Power conversion device

A refrigerant flow channel includes a first flow channel extending in a first direction and a plurality of first branching flow channels extending in a second direction by branching from the first flow channel. Three element arrays corresponding to a first motor for driving and three element arrays corresponding to a second motor for power generation are respectively disposed side by side in the first direction on a mounting surface. The element array of the first motor in each phase and the element array of the second motor in each phase face each other in the second direction, and are disposed at positions overlapping the first branching flow channel in a plan view. The element array of the first motor is located on an upstream side of the first branching flow channel with respect to the element array of the second motor.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on Japanese Patent Application No. 2017-202664, filed Oct. 19, 2017, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a power conversion device.

Description of Related Art

Hitherto, as shown inFIG. 7, there has been known a semiconductor device110including a circuit element portion101constituted by a plurality of semiconductor elements, a circuit substrate102on which a plurality of circuit element portions101are mounted, and a cooler103which is connected to the circuit substrate102(see, for example, Japanese Unexamined Patent Application, First Publication No. 2015-079819). A refrigerant flow channel111is formed in the cooler103along a longitudinal direction (array direction of the circuit element portion101). The circuit element portion101is cooled by heat exchange between a refrigerant flowing through the refrigerant flow channel111and the circuit element portion.

SUMMARY OF THE INVENTION

In the semiconductor device110according to the above related art, a refrigerant cooling a circuit element portion101on a side (that is, upstream side) close to an inlet112of the refrigerant flow channel111cools a circuit element portion101on a side (that is, downstream side) close to an outlet113of the refrigerant flow channel111. Therefore, in a case where the number of circuit element portions101arrayed along the refrigerant flow channel111increases, the temperature gradient of a refrigerant becomes larger between the upstream side and the downstream side of the refrigerant flow channel111, and thus there is the possibility of an increase in the change of cooling performance caused by the array positions of the circuit element portions101. In a case where the temperature gradient of a refrigerant increases between the upstream side and the downstream side of the refrigerant flow channel111, it becomes difficult to cool the circuit element portions101from the upstream side of the refrigerant flow channel111toward the downstream side thereof. As a result, it becomes difficult to uniformly cool each of the circuit element portions101.

In addition, in a case where a plurality of circuit element portions101configure an electrification switching circuit for a motor of a plurality of phases, the arraying of circuit element portions101having different phases along the refrigerant flow channel111causes a change in cooling performance among a plurality of phases of one motor. As a result, it becomes difficult to uniformly cool the circuit element portions101of each phase.

An aspect of the present invention is contrived in view of such circumstances, and an object thereof is to provide a power conversion device which makes it possible to cool a plurality of elements uniformly and efficiently, and to suppress an increase in a difference in cooling performance between the plurality of elements.

In order to solve the above problem and achieve such an object, the present invention adopts the following aspects.

(1) According to an aspect of the present invention, there is provided a power conversion device including: a heat dissipation portion having a refrigerant flow channel through which a refrigerant circulates and a mounting surface; a plurality of first element arrays in which element arrays including a high side arm element and a low side arm element delivering power to and from a first motor capable of a power-running operation using power supplied from a power storage device are disposed side by side in a first direction on the mounting surface according to a plurality of phases of the first motor; and a plurality of second element arrays in which element arrays including a high side arm element and a low side arm element delivering power to and from a second motor capable of generating power for running of the first motor are disposed side by side in the first direction on the mounting surface according to a plurality of phases of the second motor, wherein the plurality of first element arrays and the plurality of second element arrays are disposed at positions facing each other in a second direction intersecting the first direction, the refrigerant flow channel includes a first flow channel extending in the first direction, and a plurality of first branching flow channels that branch from the first flow channel so as to correspond to each phase of the plurality of first element arrays and the plurality of second element arrays, and extend in the second direction at positions overlapping the first element arrays and the second element arrays in a plan view seen from a third direction orthogonal to the first direction and the second direction, and in each of the first branching flow channels, the plurality of first element arrays are located on an upstream side of the first branching flow channel in the second direction with respect to the plurality of second element arrays.

(2) In the above (1), the high side arm element and the low side arm element in the plurality of first element arrays and the plurality of second element arrays may be disposed side by side in the first direction.

(3) In the above (1) or (2), the power conversion device may further include a voltage converter which is electrically connected to the plurality of first element arrays or the plurality of second element arrays, a high side arm element and a low side arm element configuring the voltage converter may be disposed side by side in the second direction on the mounting surface, the refrigerant flow channel may further include a second branching flow channel that branches from the first flow channel, and extends in the second direction at a position overlapping the high side arm element and the low side arm element of the voltage converter in the plan view, and the low side arm element of the voltage converter may be located on an upstream side of the second branching flow channel in the second direction with respect to the high side arm element of the voltage converter.

According to the above (1), as compared with a case where a plurality of power conversion circuit portions are disposed on a refrigerant flow channel of one system, it is possible to suppress an increase in the temperature gradient of a refrigerant between the upstream side and the downstream side of the refrigerant flow channel associated with an increase in the number of power conversion circuit portions. In addition, since a branching flow channel is provided for each phase in the first motor and the second motor, it is possible to suppress a change in cooling performance among a plurality of phases of each motor, and to make cooling performance between a plurality of phases uniform.

Here, the first element array corresponding to the first motor has more of a tendency to generate heat than the second element array corresponding to the second motor. Therefore, in each of the first branching flow channels, the first element array is disposed further upstream than the second element array, and thus a difference in temperature between the refrigerant and the first element array has a tendency to be secured. Thereby, it is possible to uniformly and efficiently cool the first element array and the second element array, and to suppress an increase in a difference in cooling performance between a plurality of element arrays.

In a case of the above (2), in each of the first element array and the second element array in each branching flow channel, the high side arm element and the low side arm element are disposed side by side in the first direction, and thus it is possible to suppress an increase in a difference in cooling performance between the high side arm element and the low side arm element.

In a case of the above (3), in a case where a voltage conversion circuit boosts a voltage from the power source side to a plurality of first element arrays, heat generation due to switching of the low side arm element becomes larger than that of the high side arm element. In addition, in a case where the voltage conversion circuit steps down a voltage from a plurality of second element arrays to the power source side, heat generation due to switching of the high side arm element becomes larger than that of the low side arm element. However, in a case where the output current of the power source is larger than the input current thereof when voltage boost and voltage step down are compared with each other, heat generation of the low side arm element becomes larger than that of the high side arm element.

In the second branching flow channel, since the low side arm element is disposed on the upstream side of the high side arm element, it is possible to secure a difference in temperature between the refrigerant and the low side arm element. As a result, it is possible to efficiently cool the low side arm element. Thereby, it is possible to uniformly and efficiently cool the high side arm element and the low side arm element of the voltage conversion circuit, and to suppress an increase in a difference in cooling performance between the high side arm element and the low side arm element.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of a power conversion device of the present invention will be described with reference to the accompanying drawings.

The power conversion device according to the present embodiment controls power deliver between a motor and a battery. For example, the power conversion device is mounted in an electromotive vehicle or the like. The electromotive vehicle is an electric automobile, a hybrid vehicle, a fuel cell vehicle, or the like. The electric automobile is driven using a battery as a motive power source. The hybrid vehicle is driven using a battery and an internal-combustion engine as a motive power source. The fuel cell vehicle is driven using a fuel cell as a driving source.

FIG. 1is a plan view schematically illustrating a configuration of a power conversion device1according to an embodiment of the present invention.

FIG. 2is an exploded perspective view schematically illustrating a configuration of a power conversion device1according to an embodiment of the present invention.FIG. 3is a diagram illustrating a configuration of a portion of a vehicle10in which the power conversion device1according to an embodiment of the present invention is mounted.FIG. 4is a plan view schematically illustrating a heat dissipation case64of a first heat dissipation portion61aand a plurality of element arrays PU1, PV1, PW1, PU2, PV2, and PW2of a power module21in the power conversion device1according to the embodiment of the present invention.

As shown inFIG. 3, the vehicle10includes a battery11(BATT), a first motor12(MOT) for traveling driving, and a second motor13(GEN) for power generation, in addition to the power conversion device1.

The battery11includes a battery case and a plurality of battery modules received within the battery case. The battery module includes a plurality of battery cells connected in series to each other. The battery11includes a positive electrode terminal PB and a negative electrode terminal NB which are connected to a direct-current connector1aof the power conversion device1. The positive electrode terminal PB and the negative electrode terminal NB are connected to a positive electrode end and a negative electrode end of the plurality of battery modules connected in series to each other within the battery case.

The first motor12generates a rotary driving force (power-running operation) using power which is supplied from the battery11. The second motor13generates generating power using a rotary driving force which is input to a rotary shaft. Here, the second motor13is configured to have the rotary dynamic force of an internal-combustion engine transmitted thereto. For example, each of the first motor12and the second motor13is a three-phase AC brushless DC motor. Three phases are a U-phase, a V-phase, and a W-phase. Each of the first motor12and the second motor13is an inner rotor type. Each of the motors12and13includes a rotor having a field permanent magnet and a stator having a three-phase stator winding for generating a rotating magnetic field that rotates the rotor. The three-phase stator winding of the first motor12is connected to a first three-phase connector1bof the power conversion device1. The three-phase stator winding of the second motor13is connected to a second three-phase connector1cof the power conversion device1.

The power conversion device1includes a power module21, a reactor22, a capacitor unit23, a resistor24, a first current sensor25, a second current sensor26, a third current sensor27, an electronic control unit28(MOT GEN ECU), and a gate drive unit29(G/D VCU ECU).

The power module21includes a first power conversion circuit portion31, a second power conversion circuit portion32, and a third power conversion circuit portion33. The first power conversion circuit portion31is connected to the three-phase stator winding of the first motor12by the first three-phase connector1b. The first power conversion circuit portion31converts direct-current power which is input from the battery11through the third power conversion circuit portion33into three-phase AC power. The second power conversion circuit portion32is connected to the three-phase stator winding of the second motor13by the second three-phase connector1c. The second power conversion circuit portion32converts three-phase AC power which is input from the second motor13into direct-current power. The direct-current power converted by the second power conversion circuit portion32can be supplied to at least one of the battery11and the first power conversion circuit portion31.

Each of the first power conversion circuit portion31and the second power conversion circuit portion32includes a bridge circuit formed by a plurality of switching elements which are bridge-connected to each other. For example, the switching element is a transistor such as an insulated gate bipolar transistor (IGBT) or a metal oxide semi-conductor field effect transistor (MOSFET). For example, in the bridge circuit, high side arm and low side arm U-phase transistors UH and UL forming a pair, high side arm and low side arm V-phase transistors VH and VL forming a pair, and high side arm and low side arm W-phase transistors WH and WL forming a pair are bridge-connected to each other. In the present embodiment, in each of the U, V, and W-phases, high side arm and low side arm transistors (for example, U-phase high side arm transistor UH and U-phase low side arm transistor UL) are disposed next to each other in a first direction D1.

Each of the transistors UH, VH, and WH of a high side arm configures a high side arm by its collector being connected to a positive electrode terminal PI. In each phase, each positive electrode terminal PI of a high side arm is connected to a positive electrode bus bar50p.

Each of the transistors UL, VL, and WL of a low side arm configures a low side arm by its emitter being connected to a negative electrode terminal NI. In each phase, each negative electrode terminal NI of a low side arm is connected to a negative electrode bus bar50n.

As shown inFIGS. 1 and 3, the emitter of each of the transistors UH, VH, and WH of a high side arm in each phase is connected to the collector of each of the transistors UL, VL, and WL of a low side arm at a connection point TI.

The connection point TI of the first power conversion circuit portion31in each phase is connected to a first input and output terminal Q1by a first bus bar51. The first input and output terminal Q1is connected to the first three-phase connector1b. The connection point TI of the first power conversion circuit portion31in each phase is connected to the stator winding of the first motor12in each phase through the first bus bar51, the first input and output terminal Q1, and the first three-phase connector1b.

The connection point TI of the second power conversion circuit portion32in each phase is connected to a second input and output terminal Q2by a second bus bar52. The second input and output terminal Q2is connected to the second three-phase connector1c. The connection point TI of the second power conversion circuit portion32in each phase is connected to the stator winding of the second motor13in each phase through the second bus bar52, the second input and output terminal Q2, and the second three-phase connector1c. The bridge circuit includes a diode which is connected between the collector and the emitter of each of the transistors UH, UL, VH, VL, WH, and WL so as to have a forward direction from the emitter toward the collector.

Each of the first power conversion circuit portion31and the second power conversion circuit portion32switches between the on-state (electrical conduction)/off-state (cutoff) of a transistor pair in each phase, on the basis of a gate signal that is a switching command which is input from the gate drive unit29to the gate of each of the transistors UH, VH, WH, UL, VL, and WL. The first power conversion circuit portion31converts direct-current power which is input from the battery11through the third power conversion circuit portion33into three-phase AC power, and sequentially commutates electrical conduction to the three-phase stator winding of the first motor12, to thereby allow for electrical conduction of an AC U-phase current, a V-phase current, and a W-phase current to the three-phase stator winding. The second power conversion circuit portion32converts three-phase AC power which is output from the three-phase stator winding of the second motor13into direct-current power by on (electrical conduction)/off (cutoff) driving of a transistor pair in each phase synchronized with the rotation of the second motor13.

The third power conversion circuit portion33is a voltage control unit (VCU). The third power conversion circuit portion33includes switching elements of a high side arm and a low side arm forming a pair. For example, the third power conversion circuit portion33includes a first transistor S1of a high side arm and a second transistor S2of a low side arm. The first transistor S1configures a high side arm by its collector being connected to a positive electrode terminal PV. The positive electrode terminal PV of a high side arm is connected to the positive electrode bus bar50p. The second transistor S2configures a low side arm by its emitter being connected to a negative electrode terminal NV. The negative electrode terminal NV of a low side arm is connected to the negative electrode bus bar50n. The emitter of the first transistor S1of a high side arm is connected to the collector of the second transistor S2of a low side arm. The third power conversion circuit portion33includes a diode which is connected between the collector and the emitter of each of the first transistor S1and the second transistor S2so as to have a forward direction from the emitter toward the collector.

A connection point between the first transistor S1of a high side arm and the second transistor S2of a low side arm is connected to the reactor22by a third bus bar53. Both ends of the reactor22are connected to the connection point between the first transistor S1and the second transistor S2, and the positive electrode terminal PB of the battery11. The reactor22includes a coil and a temperature sensor that detects the temperature of the coil. The temperature sensor is connected to the electronic control unit28by a signal line.

The third power conversion circuit portion33switches between the on-state (electrical conduction)/off-state (cutoff) of a transistor pair on the basis of a gate signal that is a switching command which is input from the gate drive unit29to the gate of each of the first transistor S1and the second transistor S2.

The third power conversion circuit portion33alternately switches between, during a boost in voltage, a first state where the second transistor S2is set to be in an on-state (electrical conduction) and the first transistor S1is set to be in an off-state (cutoff), and a second state where the second transistor S2is set to be in an off-state (cutoff) and the first transistor S1is set to be in an on-state (electrical conduction). In the first state, sequentially, a current flows to the positive electrode terminal PB of the battery11, the reactor22, the second transistor S2, and the negative electrode terminal NB of the battery11, the reactor22is DC excited, and magnetic energy is accumulated. In the second state, an electromotive voltage (induced voltage) is generated between both ends of the reactor22so as to prevent a change in magnetic flux due to a current flowing to the reactor22being cut off. An induced voltage caused by the magnetic energy accumulated in the reactor22is superimposed on a battery voltage, and thus a boost voltage higher than a voltage between the terminals of the battery11is applied between the positive electrode terminal PV and the negative electrode terminal NV of the third power conversion circuit portion33.

The third power conversion circuit portion33alternately switches between the second state and the first state during regeneration. In the second state, sequentially, a current flows to the positive electrode terminal PV of the third power conversion circuit portion33, the first transistor S1, the reactor22, and the positive electrode terminal PB of the battery11, the reactor22is DC excited, and magnetic energy is accumulated. In the first state, an electromotive voltage (induced voltage) is generated between both ends of the reactor22so as to prevent a change in magnetic flux due to a current flowing to reactor22being cut off. An induced voltage caused by the magnetic energy accumulated in the reactor22is stepped down, and thus a stepped down voltage lower than a voltage between the positive electrode terminal PV and the negative electrode terminal NV of the third power conversion circuit portion33is applied between the positive electrode terminal PB and the negative electrode terminal NB of the battery11.

The capacitor unit23includes a first smoothing capacitor41, a second smoothing capacitor42, and a noise filter43.

The first smoothing capacitor41is connected between the positive electrode terminal PB and the negative electrode terminal NB of the battery11. The first smoothing capacitor41smoothes a voltage fluctuation which is generated with the on/off switching operations of the first transistor S1and the second transistor S2during the regeneration of the third power conversion circuit portion33.

The second smoothing capacitor42is connected between the positive electrode terminal PI and the negative electrode terminal NI of each of the first power conversion circuit portion31and the second power conversion circuit portion32, and between the positive electrode terminal PV and the negative electrode terminal NV of the third power conversion circuit portion33. The second smoothing capacitor42is connected to a plurality of positive electrode terminal PI and negative electrode terminals NI, and the positive electrode terminal PV and the negative electrode terminal NV through the positive electrode bus bar50pand the negative electrode bus bar50n. The second smoothing capacitor42smoothes a voltage fluctuation which is generated with the on/off switching operation of each of the transistors UH, UL, VH, VL, WH, and WL of each of the first power conversion circuit portion31and the second power conversion circuit portion32. The second smoothing capacitor42smoothes a voltage fluctuation which is generated with the on/off switching operations of the first transistor S1and the second transistor S2during a boost in voltage of the third power conversion circuit portion33.

The noise filter43is connected between the positive electrode terminal PI and the negative electrode terminal NI of each of the first power conversion circuit portion31and the second power conversion circuit portion32, and between the positive electrode terminal PV and the negative electrode terminal NV of the third power conversion circuit portion33. The noise filter43includes two capacitors which are connected in series to each other. A connection point between the two capacitors is connected to the body ground or the like of the vehicle10.

The resistor24is connected between the positive electrode terminal PI and the negative electrode terminal NI of each of the first power conversion circuit portion31and the second power conversion circuit portion32, and between the positive electrode terminal PV and the negative electrode terminal NV of the third power conversion circuit portion33.

The first current sensor25is disposed at the first bus bar51that connects the connection point TI of the first power conversion circuit portion31in each phase and the first input and output terminal Q1, and detects a current of each of the U-phase, the V-phase, and the W-phase. The second current sensor26is disposed at the second bus bar52that connects the connection point TI of the second power conversion circuit portion32in each phase and the second input and output terminal Q2, and detects a current of each of the U-phase, the V-phase, and the W-phase. The third current sensor27is disposed at the third bus bar53that connects the connection point between the first transistor S1and the second transistor S2and the reactor22, and detects a current flowing to the reactor22.

Each of the first current sensor25, the second current sensor26, and the third current sensor27is connected to the electronic control unit28by a signal line.

The electronic control unit28controls an operation of each of the first motor12and the second motor13. For example, the electronic control unit28is a software functional unit that functions by a predetermined program being executed by a processor such as a central processing unit (CPU). The software functional unit is an electronic control unit (ECU) including a processor such as a CPU, a read only memory (ROM) that stores a program, a random access memory (RAM) that temporarily stores data, and an electronic circuit such as a timer. Meanwhile, at least a portion of the electronic control unit28may be an integrated circuit such as a large scale integration (LSI). For example, the electronic control unit28executes feedback control or the like of a current using a current detection value of the first current sensor25and a current target value according to a torque command value for the first motor12, and generates a control signal which is input to the gate drive unit29. For example, the electronic control unit28executes feedback control or the like of a current using a current detection value of the second current sensor26and a current target value according to a regeneration command value for the second motor13, and generates a control signal which is input to the gate drive unit29. The control signal is a signal indicating a timing at which on (electrical conduction)/off (cutoff) driving is performed on each of the transistors UH, VH, WH, UL, VL, and WL of each of the first power conversion circuit portion31and the second power conversion circuit portion32. For example, the control signal is a pulse-width modulated signal or the like.

The gate drive unit29generates a gate signal for performing actual on (electrical conduction)/off (cutoff) driving on each of the transistors UH, VH, WH, UL, VL, and WL of each of the first power conversion circuit portion31and the second power conversion circuit portion32, on the basis of the control signal which is received from the electronic control unit28. For example, the gate drive unit29executes the amplification, level shift and the like of the control signal, and generates a gate signal.

The gate drive unit29generates a gate signal for performing on (electrical conduction)/off (cutoff) driving on each of the first transistor S1and the second transistor S2of the third power conversion circuit portion33. For example, the gate drive unit29generates a gate signal having a duty ratio according to a boost voltage command during a boost in voltage of the third power conversion circuit portion33or a step down voltage command during the regeneration of the third power conversion circuit portion33. The duty ratio is a ratio between the first transistor S1and the second transistor S2.

As shown inFIGS. 1, 2 and 4, in each of the first power conversion circuit portion31and the second power conversion circuit portion32of the power module21, a high side arm switching element and a low side arm switching element corresponding to each of the three phases form element arrays PU1, PV1, PW1, PU2, PV2, and PW2. In each of the first power conversion circuit portion31and the second power conversion circuit portion32, three element arrays PU1, PV1, and PW1and three element arrays PU2, PV2, and PW2corresponding to the three phases are respectively disposed side by side in the first direction D1. For example, in the first power conversion circuit portion31, the element array PU1of the high side arm and low side arm U-phase transistors UH and UL, the element array PV1of the high side arm and low side arm V-phase transistors VH and VL, and the element array PW1of the high side arm and low side arm W-phase transistors WH and WL are sequentially disposed side by side in the first direction D1.

For example, in the second power conversion circuit portion32, the element array PU2of the high side arm and low side arm U-phase transistors UH and UL, the element array PV2of the high side arm and low side arm V-phase transistors VH and VL, and the element array PW2of the high side arm and low side arm W-phase transistors WH and WL are sequentially disposed side by side in the first direction D1.

In each of the first power conversion circuit portion31and the second power conversion circuit portion32, a high side arm switching element and a low side arm switching element in the element arrays PU1, PV1, PW1, PU2, PV2, and PW2corresponding to each of the three phases are disposed side by side in the first direction D1. In each of the high side arm and low side arm U-phase transistors UH and UL, the high side arm and low side arm V-phase transistors VH and VL, and the high side arm and low side arm W-phase transistors WH and WL, the transistor of a high side arm and the transistor of a low side arm are disposed side by side in the first direction D1.

Three element arrays PU1, PV1, and PW1corresponding to the three phases of the first power conversion circuit portion31and three element arrays PU2, PV2, and PW2corresponding to the three phases of the second power conversion circuit portion32are disposed at positions facing each other in a second direction D2orthogonal to the first direction D1for each phase. The element array PU1of the high side arm and low side arm U-phase transistors UH and UL of the first power conversion circuit portion31and the element array PU2of the high side arm and low side arm U-phase transistors UH and UL of the second power conversion circuit portion32are disposed opposite to each other in the second direction D2.

The element array PV1of the high side arm and low side arm V-phase transistors VH and VL of the first power conversion circuit portion31and the element array PV2of the high side arm and low side arm V-phase transistors VH and VL of the second power conversion circuit portion32are disposed opposite to each other in the second direction D2. The element array PW1of the high side arm and low side arm W-phase transistors WH and WL of the first power conversion circuit portion31and the element array PW2of the high side arm and low side arm W-phase transistors WH and WL of the second power conversion circuit portion32are disposed opposite to each other in the second direction D2.

Element arrays PS including switching elements of a high side arm and a low side arm of the third power conversion circuit portion33are disposed side by side next to the first power conversion circuit portion31and the second power conversion circuit portion32in the first direction D1. The first transistors S1of a high side arm of the third power conversion circuit portion33are disposed side by side next to the second power conversion circuit portion32in the first direction D1. The second transistors S2of a low side arm of the third power conversion circuit portion33are disposed side by side next to the first power conversion circuit portion31in the first direction D1. In the third power conversion circuit portion33, the first transistor S1of a high side arm and the second transistor S2of a low side arm forming a pair are disposed opposite to each other in the second direction D2.

As shown inFIG. 2, the power conversion device1includes two heat dissipation portions61having the power module21interposed therebetween from both sides in a thickness direction (third direction) E of the power module21, a joint62, and two seal members63. The two heat dissipation portions61corresponds to a first heat dissipation portion61aand a second heat dissipation portion61b. The heat dissipation portion61includes a heat dissipation case64and a heat dissipation plate65.

The outer shape of the heat dissipation case64is formed in, for example, a rectangular box shape. The heat dissipation case64includes a refrigerant flow channel66through which a refrigerant circulates. The refrigerant flow channel66is formed by a plurality of wall portions67defining recessed grooves in the inside of the heat dissipation case64. The refrigerant flow channel66is connected to a refrigerant supply port68aand a refrigerant discharge port68bwhich are formed in the heat dissipation case64of the first heat dissipation portion61a.

The refrigerant supply port68aand the refrigerant discharge port68bare formed on the ends of the heat dissipation case64.

For example, the refrigerant supply port68aand the refrigerant discharge port68bmay be formed on a first end64aout of a first end64aand a second end64bin the first direction D1of the heat dissipation case64. The refrigerant supply port68aand the refrigerant discharge port68bare formed side by side in the second direction D2on the first end64a. The refrigerant supply port68aand the refrigerant discharge port68bof the first heat dissipation portion61aare connected to holes passing through the heat dissipation case64in the thickness direction E. The refrigerant supply port68aand the refrigerant discharge port68bof the second heat dissipation portion61bare connected to recessed grooves along which the inside of the heat dissipation case64extends in the thickness direction E.

As shown inFIG. 4, the refrigerant flow channel66includes a first flow channel71and a second flow channel72extending in the first direction D1, and a plurality of branching flow channels73branching between the first flow channel71and the second flow channel72and extending in the second direction D2.

The first flow channel71extends from the refrigerant supply port68aof the first end64atoward the second end64bin the first direction D1. Specifically, the first flow channel71includes a connecting portion71aconnected to the refrigerant supply port68aand a straight portion71bextending linearly along the direction (first direction D1) parallel to the branching flow channel73. The first flow channel71is configured such that the cross-sectional area (cross-sectional area orthogonal to a circulation direction) of the connecting portion71abecomes larger than the cross-sectional area of the straight portion71b.

The second flow channel72extends from the second end64btoward the refrigerant discharge port68bof the first end64ain the first direction D1. Specifically, the second flow channel72includes a connecting portion72aconnected to the refrigerant discharge port68band a straight portion72bextending linearly along the direction (first direction D1) parallel to the branching flow channel73. The second flow channel72is configured such that the cross-sectional area of the connecting portion72abecomes larger than the cross-sectional area of the straight portion72b.

The plurality of branching flow channels73connect the first flow channel71and the second flow channel72. Specifically, the branching flow channel73includes three first branching flow channels73acorresponding to the three phases of the first power conversion circuit portion31and the second power conversion circuit portion32, and one second branching flow channel73bcorresponding to the third power conversion circuit portion33.

The first branching flow channels73aare provided at positions overlapping, in a plan view, the element arrays PU1, PV1, and PW1of the first power conversion circuit portion31and the element arrays PU2, PV2, and PW2of the second power conversion circuit portion32which correspond to the respective three phases and face each other in the second direction D2. In each of the three phases, the upstream portion (region on the first flow channel71side) of the first branching flow channel73aoverlaps the element arrays PU1, PV1, and PW1of the first power conversion circuit portion31in a plan view. The downstream portion (region on the second flow channel72side) of the first branching flow channel73aoverlaps the element arrays PU2, PV2, and PW2of the second power conversion circuit portion32in a plan view.

The first branching flow channel73ais configured such that the cross-sectional areas of its upstream end (portion connected to the first flow channel71) and its downstream end (portion connected to the second flow channel72) become smaller than that of its central portion. Specifically, the upstream end and the downstream end of the first branching flow channel73aare configured such that their flow channel widths in the first direction D1become larger than that of its central portion. The central portion of the first branching flow channel73aoverlaps the entirety of the first power conversion circuit portion31and the second power conversion circuit portion32in a plan view. The upstream end and the downstream end of the first branching flow channel73aare located outside of the first power conversion circuit portion31and the second power conversion circuit portion32in the second direction.

The second branching flow channel73bis provided at a position overlapping, in a plan view, the first transistor S1of a high side arm and the second transistor S2of a low side arm which face each other in the second direction D2in one element array PS of the third power conversion circuit portion33. The upstream portion (region on the first flow channel71side) of the second branching flow channel73boverlaps the second transistor S2of a low side arm in a plan view. The downstream portion (region on the second flow channel72side) of the second branching flow channel73boverlaps the first transistor S1of a high side arm in a plan view. Meanwhile, the shape of the second branching flow channel73bin a plan view is the same as that of the first branching flow channel73a. That is, the central portion of the second branching flow channel73boverlaps the entirety of the third power conversion circuit portion33in a plan view. The upstream end and the downstream end of the first branching flow channel73aare located outside of the third power conversion circuit portion33in the second direction.

The above-described cross-sectional area a of the straight portion71bof the first flow channel71is formed to be larger than the cross-sectional area b of the upstream end of the branching flow channel73. For example, a relation of a≥4b is established.

As shown inFIG. 2, the outer shape of the heat dissipation plate65in a plan view is formed in a plate shape having substantially the same size as that of the heat dissipation case64. The heat dissipation plate65is connected to the wall portion67of the heat dissipation case64, and seals the refrigerant flow channel66by blocking the opening end of a recessed groove. Two through-holes65afacing and communicating with the refrigerant supply port68aand the refrigerant discharge port68b, respectively, of the heat dissipation case64are formed on the end of the heat dissipation plate65.

A surface facing the side opposite to the heat dissipation case64in the heat dissipation plate65configures a mounting surface65A on which the power module21is mounted. The heat dissipation plate65includes a plurality of fins (not shown) functioning as a heat sink on a surface65B on the side opposite to the mounting surface65A in the thickness direction E. The plurality of fins are disposed within each branching flow channel73in a state where the heat dissipation plate65is assembled in the heat dissipation case64. For example, the outer shape of the fin is formed in a wave type or a pin type which makes it possible to dispose the fins in a higher density than that with a straight type.

The joint62is disposed at a position overlapping the refrigerant supply port68aand the refrigerant discharge port68b(through-holes65a), in a plan view, between the first heat dissipation portion61aand the second heat dissipation portion61b.

That is, the joint62is disposed next to the power module21in the first direction D1. The joint62includes a first refrigerant flow channel62aand a second refrigerant flow channel62bfacing and communicating with the respective through-holes65acorresponding to the heat dissipation plate65.

The seal member63is disposed between each heat dissipation portion61(heat dissipation plate65) and the joint62. Through-holes63apassing through the seal member63in the thickness direction E are formed in the seal member63. The through-holes63aface and communicate with each of the two through-holes65aformed in the heat dissipation plate65and the two refrigerant flow channels62aand62bformed in the joint62. The seal member63seals an interval between the heat dissipation plate65and the joint62so as to perform sealing by mutually connecting a corresponding through-hole65aand refrigerant flow channels62aand62bout of the through-holes65aof the heat dissipation plate65and the refrigerant flow channels62aand62bof the joint62.

Each cross-sectional area c of the refrigerant supply port68aand the refrigerant discharge port68bof the heat dissipation case64, the through-hole65aof the heat dissipation plate65, the refrigerant flow channels62aand62bof the joint62, and the through-hole63aof the seal member63is formed to be larger than the cross-sectional area b of the upstream end of the branching flow channel73. For example, a relation of c/8≥b is established.

FIG. 5is an exploded perspective view illustrating the heat dissipation case64and the joint62of each of the first heat dissipation portion61aand the second heat dissipation portion61bin the power conversion device1according to the embodiment of the present invention, and is a diagram illustrating a circulation path of a refrigerant. Meanwhile, inFIGS. 4 and 5, flows of the refrigerant are shown by arrows.

As shown inFIGS. 4 and 5, a refrigerant which is supplied from the outside to two heat dissipation portions61first passes through the refrigerant supply port68aof the first heat dissipation portion61a(see arrow R1), and flows in by branching into the refrigerant flow channel66of the first heat dissipation portion61aand the first refrigerant flow channel62aof the joint62. The refrigerant flowing through the first refrigerant flow channel62aof the joint62passes through the refrigerant supply port68aof the second heat dissipation portion61b, and flows into the refrigerant flow channel66of the second heat dissipation portion61b(see arrow R2).

In the refrigerant flow channel66of each of the first heat dissipation portion61aand the second heat dissipation portion61b, the refrigerant flows in by branching into the plurality of branching flow channels73while flowing through the first flow channel71from the first end64atoward the second end64bin the first direction D1(see arrow R3). The refrigerant flowing through the plurality of branching flow channels73from the first flow channel71toward the second flow channel72in the second direction D2cools a plurality of element arrays PU1, PV1, PW1, PU2, PV2, PW2, and PS of the power module21. Specifically, the refrigerant flowing through the first branching flow channel73afirst cools the element arrays PU1, PV1, and PW1of the first power conversion circuit portion31, and next cools the element arrays PU2, PV2, and PW2of the second power conversion circuit portion32(see arrow R4). The refrigerant flowing through the second branching flow channel73bfirst cools the second transistor S2of a low side arm in the element array PS of the third power conversion circuit portion33, and next cools the first transistor S1of a high side arm (see arrow R5).

The refrigerant having passed through the branching flow channel73flows into the second flow channel72. The refrigerant flows through the second flow channel72from the second end64btoward the first end64a, and flows into the refrigerant discharge port68b(see arrow R6). The refrigerant flowing through the refrigerant discharge port68bof the second heat dissipation portion61bpasses through the second refrigerant flow channel62bof the joint62, and flows into the refrigerant discharge port68bof the first heat dissipation portion61a(see arrow R7). The refrigerant passing through the refrigerant discharge port68bof the first heat dissipation portion61ais discharged from the two heat dissipation portions61to the outside.

In the power conversion device1of the present embodiment, the element arrays PU1, PV1, PW1, PU2, PV2, and PW2of the first power conversion circuit portion31and the second power conversion circuit portion32are configured to overlap the first branching flow channels73abranched from the first flow channel71in a plan view.

According to this configuration, as compared with a case where a plurality of power conversion circuit portions are disposed on a refrigerant flow channel of one system, it is possible to suppress an increase in the temperature gradient of a refrigerant between the upstream side and the downstream side of the refrigerant flow channel associated with an increase in the number of power conversion circuit portions. That is, the number of branching flow channels73or the cross-sectional areas thereof are adjusted in accordance with the number of power conversion circuit portions, the amount of heat generation, or the like, and thus it is possible to uniformly and efficiently cool the element arrays PU1, PV1, PW1, PU2, PV2, PW2, and PS of the power conversion circuit portions31to33which are disposed on the branching flow channel73. Further, it is possible to prevent the flow channel length of one branching flow channel73from increasing, and to suppress an increase in a loss of pressure of the refrigerant. In each of the first motor12and the second motor13, since the first branching flow channel73ais provided corresponding to each phase, it is possible to suppress a change in cooling performance among a plurality of phases of each of the motors12and13, and to make cooling performance between a plurality of phases uniform.

FIG. 6is a diagram illustrating a configuration of a portion of the vehicle10in which the power conversion device1according to the embodiment is mounted.

Here, as shown inFIG. 6, power boosted in the power conversion device1and power generated in the second motor13are output to the first motor12. Therefore, as shown inFIG. 4, the element arrays PU1, PV1, and PW1(seeFIG. 1or the like) of the first power conversion circuit portion31corresponding to the first motor12have more of a tendency to generate heat than the element arrays PU2, PV2, and PW2of the second power conversion circuit portion32corresponding to the second motor13. Therefore, in each of the first branching flow channels73a, the element arrays PU1, PV1, and PW1of the first power conversion circuit portion31are disposed further upstream than the element arrays PU2, PV2, and PW2of the second power conversion circuit portion32, and thus it is possible to secure a difference in temperature between the refrigerant and the first power conversion circuit portion31. As a result, it is possible to efficiently cool the first power conversion circuit portion31.

Thereby, it is possible to uniformly and efficiently cool the element arrays PU1, PV1, PW1, PU2, PV2, and PW2of the first power conversion circuit portion31and the second power conversion circuit portion32, and to suppress an increase in a difference in cooling performance between a plurality of element arrays PU1, PV1, PW1, PU2, PV2, and PW2.

Thereby, in predetermined cooling performance such as, for example, radiation performance of a radiator which is relevant to the pump capacity of the refrigerant and the temperature of the refrigerant, it is possible to uniformly and efficiently cool the plurality of element arrays PU1, PV1, PW1, PU2, PV2, and PW2of the first power conversion circuit portion31and the second power conversion circuit portion32.

In the present embodiment, in the element arrays PU1, PV1, PW1, PU2, PV2, and PW2of the first power conversion circuit portion31and the second power conversion circuit portion32in the respective first branching flow channels73a, the high side arm switching element and the low side arm switching element are disposed side by side in the first direction D1. Thereby, it is possible to suppress an increase in a difference in cooling performance between the high side arm switching element and the low side arm switching element.

In the present embodiment, during a boost in voltage of the third power conversion circuit portion33, heat generation due to the second transistor S2of a low side arm becomes larger than that of the first transistor S1of a high side arm. In addition, during the regeneration of the third power conversion circuit portion33, heat generation due to the first transistor S1of a high side arm becomes larger than that of the second transistor S2of a low side arm. However, in a case where the output allowable current or the output allowable power of the battery11is larger than the input allowable current or the input allowable power of the battery when voltage boost and regeneration are compared with each other, heat generation due to the second transistor S2of a low side arm becomes larger than that of the first transistor S1of a high side arm.

Consequently, in the present embodiment, in the second branching flow channel73b, the second transistor S2of a low side arm is disposed on the upstream side of the first transistor S1of a high side arm.

Therefore, it is possible to secure a difference in temperature between the refrigerant and the second transistor S2of a low side arm. As a result, it is possible to efficiently cool the second transistor S2of a low side arm. Thereby, it is possible to uniformly and efficiently cool the first transistor S1of a high side arm and the second transistor S2of a low side arm of the third power conversion circuit portion33, and to suppress an increase in a difference in cooling performance between the first transistor S1and the second transistor S2.

Hereinafter, a modification example of the embodiment will be described.

In the above-described embodiment, the power conversion device1is assumed to include two heat dissipation portions61having the power module21interposed therebetween from both sides in the thickness direction E, but there is no limitation thereto. The power conversion device1may include one heat dissipation portion61in which the power module21is mounted.

Meanwhile, in the above-described embodiment, the power conversion device1is assumed to be mounted in the vehicle10, but may be mounted in other instruments without being limited thereto.

The embodiments of the present invention have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, these embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The appended claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.