Drive circuit device and vibration conveying device

Abstract

To provide a drive circuit device for driving a plurality of capacitive loads, capable of suppressing unintended fluctuations in voltage applied to each capacitive load.SOLUTION: A drive circuit device 50 includes: a capacitor 66 that is a power source for a first capacitive load 73; a first leg 71; a second leg 72; a capacitor 69 that is a power source for a second capacitive load 83; a third leg 81; and a fourth leg 82. The first capacitive load 73 is arranged between a first terminal T1 and a second terminal T2. The first capacitive load 73 is arranged between a third terminal T3 and a fourth terminal T4. The second terminal T2 and the fourth terminal T4 are electrically short-circuited. The capacitor 66 and the capacitor 69 are electrically insulated from each other.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a drive circuit device for driving a capacitive load and a vibration transfer device including the drive circuit device.

Background Art

[0002] Patent Document 1 discloses a parts feeder that conveys conveyed products by vibrating a conveyance unit to which a piezoelectric element (capacitive load) is attached. The parts feeder has a so-called half-bridge inverter circuit as a power supply circuit (drive circuit) for applying an alternating voltage to the piezoelectric element. The half-bridge inverter circuit includes a DC power supply and a pair of switching elements (also called legs) connected in series with the DC power supply. The piezoelectric element is disposed between a terminal (first terminal) disposed between the pair of switching elements and a terminal (second terminal) having a zero potential. Also, a reactor having an inductance component is connected in series with the piezoelectric element between the first terminal and the second terminal. By applying switching signals having a predetermined frequency with a phase difference of 180° to the pair of switching elements, a potential difference of the predetermined frequency is generated between the first terminal and the second terminal. Due to such a potential difference, the piezoelectric element is driven at the predetermined frequency. Hereinafter, the predetermined frequency is referred to as a drive frequency.

[0003] The above half-bridge inverter circuit is applicable to each of the two piezoelectric elements provided in the linear feeder described in Patent Document 2. The linear feeder is configured to drive the two piezoelectric elements at a drive frequency close to both the resonant frequency of one piezoelectric element and its surrounding area (first resonant frequency) and the resonant frequency of the other piezoelectric element and its surrounding area (second resonant frequency). In the linear feeder, control is performed to maintain the difference between the phase of the AC voltage applied to one piezoelectric element and the phase of the AC voltage applied to the other piezoelectric element at a predetermined value (90°). As a result, a traveling wave is generated in the conveying section provided in the linear feeder for stable and high-speed conveyance of the conveyed items. The linear feeder also has a tracking means that automatically adjusts the drive frequency to an optimal value. The tracking means is configured to adjust the drive frequency so that the amplitude of vibration of the conveying section due to one piezoelectric element and the amplitude of vibration of the conveying section due to the other piezoelectric element are approximately the same. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-193432 [Patent Document 2] Japanese Patent Publication No. 2019-193340 [Overview of the project] [Problems that the invention aims to solve]

[0005] The first and second resonant frequencies described above generally fluctuate due to factors such as temperature rise during the operation of each piezoelectric element. The tracking means described above adjusts the drive frequency to follow these fluctuations. However, it has been found that when the drive frequency is adjusted near the first and second resonant frequencies, the transport of the transported items becomes unstable. The inventors of this invention have found that the cause of the transport instability is that the amplitude and phase of the AC voltage applied to each piezoelectric element in the half-bridge inverter circuit described above change rapidly near their respective resonant frequencies.

[0006] The objective of the present invention is to suppress unintended fluctuations in the voltage applied to each capacitive load in a drive circuit device that drives multiple capacitive loads. [Means for solving the problem]

[0007] The drive circuit device of the first invention is a drive circuit device for driving a first capacitive load having a first capacitive component and a second capacitive load having a second capacitive component, comprising: a first DC power supply which is the power supply for the first capacitive load; a first leg having a pair of first switching elements connected in series with the first DC power supply; a second leg having a pair of second switching elements connected in parallel with the pair of first switching elements; a second DC power supply which is the power supply for the second capacitive load, separate from the first DC power supply; a third leg having a pair of third switching elements connected in series with the second DC power supply; and a pair connected in parallel with the pair of third switching elements. The DC power supply comprises a fourth leg having a fourth switching element, wherein the first capacitive load is positioned between a first terminal positioned between the pair of first switching elements in the first leg and a second terminal positioned between the pair of second switching elements in the second leg, and the second capacitive load is positioned between a third terminal positioned between the pair of third switching elements in the third leg and a fourth terminal positioned between the pair of fourth switching elements in the fourth leg, the second terminal and the fourth terminal are electrically short-circuited, and the first DC power supply and the second DC power supply are electrically isolated from each other.

[0008] The inventors of the present invention have found that in conventional half-bridge inverter circuits, the amplitude and phase of the AC voltage applied to a capacitive load near the resonant frequency of the capacitive load change significantly due to the impedance of the reactor. Therefore, the inventors conceived of suppressing changes in the voltage applied to the capacitive load by removing the reactor or making the inductance of the reactor very small. However, simply removing the reactor in a half-bridge inverter circuit prevents the release of charge from the capacitive load when both of the pair of switching elements are turned off (i.e., the capacitive load cannot discharge). As a result, it was found that even if the duty cycle of the switching signals applied to the pair of switching elements is changed, the effective value of the voltage applied to the capacitive load cannot be changed, and the effective value cannot be controlled (details will be explained in the embodiments described later).

[0009] Therefore, in the present invention, first, a first capacitive load is placed between the first terminal of the first leg and the second terminal of the second leg, and a second capacitive load is placed between the third terminal of the third leg and the fourth terminal of the fourth leg. In other words, each of the first and second capacitive loads is connected to a full-bridge inverter circuit. In the full-bridge inverter circuit, the discharge path for the first capacitive load can be secured by maintaining the state in which either one of the pair of first switching elements and either one of the pair of second switching elements is turned on. Similarly, the discharge path for the second capacitive load can also be secured. In this configuration, the effective value of the voltage applied to the first capacitive load can be adjusted by controlling the phase difference between the switching signal to the first leg and the switching signal to the second leg. Similarly, the effective value of the voltage applied to the second capacitive load can also be adjusted. Details will be described in the embodiments described later.

[0010] Furthermore, in this invention, the second terminal and the fourth terminal are electrically short-circuited. This ensures that one terminal of the first capacitive load and one terminal of the second capacitive load are at the same potential. Moreover, in this invention, the first DC power supply and the second DC power supply are electrically isolated from each other. This prevents short circuits between the first DC power supply and the second DC power supply, regardless of the operating state of each switching element. Therefore, failure of the drive circuit device due to such a short circuit can be prevented.

[0011] Based on the above, in a drive circuit device that drives multiple capacitive loads, unintended fluctuations in the voltage applied to each capacitive load can be suppressed.

[0012] The vibration conveying device of the second invention is a vibration conveying device comprising a drive circuit device of the first invention and a conveying unit configured to convey an object when driven by the drive circuit device, wherein the first capacitive load includes a first piezoelectric element configured to vibrate the conveying unit, and the second capacitive load includes a second piezoelectric element configured to vibrate the conveying unit.

[0013] In this invention, even when the drive frequency is adjusted near the resonant frequencies of the first capacitive load and the second capacitive load, abrupt changes in the amplitude and phase of vibrations of the transport section by the first piezoelectric element and abrupt changes in the amplitude and phase of vibrations of the transport section by the second piezoelectric element can be suppressed. Therefore, parts can be transported stably. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view of the parts feeder according to this embodiment. [Figure 2] This is a plan view of a linear feeder. [Figure 3] (a) is a cross-sectional perspective view of the linear feeder, and (b) is a cross-sectional view taken along line III(b)-III(b) in Figure 2. [Figure 4] (a) to (c) are schematic diagrams of the driving mechanism. [Figure 5] This is a schematic diagram showing the configuration of the traveling wave generation unit. [Figure 6] This is an explanatory diagram of the traveling waves generated on the transport surface. [Figure 7] This is a circuit diagram showing a conventional drive circuit device having a reactor. [Figure 8] (a) and (b) are graphs showing the switching signals applied to a conventional drive circuit device, and (c) and (d) are graphs showing the voltage applied to a predetermined part. [Figure 9] (a) is a graph showing the drive frequency dependence of the amplitude of the AC voltage applied to the piezoelectric element, and (b) is a graph showing the drive frequency dependence of the phase of the said AC voltage. [Figure 10] (a) to (d) are graphs showing the control signals or voltages in a configuration in which the reactor is simply removed from a conventional drive circuit device. [Figure 11] This is a circuit diagram showing the drive circuit device according to this embodiment. [Figure 12] (a) to (d) are graphs showing the switching signals applied to the drive circuit device. [Figure 13](a) to (c) are each graphs showing the voltage applied to a predetermined part in the drive circuit device.

Embodiments for Carrying out the Invention

[0015] Next, embodiments of the present invention will be described. For convenience of explanation, the directions shown in FIG. 1 are taken as the front-back, left-right, and up-down directions. The up-down direction is the vertical direction in which gravity acts. The front-back direction is a predetermined direction orthogonal to the up-down direction. The left-right direction is a direction orthogonal to both the up-down direction and the front-back direction.

[0016] (Schematic Configuration of Parts Feeder) The schematic configuration of the parts feeder 1 according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a perspective view of the parts feeder 1. The parts feeder 1 includes a bowl feeder 2 and a linear feeder 3 (the vibration conveying device of the present invention). The bowl feeder 2 is a device for supplying the workpiece W (the conveyed product of the present invention) to the linear feeder 3. The linear feeder 3 is connected to the front end of the bowl feeder 2. Both the bowl feeder 2 and the linear feeder 3 convey the workpiece W using a flexural progressive wave. In the present embodiment, the case where the present invention is applied to the linear feeder 3 will be described. It should be noted that it is also possible to apply the present invention to the bowl feeder 2.

[0017] The bowl feeder 2 has a bowl body 11 in which the workpiece W is accommodated. The bowl body 11 is a member having a substantially inverted frustum shape. The bowl body 11 has an open upper portion. A spiral track 12 that rises spirally from the bottom is formed on the inner peripheral wall of the bowl body 11. The bowl body 11 is vibrated by bowl driving means (not shown). The workpiece W rises along the spiral track 12 toward the linear feeder 3.

[0018] The linear feeder 3 is configured to transport workpieces W supplied from the bowl feeder 2 forward. The linear feeder 3 has a transport section 21 and a traveling wave generation section 22. The transport section 21 is a component that generates deflected traveling waves. The traveling wave generation section 22 is configured to ultrasonically vibrate the transport section 21. When the traveling wave generation section 22 vibrates the transport section 21, deflected traveling waves are generated on the transport surface 31 formed on the upper surface of the transport section 21. These deflected traveling waves transport the workpieces W forward along the transport surface 31 and supply them to the next process.

[0019] (Detailed configuration of the linear feeder) Next, the detailed configuration of the linear feeder 3 will be described. As mentioned above, the linear feeder 3 has a transport unit 21 and a traveling wave generation unit 22.

[0020] The transport section 21 will be described with reference to Figures 2, 3(a), and 3(b). Figure 2 is a plan view of the linear feeder 3. Figure 3(a) is a cross-sectional perspective view of the linear feeder 3. Figure 3(b) is a cross-sectional view taken along line III(b)-III(b) in Figure 2, which is a cross-sectional view perpendicular to the front-rear direction of the linear feeder 3.

[0021] The conveying section 21 is, for example, a roughly flat metal plate. The conveying section 21 is roughly rectangular when viewed from above. The conveying section 21 has a roughly concave cross-section perpendicular to its longitudinal direction (see Figure 3(b)). As shown in Figures 2, 3(a), and 3(b), the conveying section 21 has a fixed section 21F and a vibrating section 21V. In Figure 3(b), the area enclosed by the dashed-dotted line is the fixed section 21F, and the area enclosed by the double-dotted line is the vibrating section 21V. The fixed section 21F is the part formed in the center of the conveying section 21 in a plan view. The fixed section 21F is a roughly oval-shaped part with a smaller thickness than the peripheral part in a plan view. The fixed section 21F is sandwiched between the retaining plates 38 and 39 in the vertical direction and fixed to the retaining plates 38 and 39 by a plurality of fasteners 40. The vibrating section 21V is the part formed on the outside of the fixed section 21F in a plan view. The vibrating part 21V is the part that is thicker than the fixed part 21F.

[0022] As shown in Figure 3(b), the vibrating section 21V is roughly rectangular in cross-sectional view. A transport track 27 (see hatched area in Figure 2) is formed on the upper surface of the vibrating section 21V. The transport track 27 is a groove through which the workpiece W is transported. The transport track 27 has a main track 28 and a return track 29. The main track 28 is a path for supplying the workpiece W to the next process apparatus. The main track 28 extends from the rear end to the front end of the transport section 21. The main track 28 has a transport surface 31 on which the workpiece W rests. The return track 29 is a path for returning some of the workpiece W to the bowl feeder 2. The return track 29 has a transport surface 32 that is roughly U-shaped in plan view.

[0023] The traveling wave generation unit 22 will be explained with reference to Figures 4(a) to 4(c) and Figure 5. Figures 4(a) to 4(c) show the driving means 23, which will be described later. Figure 4(a) is a plan view of the driving means 23. Figure 4(b) is a side view of the driving means 23. Figure 4(c) is a rear view of the driving means 23. Figure 5 is a schematic diagram showing the configuration of the traveling wave generation unit 22.

[0024] The traveling wave generation unit 22 includes, for example, two driving means 23 (driving means 23a, 23b), a switching signal generation unit 41, and a driving circuit unit 42 (see Figure 5). The traveling wave generation unit 22 is configured such that the driving circuit unit 42 vibrates the two driving means 23 based on the switching signal generated by the switching signal generation unit 41. In this embodiment, the device having the vibrating unit 21V, the driving means 23a, 23b, and the driving circuit unit 42 is called the driving circuit device 50. More details of the driving circuit device 50 will be described later.

[0025] The two drive means 23 are configured to vibrate the vibrating part 21V by extending and contracting along the vibrating part 21V. The two drive means 23 are attached to the back surface of the transport track 27 of the vibrating part 21V (see Figures 3(a) and 3(b)). More specifically, the transport track 27 has two straight sections, each extending in the front-rear direction. The two straight sections are located on opposite sides of each other in the left-right direction, separated by a fixed section 21F. One of the two drive means 23 is attached to the back surface of one of the straight sections. The other drive means 23 is attached to the back surface of the other straight section.

[0026] Each driving means 23 has, for example, four piezoelectric elements 16, as shown in Figures 4(a) to 4(c). Each piezoelectric element 16 is an element that deforms when a voltage is applied.

[0027] As a more specific example of the configuration, the four piezoelectric elements 16 each have a ceramic portion 17, four electrodes 18, and one electrode 19. The ceramic portion 17 is a rectangular, thin plate-shaped member. The four electrodes 18 are attached to the upper surface (referred to as the front surface for convenience of explanation) of the ceramic portion 17 when viewed from above. The electrode 19 is attached to the lower surface (referred to as the back surface for convenience of explanation) of the ceramic portion 17 when viewed from above.

[0028] The ceramic portion 17 is a piezoelectric ceramic component that bends when a voltage is applied. The ceramic portion 17 extends for a long distance along a predetermined direction. The ceramic portion 17 is a common component in the four piezoelectric elements 16. When a predetermined wavelength is denoted as λ, the ceramic portion 17 is polarized so that its polarity (+, -) alternates at intervals of λ / 2 in the predetermined direction. The four electrodes 18 are attached to the surface of the polarized portion of the ceramic portion 17 at intervals of λ / 2 in the predetermined direction. The electrode 19 is for making the potential on the back surface of the ceramic portion 17 the same potential (common potential). The electrode 19 has an area approximately the same as the back surface of the ceramic portion. The electrode 19 is also a common component in the four piezoelectric elements 16. With these configurations, the four piezoelectric elements 16 are arranged at intervals of λ / 2 in the predetermined direction, with their polarity alternately reversing.

[0029] A drive means 23a is positioned on the back surface of one straight section of the transport track 27. A drive means 23b is positioned on the back surface of the other straight section of the transport track 27. The drive means 23a has four piezoelectric elements 16a (first piezoelectric elements of the present invention). Each piezoelectric element 16a has a capacitive component (first capacitive component of the present invention). The drive means 23b has four piezoelectric elements 16b (second piezoelectric elements of the present invention). Each piezoelectric element 16b has a capacitive component (second capacitive component of the present invention). There is a distance of (n+1 / 4)λ along the vibrating section 21V between the center of the foremost piezoelectric element 16a of the four piezoelectric elements 16a and the center of the foremost piezoelectric element 16b of the four piezoelectric elements 16b (not shown). n is an integer greater than or equal to 0.

[0030] Alternatively, instead of electrode 19, four electrodes having an area similar to electrode 18 may be attached to the back surface, facing electrode 18 with the ceramic portion 17 in between. In that case, the potential of the four electrodes attached to the back surface can be made common, for example, by jumper wires. Furthermore, the number of piezoelectric elements 16 in each driving means 23 is not limited to four.

[0031] The switching signal generation unit 41 is configured to generate a plurality of switching signals to be sent to the drive circuit unit 42. The plurality of switching signals are signals for switching the on / off state of a plurality of switching elements (described later) in the drive circuit unit 42 at predetermined timings. The switching signal generation unit 41 is configured to generate and output switching signals having predetermined frequencies, duty cycles, and phases. The frequency of the switching signals may be, for example, in the ultrasonic range. The frequency of the switching signals may be automatically adjusted by, for example, the tracking unit 44, which will be described later. The switching signal generation unit 41 is electrically connected to the drive circuit unit 42. Details of the signals generated by the switching signal generation unit 41 will be described later. In Figure 5, the "first signal group" refers to a plurality of switching signals for operating the drive means 23a, among the plurality of switching signals sent to the drive circuit unit 42. Similarly, the "second signal group" refers to a plurality of switching signals for operating the drive means 23b.

[0032] The drive circuit unit 42 is configured to apply an AC voltage to two drive means 23 to excite the vibrating unit 21V. The drive circuit unit 42 is configured to output an AC voltage having a predetermined waveform, amplitude, frequency, and phase based on a plurality of switching signals sent from the switching signal generation unit 41. The drive circuit unit 42 is configured to output a first AC voltage applied to drive means 23a and a second AC voltage applied to drive means 23b. A plurality of switching signals are sent from the switching signal generation unit 41 to the drive circuit unit 42 such that the phases of the first AC voltage and the second AC voltage differ by 90° from each other. A more detailed configuration of the drive circuit unit 42 will be described later.

[0033] When the first AC voltage is applied to the driving means 23a and the second AC voltage is applied to the driving means 23b, the driving means 23a and 23b expand and contract. This generates two standing waves that vibrate only in the vertical direction throughout the entire vibrating section 21V. The wavelengths of the two standing waves are approximately equal to the aforementioned λ. The phases of the two standing waves are about 90° apart. The positions of the nodes of one standing wave and the other standing wave are shifted by approximately λ / 4. When the two standing waves overlap, a deflection traveling wave propagating in one direction is generated on the transport surfaces 31 and 32. The deflection traveling wave causes each point on the transport surfaces 31 and 32 to vibrate in the vertical and horizontal directions.

[0034] Furthermore, the traveling wave generation unit 22 includes, for example, a difference detection unit 43 and a tracking unit 44 (see Figure 5). The traveling wave generation unit 22 detects the difference in amplitude between two standing waves using the difference detection unit 43, and adjusts the frequency of the switching signal using the tracking unit 44 to bring the difference closer to zero. For further details, please refer to, for example, Japanese Patent Application Publication No. 2019-193340.

[0035] (Specific example of a deflected traveling wave) The deflection travel wave generated on the transport surface 31 will be explained with reference to Figures 6(a) to 6(d). Figures 6(a) to 6(d) are side views of the deflection travel wave generated on the transport surface 31. The deflection travel wave propagates in the direction indicated by the solid arrow in Figure 6(a) (backward) with a period T. The neutral axis N of the vibration of the vibrating section 21V is located, for example, at the center in the vertical direction of the vibrating section 21V.

[0036] Assume that at time t=0, a point mass Z on the transport surface 31 is in its highest position (see Figure 6(a)). Subsequently, point mass Z descends and moves forward, reaching its furthest forward position at time t=T / 4 (see Figure 6(b)). Furthermore, point mass Z is at its lowest position at time t=2T / 4 (see Figure 6(c)) and at its furthest rear position at time 3T / 4 (see Figure 6(d)). In this way, point mass Z moves in the vertical and longitudinal directions, tracing an elliptical orbit EO. ​​When point mass Z is at its highest position in the elliptical orbit EO, a horizontal (transport direction) thrust force is generated due to the frictional force between the transport surface 31 and the workpiece W, and the workpiece W is transported in the opposite direction to the direction of propagation of the deflected traveling wave. In this way, each part on the transport surface 31 moves in an elliptical motion such that it has a velocity component in the transport direction and a velocity component in the vertical direction, thereby transporting the workpiece W in the transport direction. The same applies to the transport surface 32.

[0037] (Problems with conventional drive circuits, etc.) Before describing the details of the drive circuit device 50 of this embodiment, the problems of the conventional drive circuit device 100 (see Figure 7) will be described below. More specifically, examples of the configuration of the drive circuit device 100, examples of switching signals for driving the drive circuit device 100, problems that occur in the drive circuit device 100, and problems that occur when the reactors 123 and 133 described later are removed from the drive circuit device 100 will be described.

[0038] First, the configuration of the drive circuit device 100 will be explained with reference to the circuit diagram in Figure 7. The drive circuit device 100 includes a power supply unit 101, a half-bridge inverter circuit 102, and a half-bridge inverter circuit 103 (refer to the parts enclosed by the dashed lines in Figure 7, respectively). The drive circuit device 100 is configured to drive the first capacitive load 124 by the half-bridge inverter circuit 102, which is driven by the power supply unit 101. The first capacitive load 124 includes the vibration unit 21V and the driving means 23a (see Figure 5) described above. The drive circuit device 100 is also configured to drive the second capacitive load 134, which includes the vibration unit 21V and the driving means 23b (see Figure 5) described above, by the half-bridge inverter circuit 103, which is also driven by the power supply unit 101.

[0039] The power supply unit 101 includes, for example, a DC power supply 111 and capacitors 112 and 113. The power supply unit 101 is configured to divide the power supply voltage of the DC power supply 111 (hereinafter referred to as Vs for convenience of explanation) by capacitors 112 and 113. Capacitors 112 and 113 are connected in series with the DC power supply 111. Capacitor 112 is electrically connected to the positive terminal of the DC power supply 111. Capacitor 113 is electrically connected to the negative terminal of the DC power supply 111. The capacitance of capacitor 112 and the capacitance of capacitor 113 are approximately equal. The potential of the terminals between capacitor 112 and capacitor 113 is the reference potential of the drive circuit device 100.

[0040] The half-bridge inverter circuit 102 is connected in series with the DC power supply 111. The half-bridge inverter circuit 102 includes switching elements 121 and 122, a reactor 123, and a first capacitive load 124. The switching elements 121 and 122 are, for example, general N-type field-effect transistors (FETs). Each of the switching elements 121 and 122 is turned on or off by a switching signal generated in the switching signal generation unit 41 (see Figure 5) described above. The switching signal is input to the gates of each switching element 121 and 122. The switching elements 121 and 122 are connected in series with the DC power supply 111. The drain of switching element 121 is connected to the positive terminal of the DC power supply. The source of switching element 121 is connected to the drain of switching element 122. The source of switching element 122 is connected to the negative terminal of the DC power supply. A pair of switching elements 121 and 122 arranged in this manner is generally called a leg. A freewheeling diode 121D is connected in parallel to switching element 121. A freewheeling diode 122D is connected in parallel to switching element 122. The configurations of switching elements 121 and 122 are not limited to those described above.

[0041] The reactor 123 is an element for suppressing abrupt changes in the current flowing through the first capacitive load 124. The reactor 123 has an inductance component. The reactor 123 is connected in series with the first capacitive load 124. One terminal of the reactor 123 is connected to the terminal between switching element 121 and switching element 122. The other terminal of the reactor 123 is connected to one terminal of the first capacitive load 124. The first capacitive load 124 includes the vibrating part 21V and the driving means 23a (see Figure 5) as described above. The first capacitive load 124 has a capacitive component. One end of the first capacitive load 124 is connected to the other terminal of the reactor 123. The other terminal of the first capacitive load 124 is connected to the terminal between capacitor 112 and capacitor 113. With the above configuration, the voltage applied across the reactor 123 and the first capacitive load 124 (hereinafter referred to as Vo for convenience of explanation) varies within the range of -Vs / 2 to +Vs / 2. The voltage applied across the first capacitive load 124 (hereinafter referred to as Vp for convenience of explanation) also varies within the range of -Vs / 2 to +Vs / 2.

[0042] The half-bridge inverter circuit 103 includes switching elements 131 and 132, a reactor 133, and a second capacitive load 134. The half-bridge inverter circuit 103 is connected in series with the DC power supply 111. The half-bridge inverter circuit 103 is connected in parallel with the half-bridge inverter circuit 102. The switching elements 131 and 132 have the same configuration as the switching elements 121 and 122 of the half-bridge inverter circuit 102, and are arranged in the same way within the half-bridge inverter circuit 103 as the switching elements 121 and 122. Freewheeling diodes 131D and 132D are connected in parallel to the switching elements 131 and 132, respectively.

[0043] The reactor 133 has the same configuration as the reactor 123 of the half-bridge inverter circuit 102 and is arranged in the same way as the reactor 123 within the half-bridge inverter circuit 103. The second capacitive load 134 includes the vibrating part 21V and the driving means 23b (see Figure 5) as described above. The second capacitive load 134 has a capacitive component. The second capacitive load 134 is arranged in the same way as the first capacitive load 124 within the half-bridge inverter circuit 103.

[0044] Next, examples of switching signals for driving the drive circuit device 100 will be explained with reference to Figures 8(a) to 8(d). In Figures 8(a) to 8(d), the horizontal axis of the graphs all represents time. Figure 8(a) is a graph showing the time change of the first switching signal applied to the switching element 121. The vertical axis of the graph in Figure 8(a) represents the on / off state of the first switching signal. Figure 8(b) is a graph showing the time change of the second switching signal applied to the switching element 122. The vertical axis of the graph in Figure 8(b) represents the on / off state of the second switching signal. Figure 8(c) is a graph showing the time change of Vo as described above. The vertical axis of the graph in Figure 8(c) represents Vo. Figure 8(d) is a graph showing the time change of Vp as described above. The vertical axis of the graph in Figure 8(d) represents Vp.

[0045] The following describes the operation of the half-bridge inverter circuit 102, one of the two half-bridge inverter circuits 102 and 103. A detailed explanation of the operation of the half-bridge inverter circuit 103 is omitted. In the half-bridge inverter circuit 103, the switching signal generation unit 41 (see Figure 5) generates a switching signal such that the phase of the AC voltage applied to the second capacitive load 134 is shifted by 90° relative to the phase of the AC voltage applied to the first capacitive load 124.

[0046] The half-bridge inverter circuit 102 is operated by the power supply unit 101 and the switching signal generation unit 41 (see Figure 5). The switching signal generation unit 41 can generate a first switching signal (see Figure 8(a)) applied to the switching element 121 and a second switching signal (see Figure 8(b)) applied to the switching element 122. The frequencies of the first switching signal and the second switching signal are approximately the same. For the sake of explanation, this frequency will be referred to as the switching frequency (fs). When the period of the first switching signal and the period of the second switching signal are Ts, Ts = 1 / fs (see Figures 8(a) and 8(b)). The phases of the first switching signal and the second switching signal are approximately 180° apart. The duty cycles of the first switching signal and the second switching signal are approximately the same. The duty cycles of both the first and second switching signals are 50% or less. In other words, when one of the first switching signal and the second switching signal is on, the other is off.

[0047] The time variation of Vo will be briefly explained step by step, referring to Figure 8(c). First, when the first switching signal is turned on at a predetermined timing, current flows through the switching element 121, reactor 123, first capacitive load 124, and capacitor 112. At this time, Vo becomes +Vs / 2. Also, the first capacitive load 124 is charged. When the first switching signal is turned off, the current flowing through reactor 123 is maintained, so current flows through the freewheeling diode 122D, reactor 123, first capacitive load 124, and capacitor 113. At this time, Vo becomes -Vs / 2. Note that this current decays over time, and Vo becomes zero (or approaches zero). Next, when the second switching signal is turned on, current flows through the switching element 122, reactor 123, first capacitive load 124, and capacitor 113. At this time, Vo becomes -Vs / 2. Furthermore, the first capacitive load 124 is charged. When the second switching signal is turned off, current flows through the freewheeling diode 121D, the reactor 123, the first capacitive load 124, and the capacitor 112. At this time, Vo becomes +Vs / 2. Through this repetition, Vo periodically changes between -Vs / 2 and +Vs / 2. The period of Vo is Ts as described above. The frequency of Vo is fs as described above. The waveform of the time variation of Vo is generally rectangular, as shown in Figure 8(c), for example. The RMS value of Vo changes according to the duty cycle of the first and second switching signals.

[0048] The waveform of Vp is smoother than that of Vo due to the suppression of current changes by the reactor 123 (see Figure 8(d)). The phase of Vp is slightly out of phase with respect to Vo. When Vp is applied to the first capacitive load 124, the driving means 23a and the vibrating part 21V vibrate. Similarly, when an AC voltage with a phase difference of approximately 90° from that of Vp is applied to the second capacitive load 134, the driving means 23b and the vibrating part 21V vibrate.

[0049] Next, the problems that occur in the drive circuit device 100 will be described. The switching frequency is set to be approximately equal to the resonant frequency of the first capacitive load 124 and the resonant frequency of the second capacitive load 134 in order to maximize the vibration efficiency (i.e., amplitude) of each drive means 23 and vibrating part 21V. Hereinafter, the resonant frequency of the first capacitive load 124 will be called the first resonant frequency, and the resonant frequency of the second capacitive load 134 will be called the second resonant frequency. The first and second resonant frequencies are, for example, in the ultrasonic range (20 kHz or higher). In addition, the switching frequency is frequently fine-tuned by the difference detection unit 43 and tracking unit 44 described above. The inventors of this application have found that when the switching frequency is fine-tuned, the transport of workpieces W by a conventional parts feeder (not shown) equipped with the drive circuit device 100 becomes unstable (for example, large fluctuations in transport speed).

[0050] The causes of transport instability will be explained with reference to Figures 9(a) and 9(b). Figure 9(a) is a graph showing the relationship between the effective value of Vp and the switching frequency. Figure 9(b) is a graph showing the relationship between the phase difference between Vo and Vp and the switching frequency.

[0051] When the first resonant frequency is denoted as f1, it was found that the effective value of Vp (see Figure 9(a)) and the phase difference between Vo and Vp (see Figure 9(b)) fluctuate significantly when the switching frequency changes near f1. This phenomenon occurs in both the first capacitive load 124 and the second capacitive load 134. Furthermore, it is generally difficult to make the first and second resonant frequencies exactly the same, resulting in some difference between them. As a result, the ratio of the amplitude of vibration of the first capacitive load 124 to the amplitude of vibration of the second capacitive load 134 fluctuates significantly with changes in the switching frequency. In addition, the phase difference between the vibration of the first capacitive load 124 and the vibration of the second capacitive load 134 also fluctuates significantly with changes in the switching frequency. Due to these fluctuations in phase difference, when the switching frequency is finely adjusted, the phase difference of the two standing waves described above fluctuates, making it difficult to generate a deflected traveling wave, and resulting in unstable transport of the workpiece W.

[0052] The inventors of this invention believe that the phase difference between Vo and Vp described above is due to the presence of reactors 123 and 133 in the drive circuit device 100. The reason for this is as follows: When the impedance of reactor 123 is ZL and the impedance of the first capacitive load 124 is Zp, the relationship between Vp and Vo is given by the following formula.

[0053] Vp = Vo × Zp / (ZL ​​+ Zp)

[0054] According to the above formula, by removing reactors 123 and 133 from the drive circuit device 100, ZL becomes substantially zero, and Vp becomes approximately equal to Vo. Furthermore, the RMS value and phase of Vo do not depend on the switching frequency. Therefore, if Vp is approximately equal to Vo, there will be no large changes in the RMS value and phase of Vp due to changes in the switching frequency. The inventors of this application have considered the above.

[0055] However, it was found that simply removing reactors 123 and 133 from the drive circuit device 100 would cause another problem. This problem will be explained with reference to Figures 10(a) to 10(d). Figures 10(a) and 10(b) are the same graphs as Figures 8(a) and 8(b), respectively. Figure 10(c) is a graph showing the time change of Vo, similar to Figure 8(c). Figure 10(d) is a graph showing the time change of Vp, similar to Figure 8(d).

[0056] In a configuration where reactors 123 and 133 are removed from the drive circuit device 100, Vp (≒Vo) behaves as follows: When the first switching signal (see Figure 10(a)) is turned on, Vo becomes +Vs / 2 (see Figure 10(c)). Also, since the current change is not suppressed by reactor 123, the first capacitive load 124 is charged instantaneously. Therefore, Vp becomes +Vs / 2 almost simultaneously with Vo becoming +Vs / 2 (see Figure 10(d)). When the first switching signal is turned off, the charge is not released from the first capacitive load 124, and Vo and Vp are maintained at +Vs / 2. When the second switching signal (see Figure 10(b)) is turned on, Vo becomes -Vs / 2 (see Figure 10(c)). Furthermore, because the current is not suppressed by the reactor 123, the first capacitive load 124 is charged instantaneously. Therefore, Vp becomes -Vs / 2 almost simultaneously with Vo becoming -Vs / 2 (see Figure 10(d)). When the second switching signal is turned off, the charge is not released from the first capacitive load 124, and Vo is maintained at -Vs / 2 (see Figure 10(c)). Due to this repetition, regardless of the duty cycle of the first and second switching signals, Vo and Vp become square waves with a 50% duty cycle. As a result, the effective value of Vp cannot be controlled. Therefore, simply removing the reactors 123 and 133 from the drive circuit device 100 will not allow the drive circuit device 100 to operate normally.

[0057] Therefore, in order to ensure that each capacitive load operates normally while suppressing unintended fluctuations in the voltage applied to each capacitive load, the drive circuit device 50 is configured as follows.

[0058] (Detailed configuration of the drive circuit) The detailed configuration of the drive circuit device 50 of this embodiment will be described with reference to the circuit diagram in Figure 11. The drive circuit device 50 includes a power supply unit 51, a full-bridge inverter circuit 52, and a full-bridge inverter circuit 53. The full-bridge inverter circuit 52 is a circuit for driving the first capacitive load 73, which will be described later. The full-bridge inverter circuit 53 is a circuit for driving the second capacitive load 83, which will be described later.

[0059] The power supply unit 51 includes an AC power supply 61, a first DC power supply unit 62, and a second DC power supply unit 63. The first DC power supply unit 62 is a DC power supply circuit for driving the full-bridge inverter circuit 52. The second DC power supply unit 63 is a DC power supply circuit for driving the full-bridge inverter circuit 53.

[0060] The first DC power supply unit 62, together with the AC power supply unit 61, constitutes, for example, a known isolated flyback converter. The first DC power supply unit 62 includes a transformer 64, a diode 65, and a capacitor 66 (the first DC power supply of the present invention). The transformer 64 is a device that transforms the power supply voltage (AC voltage) of the AC power supply unit 61 using electromagnetic induction. The transformer 64 has a primary coil and a secondary coil. The primary coil is connected in series with the AC power supply unit 61. The secondary coil is connected in series with the diode 65 and the capacitor 66. The diode 65 rectifies the transformed AC voltage. The capacitor 66 converts the AC voltage rectified by the diode 65 into a DC voltage.

[0061] The second DC power supply unit 63, like the first DC power supply unit 62, is combined with the AC power supply unit 61 to form, for example, an isolated flyback converter. The second DC power supply unit 63 includes a transformer 67, a diode 68, and a capacitor 69 (the second DC power supply of the present invention). The primary coil of the transformer 67 is connected in series with the AC power supply unit 61 and in parallel with the primary coil of the transformer 64. The secondary coil of the transformer 67 is connected in series with the diode 68 and the capacitor 69. The diode 68 has the same function as the diode 65. The capacitor 69 has the same function as the capacitor 66. The capacitor 69 is electrically isolated from the capacitor 66.

[0062] The full-bridge inverter circuit 52 has a first leg 71, a second leg 72, and a first capacitive load 73. The first leg 71 is connected in series with the first DC power supply unit 62. The first leg 71 has a pair of first switching elements 74 (first switching elements 74A and 74B). The first switching elements 74A and 74B are connected in series. A freewheeling diode 74AD is connected in parallel to the first switching element 74A. A freewheeling diode 74BD is connected in parallel to the first switching element 74B. A first terminal T1 is located between the first switching element 74A and the first switching element 74B.

[0063] The second leg 72 is connected in series with the first DC power supply unit 62 and in parallel with the first leg 71. The second leg 72 has a pair of second switching elements 75 (second switching elements 75A and 75B). The second switching elements 75A and 75B are connected in series. A freewheeling diode 75AD is connected in parallel to the second switching element 75A. A freewheeling diode 75BD is connected in parallel to the second switching element 75B. A second terminal T2 is located between the second switching element 75A and the second switching element 75B.

[0064] The first capacitive load 73 comprises the vibrating section 21V and the driving means 23a (see Figure 5). The first capacitive load 73 is positioned between the first terminal T1 and the second terminal T2. No reactor is positioned between the first terminal T1 and the second terminal T2. Only wiring is provided between the first terminal T1 and the first capacitive load 73. Similarly, only wiring is provided between the second terminal T2 and the first capacitive load 73. The resonant frequency of the first capacitive load 73 is, for example, 20 kHz or higher.

[0065] The full-bridge inverter circuit 53 has a third leg 81, a fourth leg 82, and a second capacitive load 83. The third leg 81 is connected in series with the second DC power supply unit 63. The third leg 81 has a pair of third switching elements 84 (third switching elements 84A and 84B). The third switching elements 84A and 84B are connected in series. A freewheeling diode 84AD is connected in parallel to the third switching element 84A. A freewheeling diode 84BD is connected in parallel to the third switching element 84B. A third terminal T3 is located between the third switching element 84A and the third switching element 84B.

[0066] The fourth leg 82 is connected in series with the second DC power supply unit 63 and in parallel with the third leg 81. The fourth leg 82 has a pair of fourth switching elements 85 (fourth switching elements 85A and 85B). The fourth switching elements 85A and 85B are connected in series. A freewheeling diode 85AD is connected in parallel to the fourth switching element 85A. A freewheeling diode 85BD is connected in parallel to the fourth switching element 85B. A fourth terminal T4 is located between the fourth switching element 85A and the fourth switching element 85B.

[0067] The second capacitive load 83 comprises the vibrating section 21V and the driving means 23b (see Figure 5). The second capacitive load 83 is positioned between the third terminal T3 and the fourth terminal T4. No reactor is positioned between the third terminal T3 and the fourth terminal T4. Only wiring is provided between the third terminal T3 and the second capacitive load 83. Similarly, only wiring is provided between the fourth terminal T4 and the second capacitive load 83. The resonant frequency of the second capacitive load 83 is, for example, 20 kHz or higher.

[0068] The second terminal T2 and the fourth terminal T4 are electrically short-circuited to each other. As a result, the potential of one terminal of the first capacitive load 73 (on the side of the second terminal T2) and the potential of one terminal of the second capacitive load 83 (on the side of the fourth terminal T4) are approximately equal. This potential is the reference potential in the full-bridge inverter circuits 52 and 53.

[0069] (Operation of the drive circuit device) The operation of the drive circuit device 50 having the above configuration will be explained with reference to Figures 12(a) to 13(c). In the graphs of Figures 12(a) to 13(c), the horizontal axis represents time. Figure 12(a) is a graph showing the time change of the switching signal applied to the first switching element 74A (hereinafter referred to as signal A for the sake of explanation). The vertical axis of the graph in Figure 12(a) represents the on / off state of signal A. Figure 12(b) is a graph showing the time change of the switching signal applied to the first switching element 74B (hereinafter referred to as signal B for the sake of explanation). The vertical axis of the graph in Figure 12(b) represents the on / off state of signal B. Figure 12(c) is a graph showing the time change of the switching signal applied to the second switching element 75A (hereinafter referred to as signal C for the sake of explanation). The vertical axis of the graph in Figure 12(c) represents the on / off state of signal C. Figure 12(d) is a graph showing the time variation of the switching signal (hereinafter referred to as signal D for convenience of explanation) applied to the second switching element 75B. The vertical axis of the graph in Figure 12(d) represents the on / off state of signal D.

[0070] Figure 13(a) is a graph showing the time variation of the voltage applied between the drain and source of the first switching element 74B (hereinafter referred to as VoL for convenience of explanation). The vertical axis of the graph in Figure 13(a) represents VoL. Figure 13(b) is a graph showing the time variation of the voltage applied between the drain and source of the second switching element 75B (hereinafter referred to as VoR for convenience of explanation). The vertical axis of the graph in Figure 13(b) represents VoR. Figure 13(c) is a graph showing the time variation of the voltage applied to the first capacitive load 73 (hereinafter referred to as Vp1 for convenience of explanation). The vertical axis of the graph in Figure 13(c) represents Vp1.

[0071] The following describes the operation of the full-bridge inverter circuit 52, one of the two full-bridge inverter circuits 52 and 53. For convenience of explanation, the power supply voltage of the first DC power supply unit 62 is denoted as Vdc. As mentioned above, the voltage applied to the first switching element 74B is denoted as VoL. The voltage applied to the second switching element 75B is denoted as VoR. The voltage applied to the first capacitive load 73 is denoted as Vp1. Vp1 = VoL - VoR.

[0072] The switching signal generation unit 41 (see Figure 5) generates and outputs a signal A (see Figure 12(a)) having a predetermined switching frequency (fs). The switching frequency is, for example, 20 kHz or higher. The duty cycle of signal A is, for example, 50%. Signal A is applied to the gate of the first switching element 74A. The switching signal generation unit 41 also generates and outputs a signal B (see Figure 12(b)) having approximately the same frequency as signal A. The duty cycle of signal B is, for example, 50%. Signal B is applied to the gate of the first switching element 74B. The phase of signal B is approximately 180° different from the phase of signal A. When one of signals A and B is on, the other is off.

[0073] The switching signal generation unit 41 also generates and outputs signal C (see Figure 12(c)). The frequency of signal C is approximately equal to the frequency of signal A. The phase of signal C differs from the phase of signal A by a predetermined phase. The phase difference between signal A and signal C is called, for example, Φ (not shown in Figures 12(a) and 12(c); see Figures 13(a) and 13(b)). The duty cycle of signal C is, for example, 50%. Signal C is applied to the gate of the second switching element 75A. The switching signal generation unit 41 also generates and outputs signal D (see Figure 12(d)) with approximately the same frequency as signal C. The duty cycle of signal D is, for example, 50%. Signal D is applied to the gate of the second switching element 75B. The phase of signal D differs from the phase of signal C by approximately 180°. When one of signals C and D is on, the other is off.

[0074] When signal A is ON and signal B is OFF, the first switching element 74A is ON and the first switching element 74B is OFF. At this time, almost all of the power supply voltage of the first DC power supply unit 62 is applied to the first switching element 74B. Therefore, Vol is approximately equal to Vdc (see Figure 13(a)). Also, when signal A is OFF and signal B is ON, the first switching element 74A is OFF and the first switching element 74B is ON. At this time, Vol is approximately equal to zero (see Figure 13(a)). Thus, the waveform of Vol is a square wave with a duty cycle of 50%.

[0075] Similarly, when signal C is on and signal D is off, VoR is approximately equal to Vdc (see Figure 13(b)). When signal C is off and signal D is on, VoR is approximately equal to zero (see Figure 13(b)). Thus, the waveform of VoR is a square wave with a duty cycle of 50%. The phase of VoR differs from the phase of VoL by Φ (see Figures 13(a) and 13(b)).

[0076] As a result, Vp1 (=VoL-VoR) oscillates between -Vdc and +Vdc (see Figure 13(c)). The frequency of the oscillation is approximately equal to fs. This allows the first capacitive load 73 to be driven at approximately the same frequency as fs.

[0077] The switching signal generation unit 41 can adjust the effective value of Vp1 by changing the phase difference (i.e., Φ) between VoL and VoR. The closer Φ is to 0°, the smaller the effective value of Vp1. The closer Φ is to 180°, the larger the effective value of Vp1. In this way, the magnitude of the vibration of the first capacitive load 73 can be adjusted in the full-bridge inverter circuit 52 without a reactor. Furthermore, even if the switching frequency is changed, large fluctuations in the magnitude and phase of the vibration of the first capacitive load 73 can be suppressed. Note that Φ should be appropriately set before or during operation of the drive circuit device 50, taking into consideration its relationship with the magnitude of the vibration of the second capacitive load 83.

[0078] A detailed explanation of the operation of the full-bridge inverter circuit 53 is omitted. The switching signal generation unit 41 (see Figure 5) generates a switching signal such that the phase of the AC voltage applied to the second capacitive load 83 is shifted by 90° relative to the phase of the AC voltage applied to the first capacitive load 73. This drives the second capacitive load 83. The difference between the phase of the switching signals applied to the third switching elements 84A and 84B and the phase of the switching signals applied to the fourth switching elements 85A and 85B must be appropriately set before or during the operation of the drive circuit device 50.

[0079] As described above, the first capacitive load 73 and the second capacitive load 83 are connected to the full-bridge inverter circuits 52 and 53, respectively. In the full-bridge inverter circuit 52, the discharge path for the first capacitive load 73 can be secured by maintaining the state in which either one of the pair of first switching elements 74 and either one of the pair of second switching elements 75 is ON. Similarly, the discharge path for the second capacitive load 83 can also be secured in the full-bridge inverter circuit 53. In this configuration, the effective value of the voltage applied to the first capacitive load can be adjusted by adjusting the phase difference between the switching signal to the first leg 71 and the switching signal to the second leg 72. Similarly, the effective value of the voltage applied to the second capacitive load can also be adjusted.

[0080] Furthermore, the second terminal T2 and the fourth terminal T4 are electrically short-circuited. This ensures that one terminal of the first capacitive load 73 and one terminal of the second capacitive load 83 are at the same potential. In addition, the capacitor 66, which functions as the first DC power supply, and the capacitor 69, which functions as the second DC power supply, are electrically isolated from each other. This prevents short circuits between capacitors 66 and 69 regardless of the operating state of each switching element. Therefore, failure of the drive circuit device 50 due to such short circuits can be prevented. As a result, unintended fluctuations in the voltage applied to each capacitive load can be suppressed in the drive circuit device 50.

[0081] Furthermore, in the conventional drive circuit device 100, there is a resonant frequency of impedance formed by the reactor and capacitive load. This resonant frequency is very low compared to the drive frequency. Therefore, if a low-frequency switching signal is mistakenly applied to the drive circuit device 100, there is a risk that the drive circuit device 100 will fail due to a large current flowing through it. In the drive circuit device 50 of this embodiment, since there is no reactor, this resonant frequency does not exist. Therefore, the risk of the large current flowing through the drive circuit device 50 as described above can be avoided.

[0082] Furthermore, even if the switching frequency (drive frequency) is adjusted near the resonant frequency of the first capacitive load 73, abrupt changes in the amplitude and phase of vibration of the transport unit 21 due to the piezoelectric element 16a can be suppressed. Similarly, even if the drive frequency is adjusted near the resonant frequency of the second capacitive load 83, abrupt changes in the amplitude and phase of vibration of the transport unit 21 due to the piezoelectric element 16b can be suppressed. Therefore, the workpiece W can be transported stably.

[0083] Next, modified examples of the above embodiments will be described. However, components having the same configuration as the above embodiments will be denoted by the same reference numerals and their descriptions will be omitted as appropriate.

[0084] (1) In the above embodiment, the drive circuit device 50 is applied to a linear feeder 3 driven by a switching signal of a high frequency of 20 kHz or higher. However, it is not limited to this. The drive circuit device 50 may also be applied to a vibration transport device driven by a switching signal of a lower frequency.

[0085] (2) In the embodiments described above, the full-bridge inverter circuits 52 and 53 were configured such that Vp1 oscillates between two voltage levels (-Vdc and +Vdc). Such full-bridge inverter circuits are generally called "two-level full-bridge inverter circuits." However, they are not limited to this. The full-bridge inverter circuits 52 and 53 may also be so-called "three-level or more full-bridge inverter circuits" having three or more voltage levels.

[0086] (3) In the embodiments described above, the duty cycle of the switching signal applied to the drive circuit device 50 was assumed to be 50%. However, it is not limited to this. The duty cycle may be less than 50%, for example.

[0087] (4) In the embodiments described above, the full-bridge inverter circuits 52 and 53 were not provided with reactors. However, this is not limited to this. For example, reactors having a small inductance component such that the frequency dependence of Vp1 described above does not become a problem may be provided in the full-bridge inverter circuits 52 and / or 53.

[0088] (5) In the embodiments described above, the drive circuit device 50 is used to drive two drive means 23 (drive means 23a, 23b). However, it is not limited to this. A vibration conveying device such as a linear feeder 3 may have, for example, three or more drive means (not shown) having piezoelectric elements. The drive circuit device 50 may be configured to drive three or more drive means.

[0089] (6) In the embodiments described above, an isolated flyback converter was given as an example of the power supply unit 51. However, it is not limited to this. The power supply unit 51 may have other configurations. Alternatively, the power supply unit 51 may have two DC power supplies that are electrically isolated from each other. [Explanation of Symbols]

[0090] 3. Linear feeder (vibration conveying device) 16a Piezoelectric element (first piezoelectric element) 16b Piezoelectric element (second piezoelectric element) 21 Conveying section 50 Drive circuit device 66 Capacitor (First DC Power Supply) 69 Capacitor (Second DC Power Supply) 71 Leg 1 72 Leg 2 73 1st capacitive load 74 First switching element 74A First switching element 74B First switching element 75. Second switching is possible. 75A Second switching element 75B Second switching element 81 Third Leg 82 Leg 4 83 Second capacitive load 84 Third switching element 84A Third switching element 84B Third switching element 85. Fourth switching element 85A Fourth switching element 85B Fourth switching element T1 First terminal T2 Second terminal T3 Third terminal T4 4th terminal W Work (transported goods)

Claims

1. A drive circuit device for driving a first capacitive load having a first capacitive component and a second capacitive load having a second capacitive component, The first DC power supply is the power source for the first capacitive load, A first leg having a pair of first switching elements connected in series with the first DC power supply, A second leg having a pair of second switching elements connected in parallel with the pair of first switching elements, A second DC power supply, which is the power source for the second capacitive load, is separate from the first DC power supply. A third leg having a pair of third switching elements connected in series with the second DC power supply, A fourth leg having a pair of fourth switching elements connected in parallel with the pair of third switching elements, The first capacitive load is positioned between a first terminal positioned between the pair of first switching elements in the first leg and a second terminal positioned between the pair of second switching elements in the second leg. The second capacitive load is positioned between a third terminal positioned between the pair of third switching elements in the third leg and a fourth terminal positioned between the pair of fourth switching elements in the fourth leg. The second terminal and the fourth terminal are electrically short-circuited. A drive circuit device characterized in that the first DC power supply and the second DC power supply are electrically isolated from each other.

2. The drive circuit device according to claim 1, A vibrating conveying device comprising: a conveying unit configured to convey an object by being driven by the aforementioned drive circuit device, The first capacitive load includes a first piezoelectric element configured to vibrate the transport section, The vibration conveying device is characterized in that the second capacitive load includes a second piezoelectric element configured to vibrate the conveying section.

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