Power conversion device

Abstract

A power conversion device (4) comprises a smoothing capacitor (5) connected to a semiconductor device (90). The power conversion device (4) comprises a heat sink (14) having a plurality of fins (14a) for transmitting heat generated by the semiconductor device (90), and a flow path forming member (13). The flow path forming member (13) is joined to the heat sink (14) to form a joining portion in which a liquid gasket is interposed, and forms a cooling flow path (140) between the plurality of fins (14a). The power conversion device (4) comprises an enclosure wall (13b) and a gasket reception portion (17) that are provided further inside than the joining portion and outside the cooling flow path (140). The gasket reception portion (17) is filled with a liquid gasket that is integrated with the liquid gasket interposed in the joining portion and covers the outside of the surrounding wall (13b).

Description

Power Conversion Device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2024-022324 filed in Japan on February 16, 2024, the contents of which are incorporated by reference in their entirety.

[0002] The disclosure herein relates to power conversion devices.

[0003] Patent Document 1 discloses a power converter that is less susceptible to problems caused by refrigerant leaking between a heat sink and a flow path forming member. The power converter in Patent Document 1 seals the flow path by sandwiching the heat sink with an O-ring seal.

[0004] Japanese Patent Application Laid-Open No. 2021-44861

[0005] The technique disclosed in Patent Document 1 leaves room for improvement in terms of achieving both suppression of inductance between the capacitor and the semiconductor device and cooling performance.

[0006] An object of the disclosure in this specification is to provide a power conversion device that can achieve both suppression of inductance between a capacitor and a semiconductor device and cooling performance.

[0007] The multiple aspects disclosed in this specification employ different technical means to achieve their respective objectives. Furthermore, the reference symbols in parentheses in the claims and this section are merely examples showing the correspondence between specific means described in the embodiments below as one aspect, and do not limit the technical scope.

[0008] One of the disclosed power conversion devices includes a semiconductor device that converts power input from a power source and supplies current to an electrical load; a capacitor connected to the semiconductor device; a heat sink having a plurality of fins to which heat generated by the semiconductor device is transferred; a flow path forming member that is joined to the heat sink at a location closer to the semiconductor device than the capacitor to form a joint where a liquid gasket is interposed and that forms a cooling flow path between the heat sink and the plurality of fins; an enclosure wall that is located inside the joint but outside the cooling flow path; and a gasket receiving portion that is located inside the joint but outside the enclosure wall, that is integrated with the liquid gasket interposed at the joint, that covers the outside of the enclosure wall, and that stores dried liquid gasket.

[0009] If the joining strength between the heat sink and the flow path forming member is strengthened, a liquid gasket interposed at the joint may protrude from the joint into the cooling flow path, narrowing the flow path. Therefore, this power converter includes a gasket receiving portion located inside the joint but outside the enclosure wall. By including the gasket receiving portion, the liquid gasket in this power converter is accumulated and solidified from the joint to the gasket receiving portion. This prevents the liquid gasket from protruding into the flow path. Furthermore, the fluid in the cooling flow path is isolated from the outside by the liquid gasket accumulated between the gasket receiving portion and the joint. The gasket receiving portion functions to further enhance the sealing performance at the joint. Therefore, a power converter can be provided that can suppress the force acting on the joint by the fluid flowing through the cooling flow path and ensure cooling performance.

[0010] Furthermore, before joining the heat sink and the flow path forming member, an appropriate amount of liquid gasket according to the volume of the gasket receiving portion can be interposed at the joining portion. By setting the volume of this gasket receiving portion as small as possible, the distance from the semiconductor device to the capacitor can be set short while ensuring sealing at the gasket receiving portion. Because liquid gaskets are highly flexible sealing materials, they easily flow to fill small-volume gasket receiving portions, contributing to ensuring sealing even with small volumes. This contributes to reducing inductance between the capacitor and the semiconductor device. As a result, the power conversion device can achieve both reduced inductance between the capacitor and the semiconductor device and excellent cooling performance.

[0011] It is a circuit diagram of the power conversion device of the first embodiment. It is a partial cross-sectional view showing the configuration of the power conversion device. It is a partial enlarged view showing the seal configuration in a state where a seal member is removed. It is a partial enlarged view showing the seal configuration provided with a seal member. It is a partial enlarged view showing the seal configuration of a second embodiment.

[0012] Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to matters described in the preceding embodiment will be assigned the same reference numerals, and duplicate descriptions may be omitted. In each embodiment, when only a part of the configuration is described, other previously described embodiments may be applied to the other parts of the configuration. In addition to combinations of parts that are specifically specified as being combinable in each embodiment, it is also possible to partially combine embodiments even if not specified, as long as there is no particular problem with the combination.

[0013] First Embodiment A first embodiment disclosing an example of a power conversion device will be described with reference to FIGS. 1 to 4. Application examples of the power conversion device are as follows. The power conversion device can be applied to an on-board power conversion device mounted on vehicles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles. The power conversion device can also be mounted on flying objects such as electric vertical take-off and landing aircraft and drones, ships, construction machinery, agricultural machinery, etc. Below, an example in which the power conversion device is applied to a vehicle will be described.

[0014] 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 supply 2 is a DC voltage source configured with a chargeable and dischargeable secondary battery. The secondary battery is, for example, a lithium-ion battery, a nickel-metal hydride battery, or the like. The motor generator 3 is, for example, a three-phase AC rotating electric machine, and is an example of an electrical load to which the power conversion device 4 supplies power. The motor generator 3 functions as a drive source for the vehicle, i.e., an electric motor. The motor generator 3 functions as a generator during regeneration. The power conversion device 4 converts power between the DC power supply 2 and the motor generator 3.

[0015] The power conversion device 4 includes a power conversion circuit. As shown in FIG. 1 , the power conversion device 4 includes a smoothing capacitor 5 and an inverter 6, which is a power conversion circuit. The smoothing capacitor 5 mainly functions to smooth the DC voltage supplied from the DC power supply 2. The smoothing capacitor 5 is connected to a P line 10, which is a power supply line on the high potential side, and an N line 11, which is a power supply line on the low potential side. The smoothing capacitor 5 is an example of a capacitor defined in the claims.

[0016] The smoothing capacitor 5 is connected in parallel to the DC power supply 2. The P line 10 is connected to the positive terminal of the DC power supply 2. The N line 11 is connected to the negative terminal of the DC power supply 2. The positive terminal of the smoothing capacitor 5 is connected to the P line 10 between the DC power supply 2 and the inverter 6. The negative terminal of the smoothing capacitor 5 is connected to the N line 11 between the DC power supply 2 and the inverter 6. The P line 10 includes a plurality of P bus bars that connect electrical components together. The N line 11 includes a plurality of N bus bars that connect electrical components together.

[0017] The inverter 6 is a DC-AC conversion circuit. In accordance with switching control by a control circuit provided on the control circuit board 93, the inverter 6 converts a DC voltage into a three-phase AC voltage and outputs it to the motor generator 3. This operation drives the motor generator 3 to generate a predetermined torque.

[0018] The control circuit generates a drive command for operating the IGBT and outputs it to the drive circuit. The control circuit generates the drive command based on, for example, a torque request input from a higher-level ECU and signals detected by various sensors. The various sensors include a current sensor 7, a rotation angle sensor, and a voltage sensor. The control circuit outputs, for example, a PWM signal as the drive command. The control circuit is equipped with a microcomputer. The rotation angle sensor detects the rotation angle of the rotor of the motor-generator 3 and outputs it to the control circuit. The voltage sensor detects the voltage across the smoothing capacitor 5 and outputs it to the control circuit.

[0019] During regenerative braking of the vehicle, inverter 6 converts the three-phase AC voltage generated by motor generator 3 in response to rotational force from the wheels into a DC voltage under switching control of the control circuit. The converted DC power is output to P line 10. In this way, inverter 6 performs bidirectional power conversion between DC power supply 2 and motor generator 3.

[0020] The power conversion device 4 may be configured to include a noise filter. A case in which a configuration including a noise filter is adopted is described below. The noise filter is connected to each of the P line 10 and the N line 11. The noise filter is connected in parallel to the DC power supply 2. The positive terminal of the noise filter is connected to the P line 10 between the DC power supply 2 and the smoothing capacitor 5. The negative terminal of the noise filter is connected to the N line 11 between the DC power supply 2 and the smoothing capacitor 5. The noise filter removes noise input to and output from the P line 10 and the N line 11. The noise filter may be configured to include a capacitor. The capacitor included in the noise filter has a smaller capacitance than the smoothing capacitor 5.

[0021] The inverter 6 includes upper and lower arm circuits 9 corresponding to each of the three phases. The upper and lower arm circuits 9 are sometimes referred to as legs. The upper and lower arm circuits 9 have an upper arm 9H and a lower arm 9L. The upper arm 9H and the lower arm 9L are connected in series between the P line 10 and the N line 11, with the upper arm 9H on the P line 10 side and the lower arm 9L on the N line 11 side.

[0022] The connection point between the upper arm 9H and the lower arm 9L is connected to the winding 3a of the corresponding phase in the motor generator 3 via an output line 8. Of the upper and lower arm circuits 9, the U-phase upper and lower arm circuit 9U is connected to the U-phase winding 3a via a corresponding output line 8. The V-phase upper and lower arm circuit 9V is connected to the V-phase winding 3a via a corresponding output line 8. The W-phase upper and lower arm circuit 9W is connected to the W-phase winding 3a via a corresponding output line 8. At least a portion of the output lines 8 is formed of a conductive member such as a bus bar.

[0023] The power conversion device 4 includes current sensors 7 that individually detect the currents flowing through the three-phase lines that make up the output line 8. The current sensors 7 are fixed to, for example, bus bars that form the three-phase lines. The current sensors 7 output electrical signals corresponding to the output currents of the arms to the control circuit. The current sensors 7 include resistance detection sensors or magnetic field detection sensors.

[0024] A current sensor 7 that detects current using resistance detection includes a shunt resistor and a high-speed amplifier. A resistance detection current sensor 7 includes an electronic component having a circuit that converts a voltage drop across the shunt resistor into a current and detects the current value. A current sensor 7 that detects current using magnetic field detection includes a Hall IC, which is a current sensor component. The Hall IC detects the current value by converting the magnetic field generated around the current into a voltage using the Hall effect and measuring it. A magnetic field detection current sensor component includes an electronic component having a Hall element and an amplifier circuit. A magnetic field detection current sensor component may be a current sensor that detects a magnetic field contactlessly using an MI (Magneto Impedance) element.

[0025] The inverter 6 has six arms. Each arm is equipped with a switching element. The number of switching elements constituting each arm is not particularly limited. There may be one or more. When there are more than one switching elements, the multiple switching elements connected in parallel are turned on and off at the same timing by a common gate drive signal.

[0026] In this specification, an n-channel MOSFET 91 is used as the switching element constituting each arm. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. In the upper arm 9H, the drain of the MOSFET 91 is connected to a P line 10. In the lower arm 9L, the source of the MOSFET 91 is connected to an N line 11. The source of the MOSFET 91 in the upper arm 9H and the drain of the MOSFET 91 in the lower arm 9L are connected to each other.

[0027] A freewheeling diode 92 is connected in antiparallel to each MOSFET 91. The diode 92 may be a parasitic diode of the MOSFET 91 or may be provided separately from the parasitic diode. The anode of the diode 92 is connected to the source of the corresponding MOSFET 91. The cathode of the diode 92 is connected to the drain.

[0028] The switching element is not limited to the MOSFET 91. An IGBT may be used as the switching element. The IGBT is an abbreviation for Insulated Gate Bipolar Transistor. In the case of an IGBT, a freewheeling diode is also connected in anti-parallel.

[0029] FIG. 2 shows the configuration of the power conversion device 4, partially in cross section. As shown in FIG. 2, the power conversion device 4 includes a plurality of semiconductor devices 90, a control circuit board 93, a smoothing capacitor 5, a current sensor 7, a heat sink 14, a flow path forming member 13, and the like. The semiconductor device 90 provides at least one arm of the power conversion circuit. The semiconductor device 90 provides one phase of upper and lower arm circuits 9. The plurality of semiconductor devices 90 are connected in parallel to provide the power conversion circuit. The plurality of semiconductor devices 90 may also be referred to as a plurality of semiconductor modules. Hereinafter, two directions that are orthogonal to each other are referred to as the X direction and the Y direction. The X direction indicates a direction along a horizontal plane. The Y direction corresponds to the vertical direction.

[0030] The current sensor 7 is located on the opposite side of the semiconductor device 90 from the smoothing capacitor 5. The power conversion device 4 includes a heat sink 14 that cools at least one side of the multiple semiconductor devices 90. In this configuration, the multiple semiconductor devices 90 and the heat sink 14 are stacked and arranged in the height direction, which is the Y direction. The semiconductor devices 90 are thin plates and installed with their thickness direction aligned as the stacking direction. The stacking direction is along the vertical direction. The smoothing capacitor 5, the semiconductor device 90, and the current sensor 7 are installed so as not to overlap in the orthogonal direction when viewed from above in the Y direction. This contributes to reducing the size of the power conversion device 4 in the stacking direction, as shown in FIG. 2 .

[0031] The power conversion device 4 may be configured to include a heat sink 14 and a cooler 12 that cool both sides of the multiple semiconductor devices 90. In this configuration, the cooler 12, the multiple semiconductor devices 90, and the heat sink 14 are stacked and installed in this order in the height direction. The cooler 12 may be configured to have a cooling fluid flowing inside, or may be configured to include a cooling plate. The cooler 12 absorbs heat from one side of the semiconductor devices 90 opposite the side facing the heat sink 14. The power conversion device 4 is configured to dissipate heat from both sides of the outer casing of the multiple semiconductor devices 90 that are perpendicular to the stacking direction.

[0032] The heat sink 14 includes a heat receiving portion 14b and a plurality of fins 14a that are cooled by the fluid flowing through the cooling flow path 140, and is made of a material with high thermal conductivity. The heat receiving portion 14b is provided on the back side opposite the surface on which the plurality of fins 14a are formed. The heat sink 14 includes a joining wall portion 14c provided on the side opposite the surface on which the heat receiving portion 14b is provided, so as to surround the plurality of fins 14a. The joining wall portion 14c is the portion of the heat sink 14 that joins to the flow path forming member 13.

[0033] The portion of the flow path forming member 13 facing the joining wall portion 14c and the joining wall portion 14c constitute a fixed portion that is fixed by a fixing device 15. A plurality of fixed portions are provided around the surrounding wall 13b, which will be described later. The fixed portion is a portion that is partially fixed at a joint where the heat sink 14 and the flow path forming member 13 are joined. A sealing member is interposed at the joint to seal the cooling flow path 140 from the outside. The fixing device 15 is, for example, a restraining member such as a bolt that fixes the flow path forming member 13 and the heat sink 14 together. The fixing device 15 is inserted into a through hole 14c2 formed in the heat sink 14 to integrally join the flow path forming member 13 and the heat sink 14. If the fixing device 15 is a bolt, the fixing device 15 is screwed into a female thread formed in the flow path forming member 13 to integrally join the flow path forming member 13 and the heat sink 14. The fixing device 15 has the function of applying a compressive force to the joint to make the sealing member uniform.

[0034] FIG. 3 is a partially enlarged view showing the seal configuration without the sealing material. FIG. 3 shows the state before the sealing material is applied to the joint. The sealing material is a soft and easily deformed material when interposed in the joint, and is an adhesive material that hardens over time. An example of a sealing material is a liquid gasket. A liquid gasket is an adhesive that provides a sealing effect. A liquid gasket is liquid at room temperature and forms a thin adhesive layer when applied to the joint and dries. A liquid gasket is soft before drying. The liquid gasket uniformly distributes at the joint and is easily extruded from the joint due to compressive forces acting on the joint. The liquid gasket provides a watertight effect at the joint, performs pressure resistance, and prevents fluid leakage from the cooling channel 140.

[0035] A gasket receiving portion 17 is formed between the flow path forming member 13 and the heat sink 14, located inside the joint and outside the surrounding wall 13b. The gasket receiving portion 17 is provided in a position outside the cooling flow path 140 so as to surround the surrounding wall 13b. The gasket receiving portion 17 corresponds to the gap formed between the flow path forming member 13 and the heat sink 14 when the sealing member is removed, as shown in FIG. 3 . The gasket receiving portion 17 has a volume that can receive a liquid gasket that protrudes from the joint when the flow path forming member 13 and the heat sink 14 are joined.

[0036] Fig. 4 is a partially enlarged view showing the sealing configuration with the sealing member provided. Fig. 4 shows the state in which the heat sink 14 and the flow path forming member 13 are joined together and the joint and the gasket receiving portion 17 are filled with the sealing member. As shown in Fig. 4, the gasket receiving portion 17 stores a liquid gasket that is integrated with the liquid gasket that seals the joint and covers the outside of the surrounding wall.

[0037] 3 and 4, the gasket receiving portion 17 is formed to include a base receiving portion 17a, an extension receiving portion 17c, and a tip receiving portion 17b. The base receiving portion 17a, the extension receiving portion 17c, and the tip receiving portion 17b are arranged in this order from the joint portion to the cooling flow path 140. The base receiving portion 17a, the extension receiving portion 17c, and the tip receiving portion 17b are arranged along the outside of the surrounding wall 13b.

[0038] The base-side receiving portion 17a is a portion adjacent to the base end of the surrounding wall 13b on the outside. The base-side receiving portion 17a is provided to connect to the joint. The base-side receiving portion 17a is an area whose cross-sectional area expands and changes relative to the joint. The base-side receiving portion 17a forms an annular gap extending horizontally or laterally from the joint. The base end of the surrounding wall 13b corresponds to the base portion of the surrounding wall 13b, which is the portion that begins to rise upward from the same height as the first joint surface 13a that forms the joint. The heat sink 14 has a wall surface that extends upward along the surrounding wall 13b from a corner 14c1 that corresponds to the end of the second joint surface 16 that forms the joint. This wall surface is shaped to move upwardly relative to the joint as it approaches the cooling channel 140 from the corner 14c1.

[0039] The extension receiving portion 17c is a portion adjacent to the outer side of the side wall portion of the surrounding wall 13b. The extension receiving portion 17c is a gap that connects to the base end receiving portion 17a outside the surrounding wall 13b. The extension receiving portion 17c is an area whose cross-sectional area is reduced relative to the base end receiving portion 17a. The extension receiving portion 17c forms an annular gap that extends in a direction intersecting the base end receiving portion 17a. The extension receiving portion 17c has a shape that extends upward along the surrounding wall 13b, away from the base end receiving portion 17a.

[0040] The tip side receiving portion 17b is a portion that faces upward relative to the tip of the surrounding wall 13b. The tip side receiving portion 17b is a gap that connects to the extended receiving portion 17c above the surrounding wall 13b and is adjacent to the cooling flow path 140. The tip side receiving portion 17b is an area whose cross-sectional area expands and changes relative to the extended receiving portion 17c. The tip side receiving portion 17b forms an annular gap that extends in a direction intersecting with the extended receiving portion 17c. The tip side receiving portion 17b forms an annular gap that extends horizontally or laterally relative to the extended receiving portion 17c. The tip side receiving portion 17b has a shape that extends along the surrounding wall 13b toward the multiple fins 14a, away from the tip side receiving portion 17b and the extended receiving portion 17c.

[0041] The tip side receiving portion 17b is formed in a shape that has a larger cross-sectional area than the adjacent extended receiving portion 17c. An opening 17d on the cooling flow path 140 side of the tip side receiving portion 17b is an end that opens to the cooling flow path 140. The opening 17d is formed in a shape that has a larger cross-sectional area than an area of ​​the tip side receiving portion 17b closer to the extended receiving portion 17c. The tip side receiving portion 17b has a shape that has a larger cross-sectional area as it approaches the cooling flow path 140.

[0042] The gasket receiving portion 17 has a shape that extends upward and then laterally from the area adjacent to the joint to the area adjacent to the cooling flow channel 140. With this configuration, the gasket receiving portion 17 is formed so that the liquid gasket that protrudes from the joint is lifted up and spreads throughout. The gasket receiving portion 17 has a shape that changes so that the cross-sectional area sequentially increases, decreases, and then increases again from the area adjacent to the joint to the area adjacent to the cooling flow channel 140.

[0043] The gap between the surrounding wall 13b and the fin 14a closest to the surrounding wall 13b is part of the cooling flow path 140, and it is preferable to set this gap to a small dimension. The dimension of the gap between the fin closest to the surrounding wall 13b and the surrounding wall 13b among the multiple fins 14a is set to be equal to or smaller than the outer dimension of the fin with the smallest outer dimension. This outer dimension corresponds to the smallest thickness dimension of the fin.

[0044] The cooling flow path 140 is a flow path formed around the fins 14a by joining the flow path forming member 13 and the heat sink 14 in the vertical direction to form a joint. The joint is a portion where a first joint surface 13a of the flow path forming member 13 and a second joint surface 16 of the heat sink 14 are joined. The first joint surface 13a is an end surface of the flow path forming member 13 formed to surround the cooling flow path 140. The second joint surface 16 is an end surface of the joining wall portion 14c that faces the flow path forming member 13. The multiple fins 14a face the cooling flow path 140 and form part of the wall that forms the cooling flow path 140.

[0045] The joints are provided so as to surround the cooling flow path 140. The power conversion device 4 includes an enclosure wall 13b provided inside the joints and outside the cooling flow path 140. The enclosure wall 13b is provided so as to surround the cooling flow path 140. The enclosure wall 13b is provided so as to surround the multiple fins 14a. As shown in FIG. 2 , the enclosure wall 13b is a vertical wall extending from the flow path forming member 13 toward the heat sink 14. The cooling flow path 140 is a flow path formed by being surrounded by the portion of the flow path forming member 13 facing the multiple fins 14a, the heat sink 14, and the enclosure wall 13b.

[0046] The heat sink 14 is made of aluminum, copper, or an alloy thereof. The heat sink 14 can be manufactured by, for example, die casting. The semiconductor device 90 is installed in contact with the heat receiving portion 14b of the heat sink 14 or via other intervening members, allowing heat transfer to and from the heat sink 14. The heat receiving portion 14b is formed in a flat plate shape to increase the contact area with the semiconductor device 90. A thermally conductive material, such as a highly thermally conductive gel, sheet, or grease, may be interposed between the heat receiving portion 14b and the semiconductor device 90. The multiple fins 14a are multiple protrusions protruding from the back surface of the heat receiving portion 14b. The multiple fins 14a are positioned so as to overlap the semiconductor device 90 in the stacking direction. With this configuration, heat from the semiconductor device 90 is transferred to the heat receiving portion 14b and then further transferred to the multiple fins 14a, where it is absorbed and cooled by the fluid flowing through the cooling flow path 140.

[0047] The cooling flow path 140 is formed inside the surrounding wall 13b and along the heat sink 14. The cooling flow path 140 is a flow path arranged throughout the multiple fins 14a. For example, the cooling flow path 140 is a flow path arranged in a serpentine manner over a wide area inside the surrounding wall 13b. The fluid flowing through the cooling flow path 140 may be 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.

[0048] The current sensor 7 is provided so as to have a portion that overlaps horizontally with the semiconductor device 90, the heat sink 14, and the cooler 12. The current sensor 7 is provided so as to cover an area in the vertical direction that includes the semiconductor device 90 and the heat sink 14. The smoothing capacitor 5, the semiconductor device 90, and the current sensor 7 are provided in a horizontally aligned position.

[0049] The smoothing capacitor 5 is provided over an area that includes the semiconductor device 90 in terms of vertical position. The smoothing capacitor 5 is provided over an area that includes the semiconductor device 90 and the heat sink 14 in terms of the stacking direction in which the semiconductor device 90 and the heat sink 14 are stacked. The smoothing capacitor 5 and the semiconductor device 90 are connected via a bus bar. This bus bar is included in the bus bars that form the P line 10 and the N line 11. The length of this bus bar is proportional to the distance between the smoothing capacitor 5 and the semiconductor device 90 in the horizontal direction.

[0050] The P line 10 and the N line 11 are insulated from each other by an insulating component. The insulating component is, for example, an input connector. Inside the input connector, terminals are provided that are connected to the ends of the bus bars that form each line. Terminals of a wire harness extending from the DC power supply 2 are connected to the terminals inside the input connector. As a result, each of the P line 10 and the N line 11 is electrically connected to the DC power supply 2.

[0051] The power conversion device 4 may be configured to house multiple semiconductor devices 90, a control circuit board 93, a smoothing capacitor 5, a current sensor 7, a heat sink 14, a flow path forming member 13, and the like, in a housing. In this configuration, output lines 8 connecting the motor-generator 3 and the semiconductor devices 90 are inserted through a side wall of the housing. The output lines 8 are insulated from the side wall of the housing by insulating components. The insulating components are, for example, output connectors. Terminals connected to the tips of the output bus bars are provided inside the output connectors. Terminals in the output connectors are connected to terminals of a wire harness extending from the motor-generator 3. As a result, each phase of the upper and lower arm circuits 9 is electrically connected to the windings 3a of the motor-generator 3.

[0052] The smoothing capacitor 5 includes a capacitor element, a sealing member, electrodes connected to the capacitor element, terminals, etc. The smoothing capacitor 5 includes a capacitor element and a sealing member filled in the capacitor element housing to seal the capacitor element. The sealing member seals the capacitor element in the housing space. The sealing member forms the outer shell of the smoothing capacitor 5. The outer shell of the smoothing capacitor 5 has a rectangular parallelepiped shape, excluding the terminals, etc. The sealing member is made of a thermosetting resin, such as epoxy resin. The sealing member is an insulator that fills the gaps between the capacitor element and electrodes and the capacitor element housing. With this configuration, the sealing member seals the capacitor element, electrodes, etc. One end of the terminals is connected to the electrodes inside the smoothing capacitor 5, and the other end protrudes from the sealing member. The terminals are connected to the P line 10 and the N line 11 within the housing via terminal couplings of the terminal base unit.

[0053] The smoothing capacitor 5 is installed with the direction in which its external length is smallest oriented horizontally or horizontally. This configuration reduces the horizontal length of the power conversion device 4 occupied by the smoothing capacitor 5, thereby reducing the physical size of the device in the direction in which the semiconductor device and the smoothing capacitor are aligned. Furthermore, the smoothing capacitor 5 is installed with the direction in which its external length is largest oriented vertically. This configuration allows the semiconductor device 90, heat sink 14, and flow path forming member 13 to be housed within the range of the vertical length occupied by the smoothing capacitor 5, thereby reducing the physical size of the entire device.

[0054] The semiconductor device 90 has a flattened outer shape due to the sealing material, except for terminals protruding from the sealing material. The semiconductor device 90 is installed so that the thickness direction, which is the smallest side dimension, is aligned with the vertical direction. The control circuit board 93 is installed above the semiconductor device 90 so that the thickness direction of the board is aligned with the vertical direction. This configuration makes it possible to reduce the vertical length of the power conversion device 4 occupied by the semiconductor device 90 and the control circuit board 93.

[0055] A terminal portion 90a forming a collector terminal and an emitter terminal protrudes from one side of the flat body of the semiconductor device 90. The terminal portion 90a protrudes toward the smoothing capacitor 5 and is connected to the P line 10 and the N line 11 via the terminal coupling portion of the terminal base unit. A relay terminal protrudes from the other side of the flat body. The relay terminal is connected to the output line 8. The gate terminal of the semiconductor device 90 is connected to a control circuit board 93. The control circuit board 93 forms a control circuit on which electronic components such as an arithmetic element that controls the operation of the MOSFET 91 are mounted.

[0056] The effects of the power conversion device 4 disclosed in the specification will be described. The power conversion device 4 includes a semiconductor device 90 that converts power input from a power source and supplies the converted current to an electrical load, and a capacitor connected to the semiconductor device 90. The power conversion device 4 includes a heat sink 14 having multiple fins 14a through which heat generated by the semiconductor device 90 is transferred, and a flow path forming member 13. The flow path forming member 13 is joined to the heat sink 14 at a location closer to the semiconductor device than the capacitor, forming a joint with a liquid gasket interposed therebetween. The flow path forming member 13 is joined to the heat sink 14 to form a cooling flow path 140 between the multiple fins 14a. The power conversion device 4 includes an enclosure wall 13b located inside the joint but outside the cooling flow path 140, and a gasket receiving portion 17 in which a liquid gasket is stored. The gasket receiving portion 17 is located inside the joint but outside the enclosure wall 13b. The gasket receiving portion 17 stores a dried liquid gasket that is integrated with the liquid gasket interposed in the joint and covers the outside of the surrounding wall 13b.

[0057] The power converter 4 includes a gasket receiving portion 17, which stores dried liquid gaskets in an integrated manner from the joint to the gasket receiving portion 17. Because the gasket receiving portion 17 receives the liquid gasket that protrudes from the joint, the liquid gasket is prevented from protruding into the flow path. The fluid in the cooling flow path is isolated from the outside by the gasket stored in the gasket receiving portion 17 and the gasket interposed in the joint. The gasket receiving portion 17 functions to further enhance the sealing performance at the joint. Therefore, the power converter 4 can suppress the force acting on the joint by the fluid flowing through the cooling flow path 140, thereby ensuring cooling performance.

[0058] This device allows an appropriate amount of liquid gasket to be placed at the joint, corresponding to the volume of the gasket receiving portion 17, before joining the heat sink 14 and the flow path forming member 13. This allows any liquid gasket that protrudes from the joint after joining to be retained in the gasket receiving portion 17, ensuring sealing at the gasket receiving portion. Setting the volume of the gasket receiving portion 17 as small as possible not only ensures sealing, but also shortens the distance from the semiconductor device 90 to the capacitor. Liquid gaskets are highly flexible sealing materials. Because of their flexibility, liquid gaskets easily flow to fill the small-volume gasket receiving portion 17, contributing to ensuring sealing even in small volumes. Therefore, the power conversion device 4 can shorten the current path between the capacitor and the semiconductor device, thereby reducing inductance between them.

[0059] The gasket receiving portion 17 includes a base receiving portion 17a, an extended receiving portion 17c, and a tip receiving portion 17b. The base receiving portion 17a is adjacent to the base end of the surrounding wall and is connected to the joint. The extended receiving portion 17c extends along the surrounding wall away from the base receiving portion. The tip receiving portion 17b is connected to the extended receiving portion and faces the tip of the surrounding wall 13b. This configuration provides a gasket receiving portion 17 that allows liquid gasket that spills out from the joint to flow along the surrounding wall toward the tip receiving portion 17b and store it there. This contributes to ensuring the volume of the gasket receiving portion 17 while reducing the distance from the semiconductor device 90 to the capacitor.

[0060] The tip receiving portion 17b has a shape with a larger cross-sectional area than the extended receiving portion 17c. With this configuration, the cross-sectional area of ​​the tip receiving portion facing the cooling flow path 140 is large, which reduces the pressure that the fluid exerts on the gasket. This helps to reduce deterioration of the gasket and ensures the life of the sealing performance.

[0061] The cross-sectional area of ​​the tip-side receiving portion 17b increases as it approaches the cooling flow path 140. This configuration increases the surface area of ​​the gasket that comes into contact with the fluid flowing through the cooling flow path 140, thereby reducing the pressure acting on the gasket and ensuring the longevity of the sealing performance.

[0062] The extension receiving portion 17c extends upward from the joint along the side wall of the surrounding wall 13b. This configuration allows the liquid gasket to protrude upward from the joint, making it less likely for the gasket to drip into the cooling flow path 140. This contributes to preventing clogging of the cooling flow path 140.

[0063] The dimension of the gap between the fin 14a that is closest to the surrounding wall 13b and the surrounding wall 13b is set to be equal to or smaller than the outer dimension of the fin with the smallest outer dimension. This configuration makes it possible to provide a power conversion device 4 in which the fins 14a are located close to the surrounding wall 13b. This contributes to reducing the distance from the semiconductor device 90 to the capacitor.

[0064] The capacitor is provided over an area that includes the semiconductor device 90 and the heat sink 14 in the stacking direction of the stacked semiconductor device 90 and the heat sink 14. With this configuration, the height occupied by the capacitor, the semiconductor device, and the heat sink can be reduced while suppressing the inductance between the capacitor and the semiconductor device.

[0065] Second Embodiment A second embodiment will be described with reference to Fig. 5. The power conversion device of the second embodiment differs from the first embodiment in the configuration relating to the gasket receiving portion and the surrounding wall. The configuration, action, and effect of the second embodiment that are not specifically described are the same as those of the first embodiment, and only the differences from the first embodiment will be described below.

[0066] Fig. 5 is a partially enlarged view showing the sealing configuration with the sealing member provided. Fig. 5 shows the state in which the heat sink 14 and the flow path forming member 13 are joined together and the joint and the gasket receiving portion 17 are filled with the sealing member. As shown in Fig. 5, the gasket receiving portion 17 stores a dried liquid gasket that is integrated with the liquid gasket that seals the joint and covers the outside of the enclosure wall.

[0067] 5 is a vertical wall portion extending from the heat sink 14 toward the flow path forming member 13. The surrounding wall 13b is a ring-shaped wall portion extending downward. The tip end of the surrounding wall 13b is the lower end portion of the surrounding wall 13b.

[0068] The base end of the surrounding wall 13b corresponds to the root of the surrounding wall 13b, which is the portion that begins to slope downward from the same height as the first bonding surface 13a that forms the bond. The flow path forming member 13 has a wall surface that extends downward along the surrounding wall 13b from a corner 14c1 that corresponds to the end of the second bonding surface 16 that forms the bond. This wall surface is shaped so that it moves downward from the corner 14c1 toward the cooling flow path 140.

[0069] The extension receiving portion 17c extends downward along the surrounding wall 13b away from the base end receiving portion 17a. The tip end receiving portion 17b faces downward from the tip of the surrounding wall 13b. The tip end receiving portion 17b is a gap that connects to the extension receiving portion 17c below the surrounding wall 13b and is adjacent to the cooling channel 140.

[0070] The gasket receiving portion 17 has a shape that extends downward and then laterally from the area adjacent to the joint to the area adjacent to the cooling channel 140. With this configuration, the gasket receiving portion 17 is formed so that the liquid gasket that protrudes from the joint spreads downward.

[0071] According to the second embodiment, the gasket receiving portion 17 extends downward relative to the joint portion along the side wall of the surrounding wall 13b. This configuration allows the liquid gasket to easily spill out of the joint portion due to gravity. Therefore, even if the volume of the gasket receiving portion 17 is small, the gasket can be distributed throughout the entire gasket receiving portion 17. This reduction in the volume of the gasket receiving portion 17 contributes to shortening the distance from the semiconductor device 90 to the capacitor.

[0072] Other Embodiments The disclosure of this specification is not limited to the exemplified embodiments. The disclosure encompasses the exemplified embodiments and modifications thereto by those skilled in the art. For example, the disclosure is not limited to the combinations of parts and elements shown in the embodiments, and can be implemented in various modifications. The disclosure can be implemented in various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure encompasses the omission of parts and elements from the embodiments. The disclosure encompasses the substitution or combination of parts and elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is defined by the claims, and should be interpreted as including all modifications within the meaning and scope of the claims.

[0073] In the above-described embodiment, the gasket receiving portion 17 has a shape that varies in cross-sectional area from the area adjacent to the bond to the area adjacent to the cooling channel 140. However, a power converter that achieves the objectives described herein may also include a gasket receiving portion with a cross-sectional area that does not vary significantly or is constant.

[0074] (Disclosure of Technical Ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be described in a multiple dependent form, with the subsequent clause alternatively referring to the preceding clause. Furthermore, some clauses may be described in a multiple dependent form, with the subsequent clause referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0075] a heat sink (14) having a plurality of fins (14a) through which heat generated by the semiconductor device is transferred; a flow path forming member (13) joined to the heat sink at a location closer to the semiconductor device than the capacitor, forming a joint (13a, 16) through which a liquid gasket is interposed, and forming a cooling flow path (140) between the heat sink and the plurality of fins; an enclosure wall (13b) provided inside the joint and outside the cooling flow path; and a gasket receiving portion (17) provided inside the joint and outside the enclosure wall, integral with the liquid gasket interposed at the joint, covering the outside of the enclosure wall, and storing dried liquid gaskets.

[0076] (Technical Idea 2) The power conversion device according to Technical Idea 1, wherein the gasket receiving portion includes a base end receiving portion (17a) adjacent to the base end of the surrounding wall and connected to the joint, an extension receiving portion (17c) extending along the surrounding wall away from the base end receiving portion, and a tip end receiving portion (17b) connected to the extension receiving portion and facing the tip end of the surrounding wall.

[0077] (Technical Concept 3) The power converter according to Technical Concept 2, wherein the tip-side receiving portion has a shape larger in cross-sectional area than the extension receiving portion.

[0078] (Technical Concept 4) The power converter according to Technical Concept 2 or 3, wherein the tip-side receiving portion has a shape in which the cross-sectional area increases as it approaches the cooling flow path.

[0079] (Technical Concept 5) The power conversion device according to any one of Technical Concepts 2 to 4, wherein the extension receiving portion has a shape that extends upward relative to the joint portion along a side wall of the enclosure wall.

[0080] (Technical Concept 6) The power converter according to any one of Technical Concepts 2 to 4, wherein the gasket receiving portion has a shape that extends downward relative to the joint portion along a side wall of the enclosure wall.

[0081] (Technical Idea 7) A power conversion device described in any one of Technical Ideas 1 to 6, wherein the dimension of the gap between the fin closest to the surrounding wall and the surrounding wall among the multiple fins is formed to be equal to or smaller than the outer dimension of the fin with the smallest outer dimension.

[0082] (Technical Idea 8) The power conversion device according to any one of Technical Ideas 1 to 7, further comprising a fixing device (15) that fixes the heat sink and the flow path forming member together at a position outside the surrounding wall.

[0083] (Technical Idea 9) A power conversion device described in any one of Technical Ideas 1 to 8, wherein the capacitor is arranged over a range that includes the semiconductor device and the heat sink in the stacking direction of the stacked semiconductor device and the heat sink.

Claims

1. A power conversion device comprising: a semiconductor device (90) that converts power input from a power source (2) and supplies current to an electrical load (3); a capacitor (5) connected to the semiconductor device; a heat sink (14) having a plurality of fins (14a) through which heat generated by the semiconductor device is transmitted; a flow path forming member (13) that is joined to the heat sink at a location closer to the semiconductor device than the capacitor to form a joint (13a, 16) through which a liquid gasket is interposed and that forms a cooling flow path (140) between the heat sink and the plurality of fins; an enclosure wall (13b) that is provided inside the joint and outside the cooling flow path; and a gasket receiving portion (17) that is provided inside the joint and outside the enclosure wall, that is integral with the liquid gasket interposed at the joint, that covers the outside of the enclosure wall, and that stores dried liquid gaskets.

2. A power conversion device as described in claim 1, wherein the gasket receiving portion includes a base end receiving portion (17a) adjacent to the base end of the surrounding wall and connected to the joint, an extended receiving portion (17c) extending along the surrounding wall away from the base end receiving portion, and a tip end receiving portion (17b) connected to the extended receiving portion and facing the tip end of the surrounding wall.

3. The power conversion device according to claim 2, wherein the tip-side receiving portion has a cross-sectional area larger than that of the extension receiving portion.

4. A power conversion device according to claim 2 or 3, wherein the tip-side receiving portion has a shape in which the cross-sectional area increases as it approaches the cooling flow path.

5. The power conversion device according to claim 2, wherein the extension receiving portion is shaped to extend upward relative to the joint portion along the side wall of the enclosure wall.

6. The power conversion device according to claim 2, wherein the gasket receiving portion is shaped to extend downward relative to the joint portion along the side wall of the enclosure wall.

7. A power conversion device as described in claim 1, wherein the dimension of the gap between the fin closest to the surrounding wall and the surrounding wall is formed to be equal to or smaller than the outer dimension of the fin with the smallest outer dimension.

8. A power conversion device according to any one of claims 1 to 3, further comprising a fixing device (15) for fixing the heat sink and the flow path forming member together at a position outside the surrounding wall.

9. A power conversion device as described in any one of claims 1 to 3, wherein the capacitor is arranged over a range that includes the semiconductor device and the heat sink in the stacking direction of the stacked semiconductor device and the heat sink.

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