Inverter

Abstract

Provided is an inverter comprising a plurality of semiconductor elements, a bus bar connected to the semiconductor elements, and a cooler for cooling the semiconductor elements. The cooler of the inverter is provided with: a substrate on which the semiconductor elements are placed and to which the bus bar is fixed with an insulating material interposed therebetween; and a refrigerant path that is provided on a surface of the substrate opposite from the surface to which the bus bar is fixed and has a refrigerant for cooling the semiconductor elements flowing therethrough. The plurality of semiconductor elements include a semiconductor element of an upper arm connected to the positive electrode of a power supply and each phase of a motor, and a semiconductor element of a lower arm connected to the negative electrode of the power supply and each phase of the motor. The bus bar includes an upper arm bus bar connecting the positive electrode of the power supply and the semiconductor element of the upper arm, and a lower arm bus bar connecting the negative electrode and the semiconductor element of the lower arm. The plurality of semiconductor elements are arranged in a row in the flow direction of the refrigerant for each semiconductor element of the upper arm and the lower arm, which are connected in phase on the substrate. The semiconductor of the upper arm and the semiconductor of the lower arm are arranged so as to be offset in the direction orthogonal to the flow direction of the refrigerant.

Description

inverter

[0001] The present invention relates to an inverter.

[0002] Bus bars, which connect semiconductor elements used in power converters (inverters) to motors and smoothing capacitors, tend to generate more heat and lose more power as continuous output increases and components become smaller. One solution to this problem is to cool the bus bars with a cooler, but this method poses the problem of increased inductance due to the longer bus bars needed to accommodate the cooler. Furthermore, the longer bus bars can result in larger equipment.

[0003] JP 4138612B2 discloses a power converter in which a pair of semiconductor elements, one of which is inverted, is arranged on both sides of a plurality of stacked bus bars. In this power converter, the collector terminals and emitter terminals of the two semiconductor elements are overlapped and connected to a bus bar arranged between the two semiconductor elements. By overlapping the terminals of the bus bar and the semiconductor elements in this way, the wiring is shortened, thereby reducing the size (space) of the power converter and reducing inductance.

[0004] The power conversion device described in JP4138612B2 can reduce the inductance of the wiring and save space for the device, but does not take into consideration the cooling of the bus bar, so there is a risk that the bus bar and semiconductor elements cannot be cooled efficiently.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide an inverter that can efficiently cool bus bars and semiconductor elements while realizing reduced inductance and space saving.

[0006] According to one aspect of the present invention, there is provided an inverter for controlling a motor, the inverter including: a plurality of semiconductor elements; bus bars connected to the semiconductor elements; and a cooler for cooling the semiconductor elements. The cooler includes a substrate on which the semiconductor elements are mounted and to which the bus bars are fixed via an insulating material; and a coolant path provided on a surface of the substrate opposite to the surface to which the bus bars are fixed, through which a coolant for cooling the semiconductor elements flows. The plurality of semiconductor elements include three upper-arm semiconductor elements connected to a positive electrode of a power supply and to the U-phase, V-phase, and W-phase of a motor, respectively, and three lower-arm semiconductor elements connected to a negative electrode of the power supply and to the U-phase, V-phase, and W-phase of the motor, respectively. The bus bars include an upper-arm bus bar connecting the positive electrode of the power supply and the upper-arm semiconductor elements, and a lower-arm bus bar connecting the negative electrode of the power supply and the lower-arm semiconductor elements. Furthermore, the multiple semiconductor elements are arranged on the substrate in a row in the direction of coolant flow, with each upper arm and lower arm semiconductor element connected to the same phase of the motor, and the upper arm semiconductor and the lower arm semiconductor are arranged offset in a direction perpendicular to the coolant flow direction.

[0007] Fig. 1 is a schematic circuit diagram of a vehicle system including an inverter according to an embodiment of the present invention. Fig. 2 is a schematic configuration diagram of the inverter. Fig. 3 is a diagram showing a connection configuration of semiconductor elements. Fig. 4 is a schematic diagram explaining wiring lengths depending on the arrangement of semiconductor elements. Fig. 5 is a diagram showing the arrangement and shape of bus bars. Fig. 6 is a diagram showing welding points between bus bars and terminals of a smoothing capacitor and output terminals of a motor. Fig. 7 is a diagram showing welding points according to a modified example.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] 1 is a schematic circuit diagram of a vehicle system 100 including an inverter 1 according to an embodiment of the present invention. The vehicle system 100 is mounted on, for example, an electric vehicle. Note that the electric vehicle referred to here includes not only a battery electric vehicle (BEV) but also a hybrid electric vehicle (HEV) and the like.

[0010] As shown in FIG. 1, a vehicle system 100 includes an inverter 1, a motor 2, a power supply 3, a smoothing capacitor 4, relays 5, 6, and 7, a controller 8, and the like.

[0011] As shown in Fig. 1, the inverter 1 is connected between a power source 3 such as a battery and a motor 2, and includes a plurality of parallel circuits each consisting of semiconductor elements 11 (11UP, 11VP, 11WP, 11UN, 11VN, 11WN) that are switching elements and a diode D. A smoothing capacitor 4 is provided in parallel between the inverter 1 and the power source 3. The inverter 1 converts DC power and AC power mutually by the switching operation of the semiconductor elements 11 (11UP, 11VP, 11WP, 11UN, 11VN, 11WN).

[0012] The semiconductor elements 11 are provided between a positive line 31 connected to the positive electrode of the power supply 3 and a negative line 32 connected to the negative electrode. The semiconductor elements 11 include semiconductor elements 11UP and 11UN connected to the U phase of the motor 2, semiconductor elements 11VP and 11VN connected to the V phase, and semiconductor elements 11WP and 11WN connected to the W phase. Each phase of the semiconductor elements 11 has two upper and lower arms. That is, the semiconductor elements 11UP, 11VP, and 11WP form the upper arm, and the semiconductor elements 11UN, 11VN, and 11WN form the lower arm.

[0013] In this embodiment, the semiconductor element 11 is a MOSFET including a drain terminal (first terminal) that is a high-potential terminal, a source terminal (second terminal) that is a low-potential terminal, and a gate terminal (third terminal) that is a control terminal, but is not limited to this and may be, for example, an IGBT, etc. A control signal is input to the gate terminal from the controller 8, and conduction between the drain terminal and the source terminal is established or cut off in response to the control signal.

[0014] The relays 5 and 6 are switch means provided on the lines (positive line 31, negative line 32) connecting the power supply 3 and the inverter 1, and connect or disconnect the power supply 3 from the inverter 1 and the motor 2. The on / off operation of the relays 5 and 6 is controlled by a controller 8. When the motor 2 is driven, the relays 5 and 6 are controlled to be on and power is supplied to the motor 2 from the power supply 3 via the inverter 1, and when the electric vehicle is stopped, the relays 5 and 6 are controlled to be off. Note that even when the electric vehicle is stopped, the relays 5 and 6 may be controlled to be on when, for example, the battery 3 serving as a power source is being charged from an external charger.

[0015] The relay 7 is a switch means provided on the line (negative line 32) connecting the neutral point of the motor 2 and the negative pole of the power supply 3. The on / off operation of the relay 7 is controlled by the controller 8. The relay 7 is normally controlled to be off, but may be controlled to be on when charging the battery 3 as a power source from an external charger, warming up the battery 3, etc. The positions and presence or absence of the switch means (relays 5, 6, 7) are not limited to the configuration in FIG. 1. For example, the relay 7 may or may not be present.

[0016] The smoothing capacitor 4 is provided in parallel between the power supply 3 and the inverter 1 (semiconductor element 11 ), and smoothes the DC power input from the power supply 3 to the inverter 1 .

[0017] The controller 8 is configured by a computer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface) and is programmed to be able to execute the processes described below. Note that the controller 8 can also be configured by multiple computer hardware that executes the processes in a distributed manner.

[0018] The controller 8 controls the opening and closing of the relays 5, 6, and 7. For example, as described above, while the electric vehicle is traveling, the controller 8 controls the relays 5 and 6 to be on and the relay 7 to be off. Furthermore, for example, while the electric vehicle is stopped, the controller 8 controls the relays 5, 6, and 7 to be off.

[0019] The controller 8 also controls the operation of the inverter 1. Specifically, the controller 8 receives the required torque of the motor 2, which is an electrical load, as an input and generates a PWM signal for defining the switching pattern (duty ratio) of each semiconductor element 11 of the inverter 1. More specifically, the controller 8 calculates a current command value (a command value for a current supplied to the inverter 1) that realizes a desired required torque according to an external load (such as the amount of operation of the accelerator pedal in the case of a vehicle), calculates a control voltage (a voltage command value) that eliminates the deviation between the current command value and the actual current of the motor 2, and generates a PWM signal to realize the calculated voltage command value. The controller 8 outputs the generated PWM signal to the inverter 1. As a result, the inverter 1 operates based on the PWM signal, a voltage according to the voltage command value is applied to the motor 2, and a current according to the current command value flows through each phase of the motor 2.

[0020] Fig. 2 is a schematic diagram of the inverter 1, and is a top view of the inverter 1. Fig. 3 is a diagram showing the connection configuration of the semiconductor element 11, and is a cross-sectional view of the semiconductor element 11 as seen from the direction of the arrow in Fig. 2.

[0021] 2 and 3, the inverter 1 includes a plurality of semiconductor elements 11 (11UP, 11VP, 11WP, 11UN, 11VN, and 11WN), bus bars 12 (121 and 122) connected to the semiconductor elements 11, and a cooler 13 that cools the semiconductor elements 11. Although not shown, the inverter 1 is housed in an inverter case.

[0022] As described above, the multiple semiconductor elements 11 include three upper arm semiconductor elements 11UP, 11VP, 11WP (hereinafter collectively referred to as upper arm semiconductor element 11P) connected to the positive pole of the power supply 3 and the U phase, V phase, and W phase of the motor 2, respectively, and three lower arm semiconductor elements 11UN, 11VN, 11WN (hereinafter collectively referred to as lower arm semiconductor element 11N) connected to the negative pole of the power supply and the U phase, V phase, and W phase of the motor, respectively.

[0023] 3 , the bus bar 12 is disposed so as to contact the underside of the semiconductor element 11. The bus bar 12 includes an upper arm bus bar that connects the positive electrode of the power supply 3 to each of the upper arm semiconductor elements 11UP, 11VP, and 11WP and the motor 2, and a lower arm bus bar that connects the negative electrode of the power supply 3 to each of the lower arm semiconductor elements 11UN, 11VN, and 11WN and the motor 2. The upper arm bus bar and the lower arm bus bar each include a first bus bar 121 that connects the terminals 41 (41P, 41N) of the smoothing capacitor 4 to the semiconductor element 11, and a second bus bar 122 that connects the upper and lower arm semiconductor elements 11P and 11N that are connected to the same phase of the motor 2 to the output terminals 21 (21U, 21V, 21W) of the motor 2.

[0024] 2 , the first bus bar 121 includes a P bus bar 121P that connects the semiconductor elements 11UP, 11VP, and 11WP of the upper arm to a P terminal (positive terminal) 41P of the smoothing capacitor 4, and an N bus bar 121N that connects the semiconductor elements 11UN, 11VN, and 11WN of the lower arm to an N terminal (negative terminal) 41N of the smoothing capacitor 4. The second bus bar 122 includes a U bus bar 122U that connects the U phase of the motor 2 to the semiconductor elements 11UP and 11UN of the upper and lower arms, a V bus bar 122V that connects the V phase of the motor 2 to the semiconductor elements 11VP and 11VN of the upper and lower arms, and a W bus bar 122W that connects the W phase of the motor 2 to the semiconductor elements 11WP and 11WN of the upper and lower arms.

[0025] The terminal 41 of the smoothing capacitor 4 and the output terminal 21 of the motor 2 are each a bus bar, and the first bus bar 121 is welded on its upper surface to the terminal (bus bar) 41 of the smoothing capacitor 4, while the second bus bar 122 is welded on its upper surface to the output terminal (bus bar) 21 of the motor 2. As shown in FIG. 3 , the thickness tc of the terminal (bus bar) 41 of the smoothing capacitor 4 and the thickness to of the output terminal (bus bar) 21 of the motor 2 are thinner than the thickness ts of the first bus bar 121 and the second bus bar 122.

[0026] The cooler 13 includes a substrate 131 on which the semiconductor element 11 is mounted and a coolant path 132 through which a coolant for cooling the semiconductor element 11 flows. The bus bars 12 (first bus bar 121 and second bus bar 122) are fixed to the surface of the substrate 131 on which the semiconductor element 11 is mounted (hereinafter also referred to as the upper surface) via an insulating material 133. Fixing the bus bars 12 to the substrate 131 of the cooler 13 cools the bus bars 12, thereby cooling the semiconductor element 11. The coolant path 132 is provided on the surface (hereinafter also referred to as the lower surface) opposite the surface (upper surface) of the substrate 131 on which the bus bars 12 are fixed. The area where the periphery of the coolant path 132 contacts the substrate 131 is sealed with a sealing member (not shown) such as an O-ring. The coolant flowing through the coolant path 132 is not particularly limited and may be, for example, cooling water or a cooling gas.

[0027] Here, the multiple semiconductor elements 11 are arranged in a row on the substrate 131, with each semiconductor element (11UP and 11UN, 11VP and 11VN, 11WP and 11WN) of the upper arm and the lower arm connected to the same phase of the motor 2 being arranged in a row. The coolant in the coolant path 132 flows in the direction in which the multiple semiconductor elements 11 are arranged, cooling each semiconductor element 11 and the bus bar 12 connected to the semiconductor elements 11. In this embodiment, the coolant flows in the direction of the arrow in FIG. 2.

[0028] Furthermore, the multiple semiconductor elements 11 are arranged such that the semiconductor elements 11P of the upper arm and the semiconductor elements 11N of the lower arm are offset in a direction perpendicular to the flow direction of the coolant in the coolant path 132. That is, the multiple semiconductor elements 11 are arranged such that the center line MP of the semiconductor element 11P of the upper arm in the flow direction of the coolant does not coincide with the center line MN of the semiconductor element 11N of the lower arm in the flow direction of the coolant. This prevents thermal interference between the semiconductor elements 11P of the upper arm and the semiconductor elements 11N of the lower arm in the coolant path 132. That is, the heat removal effect of the semiconductor elements 11 and the bus bar 12 is improved, and the cooling efficiency of the semiconductor elements 11 and the bus bar 12 is improved.

[0029] As described above, in the inverter 1, a plurality of semiconductor elements 11 are arranged in a row on the substrate 131 of the cooler 13, and the semiconductor elements 11 and the busbar 12 are cooled by flowing a refrigerant in the direction in which the semiconductor elements 11 are arranged.

[0030] Bus bars connecting semiconductor elements used in power converters (inverters) to motors and smoothing capacitors tend to generate more heat and lose more power as continuous output increases and components become smaller. One solution to this problem is to place a cooler between the semiconductor elements and the motor or smoothing capacitor to cool the bus bar. However, this method requires a longer bus bar to accommodate the cooler, which increases inductance. Furthermore, the longer bus bar length can result in a larger device.

[0031] On the other hand, shortening the bus bars (wiring) connecting the semiconductor elements to the motor and smoothing capacitor can reduce the inductance of the wiring and save space, but it makes it difficult to arrange the bus bars connecting the semiconductor elements to the motor and smoothing capacitor on the refrigerant path of the cooler. This may result in inefficient cooling of the bus bars and semiconductor elements. Furthermore, for example, if bus bars are arranged on top of each other to save space, it may be difficult to cool the bus bars.

[0032] In contrast, in the inverter 1 of this embodiment, the busbars 12 are fixed to a substrate 131 of a cooler 13 having a coolant path 132, and the semiconductor elements 11 are arranged in a row on the substrate 131 in the direction of coolant flow. The semiconductor elements 11 are arranged in pairs of upper-arm semiconductor elements 11P and lower-arm semiconductor elements 11N connected to the same phase of the motor 2, with the upper-arm semiconductor elements 11P and lower-arm semiconductor elements 11N offset in a direction perpendicular to the direction of coolant flow. In this way, the semiconductor elements 11 are arranged in a row for the upper-arm semiconductor elements 11P and lower-arm semiconductor elements 11N connected to the same phase of the motor 2. This allows the distance between the motor 2 and the semiconductor elements 11 connected to the same phase of the motor 2 to be uniform, thereby achieving uniform inductance between the phases. Furthermore, because the semiconductor elements 11 are arranged in a row on the cooler 13 (substrate 131), the semiconductor elements 11 and the busbars 12 connected to the semiconductor elements 11 can be cooled by the cooler 13 even if the busbars 12 are short. Furthermore, because the semiconductor element 11P of the upper arm and the semiconductor element 11N of the lower arm are arranged offset in a direction perpendicular to the flow direction of the refrigerant in the refrigerant path 132, thermal interference between the semiconductor element 11P of the upper arm and the semiconductor element 11N of the lower arm is suppressed in the refrigerant path 132, improving the cooling efficiency of the semiconductor element 11 and the bus bar 12. That is, the bus bar 12 can be shortened to reduce inductance and save space, while efficiently cooling the bus bar 12 and the semiconductor element 11.

[0033] The connection configuration of the semiconductor elements 11 in the inverter 1 will be described in detail below.

[0034] As described above, the semiconductor elements 11 are arranged in a row on the substrate 131 of the cooler 13, with each upper arm semiconductor element 11P and lower arm semiconductor element 11N (hereinafter also referred to as upper and lower arm semiconductor elements 11P, 11N of the same phase) connected to the same phase of the motor 2. In detail, as shown in Fig. 2, the upper arm semiconductor element 11UP and the lower arm semiconductor element 11UN, the upper arm semiconductor element 11VP and the lower arm semiconductor element 11VN, and the upper arm semiconductor element 11WP and the lower arm semiconductor element 11WN are arranged in a row in the direction of refrigerant flow.

[0035] The semiconductor element 11 has a collector surface on the side in contact with the substrate 131 (lower surface) and an emitter surface on the side opposite to the surface in contact with the substrate 131 (upper surface), and has a terminal 111 at one end in the longitudinal direction of the semiconductor element 11. The terminal 111 includes a collector 111A, an emitter 111B, and a gate 111C. As shown in FIG. 2 , the terminal 111 of each semiconductor element 11 is arranged so as to be perpendicular to the direction of refrigerant flow, and the upper and lower arm semiconductor elements 11P, 11N of the same phase are arranged so that the upper arm semiconductor element 11P and the lower arm semiconductor element 11N are rotated 180° when viewed from above. The P terminal 41P of the smoothing capacitor 4 and the collector surface of the upper arm semiconductor element 11P are connected by a P bus bar 121P, and the N terminal 41N of the smoothing capacitor 4 and the emitter 111B of the terminal 111 of the lower arm semiconductor element 11N are connected by an N bus bar 121N. By arranging the upper and lower arm semiconductor elements 11P, 11N of the same phase in an inverted manner, the distance between the terminal 41 (41P, 41N) of the smoothing capacitor 4 and the semiconductor element 11 can be shortened, and the first bus bar 121 (121P, 121N) connecting the terminal 41 (41P, 41N) of the smoothing capacitor 4 and the semiconductor element 11 can be shortened. Furthermore, by arranging the upper and lower arm semiconductor elements 11P, 11N of the same phase in an inverted manner, the distance between the emitter 111B of the terminal 111 of the upper arm semiconductor element 11P, the collector surface of the lower arm semiconductor element 11N, and the output terminal 21 of the motor 2 can be shortened. Therefore, it is possible to shorten the second bus bars 122 (122U, 122V, 122W) that connect the upper and lower arm semiconductor elements 11P, 11N of the same phase to the output terminals 21 (21U, 21V, 21W) of the motor 2. In other words, it is possible to reduce the inductance due to the wiring (bus bars 12).

[0036] As described above, the semiconductor elements 11 are arranged such that the upper arm semiconductor element 11P and the lower arm semiconductor element 11N are offset in a direction perpendicular to the refrigerant flow direction of the refrigerant path 132. More specifically, among the multiple semiconductor elements 11, the center line MN of the lower arm semiconductor element 11N in the refrigerant flow direction is closer to the motor 2 than the center line MP of the upper arm semiconductor element 11P in the refrigerant flow direction. Because the lower arm semiconductor element 11N is offset toward the motor 2 (toward the U bus bar 122U, V bus bar 122V, and W bus bar 122W) relative to the upper arm semiconductor element 11P, the connection wiring (N bus bar 121N) to the N terminal 41N of the smoothing capacitor 4 is longer than when there is no offset, but the wiring to the output terminals 21 (21U, 21V, and 21W) of the motor 2 can be shortened accordingly. That is, since the total wiring (current path) from the N terminal 41N of the smoothing capacitor 4 to the output terminal 21 of the motor 2 does not change, the semiconductor element 11 can be offset without changing the total inductance. As described above, by offsetting the semiconductor element 11, thermal interference between the semiconductor element 11P of the upper arm and the semiconductor element 11N of the lower arm in the coolant path 132 is suppressed, improving the cooling efficiency of the semiconductor element 11 and the bus bar 12. That is, the cooling effect can be improved without changing the inductance of the wiring.

[0037] 4 is a schematic diagram illustrating the wiring length depending on the arrangement of the semiconductor elements 11. (a) shows a state in which the semiconductor element 11P of the upper arm and the semiconductor element 11N of the lower arm are not offset, and (b) shows a state in which the semiconductor element 11P of the upper arm is offset toward the smoothing capacitor 4 and the semiconductor element 11N of the lower arm is offset toward the motor 2.

[0038] As shown in FIG. 4, when the upper arm semiconductor element 11P is offset toward the smoothing capacitor 4 (FIG. 4(b)), the distance from the P terminal 41P of the smoothing capacitor 4 to the collector surface (bottom surface) of the upper arm semiconductor element 11P is shorter than when the upper arm semiconductor element 11P is not offset (FIG. 4(a)). Furthermore, since the bottom surface of the lower arm semiconductor element 11N is the collector surface and the terminal 111 (emitter 111B) is on the smoothing capacitor 4 side, the output terminal 21 of the motor 2 can be positioned closer to the smoothing capacitor 4 by the amount by which the upper arm semiconductor element 11P is offset. Therefore, the wiring connecting the P terminal 41P of the smoothing capacitor 4 and the upper arm semiconductor element 11P can be shortened by the amount by which the upper arm semiconductor element 11P is offset.

[0039] On the other hand, when the lower arm semiconductor element 11N is offset toward the output terminal 21 of the motor 2, the distance from the N terminal 41N of the smoothing capacitor 4 to the terminal 111 (emitter 111B) of the lower arm semiconductor element 11N becomes longer compared to when the semiconductor element 11N is not offset, but the distance from the lower arm semiconductor element 11N to the output terminal 21 of the motor 2 becomes even shorter. Therefore, the wiring connecting the terminal 41 of the smoothing capacitor 4 to the lower arm semiconductor element 11N and the wiring connecting the lower arm semiconductor element 11N to the output terminal 21 of the motor 2 can be shortened.

[0040] In this way, preferably, from a state in which the semiconductor elements 11 are not offset, the semiconductor element 11P of the upper arm is offset toward the smoothing capacitor 4, and the semiconductor element 11N of the lower arm is offset toward the motor 2. This makes it possible to shorten the length of the wiring connecting the semiconductor elements 11 to the smoothing capacitor 4 and the motor 2, and to reduce the inductance of the wiring.

[0041] In FIG. 4 , the upper-arm semiconductor element 11P is offset toward the smoothing capacitor 4, and the lower-arm semiconductor element 11N is offset toward the motor 2, compared to the state in which the semiconductor elements 11 are not offset. However, this is not necessarily limited to this. For example, from the state in which the semiconductor elements 11 are not offset, only the upper-arm semiconductor element 11P may be offset toward the smoothing capacitor 4, or only the lower-arm semiconductor element 11N may be offset toward the motor 2. Even in these cases, the total length of the wiring connecting the terminals 41 of the smoothing capacitor 4 to each semiconductor element 11 and the wiring connecting each semiconductor element 11 to the output terminals 21 of the motor 2 can be made the same as or shorter than the length of the wiring when not offset. That is, as long as the center line MN of the lower-arm semiconductor element 11N in the direction of the refrigerant flow is closer to the motor 2 than the center line MP of the upper-arm semiconductor element 11P in the direction of the refrigerant flow, the wiring length can be made shorter than when the semiconductor elements 11 are not offset. Therefore, cooling efficiency can be improved by offsetting the semiconductor elements 11 without changing or reducing the inductance of the wiring.

[0042] Fig. 5 is a diagram showing the arrangement and shape of the bus bars 12 in the inverter 1. Fig. 5 is a diagram showing the inverter 1 in a state where only the bus bars 12 and the cooler 13 are mounted.

[0043] As described above, the bus bar 12 includes a first bus bar 121 that connects the terminal 41 of the smoothing capacitor 4 to the semiconductor element 11, and a second bus bar 122 that connects the upper and lower arm semiconductor elements 11P, 11N of the same phase to the output terminal 21 of the motor 2.

[0044] As described above, the first bus bar 121 includes a P bus bar 121P that connects the semiconductor element 11P of the upper arm to the P terminal 41P of the smoothing capacitor 4, and an N bus bar 121N that connects the semiconductor element 11N of the lower arm to the N terminal (negative terminal) 41N of the smoothing capacitor 4. The second bus bar 122 includes a U bus bar 122U that connects the U phase of the motor 2 to the semiconductor elements 11UP, 11UN of the upper and lower arms, a V bus bar 122V that connects the V phase of the motor 2 to the semiconductor elements 11VP, 11VN of the upper and lower arms, and a W bus bar 122W that connects the W phase of the motor 2 to the semiconductor elements 11WP, 11WN of the upper and lower arms.

[0045] 5, the first bus bar 121 has an extension portion 1211 extending in a direction perpendicular to the refrigerant flow direction (the direction of the arrow in FIG. 5). On the other hand, the second bus bar 122 has a first extension portion 1221 extending in a direction perpendicular to the refrigerant flow direction and a second extension portion 1222 extending in the refrigerant flow direction. The first bus bars 121 are arranged so that the extension portion 1211 of the P bus bar 121P is connected to the collector surface (lower surface) of the semiconductor element 11P of the upper arm, and the extension portion 1211 of the N bus bar 121N is connected to the terminal 111 of the semiconductor element 11N of the lower arm. Furthermore, the second bus bars 122 (U bus bar 122U, V bus bar 122V, W bus bar 122W) are arranged such that the first extending portion 1221 is connected to the collector surface (lower surface) of the semiconductor element 11N of the lower arm, and the second extending portion 1222 is connected to the terminal 111 of the semiconductor element 11P of the upper arm. In this way, by combining the bus bars 12 (first bus bar 121, second bus bar 122) vertically and horizontally and arranging them in a space-efficient manner, the inverter 1 can be made space-saving, and the length of the bus bars 12 can be shortened, thereby reducing the inductance of the bus bars 12.

[0046] 6 is a diagram showing welding points between the bus bar 12 and the terminal 41 of the smoothing capacitor 4 and the output terminal 21 of the motor 2. The dashed lines in FIG.

[0047] As described above, the first bus bar 121 is welded to the terminals 41 (41P, 41N) of the smoothing capacitor 4, and the second bus bar 122 is welded to the output terminals 21 (21U, 21V, 21W) of the motor 2, respectively.

[0048] Further, the first bus bars 121 (121P, 121N) are welded to the terminals 41 (41P, 41N) of the smoothing capacitor 4 directly above the refrigerant path 132, and the second bus bars 122 (122U, 122V, 122W) are welded to the output terminals 21 (21U, 21V, 21W) of the motor 2 directly above the refrigerant path 132. That is, as shown in Fig. 6, a welding point 123 between the first bus bar 121 and the terminal 41 of the smoothing capacitor 4 and a welding point 124 between the second bus bar 122 and the output terminal 21 of the motor 2 are formed directly above the refrigerant path 132, i.e., inside the seal member.

[0049] In this way, by directly connecting the terminal 41 of the smoothing capacitor 4 to the first bus bar 121 and the output terminal 21 of the motor 2 to the second bus bar 122 by welding, the area of ​​the connection can be reduced compared to when the connection is made by bolting or the like, thereby making it possible to miniaturize the overall size of the inverter 1. Furthermore, by connecting by welding, the contact electrical resistance of the connection can be reduced. Furthermore, by arranging the connection (weld points 123, 124) directly above the coolant path 132, not only the first and second bus bars 121, 122 but also the bus bar (terminal 41) of the smoothing capacitor 4 and the bus bar (output terminal 21) of the UVW phases of the motor 2 themselves can be efficiently cooled.

[0050] As described above, the terminal (bus bar) 41 of the smoothing capacitor 4 is welded to the first bus bar 121 on the upper surface of the first bus bar 121, and the output terminal (bus bar) 21 of the motor 2 is welded to the second bus bar 122 on the upper surface of the second bus bar 122 ( FIG. 3 ). The thickness tc of the terminal (bus bar) 41 of the smoothing capacitor 4 and the thickness to of the output terminal (bus bar) 21 of the motor 2 are configured to be thinner than the thickness ts of the first bus bar 121 and the second bus bar 122.

[0051] In this way, by making the thicknesses tc and t0 of the upper bus bars (terminals 41 of the smoothing capacitor 4 and output terminals 21 of the motor 2), which are the laser irradiation surfaces during welding, thinner than the thickness ts of the lower bus bars (first bus bar 121 and second bus bar 122), it becomes easier to adjust the laser (adjust the bead depth). In addition, welding with low power becomes possible, and the occurrence of spatter, etc. can be suppressed. Therefore, the difficulty of welding itself can be reduced.

[0052] 6, the multiple welds 123 and the multiple welds 124 are formed on a straight line along the refrigerant flow direction, but this is not limited to this. For example, as shown in Fig. 7, the weld 123P between the P terminal 41P of the smoothing capacitor 4 and the P bus bar 121P and the weld 123N between the N terminal 41N of the smoothing capacitor 4 and the N bus bar 121N may be formed offset from each other in the refrigerant flow direction. This makes it easier to secure space for arranging a side nozzle that supplies assist gas, for example, when welding while applying an assist gas for preventing oxidation.

[0053] According to the inverter 1 of the present embodiment described above, the following effects can be obtained.

[0054] The inverter 1 includes bus bars 12 connected to the semiconductor elements 11, and the bus bars 12 include an upper arm bus bar connecting the positive electrode of the power supply 3 to the upper arm semiconductor elements 11UP, 11VP, and 11WP, and a lower arm bus bar connecting the negative electrode of the power supply 3 to the lower arm semiconductor elements 11UN, 11VN, and 11WN. The semiconductor elements 11 are arranged in a row in the direction of coolant flow on a substrate 131 of a cooler 13 having a coolant path 132, with the upper arm semiconductor element 11P and the lower arm semiconductor element 11N connected to the same phase of the motor 2. Furthermore, the upper arm semiconductor element 11P and the lower arm semiconductor element 11N are arranged offset in a direction perpendicular to the direction of coolant flow. In this way, the semiconductor elements 11 are arranged in a row for each of the upper arm semiconductor elements 11P and the lower arm semiconductor elements 11N connected to the same phase of the motor 2, which makes it possible to uniformly adjust the distance between the semiconductor elements 11 connected to the same phase of the motor 2 and the motor, thereby achieving uniform inductance between each phase. Furthermore, because the semiconductor elements 11 are arranged in a row on the cooler 13 (substrate 131), even if the bus bar 12 connected to the semiconductor elements 11 is short, the semiconductor elements 11 and the bus bar 12 can be cooled by the cooler 13. Furthermore, because the upper arm semiconductor elements 11P and the lower arm semiconductor elements 11N are arranged offset in a direction perpendicular to the flow direction of the coolant in the coolant path 132, thermal interference between the upper arm semiconductor elements 11P and the lower arm semiconductor elements 11N in the coolant path 132 is suppressed, thereby improving the cooling efficiency of the semiconductor elements 11 and the bus bar 12. That is, the bus bar 12 can be shortened, thereby reducing inductance and saving space, while efficiently cooling the bus bar 12 and the semiconductor element 11 .

[0055] In the inverter 1, the lower surface of the semiconductor element 11 is the collector surface, and the terminal 111 of the semiconductor element 11 has an emitter 111B, with the terminal 111 positioned perpendicular to the direction of refrigerant flow. The upper arm semiconductor element 11P and the lower arm semiconductor element 11N, which are connected in phase with the motor 2, are rotated 180 degrees when viewed from above. Furthermore, the center line MN of the lower arm semiconductor element 11N in the direction of refrigerant flow is closer to the motor 2 than the center line MP of the upper arm semiconductor element 11P in the direction of refrigerant flow. When the lower arm semiconductor element 11N is offset closer to the motor 2 than the upper arm semiconductor element 11P, the distance from the smoothing capacitor 4 to the emitter 111B of the lower arm semiconductor element 11N is longer than when the offset is not present. However, the distance from the lower arm semiconductor element 11N to the motor 2 is shorter by an even greater amount. Therefore, the total length of the wiring connecting the smoothing capacitor 4 and the lower arm semiconductor element 11N and the wiring connecting the lower arm semiconductor element 11N and the motor 2 can be shortened, and the inductance of the wiring can be reduced.

[0056] The inverter 1 includes a first bus bar 121, directly above the refrigerant path 132, whose upper surface is connected to the terminal 41 of the smoothing capacitor 4 by welding, and a second bus bar 122, directly above the refrigerant path 132, whose upper surface is connected to the output terminal 21 of the motor 2 by welding. The thicknesses tc and t0 of the terminal 41 of the smoothing capacitor 4 and the output terminal 21 of the motor 2 are thinner than the thicknesses ts of the first bus bar 121 and the second bus bar 122. By directly connecting the terminal 41 of the smoothing capacitor 4 to the first bus bar 121 and the output terminal 21 of the motor 2 to the second bus bar 122 by welding, the area of ​​the connection can be reduced compared to connections made by bolting or the like, thereby enabling the inverter 1 to be miniaturized overall. Furthermore, connecting by welding can reduce the electrical contact resistance of the connection. Furthermore, by arranging the connection parts (welding points 123, 124) directly above the refrigerant path 132, not only the first and second bus bars 121, 122, but also the bus bar (terminal 41) of the smoothing capacitor 4 and the bus bar (output terminal 21) of the UVW phase of the motor 2 themselves can be efficiently cooled.

[0057] Furthermore, by making the thickness tc, t0 of the upper bus bars (terminal 41 of smoothing capacitor 4 and output terminal 21 of motor 2), which are the laser irradiated surfaces during welding, thinner than the thickness ts of the lower bus bars (first bus bar 121 and second bus bar 122), it becomes easier to adjust the laser (adjust the bead depth). This also enables welding with low power, which can reduce the occurrence of spatter, etc., thereby reducing the difficulty of welding itself.

[0058] In the inverter 1, the first bus bar 121 extends in a direction perpendicular to the refrigerant flow direction, and the second bus bar 122 extends in the refrigerant flow direction and in a direction perpendicular to the refrigerant flow direction. In this way, by combining the bus bars 12 (the first bus bar 121 and the second bus bar 122) vertically and horizontally and arranging them in a space-efficient manner, the inverter 1 can be made space-saving, and the length of the bus bars 12 can be shortened, thereby reducing the inductance of the bus bars 12.

[0059] As in the present embodiment, it is preferable that the upper arm semiconductor element 11P and the lower arm semiconductor element 11N, which are connected to the same phase of the motor 2, are arranged rotated by 180° when viewed from above, but this is not necessarily limited to this. Even if the upper arm semiconductor element 11P and the lower arm semiconductor element 11N are arranged in the same direction, as long as the semiconductor elements 11 are arranged in a row in the direction of the refrigerant flow and offset in a direction perpendicular to the direction of the refrigerant flow, it is possible to improve cooling efficiency while saving space.

[0060] Furthermore, as in this embodiment, it is preferable that the center line MN of the lower arm semiconductor element 11N in the direction of coolant flow be closer to the motor 2 than the center line MP of the upper arm semiconductor element 11P in the direction of coolant flow, but this is not necessarily limited to this. For example, even if the center line MN of the lower arm semiconductor element 11N in the direction of coolant flow is closer to the smoothing capacitor 4 than the center line MP of the upper arm semiconductor element 11P in the direction of coolant flow, the length of the wiring can be shortened to a certain extent. Furthermore, if the semiconductor elements 11 are arranged in a row in the direction of coolant flow and offset in a direction perpendicular to the direction of coolant flow, cooling efficiency can be improved.

[0061] As in the present embodiment, the first bus bar 121 and the terminal 41 of the smoothing capacitor 4, and the second bus bar 122 and the output terminal 21 of the motor 2 are preferably welded directly above the refrigerant path 132, but this is not necessarily limited to this, and the welding locations may be determined arbitrarily. Furthermore, the first bus bar 121 and the second bus bar 122 may be connected to the terminal 41 of the smoothing capacitor 4 and the output terminal 21 of the motor 2 by a method other than welding.

[0062] Furthermore, as in the present embodiment, it is preferable that the thicknesses tc, t0 of the terminals 41 of the smoothing capacitor 4 and the output terminals 21 of the motor 2 are thinner than the thickness ts of the first bus bar 121 and the second bus bar 122, but this is not necessarily limited to this. For example, if there is no problem with heat conduction on the thickness tc, t0 side of the terminals 41 of the smoothing capacitor 4 and the output terminals 21 of the motor 2 to which heat is applied during welding, the thicknesses tc, t0 of the terminals 41 of the smoothing capacitor 4 and the output terminals 21 of the motor 2 may be equal to or greater than the thickness ts of the first bus bar 121 and the second bus bar 122.

[0063] In addition, as in the present embodiment, it is preferable that the first bus bar 121 extends in a direction perpendicular to the refrigerant flow direction, and the second bus bar 122 extends in the refrigerant flow direction and in a direction perpendicular to the refrigerant flow direction, but this is not necessarily limited to this. The first bus bar 121 and the second bus bar 122 may be disposed or shaped as desired as long as all or part of them are located on the cooler 13.

[0064] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. An inverter for controlling a motor, comprising: a plurality of semiconductor elements; bus bars connected to the semiconductor elements; and a cooler for cooling the semiconductor elements, wherein the cooler comprises a substrate on which the semiconductor elements are placed and to which the bus bars are fixed via an insulating material; and a refrigerant path provided on the surface of the substrate opposite to the surface to which the bus bars are fixed and through which a refrigerant for cooling the semiconductor elements flows, wherein the plurality of semiconductor elements include three upper arm semiconductor elements connected to the positive electrode of a power supply and the U-phase, V-phase, and W-phase of the motor, and three lower arm semiconductor elements connected to the negative electrode of the power supply and the U-phase, V-phase, and W-phase of the motor, respectively, and the bus bars include an upper arm bus bar connecting the positive electrode of the power supply and the upper arm semiconductor elements, and a lower arm bus bar connecting the negative electrode of the power supply and the lower arm semiconductor elements, the plurality of semiconductor elements are arranged on the substrate in a line in the direction of flow of the refrigerant for each of the upper arm and lower arm semiconductor elements connected to the same phase of the motor, and the upper arm semiconductor elements and the lower arm semiconductor elements are arranged offset in a direction perpendicular to the direction of flow of the refrigerant.

2. An inverter according to claim 1, wherein the inverter is arranged between the power supply and the motor, the semiconductor elements have collector surfaces on their undersides and emitters at their terminals, and the terminals are arranged so that they are perpendicular to the direction of flow of the refrigerant, the upper arm semiconductor elements and the lower arm semiconductor elements connected to the same phase of the motor are arranged rotated by 180° when viewed from above, and the center line of the refrigerant flow direction in the lower arm semiconductor elements is closer to the motor than the center line of the refrigerant flow direction in the upper arm semiconductor elements.

3. An inverter as claimed in claim 2, further comprising a smoothing capacitor between the power supply and the semiconductor element, wherein the upper arm bus bar and the lower arm bus bar each include a first bus bar directly above the refrigerant path, the upper surface of which is connected to a terminal of the smoothing capacitor by welding, and a second bus bar directly above the refrigerant path, the upper surface of which is connected to an output terminal of the motor by welding, and wherein the thickness of the terminal of the smoothing capacitor and the output terminal of the motor is thinner than the thickness of the first bus bar and the second bus bar.

4. An inverter according to claim 3, wherein the first bus bar extends in a direction perpendicular to the flow direction of the refrigerant, and the second bus bar extends in the flow direction of the refrigerant and in a direction perpendicular to the flow direction of the refrigerant.

5. An inverter according to claim 3 or 4, wherein the first bus bar includes a P bus bar and an N bus bar connected to the P terminal and the N terminal of the smoothing capacitor, respectively, and the welding point between the P terminal and the P bus bar and the welding point between the N terminal and the N bus bar are offset from each other in the flow direction of the refrigerant.

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