Cooling device of inverter

Abstract

To efficiently cool an inverter.SOLUTION: An inverter 10 is provided with power modules 11, 12, and 13 housed in a casing 14; and a cooling device 20 for cooling the power modules 11, 12, and 13. The inverter 10 comprises: a refrigerant passage 22 through which a refrigerant flows; and a pump 21 for supplying the refrigerant to the refrigerant passage 22. The refrigerant passage 22 has: a first refrigerant passage 23 which passes through the inside of the casing 14; a second refrigerant passage 24 which passes through a side closer to the power modules 11, 12, and 13 than the first refrigerant passage 23 inside the casing 14; and a connection passage 25 which allocates a portion of the refrigerant in the first refrigerant passage 23 to the second refrigerant passage 24. A cross section of the first refrigerant passage 23 decreases from the upstream to the downstream, starting at a branching point from the connection passage 25.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling device for an inverter used in an electric vehicle. [Background technology]

[0002] In electric vehicles equipped with a motor as a driving source, the motor is driven by electricity stored in a battery or electricity generated while the vehicle is traveling. The motor also functions as a generator to generate regenerative power, mainly during coasting. This motor is controlled through an inverter.

[0003] Inverters mounted on electric vehicles are cooled by a refrigerant such as water, as shown in Patent Document 1. In particular, it is important to keep the inverter within an appropriate temperature range because the power module (power semiconductor) mounted on the inverter plays a role in passing current, i.e., outputting torque, within a range that does not exceed a predetermined upper limit temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-88180 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, inverters for electric vehicles (EVs) that do not have an engine as a driving source are composed of an MCU (Motor Control Unit) for driving the motor. In addition, in hybrid vehicles (HVs / PHEVs) that have an engine and a motor as a driving source, a GCU (Generator Control Unit) for driving the generator is installed alongside the MCU for driving the motor as a power module located within the inverter, and if a voltage step-up mechanism is included, a VCU (Voltage Control Unit) is also installed.

[0006] Temperature differences can occur in different locations within the inverter installed in hybrid vehicles (HV / PHEV). One reason for this is that the temperature of the refrigerant used to cool the inverter gradually increases as it moves from the upstream to the downstream side within the inverter. In order for the inverter to perform as expected, it is desirable for the inverter to be cooled efficiently at all times.

[0007] Therefore, an object of the present invention is to efficiently cool the inverter. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs an inverter having a power module housed in a casing and a cooling device that cools the power module, the inverter including a refrigerant passage through which a refrigerant flows and a pump that supplies the refrigerant to the refrigerant passage, the refrigerant passage including a first refrigerant passage that passes through the casing, a second refrigerant passage that passes through the casing on a side closer to the power module than the first refrigerant passage, and a connecting passage that distributes a portion of the refrigerant in the first refrigerant passage to the second refrigerant passage, the cross-sectional area of ​​the first refrigerant passage decreasing from the upstream side to the downstream side at a branch point with the connecting passage (Configuration 1).

[0009] In the configuration 1, a configuration can be adopted in which the cross-sectional area of ​​the second refrigerant passage increases from the upstream side to the downstream side at the junction with the connecting passage (configuration 2).

[0010] In the configuration 1 or 2, the second refrigerant passage faces a cooling fin provided on the power module side, and a configuration can be adopted in which the protruding height of the cooling fin into the second refrigerant passage increases from the upstream side to the downstream side at the junction with the connecting passage (configuration 3).

[0011] In any one of configurations 1 to 3, the second refrigerant passage faces a cooling fin provided on the power module side, and a gap between the protruding end of the cooling fin and the inner surface of the second refrigerant passage can be configured to narrow from the upstream side to the downstream side at the junction with the connecting passage (configuration 4).

[0012] Also, an electric vehicle can be employed that includes a drive motor and a generator, and the inverter according to any one of configurations 1 to 4, in which the power module in the casing includes, in order from upstream to downstream along the flow direction of the refrigerant passage, a voltage control unit that controls the voltage supplied to the drive motor, a motor control unit that controls the rotation of the drive motor, and a generator control unit that controls power generation by the generator, and the connecting passage includes an upstream connecting passage that joins the second refrigerant passage between the voltage control unit and the motor control unit, and a downstream connecting passage that joins the second refrigerant passage between the motor control unit and the generator control unit (configuration 5). [Effects of the Invention]

[0013] According to the present invention, the inverter can be cooled efficiently. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an overall view schematically illustrating a vehicle equipped with an inverter and a cooling device therefor according to an embodiment of the present invention; [Figure 2] FIG. 1 is a schematic diagram illustrating a cooling device for an inverter according to an embodiment. [Figure 3] FIG. 3 is a plan view of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described with reference to the drawings. This embodiment is a hybrid vehicle 1 (hereinafter referred to as vehicle 1) equipped with an inverter 10 that controls a drive motor M as a drive source for traveling, and an inverter cooling device 20 that cools the inverter 10.

[0016] As shown in Fig. 1, the vehicle 1 is a four-wheel drive vehicle equipped with a drive motor M (hereinafter referred to as motor M) and an engine 4 as drive sources for traveling, and both front wheels 2 and rear wheels 3 are driven by the motor M and the engine 4. The motor M for the front wheels 2 is referred to as a front motor 31, and the motor M for the rear wheels 3 is referred to as a rear motor 32.

[0017] The vehicle 1 also includes a battery (secondary battery) 30 that supplies power to the front motor 31 and the rear motor 32, an accelerator sensor 6 that detects the amount of depression of the accelerator pedal by the driver, a steering sensor 7 that detects the amount of steering, a vehicle speed sensor that detects the speed of the vehicle 1, and various other sensors that acquire information necessary for the running of the vehicle 1. A generator 5 that generates power using the driving force of the engine 4 is provided adjacent to the engine 4. The power generated by the generator 5 is charged into the battery 30.

[0018] The front motor 31 is directly connected to the drive shaft of the front wheels 2 without a transmission. A transmission 33 is connected to the rear motor 32, which changes the rotation speed of the rotation transmitted to the rear wheels 3. The output of the front motor 31 and the rear motor 32 is controlled by an inverter 10, which converts between direct current and alternating current. The inverter 10 also has a boost mechanism that converts power from the battery 30 to a predetermined voltage required to drive the motor M. The rotation speeds of the front motor 31 and the rear motor 32 when driven are controlled by an electronic control unit 40 via the inverter 10 in response to input from the driver. The electronic control unit 40 also controls the gear shifting operation by the transmission 33 based on the vehicle speed, the amount of accelerator depression, etc. These controls are performed by a driving control unit 41 in the electronic control unit 40.

[0019] The vehicle 1 is set to three driving modes: an electric driving mode (hereinafter referred to as EV mode) in which the vehicle runs solely on the driving force of the motor M; a series driving mode in which the vehicle runs solely on the driving force of the motor M while generating electricity with the generator 5; and a parallel driving mode in which the engine 4 and the motor M are used as the driving source for running. The driving control unit 41 selects the optimal driving mode depending on the state and driving condition of the vehicle 1 at that time, the driver's requests, etc. The motor M, the engine 4, etc. are controlled depending on the selected driving mode.

[0020] As shown in FIG. 1, the inverter 10 includes, within a casing 14, power modules including a VCU 11 (Voltage Control Unit 11) for controlling the boosting by the boost mechanism, an MCU 12 (Motor Control Unit 12) for controlling the driving of the motor M, and a GCU 13 (Generator Control Unit 13) for controlling the driving of the generator 5.

[0021] The inverter cooling device 20 (hereinafter referred to as the cooling device 20) includes a refrigerant passage 22 connected to the casing 14 and a pump 21 that sends out refrigerant to the refrigerant passage 22. The refrigerant is supplied into the casing 14 by the pump 21, causing heat to be absorbed from the internal power module and the heat absorbed by the refrigerant to be released to the outside. The heat is released to the outside by a heat dissipation unit (not shown), such as a radiator, provided midway through the refrigerant passage 22. A valve device for adjusting the flow rate may be provided at an appropriate position in the refrigerant passage 22 as needed. The pump 21 and the valve device are controlled by an inverter cooling control unit 42 provided in the electronic control unit 40. In the embodiment, water is used as the refrigerant, but various fluid refrigerants, such as other liquids such as oil, or gases, may also be used.

[0022] The present invention is based on the idea of ​​efficiently cooling the inverter by changing the cross section of the refrigerant passage in the casing 14 that houses the power module from the upstream side to the downstream side.

[0023] In this embodiment, the VCU 11, MCU 12, and GCU 13 are housed in a single casing 14. The vehicle 1 has a boost mechanism, and therefore the VCU 11 is used frequently. The MCU 12 is used only when the motor M is driven, and the GCU 13 is used only when the generator 5 is driven. For this reason, the VCU 11, MCU 12, and GCU 13 are arranged in this order from upstream to downstream along the refrigerant flow direction within the casing 14.

[0024] The casing 14 has two openings that serve as an inlet and an outlet for the refrigerant. Each opening has a nipple, and a pipe for supplying the refrigerant is connected to each opening, forming part of the refrigerant passage 22. In the refrigerant passage 22, an upstream passage 22a extending from the pump 21 is connected to one opening X of the casing 14, and after passing through refrigerant passages 23 and 24 within the casing 14, the refrigerant returns to the pump 21 via a downstream passage 22b extending from the other opening Y.

[0025] 2 and 3, the refrigerant passage 22 in the casing 14 connects one opening X to the other opening Y. The shortest path connecting one opening X and the other opening Y is a line that connects the diagonal of the casing 14, which is rectangular in plan view.

[0026] Furthermore, the refrigerant passage 22 in the casing 14 includes a first refrigerant passage 23 that passes through the casing 14 from one opening X on the upstream side toward the other opening Y on the downstream side, a second refrigerant passage 24 that passes through the casing 14 on a side closer to the power module than the first refrigerant passage 23, and a connecting passage 25 that distributes a portion of the refrigerant in the first refrigerant passage 23 to the second refrigerant passage 24. In FIG. 3 , symbol A indicates the cooling section A of the VCU 11, symbol B indicates the cooling section B of the MCU 12, and symbol C indicates the cooling section C of the GCU 13. The second refrigerant passage 24 is close to the power module and is therefore in an environment where the refrigerant temperature is likely to rise. However, since the low-temperature refrigerant on the first refrigerant passage 23 side is supplied to a midstream portion of the second refrigerant passage 24 through the connecting passage 25, a high cooling effect can be achieved not only for the upstream side but also for the midstream and downstream side power modules.

[0027] In this embodiment, the VCU 11, MCU 12, and GCU 13 are provided in this order from upstream to downstream inside the casing 14, and the connecting passage 25 includes an upstream connecting passage 25a that merges with the second refrigerant passage 24 between the VCU 11 and the MCU 12, and a downstream connecting passage 25b that merges with the second refrigerant passage 24 between the MCU 12 and the GCU 13. This allows for a high cooling effect to be exerted on the MCU 12 and the GCU 13 as well.

[0028] The cross-sectional area of ​​first refrigerant passage 23 decreases from the upstream side to the downstream side at the branch point with connection passage 25. In this embodiment, two connection passages 25 are provided, an upstream connection passage 25a and a downstream connection passage 25b, and therefore the cross-sectional area of ​​first refrigerant passage 23 decreases from the upstream side to the downstream side at the branch point with upstream connection passage 25a and the branch point with downstream connection passage 25b. This makes it easier for the refrigerant in first refrigerant passage 23 to be guided toward connection passage 25.

[0029] In FIG. 2, the first refrigerant passage 23 is divided into an upstream section 23a upstream of the branch point with the upstream connecting passage 25a, a midstream section 23b between the branch point with the upstream connecting passage 25a and the branch point with the downstream connecting passage 25b, and a downstream section 23c downstream of the branch point with the downstream connecting passage 25b. The heights of the upstream section 23a, midstream section 23b, and downstream section 23c gradually decrease in the order of v1, v2, and v3. That is, v1 > v2 > v3 holds. The upstream section 23a, midstream section 23b, and downstream section 23c each have a predetermined width L1 in the depth direction shown in FIG. 2 (see the vertical length L1 shown in FIG. 3). Therefore, the cross-sectional areas Sa, Sb, and Sc of the upstream section 23a, midstream section 23b, and downstream section 23c in a cross section perpendicular to the flow direction gradually decrease downstream, such that Sa > Sb > Sc.

[0030] The cross-sectional area of ​​the second refrigerant passage 24 increases from the upstream side to the downstream side at the junction with the connecting passage 25. In this embodiment, the connecting passage 25 includes two connecting passages, an upstream connecting passage 25a and a downstream connecting passage 25b, so the cross-sectional area of ​​the second refrigerant passage 24 increases from the upstream side to the downstream side at the junction with the upstream connecting passage 25a and the junction with the downstream connecting passage 25b. This makes it easier for the refrigerant in the connecting passage 25 to merge with the second refrigerant passage 24.

[0031] In FIG. 2, the second refrigerant passage 24 is divided such that the upstream side of the branch point with the upstream connection passage 25a is the upstream portion 24a, the middle portion between the branch point with the upstream connection passage 25a and the branch point with the downstream connection passage 25b is the middle portion 24b, and the downstream side of the branch point with the downstream connection passage 25b is the downstream portion 24c. The heights of the upstream portion 24a, the middle portion 24b, and the downstream portion 24c gradually increase in the order of h1 + w1, h2 + w2, h3 + w3 for the passage height. That is, (h1 + w1) < (h2 + w2) < (h3 + w3) holds. Note that the upstream portion 24a, the middle portion 24b, and the downstream portion 24c are formed with a predetermined width L1 in the depth direction shown in FIG. 2 (refer to the vertical length L1 shown in FIG. 3). Therefore, the cross-sectional areas Ta, Tb, Tc in the cross-section orthogonal to the flow direction in each passage of the upstream portion 2, the middle portion 24b, and the downstream portion 24c gradually increase as Ta < Tb < Tc toward the downstream side.

[0032] When the cross-sectional areas in the cross-section orthogonal to the flow direction in each passage of the upstream connection passage 25a and the downstream connection passage 25b are Ua and Ub, respectively, Sa - Sb = Ua Sb - Sc = Ub Tb - Ta = Ua Tc - Tb = Ub This is effective in ensuring a smooth flow of the refrigerant. The upstream connection passage 25a and the downstream connection passage 25b are each formed with a predetermined width L2 in the depth direction shown in FIG. 2 (refer to the vertical length L2 shown in FIG. 3). Here, the flow direction in each passage refers to the left-right direction (longitudinal direction) of the rectangular casing 14 shown in FIG. 3, not the diagonal direction in the plan view of the rectangular casing 14 shown in FIG. 3. Therefore, the cross-section orthogonal to the flow direction corresponds to the cross-section in the depth direction of FIG. 2, that is, the vertical direction in FIG. 3 (the width direction orthogonal to the longitudinal direction of the casing 14).

[0033] The flow directions of the upstream connection passage 25a and the downstream connection passage 25b are in a diagonal direction (refer to arrow R in Fig. 2) approaching the second refrigerant passage 24 as they go downstream with respect to the flow directions of the first refrigerant passage 23 and the second refrigerant passage 24 (refer to arrows P and Q in Fig. 2), which is effective in ensuring smooth flow of the refrigerant as well.

[0034] Also, since the second refrigerant passage 24 faces the cooling fins 11a, 12a, and 13a provided on the power module side, it can be said that the cooling effect of the power module by supplying the refrigerant with a lower temperature in the first refrigerant passage 23 to the middle part of the second refrigerant passage 24 is high. In particular, the flow of the refrigerant merged from the connection passage 25 heads toward the power module side and hits the end part on the root side (the upper side in Fig. 2) of the cooling fins 12a and 13a, so that the effect of pulling away the refrigerant with an increased temperature from the inner surface on the power module side can also be expected.

[0035] Moreover, the protruding height of the cooling fins 11a, 12a, and 13a into the second refrigerant passage 24 changes at the confluence point with the connection passage 25, and the protruding height gradually increases in the order of h1, h2, and h3 from the upstream side to the downstream side. That is, h1 < h2 < h3 holds. For this reason, the cooling performance for the power module on the downstream side where the temperature of the refrigerant tends to increase is enhanced.

[0036] Furthermore, the gap between the protruding side ends of the cooling fins 11a, 12a, and 13a and the inner surface of the second refrigerant passage 24 facing them changes at the confluence point with the connection passage 25, and the gap gradually narrows in the order of w1, w2, and w3 from the upstream side to the downstream side. That is, w1 > w2 > w3 holds. For this reason, the cooling performance for the power module is enhanced by increasing the flow velocity of the refrigerant on the downstream side where the temperature of the refrigerant tends to increase.

[0037] In the above embodiment, the protruding heights h1, h2, and h3 of the cooling fins 11a, 12a, and 13a and the gaps w1, w2, and w3 between the protruding ends of the cooling fins 11a, 12a, and 13a and the inner surface of the second refrigerant passage 24 are constant within each of the cooling sections A, B, and C, respectively. However, these may be varied within each of the cooling sections. For example, the protruding heights h1, h2, and h3 of the cooling fins 11a, 12a, and 13a may be increased toward the downstream side within each of the cooling sections. Furthermore, the gaps w1, w2, and w3 between the protruding ends of the cooling fins 11a, 12a, and 13a and the inner surface of the second refrigerant passage 24 may be increased toward the downstream side within each of the cooling sections.

[0038] In the embodiment, the cooling fins 11a, 12a, and 13a are cylindrical, but various modifications can be made to the shape, size, spacing, arrangement, etc. of the cooling fins 11a, 12a, and 13a depending on the specifications. For example, the cooling fins 11a, 12a, and 13a may be shaped like a prism, a truncated pyramid, or a truncated cone, or may have a protrusion extending along the longitudinal direction of the casing 14 or a protrusion extending along the width direction of the casing 14.

[0039] In the above embodiment, the configuration of the present invention has been described using as an example the inverter 10 in which all of the power modules, the VCU 11, the MCU 12, and the GCU 13, are housed in one casing 14, but the manner in which the power modules are housed in the casing 14 is not limited to the above embodiment. For example, the present invention may be applied to a casing 14 that houses only the VCU 11, a casing 14 that houses only the MCU 12, a casing 14 that houses only the GCU 13, or a casing 14 that houses a plurality of power modules selected from the VCU 11, the MCU 12, and the GCU 13.

[0040] In each of the above embodiments, a hybrid vehicle is assumed as the vehicle 1, but the hybrid vehicle may be a plug-in hybrid car in which the battery 50 can be charged directly (external charging) using a plug from a household outlet or the like, or the battery 50 can supply power directly to household electrical appliances or the like (external power supply) using a plug. The present invention can also be applied to an electric vehicle (EV) that does not have an engine 4 and has only a motor M as a driving source for traveling. [Explanation of symbols]

[0041] 1 vehicle 4 Engine 5. Generator 10 Inverter 11 Voltage Control Unit (VCU) 11a Cooling fin 12 Motor Control Unit (MCU) 12a Cooling fin 13 Generator Control Unit (GCU) 13a Cooling fin 14 Casing 20 Cooling device 21 Pump 22 Refrigerant passage 23 First refrigerant passage 24 Second refrigerant passage 25 Connecting Passage 25a Upstream connecting passage 25b Downstream connecting passage M Drive motor (motor)

Claims

1. An inverter including a power module housed in a casing and a cooling device for cooling the power module, a refrigerant passage through which a refrigerant flows, and a pump that supplies the refrigerant to the refrigerant passage; the refrigerant passage includes a first refrigerant passage that passes through the casing, a second refrigerant passage that passes through the casing on a side closer to the power module than the first refrigerant passage, and a connecting passage that distributes a portion of the refrigerant from the first refrigerant passage to the second refrigerant passage, and a cross-sectional area of ​​the first refrigerant passage decreases from the upstream side to the downstream side at a branch point with the connecting passage.

2. 2. The inverter according to claim 1, wherein a cross-sectional area of ​​the second refrigerant passage increases from an upstream side to a downstream side at a junction with the connecting passage.

3. 2. The inverter according to claim 1, wherein the second refrigerant passage faces a cooling fin provided on the power module side, and a protruding height of the cooling fin into the second refrigerant passage increases from an upstream side to a downstream side of a junction with the connecting passage.

4. 2. The inverter according to claim 1, wherein the second refrigerant passage faces a cooling fin provided on the power module side, and a gap between a protruding end of the cooling fin and an inner surface of the second refrigerant passage narrows from an upstream side to a downstream side at a junction with the connecting passage.

5. An electric vehicle comprising a drive motor and a generator, and the inverter according to any one of claims 1 to 4, the power module in the casing includes, in order from upstream to downstream along the flow direction of the refrigerant passage, a voltage control unit that controls voltage supplied to the drive motor, a motor control unit that controls rotation of the drive motor, and a generator control unit that controls power generation by the generator; the connecting passage includes an upstream connecting passage that merges with the second refrigerant passage between the voltage control unit and the motor control unit, and a downstream connecting passage that merges with the second refrigerant passage between the motor control unit and the generator control unit.

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