WO2024202932A1 - Power conversion device - Google Patents

Abstract

A power conversion device (4) comprises: a semiconductor module (20) constituting an inverter (5); coolers (30, 40) for cooling the semiconductor module (20) from both surface sides; and connection pipes (50, 60) for connecting the coolers (30, 40). The cooler (30) defines a flow path (32) and has: a case (31) having an opening (311) at a portion overlapping with the semiconductor module (20); a base plate (331) disposed in the case (31) so as to cover the opening (311); and pin fins (332) extending from the base plate (331) into the flow path (32). In the arrangement direction of the connection pipes (50, 60), the length of the base plate (331) is shorter than the length between the outer ends of the connection pipes (50, 60).

Description

Power Conversion Equipment CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on patent application No. 2023-55860 filed in Japan on March 30, 2023, and the contents of the original application are incorporated by reference in their entirety.

The disclosure in this specification relates to a power conversion device.

Patent document 1 discloses a power conversion device. The contents of the prior art document are incorporated by reference as explanations of the technical elements in this specification.

Chinese Patent Publication No. 114068450

The power conversion device disclosed in Patent Document 1 is equipped with a two-stage cooler. The power conversion device has a structure that dissipates heat from the chips that make up the inverter to both sides. The cooler case is provided with fins for heat dissipation. In the configuration of Patent Document 1, there is a risk that the case will bend outward, i.e., deform, due to water pressure. If the case bends outward, the gap between the fins and the case will become larger, and more refrigerant will pass through without hitting the fins, reducing heat dissipation. If the case deforms, the adhesion between the case and the chips will decrease, and thermal resistance will increase. Thus, there is a risk that the configuration of Patent Document 1 will reduce heat dissipation. In the above-mentioned perspectives, or in other perspectives not mentioned, further improvements are required for power conversion devices.

One disclosed objective is to provide a power conversion device that can suppress a decrease in heat dissipation.

The power conversion device disclosed herein is
A semiconductor module that configures a power conversion circuit;
a first cooler having a first flow path and configured to cool the semiconductor module;
a second cooler having a second flow path and cooling the semiconductor module from an opposite side to the first cooler;
a first connecting portion having a first connecting flow path communicating with the first flow path and the second flow path;
a second connecting portion having a second connecting flow path communicating with the first flow path and the second flow path and providing a bypass path for a portion of the refrigerant together with the first connecting portion;
the first cooler includes a case that defines a first flow path and has an opening at a portion that overlaps with the semiconductor module, a base plate that is disposed on the case so as to cover the opening, and pin fins that extend from the base plate into the first flow path;
In the arrangement direction of the first connecting portion and the second connecting portion, the length of the base plate is shorter than the length between the outer ends of the first connecting portion and the second connecting portion.

In the disclosed power conversion device, the length of the base plate is shorter than the length between the outer ends of the first connecting part and the second connecting part, so deformation of the base plate due to water pressure can be suppressed. As a result, a power conversion device can be provided that can suppress a decrease in heat dissipation performance.

The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The reference characters in parentheses in the claims are illustrative of the corresponding relationships with the parts of the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and advantages disclosed in this specification will become clearer with reference to the detailed description that follows and the attached drawings.

1 is a diagram showing a circuit configuration and a drive system of a power conversion device according to a first embodiment; FIG. 2 is a plan view showing the power conversion device. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 . FIG. 3 is a cross-sectional view taken along line IV-IV in FIG. 2 . FIG. FIG. FIG. 11 is a plan view showing a power conversion device according to a second embodiment. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7 .

Below, several embodiments will be described with reference to the drawings. Note that in each embodiment, corresponding components will be given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of the other embodiment previously described may be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

The power conversion device of this embodiment is applied, for example, to a moving body that uses a rotating electric machine as a drive source. Examples of moving bodies include electric vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric flying objects such as drones and electric vertical take-off and landing aircraft (eVTOLs), ships, construction machinery, and agricultural machinery. Below, an example of application to a vehicle is described.

First Embodiment
First, a schematic configuration of a drive system of a vehicle will be described with reference to FIG.

<Vehicle drive system>
As shown in FIG. 1 , a vehicle drive system 1 includes a DC power supply 2 , a motor generator 3 , and a power conversion device 4 .

The DC power source 2 is a DC voltage source composed of a chargeable and dischargeable secondary battery. The secondary battery is, for example, a lithium ion battery, a nickel-metal hydride battery, or an organic radical battery. The motor generator 3 is a three-phase AC rotating electric machine. The motor generator 3 functions as a drive source for the vehicle, that is, an electric motor. The motor generator 3 functions as a generator during regeneration. The power conversion device 4 converts power between the DC power source 2 and the motor generator 3.

<Circuit configuration of power conversion device>
1 shows a circuit configuration of a power conversion device 4. The power conversion device 4 includes at least a power conversion circuit. The power conversion circuit in this embodiment is an inverter 5. The power conversion device 4 may further include a smoothing capacitor 6, a drive circuit 7, and the like.

The smoothing capacitor 6 mainly smoothes the DC voltage supplied from the DC power supply 2. The smoothing capacitor 6 is connected to the P line 8, which is the high-potential power supply line, and the N line 9, which is the low-potential power supply line. The P line 8 is connected to the positive electrode of the DC power supply 2, and the N line 9 is connected to the negative electrode of the DC power supply 2. The positive electrode of the smoothing capacitor 6 is connected to the P line 8 between the DC power supply 2 and the inverter 5. The negative electrode of the smoothing capacitor 6 is connected to the N line 9 between the DC power supply 2 and the inverter 5. The smoothing capacitor 6 is connected in parallel to the DC power supply 2.

The inverter 5 is a DC-AC conversion circuit. In accordance with switching control by a control circuit (not shown), the inverter 5 converts DC voltage into three-phase AC voltage and outputs it to the motor generator 3. This drives the motor generator 3 to generate a predetermined torque. During regenerative braking of the vehicle, the inverter 5 converts the three-phase AC voltage generated by the motor generator 3 in response to rotational force from the wheels into DC voltage in accordance with switching control by the control circuit and outputs it to the P line 8. In this way, the inverter 5 performs bidirectional power conversion between the DC power source 2 and the motor generator 3.

The inverter 5 is configured with upper and lower arm circuits 10 for three phases. The upper and lower arm circuits 10 are sometimes referred to as legs. The upper and lower arm circuits 10 each have an upper arm 10H and a lower arm 10L. The upper arm 10H and the lower arm 10L are connected in series between the P line 8 and the N line 9, with the upper arm 10H on the P line 8 side.

The connection point between the upper arm 10H and the lower arm 10L, i.e., the midpoint of the upper and lower arm circuits 10, is connected to the winding 3a of the corresponding phase in the motor generator 3 via an output line 11. Of the upper and lower arm circuits 10, the U-phase upper and lower arm circuit 10U is connected to the U-phase winding 3a via an output line 11. The V-phase upper and lower arm circuit 10V is connected to the V-phase winding 3a via an output line 11. The W-phase upper and lower arm circuit 10W is connected to the W-phase winding 3a via an output line 11.

The upper and lower arm circuits 10 (10U, 10V, 10W) have a series circuit 12. The upper and lower arm circuits 10 may have one or more series circuits 12. When there are multiple series circuits 12, the series circuits 12 are connected in parallel to each other to form one phase of the upper and lower arm circuit 10. In this embodiment, each of the upper and lower arm circuits 10 has one series circuit 12. The series circuit 12 is configured by connecting the switching element on the upper arm 10H side and the switching element on the lower arm 10L side in series between the P line 8 and the N line 9.

The number of high-side switching elements and low-side switching elements constituting the series circuit 12 is not particularly limited. It may be one or more. The series circuit 12 of this embodiment has two switching elements on the high-side and two switching elements on the low-side. The two switching elements on the high-side are connected in parallel, and the two switching elements on the low-side are connected in parallel to constitute one series circuit 12. In other words, each of the six arms 10H, 10L of the three-phase upper and lower arm circuits 10 is composed of two switching elements connected in parallel to each other.

In this embodiment, an n-channel MOSFET 13 is used as each switching element. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. The two high-side MOSFETs 13 connected in parallel are turned on and off at the same timing by a common gate drive signal (drive voltage). The two low-side MOSFETs 13 connected in parallel are turned on and off at the same timing by a common gate drive signal (drive voltage).

Each MOSFET 13 is connected inversely parallel to a freewheeling diode 14 (hereinafter referred to as FWD 14). In the case of MOSFET 13, FWD 14 may be a parasitic diode (body diode) or an external diode. In the upper arm 10H, the drain of MOSFET 13 is connected to the P line 8. In the lower arm 10L, the source of MOSFET 13 is connected to the N line 9. The source of MOSFET 13 in the upper arm 10H and the drain of MOSFET 13 in the lower arm 10L are connected to each other. The anode of FWD 14 is connected to the source of the corresponding MOSFET 13, and the cathode is connected to the drain.

The switching element is not limited to MOSFET 13. For example, an IGBT may be used. IGBT is an abbreviation for Insulated Gate Bipolar Transistor. In the case of an IGBT, FWD 14 is also connected in inverse parallel.

The drive circuit 7 drives the switching elements that make up a power conversion circuit such as the inverter 5. The drive circuit 7 supplies a drive voltage to the gate of the corresponding MOSFET 13 based on a drive command from the control circuit. By applying a drive voltage, the drive circuit drives the corresponding MOSFET 13, i.e., turns it on and off. The drive circuit is sometimes called a driver.

The power conversion device 4 may include a control circuit for the switching element. The control circuit generates a drive command for operating the MOSFET 13 and outputs it to the drive circuit 7. The control circuit generates the drive command based on, for example, a torque request input from a host ECU (not shown) and signals detected by various sensors. ECU is an abbreviation for Electronic Control Unit. The control circuit may be provided within the host ECU.

The various sensors include, for example, a current sensor, a rotation angle sensor, and a voltage sensor. The power conversion device 4 may be equipped with at least one of the sensors. The current sensor detects the phase current flowing through the winding 3a of each phase. The rotation angle sensor detects the rotation angle of the rotor of the motor generator 3. The voltage sensor detects the voltage across the smoothing capacitor 6. The control circuit is configured to include, for example, a processor and a memory. The control circuit outputs, for example, a PWM signal as a drive command. PWM is an abbreviation for Pulse Width Modulation.

The power conversion device 4 may include a converter as a power conversion circuit. The converter is a DC-DC conversion circuit that converts a DC voltage, for example, into a DC voltage of a different value. The converter is provided between the DC power source 2 and the smoothing capacitor 6. The converter is configured, for example, with a reactor and the above-mentioned upper and lower arm circuits 10. With this configuration, voltage can be increased and decreased. The power conversion device 4 may include a filter capacitor that removes power supply noise from the DC power source 2. The filter capacitor is provided between the DC power source 2 and the converter.

<Structure of power conversion device>
FIG. 2 is a plan view showing an example of the power conversion device 4 according to the present embodiment. For convenience, signal terminals and a circuit board are omitted in FIG. 2. The white arrows in FIG. 2 indicate the direction of flow of the refrigerant. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. In FIG. 4, a part of the housing and the circuit board are omitted. In FIG. 4, the solid arrows in FIG. 4 indicate the flow of the refrigerant. FIG. 5 is a plan view showing a heat dissipation member. The white arrows in FIG. 5 also indicate the direction of flow of the refrigerant.

The power conversion device 4 of this embodiment includes a semiconductor module 20, coolers 30 and 40, and connecting pipes 50 and 60. The power conversion device 4 may also include a circuit board 70 as shown in FIG. 3.

In the following, the stacking direction of the semiconductor modules 20 and the coolers 30, 40 is referred to as the Z direction. The direction perpendicular to the Z direction and in which the connecting pipes 50, 60 are arranged is referred to as the X direction. The direction perpendicular to both the X direction and the Z direction is referred to as the Y direction. The X direction, Y direction, and Z direction are in a mutually perpendicular positional relationship. Unless otherwise specified, a planar shape refers to a shape viewed from the Z direction. A planar view from the Z direction may simply be referred to as a planar view. When describing the relative positions of two components, the position of the component closer to the cooler 30 in the Z direction may be referred to as the lower position, and the position of the component farther from the cooler 30 may be referred to as the upper position. First, the general configuration of each element will be described.

<Semiconductor module>
The semiconductor modules 20 constitute the upper and lower arm circuits 10 described above, i.e., the inverter 5 (power conversion circuit). The power conversion device 4 of this embodiment includes three semiconductor modules 20. One semiconductor module 20 provides one series circuit 12, i.e., one phase of upper and lower arm circuits 10. The multiple semiconductor modules 20 include a semiconductor module 20U that provides the upper and lower arm circuits 10U, a semiconductor module 20V that provides the upper and lower arm circuits 10V, and a semiconductor module 20W that provides the upper and lower arm circuits 10W.

All the semiconductor modules 20 have a common structure. Each semiconductor module 20 includes a semiconductor element 21, a sealing body 22, a signal terminal 23, power supply terminals 24P and 24N, and an output terminal 25.

The semiconductor element 21 is formed by forming a switching element on a semiconductor substrate made of materials such as silicon (Si) or a wide band gap semiconductor with a wider band gap than silicon. The switching element has a vertical structure so that the main current flows in the thickness direction of the semiconductor substrate. Examples of wide band gap semiconductors include silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), and diamond. The semiconductor element 21 is sometimes called a power element, a semiconductor chip, etc.

As an example, the semiconductor element 21 of this embodiment is formed by forming the above-mentioned n-channel MOSFET 13 and FWD 14 on a semiconductor substrate made of SiC. The MOSFET 13 has a vertical structure so that the main current flows in the thickness direction of the semiconductor element 21 (semiconductor substrate). The semiconductor element 21 has main electrodes (not shown) on both sides in the thickness direction of the semiconductor element 21. Specifically, as main electrodes of the switching element, it has a source electrode on the front side and a drain electrode on the back side. The source electrode is formed on a part of the front side. The drain electrode is formed on almost the entire back side.

The main current flows between the drain electrode and the source electrode. The semiconductor element 21 has a pad (not shown) that is a signal electrode on the surface where the source electrode is formed. The semiconductor element 21 is arranged so that its plate thickness direction is approximately parallel to the Z direction. The semiconductor element 21 of this embodiment includes two semiconductor elements 21H that provide switching elements on the high side of the series circuit 12, and two semiconductor elements 21L that provide switching elements on the low side of the series circuit 12. The semiconductor elements 21H and 21L are arranged side by side in the Y direction. The two semiconductor elements 21H are arranged side by side in the X direction. Similarly, the two semiconductor elements 21L are arranged side by side in the X direction.

The four semiconductor elements 21 provide four switching elements for one series circuit 12. The semiconductor module 20 includes semiconductor elements 21 corresponding to the number of switching elements that make up one series circuit 12. When the series circuit 12 includes two switching elements, the semiconductor module 20 includes one each of semiconductor elements 21H and 21L.

The encapsulant 22 encapsulates some of the other elements that make up the semiconductor module 20. The remaining parts of the other elements are exposed outside the encapsulant 22. The encapsulant 22 is made of a material such as resin. The encapsulant 22 is molded by a transfer molding method using a material such as epoxy resin. The encapsulant 22 may also be formed using a gel, for example.

The sealing body 22 has, for example, a generally rectangular shape in plan view. The sealing body 22 has, as surfaces forming its outer periphery, one surface 22a and a back surface 22b that is the surface opposite one surface 22a in the Z direction. One surface 22a and the back surface 22b are, for example, flat surfaces. The sealing body 22 also has side surfaces 22c, 22d, 22e, and 22f that connect one surface 22a and the back surface 22b. Side surface 22c is the surface opposite side surface 22d in the Y direction. Side surface 22e is the surface opposite side surface 22f in the X direction.

The signal terminal 23 is an external connection terminal electrically connected to a pad of the semiconductor element 21. The signal terminal 23 protrudes to the outside from the sealing body 22. For example, the signal terminal 23 connected to the pad of the semiconductor element 21H protrudes from the side surface 22c of the sealing body 22. The signal terminal 23 connected to the pad of the semiconductor element 21L protrudes from the side surface 22d of the sealing body 22. The signal terminal 23 bends outside the sealing body 22 and extends in a direction away from the cooler 30, that is, upward. The signal terminal 23 is roughly L-shaped.

The power supply terminals 24P, 24N and the output terminal 25 are external connection terminals electrically connected to the main electrodes of the semiconductor element 21. Such external connection terminals are sometimes called main terminals. The power supply terminal 24P is electrically connected to the drain electrode of the semiconductor element 21H. The power supply terminal 24N is electrically connected to the source electrode of the semiconductor element 21L. The power supply terminal 24P is sometimes called a P terminal, a high potential power supply terminal, a positive terminal, etc. The power supply terminal 24N is sometimes called an N terminal, a low potential power supply terminal, a negative terminal, etc. The power supply terminals 24P, 24N are electrically connected to the smoothing capacitor 6. The power supply terminals 24P, 24N protrude to the outside from the side surface 22c of the sealing body 22. The protruding portions of the power supply terminals 24P, 24N are arranged side by side in the X direction.

The output terminal 25 is electrically connected to the connection point between the source electrode of the semiconductor element 21H and the drain electrode of the semiconductor element 21L, i.e., the connection point (midpoint) of the series circuit 12. The output terminal 25 protrudes to the outside from the side surface 22d of the sealing body 22. The output terminal 25 may be called an O terminal, an output terminal, an AC terminal, etc. The output terminal 25 is connected to the corresponding winding 3a of the motor generator 3, for example, via a bus bar (not shown). The external connection terminal does not protrude from the side surfaces 22e, 22f of the sealing body 22.

The semiconductor module 20 may include wiring members in addition to the elements described above. The wiring members provide a wiring function that electrically connects the main electrodes and main terminals of the semiconductor element 21. The wiring members provide a heat dissipation function that dissipates heat from the semiconductor element 21. The wiring members are arranged, for example, to sandwich the semiconductor element 21 in the Z direction. As the wiring members, a substrate having metal bodies arranged on both sides of an insulating base material may be used, or a heat sink, which is a metal member, may be adopted. The heat sink is provided, for example, as a part of the lead frame. A part of the wiring members may be exposed from at least one of the first surface 22a and the back surface 22b of the sealing body 22. This can improve heat dissipation.

The semiconductor module 20 is placed on the base plate 331 so that the back surface 22b faces the base plate 331 of the heat dissipation member 33 described below. If necessary, an electrical insulating member such as a ceramic plate may be placed between the semiconductor module 20 and the base plate 331, or a thermally conductive member such as a TIM may be placed. TIM is an abbreviation for Thermal Interface Material.

As shown in FIG. 2, the three semiconductor modules 20 are lined up in the X direction. That is, the multiple semiconductor modules 20 are arranged side by side along the X direction. The three semiconductor modules 20 are lined up, for example, in the order of semiconductor module 20U, semiconductor module 20V, and semiconductor module 20W. In the X direction, the side faces of adjacent semiconductor modules 20 face each other with a predetermined distance between them. Specifically, side face 22f of semiconductor module 20U faces side face 22e of semiconductor module 20V, and side face 22f of semiconductor module 20V faces side face 22e of semiconductor module 20W.

<Lower cooler>
The cooler 30 cools the semiconductor module 20 from the rear surface 22b side. The cooler 30 is disposed below the semiconductor module 20. The cooler 30 includes a case 31. The case 31 defines a flow path 32 through which the coolant 80 flows. The case 31 is formed using a metal material such as aluminum. The case 31 is formed using a material with higher rigidity than the heat dissipation member 33 described below. As an example, the case 31 in this embodiment is formed using ADC12, which is an AlSiCu alloy.

The flow paths 32 are arranged to overlap at least a portion of each of the semiconductor modules 20 in a planar view so as to effectively cool the semiconductor modules 20. As an example, the flow paths 32 in this embodiment are arranged to enclose most of each of the semiconductor modules 20 in a planar view. The flow paths 32 extend along the arrangement direction of the three semiconductor modules 20, that is, along the X direction. Note that the refrigerant 80 may be, for example, a refrigerant that changes phase, such as water or ammonia, or a refrigerant that does not change phase, such as an ethylene glycol-based refrigerant.

The case 31 has an opening 311 at a position overlapping the semiconductor module 20 in a plan view. The opening 311 is provided in the wall that defines the flow path 32 and faces the semiconductor module 20. The opening 311 penetrates the facing wall. The opening 311 has, for example, a substantially rectangular shape in plan view with the X direction as its longitudinal direction. A heat dissipation member 33 is arranged in the opening 311 of the case 31.

The heat dissipation member 33 has a base plate 331 and a number of pin fins 332. The heat dissipation member 33 is formed using a metal material with better thermal conductivity than the case 31, for example an aluminum alloy with excellent thermal conductivity. As an example, the heat dissipation member 33 in this embodiment is formed using A6063, which is an AlMgSi alloy. The heat dissipation member 33 is arranged so as to overlap the semiconductor module 20 in a plan view.

The base plate 331 is arranged so as to close the opening 311 of the case 31. The base plate 331 has, for example, a generally rectangular shape in plan view with the longitudinal direction being the X direction. The peripheral edge of the base plate 331 is liquid-tightly joined to the edge of the opening on the outer surface of the case 31 by friction stir welding or the like. This makes it possible to prevent the refrigerant 80 from leaking out of the flow path 32 through the opening 311. The base plate 331 and the case 31 define the flow path 32. The seal portion 34, which is the joint between the base plate 331 and the case 31, provides a liquid-tight seal.

The pin fins 332 are pin-shaped fins as shown in Figures 3, 4, and 5. The pin fins 332 may be provided integrally with the base plate 331, or may be provided integrally by joining. The pin fins 332 are disposed in the flow path 32 through the opening 311. The pin fins 332 protrude from the base plate 331. The multiple pin fins 332 extend in the Z direction from one surface of the base plate 331. The pin fins 332 have a predetermined length in the Z direction. The pin fins 332 have a substantially circular or elliptical shape in plan view. The multiple pin fins 332 are provided at a predetermined pitch in the Y direction. The multiple pin fins 332 are provided at a predetermined pitch in the X direction.

The case 31 of the cooler 30 may be provided as a stand-alone case 31, or may be provided as a part of a housing that houses other elements of the power conversion device 4. As an example, the case 31 of this embodiment is provided as a part of the housing 35. The case 31 is provided as a part of the bottom wall 351 of the housing 35. The housing 35 has an opening to house other elements. The housing 35 has a bottom wall 351 and a side wall 352 that is connected to the bottom wall 351 and defines a housing space together with the bottom wall 351. As an example, the housing 35 of this embodiment is box-shaped with one side open. The housing 35 is approximately rectangular in plan view in the Z direction. The semiconductor module 20, the cooler 40, the circuit board 70, etc. are arranged in the housing space of the housing 35.

The housing 35 is fitted with an inlet pipe 36 for supplying refrigerant to the coolers 30, 40, and a discharge pipe 37 for discharging the refrigerant from the coolers 30, 40. The inlet pipe 36 and the discharge pipe 37 are inserted through corresponding through holes (not shown) and are arranged inside and outside the housing 35. The mounting positions of the inlet pipe 36 and the discharge pipe 37 are not particularly limited. They may be mounted on the bottom wall 351 or the side wall 352. The inlet pipe 36 and the discharge pipe 37 may be mounted on a common surface or on different surfaces. As an example, in this embodiment, the inlet pipe 36 is mounted on one of the walls facing each other in the X direction, and the discharge pipe 37 is mounted on the other wall.

The housing 35 including the case 31 may be made of a single member, or may be made of a combination of multiple members. The bottom wall 351 of the housing 35 may be made of a combination of multiple members in one part, and a single member in the other part. The power conversion device 4 may be provided with a cover (lid) (not shown) that closes the opening of the housing 35.

<Upper stage cooler>
The cooler 40 cools the semiconductor module 20 from the one surface 22a side. The cooler 40 is disposed above the semiconductor module 20. The cooler 40 is disposed on the one surface 22a of the semiconductor module 20. An electrical insulating member such as a ceramic plate may be disposed between the cooler 40 and the semiconductor module 20 as necessary, or a thermally conductive member such as a TIM may be disposed. The cooler 40 cools the semiconductor module 20 from the opposite side to the cooler 30 in the Z direction.

The cooler 40 includes a case 41. The case 41 defines a flow path 42 through which the refrigerant 80 flows. The case 41 is formed using a metal material such as aluminum. In the Z direction, the cooler 40 is thinner than the cooler 30. The cooler 40 is, for example, a tubular body with a flat shape overall. The cooler 40 is configured to have a flow path inside by using, for example, a pair of plates (thin metal plates). At least one of the pair of plates is processed into a shape that expands in the Z direction by press processing. Thereafter, the outer peripheral edges of the pair of plates are fixed to each other by crimping or the like, and are joined to each other around the entire circumference by brazing or the like. This forms a flow path 42 through which the refrigerant 80 can flow between the pair of plates.

The flow paths 42 are arranged to overlap at least a portion of each of the semiconductor modules 20 in a planar view so as to effectively cool the semiconductor modules 20. In this embodiment, the flow paths 42 are arranged to overlap most of each of the semiconductor modules 20 in a planar view. The flow paths 42 extend along the arrangement direction of the three semiconductor modules 20, that is, the X direction. The flow paths 42 cross the three semiconductor modules 20 in the X direction. In a planar view, the flow paths 42 are contained within the flow paths 32. The extension length of the flow paths 42 is shorter than the extension length of the flow paths 32.

The cooler 40 may include fins. As an example, the cooler 40 of this embodiment includes fins 43. The fins 43 are arranged inside a case 41 made up of a pair of plates, i.e., in the flow path 42. The fins 43 are arranged so as to overlap the semiconductor module 20 in a plan view. The fins 43 are, for example, wave-shaped fins. The fins 43 have a predetermined height in the Z direction. The height of the fins 43 is less than the height (length) of the pin fins 332. Although not shown in the figure, the multiple fins 43 are arranged at a predetermined pitch in the Y direction.

The cooler 40 is stacked on the cooler 30 via the semiconductor module 20. The cooler 40 may be pressed in the Z direction from the side opposite the semiconductor module 20 by a pressure member (not shown). The pressure maintains good thermal conduction between the cooler 40 and the semiconductor module 20, and between the semiconductor module 20 and the cooler 30. The pressure member may include, for example, a pressure plate and an elastic member. The elastic member is, for example, a material that generates pressure by elastic deformation such as rubber, or a metal spring. The elastic member is disposed between the pressure plate and the cooler 40 in the Z direction. The elastic member is elastically deformed by fixing the pressure plate to a predetermined position relative to the housing 35. The cooler 40 and the semiconductor module 20 are pressed against the cooler 30 by the reaction force of the elastic deformation.

<Connecting pipe>
The connecting pipes 50 and 60 connect the cooler 30 and the cooler 40. The connecting pipe 50 supplies the refrigerant 80 to the flow paths to which the inlet pipe 36 is not connected. The connecting pipe 60 discharges the refrigerant 80 from the flow paths to which the outlet pipe 37 is not connected. As an example, the connecting pipe 50 in this embodiment supplies a portion of the refrigerant 80 supplied to the cooler 30 through the inlet pipe 36 to the cooler 40. The connecting pipe 60 discharges the refrigerant 80 that has flowed through the cooler 40 from the outlet pipe 37 via the cooler 30.

The connecting pipe 50 has a connecting flow passage 51 that communicates with the flow passages 32 and 42. The connecting pipe 60 has a connecting flow passage 61 that communicates with the flow passages 32 and 42. The connecting flow passages 51 and 61 extend in the Z direction. One end of each of the connecting flow passages 51 and 61 communicates with the flow passage 32, and the other end communicates with the flow passage 42. The connecting pipe 50 is connected to the vicinity of one end of the cooler 40 in the X direction. The connecting pipe 60 is connected to the vicinity of the other end of the cooler 40. Reference numeral 52 in FIG. 4 denotes a seal portion around the connecting pipe 50 provided on the cooler 30. Reference numeral 62 denotes a seal portion around the connecting pipe 60 provided on the cooler 30. The seal portions 52 and 62 are provided by, for example, grommets.

The connecting pipe 50 is disposed between the connection position of the inlet pipe 36 and the cooler 30 and the heat dissipation member 33. The connecting pipe 60 is disposed between the heat dissipation member 33 and the connection position of the outlet pipe 37 and the cooler 30. A part of the refrigerant 80 supplied from the inlet pipe 36 flows through the flow path 32 and is discharged from the outlet pipe 37. Another part of the refrigerant 80 is supplied to the flow path 42 through the flow path 32 and the connecting flow path 51 of the connecting pipe 50. The refrigerant 80 that has flowed through the flow path 42 flows into the flow path 32 through the connecting flow path 61 of the connecting pipe 60 and is discharged from the outlet pipe 37. The connecting pipes 50 and 60, together with the cooler 40, provide a bypass path for the refrigerant 80.

As an example, in the two-stage cooler of this embodiment, the flow rate of the refrigerant 80 flowing through the flow path 32 is greater than the flow rate of the refrigerant 80 flowing through the flow path 42. The flow path 32 is a main flow path, and the flow path 42 is a sub-flow path branched off from the flow path 32. The flow rate of the flow path 32 that passes through the branch point by the connecting pipe 50 is greater than the flow rate of the refrigerant 80 flowing through the flow path 42. The cross-sectional area of the flow path 32 is greater than the cross-sectional area of the flow path 42. In the Z direction, the thickness (height) of the cooler 30 is greater than the thickness of the cooler 40. The flow path 42, which is a sub-flow path, is branched off from the flow path 32, which is the main flow path, via the connecting flow paths 51 and 61. The cross-sectional area of each of the connecting flow paths 51 and 61 is smaller than the cross-sectional area of the flow path 32. The cross-sectional area of each flow path is the area of a cross section perpendicular to the extension direction of the flow path, that is, the flow direction of the refrigerant. In addition, the water flow resistance of the connecting flow paths 51 and 61 is smaller than the water flow resistance of the flow path 42.

<Circuit board>
Although not shown, the circuit board 70 includes a wiring board in which wiring is arranged on an insulating base material such as resin, electronic components mounted on the wiring board, connectors, etc. The mounted electronic components and wiring form a circuit. The drive circuit 7 described above is formed on the circuit board 70.

The circuit board 70 is arranged so as to overlap the semiconductor modules 20 when viewed in a plane in the Z direction. The circuit board 70 is arranged above the three semiconductor modules 20. The signal terminals 23 of the three semiconductor modules 20 are mounted on the circuit board 70. As an example, the circuit board 70 in this embodiment is arranged inside the housing 35. The circuit board 70 is located above the cooler 40.

<Base plate placement>
As described above, the base plate 331 of the heat dissipation member 33 is disposed so as to close the opening 311 of the case 31. In the X direction, the length L1 of the base plate 331 is shorter than the length L2 between the outer end of the connecting pipe 50 and the outer end of the connecting pipe 60. As an example, the length L1 of the base plate 331 in this embodiment is shorter than the length between the centers of the connecting pipes 50, 60 (connecting flow paths 51, 61) in the X direction. The length L1 of the base plate 331 is shorter than the length between the inner end of the connecting pipe 50 and the inner end of the connecting pipe 60. As shown in FIG. 4, the seal portion 34 between the base plate 331 and the case 31 is located inside the seal portions 52, 62 between the case 31 and the connecting pipes 50, 60.

Summary of the First Embodiment
FIG. 6 shows a reference example. FIG. 6 corresponds to FIG. 4. In the reference example, the suffix r is added to the reference symbols of the elements related to this embodiment. The power converter 4r of the reference example also includes coolers 30r, 40r having a two-stage structure. The case 31r defining the flow path 32r is open on the entire surface facing the semiconductor module 20r. The base plate 331r is a cover that closes the opening of the case 31r. Therefore, in the X direction, which is the arrangement direction of the connecting pipes 50r, 60r, the length L1r of the base plate 331r is longer than the length L2r between the outer end of the connecting pipe 50r and the outer end of the connecting pipe 60r. The other configurations of the power converter 4r are the same as those of the power converter 4 of this embodiment.

As described above, because the base plate 331r is long, there is a risk that the base plate 331r will bend outward due to water pressure, that is, will deform into an outward convex shape. If the base plate 331r bends outward, the gap between the pin fins 332r and the case 31r will become larger, and the amount of refrigerant that passes through without hitting the pin fins 332r will increase, reducing the cooling performance (heat exchange performance) of the cooler 30r. If the base plate 331r deforms, the adhesion between the base plate 331r and the semiconductor module 20r will decrease, and the thermal resistance will increase. As a result, the heat dissipation performance will decrease according to the configuration of the reference example, and the structure in which the heat dissipation member 33r is added to the two- stage cooler 30r, 40r cannot be fully utilized.

According to the power conversion device 4 of this embodiment, in the X direction in which the connecting pipes 50, 60 are arranged, the length L1 of the base plate 331 is shorter than the length L2 between the outer ends of the connecting pipes 50, 60. In this way, since the length of the base plate 331 constituting the heat dissipation member 33 is short, deformation of the base plate 331 due to water pressure, specifically outward bending, can be suppressed. This prevents the gap between the pin fins 332 and the case 31 from expanding, and prevents an increase in the amount of refrigerant 80 that passes through without hitting the pin fins 332. In addition, the adhesion between the base plate 331 and the semiconductor module 20 from decreasing, which prevents an increase in thermal resistance.

As described above, the power converter 4 of this embodiment can suppress the deterioration of heat dissipation. Therefore, the structure in which the heat dissipation member 33 is added to the two- stage coolers 30, 40 can be fully utilized. In other words, a power converter 4 with high heat dissipation properties can be provided. In this embodiment, the cooler 30 corresponds to the first cooler, and the flow path 32 corresponds to the first flow path. The cooler 40 corresponds to the second cooler, and the flow path 42 corresponds to the second flow path. The connecting pipe 50 corresponds to the first connecting portion, and the connecting flow path 51 corresponds to the first connecting flow path. The connecting pipe 60 corresponds to the second connecting portion, and the connecting flow path 61 corresponds to the second connecting flow path.

The base plate 331 (heat dissipation member 33) may be formed using the same material as the case 31, or may be formed using a material different from that of the case 31. As an example, the base plate 331 in this embodiment is formed using a material different from that of the case 31. The thermal conductivity of the base plate 331 is higher than that of the case 31, and the rigidity of the case 31 is higher than that of the base plate 331.

As described above, since the length L1 of the base plate 331 is shorter than the length L2 between the outer ends of the connecting pipes 50 and 60, deformation of the base plate 331 due to water pressure can be suppressed even if the rigidity of the base plate 331 is low. Since deformation is suppressed and the thermal conductivity of the base plate 331 is high, heat dissipation can be further improved.

<Modification>
The arrangement order of the three semiconductor modules 20U, 20V, and 20W is not limited to the above example. The semiconductor module 20U or the semiconductor module 20W may be disposed in the middle.

Although an example has been shown in which the inlet pipe 36 and the outlet pipe 37 are connected to the cooler 30, this is not limiting. The inlet pipe 36 and the outlet pipe 37 may also be connected to the cooler 40. In this case, a portion of the refrigerant 80 flows from the flow path 42 through the connecting pipe 50 to the flow path 32 of the cooler 30. The refrigerant 80 that has flowed through the flow path 32 returns to the flow path 42 through the connecting pipe 60 and is discharged.

Although an example has been shown in which the cooler 30 includes the base plate 331 and the pin fins 332, the cooler 40 may also include a base plate and pin fins. The length of the base plate included in the cooler 40 may be shorter than the length L2 between the outer ends of the connecting pipes 50, 60. The case 41 of the cooler 40 has an opening on the surface facing the semiconductor module 20, and the base plate is arranged to close this opening. In this case, the cooler 40 corresponds to the first cooler, and the flow path 42 corresponds to the first flow path. Also, the cooler 30 corresponds to the second cooler, and the flow path 32 corresponds to the second flow path.

Second Embodiment
This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used. In the preceding embodiment, the length of the base plate constituting the heat dissipation member is shorter than the length between the outer ends of the connecting pipe. In addition, the first flow path may include a flow straightening chamber.

FIG. 7 is a plan view showing the power conversion device 4 according to this embodiment. FIG. 7 corresponds to FIG. 2. For convenience, signal terminals and circuit boards are also omitted in FIG. 7. The white arrows in FIG. 7 indicate the direction of refrigerant flow. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. FIG. 8 corresponds to FIG. 4. Part of the housing and the circuit board are also omitted in FIG. 7. The solid arrows in FIG. 7 indicate the flow of refrigerant.

The cooler 30 of this embodiment has a wall portion 38. The wall portion 38 protrudes from the inner wall of the case 31. The wall portion 38 may be provided integrally with the case 31, or may be provided integrally by joining. The wall portion 38 is provided between the connecting pipe 50 and the base plate 331 in the X direction. The wall portion 38 locally narrows the flow path 32. As an example, the wall portion 38 of this embodiment is connected to the bottom surface and both side surfaces in the Y direction of the inner wall of the case 31. The wall portion 38 is not connected to the top surface of the inner wall of the case 31. Between the wall portion 38 and the top surface of the inner wall of the case 31, there is a gap through which the refrigerant 80 can flow. The wall portion 38 divides the flow path 32 into two regions.

The flow path 32 has a heat exchange chamber 321 and a straightening chamber 322 as regions partitioned by the wall portion 38. The heat exchange chamber 321 is a region downstream of the wall portion 38 in the longitudinal direction of the flow path 32, i.e., in the X direction. The heat exchange chamber 321 is a region closer to the exhaust pipe 37 than the wall portion 38. The pin fins 332 of the heat dissipation member 33 are arranged in the heat exchange chamber 321. The straightening chamber 322 is a region upstream of the wall portion 38 in the X direction. The straightening chamber 322 is a region closer to the inlet pipe 36 than the wall portion 38. In the X direction, the length of the straightening chamber 322 is shorter than the length of the heat exchange chamber 321. As an example, the straightening chamber 322 in this embodiment is smaller than the heat exchange chamber 321. The volume of the straightening chamber 322 is smaller than the volume of the heat exchange chamber 321. The straightening chamber 322 is a small room.

The connecting passage 51 of the connecting pipe 50, which provides a refrigerant inlet for the bypass path, is connected to the rectification chamber 322. The connecting passage 61 of the connecting pipe 60, which provides a refrigerant outlet for the bypass path, is connected to the heat exchange chamber 321. The heat exchange chamber 321 and the rectification chamber 322 are connected to each other through a gap above the wall portion 38. The other configurations are the same as those described in the preceding embodiment.

<Summary of the Second Embodiment>
According to the power conversion device 4 of the present embodiment, it is possible to achieve the same effects as those of the preceding embodiment. Furthermore, the cooler 30 of the power conversion device 4 has a wall portion 38 protruding from the inner wall of the case 31. This wall portion 38 divides the flow path 32 into a heat exchange chamber 321 in which pin fins 332 are arranged, and a rectification chamber 322. The rectification chamber 322 is an area upstream of the wall portion 38, and is connected to the connecting flow path 51 of the connecting pipe 50.

In this way, the power conversion device 4 has the rectification chamber 322 as a front chamber of the heat exchange chamber 321 and the flow path 42. The rectification chamber 322 can receive and rectify the pulsation caused by the water pump. This makes it possible to suppress variations in the cooling effect. In other words, it is possible to improve heat dissipation. The cooler 30 corresponds to the first cooler, and the flow path 32 corresponds to the first flow path. The cooler 40 corresponds to the second cooler, and the flow path 42 corresponds to the second flow path. The connecting pipe 50 corresponds to the first connecting part, and the connecting flow path 51 corresponds to the first connecting flow path. The connecting pipe 60 corresponds to the second connecting part, and the connecting flow path 61 corresponds to the second connecting flow path.

<Modification>
In the inner wall of the case 31, the surface to which the wall portion 38 is connected is not particularly limited. The wall portion 38 may be connected only to the bottom surface, only to the side surface, only to the top surface, or both to the side surface and the top surface.

The cooler 30 may have a wall portion provided between the connecting pipe 60 and the base plate 331 in the X direction. This wall portion divides the heat exchange chamber 321 into an area where the pin fins 332 are arranged and an area where the connecting pipe 60 communicates.

In a configuration in which the inlet pipe 36 and the outlet pipe 37 are connected to the cooler 40, a wall may be provided in the cooler 40 to divide the flow path 42 into a heat exchange chamber and a flow straightening chamber. In this case, the cooler 40 corresponds to the first cooler, and the flow path 42 corresponds to the first flow path. The cooler 30 corresponds to the second cooler, and the flow path 32 corresponds to the second flow path.

Other Embodiments
The disclosure in this specification and drawings, etc. is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and/or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and/or elements of the embodiments. The disclosure includes the substitution or combination of parts and/or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

The disclosure in the specification and drawings, etc. is not limited by the claims. The disclosure in the specification and drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and extensive technical ideas than the technical ideas described in the claims. Therefore, a variety of technical ideas can be extracted from the disclosure in the specification and drawings, etc., without being bound by the claims.

When an element or phase is referred to as being "on," "coupled," "connected," or "coupled," it may be directly on, coupled, connected, or coupled to another element or phase, and there may be intervening elements or phases present. In contrast, when an element is referred to as being "directly on," "directly coupled," "directly connected," or "directly coupled" to another element or phase, there are no intervening elements or phases present. Other words used to describe relationships between elements should be construed in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Spatially relative terms such as "inside," "outside," "back," "bottom," "low," "top," "top," and the like are utilized herein for ease of description to describe the relationship of one element or feature to other elements or features as depicted in the figures. Spatially relative terms may be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figures is turned over, elements described as "below" or "directly below" other elements or features would be oriented "above" the other elements or features. Thus, the term "bottom" can encompass both an orientation of top and bottom. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used in this specification would be interpreted accordingly.

The vehicle drive system 1 is not limited to the configuration described above. For example, although an example with one motor generator 3 has been shown, the present invention is not limited to this. Multiple motor generators may be provided.

Although an example has been shown in which the power conversion device 4 includes an inverter 5 as a power conversion circuit, this is not limiting. For example, the power conversion device 4 may be configured to include multiple inverters. The power conversion device 4 may be configured to include at least one inverter and a converter.

The number of semiconductor modules 20 is not limited to the above example. For example, one semiconductor module 20 may provide six arms 10H, 10L. One semiconductor module 20 may provide one arm, i.e., one upper arm 10H or one lower arm 10L.

Claims (3)

1. A semiconductor module (20) constituting a power conversion circuit (5);
   a first cooler (30) having a first flow path (32) and cooling the semiconductor module;
   a second cooler (40) having a second flow path (42) and cooling the semiconductor module from the opposite side to the first cooler;
   a first connecting portion (50) having a first connecting flow path (51) communicating with the first flow path and the second flow path;
   a second connecting portion (60) having a second connecting flow path (61) communicating with the first flow path and the second flow path and providing a bypass path for a part of the refrigerant together with the first connecting portion,
   The first cooler includes a case (31) that defines the first flow path and has an opening at a portion that overlaps with the semiconductor module, a base plate (331) that is disposed on the case so as to cover the opening, and pin fins (332) that extend from the base plate into the first flow path,
   A power conversion device, wherein a length of the base plate in an arrangement direction of the first connecting portion and the second connecting portion is shorter than a length between outer ends of the first connecting portion and the second connecting portion.
2. the thermal conductivity of the base plate is higher than the thermal conductivity of the case;
   The power conversion device according to claim 1 , wherein the rigidity of the case is higher than the rigidity of the base plate.
3. The first connection portion provides a refrigerant inlet for the bypass path,
   The second connection portion provides a refrigerant outlet for the bypass path,
   3. The power conversion device according to claim 1 or claim 2, wherein the first cooler is provided between the first connecting portion and the base plate in the arrangement direction, and has a wall portion (38) protruding from an inner wall of the case, a heat exchange chamber (321) which is a region of the first flow path downstream of the wall portion and in which the pin fins are arranged, and a straightening chamber (322) which is a region upstream of the wall portion and to which the first flow path of the first connecting portion is connected.

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