Circuit unit

Abstract

To provide a circuit unit capable of stably controlling an inrush current while suppressing an increase in an installation space of a precharge resistor.SOLUTION: A circuit unit 10 connected between an on-vehicle power supply 12 and a load 14 includes a main relay 18 that performs switching between energization and de-energization between the on-vehicle power supply 12 and the load 14, and a precharge relay 22 and a precharge resistor 24 that configure a precharge circuit 20 connected in parallel with the main relay 18, in which the precharge resistor 24 is configured by using a metal-clad resistor, and a metal case 54 of the metal-clad resistor has a thermal contact portion 56 that thermally contacts a heat radiation target 80.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a circuit unit. [Background technology]

[0002] Patent Document 1 discloses a circuit unit that is housed in a battery pack mounted on a vehicle and switches between energization and de-energization between the battery and a load. The circuit unit houses a relay and a pre-charge resistor, which is a ceramic resistor, in a case. The pre-charge resistor is connected in series with a pre-charge relay and forms a pre-charge circuit that is connected in parallel with the relay. The pre-charge circuit pre-charges a capacitor in the vehicle load, thereby controlling the inrush current that flows through the load (e.g., inverter circuit) when the vehicle starts up and protecting circuit components such as the capacitor and relay. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-181737 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, inrush currents have become larger due to the trend toward higher voltages in recent vehicles, and in many cases multiple pre-charge resistors are required to control the inrush current. On the other hand, there is also a demand for smaller circuit units, making it difficult to secure space to install pre-charge resistors.

[0005] Therefore, a circuit unit is disclosed that can stably control the inrush current while suppressing an increase in the mounting space for the precharge resistor. [Means for solving the problem]

[0006] The circuit unit disclosed herein is a circuit unit connected between an on-board power supply and a load, and includes a main relay that switches between energization and de-energization between the on-board power supply and the load, and a pre-charge relay and a pre-charge resistor that constitute a pre-charge circuit connected in parallel to the main relay, wherein the pre-charge resistor is constructed using a metal clad resistor, and the metal case of the metal clad resistor has a thermal contact portion that is in thermal contact with a heat dissipation target. Effect of the Invention

[0007] According to the circuit unit of the present disclosure, it is possible to control the inrush current while suppressing an increase in the mounting space for the precharge resistor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a circuit unit according to a first embodiment in a state where it is fixed to a heat dissipation target. [Diagram 2] FIG. 2 is a perspective view showing the circuit unit shown in FIG. 1 with an upper case that constitutes an insulating case removed. [Diagram 3] FIG. 3 is a plan view of the circuit unit shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a perspective view showing the circuit unit shown in FIG. 1 in a state where it is fixed to another heat dissipation target, with an upper case constituting an insulating case removed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Description of the embodiments of the present disclosure> First, embodiments of the present disclosure will be listed and described. The circuit unit of the present disclosure includes: (1) A circuit unit connected between an on-board power supply and a load, comprising: a main relay that switches between energization and de-energization between the on-board power supply and the load; and a pre-charge relay and a pre-charge resistor that constitute a pre-charge circuit connected in parallel to the main relay, wherein the pre-charge resistor is constructed using a metal clad resistor, and the metal case of the metal clad resistor has a thermal contact portion that is in thermal contact with a heat dissipation target.

[0010] According to the circuit unit of this aspect, the precharge resistor of the precharge circuit that controls the inrush current when the vehicle is started is configured using a metal clad resistor that is configured by insulating a wound resistor and sealing it in a metal case. Metal clad resistors are used for large currents, so they can handle large currents without increasing the number of resistors as in the case of conventional ceramic resistors. In other words, by using a metal clad resistor, it is possible to stably control the inrush current while suppressing an increase in the mounting space for the precharge resistor or reducing the mounting space.

[0011] Moreover, since the metal clad resistor itself has a metal case, it has excellent heat dissipation properties, and by thermally contacting the thermal contact part of the metal case with the heat dissipation target, a heat dissipation path for the metal clad resistor can be easily secured, improving the heat dissipation properties of the metal clad resistor, thereby ensuring the operational stability of the metal clad resistor and enabling more stable control of inrush current.

[0012] The heat dissipation target with which the thermal contact portion of the metal case of the metal clad resistor comes into thermal contact may be a component provided in the circuit unit itself (e.g., the case of the circuit unit, etc.) or a component other than the circuit unit (e.g., the housing of a battery pack in which the circuit unit is mounted, etc.).

[0013] (2) In the above (1), it is preferable that the device has an insulating case that holds the main relay, the pre-charge relay, and the pre-charge resistor, and the insulating case has an opening window that exposes the thermal contact portion of the metal case of the metal clad resistor so that it can be thermally contacted with the heat dissipation target. While the main relay, the pre-charge relay, and the pre-charge resistor are stably held in the insulating case, the thermal contact portion of the metal case can be brought into thermal contact with the heat dissipation target through the opening window provided in the insulating case, and it is possible to simultaneously ensure insulation between the main relay, the pre-charge relay, and the pre-charge resistor, and a heat dissipation path in the metal clad resistor.

[0014] (3) In the above (1) or (2), it is preferable that the thermal contact portion of the metal case contacts the heat dissipation target via an elastic heat dissipation sheet or a gap filler, which advantageously prevents a gap from being formed between the thermal contact portion formed by the surface of the metal case of the metal clad resistor and the heat dissipation target, thereby advantageously preventing a reduction in the heat dissipation performance of the metal clad resistor.

[0015] (4) In any one of the above (1) to (3), it is preferable that the heat dissipation target with which the thermal contact portion of the metal clad resistor is in thermal contact is a heat sink in thermal contact with the main relay. The main relay generates heat when the power source and the load are energized, while the metal clad resistor generates heat when the vehicle is started, which is different from the time when the main relay generates heat. Therefore, by skillfully using the heat sink for the main relay as the heat dissipation target for the metal clad resistor, it is possible to ensure a heat dissipation path for the metal clad resistor while suppressing an increase in the number of parts.

[0016] The heat sink may be a metal plate that is in close contact with the insulating case described in (2) above that constitutes the circuit unit, or it may be a metal housing of a battery pack on which the insulating case described in (2) above is placed.

[0017] (5) In any one of the above (1) to (4), it is preferable that the heat dissipation target with which the thermal contact portion of the metal clad resistor is in thermal contact is a metal plate that constitutes the housing of the vehicle-mounted power supply and has a refrigerant flow path through which a refrigerant flows inside. This is because by using a metal plate having a refrigerant flow path in the housing of the vehicle-mounted power supply to which the circuit unit is connected as the heat dissipation target, the heat dissipation properties of the metal clad resistor can be further advantageously increased.

[0018] <Details of the embodiment of the present disclosure> Specific examples of the circuit unit of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0019] <Embodiment 1> Hereinafter, a circuit unit 10 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. The circuit unit 10 is mounted on, for example, an electric vehicle or a hybrid vehicle, and is connected between an on-board power source and a load. In the first embodiment, the circuit unit 10 is connected between a battery 12, which is an example of an on-board power source, and an inverter 14, which is an example of a load. The circuit unit 10 can be arranged in any direction in the vehicle, but in the following, the upper side will be described as the upper side in FIG. 4, the lower side as the lower side in FIG. 4, the left side as the left side in FIG. 3, the right side as the right side in FIG. 3, the front side as the lower side in FIG. 3, and the rear side as the upper side in FIG. 3. In addition, for multiple identical members, only some of the members may be labeled with a reference symbol, and the reference symbols may be omitted for the other members.

[0020] The battery 12 may be a known one, and the structure is not limited, but may be, for example, a battery module made up of a plurality of battery cells (not shown). The battery 12 (battery module) may be housed in, for example, a metal housing 16 (see FIG. 6 described later), and the battery 12 and the circuit unit 10 are housed together in the housing 16 to form a battery pack (not shown).

[0021] <Circuit unit 10> The circuit unit 10 includes a positive side relay 18 serving as a main relay for switching between energization and de-energization between the battery 12, which is a power source, and the inverter 14, which is a load, and a pre-charge relay 22 and a pre-charge resistor 24 constituting a pre-charge circuit 20 connected in parallel to the positive side relay 18. In the first embodiment, the circuit unit 10 includes a negative side relay 19 in addition to the positive side relay 18, and these positive and negative side relays 18, 19, the pre-charge relay 22, and the pre-charge resistor 24 are fixed by bolts or screws to a lower case 62 constituting an insulating case 58, which will be described later.

[0022] <Main relay (positive relay 18)> In the first embodiment, a pair of relays 18, 19 are provided in the circuit unit 10 and are arranged spaced apart from each other in the left-right direction. One relay (the left in the first embodiment) is the positive relay 18 as a main relay, and the other relay (the right in the first embodiment) is the negative relay 19. The positive and negative relays 18, 19 each have a pair of terminals 26, 26 (one of which is shown in FIG. 4) on the front side (the positive relay 18 is in the front, and the negative relay 19 is in the rear) that are spaced apart from each other in the left-right direction, and each terminal 26 is exposed on the surface of each relay 18, 19.

[0023] Each terminal 26 is an input and output terminal for each relay 18, 19. For example, in the positive relay 18, the left terminal 26 is an input terminal on the positive side, and the right terminal 26 is an output terminal on the positive side. In addition, in the negative relay 19, the left terminal 26 is an output terminal on the negative side, and the right terminal 26 is an input terminal on the negative side.

[0024] A current bus bar 28 is overlapped with each terminal portion 26 of each of the relays 18, 19 and fixed by a bolt 30. That is, the circuit unit 10 includes first and second current bus bars 28a, 28b connected to the input and output terminal portions 26, 26 of the positive relay 18, and third and fourth current bus bars 28c, 28d connected to the output and input terminal portions 26, 26 of the negative relay 19. When the circuit unit 10 is assembled, the ends of the first to fourth current bus bars 28a-28d are exposed to the outside through through windows 68a-68d provided in an insulating case 58 (upper case 60) described later, and each of the input and output connection portions 32a, 32b on the positive side and each of the output and input connection portions 32c, 32d on the negative side are configured.

[0025] 1, the input connection portion 32a on the positive electrode side and the input connection portion 32d on the negative electrode side are electrically connected to the positive and negative terminal portions (not shown) of the battery 12 by conductive members 34 made of bus bars, electric wires, etc. Also, the output connection portion 32b on the positive electrode side and the output connection portion 32c on the negative electrode side are electrically connected to the positive and negative terminal portions (not shown) of the inverter 14 by conductive members 34. Each of these connections 32a to 32d and the conductive members 34 can be fixed by a bolt 35.

[0026] As a result, a main circuit 36 ​​between the battery 12 and the inverter 14 is configured, including the relays 18, 19, the first to fourth current-carrying bus bars 28a to 28d, and the conductive members 34. In the main circuit 36, by switching the relays 18, 19 between ON and OFF, the main circuit 36 ​​between the battery 12 and the inverter 14 can be switched between a conductive state and a non-conductive state.

[0027] In addition to the first to fourth current-carrying busbars 28a to 28d, the first to fourth heat-dissipating busbars 38a to 38d are fastened to the terminals 26 of the positive and negative relays 18, 19 by bolts 30. The first to fourth heat-dissipating busbars 38a to 38d are each substantially L-shaped, and have a portion that extends in the vertical direction and a portion that bends from the lower end of the portion that extends in the vertical direction and spreads out in the horizontal direction. The upper end portions of the heat-dissipating busbars 38a to 38d are fixed to the terminals 26 of the relays 18, 19 by the bolts 30, and the lower ends of the heat-dissipating busbars 38a to 38d extend in the front-rear direction and are located below the relays 18, 19.

[0028] As described below, the portion extending in the front-rear direction at the lower end of each of these heat dissipation bus bars 38a-38d is a heat dissipation portion 40 that is in thermal contact with a heat dissipation plate 80, which is the heat dissipation target, via an insulating sheet 76 and an elastic heat dissipation sheet (or gap filler) 78. With this structure, each terminal portion 26 of each relay 18, 19 is in thermal contact with the heat dissipation plate 80 via each of the heat dissipation bus bars 38a-38d, the insulating sheet 76, and the elastic heat dissipation sheet (or gap filler) 78, and heat generated when electricity is passed through each of the relays 18, 19 can be dissipated from the heat dissipation plate 80.

[0029] <Precharge circuit 20> A pre-charge circuit 20 is connected in parallel to the main relay (positive side relay 18) in the main circuit 36. Specifically, in the pre-charge circuit 20, a pre-charge relay 22 and a pre-charge resistor 24 are connected in series. The pre-charge relay 22 and the input terminal 26 of the positive side relay 18 are electrically connected by an electric wire 42, and the pre-charge resistor 24 and the output terminal 26 of the positive side relay 18 are electrically connected by an electric wire 44. The pre-charge relay 22 and the pre-charge resistor 24 are also electrically connected by an electric wire 46.

[0030] A terminal 48 is provided on at least one end of each of the electric wires 42, 44, 46, and each terminal 48 is overlapped with each terminal portion 26 of the positive relay 18 or each terminal portion 50 (described later) of the pre-charge relay 22 and fixed by a bolt 30 or a screw 52.

[0031] <Precharge relay 22> A known pre-charge relay 22 may be used, and the structure is not limited thereto. The pre-charge relay 22 includes a pair of terminals 50, 50 (one of which is shown in FIG. 4 ) spaced apart from each other in the left-right direction. In the first embodiment, the pre-charge relay 22 is disposed with the upper side facing forward, and each terminal 50 is exposed on the upper surface of the pre-charge relay 22. A terminal 48 provided at an end of an electric wire 42 connecting the positive-side relay 18 and the pre-charge relay 22 is overlapped with an input terminal 50 (left terminal 50) of the pre-charge relay 22 and fixed by a screw 52. A terminal 48 provided at an end of an electric wire 46 connecting the pre-charge relay 22 and the pre-charge resistor 24 is overlapped with an output terminal 50 (right terminal 50) of the pre-charge relay 22 and fixed by a screw 52.

[0032] <Precharge resistor 24> The precharge resistor 24 is configured using a metal clad resistor. Since a known one can be used as the precharge resistor 24 (metal clad resistor), detailed description will be omitted, but a wire-wound resistor (not shown) is sealed in an insulated state in a metal case 54. Note that in FIG. 5, illustration of the internal structure of the precharge resistor 24 is omitted, and only the metal case 54 is shown. In other words, the metal case 54 in the precharge resistor 24 has a hollow shape, and a wire-wound resistor (not shown) is housed in an insulated state inside the metal case 54. In the first embodiment, the metal case 54 in the precharge resistor 24 has a hollow, approximately rectangular parallelepiped shape, and is arranged to extend in the front-rear direction.

[0033] As described above, the pre-charge resistor 24 is connected to the electric wire 44 connected to the positive relay 18 and the electric wire 46 connected to the pre-charge relay 22. Specifically, the electric wire 44 is connected to one end of the winding provided inside the pre-charge resistor 24, and the electric wire 46 is connected to the other end. The electric wires 44, 46 connected to both ends of the winding extend from the inside of the metal case 54 to the outside. In the first embodiment, the electric wires 44, 46 extend to the outside from one end in the length direction of the metal case 54 (the front end in the first embodiment). The terminals 48 provided at the ends of the electric wires 44, 46 are overlapped with the output terminal portion 26 of the positive relay 18 and the output terminal portion 50 of the pre-charge relay 22, respectively, and are fixed by the bolts 30 and the screws 52, respectively.

[0034] The metal case 54 in this precharge resistor 24 (metal clad resistor) has a thermal contact portion 56 that is in thermal contact with a heat sink 80 serving as a heat dissipation target, which will be described later. In the first embodiment, the metal case 54 is superimposed on the heat sink 80 via an elastic heat dissipation sheet (or gap filler) 78, which will be described later, and the thermal contact portion 56 is formed by the lower wall portion that constitutes the hollow metal case 54.

[0035] <Insulating case 58> The circuit unit 10 has an insulating case 58 that holds relays 18, 19 including a main relay (positive-side relay 18), a precharge relay 22, and a precharge resistor 24. In the first embodiment, the insulating case 58 is a hollow rectangular parallelepiped as a whole, and the left-right dimension is larger than the front-rear dimension. In particular, in the first embodiment, the insulating case 58 includes an upper case 60 and a lower case 62 that can be assembled and disassembled to each other in the vertical direction. The upper case 60 and the lower case 62 are formed of, for example, a synthetic resin. Although the method of fixing the upper case 60 and the lower case 62 is not limited, in the first embodiment, the upper case 60 is overlapped above the lower case 62 with the lower case 62 sandwiched therebetween, and a heat sink 80 (described later) is overlapped below the lower case 62, and these are fastened by bolts 63 at the four corners of the outer periphery to fix the upper case 60 and the lower case 62.

[0036] The upper case 60 is generally box-shaped and opens downward, and includes an upper bottom wall 64 and an upper peripheral wall 66 protruding downward from the outer periphery of the upper bottom wall 64. The upper bottom wall 64 is provided with rectangular through-windows 68a-68d that penetrate in the thickness direction (vertical direction) at positions corresponding to the connection portions 32a-32d of the first to fourth current-carrying bus bars 28a-28d when the circuit unit 10 is assembled.

[0037] The lower case 62 has a bottom wall 70 that is generally flat, and the bottom wall 70 has substantially the same shape as the upper case 60 in a plan view. As a result, when the upper case 60 and the lower case 62 are overlapped and fixed together, the lower opening of the upper case 60 is covered by the bottom wall 70 of the lower case 62.

[0038] The bottom wall 70 is provided with rectangular opening windows 72 (one of which is shown in FIG. 4) penetrating in the thickness direction (vertical direction) at positions corresponding to the heat dissipation sections 40 of the first to fourth heat dissipation bus bars 38a to 38d when the circuit unit 10 is assembled. The bottom wall 70 is also provided with rectangular opening windows 74 penetrating in the thickness direction (vertical direction) at positions corresponding to the thermal contact sections 56 of the precharge resistors 24 (metal clad resistors) when the circuit unit 10 is assembled. This allows the opening window 74 to expose the thermal contact sections 56 of the metal case 54 so that they can come into thermal contact with a heat sink 80 (described later) when the circuit unit 10 is assembled.

[0039] In the first embodiment, an insulating sheet 76 and an elastic heat dissipation sheet 78 are housed in a laminated state in each opening window 72 provided below each heat dissipation section 40. As a result, the first to fourth heat dissipation bus bars 38a to 38d are in contact with a heat dissipation plate 80 (described later) that is overlaid on the bottom wall section 70 in an electrically insulated state and in a thermally conductive state. The insulating sheet 76 and the elastic heat dissipation sheet 78 may be of a known material. In particular, the elastic heat dissipation sheet 78 may be a material that is a thermally conductive material and that allows the heat dissipation section 40 to contact the heat dissipation plate 80 through the insulating sheet 76 and the elastic heat dissipation sheet 78 without an air layer, and a known gap filler may also be used. In addition, the insulating sheet 76 and the elastic heat dissipation sheet 78 do not need to be separate materials, and may be composed of a single material having insulating properties and thermal conductivity. These insulating sheets 76 and elastic heat dissipation sheets (or gap fillers) 78 are fixed (e.g., glued) to the underside of each heat dissipation portion 40, for example, and are arranged in a housed state inside each opening window 72 when the circuit unit 10 is assembled.

[0040] In addition, an elastic heat dissipation sheet (or gap filler) 78 is accommodated in the opening window 74 provided below the thermal contact portion 56. As a result, the thermal contact portion 56 is in contact with a heat sink 80 (described later) in a thermally conductive state. Since the wire-wound resistor constituting the pre-charge resistor 24 is accommodated in the metal case 54 in an insulated state, even when the circuit unit 10 is in a conducting state, the metal case 54 is in an electrically insulated state, and the insulating sheet 76 does not need to be arranged in the opening window 74. The elastic heat dissipation sheet (or gap filler) 78 is fixed (for example, bonded) to the lower surface of the thermal contact portion 56 (the lower wall portion of the metal case 54), for example, and is arranged in a accommodated state inside the opening window 74 when the circuit unit 10 is assembled.

[0041] <Heat Dissipation Target (Heat Dissipation Plate 80)> The heat sink 80 is made of a metal having excellent heat dissipation properties, and is made of a metal plate having a predetermined thickness. The heat sink 80 has the same shape as the insulating case 58 in a plan view, and the insulating case 58 and the heat sink 80 are fixed by the bolts 63 in a state where they are stacked. By fixing the insulating case 58 and the heat sink 80 in a stacked state, each heat sink portion 40 of the first to fourth heat sink bus bars 38a to 38d is stacked on the heat sink 80 via the insulating sheet 76 and the elastic heat sink sheet (or gap filler) 78. In addition, by fixing the insulating case 58 and the heat sink 80 in a stacked state, the thermal contact portion 56 of the metal case 54 is stacked on the heat sink 80 via the elastic heat sink sheet (or gap filler) 78. As a result, the positive and negative side relays 18, 19 and the precharge resistor 24 are in thermal contact with the same heat sink 80.

[0042] Note that heat sink 80 may be superimposed on, for example, housing 16 of the battery pack so that heat generated in each of relays 18, 19 and pre-charge resistor 24 is dissipated from housing 16 via heat sink 80. Alternatively, heat sink 80 does not have to be superimposed on housing 16 of the battery pack, and heat generated in each of relays 18, 19 and pre-charge resistor 24 may be dissipated into the air via heat sink 80.

[0043] <Assembly of the circuit unit 10> The following describes a specific example of a method for assembling the circuit unit 10. Note that the method for assembling the circuit unit 10 is not limited to the embodiment described below.

[0044] First, the first to fourth current-carrying bus bars 28a to 28d and the first to fourth heat-dissipating bus bars 38a to 38d are overlapped with the terminal portions 26 of the relays 18, 19, and are fixed with the bolts 30. At this time, the terminals 48 provided at the ends of the electric wires 42, 44 are also overlapped with the terminal portions 26 of the positive-electrode relay 18, and are fastened together with the bolts 30. Then, the relays 18, 19, the pre-charge relay 22, and the pre-charge resistor 24 are placed on the lower case 62, which is provided with the opening windows 72, 74, and fixed with bolts or screws.

[0045] For example, the insulating sheets 76 and the elastic heat dissipation sheets (or gap fillers) 78 are superimposed and pre-fixed to the lower surfaces of the heat dissipation sections 40 of the first to fourth heat dissipation bus bars 38a to 38d. As a result, the relays 18, 19 are fixed to the lower case 62, and the insulating sheets 76 and the elastic heat dissipation sheets (or gap fillers) 78 are arranged in a housed state within the respective opening windows 72. Also, for example, the elastic heat dissipation sheets (or gap fillers) 78 are superimposed and pre-fixed to the lower surface of the lower wall portion of the metal case 54. As a result, the pre-charge resistor 24 is fixed to the lower case 62, and the elastic heat dissipation sheets (or gap fillers) 78 are arranged in a housed state within the opening windows 74.

[0046] Thereafter, the terminals 48 provided at the ends of the electric wires 42, 46 are overlapped with the terminal portions 50 of the pre-charge relay 22, and are fixed by the screws 52. Next, the heat sink 80 is overlapped on the lower surface of the lower case 62 (bottom wall portion 70) configured in this manner, and the upper case 60 is brought close to the lower case 62 from above, and the upper case 60 and the heat sink 80 are fixed by the bolts 63. This completes the circuit unit 10. In the completed state of the circuit unit 10, the connection portions 32a-32d of the first to fourth current-carrying bus bars 28a-28d are exposed to the outside from the through windows 68a-68d in the upper case 60.

[0047] The circuit unit 10 manufactured as described above is housed in, for example, the housing 16 of a battery pack, and the input connection portion 32a on the positive electrode side and the input connection portion 32d on the negative electrode side are electrically connected to the battery 12 arranged in the housing 16 by the respective conductive members 34. The output connection portion 32b on the positive electrode side and the output connection portion 32c on the negative electrode side are electrically connected to the inverter 14 provided outside the battery pack by the respective conductive members 34. In this way, the battery 12 and the inverter 14 are electrically connected via the circuit unit 10. Note that, in a state where the circuit unit 10 is arranged in the housing 16 of the battery pack, the heat sink 80 may or may not be overlapped with the housing 16.

[0048] Generally, when a vehicle is started, electricity flows from the battery to the inverter to charge the capacitor in the inverter. However, the current (inrush current) at the time of starting the vehicle is relatively large, and if the inrush current flows through the main circuit, the main relay may be damaged. To prevent this damage, a precharge resistor is provided. That is, when the vehicle is started, the positive side relay 18 is turned OFF and the precharge relay 22 is turned ON, so that power is supplied from the battery 12 to the capacitor in the inverter 14 via the precharge circuit 20, and damage to the positive side relay 18 is avoided and the capacitor is charged. After the vehicle is started, the positive side relay 18 is turned ON and the precharge relay 22 is turned OFF, so that power is supplied from the battery 12 to the inverter 14 through the main circuit 36. Therefore, when the vehicle is started, the precharge circuit 20 is energized, causing the precharge resistor 24 to heat up, and after the vehicle is started, the main circuit 36 ​​is energized, causing each relay 18, 19 to heat up. That is, the precharge resistor 24 and the positive relay 18 generate heat at different times.

[0049] In the circuit unit 10 of the first embodiment having the above-described structure, a metal clad resistor capable of handling a large current is adopted as the pre-charge resistor 24. That is, the metal clad resistor is an insulated wire-wound resistor housed in a metal case 54, and heat can be dissipated through the metal case 54. As a result, the metal clad resistor has better heat dissipation properties than, for example, a ceramic resistor, and even if multiple ceramic resistors are required, a smaller number of metal clad resistors (for example, one) can handle a large current. As a result, the mounting space for the pre-charge resistor can be reduced, and the circuit unit 10 can be made smaller in size.

[0050] The relays 18, 19 including the main relay (positive pole side relay 18), the pre-charge relay 22, and the pre-charge resistor 24 are held in an insulating case 58, and a lower case 62 constituting the insulating case 58 is formed with an opening window 74 that exposes the thermal contact portion 56 of the pre-charge resistor 24 (metal clad resistor) so that it can come into contact with a heat sink 80. This allows heat generated in the pre-charge resistor 24 to be dissipated from the heat sink 80 through the opening window 74.

[0051] In particular, the thermal contact portion 56 is in contact with the heat sink 80 via an elastic heat dissipation sheet (or gap filler) 78. By providing the elastic heat dissipation sheet (or gap filler) 78 between the thermal contact portion 56 and the heat sink 80 in this manner, no air layer is interposed between the thermal contact portion 56 and the heat sink 80, improving the heat dissipation efficiency.

[0052] The heat sink 80, with which the thermal contact portion 56 is in thermal contact, is also in thermal contact with the positive relay 18. This makes it possible to configure a common heat dissipation path for the pre-charge resistor 24 and the main relay (positive relay 18), which generate heat at different times, and prevents an increase in the number of parts, etc., compared to the case where separate heat dissipation paths are configured for the pre-charge resistor 24 and the main relay (positive relay 18).

[0053] <Modification> Although the first embodiment has been described above as a specific example of the present disclosure, the present disclosure is not limited to this specific description. Modifications, improvements, etc. within the scope of achieving the object of the present disclosure are included in the present disclosure. For example, the following modified examples of the embodiment are also included in the technical scope of the present disclosure.

[0054] (1) In the above embodiment, the heat dissipation target is the heat dissipation plate 80 made of a metal plate-like body, but the present invention is not limited to this embodiment. That is, as shown in FIG. 6, the heat dissipation target may be a metal plate 92 that constitutes the housing 16 of the battery 12, which is an on-board power source, and has a refrigerant flow path 90 through which a refrigerant (not shown) flows inside. Specifically, the metal plate 92 is constituted by, for example, the bottom wall of the housing 16, and the refrigerant flow path 90 is formed inside the metal plate 92. Note that a known refrigerant is used as the refrigerant that flows through the refrigerant flow path 90. Also, the extension direction and length of the refrigerant flow path 90 shown in FIG. 6 are merely examples, and the extension direction and length of the refrigerant flow path are not limited. Even if the heat dissipation target is such a metal plate 92, the circuit unit 10 is overlapped and fixed, and the thermal contact portion 56 of the pre-charge resistor 24 (metal clad resistor) is thermally contacted, so that the same effect as in the above embodiment can be achieved. Even when the circuit unit 10 is placed and fixed on the metal plate 92 formed by the bottom wall portion of the housing 16 in this manner, a heat sink 80 as in the above embodiment may be provided between the circuit unit 10 and the metal plate 92.

[0055] (2) In the above embodiment, the lower case 62 has the opening windows 72 at positions corresponding to the heat dissipation portions 40 of the heat dissipation bus bars 38a-38d of the relays 18, 19, and the opening window 74 at a position corresponding to the thermal contact portion 56 of the precharge resistor 24, but the present invention is not limited to this embodiment. The above opening windows are not essential to the lower case, and the heat dissipation portions and the thermal contact portions may be in thermal contact with the bottom wall portion of the lower case formed of a synthetic resin having good thermal conductivity. In this case, the bottom wall portion of the lower case constitutes the heat dissipation target. Note that the heat dissipation bus bars, insulating sheets, and elastic heat dissipation sheets (or gap fillers) are not essential to the circuit unit according to the present disclosure.

[0056] (3) The structure of the pre-charge resistor (metal clad resistor) is not limited as long as it has a metal case. In the above embodiment, the electric wires 44, 46 extending from the pre-charge resistor 24 extend from one end (front end) in the longitudinal direction of the pre-charge resistor 24, but the two electric wires may extend from both sides in the longitudinal direction of the pre-charge resistor.

[0057] (4) The shape, length, etc. of each conductive member 34 shown in FIG. 1 are merely examples, and do not limit the manner in which an on-board power supply or a load is connected to the circuit unit.

[0058] (5) In the above embodiment, the heat sink 80 may have a divided structure, and may be composed of, for example, two members separated from each other in the left-right direction. That is, the left heat sink may be in thermal contact with the heat sink portions 40 of the heat sink bus bars 38a, 38b in the main relay (positive relay 18) and the thermal contact portion 56 in the pre-charge resistor 24, and the right heat sink may be in thermal contact with the heat sink portions 40 of the heat sink bus bars 38c, 38d in the negative relay 19. Note that the heat sink (for example, the heat sink) may simply be provided at a position corresponding to the thermal contact portion of the metal case in the pre-charge resistor.

[0059] (6) In the above embodiment, the precharge circuit 20 is connected in parallel to the positive side relay 18. However, the precharge circuit may be connected in parallel to the negative side relay. In this case, the main relay is constituted by the negative side relay. [Explanation of symbols]

[0060] 10 Circuit Unit 12 Battery (on-board power supply) 14 Inverter (load) 16 Case 18 Positive relay (main relay) 19 Negative relay 20 Precharge Circuit 22 Precharge relay 24 Precharge resistor 26 Terminal section 28 Current carrying busbar 28a First current busbar 28b Second current busbar 28c 3rd current busbar 28d 4th current busbar 30 Volts 32a (positive input) connection 32b (positive output) connection 32c (negative output) connection 32d (negative input) connection 34 Conductive materials 35 Volts 36 Main Circuit 38a~38d Heat dissipation busbars 40 Heat dissipation part 42,44,46 Electric wire 48 terminals 50 Terminal section 52 Screw 54 Metal Case 56 Thermal contacts 58 Insulating Case 60 Upper Case 62 Lower case 63 Volts 64 Upper bottom wall 66 Upper peripheral wall 68a~68d Through window 70 Bottom wall 72,74 Opening window 76 Insulation sheet 78 Elastic heat dissipation sheet (or gap filler) 80 Heat sink (heat dissipation target) 90 Coolant flow path 92 Metal plate (heat dissipation target)

Claims

1. A circuit unit connected between an on-board power supply and a load, a main relay that switches between energization and de-energization between the on-board power supply and the load; a precharge relay and a precharge resistor that configure a precharge circuit connected in parallel to the main relay; The precharge resistor is constructed using a metal clad resistor, A circuit unit, wherein the metal case of the metal clad resistor has a thermal contact portion that is in thermal contact with a heat dissipation target.

2. an insulating case that holds the main relay, the precharge relay, and the precharge resistor; 2. The circuit unit according to claim 1, wherein the insulating case has an opening window that exposes the thermal contact portion of the metal case of the metal clad resistor so as to be in thermal contact with the heat dissipation target.

3. 3. The circuit unit according to claim 1, wherein the thermal contact portion of the metal case is in contact with the heat dissipation target via an elastic heat dissipation sheet or a gap filler.

4. 3. The circuit unit according to claim 1, wherein the heat dissipation target with which the thermal contact portion of the metal clad resistor is in thermal contact is a heat sink in thermal contact with the main relay.

5. 3. The circuit unit according to claim 1, wherein the heat dissipation target with which the thermal contact portion of the metal clad resistor is in thermal contact is a metal plate that constitutes a housing of the vehicle-mounted power supply and has a refrigerant flow path through which a refrigerant flows.

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