Power conversion device

Abstract

A power conversion device (100) comprises: a capacitor element (12); switching elements (20), (21); a wiring member (30); a cooling body (3); and a heat-conductive insulating member (5). The wiring member (30) is connected to the capacitor element (12) and the switching elements (20), (21). The capacitor element (12) and the switching elements (20), (21) are mounted on the cooling body (3). The heat-conductive insulating member (5) is connected to the cooling body (3) and the wiring member (30). The wiring member (30) has a first contact portion (5a) and a second contact portion (5b). The wiring member (30) is connected to the capacitor element (12) at the first contact portion (5a), and connected to the switching elements (20), (21) at the second contact portion (5b). The heat resistance of the wiring member (30) from the first contact portion (5a) to the heat-conductive insulating member (5) is less than the heat resistance of the wiring member (30) from the second contact portion (5b) to the heat-conductive insulating member (5).

Description

Power Conversion Device

[0001] The present disclosure relates to a power conversion device.

[0002] In recent years, power conversion devices such as voltage-type inverters that convert DC power to AC power have been used not only in air conditioners, machine tools, railway drive systems, and elevators, but also in renewable energy power conditioners and electric vehicles. Known configurations of such power conversion devices include a cooler equipped with a capacitor element and a switching element, wiring members connected to the capacitor element and the switching element, and a thermally conductive insulating member connected to the wiring member and the cooler (see, for example, JP 2017-188998 A).

[0003] JP 2017-188998 A

[0004] However, because the above-mentioned power converters are used in a wide range of products, there is a demand for miniaturization of the power converters. In particular, there is a demand for miniaturization of the capacitor elements, which account for a large proportion of the volume of the power converter. One of the challenges in achieving this miniaturization is improving the cooling performance of the capacitor elements.

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a power conversion device with improved cooling performance for a capacitor element.

[0006] A power conversion device according to the present disclosure includes a capacitor element, a switching element, a wiring member, a cooling body, and a thermally conductive insulating member. The wiring member is electrically connected to the capacitor element and the switching element. The cooling body carries the capacitor element and the switching element. The thermally conductive insulating material is connected to the cooling body and the wiring member. The wiring member has a first contact portion and a second contact portion. The wiring member is connected to the capacitor element at the first contact portion. The wiring member is connected to the switching element at the second contact portion. The thermal resistance of the wiring member in a region from the first contact portion to the thermally conductive insulating member is smaller than the thermal resistance of the wiring member in a region from the second contact portion to the thermally conductive insulating member.

[0007] According to the above, it is possible to obtain a power conversion device in which the cooling performance of the capacitor element is improved.

[0008] 9 is a circuit diagram of a power conversion device according to embodiment 1. FIG. 1 is a perspective view of a power conversion device according to embodiment 1. FIG. 2 is a plan view of a power conversion device according to embodiment 1. FIG. 3 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 4 is a cross-sectional view taken along line V-V in FIG. 3. FIG. 5 is a plan view showing a modified example of the power conversion device according to embodiment 1. FIG. 6 is a circuit diagram of a power conversion device according to embodiment 2. FIG. 7 is a perspective view of a power conversion device according to embodiment 2. FIG. 8 is a plan view of a power conversion device according to embodiment 2. FIG. 9 is a cross-sectional view taken along line X-X in FIG. 9. FIG. 10 is a cross-sectional view taken along line XI-XI in FIG. 9. FIG. 11 is a cross-sectional view of a power conversion device according to embodiment 3. FIG. 12 is a cross-sectional view of a power conversion device according to embodiment 3. FIG. 13 is a cross-sectional view of a power conversion device according to embodiment 4. FIG. 14 is a cross-sectional view of a power conversion device according to embodiment 4.

[0009] Hereinafter, embodiments of the present disclosure will be described. Unless otherwise specified, the same or corresponding parts in the following drawings will be denoted by the same reference numerals, and the description thereof will not be repeated.

[0010] First Embodiment <Configuration of Power Conversion Device> Fig. 1 is a circuit diagram of a power conversion device 100 according to a first embodiment. Fig. 2 is a perspective view of the power conversion device 100 according to the first embodiment. Fig. 3 is a plan view of the power conversion device 100 according to the first embodiment. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 5 is a cross-sectional view taken along line V-V in Fig. 3.

[0011] The power conversion device 100 shown in Figures 1 to 5 is, for example, a power conversion device 100 that converts DC voltage to AC voltage and is composed of a capacitor module 1 that smooths the voltage, a power module 2 that converts DC (Direct Current) voltage to AC (Alternating Current) voltage, and wiring members 30 electrically connected to the capacitor module 1 and the power module 2. The wiring members 30 include a high-potential-side wiring member 30h and a low-potential-side wiring member 30l. The high-potential-side wiring member 30h is composed of a capacitor high-potential-side wiring member 31h, a power module high-potential-side wiring member 32h, and semiconductor element wiring members 34a and 34b. The low-potential-side wiring member 30l is composed of a capacitor low-potential-side wiring member 31l, a power module low-potential-side wiring member 32l, and a semiconductor element wiring member 34c.

[0012] First, the electrical circuit of the power conversion device 100 according to the first embodiment will be described. As shown in FIG. 1 , the capacitor module 1 includes a capacitor element 12, a capacitor high-potential-side wiring member 31h, and a capacitor low-potential-side wiring member 31l. Here, six capacitor elements 12a, 12b, 12c, 12d, 12e, and 12f are arranged as the capacitor elements 12. The capacitor elements 12a, 12b, 12c, 12d, 12e, and 12f are connected in parallel. The capacitor high-potential-side wiring member 31h is connected to the high-potential side of the capacitor element 12. The other end of the capacitor high-potential-side wiring member 31h, opposite the one end connected to the high-potential side of the capacitor element 12, is connected to a power module high-potential-side terminal 33h. The capacitor low-potential-side wiring member 31l is connected to the low-potential side of the capacitor element 12. The capacitor low potential side wiring member 31l is connected to the power module low potential side terminal portion 33l at the other end opposite to the one end connected to the low potential side of the capacitor element 12.

[0013] In the first embodiment, film capacitors are used for the six capacitor elements 12a, 12b, 12c, 12d, 12e, and 12f, but other types of capacitors may also be used. Also, although the six capacitor elements 12a, 12b, 12c, 12d, 12e, and 12f are connected in parallel, they may be connected in series, or may be connected in a series-parallel configuration that combines series and parallel connections.

[0014] In the first embodiment, the internal circuit of the power module 2 is a three-phase full-bridge inverter circuit. The power module 2 includes switching elements 20 and 21, a power module high-potential-side wiring member 32h, and a power module low-potential-side wiring member 32l. In the first embodiment, the switching elements 20 and 21 respectively include three-phase high-potential-side IGBT elements 20a, 20b, and 20c, high-potential-side diode elements 20d, 20e, and 20f, low-potential-side IGBT elements 21a, 21b, and 21c, and low-potential-side diode elements 21d, 21e, and 21f. The power module high-potential-side wiring member 32h includes a power module high-potential-side terminal portion 33h. The other end of the power module high-potential-side wiring member 32h, which is located opposite to the one end including the power module high-potential-side terminal portion 33h, is connected to the collector electrodes of the high-potential-side IGBT elements 20a, 20b, and 20c. The high-potential side diode elements 20d, 20e, and 20f are connected in anti-parallel to the high-potential side IGBT elements 20a, 20b, and 20c, respectively. The power module low-potential side wiring member 32l includes a power module low-potential side terminal portion 33l. The power module low-potential side wiring member 32l is connected to the emitter electrodes of the low-potential side IGBT elements 21a, 21b, and 21c at the other end opposite to the one end including the power module low-potential side terminal portion 33l. The low-potential side diode elements 21d, 21e, and 21f are connected in anti-parallel to the low-potential side IGBT elements 21a, 21b, and 21c, respectively.

[0015] In the first embodiment, the internal circuit of the power module 2 is a three-phase full-bridge inverter circuit, but may be another type of inverter circuit. For example, the internal circuit of the power module 2 may be a single-phase inverter, a dual three-phase inverter, or a multilevel inverter circuit such as a three-level inverter circuit. In addition, in the first embodiment, the power module 2 includes all inverter circuits, but the power module 2 may be configured with individual power elements. The power elements may be, for example, MOSFETs in addition to IGBT elements.

[0016] Next, the configuration of the power conversion device 100 in the first embodiment will be described. As shown in FIGS. 2 to 5 , the capacitor module 1 and the power module 2 are disposed on the upper surface of the cooling body 3. The cooling body 3 may have any configuration as long as it can transfer heat generated in the capacitor module 1 and the power module 2 and transmit the heat to the outside (for example, the surrounding space). For example, the cooling body 3 may perform convective heat dissipation and radiative heat dissipation to the surrounding space via its surface. Alternatively, the cooling body 3 may have a refrigerant flow path, as described below, formed therein, and heat may be transferred to the outside via the refrigerant flowing through the refrigerant flow path. Therefore, the cooling body 3 may be, for example, a housing that houses the capacitor module 1 and the power module. Alternatively, the cooling body 3 may be a separate member from the housing and connected to the housing. The material of the cooling body 3 may be, for example, a metal material such as aluminum (Al) or iron (Fe).

[0017] 4 and 5 , a refrigerant flow path 4 through which a refrigerant such as cooling water flows may be formed on the upper surface of the cooling body 3. The power module 2 is disposed directly above the refrigerant flow path 4. In this manner, the power module 2 is cooled by disposing the power module 2 directly above the refrigerant flow path 4. Furthermore, in order to more effectively cool the capacitor element 12, the refrigerant flow path 4 may be formed, for example, directly below the capacitor module 1. Note that the cooling method for the power module 2 may not be a cold water method in which cooling water flows through the refrigerant flow path 4, but may be an air-cooling method in which a cooling gas such as air flows through the refrigerant flow path 4.

[0018] The capacitor module 1 is electrically connected to the power module 2 by a capacitor high-potential side wiring member 31h and a capacitor low-potential side wiring member 31l. The capacitor high-potential side wiring member 31h and the capacitor low-potential side wiring member 31l are each connected to the cooling body 3 via a thermally conductive insulating member 5. Heat generated in the capacitor element 12 is dissipated to the refrigerant flow path 4 via the thermally conductive insulating member 5 and the cooling body 3. As a result, the capacitor element 12 is cooled. The thermally conductive insulating member 5 is made of, for example, silicone resin. The thermally conductive insulating member 5 may also be made of a resin material containing a thermally conductive filler.

[0019] 4 and 5, the capacitor module 1 is composed of a capacitor case 11, a capacitor element 12, a capacitor high-potential side wiring member 31h, a capacitor low-potential side wiring member 31l, and a capacitor sealing material 13. The capacitor element 12, the capacitor high-potential side wiring member 31h, the capacitor low-potential side wiring member 31l, and the capacitor sealing material 13 are arranged inside the capacitor case 11. The capacitor element 12 is arranged so as to be sandwiched between the capacitor high-potential side wiring member 31h and the capacitor low-potential side wiring member 31l.

[0020] The capacitor high-potential-side wiring member 31h is connected to the capacitor element 12. The capacitor case 11 has a through hole H. The capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l each extend from the inside to the outside of the capacitor case 11 through the through hole H. As shown in FIG. 5 , the capacitor high-potential-side wiring member 31h extends to the outside of the capacitor case 11 through the through hole H at the other end opposite to the one end connected to the capacitor element 12. The capacitor high-potential-side wiring member 31h is connected to the power module high-potential-side terminal 33h at the other end opposite to the one end connected to the capacitor element 12. The capacitor low-potential-side wiring member 31l is connected to the capacitor element 12. As shown in FIG. 4 , the capacitor low-potential-side wiring member 31l extends to the outside of the capacitor case 11 through the through hole H at the other end opposite to the one end connected to the capacitor element 12. The capacitor low-potential-side wiring member 31l is connected to the power module low-potential-side terminal 33l at the other end opposite the end connected to the capacitor element 12. The capacitor sealing material 13 seals the capacitor element 12 and the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l, excluding the portion extending to the outside of the capacitor case 11, so as to fill the inside of the capacitor case 11. The capacitor case 11 is made of, for example, PET (Polyethylene Terephthalate) resin. The capacitor case 11 may be made of an engineering plastic with excellent heat resistance, and therefore may be made of PET resin, PPS (Polyphenylene Sulfide) resin, or PBT (Polybutylene Terephthalate) resin.

[0021] The power module 2 is composed of switching elements 20 and 21, a power module high-potential side wiring member 32h, a power module low-potential side wiring member 32l, semiconductor element wiring members 34a, 34b, and 34c, an insulating member 25, a heat sink 26, a power module sealing material 23, and a power module case 24. In the first embodiment, the power module 2 is integrated with the heat sink 26, but the power module 2 may be configured without incorporating the heat sink 26. In this case, the heat sink 26 may be attached separately to the power module 2. The material of the power module case 24 is, for example, PET resin. The material of the power module case 24 may be an engineering plastic with excellent heat resistance, and therefore may be PPS resin or PBT resin in addition to PET resin.

[0022] On the low-potential side of the power module 2, as shown in FIG. 4 , the low-potential-side IGBT element 21a and the low-potential-side diode element 21d are disposed on the upper surface of the semiconductor element wiring member 34c. The semiconductor element wiring member 34c is surface-connected to the insulating member 25 on the side opposite to the side on which the low-potential-side IGBT element 21a and the low-potential-side diode element 21d are disposed. The low-potential-side IGBT element 21a and the low-potential-side diode element 21d are connected to the power module low-potential-side wiring member 32l on the side opposite to the side connected to the semiconductor element wiring member 34c. The low-potential-side diode element 21d has an anode connected to the power module low-potential-side wiring member 32l and a cathode connected to the semiconductor element wiring member 34c. The low-potential-side IGBT element 21a has an emitter connected to the power module low-potential-side wiring member 32l and a collector connected to the semiconductor element wiring member 34c. The power module low-potential-side wiring member 32l has a power module low-potential-side terminal portion 33l that extends to the outside of the power module case 24 at the other end opposite to the one end connected to the low-potential-side IGBT element 21a and the low-potential-side diode element 21d.

[0023] On the high-potential side of the power module 2, as shown in FIG. 5 , the high-potential side IGBT element 20a and the high-potential side diode element 20d are disposed on the upper surface of the semiconductor element wiring member 34b. The semiconductor element wiring member 34b is surface-connected to the insulating member 25 on the side opposite to the side on which the high-potential side IGBT element 20a and the high-potential side diode element 20d are disposed. The high-potential side IGBT element 20a and the high-potential side diode element 20d are connected to the semiconductor element wiring member 34a on the side opposite to the side connected to the semiconductor element wiring member 34b. The high-potential side diode element 20d has a cathode connected to the semiconductor element wiring member 34b and an anode connected to the semiconductor element wiring member 34a. The high-potential side IGBT element 20a has a collector connected to the semiconductor element wiring member 34b and an emitter connected to the semiconductor element wiring member 34a. The semiconductor element wiring member 34b is connected to the power module high-potential-side wiring member 32h on the surface where the high-potential-side IGBT element 20a and the high-potential-side diode element 20d are arranged. The power module high-potential-side wiring member 32h has a power module high-potential-side terminal portion 33h that extends to the outside of the power module case 24 at the other end opposite to the one end connected to the high-potential-side IGBT element 20a and the high-potential-side diode element 20d.

[0024] On each of the high-potential side and the low-potential side, the insulating member 25 is connected to the heat sink 26 on the surface opposite to the surface on which the switching elements 20, 21 are arranged. The heat sink 26 is mounted on the cooling body 3 so that the surface opposite to the surface connected to the insulating member 25 becomes the inner wall of the refrigerant flow path 4 (so as to block the refrigerant flow path 4). In this way, the refrigerant flow path 4, which is a sealed path, is formed. The heat sink 26 is cooled by the cooling water or cooling air flowing through the refrigerant flow path 4. As a result, the switching elements 20, 21 are cooled via the insulating member 25 and the semiconductor element wiring members 34b, 34c.

[0025] The power module sealing material 23 seals the switching elements 20, 21, the semiconductor element wiring members 34a, 34b, 34c, and the insulating member 25 so as to fill the area surrounded by the power module case 24 and the heat sink 26. The material of the power module sealing material 23 is, for example, a silicone gel material.

[0026] Here, the power conversion device 100 according to the first embodiment is characterized in that, as shown in FIGS. 2 to 5 , the thermally conductive insulating member 5 is arranged so that the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the capacitor module 1 to the thermally conductive insulating member 5 is smaller than the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the power module 2 to the thermally conductive insulating member 5.

[0027] Specifically, the capacitor high potential side wiring member 31h and the capacitor low potential side wiring member 31l have first contact portions 5a and second contact portions 5b. As shown in Figures 4 and 5, the portions of the capacitor high potential side wiring member 31h and the capacitor low potential side wiring member 31l that pass through the through holes H of the capacitor case 11 are referred to as first contact portions 5a. The portions of the capacitor high potential side wiring member 31h and the capacitor low potential side wiring member 31l that connect to the power module high potential side terminal portion 33h and the power module low potential side terminal portion 33l, respectively, are referred to as second contact portions 5b. The portions of the capacitor high potential side wiring member 31h and the capacitor low potential side wiring member 31l that connect to the thermally conductive insulating member 5 are referred to as third contact portions 5c. 4 and 5 , the third contact portion 5c may be a portion of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l that overlaps with a central portion of the thermally conductive insulator 5 in the direction along the extension of the wiring member. When the cross-sectional shapes of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l (shapes in a cross section perpendicular to the extension direction of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l) are uniform from the first contact portion 5a to the second contact portion 5b in a side view of the power conversion device 100, the distance L1 is set to be smaller than the distance L2. In this case, the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the capacitor module 1 to the thermally conductive insulator 5 is smaller than the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the power module 2 to the thermally conductive insulator 5.

[0028] 4 and 5 , distance L1 is the distance along the surface of thermally conductive insulating member 5 from first contact portion 5a to third contact portion 5c in a side view of power converter 100. Distance L2 is the distance along the surface of thermally conductive insulating member 5 from second contact portion 5b to third contact portion 5c in a side view of power converter 100.

[0029] When the cross-sectional shapes of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l are uniform from the first contact portion 5 a to the second contact portion 5 b, the thermally conductive insulating member 5 may be arranged so that the third contact portion 5 c of each of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l is closer to the capacitor than the midpoint between the first contact portion 5 a and the second contact portion 5 b. The midpoint is a point on the surface of each of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l, where the distance L1 is the same as the distance L2.

[0030] Fig. 6 is a plan view showing a modification of the power conversion device 100 according to the first embodiment. The power conversion device 100 shown in Fig. 6 basically has the same configuration as the power conversion device 100 shown in Figs. 1 to 5 , but differs from the power conversion device 100 shown in Figs. 1 to 5 in that the cross-sectional shapes of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l are not uniform. Specifically, as shown in Fig. 6 , in a plan view of the wiring member 30 seen from a direction perpendicular to the upper surface of the cooling body 3, the width in the Y direction of each of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l near the first contact portion 5 a is smaller than the width in the Y direction of each of the capacitor high-potential-side wiring member 31 h and the capacitor low-potential-side wiring member 31 l near the second contact portion 5 b. In this manner, when the cross-sectional shapes of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l are not uniform from the first contact portion 5a to the second contact portion 5b, the thermally conductive insulating member 5 may be arranged so that the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the capacitor module 1 to the thermally conductive insulating member 5 is smaller than the thermal resistance of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l in the region from the power module 2 to the thermally conductive insulating member 5, taking into consideration Fourier's law (described later). This arrangement increases the amount of heat generated in the capacitor element 12 and dissipated to the refrigerant flow path 4 via the thermally conductive insulating member 5 and the cooling body 3. As a result, the cooling performance of the capacitor element 12 is improved. For example, in the power conversion device 100 shown in FIG. 6, the thermally conductive insulating member 5 may be arranged closer to the capacitor module 1 so that the distance L1 is shorter than in the power conversion devices 100 shown in FIGS. 4 and 5. In addition, in the plan view shown in Figure 6, the width in the Y direction near the first contact portion 5a of each of the capacitor high potential side wiring member 31h and the capacitor low potential side wiring member 31l may be larger than the width in the Y direction near the second contact portion 5b.

[0031] Considering the flow of heat as being similar to the flow of electricity, the thermal resistance R (unit: K / W) of the thermally conductive and insulating member 5 in the first embodiment can be expressed by the following formula (1) based on Fourier's law. The distance L (unit: m) is the distance along the surface of the wiring member 30. The cross-sectional area A (unit: m ２ ) is the cross-sectional area of ​​the wiring member 30 in a cross section perpendicular to the direction along the surface of the wiring member 30. The thermal conductivity (unit: W / (m·K)) is a physical property value determined by the material of the wiring member 30.

[0032]

[0033] The cooling action of capacitor element 12 in power conversion device 100 according to the first embodiment will be described below.

[0034] In the power conversion device 100 according to the first embodiment, the heat generated on the low potential side includes heat Q21 generated in the low potential side IGBT element 21 a and the low potential side diode element 21 d in accordance with the operation of the low potential side IGBT element 21 a and the low potential side diode element 21 d, Joule heat Q19 generated in the power module low potential side wiring member 32 l as a result of current flowing from the low potential side IGBT element 21 a and the low potential side diode element 21 d, Joule heat Q15 generated in the capacitor low potential side wiring member 31 l as a result of current flowing from the low potential side IGBT element 21 a and the low potential side diode element 21 d, and Joule heat Q12 generated in the capacitor element 12 as a result of current flowing from the low potential side IGBT element 21 a and the low potential side diode element 21 d.

[0035] Most of the heat Q21 is dissipated to the coolant flow path 4 via the semiconductor element wiring member 34c, the insulating member 25, and the heat sink 26. The remaining heat Q21 is dissipated to the coolant flow path 4 via the power module low potential side wiring member 32l, the capacitor low potential side wiring member 31l, the thermally conductive insulating member 5, and the cooling body 3. The remaining heat Q21 dissipated via the thermally conductive insulating member 5 is referred to as the heat quantity Q211.

[0036] Most of the Joule heat Q19 is dissipated to the refrigerant flow path 4 via the low potential side IGBT element 21a, the low potential side diode element 21d, the semiconductor element wiring member 34c, the insulating member 25, and the heat sink 26. The remaining Joule heat Q19 is dissipated to the refrigerant flow path 4 via the capacitor low potential side wiring member 31l, the thermally conductive insulating member 5, and the cooling body 3. The amount of heat of the remaining Joule heat Q19 dissipated via the thermally conductive insulating member 5 is referred to as heat amount Q191.

[0037] The amount of Joule heat Q15 includes the amount of heat radiated to the refrigerant flow path 4 via the power module low potential side wiring member 32l, the low potential side IGBT element 21a and the low potential side diode element 21d, the semiconductor element wiring member 34c, the insulating member 25, and the heat sink 26, and the amount of heat radiated to the refrigerant flow path 4 via the thermally conductive insulating member 5 and the cooling body 3. Of this Joule heat Q15, the Joule heat Q15 radiated to the refrigerant flow path 4 via the thermally conductive insulating member 5 and the cooling body 3 is referred to as the amount of heat Q151.

[0038] Strictly speaking, Joule heat Q15 includes the amount of heat dissipated to the refrigerant flow path 4 via the capacitor sealing material 13, the capacitor case 11, and the cooling body 3. However, while the thermal conductivity of the copper material used for the capacitor low-potential-side wiring member 31l is 398 W / (m·K), the thermal conductivity of the epoxy resin material used for the capacitor sealing material 13 and the thermal conductivity of the PET resin material used for the capacitor case 11 are relatively small, at 0.2 W / (m·K) and 0.3 W / (m·K), respectively. Therefore, compared to the amount of heat Q151, the amount of heat dissipated to the refrigerant flow path 4 via the capacitor sealing material 13, the capacitor case 11, and the cooling body 3 is negligibly small and is not considered here.

[0039] The Joule heat Q12 is radiated to the refrigerant flow path 4 via the capacitor low-potential side wiring member 31l, the thermally conductive insulating member 5, and the cooling body 3. The heat quantity of this Joule heat Q15 is referred to as heat quantity Q151. Strictly speaking, part of the Joule heat Q12 is radiated to the refrigerant flow path 4 via the capacitor sealing material 13, the capacitor case 11, and the cooling body 3; however, like the Joule heat Q15, the heat quantity radiated to the refrigerant flow path 4 via the capacitor sealing material 13, the capacitor case 11, and the cooling body 3 is negligibly small and is therefore not taken into consideration.

[0040] Furthermore, the Joule heat Q12, Q15, Q19, and heat Q21 described above each include the amount of heat dissipated into the surrounding air via the capacitor case 11 or the power module case 24. However, when the thermal conductivity and convective heat transfer coefficient of the constituent materials are taken into consideration, the amount of heat dissipated into the surrounding air via the capacitor case 11 or the power module case 24 is negligibly small and is therefore not taken into consideration.

[0041] From the above, in the power conversion device 100 according to the first embodiment, the total amount of heat Q1 passing through the thermally conductive insulating material on the low potential side is expressed by the following formula (2).

[0042]

[0043] The high-potential side configuration of the power conversion device 100 according to the first embodiment differs from the low-potential side configuration in that the capacitor high-potential side wiring member 31h is connected to the top surface of the capacitor element 12 (the surface opposite the cooling body 3 when viewed from the capacitor element 12), and that the power module high-potential side wiring member 32h is connected to the semiconductor element wiring member 34b rather than to the switching elements 20, 21. Except for the above two points, the high-potential side configuration is the same as the low-potential side configuration, and therefore the cooling action on the high-potential side is the same as the cooling action on the low-potential side.

[0044] Here, of the heat generated in the high potential side IGBT element 20a and the high potential side diode element 20d in conjunction with the operation of the high potential side IGBT element 20a and the high potential side diode element 20d, the heat quantity that is dissipated to the refrigerant flow path 4 via the semiconductor element wiring member 34b, the power module high potential side wiring member 32h, the capacitor high potential side wiring member 31h, the thermally conductive insulating member 5, and the cooling body 3 is defined as heat quantity Q202.

[0045] Of the Joule heat generated in the power module high potential side wiring member 32h, the amount of heat dissipated to the refrigerant flow path 4 via the capacitor high potential side wiring member 31h, the thermally conductive insulating member 5, and the cooling body 3 is taken as heat amount Q182.

[0046] Of the Joule heat generated in the capacitor high potential side wiring member 31h, the amount of heat dissipated to the coolant flow path 4 via the thermally conductive insulating member 5 and the cooling body 3 is defined as a heat amount Q142.

[0047] Of the Joule heat Q12 generated in the capacitor element 12, the amount of Joule heat Q12 radiated to the refrigerant flow path 4 via the capacitor high potential side wiring member 31h, the thermally conductive insulating member 5, and the cooling body 3 is defined as the amount of heat Q122.

[0048] From the above, in the power conversion device 100 according to the first embodiment, the total amount of heat Q2 passing through the thermally conductive insulating material on the high potential side is expressed by the following formula (3).

[0049]

[0050] <Operation and Effect> The power conversion device 100 according to the present disclosure includes a capacitor element 12, switching elements 20, 21, a wiring member 30, a cooling body 3, and a thermally conductive insulating member 5. The wiring member 30 is electrically connected to the capacitor element 12 and the switching elements 20, 21. The cooling body 3 carries the capacitor element 12 and the switching elements 20, 21. The thermally conductive insulating member 5 is connected to the cooling body 3 and the wiring member 30. The wiring member 30 has a first contact portion 5a and a second contact portion 5b. The wiring member 30 is connected to the capacitor element 12 at the first contact portion 5a. The wiring member 30 is connected to the switching elements 20, 21 at the second contact portion 5b. The thermal resistance of the wiring member 30 in the region from the first contact portion 5a to the thermally conductive insulating member 5 is smaller than the thermal resistance of the wiring member 30 in the region from the second contact portion 5b to the thermally conductive insulating member 5.

[0051] In this manner, the thermal resistance of the wiring member 30 in the region from the first contact portion 5 a to the thermally conductive insulating member 5 is smaller than the thermal resistance of the wiring member 30 in the region from the second contact portion 5 b to the thermally conductive insulating member 5, so that heat generated in the capacitor element 12 can be effectively conducted to the cooling body 3 via the wiring member 30 and the thermally conductive insulating member 5. This suppresses a temperature rise in the capacitor element 12 due to heat Q12 generated in the capacitor element 12. Meanwhile, the amount of temperature rise in the thermally conductive insulating member 5 due to heat Q20 and heat Q21 generated in the switching elements 20 and 21, heat Q19 generated in the power module low-potential side wiring member 32 l, and heat Q18 generated in the power module high-potential side wiring member 32 h is reduced. As a result, a temperature rise in the capacitor element 12 due to a temperature rise in the thermally conductive insulating member 5 can be suppressed, thereby suppressing a temperature rise in the capacitor element 12.

[0052] In the above-mentioned power conversion device 100, when the portion of the wiring member 30 connected to the thermally conductive insulating member 5 is the third contact portion 5c, the distance L1 from the first contact portion 5a to the third contact portion 5c is also smaller than the distance L2 from the second contact portion 5b to the third contact portion 5c.

[0053] In this way, when the cross-sectional shape of the wiring member 30 is uniform, the thermal resistance of the wiring member 30 in the region from the first contact portion 5a to the thermally conductive insulating member 5 is smaller than the thermal resistance of the wiring member 30 in the region from the second contact portion 5b to the thermally conductive insulating member 5, thereby suppressing the temperature rise of the capacitor element 12.

[0054] In the power conversion device 100, the cooling body 3 has a refrigerant flow path 4 formed in a position facing the switching elements 20, 21. In this case, the heat transferred from the thermally conductive insulating member 5 to the cooling body 3 can be effectively removed by the refrigerant flowing through the refrigerant flow path 4, and the switching elements 20, 21 can be efficiently cooled.

[0055] In order to verify the effects of the power conversion device 100 according to the first embodiment as described above, the following simulation was carried out.

[0056] 1 to 5 , the temperature rise in the capacitor element when the position of the thermally conductive insulating member was changed was determined by simulation when the power conversion device as Example 1, which has the same configuration as the power conversion device 100 shown in Figures 1 to 5 , was operated with the temperatures of the low potential side IGBT element 21 a, the low potential side diode element 21 d, the semiconductor element wiring member 34 b, and the cooling body 3 set to 120°C, 120°C, 80°C, and 70°C. The ripple current flowing from the power module 2 to the capacitor module 1 was set to 200 Arms.

[0057] <Analysis Results> Table 1 shows the simulation results of Example 1 under the above analysis conditions. In Table 1, the position ratio of the thermally conductive insulating member 5 is the value obtained by dividing the distance L1 from the first contact portion 5a to the third contact portion 5c by the distance from the first contact portion 5a to the second contact portion 5b (distance L1 + distance L2). As can be seen from Table 1, the temperature of the capacitor element 12 after static settling in Example 1 is lower when the position ratio of the thermally conductive insulating member 5 is less than 50% than when the position ratio of the thermally conductive insulating member 5 is 50% or more. In other words, when the cross-sectional shape of the wiring member 30 is uniform, arranging the thermally conductive insulating member 5 closer to the first contact portion 5a than to the second contact portion 5b can suppress the temperature rise of the capacitor element 12.

[0058]

[0059] Second Embodiment <Configuration of Power Conversion Apparatus> Fig. 7 is a circuit diagram of a power conversion apparatus 100 according to a second embodiment. Fig. 7 corresponds to Fig. 1. Fig. 8 is a perspective view of the power conversion apparatus 100 according to the second embodiment. Fig. 8 corresponds to Fig. 2. Fig. 9 is a plan view of the power conversion apparatus 100 according to the second embodiment. Fig. 9 corresponds to Fig. 3. Fig. 10 is a cross-sectional view taken along line X-X in Fig. 9. Fig. 10 corresponds to Fig. 4. Fig. 11 is a cross-sectional view taken along line XI-XI in Fig. 9. Fig. 11 corresponds to Fig. 5.

[0060] The power conversion device 100 shown in Figures 7 to 11 basically has the same configuration as the power conversion device 100 shown in Figures 1 to 5, but differs from the power conversion device 100 shown in Figures 1 to 5 in that there is no thermally conductive insulating member 5 on the high potential side. Also, the circuit of the power conversion device 100 shown in Figure 7 differs from the circuit of the power conversion device 100 shown in Figure 1 in that it is composed of three capacitor elements 12.

[0061] The power conversion device 100 according to the second embodiment can be designed to accommodate a case in which the ripple current flowing through the capacitor module 1 is small. Because the ripple current flowing through the capacitor module 1 is small, the number of capacitor elements 12 connected in parallel within the capacitor module 1 may be, for example, three. In addition, since the number of capacitor elements 12 is set to three in the second embodiment, the external shape of the capacitor module 1 according to the second embodiment can be smaller than the external shape of the capacitor module 1 according to the first embodiment. Because the ripple current flowing through the capacitor module 1 is small, the cross-sectional areas of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l according to the second embodiment may be smaller than the cross-sectional areas of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l according to the first embodiment, for example, may be smaller by 38%.

[0062] In the power conversion device 100 of the second embodiment, since the ripple current is small, the resistance loss generated in each of the capacitor elements 12, the capacitor high potential side wiring member 31 h, the power module high potential side wiring member 32 h, the power module low potential side wiring member 32 l, and the capacitor low potential side wiring member 31 l through which the ripple current flows is small. Therefore, in the second embodiment, the thermally conductive insulating member 5 is arranged only on the low potential side.

[0063] The internal structure of the power module 2 on the high potential side is such that the insulating member 25, the semiconductor element wiring member 34b, the high potential side IGBT element 20a, and the high potential side diode element 20d are surface-bonded in this order when viewed from the heat sink 26. The power module high potential side wiring member 32h is also bonded to the semiconductor element wiring member 34b.

[0064] On the other hand, the internal structure of the low-potential side power module 2 is such that, as viewed from the heat sink 26, the insulating member 25, the semiconductor element wiring member 34c, the low-potential side IGBT element 21a, and the low-potential side diode element 21d are surface-bonded in this order. Therefore, the low-potential side IGBT element 21a and the low-potential side diode element 21d are heated to a higher temperature than the semiconductor element wiring member 34c. As a result, the power module low-potential side wiring member 32l, which is connected to the low-potential side IGBT element 21a and the low-potential side diode element 21d, is heated to a higher temperature than the power module high-potential side wiring member 32h, which is connected to the semiconductor element wiring member 34b. Therefore, connecting the thermally conductive insulating member 5 to the power module low-potential side wiring member 32l rather than to the power module high-potential side wiring member 32h can more effectively improve the cooling of the capacitor element 12.

[0065] In this way, the thermally conductive and insulating member 5 needs to be attached at only one location, and the structure of the power converter 100 according to the second embodiment is simplified.

[0066] <Effects> In the above-described power conversion device 100, the wiring member 30 is connected to the surface of each of the switching elements 20, 21 opposite to the surface facing the cooling body 3. The thermally conductive insulating member 5 is connected only to the cooling body 3 and the wiring member 30. In this manner, even if the wiring member 30 is connected to the surface of each of the switching elements 20, 21 opposite to the surface facing the cooling body 3, the heat generated in the switching elements 20, 21 can be dissipated to the cooling body 3 via the thermally conductive insulating member 5. As a result, it is possible to suppress a rise in the temperature of the capacitor element 12 due to the heat generated in the switching elements 20, 21, and consequently improve the cooling performance of the capacitor element 12.

[0067] In the power conversion device 100, the switching elements 20, 21 include a high-side switching element 20 and a low-side switching element 21. The wiring member 30 includes a high-side wiring member 30h and a low-side wiring member 30l. The high-side wiring member 30h is connected to the surface of the high-side switching element 20 facing the cooling body 3. The low-side switching element 21 is connected to the surface opposite the surface facing the cooling body 3. The thermally conductive insulating member 5 is connected only to the cooling body 3 and the low-side wiring member 30l. In this manner, even if there are multiple wiring members 30 connecting the capacitor element 12 and the switching elements 20, 21, it is not necessary to attach the thermally conductive insulating member 5 to all of the wiring members 30, thereby reducing the number of parts constituting the power conversion device 100. As a result, the structure of the power conversion device 100 can be simplified.

[0068] In order to verify the effects of the power conversion device 100 according to the second embodiment as described above, the following simulation was carried out.

[0069] <Analysis Conditions> The power conversion devices of Examples 2 and 3 were operated with the temperatures of the low-potential side IGBT element 21a, the low-potential side diode element 21d, the semiconductor element wiring member 34b, and the cooling body 3 set to 120°C, 120°C, 80°C, and 70°C, respectively, and the temperature rise in the capacitor element when the position of the thermally conductive insulating member was changed was determined by simulation. The ripple current flowing from the power module 2 to the capacitor module 1 was set to 100 Arms. Example 2 has a configuration similar to that of the power conversion device 100 according to the second embodiment, with the thermally conductive insulating member 5 being arranged only on the low-potential side. Example 3 has a configuration in which the thermally conductive insulating member 5 is not arranged on the low-potential side but is arranged only on the high-potential side.

[0070] <Analysis Results> Table 2 shows the simulation results under the above conditions.

[0071]

[0072] As can be seen from Table 2, regardless of the comparison of the position ratio of the thermally conductive insulating member 5, the temperature of the capacitor element 12 after settling in Example 2 is lower than the temperature of the capacitor element 12 after settling in Example 3. Furthermore, in both Examples 2 and 3, the temperature of the capacitor element 12 after settling is relatively lower when the position ratio of the thermally conductive insulating member 5 is less than 50% than when the position ratio of the thermally conductive insulating member 5 is 50% or more. This is the same as the simulation result for the power conversion device 100 according to Embodiment 1.

[0073] Third Embodiment <Configuration of Power Conversion Apparatus> Figures 12 and 13 are cross-sectional views of a power conversion apparatus 100 according to a third embodiment. Figure 12 corresponds to Figure 4. Figure 13 corresponds to Figure 5.

[0074] The power converter 100 shown in Figures 12 and 13 basically has the same configuration as the power converter 100 shown in Figures 1 to 5, but differs from the power converter 100 shown in Figures 1 to 5 in that the entire thermally conductive insulating member 5 is located closer to the capacitor than the midpoint between the first contact portion 5a and the second contact portion 5b. Specifically, as shown in Figures 12 and 13, the third contact portion 5c is a portion of the wiring member that overlaps with one end of the thermally conductive insulating member 5 (a point farther from the first contact portion 5a) in the direction along the extension direction of the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l.

[0075] The third contact portion 5c may be located closer to the capacitor element 12 than the midpoint between the first contact portion 5a and the second contact portion 5b. In other words, both ends of the thermally conductive insulating member 5 may be located closer to the capacitor than the midpoint between the first contact portion 5a and the second contact portion 5b in the direction along which the capacitor high-potential-side wiring member 31h and the capacitor low-potential-side wiring member 31l extend.

[0076] In this way, the thermally conductive and insulating member 5 is disposed on the capacitor element 12 side, and therefore the temperature rise of the capacitor element 12 can be further suppressed.

[0077] <Effects> In the power converter 100, the entire thermally conductive insulating member 5 is located closer to the capacitor element 12 than the midpoint between the first contact portion 5 a and the second contact portion 5 b. This makes it possible to further suppress the temperature rise of the capacitor element 12.

[0078] Fourth Embodiment <Configuration of Power Conversion Device> Figures 14 and 15 are cross-sectional views of a power conversion device 100 according to a fourth embodiment. Figure 14 corresponds to Figure 4. Figure 15 corresponds to Figure 5.

[0079] The power conversion device 100 shown in Figures 14 and 15 basically has the same configuration as the power conversion device 100 shown in Figures 1 to 5, but differs from the power conversion device 100 shown in Figures 1 to 5 in that the thermally conductive insulating member 5 is in contact with the capacitor elements 12. Specifically, the thermally conductive insulating member 5 is in indirect contact with the capacitor elements 12 by being in contact with the side surface of the capacitor case 11. The capacitor module 1 may be composed of the capacitor elements 12, a capacitor high-potential side wiring member 31h, and a capacitor low-potential side wiring member 31l, and the thermally conductive insulating member 5 may be in direct contact with the capacitor elements 12.

[0080] In this way, the thermally conductive and insulating member 5 is disposed on the capacitor element 12 side, and therefore the temperature rise of the capacitor element 12 can be further suppressed.

[0081] <Operation and Effect> In the power converter 100, the thermally conductive insulating member 5 is in contact with the capacitor element 12. In this way, the temperature rise of the capacitor element 12 can be further suppressed.

[0082] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0083] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) A power conversion device comprising: a capacitor element; a switching element; a wiring member electrically connected to the capacitor element and the switching element; a cooling body mounting the capacitor element and the switching element; and a thermally conductive insulating member connected to the cooling body and the wiring member, wherein the wiring member has a first contact portion and a second contact portion, the wiring member is connected to the capacitor element at the first contact portion, and the wiring member is connected to the switching element at the second contact portion, and the thermal resistance of the wiring member in a region from the first contact portion to the thermally conductive insulating member is smaller than the thermal resistance of the wiring member in a region from the second contact portion to the thermally conductive insulating member. (Appendix 2) The power conversion device according to Appendix 1, wherein, when a portion of the wiring member connected to the thermally conductive insulating member is defined as a third contact portion, the distance from the first contact portion to the third contact portion is also smaller than the distance from the second contact portion to the third contact portion. (Supplementary Note 3) The power conversion device according to Supplementary Note 1 or Supplementary Note 2, wherein the wiring member is connected to a surface of the switching element opposite to a surface facing the cooling body, and the thermally conductive insulating member is connected only to the cooling body and the wiring member. (Supplementary Note 4) The power conversion device according to Supplementary Note 1 or Supplementary Note 2, wherein the switching elements include high-potential side switching elements and low-potential side switching elements, the wiring member includes high-potential side wiring member and low-potential side wiring member, the high-potential side switching elements are connected to a surface facing the cooling body, and the low-potential side switching elements are connected to a surface opposite to a surface facing the cooling body, and the thermally conductive insulating member is connected only to the cooling body and the low-potential side wiring member. (Supplementary Note 5) The power conversion device according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the cooling body has a refrigerant flow path formed in a position facing the switching elements. (Supplementary Note 6) The power conversion device according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the entire thermally conductive insulating member is located closer to the capacitor element than a midpoint between the first contact portion and the second contact portion.(Supplementary Note 7) The power conversion device according to any one of Supplementary Note 1 to Supplementary Note 6, wherein the thermally conductive insulating member is in contact with the capacitor element.

[0084] REFERENCE SIGNS LIST 1 Capacitor module, 2 Power module, 3 Cooling body, 4 Coolant flow path, 5 Thermally conductive insulating member, 5a First contact portion, 5b Second contact portion, 5c Third contact portion, 11 Capacitor case, 12 Capacitor element, 13 Capacitor sealing material, 20, 21 Switching element, 20 High potential side switching element, 20a High potential side IGBT element, 20d High potential side diode element, 21 Low potential side switching element, 21a Low potential side IGBT element, 21d Low potential side diode element, 23 Power module sealing material, 24 Power module case, 25 Insulating member, 26 Heat sink, 30 Wiring member, 30h High potential side wiring member, 30l Low potential side wiring member, 31h Capacitor high potential side wiring member, 31l Capacitor low potential side wiring member, 32h Power module high potential side wiring member, 32l Power module low potential side wiring member, 33h Power module high potential side terminal portion, 33l: power module low potential side terminal portion, 34a, 34b, 34c: semiconductor element wiring member, 100: power conversion device, L, L1, L2: distance, H: through hole.

Claims

1. A capacitor element; A switching element; a wiring member electrically connected to the capacitor element and the switching element; A cooling body; a thermally conductive insulating member connected to the cooling body and the wiring member, the wiring member has a first contact portion and a second contact portion; the wiring member is connected to the capacitor element at the first contact portion, the wiring member is connected to the switching element at the second contact portion, A power conversion device, wherein the thermal resistance of the wiring member in a region from the first contact portion to the thermally conductive insulating member is smaller than the thermal resistance of the wiring member in a region from the second contact portion to the thermally conductive insulating member.

2. When a portion of the wiring member connected to the thermally conductive insulating member is defined as a third contact portion, The power conversion device according to claim 1 , wherein a distance from the first contact portion to the third contact portion is smaller than a distance from the second contact portion to the third contact portion.

3. The switching element has a surface opposite to a surface facing the cooling body, and the wiring member is connected to the surface opposite to the surface facing the cooling body.

3. The power conversion device according to claim 1, wherein the thermally conductive insulating member is connected only to the cooling body and the wiring member.

4. The switching element includes a high potential side switching element and a low potential side switching element, The wiring member includes a high potential side wiring member and a low potential side wiring member, the high potential side switching element has a surface facing the cooling body to which the high potential side wiring member is connected; The low potential side switching element has a surface opposite to a surface facing the cooling body, and the low potential side wiring member is connected to the surface opposite to the surface facing the cooling body.

3. The power conversion device according to claim 1, wherein the thermally conductive insulating member is connected only to the cooling body and the low potential side wiring member.

5. 3. The power conversion device according to claim 1, wherein the cooling body has a coolant flow path formed in a position facing the switching element.

6. 3 . The power conversion device according to claim 1 , wherein the entirety of the thermally conductive insulating member is located closer to the capacitor element than a midpoint between the first contact portion and the second contact portion.

7. The power conversion device according to claim 1 , wherein the thermally conductive insulating member is in contact with the capacitor element.

8. A power conversion device as described in claim 1 or claim 2, wherein the switching element is mounted on the cooling body.

9. A power conversion device as described in claim 8, wherein the capacitor element is mounted on the cooling body.