JP2014017900A - Inverter for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which reduces stress applied to a support end of a terminal board in an inverter where the terminal board is supported in a cantilever manner and an end part opposite to the support end of the terminal board is connected with an external cable.SOLUTION: An inverter disclosed by this specification includes a terminal board 3 which connects a bus bar in the inverter with a terminal of a power cable extending from a motor. The terminal board 3 is supported in the inverter in a cantilever manner. In the terminal board 3, a terminal attachment surface 3a for attaching the terminal 50 faces in a direction intersecting with a direction that leads from a support end 3e of the terminal board 3 to a tip 3f. The terminal board includes a nut 5, which receives a bolt 52, so that a bus bar tip 9a positioned on the terminal attachment surface and the terminal 50 of the power cable are fastened by the bolt 52 inserted thereto. The nut 5 is attached so as to move in a bolt insertion direction without being removed from the terminal board.

Description

  The present invention relates to an inverter that drives a motor of an electric vehicle. The “electric vehicle” in the present specification includes a hybrid vehicle and a fuel cell vehicle having both a motor and an engine.

  The electric vehicle includes an inverter that converts the DC power of the battery into AC power having a frequency suitable for driving the motor. In many electric vehicles, a motor is generated using the inertia energy of the vehicle at the time of braking, and the generated electric power is converted into direct current by an inverter to charge a battery.

  Since a large current flows through an electric cable (referred to as a power cable) connecting the inverter and the motor, a thick conductor is used. One end of the power cable is connected to the motor, and the other end is connected to the inverter. Since the connection portion between the inverter and the power cable is at a high voltage, the connection portion may be provided inside the casing of the inverter in order to isolate the connection portion from the outside (for example, Patent Document 1).

JP 2011-187933 A

  Miniaturization is required for in-vehicle devices including inverters. Various components are housed inside the inverter casing, but in order to reduce the size of the entire device, a device is required to arrange the components. As a result of devising the arrangement of various parts and downsizing the inverter housing, the layout of the terminal block for connecting the power cable terminals is reduced, and in some cases, the terminal block can be supported in a cantilevered manner. It may be required to fix with. On the other hand, since the power cable is thick and has high rigidity, if the power cable is connected at or near the tip of the terminal block that is cantilevered (the end away from the support end of the terminal block), the power cable is pulled. As a result, stress concentration may occur at the support end of the terminal block. The present specification relates to an inverter in which a terminal block is cantilevered and is connected to an external cable at an end on the opposite side, and provides a technique for reducing stress applied to the support end of the terminal block.

  The inverter disclosed in this specification includes a terminal block that connects a bus bar in the inverter and a terminal of a power cable extending from the motor. The terminal block is cantilevered inside the inverter. And the terminal attachment surface has faced the direction which cross | intersects the direction which goes to the edge part on the opposite side to a support end from the support end of a terminal block. Here, in order to simplify the description, the “direction intersecting the direction from the support end toward the end opposite to the support end” will be referred to as the “cantilever lateral direction”. The terminal mounting surface faces the opening provided in the casing of the inverter. Further, the terminal block includes a nut for receiving the bolt so that the front end of the bus bar positioned on the terminal mounting surface and the terminal of the power cable can be fastened by a bolt inserted in the lateral direction of the cantilever through the opening. The nut is attached so as to be movable in the lateral direction of the cantilever without being detached from the terminal block. More specifically, the nut is attached so as to be movable in the lateral direction of the cantilever without detaching from the terminal block by a predetermined length even after the bus bar tip and the terminal of the power cable are fastened by the bolt. In one aspect of mounting the nut movably, the nut is a recess provided facing the terminal mounting surface of the terminal block, and the opening is incorporated in a recess whose opening is narrowed in a bottleneck shape with respect to the internal space. Yes. On the other hand, one aspect of the nut is provided with a protruding portion on the side surface, and the protruding portion is locked to the bottleneck portion of the opening of the recess so as not to be detached from the terminal block. And it can move until the end face (front end face) of the bolt insertion side of the nut protrudes from the terminal mounting face.

  According to said structure, a volt | bolt is penetrated by the bus bar front-end | tip located on a terminal attachment surface and the terminal of a power cable through the opening of a housing | casing, and is fastened by the said nut of a terminal block. And even after the end of the bus bar and the terminal of the power cable are fastened between the front end face of the nut and the bolt, the fastening portion (bolt and nut) can move by a predetermined length. The predetermined length becomes so-called “play” (clearance / allowance), which reduces the tensile force due to the rigidity of the power cable and reduces the stress applied to the support end.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a disassembled perspective view of the inverter of an Example. It is a figure of the bus bar and the current sensor excluding the terminal block main body, and is a diagram showing the positional relationship between the bus bar and the current sensor. It is a figure which shows the terminal block set to the predetermined position of a housing | casing. FIG. 4 is a YZ plane sectional view of the terminal block in FIG. 3. It is an expanded sectional view of the nut loosely fitted in the hollow provided in the terminal block body. It is YZ sectional drawing of a terminal block (power cable fastening state). It is a YZ sectional view of a terminal block (state where a nut was pulled out). It is a perspective view of a nut. It is a perspective view of a nut of another shape.

  Before describing the embodiments, other features of the inverters of the embodiments will be listed.

  (1) The terminal block is made of resin. In the terminal block, a current sensor that measures the current flowing through the bus bar, which is an output current of the inverter, and the bus bar are integrally manufactured by insert molding.

  (2) The inverter includes a semiconductor laminated unit in which a plurality of flat plate type semiconductor modules containing switching elements for outputting AC power to the motor and a plurality of flat plate type cooling plates are stacked. The end of the bus bar opposite to the power cable terminal connection side is connected to the current output terminal of the semiconductor module.

  The inverter 2 of an Example is demonstrated with reference to drawings. FIG. 1 shows an exploded perspective view of the inverter 2. The inverter 2 in FIG. 1 is a device that is mounted on an electric vehicle and boosts the direct current power of a battery and converts it into alternating current suitable for driving a motor. The inverter 2 includes, as main components, large-capacitance capacitors 21 and 23, a semiconductor multilayer unit 10, a reactor 22, a terminal block 3, and a control board 24 on which a control circuit is mounted. All of these parts are housed in the housing 20.

  The semiconductor stacked unit 10 has a structure in which a plurality of flat semiconductor modules 12 in which switching elements (typically IGBTs) are molded with resin and a plurality of flat cooling plates 15 through which a coolant passes are alternately stacked. Some of the switching elements molded in the semiconductor module 12 constitute an inverter circuit, and others are used for voltage converters. A large amount of current flows through the switching elements used in the inverter circuit and voltage converter, so the amount of heat generated is large. The switching element can be effectively cooled by molding it into a flat plate with resin and sandwiching it with a cooling plate.

  As is well known, an inverter circuit is a circuit in which three sets of series connection circuits of two switching elements are connected in parallel as a main circuit. An alternating current is output from the midpoint of the series connection of the two switching elements. One semiconductor module 12 is molded with two switching elements and diodes (reflux diodes) connected in antiparallel to the respective switching elements, and the two switching elements are internally connected in series. From the lower surface of the semiconductor module 12, three metal flat plate terminals (13a, 13b, 13c) extend. The three terminals are a high-voltage side terminal 13c, a low-voltage side terminal 13b, and an intermediate terminal 13a that are connected in series, respectively. The intermediate terminal 13a corresponds to the output terminal of the inverter circuit, and AC power supplied to the motor is output. The bus bar 9 is connected to the intermediate terminal 13a. In FIG. 1, the bus bars connected to the high voltage side terminal 13c and the low voltage side terminal 13b are not shown. A signal line (control signal line 14) for inputting a signal (PWM signal) to be applied to the gate of the switching element extends from the upper surface of the semiconductor module 12.

  The reactor 22 forms a voltage converter together with some switching elements in the semiconductor multilayer unit 10. The capacitor 21 is connected in parallel to the input end of the voltage converter, and the capacitor 23 is connected in parallel to the output end of the voltage converter (input end of the inverter circuit). Capacitors 21 and 23 are provided to smooth the current flowing through the circuit. Since the inverter 2 supplies electric power to the traveling motor and handles a large current, capacitors 21 and 23 having large capacities are employed. In the drawing, only six semiconductor modules 12 corresponding to two inverter circuits are shown, and the semiconductor module 12 for a voltage converter circuit is not shown.

  As shown in FIG. 1, a control board 24 on which a circuit for controlling a switching element is mounted is placed above the semiconductor multilayer unit 10 and the reactor 22. On the control board 24, as shown in FIG. 1, electronic components such as chips constituting a circuit are physically mounted. The control signal line 14 extending from the upper surface of the semiconductor module 12 and the current sensor signal line 19 extending from the sensor circuit board 18 disposed on the upper surface of the terminal block 3 are connected to the control board 24. The control board 24 generates a PWM signal based on sensor data of a current sensor (described later) so that the inverter circuit has a predetermined output and outputs the PWM signal to the semiconductor module 12.

  The relationship among the semiconductor laminated unit 10, the bus bar 9, and the terminal block 3 constituting the inverter circuit will be described in detail. The inverter 2 supplies electric power to the two motors for traveling. Therefore, the inverter 2 includes two inverter circuits. One inverter circuit outputs UVW3 phase. The bus bar 9 is a conductor that passes the output of the inverter circuit, and one end thereof is connected to an intermediate terminal (terminal 13a) of two switching elements connected in series.

  Since the motor is a three-phase AC motor, the output of one inverter circuit is also UVW three-phase. Since the inverter 2 drives two motors, two sets of UVW three-phase outputs and a total of six bus bars extend from the semiconductor laminated unit 10. The other end of the bus bar 9 (the end opposite to the end connected to the semiconductor laminated unit 10) is embedded in the terminal block 3. The terminal block 3 is a device for connecting a bus bar 9 inside the inverter and a power cable terminal (not shown in FIG. 1, which will be described later with reference to FIG. 3) extending from the motor. The other end 9 a of the bus bar 9 is exposed to face one side 3 a of the terminal block 3.

  The main body 4 of the terminal block 3 is made of resin, and a core 16 of a current sensor is embedded therein by insert molding. The bus bar 9 is also embedded together with the core 16 by insert molding. In FIG. 2, the positional relationship among the terminals 13 a, the bus bar 9, and the core 16 of the semiconductor module 12 is shown with the main body 4 omitted. The current sensor includes a C-shaped core 16 and a magnetosensitive element (not shown) disposed in a gap between the core 16 (a gap between both ends of the C-shape). The magnetosensitive element is connected to the sensor circuit board 18, and the output of the magnetosensitive element is processed by the sensor circuit board 18 and sent to the control board 24 through the sensor signal line 19. The core 16 is disposed so as to surround the bus bar 9. When a current flows through the bus bar 9, an induced magnetic field is generated due to the current. The induction magnetic field concentrates on the core 16. An induced magnetic field flowing through the core 16 is measured by a magnetosensitive element arranged in the gap of the core, and the magnitude of the current flowing through the bus bar 9 is specified from the strength.

  As shown in FIG. 2, the end 9 a on the terminal block side of the bus bar 9 is bent at a right angle and is located on the surface 3 a of the one surface 3 a of the terminal block 3. Hereinafter, one surface 3a of the terminal block 3 is referred to as a terminal mounting surface 3a. Further, the end of the bus bar positioned on the terminal mounting surface 3a is referred to as an end surface 9a. When the terminal block 3 is fixed to the casing 20 of the inverter 2, the terminal mounting surface 3a faces the opening 20a provided in the casing 20, and the end face 9a of the bus bar 9 is exposed from the opening 20a. Next, the attachment structure of the terminal block 3 will be described.

  Flange 3 b is provided on both sides of the main body 4 of the terminal block 3. The flange 3 b is provided with a through hole, and the terminal block 3 is fixed to the casing 20 of the inverter 2 through a bolt through the through hole. FIG. 3 shows the terminal block 3 installed in the casing 20 of the inverter 2. In FIG. 3, illustration of the fixed state of the terminal block 3 is omitted. FIG. 4 shows a cross-sectional view of the terminal block 3 cut along the YZ plane of FIG. Note that the lower side of the line AA in FIG. 4 shows a cross section passing through the hole of the end face 9a of the bus bar 9, and the upper side of the line AA in FIG. 4 shows a cross section through the bolt insertion hole of the flange 3b. I want.

  As shown in FIGS. 3 and 4, the end face 9a of the bus bar 9 faces the opening 20a of the housing 20, and the terminal 50 of the power cable 51 extending from the motor (not shown) to the end face 9a through the opening 20a is a bolt. Connected at 52. In FIG. 3, only two power cables 51 are shown, but the power cables are connected to all six end faces 9a.

  As shown in FIG. 4, a protruding portion 20 b is provided on the inner side of the housing 20, and the flange 3 b of the terminal block 3 is fixed to the lower surface thereof with bolts 41. As shown in FIG. 4, the terminal block 3 has a cantilever support structure that is fixed to the housing 20 at the upper end 3e in the vertical direction (Z-axis direction) and extends downward. Hereinafter, the upper end 3e is referred to as a cantilever support end 3e. The terminal attachment surface 3a is located in the vicinity of the end portion 3f opposite to the cantilever support end 3e. The bolt 52 for fixing the terminal 50 of the power cable 51 has a direction (in the Y-axis direction in FIG. 4) that intersects the direction (ie, the Z-axis direction in FIG. 4) from the cantilever support end 3e toward the opposite end 3f. Yes, referred to as the cantilever lateral direction). When the power cable 51 has high rigidity and is fastened to the end surface 9a of the bus bar 9 with the bolt 52, the power cable 51 tends to return to the positive direction of the Y axis in FIG. The force brings a bending moment to the terminal block 3 at the tip 3f of the terminal block 3 that is cantilevered (the end opposite to the support end 3e). Since the terminal block 3 has a cantilever support structure, the bending moment acts intensively on the support end 3e. When the nut that receives the bolt 52 is fixed to the terminal block 3, a bending moment acts directly on the support end 3e, fatigues the support end 3e, and lowers its durability. In the inverter 2 of the present embodiment, the stress concentration on the support end 3e due to the tensile force of the power cable 51 is reduced. The mechanism will be described next.

  As shown in FIG. 4, a nut 5 that receives a bolt 52 is attached to the main body 4 of the terminal block 3. A through hole is provided in the end face 9a of the bus bar 9 and the terminal 50 of the power cable 51, and FIG. 5 shows an enlarged cross-sectional view of the nut 5 loosely fitted in a recess 3c provided in the terminal base body 4. The terminal 50 is overlapped on the end face 9a, the bolt 52 is passed through the through hole, and the bolt 52 is fastened to the nut 5 to fix the terminal 50 of the power cable 51 to the terminal block 3 (to the bus bar 9). FIG. 6 shows a state in which the terminal 50 of the power cable 51 is fastened to the terminal block 3. The nut 5 is loosely fitted in a recess 3 c provided so as to open on the terminal mounting surface 3 a of the main body 4. In the opening of the recess 3c, a flange 3d is provided inwardly, and the opening is narrowed like a bottle neck. The nut 5 is provided with a protruding portion 5 b on the side surface, and the protruding portion 5 b is caught by the flange 3 d so that the nut 5 does not come off the main body 4. Further, the depth of the recess 3c has a margin with respect to the length of the nut 5, and the nut 5 can move by a predetermined distance in the axial direction (Y-axis direction in FIGS. 4 and 5). However, as described above, the nut 5 does not come off the main body 4. FIG. 7 shows a state where the nut 5 is pulled by the power cable 51 and moved by a distance d. Thus, the nut 5 can move by the distance d without applying a load to the support end 3e of the terminal block 3 while the terminal 50 is fastened to the end face 9a of the bus bar 9. Therefore, the stress applied to the support end 3e that cantilever-supports the terminal block 3 can be reduced.

  As shown in FIGS. 5 to 7, the end surface 5 a of the nut 5 can protrude from the terminal mounting surface 3 a of the main body 4. Therefore, the end face 9 a of the bus bar 9 and the terminal 50 of the power cable 51 can be fastened together between the end face 5 a of the nut 5 and the bolt 52. With this structure, the end face 9a of the bus bar 9 and the terminal 50 of the power cable 51 can be firmly fastened without applying a load to the main body 4 of the terminal block.

  FIG. 8 shows a perspective view of the nut 5. FIG. 9 shows a nut 105 according to a modification. Both nuts are provided with projecting portions 5b and 105b on the side surfaces. These projecting portions 5b and 105b are hooked on the opening flange 3d of the recess 3c provided in the terminal block body 4, and the nut 5 (105) is provided. This prevents the terminal block 3 from coming off.

  Points to be noted regarding the technology described in the embodiments will be described. In the terminal block 3, the terminal 50 of the power cable 51 is fastened by a bolt 52 that is inserted in the cantilever lateral direction (Y-axis direction in the drawing). The force applied in the lateral direction of the cantilever acts directly on the support end 3 e of the terminal block 3 as a bending moment. Therefore, if the force applied in the lateral direction of the cantilever is large, a large concentrated stress is applied to the support end 3e. In the terminal block disclosed in the present specification, the terminal of the power cable 51 is fixed by a bolt 52 inserted in the lateral direction of the cantilever. The power cable 51 is thick and has high rigidity, is separated from the terminal block 3 before being fixed with bolts, and is strongly bent and fixed to the terminal block 3. The power cable 51 has a restoring force acting in the lateral direction of the cantilever, and the restoring force becomes a bending moment for the terminal block 3 that is cantilevered. The technology disclosed in this specification allows the bolt 52 and the nut 5 to be displaced in the lateral direction of the cantilever while the terminal 50 of the bus bar 9 and the power cable 51 is fastened together with the bolt 52 and the nut 5. In particular, the bolt 52 and the nut 5 are allowed to move from the state in which the power cable 51 is fastened to the direction in which the power cable 51 returns to the original position (that is, the direction in which the restoring force is weakened). Therefore, the restoring force acting on the power cable 51 is weakened, and the stress applied to the support end 3e of the terminal block 3 is relaxed.

  The technology disclosed in this specification is not limited to the structure of the inverter of the embodiment. Further, the structure of the terminal block and the structure of the nut are not limited to the structure of the embodiment. The technology disclosed in this specification can be applied to a structure in which a terminal block is cantilevered and a cable is fixed to the terminal block.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Inverter 3: Terminal block 3a: Terminal mounting surface 3b, 3d: Flange 3c: Depression 3e: Support end 3f: Tip 4: Terminal block body 5: Nut 5a: End surface 5b: Protruding portion 9: Bus bar 9a: End surface 10: Semiconductor laminated unit 12: Semiconductor modules 13a, 13b, 13c: Terminal 14: Control signal line 15: Cooling plate 16: Core 18: Sensor circuit board 19: Current sensor signal line 20: Housing 20a: Opening 20b: Projection 21 23: Capacitor 22: Reactor 24: Control board 41, 52: Bolt 50: Terminal 51: Power cable

Claims (5)

It is an inverter with a terminal block that connects the bus bar inside the inverter and the terminal of the power cable extending from the motor,
The terminal block is
Cantilevered inside the inverter,
The terminal mounting surface for mounting the terminal faces a direction intersecting with the direction from the support end of the terminal block toward the end opposite to the support end,
The bus bar tip located on the terminal mounting surface and the terminal of the power cable are provided with a nut for receiving the bolt so that it can be fastened by a bolt inserted in the intersecting direction,
The inverter, wherein the nut is attached so as to be movable in the intersecting direction without being detached from the terminal block. The nut is
It has a protruding part on the side, and is locked by the protruding part so as not to come off from the terminal block,
2. The inverter according to claim 1, wherein the end surface on the bolt insertion side is movable until it projects beyond the terminal mounting surface. The terminal mounting surface faces the opening provided in the inverter housing,
3. The inverter according to claim 1, wherein the bolt is inserted through the opening into a bus bar tip positioned on the terminal mounting surface and a terminal of the power cable and fastened to the nut of the terminal block. The terminal block body is made of resin,
The inverter according to any one of claims 1 to 3, wherein a current sensor that measures an output current of the inverter and that flows through the bus bar and the bus bar are integrated with the main body by insert molding. . Inverter
It has a semiconductor laminated unit in which a plurality of flat plate type semiconductor modules containing switching elements for outputting AC power to a motor and a plurality of flat plate type cooling plates are laminated,
5. The inverter according to claim 4, wherein an end portion of the bus bar opposite to the power cable terminal connection side is connected to a current output terminal of the semiconductor module.

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