Electrodischarge machining apparatus

Abstract

An electrodischarge machining apparatus (100) comprises: a machining tank (1) that accommodates electrodes and a workpiece and stores a machining liquid (7); and a power supply device (3) that supplies a current between the electrodes. The power supply device (3) has: a power supply housing (31) that is disposed on the outer surface (1g) of the machining tank (1); a plurality of substrates (33) that are accommodated in the power supply housing (31) and have heating elements (33a); a water-cooling pipe (36) that is accommodated in the power supply housing (31) and through which a cooling medium flows; and heat dissipation fins (37) that are accommodated in the power supply housing (31) and are in contact with the water-cooling pipe (36) and with the heating elements (33a) of the plurality of substrates (33). The power supply housing (31) has a substrate plane (31a) facing the outer surface (1g) of the machining tank (1). The plurality of substrates (33) are disposed in a state of being displaced from each other in a direction perpendicular to the substrate plane (31a). The heat dissipation fins (37) have different structures or different dimensions depending on the amount of heat generated by the heating elements (33a) of each of the substrates (33).

Description

Electric discharge machining apparatus

[0001] The present disclosure relates to an electric discharge machining apparatus that generates an electric discharge between electrodes and a workpiece formed in a machining tank and machines the workpiece by the arc heat of the electric discharge.

[0002] Conventionally, an electric discharge machining apparatus that generates an electric discharge between electrodes and a workpiece formed in a machining tank and machines the workpiece by the arc heat of the electric discharge is known. The electric discharge machining apparatus includes a power supply device that supplies current and voltage between the electrodes.

[0003] Generally, machining characteristics such as the surface roughness of the machined surface of the workpiece and the dimensions of the workpiece after machining are affected by the current supplied between the electrodes from the power supply device during electric discharge. Therefore, when the current changes, the machining characteristics also change.

[0004] Since the current supplied between the electrodes has a very short pulse shape, it is affected by parasitic impedances such as parasitic inductance and stray capacitance derived from the connection conductor between the electrodes and the power supply device. In particular, if there is a distance between the electrodes and the power supply device, the connection conductor becomes longer accordingly, and the current decays due to the parasitic inductance, which may make it difficult to obtain desired machining characteristics. Further, when the connection conductor is a cable, even if the length, thickness, number, etc. of the cable are uniquely designed, a misalignment of the cable arrangement occurs due to assembly errors that occur for each electric discharge machining apparatus. As a result, a difference occurs in the parasitic inductance, and variations occur in the machining quality of the workpiece.

[0005] Therefore, in order to shorten the distance between the electrodes and the power supply device, it is preferable to bring the power supply device as close as possible to the electrodes. For example, Patent Document 1 discloses a technique of miniaturizing the entire power supply device by arranging a plurality of substrates on the same plane (in a row in a direction parallel to one plane of the power supply device) inside the power supply device and directly attaching the power supply device to the outer surface of the machining tank. Further, Patent Document 1 discloses a technique of providing a water cooling pipe through which a cooling medium flows inside the power supply device along the direction in which a plurality of substrates are arranged in a row in order to cool electronic components (hereinafter referred to as heating elements) on each substrate.

[0006] U.S. Patent No. 9,682,436

[0007] However, in the technology disclosed in Patent Document 1, because multiple substrates are arranged on the same plane, the water cooling pipe becomes longer, and uneven cooling efficiency to the heat-generating elements on each substrate tends to occur. As a result, the temperature of the heat-generating elements on each substrate tends to become non-uniform, and differences in the pulse shape of the output current waveform occur for each substrate due to the temperature characteristics of the heat-generating elements.

[0008] This disclosure has been made in view of the above, and aims to provide an electrical discharge machining apparatus that is less likely to cause differences in the pulse shape of the output current waveform for each substrate due to the temperature characteristics of the heating element.

[0009] To solve the above-mentioned problems and achieve the objective, the electrical discharge machining apparatus according to this disclosure is an electrical discharge machining apparatus that generates a discharge between electrodes formed between an electrode and a workpiece, and processes the workpiece by the arc heat of the discharge, and comprises a machining tank and a power supply unit. The machining tank houses the electrode and the workpiece and stores machining fluid. The power supply unit supplies current between the electrodes. The power supply unit comprises a power supply housing disposed on the outer surface of the machining tank and a plurality of substrates housed within the power supply housing and having heating elements. The power supply unit also comprises a water cooling pipe housed within the power supply housing through which a cooling medium flows, and heat dissipation fins housed within the power supply housing that contact the heating elements of each of the plurality of substrates and the water cooling pipe. The power supply housing has a substrate plane facing the outer surface of the machining tank. The plurality of substrates are arranged offset from each other in the vertical direction of the substrate plane. The heat dissipation fins have different structures or different dimensions depending on the amount of heat generated by the heating elements of each substrate.

[0010] The electrical discharge machining apparatus described herein has the effect of minimizing differences in the pulse shape of the output current waveform for each substrate due to the temperature characteristics of the heating element.

[0011] An explanatory diagram showing the configuration of the electrical discharge machining apparatus according to Embodiment 1. A plan view showing the configuration of the machining tank and power supply unit of the electrical discharge machining apparatus according to Embodiment 1. A plan view showing the configuration of the machining tank and power supply unit of the electrical discharge machining apparatus according to Embodiment 2. A plan view showing the configuration of the machining tank and power supply unit of the electrical discharge machining apparatus according to Embodiment 3. A side view showing the configuration of the power supply unit of the electrical discharge machining apparatus according to Embodiment 3.

[0012] The electrical discharge machining apparatus according to this embodiment will be described in detail below with reference to the drawings.

[0013] Embodiment 1. Figure 1 is an explanatory diagram showing the configuration of an electrical discharge machining apparatus 100 according to Embodiment 1. Figure 2 is a plan view showing the configuration of the machining tank 1 and power supply unit 3 of the electrical discharge machining apparatus 100 according to Embodiment 1. As shown in Figure 1, the electrical discharge machining apparatus 100 comprises a machining tank 1, a connecting conductor 2, and a power supply unit 3. The electrical discharge machining apparatus 100 is a device that applies a voltage pulse controlled by the power supply unit 3 to the gap 6 formed between the electrode 4 and the workpiece 5, generates a discharge in the gap 6, and processes the workpiece 5 by melting it with the arc heat of the discharge. In this embodiment, the electrical discharge machining apparatus 100 is a die-sinking electrical discharge machining apparatus, but it may also be a wire electrical discharge machining apparatus where the electrode 4 is a wire, or a small-hole electrical discharge machining apparatus where the electrode 4 is a rod-shaped electrode or a hollow rod-shaped electrode.

[0014] Hereafter, when describing the direction of each component of the electrical discharge machining apparatus 100, we will follow the left-handed XYZ coordinate system shown in Figure 2. The X, Y, and Z axes are three axes perpendicular to each other. Of each axis, the direction of the arrow is considered positive, and the direction opposite to the arrow is considered negative. The direction along the X axis (X-axis direction) is the direction in which the machining tank 1 and the power supply unit 3 face each other, and is included in the horizontal direction. The direction along the Y axis (Y-axis direction) is the direction perpendicular to the X-axis direction, and is included in the horizontal direction. The direction along the Z axis (Z-axis direction) is the direction perpendicular to the X-axis direction and Y-axis direction, and coincides with the up-down direction (vertical direction). Hereafter, the positive direction of the Z axis will be considered upward, and the negative direction of the Z axis will be considered downward.

[0015] As shown in Figure 1, the processing tank 1 serves to house the electrode 4 and the workpiece 5, as well as to store the processing fluid 7. The electrode 4 and the workpiece 5 are immersed in the processing fluid 7 in the processing tank 1. The processing fluid 7 contributes to cooling the electrode 4 and the workpiece 5, preventing fires, and removing processing chips generated by electrical discharge machining. Examples of materials for the workpiece 5 include tungsten, molybdenum, silicon carbide, single-crystal silicon, single-crystal silicon carbide, gallium nitride, and polycrystalline silicon. Silicon carbide is also called silicon carbide.

[0016] The machining tank 1 is box-shaped with an opening at the top. As shown in Figures 1 and 2, the machining tank 1 has a bottom wall 1a, a front wall 1b, a rear wall 1c, and a pair of side walls 1d and 1e. As shown in Figure 2, the bottom wall 1a is a rectangular, horizontal wall. The front wall 1b, rear wall 1c, and side walls 1d and 1e rise from the periphery of the bottom wall 1a. The front wall 1b is a vertical wall that the operator faces when performing electrical discharge machining. The rear wall 1c is a vertical wall located on the opposite side of the operator, with the front wall 1b in between. The side wall 1d is a vertical wall that connects one end of the front wall 1b and the rear wall 1c in the Y-axis direction. The side wall 1e is a vertical wall that connects the other end of the front wall 1b and the rear wall 1c in the Y-axis direction. Hereinafter, the surface of each wall of the processing tank 1 that faces the inside of the processing tank 1 will be referred to as the inner surface 1f, and the surface of each wall of the processing tank 1 that faces the outside of the processing tank 1 will be referred to as the outer surface 1g.

[0017] As shown in Figure 1, the connecting conductor 2 is a conductor that electrically connects the electrode 4 and the workpiece 5 to the power supply unit 3. That is, the connecting conductor 2 electrically connects the space between the electrodes 6 to the power supply unit 3. The connecting conductor 2 is, for example, a cable or a copper plate. The connecting conductor 2 makes it possible to wire from each power supply board 34 to the space between the electrodes 6, as described later, and this wiring inevitably generates parasitic impedance 8. As mentioned above, this parasitic impedance 8 often does not match the design value and becomes a factor that hinders high-precision machining by the electrical discharge machining apparatus 100.

[0018] The power supply unit 3 is a device that supplies current and voltage to the space between the electrodes 6. The power supply unit 3 is electrically connected to the electrodes 4 and the workpiece 5 via connecting conductors 2. The power supply unit 3 includes a power supply housing 31, a stabilized power supply 32, and a plurality of circuit boards 33. As shown in Figure 2, the power supply unit 3 also includes a water cooling pipe 36 and a plurality of heat dissipation fins 37.

[0019] The power supply housing 31 is positioned on the outer surface 1g of the rear wall 1c of the machining tank 1, that is, on the back of the machining tank 1. The power supply housing 31 may also be positioned on the outer surface 1g of walls other than the rear wall 1c and the bottom wall 1a. The power supply housing 31 serves to house a plurality of circuit boards 33, a water cooling pipe 36, and a plurality of heat dissipation fins 37. The shape of the power supply housing 31 is box-like. The circuit boards 33, heat dissipation fins 37, and the retaining member 38 described later, housed inside the power supply housing 31, are not actually visible, but in each figure from Figure 2 onward, each component is shown with a solid line. The power supply housing 31 has a circuit board surface 31a facing the outer surface 1g of the rear wall 1c of the machining tank 1. The circuit board surface 31a is a mounting surface to which the machine is attached to the machining tank 1. The circuit board surface 31a is a plane that extends in the Y-axis direction and the Z-axis direction. The circuit board surface 31a is parallel to the outer surface 1g of the rear wall 1c of the machining tank 1 and faces the outer surface 1g of the rear wall 1c of the machining tank 1 with a gap between them.

[0020] As shown in Figure 1, the stabilized power supply 32 is a power source for supplying the current (DC current) used for electrical discharge machining to the space between the electrodes 6. The stabilized power supply 32 may be installed either inside or outside the power supply housing 31. In this embodiment, in order to make the power supply housing 31 as small as possible, an example is shown in which the stabilized power supply 32 is installed outside the power supply housing 31.

[0021] As shown in Figure 2, each of the multiple substrates 33 is housed in a power supply housing 31 and has multiple heating elements 33a, which are electronic components. The substrates 33 are printed circuit boards. The multiple substrates 33 are arranged offset from each other in the direction perpendicular to the substrate plane 31a. The direction perpendicular to the substrate plane 31a coincides with the direction of the X-axis. Hereinafter, the X-axis direction may also be referred to as the direction perpendicular to the substrate plane 31a. Each of the multiple substrates 33 has multiple output terminals 33b. The distance from the output terminals 33b to the processing bath 1 differs for each substrate 33. A portion of each of the multiple substrates 33 overlaps with another substrate 33 when viewed along the direction perpendicular to the substrate plane 31a. Preferably, each heating element 33a of the multiple substrates 33 is a wide-bandgap semiconductor. The substrate 33 is either a power supply substrate 34 or an oscillator substrate 35. The power supply substrate 34 is a substrate electrically connected to the poles 6. The oscillator substrate 35 is a substrate that controls the current supplied from the stabilized power supply 32 (see Figure 1) by switching.

[0022] In the illustrated example, the power supply unit 3 has a plurality of power supply boards 34 and one oscillator board 35. In this embodiment, an example is shown in which there are three power supply boards 34 and one oscillator board 35, but this is not intended to limit the number of boards. Hereafter, when distinguishing between the three power supply boards 34, they will be referred to as power supply board 34A, power supply board 34B, and power supply board 34C. The three power supply boards 34A to 34C are arranged in the Y-axis direction, partially overlapping in the Y-axis direction. Each power supply board 34A to 34C is electrically connected between poles 6 (see Figure 1) via a connecting conductor 2. The oscillator board 35 is positioned away from power supply board 34B, which is located in the center in the Y-axis direction, in the X-axis direction.

[0023] The entire power supply board 34B and the entire oscillator board 35 overlap each other when viewed along the vertical direction of the board plane 31a. A portion of the power supply board 34A is positioned between the power supply board 34B and the oscillator board 35 in the X-axis direction, and is spaced apart from both the power supply board 34B and the oscillator board 35. A portion of the power supply board 34A, a portion of the power supply board 34B, and a portion of the oscillator board 35 overlap each other when viewed along the vertical direction of the board plane 31a. A portion of the power supply board 34C is positioned between the power supply board 34B and the oscillator board 35 in the X-axis direction, and is spaced apart from both the power supply board 34B and the oscillator board 35. A portion of the power supply board 34C, a portion of the power supply board 34B, and a portion of the oscillator board 35 overlap each other when viewed along the vertical direction of the board plane 31a.

[0024] Each of the multiple substrates 33 is connected to the substrate plane 31a or to another substrate 33 via a retaining member 38 extending in the X-axis direction. The retaining member 38 is a spacer or the like. An insulating spacer may be used as the spacer. Specifically, each power supply substrate 34A to 34C is connected to the substrate plane 31a via a plurality of retaining members 38. The retaining members 38 connecting each power supply substrate 34A to 34C to the substrate plane 31a penetrate the substrate plane 31a and reach the processing bath 1, and are in contact with the outer surface 1g of the processing bath 1. Note that in Figure 2, the retaining members 38 connecting each power supply substrate 34A to 34C to the substrate plane 31a do not reach each power supply substrate 34A to 34C, but in reality they do reach each power supply substrate 34A to 34C. Furthermore, when viewed along the vertical direction of the substrate plane 31a, parts of the power supply board 34A and parts of the power supply board 34B that overlap are connected to each other via a holding member 38, with a gap between them. Also, when viewed along the vertical direction of the substrate plane 31a, parts of the power supply board 34A and parts of the oscillator board 35 that overlap are connected to each other via a holding member 38, with a gap between them.

[0025] Furthermore, when viewed along the vertical direction of the substrate plane 31a, parts of the power supply board 34C and parts of the power supply board 34B that overlap are connected to each other via a holding member 38, with a gap between them. Also, when viewed along the vertical direction of the substrate plane 31a, parts of the power supply board 34C and parts of the oscillator board 35 that overlap are connected to each other via a holding member 38, with a gap between them. The multiple substrates 33 are arranged offset from each other in the vertical direction of the substrate plane 31a via the multiple holding members 38, and are arranged to overlap at least partially when viewed along the vertical direction of the substrate plane 31a.

[0026] Each power supply board 34A to 34C has a plurality of heating elements 33a. The plurality of heating elements 33a are provided on the surface of each power supply board 34A to 34C facing the processing tank 1. It is preferable that the plurality of heating elements 33a of each power supply board 34A to 34C are arranged at equal intervals in the Y-axis direction, which is the direction in which the cooling medium flows (see arrow D in Figure 2), as in this embodiment, but they may also be arranged at uneven intervals in the Y-axis direction. The heating elements 33a of each power supply board 34A to 34C are connected to the water cooling pipe 36 via heat dissipation fins 37. Although not shown in the figure, the oscillator board 35 also has heating elements. The heating elements of the oscillator board 35 may also be connected to the water cooling pipe 36 via heat dissipation fins 37. However, since the amount of heat generated by the heating elements of the oscillator board 35 is less than that of the heating elements 33a of the power supply board 34, it is not always necessary to connect the heating elements of the oscillator board 35 to the water cooling pipe 36 via heat dissipation fins 37.

[0027] The water cooling pipe 36 is housed within the power supply housing 31. A cooling medium flows through the water cooling pipe 36. In this embodiment, the processing fluid 7 in the processing tank 1 is used as the cooling medium, but a cooling liquid specifically for cooling may be used instead of the processing fluid 7. The water cooling pipe 36 extends in a straight line along the Y-axis. The inner and outer diameters of the water cooling pipe 36 are constant along its entire length in the Y-axis direction. Arrow D in Figure 2 indicates the direction in which the cooling medium flows within the water cooling pipe 36. The direction of flow of the cooling medium coincides with the Y-axis direction. The water cooling pipe 36 is positioned between each power supply board 34A to 34C and the processing tank 1 in the X-axis direction. The water cooling pipe 36 is positioned away from each power supply board 34A to 34C in the positive direction of the X-axis direction of each power supply board 34A to 34C.

[0028] The heat dissipation fins 37 are housed within the power supply housing 31 and contact each of the heat-generating elements 33a of the multiple substrates 33 and the water cooling pipes 36. The heat dissipation fins 37 dissipate the heat from the heat-generating elements 33a to the cooling medium in the water cooling pipes 36. In this embodiment, one heat dissipation fin 37 is provided for each power supply substrate 34A to 34C, but one fin may be provided to contact all of the multiple power supply substrates 34A to 34C together. Each heat dissipation fin 37 is in contact with the multiple heat-generating elements 33a and the outer surface of the water cooling pipes 36. Although not shown in the figures, each heat dissipation fin 37 is arranged around the entire circumference of the water cooling pipes 36. Each heat dissipation fin 37 is positioned between each power supply substrate 34A to 34C and the processing tank 1 in the X-axis direction.

[0029] In order to make the temperature of the heating elements 33a of each substrate 33 uniform, it is preferable to place the heating elements 33a with high heating temperatures near the water cooling pipes 36, and the heating elements 33a with low heating temperatures far from the water cooling pipes 36. In this embodiment, the heating elements 33a of the power supply board 34B, the heating elements 33a of the power supply board 34A, and the heating elements 33a of the power supply board 34C have the highest heating temperatures and are closest to the water cooling pipes 36, in that order. Also, in this embodiment, the heating elements 33a of the power supply board 34B, the heating elements 33a of the power supply board 34A, and the heating elements 33a of the power supply board 34C are closest to the substrate surface 31a and the processing tank 1, in that order.

[0030] The multiple heat dissipation fins 37 have different dimensions from each other, according to the amount of heat generated by the heat-generating element 33a on each substrate 33. That is, the width dimension of each of the multiple heat dissipation fins 37 in the X-axis direction is different from each other, according to the amount of heat generated by the heat-generating element 33a on each substrate 33. Specifically, in this embodiment, the width dimension in the X-axis direction decreases in the following order: heat dissipation fins 37 that contact the heat-generating element 33a on the power supply substrate 34B, heat dissipation fins 37 that contact the heat-generating element 33a on the power supply substrate 34A, and heat dissipation fins 37 that contact the heat-generating element 33a on the power supply substrate 34C.

[0031] The heat generated by the heat-generating elements 33a of each power supply board 34A to 34C is transferred to the heat dissipation fins 37 that are in contact with each power supply board 34A to 34C. As the cooling medium flows through the water cooling pipe 36, heat exchange occurs between the heat dissipation fins 37 and the cooling medium. In other words, the cooling medium absorbs the heat transferred to the heat dissipation fins 37. As a result, the heat-generating elements 33a of each power supply board 34A to 34C are cooled.

[0032] Next, the effects of the electrical discharge machining apparatus 100 according to this embodiment will be described.

[0033] In the technology disclosed in Patent Document 1, by arranging multiple substrates on the same plane, the water cooling pipe becomes longer, which tends to cause uneven cooling efficiency to the heat-generating elements of each substrate, and the heat dissipation fins have a uniform structure. As a result, the temperature of the heat-generating elements on each substrate tends to be non-uniform, and differences in the pulse shape of the output current waveform occur for each substrate due to the temperature characteristics of the heat-generating elements. When an electrical discharge machining (EDM) machine is a wire EDM machine, the machining accuracy and machining speed can generally be improved by adjusting the current waveform supplied from the top and bottom of the wire according to the wire wear. However, if there are differences in the pulse shape of the output current waveform for each substrate, adjusting the current waveform becomes difficult. Even in such cases, it is possible to adjust the current waveform by power supply control, but this leads to the problem of a complex circuit configuration.

[0034] In this embodiment, as shown in Figure 2, the multiple substrates 33 are arranged offset from each other in the vertical direction of the substrate plane 31a, so that when viewed along the vertical direction of the substrate plane 31a, parts or all of the multiple substrates 33 can be overlapped. For this reason, compared to the technology disclosed in Patent Document 1, the length of the water cooling pipe 36 in the direction parallel to the substrate plane 31a (Y-axis direction) is shortened, and the cooling efficiency to the heat-generating elements 33a of each substrate 33 is less likely to be uneven. In addition, in this embodiment, because the multiple substrates 33 are arranged offset from each other in the vertical direction of the substrate plane 31a, the distance to the water cooling pipe 36 can be changed for each substrate 33. Then, the dimensions of the heat dissipation fins 37 can be changed according to the amount of heat generated by the heat-generating elements 33a of each substrate 33 (according to the distance between each substrate 33 and the water cooling pipe 36), so that the heat dissipation fins 37 do not have a uniform structure. As a result, the temperature of the heat-generating elements 33a of each substrate 33 tends to be uniform, and differences in the pulse shape of the output current waveform of each substrate 33 are less likely to occur due to the temperature characteristics of the heat-generating elements 33a. Furthermore, since differences in the pulse shape of the output current waveform for each substrate 33 are less likely to occur, adjustment of the current waveform by power supply control becomes unnecessary, thus avoiding increased complexity of the circuit configuration. In addition, since differences in the pulse shape of the output current waveform for each substrate 33 are less likely to occur, processing characteristics are also improved.

[0035] In the technology disclosed in Patent Document 1, since multiple substrates are arranged on the same plane, the distance from the output terminal of each substrate to the processing tank (between electrodes) is uniform, making it difficult to adjust the impedance from each substrate to the processing tank. To adjust the impedance from each substrate to the processing tank, it was necessary to unnecessarily change the length and thickness of the cables connected to each substrate or to assemble an adjustment electrical circuit.

[0036] In this embodiment, since the multiple substrates 33 are arranged offset from each other in the vertical direction of the substrate plane 31a, the distance from the output terminal 33b of each substrate 33 to the processing tank 1 can be arbitrarily changed. That is, the distance between the output terminal 33b and the processing tank 1 is different for each substrate 33. Therefore, the impedance from each substrate 33 to the processing tank 1 can be arbitrarily adjusted by changing the distance from the output terminal 33b of each substrate 33 to the processing tank 1 without unnecessarily changing the length and thickness of the cables or assembling an adjustment electrical circuit. This makes it easy to adjust the output current for each substrate 33.

[0037] In this embodiment, the wiring length can be arbitrarily changed for each substrate 33 by electrically connecting each substrate 33 and the poles 6 of the processing tank 1 via a connecting conductor 2 such as a cable. Therefore, the impedance (wiring impedance) from each substrate 33 to the processing tank 1 can be arbitrarily adjusted. Alternatively, the impedance from each substrate 33 to the processing tank 1 can be arbitrarily adjusted using passive elements with known values ​​instead of cables. Passive elements include resistors, capacitors, inductors, etc.

[0038] In this embodiment, a portion of each of the multiple substrates 33 overlaps with another substrate 33 when viewed along the perpendicular direction of the substrate plane 31a, thereby shortening the length of the water cooling pipe 36 in the direction parallel to the substrate plane 31a (Y-axis direction). This suppresses pressure loss of the cooling medium. Furthermore, by designing the water cooling pipe 36 with low pressure loss, clogging of the water cooling pipe 36 by machining debris can be suppressed even when using machining fluid 7 containing minute machining debris as the cooling medium. This eliminates the need to separately prepare a cooling liquid specifically for cooling, thereby reducing product costs.

[0039] In this embodiment, the water cooling pipe 36 is in a straight line along the Y-axis direction (one direction), which suppresses pressure loss of the cooling medium within the water cooling pipe 36. Therefore, clogging of the water cooling pipe 36 with processing chips can be further suppressed.

[0040] In this embodiment, each of the heating elements 33a of the multiple substrates 33 is a wide-bandgap semiconductor, which suppresses power loss and reduces the amount of heat generated by the heating elements 33a.

[0041] Embodiment 2. Next, an electrical discharge machining apparatus 100A according to Embodiment 2 will be described with reference to Figure 3. Figure 3 is a plan view showing the configuration of the machining tank 1 and power supply unit 3 of the electrical discharge machining apparatus 100A according to Embodiment 2. In this embodiment, the arrangement of the water cooling pipe 36 and heat dissipation fins 37 relative to the substrate 33 and the machining tank 1 differs from that of Embodiment 1 described above. In Embodiment 2, parts that overlap with those of Embodiment 1 described above are denoted by the same reference numerals and their description is omitted.

[0042] The oscillator board 35 is positioned away from the power supply board 34B, which is located in the center in the Y-axis direction, in the positive direction in the X-axis direction. The oscillator board 35 is positioned between the processing tank 1 and the power supply board 34B in the X-axis direction. The oscillator board 35 and each power supply board 34A, 34C are connected to the substrate plane 31a with a gap between them via a holding member 38. The holding member 38 that connects the oscillator board 35 and each power supply board 34A, 34C to the substrate plane 31a penetrates the substrate plane 31a and reaches the processing tank 1, and is in contact with the outer surface 1g of the processing tank 1. Furthermore, a portion of the power supply board 34A and a portion of the oscillator board 35 that overlap when viewed along the vertical direction of the substrate plane 31a are connected to each other with a gap between them via the holding member 38. Furthermore, a portion of the power supply board 34A and a portion of the power supply board 34B that overlap when viewed along the vertical direction of the substrate plane 31a are connected to each other with a gap between them via the holding member 38.

[0043] Also, a part of the power supply substrate 34B and a part of the power supply substrate 34C that overlap when viewed along the vertical direction of the substrate plane 31a are connected to each other with a space therebetween via the holding member 38. Also, a part of the power supply substrate 34C and a part of the oscillation substrate 35 that overlap when viewed along the vertical direction of the substrate plane 31a are connected to each other with a space therebetween via the holding member 38. The plurality of substrates 33 are arranged offset from each other in the vertical direction of the substrate plane 31a via the plurality of holding members 38, and are arranged such that they at least partially overlap when viewed along the vertical direction of the substrate plane 31a.

[0044] The plurality of heating elements 33a are provided on the surface of each of the power supply substrates 34A to 34C facing away from the processing tank 1. It is preferable that the plurality of heating elements 33a of each of the power supply substrates 34A to 34C are arranged at equal intervals in the Y-axis direction, which is the direction in which the cooling medium flows (see the arrow D in FIG. 3) as in the present embodiment, but they may be arranged at unequal intervals in the Y-axis direction. Each heating element 33a of each of the power supply substrates 34A to 34C is connected to the water cooling pipe 36 via the heat dissipation fins 37.

[0045] The water cooling pipe 36 is arranged on the opposite side of the processing tank 1 across each substrate 33 in the X-axis direction. The water cooling pipe 36 is arranged away from each of the power supply substrates 34A to 34C in one direction in the X-axis direction of each of the power supply substrates 34A to 34C.

[0046] In this embodiment, one heat radiating fin 37 is provided to contact each of the plurality of power supply boards 34A to 34C collectively. However, one heat radiating fin 37 may be provided for each of the power supply boards 34A to 34C. The heat radiating fin 37 is in contact with the plurality of heating elements 33a of each of the power supply boards 34A to 34C and the outer peripheral surface of the water cooling pipe 36. Although not shown, the heat radiating fin 37 is arranged over the entire outer circumference of the water cooling pipe 36. The heat radiating fin 37 is arranged on the opposite side of the processing tank 1 across each substrate 33 in the X-axis direction. In this embodiment, in the order of the heating element 33a of the power supply board 34B, the heating element 33a of the power supply board 34C, and the heating element 33a of the power supply board 34A, the heating temperature is high and the distance from the water cooling pipe 36 is close. Also, in this embodiment, in the order of the heating element 33a of the power supply board 34A, the heating element 33a of the power supply board 34C, and the heating element 33a of the power supply board 34B, the distance from the substrate plane 31a and the processing tank 1 is close.

[0047] The heat radiating fin 37 has different dimensions for each part according to the amount of heat generated by the heating element 33a for each substrate 33. That is, the width dimension of the heat radiating fin 37 in the X-axis direction is different according to the amount of heat generated by the heating element 33a for each substrate 33. Specifically, in this embodiment, in the order of the part of the heat radiating fin 37 that contacts the heating element 33a of the power supply board 34B, the part of the heat radiating fin 37 that contacts the heating element 33a of the power supply board 34C, and the part of the heat radiating fin 37 that contacts the heating element 33a of the power supply board 34A, the width dimension in the X-axis direction becomes shorter.

[0048] The heat generated by the heating elements 33a of each of the power supply boards 34A to 34C is transmitted to the heat radiating fin 37 that contacts each of the power supply boards 34A to 34C. When the cooling medium flows in the water cooling pipe 36, heat exchange occurs between the heat radiating fin 37 and the cooling medium. That is, the cooling medium absorbs the heat transmitted to the heat radiating fin 37. Thereby, the heating elements 33a of each of the power supply boards 34A to 34C are cooled.

[0049] Next, the effects of the electric discharge machining apparatus 100A according to this embodiment will be described.

[0050] In this embodiment, as shown in Figure 3, the water cooling pipe 36 and heat dissipation fins 37 are arranged on the opposite side of the processing tank 1 from each substrate 33 in the X-axis direction (perpendicular to the substrate plane 31a), thereby suppressing heat conduction from the heat dissipation fins 37 to the processing tank 1. This makes it possible to suppress the impact on the processing performance of the electrical discharge machining apparatus 100A.

[0051] Embodiment 3. Next, an electrical discharge machining apparatus 100B according to Embodiment 3 will be described with reference to Figures 4 and 5. Figure 4 is a plan view showing the configuration of the machining tank 1 and power supply unit 3 of the electrical discharge machining apparatus 100B according to Embodiment 3. Figure 5 is a side view showing the configuration of the power supply unit 3 of the electrical discharge machining apparatus 100B according to Embodiment 3. This embodiment differs from Embodiments 1 and 2 described above in that the entirety of the multiple substrates 33 are superimposed on each other when viewed along the vertical direction of the substrate plane 31a, and that a portion of the multiple substrates 33 are arranged in contact with a common heat dissipation fin 37. In Embodiment 3, parts that overlap with Embodiments 1 and 2 described above are denoted by the same reference numerals and their description is omitted.

[0052] As shown in Figure 4, in this embodiment, the three power supply boards 34 and the one oscillator board 35 are arranged in a line along the X-axis direction. From the processing bath 1 along the X-axis direction, the power supply boards 34A, 34B, 34C, and oscillator board 35 are arranged in that order. When viewed along the perpendicular direction of the board plane 31a, the entirety of the power supply boards 34A to 34C and the oscillator board 35 overlap each other. The power supply board 34A is connected to the board plane 31a at intervals via a plurality of holding members 38. The holding members 38 that connect the power supply board 34A to the board plane 31a penetrate the board plane 31a and reach the processing bath 1, and are in contact with the outer surface 1g of the processing bath 1. The power supply boards 34A and 34B are connected to each other at intervals via a plurality of holding members 38. The power supply boards 34B and 34C are connected to each other at intervals via a plurality of holding members 38. Furthermore, the power supply board 34C and the oscillator board 35 are connected to each other via a plurality of holding members 38, with a gap between them.

[0053] The multiple heating elements 33a of each power supply board 34A, 34B are provided on the side of each power supply board 34A, 34B facing away from the processing tank 1. As shown in Figure 5, the multiple heating elements 33a of the power supply board 34C are provided on the side of the power supply board 34C facing the processing tank 1. The heating elements 33a of adjacent power supply boards 34B, 34C in the X-axis direction face each other in the Z-axis direction, with the water cooling pipe 36 and heat dissipation fins 37 in between. Note that in Figure 5, the connecting conductor 2 connected to the power supply board 34B is not shown. As shown in Figure 4, it is preferable that the multiple heating elements 33a of each power supply board 34A to 34C are arranged at equal intervals in the Y-axis direction, which is the direction in which the cooling medium flows (see arrow D in Figure 4), as in this embodiment, but they may also be arranged at uneven intervals in the Y-axis direction.

[0054] In this embodiment, there are two water cooling tubes 36. The two water cooling tubes 36 are arranged apart from each other in the X-axis direction. Hereinafter, the two water cooling tubes 36 will be referred to as water cooling tube 36A and water cooling tube 36B. Water cooling tube 36A is located between power supply board 34A and power supply board 34B in the X-axis direction. Water cooling tube 36B is located between power supply board 34B and power supply board 34C in the X-axis direction.

[0055] In this embodiment, there are two heat dissipation fins 37. The two heat dissipation fins 37 are arranged relative to each other in the X-axis direction. Hereinafter, when distinguishing between the two heat dissipation fins 37, they will be referred to as heat dissipation fin 37A and heat dissipation fin 37B. Heat dissipation fin 37A is in contact with a plurality of heat-generating elements 33a on the power supply board 34A and the outer surface of the water cooling pipe 36A. As shown in Figure 5, heat dissipation fin 37A is arranged around the entire circumference of the outer surface of the water cooling pipe 36A. Heat dissipation fin 37A is arranged between the power supply board 34A and the power supply board 34B in the X-axis direction. Heat dissipation fin 37A is in contact with the heat-generating elements 33a on the power supply board 34A, but not with the heat-generating elements 33a on the power supply board 34B. The heat-generating elements 33a on the power supply board 34A are connected to the water cooling pipe 36A via heat dissipation fin 37A.

[0056] The heat dissipation fins 37B are in contact with multiple heat-generating elements 33a on each power supply board 34B, 34C and the outer surface of the water cooling pipe 36B. That is, some of the heat-generating elements 33a on some of the boards 33 (power supply boards 34B, 34C) are positioned in contact with the common heat dissipation fins 37. The heat dissipation fins 37B are positioned around the entire circumference of the water cooling pipe 36B. The heat dissipation fins 37B are positioned between the power supply board 34B and the power supply board 34C in the X-axis direction. The heat-generating elements 33a on each power supply board 34B, 34C are connected to the water cooling pipe 36B via the heat dissipation fins 37B.

[0057] As shown in Figure 4, when multiple substrates 33 are stacked on top of each other when viewed along the vertical direction of the substrate plane 31a, it is preferable to connect the substrate 33 having a heating element 33a with a high heating temperature individually to the water cooling pipe 36 via a heat dissipation fin 37, and connect the multiple substrates 33 having heating elements 33a with a low heating temperature to the water cooling pipe 36 via a common heat dissipation fin 37. This makes it easier to make the temperature of the heating element 33a of each substrate 33 uniform. In this embodiment, the heating temperature of the heating element 33a of the power supply board 34A is higher than that of the heating element 33a of the power supply board 34B and the heating element 33a of the power supply board 34C. Therefore, in this embodiment, the power supply board 34A is connected individually to the water cooling pipe 36A via a heat dissipation fin 37A, and the multiple power supply boards 34B and 34C are connected to the water cooling pipe 36B via a common heat dissipation fin 37B. In this embodiment, the heating element 33a of the power supply board 34A, the heating element 33a of the power supply board 34B, and the heating element 33a of the power supply board 34C are in the order of being closest to the substrate surface 31a and the processing tank 1.

[0058] The multiple heat dissipation fins 37A and 37B have different structures depending on the amount of heat generated by the heat-generating element 33a of each substrate 33. Specifically, in this embodiment, heat dissipation fin 37A contacts only the heat-generating element 33a of the power supply substrate 34A, while heat dissipation fin 37B contacts both the heat-generating element 33a of the power supply substrate 34B and the heat-generating element 33a of the power supply substrate 34C.

[0059] The heat generated by the heat-generating element 33a on the power supply board 34A is transferred to the heat dissipation fins 37A that are in contact with the heat-generating element 33a on the power supply board 34A. When the cooling medium flows through the water cooling pipe 36A, heat exchange takes place between the heat dissipation fins 37A and the cooling medium. That is, the cooling medium absorbs the heat transferred to the heat dissipation fins 37A. As a result, the heat-generating element 33a on the power supply board 34A is cooled. On the other hand, the heat generated on each power supply board 34B and 34C is transferred to the heat dissipation fins 37B that are in contact with the heat-generating elements 33a on each power supply board 34B and 34C. When the cooling medium flows through the water cooling pipe 36B, heat exchange takes place between the heat dissipation fins 37B and the cooling medium. That is, the cooling medium absorbs the heat transferred to the heat dissipation fins 37B. As a result, the heat-generating elements 33a on each power supply board 34B and 34C are cooled.

[0060] Next, the effects of the electrical discharge machining apparatus 100B according to this embodiment will be described.

[0061] In this embodiment, as shown in Figures 4 and 5, the entirety of each of the multiple substrates 33 overlaps with one another when viewed along the vertical direction of the substrate plane 31a, thereby reducing the area occupied by the power supply unit 3 in the processing tank 1.

[0062] In this embodiment, as shown in Figure 4, the entirety of each of the multiple substrates 33 overlaps when viewed along the vertical direction of the substrate plane 31a, thereby shortening the length of the water cooling tube 36 in the Y-axis direction. This suppresses pressure loss of the cooling medium. Furthermore, by designing the water cooling tube 36 with low pressure loss, even when using a processing fluid 7 containing minute processing debris as the cooling medium, clogging of the water cooling tube 36 by processing debris can be suppressed. As a result, there is no need to separately prepare a cooling liquid specifically for cooling, and product costs can be reduced.

[0063] In this embodiment, as shown in Figure 5, the heating elements 33a of some of the multiple substrates 33 (power supply substrates 34B, 34C) face each other in the Z-axis direction with a water cooling pipe 36B and a heat dissipation fin 37B in between. As a result, some of the heating elements 33a of the multiple substrates 33 are positioned in contact with a common heat dissipation fin 37. In other words, the heat dissipation fin 37 can be shared among some of the multiple substrates 33. This reduces the number of parts and allows for miniaturization of the entire power supply unit 3. Furthermore, because the heat dissipation fin 37 is shared, the overall weight of the power supply unit 3 can be reduced, making it easier to install the power supply unit 3 even in the electrical discharge machining apparatus 100B driven by the machining tank 1.

[0064] In this embodiment, as shown in Figure 4, the entirety of each of the multiple substrates 33 overlaps with one another when viewed along the vertical direction of the substrate plane 31a, allowing for a uniform design of the holding member 38. This enables the standardization and optimization of components.

[0065] In this embodiment, as shown in Figure 4, the heating elements 33a of each of the multiple substrates 33 (multiple power supply substrates 34A to 34C) are arranged with equal spacing in the Y-axis direction, which is the direction in which the cooling medium flows. This makes it easier for the temperature of the heating elements 33a on each substrate 33 to become uniform, and makes it less likely for differences to occur in the pulse shape of the output current waveform for each substrate 33 due to the temperature characteristics of the heating elements 33a. Furthermore, because differences in the pulse shape of the output current waveform for each substrate 33 are less likely to occur, adjustment of the current waveform by power supply control becomes unnecessary, and complexity of the circuit configuration can be avoided. In addition, because differences in the pulse shape of the output current waveform for each substrate 33 are less likely to occur, processing characteristics are also improved.

[0066] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0067] 1 Processing tank, 1a bottom wall, 1b front wall, 1c rear wall, 1d, 1e side walls, 1f inner surface, 1g outer surface, 2 connecting conductor, 3 power supply unit, 4 electrodes, 5 workpiece, 6 space between electrodes, 7 processing fluid, 8 parasitic impedance, 31 power supply housing, 31a substrate surface, 32 stabilized power supply, 33 substrate, 33a heating element, 33b output terminal, 34, 34A, 34B, 34C power supply board, 35 oscillation board, 36, 36A, 36B water cooling pipe, 37, 37A, 37B heat dissipation fin, 38 holding member, 100, 100A, 100B electrical discharge machining device, D arrow.

Claims

1. An electrical discharge machining apparatus that processes a workpiece by generating a discharge between electrodes formed between electrodes and a workpiece, and using the arc heat of the discharge, comprising: a processing tank that houses the electrodes and the workpiece and stores a processing fluid; and a power supply device that supplies current between the electrodes, wherein the power supply device comprises: a power supply housing disposed on the outer surface of the processing tank; a plurality of substrates housed in the power supply housing and having heating elements; a water cooling pipe housed in the power supply housing and through which a cooling medium flows; and heat dissipation fins housed in the power supply housing that contact the heating elements of each of the plurality of substrates and the water cooling pipe, wherein the power supply housing has a substrate plane facing the outer surface of the processing tank, the plurality of substrates are arranged offset from each other in the vertical direction of the substrate plane, and the heat dissipation fins have different structures or different dimensions depending on the amount of heat generated by the heating elements of each substrate.

2. The electrical discharge machining apparatus according to claim 1, characterized in that each of the plurality of substrates has an output terminal, and the distance from the output terminal to the processing tank is different for each substrate.

3. The electrical discharge machining apparatus according to claim 1 or 2, characterized in that a part or all of each of the multiple substrates overlaps with another substrate when viewed along the perpendicular direction of the substrate plane.

4. The electrical discharge machining apparatus according to any one of claims 1 to 3, characterized in that each of the plurality of substrates overlaps with one another when viewed along the direction perpendicular to the substrate plane, some of the heating elements of the plurality of substrates are arranged in contact with a common heat dissipation fin, and the heating elements of each of the plurality of substrates are arranged at equal intervals with respect to the direction of flow of the cooling medium.

5. The electrical discharge machining apparatus according to any one of claims 1 to 4, characterized in that each of the heating elements of the plurality of substrates is a wide-bandgap semiconductor.

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