JP5742762B2 - Power converter - Google Patents

Description

  The technology disclosed in the present specification relates to a power conversion device including a reactor and a capacitor.

  Power converters such as inverters and converters often include a step-up circuit or a step-down circuit composed of a reactor, a capacitor, and a switching element. In a typical step-up circuit (or step-down circuit), a reactor and a capacitor are connected in series. More specifically, in the step-up circuit (or step-down circuit), the connection point between the reactor and the capacitor is connected to the input end, the other end of the reactor is connected to the switching element, and the other end of the capacitor is connected to the ground. Circuit configuration. A capacitor used as a set with a reactor in a step-up circuit or a step-down circuit may be called a filter capacitor.

  Although both the reactor and the capacitor generate heat, the reactor generates a large amount of heat. On the other hand, the capacitor has lower heat resistance than the reactor.

  In recent years, electric vehicles including hybrid vehicles have been actively developed, and motor power control units have a tendency to increase in capacity / compact. With the downsizing, the reactor and the capacitor are arranged close to each other, and a heat shielding technique between the reactor and the capacitor is being studied so that the heat of the reactor does not affect the capacitor.

  For example, Patent Document 1 discloses a technique in which a heat shielding member is disposed between a reactor and a capacitor, and the reactor and the capacitor are covered with an insulating heat transfer material such as a resin. For example, an epoxy resin is used as the insulating heat transfer material. Since a large current flows between the reactor and the capacitor, the reactor and the capacitor are connected to each other by a highly conductive metal rod-like conductive member called a bus bar. However, the technique of Patent Document 1 is covered with a heat transfer material including the bus bar. The technique of patent document 1 protects a capacitor | condenser from the heat of a reactor with a heat-shielding member and a heat-transfer material.

JP 2010-233294 A

  The technique of Patent Document 1 covers a heat transfer material including a bus bar and diffuses heat. However, the reactor and the capacitor may not be covered with a heat transfer material such as resin. On the other hand, since the bus bar is in the shape of a thin metal rod, the heat conductivity is high, and the bus bar becomes one of the heat transfer paths from the reactor to the capacitor. This specification provides the technique which suppresses the heat transfer from the reactor to a capacitor | condenser through a bus bar in the power converter device provided with the reactor and the capacitor | condenser.

  In one aspect of the power conversion device that embodies the technology disclosed in the present specification, the bus bar connecting the reactor and the capacitor is in contact with the case via the insulating heat transfer member. By adopting such a configuration, part of the heat transmitted from the reactor to the bus bar is not transmitted to the capacitor but diffuses to the case. The amount of heat transferred from the reactor to the capacitor can be suppressed.

  In another aspect of the power conversion device disclosed in this specification, the case of the power conversion device is divided into an upper case and a lower case. The reactor and the capacitor are fixed to the lower case, and the bus bar is in contact with the upper case via the heat transfer member. In this configuration, the heat of the bus bar is diffused in an upper case separate from the lower case that fixes the reactor and the capacitor. Therefore, heat transfer to the capacitor can be further suppressed. Further, the upper case corresponds to a lid for the lower case. That is, according to said structure, if an upper case is removed, a reactor, a capacitor | condenser, and a bus bar will be exposed, and it is excellent in assemblability and maintenance property.

  In still another aspect of the power conversion device disclosed in the present specification, the bus bar extends from the reactor, bends upward, then horizontally bends, further bends downward, and is connected to the condenser. Through the upper case. Normally, the bus bar should be short in order to reduce the electrical resistance. However, in one aspect of the novel power conversion device disclosed in this specification, the bus bar is not routed so as to connect the reactor and the capacitor in the shortest time, but the capacitor contacts the upper case even if it is bypassed upward. By suppressing heat transfer to the power converter, the total performance of the power converter is improved.

  Further, since the horizontal portion of the bus bar is arranged in parallel near the upper case, an additional effect of reducing the bus bar inductance can be expected. Usually, the case (upper case and lower case) is made of a conductive material such as aluminum. An alternating current flows from the reactor to the bus bar, but an induction magnetic field is generated in the upper case in a portion parallel to the bus bar due to the alternating current flowing to the bus bar. The induced magnetic field acts to cancel the magnetic field generated by the current flowing through the bus bar, and as a result, the inductance is reduced.

  Further, the bus bar is configured by bolting the reactor side bus bar extending from the reactor and the capacitor side bus bar extending from the capacitor, and the reactor side bus bar is in contact with the case via the heat transfer member. Good. The place where the bolt is attached becomes a heat reservoir, but by spreading a part of the heat to the case on the reactor side of the heat reservoir, the amount of heat transmitted to the periphery of the bolt and thus to the capacitor is reduced.

  The heat transfer member may be a sheet having elasticity. In the case where the reactor, the capacitor, and the bus bar are fixed to the lower case and the upper case is closed later, it is necessary to ensure a dimensional tolerance between the bus bar and the upper case. By adopting a sheet-like member having elasticity as the heat transfer member, contact via the heat transfer member can be ensured even if the gap between the bus bar and the upper case varies.

  Details of the technology disclosed in this specification and further improvements will be described in the embodiments of the present invention.

It is a block diagram of the electric power system of the hybrid vehicle of an Example. It is a top view of a power control unit (part). FIG. 3 is a cross-sectional view corresponding to the view taken along arrows III-III in FIG. It is a perspective view of a bus bar.

  A power converter according to an embodiment will be described with reference to the drawings. The power converter of the embodiment is a power control unit mounted on a hybrid vehicle. The power control unit includes a circuit that boosts the power of the main battery, converts it into alternating current, and outputs the alternating current to the motor, and a circuit that steps down the power of the main battery and supplies it to another electric device.

  Prior to explaining the power control unit, the power system of the hybrid vehicle will be outlined. FIG. 1 shows a block diagram of a power system of the hybrid vehicle 2. The hybrid vehicle 2 includes a motor 8 and an engine 6 as a driving source for traveling. The output torque of the motor 8 and the output torque of the engine 6 are appropriately distributed / combined by the power distribution mechanism 7 and transmitted to the axle 9 (that is, the wheel). It should be noted that FIG. 1 shows only parts necessary for the description of the technology disclosed in this specification, and some parts not related to the description are not shown.

  Electric power for driving the motor 8 is supplied from the main battery 3. The output voltage of the main battery 3 is, for example, 300 volts. In addition to the main battery 3, the hybrid vehicle 2 also includes an auxiliary battery 24 for supplying power to a device group driven by a voltage lower than the output voltage of the main battery 3, such as a car navigation device or a room lamp. . In FIG. 1, a device group that is driven at a voltage lower than the output voltage of the main battery 3 is collectively referred to as “auxiliary machine 25”. A signal processing circuit (such as a PWM generation circuit) other than the large current system circuit of the power control unit 5 is also a kind of auxiliary equipment. In addition, the name “main battery” is for convenience to distinguish from “auxiliary battery”. Hereinafter, in order to simplify the description, the power control unit 5 may be referred to as “PCU 5”.

  The main battery 3 is connected to the PCU 5 via the system main relay 4. The system main relay 4 is a switch for connecting or disconnecting the main battery 3 and the drive system of the vehicle. The system main relay 4 is switched by a host controller (not shown).

  The PCU 5 is an electronic circuit that is interposed between the main battery 3 and the motor 8. The PCU 5 includes a first converter circuit 12 that boosts the voltage of the main battery 3 to a voltage suitable for driving the motor 8 (for example, 600 volts), an inverter circuit 21 that converts the boosted DC power into AC, and the power of the main battery 3. Includes a second converter circuit 18 that steps down the voltage to a voltage suitable for driving the auxiliary device 25 (for example, 12 volts).

  The hybrid vehicle 2 can also generate electric power with the motor 8 using the driving force of the engine 6 or the deceleration energy of the vehicle. When the motor 8 generates power, the inverter circuit 21 converts alternating current into direct current, and the first converter circuit 12 steps down to a voltage slightly higher than the main battery 3 and supplies the voltage to the main battery 3.

  The first converter circuit 12 is a circuit mainly including a filter capacitor 13, a reactor 14, and two switching circuits 23a. The switching circuit 23a is composed of an anti-parallel circuit of an IGBT and a diode. More specifically, the configuration of the first converter circuit 12 is as follows. Reactor 14 and filter capacitor 13 are connected in series, and the connection point corresponds to the input of first converter circuit 12. The other end of the filter capacitor 13 is connected to the ground. The other end of the reactor 14 is connected to a connection point of two switching elements connected in series. Such a circuit configuration is well known as a buck-boost converter.

  The inverter circuit 21 is a circuit mainly including six switching circuits 23b that repeat switching to generate alternating currents of the U, V, and W phases of the motor 8. The switching circuit 23b is also composed of an antiparallel circuit of an IGBT and a diode.

  The IGBTs and diodes and the peripheral circuits constituting the switching circuit 23a of the first converter circuit 12 and the switching circuit 23b of the inverter circuit 21 are packaged as an intelligent power module (IPM). In this specification, description of such a package is omitted.

  A smoothing capacitor 16 is connected in parallel with the first converter circuit 12 on the high voltage side (that is, the inverter circuit side) of the first converter circuit 12. The smoothing capacitor 16 is inserted to smooth the current input to the inverter circuit 21. The electric wire on the high potential side of the switching circuit 23a of the first converter circuit 12 and the high potential side of the switching circuit 23b of the inverter circuit 21 is referred to as a P line. On the other hand, the electric wires on the low potential side of the first converter circuit 12 and the inverter circuit 21 are referred to as N lines. The N line is connected to the ground G. Since a large current is supplied from the main battery 3 to the motor 8, the heat generated by the filter capacitor 13 and the reactor 14 through which the large current flows is particularly large.

  In the PCU 5, a second converter circuit 18 that steps down the voltage of the main battery 3 is also connected to the main battery 3 via the system main relay 4. As shown in FIG. 1, the second converter circuit 18 supplies power to the auxiliary machine 25 and charges the auxiliary battery 24. The auxiliary battery 24 is provided for supplying electric power to the auxiliary machine 25 when electric power is not supplied from the main battery 3 (for example, when the system main relay 4 is opened).

  Next, the hardware configuration of the PCU 5 will be described. FIG. 2 shows a plan view of a part of the PCU 5 (portion related to the reactor 14 and the filter capacitor 13), and FIG. 3 shows a cross-sectional view corresponding to III-III in FIG. However, in FIG. 2 and FIG. 3, it should be noted that some hardware such as an IPM including an IGBT and a diode constituting the switching circuit 23b are omitted. In FIG. 3, the illustration of the inside of the second converter unit 52 is omitted. The second converter unit 52 is a housing that houses the second converter circuit 18 described above.

  The case 41 of the PCU 5 is divided into an upper case 41a and a lower case 41b. Both the upper case 41a and the lower case 41b are made of aluminum and are conductive. In FIG. 2, the upper case 41a is not shown. Inside the case 41, the filter capacitor 13, the smoothing capacitor 16, the reactor 14, and the above-described IPM (not shown) are stored as main units. In addition, the case 41 stores a board unit that generates a PWM signal for the switching circuits 23a and 23b and a cooler that cools electronic components and the like, which are not shown.

  As shown in FIG. 3, the reactor 14 includes a core 15a, a coil 15b wound around the core 15a, and a resin 15c covering the core 15a. The core 15a is obtained by firing magnetic iron powder. The lower side of the resin 15c is fixed to the lower case 41b. Although not shown, more specifically, the resin 15c is fixed to the lower case 41b with a bolt.

  A filter capacitor 13 is disposed adjacent to the reactor 14. A shielding plate 41c is erected between the reactor 14 and the filter capacitor 13 from the bottom of the lower case 41b upward. The shielding plate 41 c prevents the heat generated by the reactor 14 from being directly transmitted to the filter capacitor 13. Note that both the reactor 14 and the filter capacitor 13 are fixed to the lower case 41b.

  A reactor positive electrode bus bar 31 (reactor side bus bar) is connected to one end 14a of the coil 15b of the reactor 14, and a reactor negative electrode bus bar 34 is connected to the other end 14b of the coil 15b. Although not shown, the reactor negative electrode bus bar 34 is connected to the ground G. The “bus bar” is a metal rod-shaped member having a low resistance value, and means a conductive member for flowing a large current.

  As is apparent from the block diagram of FIG. 1, one end 14 a of the reactor 14 is connected to the filter capacitor 13. In terms of hardware, as shown in FIGS. 2 and 3, the reactor positive electrode bus bar 31 connected at one end 14 a of the reactor 14 and the capacitor side bus bar 32 extending from the filter capacitor 13 are connected by a bolt 38. ing. Although not shown, a bus bar that supplies power from the main battery 3 is also connected to the bolt 38. The capacitor-side bus bar 32 has a branch end 32 a extending from the middle, and the branch end 32 a is connected to one electrode of the filter capacitor 13. The other power of the filter capacitor 13 is connected to the ground G. The other end of the capacitor side bus bar 32 extends further downward from the branch end 32 a and is connected to the DC converter side bus bar 35 by a bolt 39.

  FIG. 4 is a perspective view of the reactor positive electrode bus bar 31 (reactor side bus bar 31) and the capacitor side bus bar 32. One end of the reactor positive electrode bus bar 31 is connected to one end 14a of the coil of the reactor 14 (location indicated by symbol Pa in FIG. 4). Reactor positive electrode bus bar 31 and one end 14a of the coil are joined by welding. Reactor positive electrode bus bar 31 extends in the horizontal direction from one end 14a of the coil, then bends upward, then bends horizontally, and further bends downward to connect to capacitor-side bus bar 32. A connection point Pb between the reactor positive electrode bus bar 31 and the capacitor side bus bar 32 is above the filter capacitor 13. The capacitor-side bus bar 32 extends downward along the filter capacitor 13, and the branch end 32 a wraps around the side of the filter capacitor 13 on the way. The branch end 32 a is connected to an end electrode (metallicon electrode) of the filter capacitor 13. The capacitor-side bus bar 32 extends further downward and wraps around the lower side of the filter capacitor 13, where it is connected to the DC converter-side bus bar 35 via a bolt 39 (location indicated by reference numeral Pc in FIG. 4). In addition, XY in each figure has shown the horizontal surface, and the Z-axis has shown the perpendicular direction.

  A heat transfer member 36 is disposed on the uppermost horizontal portion 31a of the reactor positive electrode bus bar 31, and the heat transfer member 36 is in contact with the upper case 41a (see FIG. 3). That is, the reactor positive electrode bus bar 31 is in contact with the upper case 41 a via the heat transfer member 36. The heat transfer member 36 is also an insulating material. The heat transfer member 36 is made of, for example, silicon rubber, and is excellent in insulation and heat transfer. Further, the heat transfer member 36 has an appropriate elasticity, and when the upper case 41a is put on the lower case 41b, the heat transfer member 36 contracts between the reactor positive electrode bus bar 31 and the upper case 41a, and the reactor positive electrode bus bar 31 and the upper case It sticks to both sides of 41a.

  Since a large current for driving the motor flows through the reactor 14, the amount of heat generated is large. The coil 15b that constitutes the reactor 14 is made of a flat wire, and the bus bar that is electrically connected to the coil 15b has a thin plate shape, so that heat is easily transmitted. As well shown in FIG. 3, the reactor positive electrode bus bar 31 is once bent upward and then bent in the horizontal direction. The horizontal portion 31 a is in contact with the upper case 41 a through the heat transfer member 36. The heat of the reactor 14 is transmitted to the filter capacitor 13 via the reactor positive electrode bus bar 31 and the capacitor side bus bar 32, but part of the heat is released from the horizontal portion 31 a to the upper case 41 a via the heat transfer member 36. That is, the amount of heat transmitted from the reactor 14 to the filter capacitor 13 via the bus bar is suppressed. Since the horizontal portion 31a is relatively distant from the filter capacitor 13, there is not much heat transferred to the capacitor 13 by detouring from the upper case 41a to the lower case 41b. As well shown in FIGS. 3 and 4, it is not necessary to bypass the reactor positive electrode bus bar 31 upward in order to connect the one end 14 a of the reactor and the electrode of the filter capacitor 13 at the shortest distance. However, the technology disclosed in the present specification bypasses the bus bar so as to pass through the vicinity of the upper case 41 a and brings the bus bar and the upper case 41 a into contact with each other via the heat transfer member 36. With such a structure, the amount of heat transferred from the reactor 14 to the filter capacitor 13 is suppressed, and the filter capacitor 13 is thermally protected.

  Further, the horizontal portion 31 a that transfers the heat of the reactor to the upper case 41 a is located on the reactor side with respect to the bolt 38 that is a connection point between the reactor positive electrode bus bar 31 and the capacitor side bus bar 32. The bolt 38 is easy to accumulate heat, but since the bus bar is in contact with the upper case 41a on the reactor side of the bolt 38, the heat can be diffused to the upper case 41a before reaching the bolt 38. By suppressing the amount of heat from being accumulated in the bolt 38, the amount of heat transmitted from the reactor 14 to the filter capacitor 13 is further effectively suppressed.

  Further, the horizontal portion 31a extends in parallel near the top plate of the upper case 41a. The upper case 41a is made of aluminum and is conductive. An alternating current flows through the reactor 14 to the bus bar. An induced magnetic field is generated in the upper case 41a due to a change in the current flowing through the bus bar. The induced magnetic field cancels a part of the magnetic field generated by the current flowing through the bus bar. Since a part of the magnetic field generated by the current flowing through the bus bar is canceled, the above structure also has an additional effect of reducing the inductance of the bus bar.

  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 illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: Hybrid vehicle 3: Main battery 4: System main relay 5: Power control unit (power converter)
6: Engine 8: Motor 12: Converter circuit 13: Filter capacitor 14: Reactor 15b Coil 16: Smoothing capacitor 18: Converter circuit 21: Inverter circuit 23a, 23b: Switching circuit 24: Auxiliary battery 25: Auxiliary machine 31: Reactor Positive bus bar (reactor side bus bar)
31a Horizontal portion 32: Capacitor-side bus bar 32a: Branch end 36: Heat transfer member 38, 39: Bolt 41: Case 41a: Upper case 41b: Lower case 52: Converter unit

Claims (4)

The bus bar connecting the reactor and the capacitor is in contact with the case via an insulating heat transfer member ,
The case is divided into an upper case and a lower case.
The reactor and capacitor are fixed to the lower case,
The bus bar is in contact with the upper case through a heat transfer member . The bus bar extends from the reactor, bends upward, then bends horizontally, is further bent downward, is connected to the condenser, and is in contact with the upper case via a heat transfer member at the horizontal portion. The power converter according to 1 . The bus bar is configured by bolting a reactor side bus bar extending from the reactor and a capacitor side bus bar extending from the capacitor, and the reactor side bus bar is in contact with the case via a heat transfer member. The power converter according to claim 1 or 2, wherein The power conversion device according to any one of claims 1 to 3 , wherein the heat transfer member has a sheet shape having elasticity.

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