when the static pressing amount by the exciter is 40 μm and the amplitude of the operating voltage of the piezoelectric actuator is 50 V. Similarly, (B) is a graph of measured values when the static pressing amount is 80 μm and the amplitude of the operating voltage is 50 V. (C) is a graph of measured values when the static pressing amount is 120 μm and the amplitude of the operating voltage is 50 V. (D) is a graph of measured values when the static pressing amount is 40 μm and the amplitude of the operating voltage is 25 V. (E) is a graph of measured values when the static pressing amount is 80 μm and the amplitude of the operating voltage is 25 V.

In each of the graphs (A) to (E), attention is paid to the data showing the relationship between the amplitude and the frequency shown in the upper row. The dark line data indicated by reference numeral 61 and the light line data indicated by reference numeral 62 generally had the same frequency value at which the amplitude showed a peak. From this, it was confirmed that the measurement data of the prototype of the vibration exciter of the present invention showed a good correspondence with the conventional impact test (hammering test).

1 Battery 2 Piezoelectric element 3 Force sensing unit 4 Control unit 5 Drive circuit 6 Capacitive element 7 Switching unit 8 Voltage control unit 10 Wireless vibration exciter 11 Charging connector 12 Amplifier 13 Booster circuit 20 Machine tool 21 Bed 22 Column 23 Saddle 24 Main shaft device 25 Tool holder 26 Table 27 Judge 28 Charging device 29 Control device 291 Data 71 NPN transistor 72 PNP transistor 73 Rectifier element 74 Rectifier element 90 Work piece (work)
91 Measurement point 241 Headstock

Claims (6)

A piezoelectric element that is connected to a battery and vibrates the workpiece by the inverse piezoelectric effect when a drive voltage is applied.
A force sensing unit that senses the force received from the workpiece while the workpiece is being vibrated.
A control unit that wirelessly transmits the detected information indicating the force to a control device that controls the processing of the workpiece.
A wireless vibration exciter equipped with. The capacitive element connected to the piezoelectric element and
It is switched between applying the voltage due to the electric energy stored in the capacitive element to the piezoelectric element or applying the voltage generated by the piezoelectric element receiving the force from the workpiece to the capacitive element. Switching part and
The wireless vibration exciter according to claim 1. The wireless vibration exciter according to claim 1 or 2, wherein the control unit drives the piezoelectric element while changing the drive frequency. The wireless vibrating device according to any one of claims 1 to 3, wherein the control unit transmits information regarding the communication quality of wireless communication with the control device to the control device. The control unit
The dynamic rigidity of the work piece is calculated based on the information indicating the force and the information on the displacement of the work piece caused by the vibration.
The wireless vibration exciter according to any one of claims 1 to 4, wherein the calculated information indicating the dynamic rigidity is wirelessly transmitted to the control device. A drive circuit for a piezoelectric element provided in the wireless vibration exciter according to any one of claims 1 to 5.
The capacitive element connected to the piezoelectric element and
A switching unit that switches between applying a voltage due to the electric energy stored in the capacitive element to the piezoelectric element or applying a voltage generated by the piezoelectric element receiving a force from a workpiece to the capacitive element. And, the drive circuit of the piezoelectric element.

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