electric motor drive device

Abstract

This invention provides an electric motor drive device. It enables an easy-to-construct, compact, and low-cost electric motor drive device that reduces heat loss from both the smoothing capacitor and the buffer capacitor. The electric motor drive device includes: a smoothing capacitor section having at least one smoothing capacitor disposed between a converter circuit and an inverter circuit within a power conversion circuit that generates drive power for the electric motor; a buffer capacitor that suppresses surge voltages of power elements constituting part of the power conversion circuit; and a support plate for housing the smoothing capacitor section, wherein the electrode terminals of the smoothing capacitor section and the electrode terminals of the buffer capacitor are disposed close to each other across the support plate, the positive terminal of the smoothing capacitor section is electrically connected to the positive terminal of the buffer capacitor, and the negative terminal of the smoothing capacitor section is electrically connected to the negative terminal of the buffer capacitor.

Description

Technical Field

[0001] The present invention relates to an electric motor drive device having a smoothing capacitor section and a buffer capacitor. Background Technology

[0002] In an electric motor drive device that controls the drive of electric motors in machine tools, forging machinery, injection molding machines, industrial machinery, or various robots, AC power supplied from an AC power source is converted into DC power by a converter circuit (rectifier circuit) and output to the DC link. Then, an inverter circuit is used to convert the DC power from the DC link back into AC power, and the AC power is supplied as drive power to the electric motor located on each drive shaft.

[0003] A "DC link" refers to the circuit section that electrically connects the DC output side of the converter circuit to the DC input side of the inverter circuit. It is sometimes also called the "DC link section," "DC loop," "DC bus," or "DC intermediate circuit." The DC link contains a large-capacity smoothing capacitor that suppresses ripple in the DC output of the converter circuit and smooths the voltage input to the inverter circuit. The smoothing capacitor is also called the DC link capacitor.

[0004] Furthermore, power conversion circuits that include inverter circuits and PWM control circuits are, for example, constructed using a bridge circuit. This bridge circuit has a semiconductor switching element called a power element and a diode connected in anti-parallel to the semiconductor switching element. Power conversion is achieved by driving the power element in an on-off manner. In power conversion circuits with power elements, buffer capacitors with good frequency characteristics are provided to suppress surge voltages applied to the power element.

[0005] For example, as disclosed in Japanese Patent Application Publication No. 2018-042384, an inverter structure is known: the inverter structure includes two inverter drive units that convert DC power into AC power for driving two motors, respectively. These inverter drive units are housed in a housing. In this inverter structure, the two inverter drive units include: two switching circuit devices connected to multiple switching elements that convert DC power into AC power and supply it to the respective motors; a capacitor component that includes a smoothing capacitor that smooths the power input to the switching circuit devices and two sets of busbars connected to the smoothing capacitor and supplying power to the two switching circuit devices respectively; and a connecting conductor that supplies power to the two switching circuit devices via the two sets of busbars. The connecting conductor is provided between the two switching circuit devices in the housing.

[0006] For example, as described in Japanese Patent No. 4675379, a drive circuit for an electric motor is known: this drive circuit uses a converter circuit and an inverter circuit to drive the electric motor. The drive circuit is characterized in that it includes: a printed circuit board for a control circuit; and a lead frame molded substrate, which is mounted at predetermined intervals on the component surface of the printed circuit board using protrusions made of molding resin for spacers, and is formed by integrally molding metal plate leads with the molding resin. The converter circuit is constructed on the lead frame molded substrate. The electronic components of the converter circuit and the inverter circuit are used to adjust the height of the electronic components by clamping them with a height adjustment protrusion integral with the molding resin. A buffer capacitor and a shunt resistor of the inverter circuit are also installed. An electrolytic capacitor of the converter circuit is installed on the component side of the printed circuit board. The power terminals of the electronic components are temporarily connected to the lead frame molding substrate. Subsequently, the metal plate leads of the lead frame molding substrate are combined with the printed circuit board, and the control wiring terminals of the electronic components are connected to the printed circuit board.

[0007] For example, as disclosed in Japanese Patent Application Publication No. 2011-091250, a capacitor is known to include: a housing having an opening; a plurality of capacitor elements housed in the housing, each having a pair of electrode surfaces at the opening side and bottom side of the housing; an opening-side busbar disposed on the electrode surfaces of the capacitor elements on the opening side; and a bottom-side busbar disposed on the electrode surfaces of the capacitor elements on the bottom side. The plurality of capacitor elements are connected in parallel using the opening-side busbar and the bottom-side busbar. Each of the opening-side busbar and the bottom-side busbar has a connection terminal for connecting to an external device, disposed in a manner not close to the side surface of the capacitor elements. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] As described above, electric motor drive devices include smoothing capacitors and buffer capacitors. Large-capacity electrolytic capacitors are mostly used as smoothing capacitors. When an overvoltage is applied, the internal electrolyte in an electrolytic capacitor vaporizes, generating gas, which may increase the internal pressure. Therefore, an opening is provided near the terminals to release the gas. Electrolytic capacitors have the following limitation: to prevent electrolyte leakage from the opening, the terminals must be positioned so that they do not face vertically. In particular, electrolytic capacitors with screw terminals have stricter restrictions on installation position because the busbar and screw terminals are fastened using threads. Therefore, the physical distance between the smoothing capacitor and the buffer capacitor may increase depending on the configuration of the power components. If the distance between the smoothing capacitor and the buffer capacitor increases, the inductive component between them increases. Due to this inductive component, a potential difference is generated between the smoothing capacitor and the buffer capacitor, increasing the oscillating current, and thus increasing the heat loss of both the smoothing capacitor and the buffer capacitor. To reduce this heat loss, for example, one could consider selecting capacitors with large heat capacity for the smoothing capacitor and the buffer capacitor, or installing heat sinks such as cooling fans near the smoothing capacitor and the buffer capacitor. However, the larger the heat capacity of the capacitor, the higher its price. In addition, installing heat sinks increases the cost, complexity, and size of the motor drive. Therefore, it is desirable to realize a motor drive that is easy to construct, compact, and low-cost, while reducing the heat loss of the smoothing capacitor and the buffer capacitor.

[0010] Solution for solving the problem

[0011] According to a technical solution of this disclosure, a motor drive device is provided, characterized in that the motor drive device includes: a smoothing capacitor section having at least one smoothing capacitor, the smoothing capacitor smoothing the voltage between a converter circuit and an inverter circuit in a power conversion circuit, the power conversion circuit generating motor drive power based on AC power supplied from an AC power source; and a buffer capacitor for suppressing surge voltage of power elements constituting part of the power conversion circuit; the electrode terminals of the smoothing capacitor section are disposed close to the electrode terminals of the buffer capacitor, the positive terminal of the electrode terminals of the smoothing capacitor section is electrically connected to the positive terminal of the electrode terminals of the buffer capacitor, and the negative terminal of the electrode terminals of the smoothing capacitor section is electrically connected to the negative terminal of the electrode terminals of the buffer capacitor.

[0012] In the above-mentioned motor drive device, the electrode terminals of the smoothing capacitor section may be arranged opposite to the electrode terminals of the buffer capacitor.

[0013] Alternatively, the motor drive device described above may also include a support plate for the smoothing capacitor section, wherein the electrode terminals of the smoothing capacitor section and the electrode terminals of the buffer capacitor are arranged opposite each other across the support plate.

[0014] Alternatively, the motor drive device described above may include: a first conductor for electrically connecting the positive terminal of the smoothing capacitor section to the positive terminal of the buffer capacitor; and a second conductor for electrically connecting the negative terminal of the smoothing capacitor section to the negative terminal of the buffer capacitor, wherein the first conductor and the second conductor have portions close to each other.

[0015] For the aforementioned motor drive device, the support plate may also have multiple connecting portions, including a group of positive and negative connecting portions. The positive terminal of the smoothing capacitor is electrically connected to the positive terminal of the buffer capacitor via the first conductor of the positive connecting portion of any of the multiple connecting portions. The negative terminal of the smoothing capacitor is electrically connected to the negative terminal of the buffer capacitor via the second conductor of the negative connecting portion of any of the multiple connecting portions.

[0016] For the aforementioned motor drive device, the positive and negative terminals of the smoothing capacitor and the positive and negative terminals of the buffer capacitor may also be composed of screw-type terminals.

[0017] Alternatively, the positive terminal of the smoothing capacitor can be electrically connected to the first conductor using soldering, and the positive terminal of the buffer capacitor can be electrically connected to the first conductor using soldering, the negative terminal of the smoothing capacitor can be electrically connected to the second conductor using soldering, and the negative terminal of the buffer capacitor can be electrically connected to the second conductor using soldering.

[0018] For the aforementioned motor drive device, multiple smoothing capacitors can also be connected in series.

[0019] For the aforementioned motor drive device, it is also possible that multiple buffer capacitors are connected in parallel for the buffer capacitor.

[0020] The effects of the invention

[0021] According to a technical solution disclosed herein, a motor drive device that is easy to construct, small in size, and low in cost can be realized, which can reduce the heat loss of the smoothing capacitor and the heat loss of the buffer capacitor. Attached Figure Description

[0022] The invention can be more clearly understood by referring to the following figures.

[0023] Figure 1A This is a side view showing the mounting structure of the smoothing capacitor section, the buffer capacitor, and the power element of an electric motor drive device according to an embodiment of the present disclosure.

[0024] Figure 1B This is a perspective view showing the mounting structure of the smoothing capacitor section, the buffer capacitor, and the power element of an electric motor drive device according to an embodiment of the present disclosure.

[0025] Figure 2 This is a side view schematically showing the mounting structure of the smoothing capacitor section, the buffer capacitor, and the power element of an electric motor drive device according to an embodiment of the present disclosure.

[0026] Figure 3A It is a schematic diagram of a motor drive device that generates motor drive power based on AC power supplied by an AC power source, and it is also a circuit diagram of the motor drive device.

[0027] Figure 3B It is a schematic diagram of a motor drive device that generates motor drive power based on AC power supplied by an AC power source, and is a circuit diagram used to illustrate the generation of oscillating current.

[0028] Figure 4A This is a top view illustrating a first aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0029] Figure 4B This is a side view illustrating a first aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0030] Figure 5A This is a top view illustrating a second aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0031] Figure 5B This is a side view of a second aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0032] Figure 6A This is a side view of a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0033] Figure 6B This is a side view of a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0034] Figure 6C This is a top view illustrating a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0035] Figure 7 This is a diagram used to illustrate the positional relationship between the smoothing capacitor and the buffer capacitor in an existing electric motor drive device.

[0036] Figure 8 This is a diagram illustrating the positional relationship between the smoothing capacitor section and the buffer capacitor of an electric motor drive device according to an embodiment of the present disclosure.

[0037] Figure 9 This is a side view schematically showing the mounting structure of a motor drive device in one embodiment of this disclosure, in which multiple smooth capacitors are connected in series.

[0038] Figure 10 This is a side view schematically showing the mounting structure of a plurality of buffer capacitors connected in parallel in an electric motor drive device according to an embodiment of the present disclosure.

[0039] Figure 11A This is a top view illustrating a first aspect of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0040] Figure 11B This is a side view illustrating a first aspect of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0041] Figure 12A This is a top view of a second aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0042] Figure 12B This is a side view of a second aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0043] Figure 13A This is a top view of a third aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0044] Figure 13B This is a side view of a third aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure.

[0045] Figure 14 This is a side view illustrating a modified example of the connection portion of an electric motor drive device according to an embodiment of the present disclosure. Detailed Implementation

[0046] Hereinafter, a motor drive device having a smoothing capacitor section and a buffer capacitor will be described with reference to the accompanying drawings. For ease of understanding, the scale of these drawings has been appropriately altered. The configuration shown in the drawings is an example for implementation and is not limited to the illustrated embodiment.

[0047] Figure 1A This is a side view showing the mounting structure of the smoothing capacitor section, the buffer capacitor, and the power element of an electric motor drive device according to an embodiment of the present disclosure. Figure 1B This is a perspective view showing the mounting structure of the smoothing capacitor section, buffer capacitor, and power element of an electric motor drive device according to one embodiment of the present disclosure. Hereafter, portions labeled with the same reference numerals in different figures refer to components having the same function. Furthermore, Figure 2 This is a side view schematically showing the mounting structure of the smoothing capacitor section, buffer capacitor, and power element of an electric motor drive device according to one embodiment of the present disclosure. Additionally, Figure 3A It is a schematic diagram of a motor drive device that generates motor drive power based on AC power supplied by an AC power source, and it is also a circuit diagram of the motor drive device. Figure 3B This is a schematic diagram illustrating a motor drive device that generates motor drive power based on AC power supplied from an AC power source, and it is also a circuit diagram used to explain the generation of oscillating current. Figure 3A and Figure 3B In order to simplify the explanation, only the part corresponding to one phase is shown for the number of phases of AC power supply 2 and motor 3, but AC power supply 2 and motor 3 can be either single-phase or three-phase.

[0048] Before describing an embodiment of the electric motor drive device of this disclosure, refer to... Figure 3A and Figure 3B This section explains the circuit of a motor drive device that generates motor drive power based on AC power supplied by a self-contained AC power source, and the principle of oscillating current generation.

[0049] like Figure 3A and Figure 3B As shown, the motor drive device 1 includes: a converter circuit (rectifier circuit) 51, which converts the AC power supplied from the AC power source 2 into DC power and outputs it to the DC link; and an inverter circuit 52, which converts the DC power from the DC link into AC power and outputs the AC power as the motor drive power.

[0050] The inverter circuit 52 is composed of a bridge circuit consisting of a power element 15, which is a semiconductor switching element, and a diode connected in anti-parallel to the power element 15. Similarly, the converter circuit 51, when implemented with a diode rectifier circuit, does not have a power element; however, when implemented with a PWM-controlled rectifier circuit, it is similar to the inverter circuit 52, consisting of a power element and a bridge circuit consisting of a diode connected in anti-parallel to the power element. Examples of power elements include unipolar transistors such as FETs, bipolar transistors, IGBTs, thyristors, and GTOs. Furthermore, a combination of a semiconductor switching element and a diode can also be defined as a "power element," and such a power element is also called a "power module."

[0051] A smoothing capacitor section 11 is provided in the DC link between the converter circuit 51 and the inverter circuit 52 to smooth the voltage of the DC link. In the illustrated example, the smoothing capacitor section 11 and the buffer capacitor 12 are provided on both the DC output side of the diode in the converter circuit 51 and the DC input side of the power element 15 in the inverter circuit 52.

[0052] A closed circuit (loop circuit) is formed between each positive and negative terminal of the smoothing capacitor section 11 and between each positive and negative terminal of the buffer capacitor 12, thereby generating an inductive component. Figure 3B The inductor component is indicated by reference numeral 31 in the attached figure. In the inverter circuit 52, the DC power from the DC link is converted into AC power by alternately switching the upper power element 15-1 and the lower power element 15-2 on and off. For example, when the lower power element 15-2 is off, the current i returns through the diode D1 connected in anti-parallel to the upper power element 15-1. At this time, a surge voltage of L×di / dt is generated by the internal inductance of the upper power element 15-1. Using this surge voltage L×di / dt, the current flows to the buffer capacitor 12, and the voltage between the positive and negative terminals of the buffer capacitor 12 rises. As a result, with the presence of the inductor component 31, a potential difference is generated between the smoothing capacitor section 11 and the buffer capacitor 12, and an oscillating current is generated. If the distance between the smoothing capacitor section 11 and the buffer capacitor 12 becomes longer, the inductive component between the smoothing capacitor section 11 and the buffer capacitor 12 increases, and the potential difference between the smoothing capacitor section 11 and the buffer capacitor 12 further increases. Therefore, a larger oscillating current is generated between the smoothing capacitor section 11 and the buffer capacitor 12, and the heat loss of the smoothing capacitor section 11 and the heat loss of the buffer capacitor 12 increase.

[0053] To reduce the heat loss of the smoothing capacitor and the buffer capacitor caused by the generation of oscillating current, such as Figure 1A , Figure 1B as well as Figure 2As shown, an embodiment of the electric motor drive device 1 of this disclosure includes: a smoothing capacitor section 11 having at least one smoothing capacitor that smooths the voltage between a converter circuit and an inverter circuit in a power conversion circuit that generates electric motor drive power based on AC power supplied from an AC power source; a buffer capacitor 12 for suppressing surge voltage of a power element 15 constituting part of the power conversion circuit; and a support plate 13 for which the smoothing capacitor section 11 is disposed.

[0054] The smoothing capacitor section 11 may have at least one smoothing capacitor. The smoothing capacitor may be, for example, an electrolytic capacitor or a film capacitor. When the smoothing capacitor section 11 is composed of a single smoothing capacitor, this smoothing capacitor is preferably of large capacitance. Alternatively, when the smoothing capacitor section 11 is composed of multiple smoothing capacitors, a larger capacitance can be achieved by combining multiple small-capacity smoothing capacitors. Figure 1A and Figure 1B In the example shown, the smoothing capacitor section 11 has six smoothing capacitors 11-1, 11-2, 11-3, 11-4, 11-5, and 11-6. The connection relationship between the smoothing capacitors in the case where the smoothing capacitor section 11 is composed of multiple smoothing capacitors is not specifically intended to limit this embodiment. As an example, the smoothing capacitor section 11 may be configured by connecting in series groups of capacitors 11-1, 11-2, and 11-3 connected in parallel, and groups of capacitors 11-4, 11-5, and 11-6 connected in parallel.

[0055] In addition, the smoothing capacitor section 11 has electrode terminals 21 including a positive terminal 21P and a negative terminal 21N. Figure 1A The shape and position of the electrode terminal 21 shown, including the positive terminal 21P and the negative terminal 21N, are only one example and may be other shapes and positions.

[0056] A smooth capacitor section 11 is disposed on a support plate 13. The support plate 13 can be a printed circuit board with various components and wiring mounted on it, or a molded board without various components and wiring mounted on it. As materials constituting the support plate 13, for example, phenolic plastic, paper epoxy, glass fiber epoxy, alumina, or combinations thereof are available.

[0057] When the motor (not shown) driven by the motor drive unit 1 is a three-phase AC motor, power elements 15U, 15V, and 15W are respectively provided on phases U, V, and W. In the illustrated example, power elements 15U, 15V, and 15W are mounted on the printed circuit board 16, for example. Alternatively, power elements 15U, 15V, and 15W may also be mounted on the side of the support plate 13 opposite to the side where the smoothing capacitor section 11 is located. Reference numeral 23 indicates the input and output terminals of each power element 15U, 15V, and 15W. Figure 1B The shape and position of the input and output terminals 23 of each power element 15U, 15V, 15W shown are only one example, and other shapes and positions are also possible.

[0058] The buffer capacitor 12 is, for example, composed of an electrolytic capacitor, a film capacitor, etc. The buffer capacitor 12 is provided in each power element 15 and mounted on a printed circuit board 16. Figure 1A , Figure 1B as well as Figure 2 In the example shown, since the motor driven by the motor drive unit 1 is a three-phase AC motor, buffer capacitors 12U, 12V, and 12W are provided corresponding to the power elements 15U, 15V, and 15W. Furthermore, the buffer capacitor 12 has electrode terminals 22 including a positive terminal 22P and a negative terminal 22N.

[0059] The electrode terminals 21 of the smoothing capacitor section 11 and the electrode terminals 22 of the buffer capacitor 12 are arranged as close as possible across the support plate 13. More preferably, the electrode terminals 21 of the smoothing capacitor section 11 and the electrode terminals 22 of the buffer capacitor 12 are arranged opposite each other across the support plate 13. However, when each of the smoothing capacitors 11-1 to 11-6 constituting the smoothing capacitor section 11 includes an electrolytic capacitor, the smoothing capacitor section 11 is arranged such that its opening does not face the vertical direction, and this opening is used to prevent the increase of internal pressure when an overvoltage is applied.

[0060] The positive terminal 21P of the electrode terminal 21 of the smoothing capacitor section 11 is electrically connected to the positive terminal 22P of the electrode terminal 22 of the buffer capacitor 12 via a first conductor 14-1. Furthermore, the negative terminal 21N of the electrode terminal 21 of the smoothing capacitor section 11 is electrically connected to the negative terminal 22N of the electrode terminal 22 of the buffer capacitor 12 via a second conductor 14-2.

[0061] The positive terminal 21P and negative terminal 21N of the smoothing capacitor section 11 and the positive terminal 22P and negative terminal 22N of the buffer capacitor 12 are, for example, constructed using screw-type terminals. In this case, the first conductor 14-1 is electrically connected to the positive terminal 21P of the smoothing capacitor section 11 and to the positive terminal 22P of the buffer capacitor 12 by fastening with a conductive screw. The second conductor 14-2 is electrically connected to the negative terminal 21N of the smoothing capacitor section 11 and to the negative terminal 22N of the buffer capacitor 12 by fastening with a conductive screw.

[0062] Alternatively, the positive terminal 21P of the smoothing capacitor section 11 and the first conductor 14-1, and the positive terminal 22P of the buffer capacitor 12 and the first conductor 14-1 are respectively connected by soldering. The negative terminal 21N of the smoothing capacitor section 11 and the second conductor 14-2, and the negative terminal 22N of the buffer capacitor 12 and the second conductor 14-2 are respectively connected by soldering.

[0063] Examples of the first conductor 14-1 and the second conductor 14-2 include busbars, conductive cables, and conductive components with insulating films covering their outer surfaces. Busbars and conductive cables are conductors used to conduct large currents and are manufactured by sheet metal processing of metals such as copper, brass, or aluminum. For conductive components with insulating films, the conductive component portion is also a conductor used to conduct large currents and is manufactured by sheet metal processing of metals such as copper, brass, or aluminum. In particular, when the first conductor 14-1 and the second conductor 14-2 are respectively constituted by conductive components with insulating films, the insulating film is peeled off at the connection portions where the conductive components with insulating films are connected to the electrode terminals of the smoothing capacitor portion 11 and the buffer capacitor 12, exposing the conductive components to the outside. Conductive cables and conductive components with insulating films can be components with high rigidity, or they can be flexible components. In this embodiment, as an example, the first conductor 14-1 and the second conductor 14-2 are respectively formed by bus bars.

[0064] As described above, according to this embodiment, the electrode terminals 21 of the smoothing capacitor section 11 and the electrode terminals 22 of the buffer capacitor 12 are arranged as close as possible across the support plate 13. Therefore, the electrical paths between the positive terminal 21P of the smoothing capacitor section 11 and the positive terminal 22P of the electrode terminal 22 of the buffer capacitor 12, and between the negative terminal 21N of the smoothing capacitor section 11 and the negative terminal 22N of the electrode terminal 22 of the buffer capacitor 12, are shortened, thus reducing the inductance. Consequently, the oscillating current is reduced, and therefore, heat loss from the smoothing capacitor section 11 and the buffer capacitor 12 can be suppressed. Furthermore, since the heat loss from the smoothing capacitor section 11 and the buffer capacitor 12 is suppressed, a heat sink can be eliminated or reduced, enabling cost reduction, ease of construction, and miniaturization of the motor drive device. For example, when a cooling fan is used as the heat sink, the current used to operate the cooling fan can be eliminated or reduced, thus reducing the power consumption of the motor drive device.

[0065] Next, several configurations of the smoothing capacitor section 11 will be listed. Here, as an example, in the first and second configurations, the smoothing capacitor section 11 is composed of multiple smoothing capacitors, while in the third configuration, the smoothing capacitor section 11 is composed of a single smoothing capacitor.

[0066] Figure 4A This is a top view illustrating a first aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure. Figure 4B This is a side view illustrating a first aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0067] Figure 4A and Figure 4B The smooth capacitor section 11 of the first embodiment shown is... Figure 1A , Figure 1B as well as Figure 2 Similarly, the smoothing capacitor section 11 shown is constructed by using multiple ( Figure 4A and Figure 4BIn the example shown, eight smoothing capacitors 11-7 to 11-14 are electrically connected to each other and are mounted on the support plate 13. The smoothing capacitors 11-7 to 11-14 are electrically connected using soldering. By combining multiple small-capacity smoothing capacitors 11-7 to 11-14, the capacity of the smoothing capacitor section 11 can be increased. The connection relationship between the smoothing capacitors in the case where the smoothing capacitor section 11 is composed of multiple smoothing capacitors is not particularly intended to limit this embodiment. For example, the smoothing capacitor section 11 may be constructed by connecting a group of capacitors 11-7 to 11-10 connected in parallel and a group of capacitors 11-11 to 14 connected in parallel in series. Alternatively, the smoothing capacitor section 11 may be constructed by connecting the smoothing capacitors 11-7 to 11-14 in series. Alternatively, the smoothing capacitor section 11 may be constructed by connecting the smoothing capacitors 11-7 to 11-14 in parallel.

[0068] Figure 5A This is a top view illustrating a second aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure. Figure 5B This is a side view of a second aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure.

[0069] Figure 5A and Figure 5B The smooth capacitor section 11 of the second embodiment shown uses multiple ( Figure 5A and Figure 5B In the example shown, two screw-terminal type smooth capacitors 11-15 and 11-16 are electrically connected to each other. By combining multiple small-capacity smooth capacitors 11-15 and 11-16, the capacity of the smooth capacitor section 11 can be increased. Similar to the first embodiment, the connection relationship between the smooth capacitors in the case where the smooth capacitor section 11 is composed of multiple smooth capacitors is not particularly intended to limit this embodiment. For example, the smooth capacitor section 11 may be constructed by connecting the smooth capacitors 11-15 and 11-16 in series. Alternatively, the smooth capacitor section 11 may be constructed by connecting the smooth capacitors 11-15 and 11-16 in parallel.

[0070] Figure 6A This is a side view of a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure. Figure 6B This is a side view of a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure. Figure 6C This is a top view illustrating a third aspect of the smoothing capacitor section of an electric motor drive device according to an embodiment of the present disclosure. For example, when the voltage of the DC link is relatively low, the smoothing capacitor section 11 can be composed of a single smoothing capacitor 11-17.

[0071] Figure 7 This is a diagram illustrating the positional relationship between the smoothing capacitor and the buffer capacitor in an existing electric motor drive device. Figure 7 In the example shown, the negative Z-axis direction is set as the vertical direction. Additionally, in Figure 7 In the example shown, for the sake of simplicity, the smoothing capacitor 110 and the substrate 160 for providing the buffer capacitor 120 are shown separately, but in reality, the smoothing capacitor 110 is arranged to overlap with the substrate 160 in the positive Y-axis direction or the negative Y-axis direction.

[0072] Smoothing capacitors 110 are mostly constructed from electrolytic capacitors that can ensure a large capacitance with a small size. When an overvoltage is applied, the electrolytic capacitor generates gas due to the vaporization of the internal electrolyte, which may increase the internal pressure. Therefore, an opening for gas release is provided near the terminals. Thus, electrolytic capacitors have the following limitation: to prevent electrolyte leakage from the opening, the terminals must be positioned so that they do not face the vertical direction. Figure 7 In the example shown, the smoothing capacitor 110 is arranged with its positive terminal 210P and negative terminal 210N facing upwards along the Z-axis (positive Z-axis direction). On the other hand, when the buffer capacitor 120 (120U, 120V, 120W) must be positioned below the Z-axis of the substrate 160 of the motor drive device 100, the electrical path between the smoothing capacitor 110 and the buffer capacitor 120 becomes longer, thus increasing the inductance. Due to this larger inductance, the potential difference between the smoothing capacitor 110 and the buffer capacitor 120 increases, resulting in a larger oscillating current. Consequently, the heat loss of both the smoothing capacitor 110 and the buffer capacitor 120 increases. As described above, due to the particularly strict constraints on the placement of large electrolytic capacitors with screw terminals, the electrical path between the smoothing capacitor 110 and the buffer capacitor 120 becomes longer, and the heat loss of both becomes particularly large.

[0073] Figure 8 This is a diagram illustrating the positional relationship between the smoothing capacitor section and the buffer capacitor in a motor drive device according to an embodiment of this disclosure. Figure 8 In the example shown, the negative Z-axis direction is set as the vertical direction. Additionally, in Figure 8 In the example shown, for the sake of simplicity, the smoothing capacitor section 11 and the printed circuit board 16 for providing the buffer capacitor 12 are shown separately. However, in reality, the smoothing capacitor section 11 is arranged to overlap with the printed circuit board 16 in the positive Y-axis direction or the negative Y-axis direction.

[0074] Here, as an example, I will illustrate that Figure 4A and Figure 4B The smoothing capacitor section 11 of the first embodiment shown is provided in the motor drive device 1. The smoothing capacitor section 11 is constructed by electrically connecting smoothing capacitors 11-7 to 11-14 to each other, and is provided on the support plate 13.

[0075] The support plate 13 is provided with a connection portion 40 including a positive side connection portion 41P and a negative side connection portion 41N. When the buffer capacitor 12 (12U, 12V, 12W) is positioned below the Z-axis of, for example, the printed circuit board 16 of the motor drive device 1, the connection portion 40 is provided below the Z-axis of the support plate 13 as shown in the figure. The positive side connection portion 41P and the negative side connection portion 41N are, for example, composed of conductive members such as solder pads penetrating both sides of the support plate 13. The positive terminal 21P of the smoothing capacitor section 11 is connected by a first conductor ( Figure 8 (Not shown in the diagram) is electrically connected to the positive side connection part 41P, and the negative terminal 21N of the smoothing capacitor part 11 is connected by the second conductor ( Figure 8 (Not shown in the diagram) is electrically connected to the negative side connection 41N. The positive side connection 41P on the support plate 13 is also electrically connected to the positive terminal 22P of the buffer capacitor 12 via a first conductor. The negative side connection 41N on the support plate 13 is also electrically connected to the negative terminal 22N of the buffer capacitor 12 via a second conductor.

[0076] Alternatively, for example, the positive side connection portion 41P and the negative side connection portion 41N may be configured as holes penetrating the support plate 13, with the first conductor and the second conductor respectively passing through these holes. In this case, the positive terminal 21P of the smoothing capacitor portion 11 is directly electrically connected to the positive terminal 22P of the buffer capacitor 12 via the first conductor penetrating the positive side connection portion 41P formed by the hole. The negative terminal 21N of the smoothing capacitor portion 11 is directly electrically connected to the negative terminal 22N of the buffer capacitor 12 via the second conductor penetrating the negative side connection portion 41N formed by the hole.

[0077] Thus, since the buffer capacitor 12 and the connecting portion 40 are both located below the Z-axis, the electrode terminals 21 of the smoothing capacitor portion 11 and 22 of the buffer capacitor 12 are arranged close together. Consequently, the electrical paths between the positive terminal 21P of the smoothing capacitor portion 11 and the positive terminal 22P of the buffer capacitor 12, and between the negative terminal 21N of the smoothing capacitor portion 11 and the negative terminal 22N of the buffer capacitor 12, are shortened, thus reducing the inductance. Therefore, due to the reduction in oscillating current, heat loss in the smoothing capacitor portion 11 and the buffer capacitor 12 can be suppressed. Furthermore, in this embodiment, since the small-capacity smoothing capacitors 11-7 to 11-14 within the smoothing capacitor portion 11 can be arranged in relatively free positions, compared to… Figure 7 The smooth capacitor 110, which is composed of a large-capacity electrolytic capacitor with screw-type terminals, offers a high degree of design freedom.

[0078] The number and connection relationship of the smoothing capacitors in the smoothing capacitor section 11 can be appropriately determined, for example, based on the magnitude of the DC link voltage and the voltage rating of each smoothing capacitor. For example, the more smoothing capacitors connected in series in the smoothing capacitor section 11, the larger the DC link voltage can be handled.

[0079] in addition, Figure 9 This is a side view schematically showing the mounting structure of a motor drive device according to an embodiment of this disclosure, in which multiple smoothing capacitor sections are connected in series. By connecting multiple smoothing capacitor sections 11 in series, it is also possible to handle larger DC link voltages. In this case, multiple smoothing capacitor sections 11 are provided on the support plate 13.

[0080] In addition, the buffer capacitor 12 is provided corresponding to the power element 15 of each phase, but in the part corresponding to this one phase, the buffer capacitor 12 can also be connected in parallel to achieve a larger capacity. Figure 10 This is a schematic side view illustrating the mounting configuration of a motor drive device according to one embodiment of this disclosure, in which multiple buffer capacitors are connected in parallel. As needed, the capacity can be increased by connecting multiple buffer capacitors 12 in parallel, thus enabling the suppression of larger surge voltages. In this case, multiple buffer capacitors 12 are provided on the printed circuit board 16.

[0081] Next, several configurations of the first conductor 14-1 and the second conductor 14-2 for further suppressing oscillating current are listed. Since a closed circuit (loop circuit) is formed between the positive and negative terminals of the smoothing capacitor section 11 and between the positive and negative terminals of the buffer capacitor 12, an inductive component is generated to varying degrees. Therefore, by arranging the first conductor 14-1 and the second conductor 14-2 in a manner with portions close to each other, the magnitude of the inductive component 31 is reduced. The first conductor 14-1 is used to electrically connect the positive terminal 21P of the smoothing capacitor section 11 to the positive terminal 22P of the buffer capacitor 12, and the second conductor 14-2 is used to electrically connect the negative terminal 21N of the smoothing capacitor section 11 to the negative terminal 22N of the buffer capacitor 12.

[0082] Figure 11A This is a top view illustrating a first aspect of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 11B This is a side view illustrating a first configuration of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 11A and Figure 11B In the example shown, the support plate 13 is omitted from the drawing for simplicity. Figure 11A and Figure 11B In the first configuration shown, the first conductor 14-1 and the second conductor 14-2 overlap along the Y-axis near the middle.

[0083] Figure 12A This is a top view of a second aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 12B This is a side view illustrating a second aspect of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 12A and Figure 12B In the example shown, the support plate 13 is omitted from the illustration for the sake of simplicity. Figure 12A and Figure 12B The second form shown is also similar to Figure 11A and Figure 11B Similarly, in the first configuration shown, the first conductor 14-1 and the second conductor 14-2 overlap along the Y-axis in the intermediate attachment. However, Figure 12A and Figure 12B The second configuration shown differs in its arrangement near the connection between the smooth capacitor section 11 and the first conductor 14-1 and the second conductor 14-2, and in its arrangement near the connection between the buffer capacitor 12 and the first conductor 14-1 and the second conductor 14-2. Figure 11A and Figure 11BThe first form shown is different.

[0084] Figure 13A This is a top view of a third aspect illustrating the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 13B This is a side view illustrating a third aspect of the mounting structure of the first and second conductors of an electric motor drive device according to an embodiment of the present disclosure. Figure 13A and Figure 13B In the example shown, the support plate 13 is omitted from the drawing for simplicity. Figure 13A and Figure 13B In the third configuration shown, the first conductor 14-1 and the second conductor 14-2 overlap along the Z-axis near the middle.

[0085] Furthermore, for any of the first to third embodiments described above, insulation should be ensured between the first conductor 14-1 and the second conductor 14-2. For example, the first conductor 14-1 and the second conductor 14-2 can be separated to a degree that ensures insulation, or either or both of the first conductor 14-1 and the second conductor 14-2 can be covered with an insulating film.

[0086] Next, a modified example of the connecting portion 40 provided on the support plate 13 will be described.

[0087] Figure 14 This is a side view illustrating a modified example of the connection portion of an electric motor drive device according to an embodiment of the present disclosure. Figure 14 In the example shown, the negative Z-axis direction is set as the vertical direction. Additionally, in Figure 14 In the example shown, for the sake of simplicity, the support plate 13 and the printed circuit boards 16 (16A, 16B, 16C) for housing the buffer capacitor 12 are illustrated separately. However, in practice, any of the printed circuit boards 16A, 16B, 16C are arranged to overlap the support plate 13 in the positive Y-axis direction. The illustrated position of the buffer capacitor 12 at the printed circuit boards 16A, 16B, 16C is an example; the buffer capacitor 12 can also be placed at locations other than those shown on the printed circuit board 16.

[0088] If multiple connecting portions 40A, 40B, and 40C, each having a positive side connecting portion 41P and a negative side connecting portion 41N, are pre-set staggered along the Z-axis direction on the support plate 13, then the connecting portion that minimizes the electrical path between the electrode terminal 21 of the smoothing capacitor portion 11 and the electrode terminal 22 of the buffer capacitor 12 can be selected based on the position of the buffer capacitor 12 in the Z-axis direction on the printed circuit board 16. Figure 14In the example shown, the number of connecting parts provided on the support plate 13 is set to three, but it can also be two or more.

[0089] The positive terminal 21P of the smoothing capacitor 11 is electrically connected to the positive terminal 22P of the buffer capacitor 12 via a first conductor 14-1 of the positive side connection portion 41P of any of the multiple connection portions 40A, 40B, and 40C provided on the support plate 13. The negative terminal 21N of the smoothing capacitor 11 is electrically connected to the negative terminal 22N of the buffer capacitor 12 via a second conductor 14-2 of the negative side connection portion 41N of any of the multiple connection portions 40A, 40B, and 40C provided on the support plate 13.

[0090] For example, a printed circuit board 16A is arranged to overlap a support plate 13 in the positive Y-axis direction. The printed circuit board 16A has a buffer capacitor 12 located at its upper position in the Z-axis direction. In this case, a connection portion 40A is selected. In this case, the positive terminal 21P of the smoothing capacitor portion 11 is connected via a first conductor 14-1 (…). Figure 14 (Not shown in the figure) is electrically connected to the positive side connection portion 41P of the connection portion 40A, and the negative terminal 21N of the smoothing capacitor portion 11 is connected by the second conductor 14-2 ( Figure 14 (Not shown in the diagram) is electrically connected to the negative side connection portion 41N of the connection portion 40A. The positive side connection portion 41P of the connection portion 40A on the support plate 13 is also electrically connected to the positive terminal 22P of the buffer capacitor 12 on the printed circuit board 16A via the first conductor 14-1. The negative side connection portion 41N of the connection portion 40A on the support plate 13 is also electrically connected to the negative terminal 22N of the buffer capacitor 12 on the printed circuit board 16A via the second conductor 14-2.

[0091] For example, a printed circuit board 16B is arranged to overlap with a support plate 13 in the positive Y-axis direction. A buffer capacitor 12 is provided at the middle portion of the printed circuit board 16B in the Z-axis direction. In this case, a connection portion 40B is selected. In this case, the positive terminal 21P of the smoothing capacitor portion 11 is connected via a first conductor 14-1 (…). Figure 14 (Not shown in the figure) is electrically connected to the positive side connection 41P of the connection part 40B, and the negative terminal 21N of the smoothing capacitor part 11 is connected by the second conductor 14-2 ( Figure 14(Not shown) is electrically connected to the negative side connection portion 41N of the connection portion 40B. The positive side connection portion 41P of the connection portion 40B on the support plate 13 is also electrically connected to the positive terminal 22P of the buffer capacitor 12 on the printed circuit board 16B via the first conductor 14-1. The negative side connection portion 41N of the connection portion 40B on the support plate 13 is also electrically connected to the negative terminal 22N of the buffer capacitor 12 on the printed circuit board 16B via the second conductor 14-2.

[0092] For example, a printed circuit board 16C is arranged to overlap a support plate 13 in the positive Y-axis direction. The printed circuit board 16C has a buffer capacitor 12 located in the lower part of the Z-axis direction. In this case, a connection portion 40C is selected. In this case, the positive terminal 21P of the smoothing capacitor portion 11 is connected via a first conductor 14-1 (…). Figure 14 (Not shown in the figure) is electrically connected to the positive side connection 41P of the connection part 40C, and the negative terminal 21N of the smoothing capacitor part 11 is connected by the second conductor 14-2 ( Figure 14 (Not shown) is electrically connected to the negative side connection portion 41N of the connection portion 40C. The positive side connection portion 41P of the connection portion 40C on the support plate 13 is also electrically connected to the positive terminal 22P of the buffer capacitor 12 on the printed circuit board 16C via the first conductor 14-1. The negative side connection portion 41N of the connection portion 40C on the support plate 13 is also electrically connected to the negative terminal 22N of the buffer capacitor 12 on the printed circuit board 16C via the second conductor 14-2.

[0093] Thus, the electrode terminals 21 of the smoothing capacitor section 11 and the electrode terminals 22 of the buffer capacitor 12 are arranged close together via any one of the multiple connection portions 40A, 40B, and 40C. Therefore, the connection portions on the support plate 13 can be selected from the multiple connection portions 40A, 40B, and 40C such that the electrical path between the positive terminal 21P of the smoothing capacitor section 11 and the positive terminal 22P of the buffer capacitor 12, and the inductance between the negative terminal 21N of the smoothing capacitor section 11 and the negative terminal 22N of the buffer capacitor 12 are smaller (i.e., the heat loss of the smoothing capacitor section 11 and the heat loss of the buffer capacitor 12 can be more effectively suppressed). Therefore, if multiple connection portions ( Figure 14 The examples shown are connection portions 40A, 40B, and 40C. Regardless of the location of the buffer capacitor 12 on the printed circuit board 16, it can be designed to be supported by a support plate 13. Therefore, the variety of support plates 13 for the smoothing capacitor portion 11 can be reduced. As a result, the cost of the motor drive device 1 can be reduced and its construction simplified.

[0094] According to one aspect of this disclosure, an easy-to-construct, small-sized, and low-cost electric motor drive device can be realized, which can reduce the heat loss of the smoothing capacitor and the heat loss of the buffer capacitor.

Claims

1. A motor drive device, characterized in that, The electric motor drive device includes: The smoothing capacitor section has at least one smoothing capacitor that smooths the voltage between the converter circuit and the inverter circuit in the power conversion circuit, which generates motor drive power based on AC power supplied from an AC power source. A buffer capacitor for suppressing surge voltages in power components that form part of the power conversion circuit; and A support plate is provided for the smoothing capacitor section. The electrode terminals of the smoothing capacitor are arranged close to and opposite to the electrode terminals of the buffer capacitor, separated by the support plate. The positive terminal of the electrode terminal of the smoothing capacitor is electrically connected to the positive terminal of the electrode terminal of the buffer capacitor, and the negative terminal of the electrode terminal of the smoothing capacitor is electrically connected to the negative terminal of the electrode terminal of the buffer capacitor.

2. A motor drive device, characterized in that, The electric motor drive device includes: The smoothing capacitor section has at least one smoothing capacitor that smooths the voltage between the converter circuit and the inverter circuit in the power conversion circuit, which generates motor drive power based on AC power supplied from an AC power source. A buffer capacitor is used to suppress surge voltages of power elements that form part of the power conversion circuit; The first conductor is used to electrically connect the positive terminal of the electrode terminal of the smooth capacitor to the positive terminal of the electrode terminal of the buffer capacitor. A second conductor, used to electrically connect the negative terminal of the electrode terminals of the smoothing capacitor to the negative terminal of the electrode terminals of the buffer capacitor; and A support plate is provided for the smoothing capacitor section. The electrode terminals of the smoothing capacitor are arranged close to and opposite to the electrode terminals of the buffer capacitor, separated by the support plate. The positive terminal of the smoothing capacitor is electrically connected to the positive terminal of the buffer capacitor, and the negative terminal of the smoothing capacitor is electrically connected to the negative terminal of the buffer capacitor. The first conductor and the second conductor have portions that are close to each other.

3. The electric motor drive device according to claim 2, characterized in that, The support plate is provided with multiple connecting parts, including a combination of positive side connecting parts and negative side connecting parts. The positive terminal of the smoothing capacitor is electrically connected to the positive terminal of the buffer capacitor via the first conductor of the positive side connection portion, which is connected to any one of the plurality of connection portions; and the negative terminal of the smoothing capacitor is electrically connected to the negative terminal of the buffer capacitor via the second conductor of the negative side connection portion, which is connected to any one of the plurality of connection portions.

4. The electric motor drive device according to claim 2, characterized in that, The positive and negative terminals of the smooth capacitor section and the positive and negative terminals of the buffer capacitor are composed of screw-type terminals.

5. The electric motor drive device according to claim 2, characterized in that, The positive terminal of the smooth capacitor is electrically connected to the first conductor via soldering, and the positive terminal of the buffer capacitor is also electrically connected to the first conductor via soldering. The negative terminal of the smooth capacitor is electrically connected to the second conductor by soldering, and the negative terminal of the buffer capacitor is electrically connected to the second conductor by soldering.

6. The electric motor drive device according to any one of claims 1 to 5, characterized in that, Multiple smoothing capacitor sections are connected in series.

7. The electric motor drive device according to any one of claims 1 to 5, characterized in that, For the buffer capacitor, multiple buffer capacitors are connected in parallel.

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