Circuit unit

Abstract

Disclosed is a circuit unit of a type in which a circuit board is inserted from a side opening of a case, the circuit unit being capable of constituting a heat dissipation path in which displacement of a heat conduction member is suppressed.　A circuit unit 10 comprises: a case 14 having a side opening portion 12; a circuit board 16 inserted into the case 14 through the side opening portion 12 and disposed; an electric component 18 mounted on the circuit board 16; an opening window 22 that penetrates an opposing surface 20 facing the electric component 18 in the case 14 and exposes the electric component 18 to the outside; and a heat sink 26 that can be passed through the opening window 22 and is fixed to the circuit board 16 in a state of being in contact with the electric component 18 via a heat conduction member 24.

Description

Circuit unit

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

[0002] Patent Document 1 discloses a circuit unit of a type in which a circuit board mounted with electrical components is slid and inserted from a side opening of a case. In this structure, in order to secure a heat dissipation path for electrical components that generate a large amount of heat, a protrusion protruding toward the electrical component from a portion of the case where a heat sink is provided is provided, and a structure in which a gap between the electrical component and the protrusion is filled with a heat conductive member such as TIM (Thermal Interface Material) is proposed.

[0003] Japanese Patent Application Laid-Open No. 2024-138933

[0004] However, in the structure of Patent Document 1, when inserting the circuit board from the side opening of the case, the heat conductive member placed on the upper surface of the electrical component is displaced due to interference with the protrusion, which causes a gap between the electrical component and the protrusion, and thus there is a risk that the desired heat dissipation performance cannot be ensured.

[0005] Therefore, the present disclosure provides a circuit unit of the type in which the circuit board is inserted from the side opening of the case, which can form a heat dissipation path that suppresses displacement of the heat conductive member.

[0006] The circuit unit of the present disclosure comprises: a case having a side opening; a circuit board inserted into the case through the side opening and arranged therein; an electrical component mounted on the circuit board; an opening window penetrating through a facing surface of the case that faces the electrical component, and exposing the electrical component to the outside; and a heat sink that can pass through the opening window and is fixed to the circuit board in a state of being in contact with the electrical component via a heat conductive member.

[0007] According to the present disclosure, in a circuit unit of the type in which the circuit board is inserted from the side opening of the case, a heat dissipation path that suppresses displacement of the heat conductive member can be formed.

[0008] Figure 1 is a perspective view showing a circuit unit according to Embodiment 1. Figure 2 is a plan view of the circuit unit shown in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is an exploded perspective view of the circuit unit shown in Figure 1. Figure 5 is an explanatory diagram illustrating the assembly process of the circuit unit according to Embodiment 2.

[0009] <Description of Embodiments of the Disclosure> First, embodiments of the Disclosure will be listed and described. The circuit unit of the Disclosure includes: (1) a case having a lateral opening; a circuit board inserted into the case and disposed through the lateral opening; electrical components mounted on the circuit board; an opening window provided through a surface of the case facing the electrical components to expose the electrical components to the outside; and a heat sink that is insertable through the opening window and fixed to the circuit board in contact with the electrical components via a heat conductive member.

[0010] According to the circuit unit of this disclosure, in a circuit unit in which a circuit board is inserted from a side opening of the case, an opening window that exposes the electrical components mounted on the circuit board to the outside is provided through the opposite surface of the case. This makes it possible to insert the circuit board from the side opening of the case and then insert the heat sink through the opening window of the case to bring it into contact with the electrical components via a heat conductive member. Furthermore, the heat sink is fixed to the circuit board in a state where it is in contact with the electrical components via the heat conductive member. This makes it possible to fix the heat sink to the circuit board in a state where it is in contact with the electrical components via the heat conductive member before inserting the circuit board into the case. As a result, compared to conventional structures in which the heat conductive member placed on the upper surface of the electrical components interferes with a protrusion when inserting the circuit board, the displacement of the heat conductive member can be advantageously suppressed, and a stable heat dissipation path from the electrical components to the heat sink can be secured. Therefore, the desired heat dissipation performance can be stably secured by a heat dissipation path that suppresses the displacement of the heat conductive member.

[0011] (2) In the above (1), it is preferable that there is a cover that closes the opening window, and that the cover has multiple openings through it. This is because by closing the opening window with the cover, it is possible to prevent foreign objects from entering the case by passing through the opening window. In addition, since the cover has multiple openings through it, the heat sink can be cooled by the outside air passing through the openings, and the hot air around the heat sink inside the case can be discharged to the outside, thereby further improving the heat dissipation performance.

[0012] (3) In (2) above, it is preferable that the cover has a cylindrical wall that protrudes toward the circuit board and surrounds the electrical component. By surrounding the electrical component with a peripheral wall protruding from the cover, heat propagation to the area around the electrical component is prevented, and heat can be dissipated from the electrical component through a heat dissipation path from the heat sink through an opening (window).

[0013] (4) In (2) or (3) above, it is preferable that the lid is bolted to the circuit board together with the heat sink while the opening window is closed. By using a structure in which the heat sink is bolted to the circuit board, the lid can be fixed to the board and the lid can be held in a state where the opening window of the case is closed via the board. This makes it possible to provide a circuit unit in which the opening window is held by the lid while reducing the number of parts and miniaturizing the unit.

[0014] <Details of Embodiments of the Disclosure> Specific examples of the circuit units of the Disclosure will be described below with reference to the drawings. However, the Disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the Claims as indicated by the Claims.

[0015] <Embodiment 1> Hereinafter, a circuit unit 10 according to Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 4. This circuit unit 10 constitutes an electrical junction box mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and distributes power from a battery as a power source to various loads. The circuit unit 10 can be positioned in any orientation, but hereafter, "upper" will be described as the upper part in Figure 3, "lower" as the lower part in Figure 3, "left" as the upper part in Figure 2, "right" as the lower part in Figure 2, "front" as the left in Figure 2, and "rear" as the right in Figure 2. In addition, in the following description, for multiple identical components, only some components may be given reference numerals, and the reference numerals for other components may be omitted.

[0016] <Circuit Unit 10> The circuit unit 10 comprises a case 14 having a front opening 12 as a lateral opening, a circuit board 16 inserted into the case 14 through the lateral opening (front opening 12) and arranged therein, and electrical components 18 mounted on the circuit board 16. The circuit unit 10 also includes an opening window 22 that penetrates the opposing surface of the case 14 facing the electrical components 18 (the lower surface 20 of the upper wall portion 28 of the case 14, which will be described later) to expose the electrical components 18 to the outside, and a heat sink 26 that can be inserted through the opening window 22 and is fixed to the circuit board 16 in contact with the electrical components 18 via a heat conductive member 24.

[0017] <Case 14> Case 14 is a hollow, substantially rectangular box shape overall, and in Embodiment 1 it is made of synthetic resin. As described above, Case 14 has a lateral opening that opens to the side (in a direction perpendicular to the vertical direction), and in Embodiment 1, Case 14 has a front opening 12 that opens forward as a lateral opening. That is, Case 14 has an upper wall portion 28 and a lower wall portion 30 that face each other at a predetermined opposing distance in the vertical direction, and a left wall portion 32 and a right wall portion 34 that face each other at a predetermined opposing distance in the left-right direction. Furthermore, the rear ends of each of these wall portions 28, 30, 32, 34 are covered by a rear wall portion 36, and the front ends of each of these wall portions 28, 30, 32, 34 constitute the front opening 12. Each of the wall portions 28, 30, 32, 34, 36 is configured as a substantially rectangular plate. Furthermore, a circuit board 16 with electrical components 18 mounted on it can be inserted into the case 14 through the front opening 12.

[0018] Furthermore, the inner surfaces of each wall portion 28, 30, 32, 34, 36 constituting the case 14 may be provided with guide portions to guide the insertion of the circuit board 16 into the case 14, and support portions to support the circuit board 16 after it has been inserted into the case 14. In addition, after the circuit board 16 has been inserted into the case 14, for example, a cover (not shown) may be assembled over the front opening 12 of the case 14 to cover the front opening 12, thereby preventing the circuit board 16 from falling out of the case 14.

[0019] As described above, since the circuit board 16 on which the electrical components 18 are mounted is arranged inside the case 14, the lower surface 20 of the upper wall portion 28 and the upper surface of the lower wall portion 30 of the case 14 are facing surfaces that face the electrical components 18 in the case 14. In Embodiment 1, an opening window 22 is formed on the lower surface 20 of the upper wall portion 28, which is this facing surface, to expose the electrical components 18 to the outside, and the opening window 22 is formed to penetrate the upper wall portion 28 in the thickness direction (vertical direction). That is, in a plan view, the opening window 22 is provided in a shape larger than the electrical components 18, and in a plan view, the opening window 22 is formed in a rectangular shape.

[0020] <Lid 38> The circuit unit 10 has a lid 38 that closes the opening window 22. The lid 38 is a roughly box-shaped or roughly bottomed cylindrical shape that opens downward, and is made of a hard material such as metal or synthetic resin. In Embodiment 1, the lid 38 is made of synthetic resin. This lid 38 has an upper bottom wall portion 40 and a cylindrical wall 42 that protrudes downward from the outer peripheral edge of the upper bottom wall portion 40. That is, the cylindrical wall 42 of the lid 38 protrudes downward toward the circuit board 16 and surrounds the electrical components 18.

[0021] In particular, in Embodiment 1, the lid 38 is shaped to correspond to the opening window 22, and in plan view, the upper bottom wall portion 40 is rectangular, and the cylindrical wall 42 is rectangular. Furthermore, through holes 46 are formed at the four corners of the upper bottom wall portion 40, through which bolts 44 for bolting the lid 38 to the circuit board 16 are inserted, penetrating the upper bottom wall portion 40 in the vertical direction. In addition, a plurality of openings 48 penetrating in the vertical direction are formed in the upper bottom wall portion 40 of the lid 38. Each of these openings 48 is formed in a region that overlaps with, for example, the electrical components 18 and the heat sink 26 in plan view. The shape of each of these openings 48 is not limited, and for example, it may be a slit shape extending in the front-to-back direction and / or left-to-right direction, but in Embodiment 1, each opening 48 is formed as a circular through hole. The inner diameter of each opening 48 is made sufficiently small to create a micro-porous structure that prevents, for example, water droplets from entering. This ensures liquid-tightness while providing openings 48 in the upper bottom wall 40, preventing water from entering the case 14.

[0022] <Circuit Board 16> The circuit board 16 may be, for example, a known printed circuit board, and is a substantially rectangular flat plate that extends horizontally (in a direction perpendicular to the vertical direction), with an electrical circuit (not shown) printed on at least one of its upper and lower surfaces. The circuit board 16 (printed circuit board) may be a rigid board or a flexible printed circuit board (FPC) that can be flexibly deformed. As described above, electrical components 18 are mounted on the electrical circuit on the circuit board 16, and other electrical components besides the above-mentioned electrical components 18 may also be mounted.

[0023] Furthermore, fastening portions 50 are formed around the mounting positions of the electrical components 18 on the circuit board 16, into which the bolts 44 for fixing the cover 38 are fastened. In Embodiment 1, approximately cylindrical fastening portions 50 are provided at four locations around the mounting positions of the electrical components 18, and female threads are formed on the inner circumferential surface of each fastening portion 50 into which the male threads of each bolt 44 are screwed. In particular, in Embodiment 1, each fastening portion 50 is integrally formed with respect to the circuit board 16 and is formed with a predetermined protrusion dimension (vertical dimension) relative to the circuit board 16. The upward protrusion dimension of each fastening portion 50 is such that it does not interfere with the upper wall portion 28 when the circuit board 16 is inserted into the case 14 through the front opening 12.

[0024] <Electrical Components 18> The electrical components 18 are not limited to those that are mounted on the electrical circuit on the circuit board 16 and generate heat when current is applied, but relatively low-profile electrical components such as field-effect transistors (FETs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) are preferably used. As described above, when the cover 38 is fixed, the electrical components 18 are covered by the cylindrical wall 42, and for example, when multiple electrical components 18 are mounted on the circuit board 16, the electrical components 18 that generate relatively large amounts of heat are arranged to be located inside the cylindrical wall 42. Electrical components that generate relatively small amounts of heat may be arranged to be located inside the cylindrical wall 42 or to be located outside it.

[0025] <Thermal Conducting Member 24> A known TIM is used as the thermal conducting member 24, and for example, it has good thermal conductivity as well as electrical insulation properties. The thermal conducting member 24 is, for example, in the form of a substantially rectangular sheet and is sandwiched between the electrical component 18 and the heat sink 26 in the vertical direction. The shape of the thermal conducting member 24 is not limited, and for example, it may be in the form of a gel and applied to the lower surface of the heat sink 26. The thermal conducting member 24 may be the same size as the electrical component 18 in a plan view, but it may be larger or smaller than the electrical component 18 in a plan view.

[0026] <Heat sink 26> The heat sink 26 is made of a metal with good thermal conductivity. In Embodiment 1, the heat sink 26 comprises a base portion 52 that widens into a roughly rectangular flat plate shape at its lower end, and a plurality of fin portions 54 that protrude upward from the base portion 52. Through holes 56 are formed at the four corners of the base portion 52 through which bolts for fixing the heat sink 26 to the circuit board 16 are inserted. In Embodiment 1, the heat sink 26 and the cover 38 are fixed together by common bolts 44, and when the circuit unit 10 is assembled, the through holes 56 in the heat sink 26 and the through holes 46 in the cover 38 are formed in the same position in a plan view (projection in the vertical direction).

[0027] Furthermore, in Embodiment 1, a plurality of fin portions 54 are arranged in parallel in the front-to-back direction, and each fin portion 54 is formed to be narrower as it moves upward, with the width dimension in the parallel direction (front-to-back width dimension) gradually decreasing. When the circuit unit 10 is assembled, the protruding tip surface (upper end surface) of each fin portion 54 may be in contact with the lower surface of the upper bottom wall portion 40 of the lid 38, or it may be slightly separated from the lower surface of the upper bottom wall portion 40 and facing it.

[0028] <Assembly Method of Circuit Unit 10> The following describes a specific example of how to assemble the circuit unit 10. However, the assembly method of the circuit unit 10 is not limited to the description below.

[0029] First, electrical components 18 are mounted on the circuit board 16 within the area enclosed by each fastening portion 50. Then, the circuit board 16 with the mounted electrical components 18 is inserted through the front opening 12 of the case 14, and the circuit board 16 is placed and supported on a support portion (not shown) inside the case 14. In this state, the electrical components 18 on the circuit board 16 are exposed to the outside through the opening window 22 of the case 14. Next, a heat sink 26, for example, with a heat conductive member 24 fixed to its lower surface, is inserted into the case 14 through this opening window 22, and the base portion 52 of the heat sink 26 and the electrical components 18 are superimposed via the heat conductive member 24. Then, each insertion hole 56 in the heat sink 26 and each fastening portion 50 on the circuit board 16 are connected in the vertical direction.

[0030] Next, the cover 38 is brought closer from above the heat sink 26, and the lower portion of the cylindrical wall 42 of the cover 38 is inserted into the case 14 through the opening window 22. When the cover 38 is inserted all the way down, the lower end of the cover 38 abuts against the outer periphery of the fastening portion 50 on the circuit board 16, and the area around the electrical components 18, the heat conductive member 24, and the heat sink 26 is covered by the cover 38. In this state, the protruding tip surface (upper end surface) of each fin portion 54 on the heat sink 26 abuts against, for example, the lower surface of the upper bottom wall portion 40 of the cover 38, and each insertion hole 46 on the cover 38 is in the same position as each insertion hole 56 and each fastening portion 50 in a plan view. Then, by inserting each bolt 44 through each of these insertion holes 46, 56 and fastening them to each fastening portion 50, the cover 38 is bolted to the circuit board 16 together with the heat sink 26, with the opening window 22 closed. Subsequently, if necessary, the circuit unit 10 of Embodiment 1 is completed by covering the front opening 12 of the case 14 with a cover (not shown) or the like.

[0031] In the circuit unit 10 manufactured in this manner, for example, the electrical circuits on the circuit board 16 are electrically connected to the battery and various loads, thereby creating an electrical conductivity between the battery and the various loads. When the electrical components 18 on the circuit board 16 are energized, they generate heat, and this heat is transferred to the heat sink 26 via the heat conductive member 24, from where it is dissipated into the outside space.

[0032] In the circuit unit 10 of Embodiment 1, which has the structure described above, the circuit board 16 is inserted through the front opening 12 on the side (front), while the heat conductive member 24 and heat sink 26 that are superimposed on the electrical components 18 on the circuit board 16 are assembled from above through the opening window 22. As a result, the risk of the heat conductive member 24 interfering with the case 14 and shifting off the electrical components 18 when inserting the circuit board 16 into the case 14 can be reduced. In addition, since the heat sink 26 is not inserted into the case 14 through the front opening 12, the height dimension of the heat sink 26 can be made relatively large, thereby improving heat dissipation performance.

[0033] The circuit unit 10 has a cover 38 that closes the opening window 22, and the cover 38 has a plurality of openings 48 that pass through it. As a result, the heat transferred to each fin portion 54 of the heat sink 26 is dissipated to the outside space through each opening 48, further improving the heat dissipation performance. In particular, by making the inner diameter of each opening 48 sufficiently small, liquid tightness can be ensured, and water can be prevented from entering the case 14 through each opening 48.

[0034] The cover 38 has a cylindrical wall 42 that protrudes toward the circuit board 16 and surrounds the electrical components 18. This cylindrical wall 42 is provided to surround, for example, an electrical component 18 that generates a relatively large amount of heat, thereby preventing adverse thermal effects on electrical components located outside the cylindrical wall 42 on the circuit board 16. Furthermore, the heat from the electrical components 18 is prevented from escaping to the outside of the cylindrical wall 42, allowing for efficient heat dissipation via the heat sink 26.

[0035] The cover 38 is bolted to the circuit board 16 together with the heat sink 26 while covering the opening window 22. This avoids the need to separately fix the cover 38 and the heat sink 26 to the circuit board 16, thereby reducing the number of parts and assembly time, and also suppressing the increase in size of the circuit unit 10.

[0036] <Embodiment 2> Hereinafter, a specific example of a circuit unit 60 and an assembly method for the circuit unit 60 according to Embodiment 2 of the present disclosure will be described with reference to Figure 5. The basic structure of the circuit unit 60 in Embodiment 2 is the same as in Embodiment 1, but Embodiment 2 differs from Embodiment 1 in that, in addition to the circuit board 16 and electrical components 18, the heat conductive member 24 and the heat sink 62 are also inserted into the case 14 through the front opening 12. Hereinafter, the differences from Embodiment 1 will be mainly described, and the same members and parts as in Embodiment 1 will be denoted by the same reference numerals in the figures, and detailed explanations will be omitted.

[0037] In other words, in Embodiment 1, when the heat sink 26 is fixed on the circuit board 16, the protruding tips (upper ends) of each fin portion 54 on the heat sink 26 are located above the upper wall portion 28 of the case 14. In contrast, in Embodiment 2, when the heat sink 62 is fixed on the circuit board 16, the protruding tips of each fin portion 54 on the heat sink 62 are formed with a protrusion dimension that does not reach the upper wall portion 28 of the case 14. As a result, instead of placing the heat sink 62 inside the case 14 through the opening window 22 in the upper wall portion 28, the heat sink 62 can be inserted through the front opening 12 without interfering with the upper wall portion 28, even when the heat sink 62 is assembled to the circuit board 16. Such a heat sink 62 is fixed to the circuit board 16 by screws 63 that are inserted through each insertion hole 56 in the base portion 52.

[0038] Furthermore, in Embodiment 2, similar to Embodiment 1, the circuit unit 60 has a cover 64 that closes the opening window 22. The upper bottom wall portion 40 of this cover 64 is rectangular in shape and larger than the opening window 22 in a plan view, and through holes 46 through which screws 66 are inserted are formed at the four corners of the upper bottom wall portion 40, and fastening portions 68 are provided at four locations around the opening window 22 on the upper wall portion 28, at positions corresponding to each through hole 46, through which each screw 66 is fastened.

[0039] Therefore, the circuit unit 60 of Embodiment 2 is assembled, for example, by the following method. First, as shown in the upper left of Figure 5, the heat sink 62 is placed on top of the electrical components 18 on the circuit board 16 via the heat conductive member 24, and the heat sink 62 and the circuit board 16 are fixed together with screws 63. Then, as shown in the upper right of Figure 5, the assembly of the circuit board 16, electrical components 18, heat conductive member 24, and heat sink 62 is inserted into the case 14 through the front opening 12 of the case 14.

[0040] When the above assembly is inserted into the case 14, the heat sink 62 is exposed to the outside through the opening window 22 of the upper wall portion 28, as shown in the lower left of Figure 5. In other words, in a plan view, the heat sink 62 is formed to be smaller than the opening window 22, and the heat sink 62 is made capable of passing through the opening window 22. Next, as shown in the middle of the lower section of Figure 5, the cover 64 is assembled from above to close the opening window 22 and fixed to the upper wall portion 28 with screws 66. This completes the circuit unit 60 of Embodiment 2, as shown in the lower right of Figure 5. In this state, the cylindrical wall 42 of the cover 64 surrounds the outer periphery of the electrical components 18, the heat conductive member 24, and the heat sink 62.

[0041] In the circuit unit 60 of Embodiment 2, which has the structure described above, the circuit board 16 to which the heat sink 62 is assembled is inserted through the front opening 12. During this insertion, the fin portions 54 of the heat sink 62 do not interfere with the upper wall portion 28 of the case 14, and therefore, displacement of the heat conductive member 24 sandwiched between the electrical components 18 and the heat sink 62 can be prevented. Therefore, the same effects as in Embodiment 1 can be achieved in the circuit unit 60 of Embodiment 2. In particular, in Embodiment 1, the cover 38 and the heat sink 26 were fixed with common bolts 44, so the length of each bolt 44 was relatively large. In contrast, in Embodiment 2, the heat sink 26 is fixed to the circuit board 16 and the cover 64 is fixed to the upper wall portion 28 of the case 14, so relatively small screws 63 and 66 can be used for fixing them, improving the handling of the components.

[0042] <Modifications> Although Embodiments 1 and 2 have been described in detail above as specific examples of the present disclosure, the present disclosure is not limited by these specific descriptions. Modifications, improvements, etc., to the extent that they can achieve the objectives of the present disclosure are included in the present disclosure. For example, the following modifications of embodiments are also included in the technical scope of the present disclosure.

[0043] (1) In the above embodiment, both the case 14 and the lids 38, 64 are formed of synthetic resin, but the case and / or the lid may be formed of metal.

[0044] (2) In the above embodiment, both the heat sinks 26, 62 have respective fin portions 54, but the heat sink does not need to include a fin portion. From the viewpoint of heat dissipation, it is preferable that the heat sink is provided with an uneven shape such as a fin portion to increase the surface area.

[0045] (3) In the above embodiment, both the lids 38, 64 are formed in a substantially rectangular bottomed cylindrical shape, but the present invention is not limited to this aspect, and may be formed in a substantially circular bottomed cylindrical shape. That is, the upper bottom wall portion of the lid may be circular, and the cylindrical wall may be cylindrical. Even in that case, for example, the lid can be bolted to the circuit board or the upper wall portion with bolts or screws at four positions on the circumference of the outer peripheral portion of the upper bottom wall portion. Similarly, the base portion of the heat sink may also be circular in a plan view.

[0046] (4) In the above embodiment, FETs and MOSFETs are described as the electrical component 18, but this is merely an example and is not limiting.

[0047] 10 Circuit unit (Embodiment 1) 12 Front opening (side opening) 14 Case 16 Circuit board 18 Electrical component 20 Lower surface (opposing surface) 22 Opening window 24 Heat conductive member 26 Heat sink 28 Upper wall portion 30 Lower wall portion 32 Left wall portion 34 Right wall portion 36 Rear wall portion 38 Lid 40 Upper bottom wall portion 42 Cylindrical wall 44 Bolt 46 Insertion hole 48 Opening 50 Fastening portion 52 Base portion 54 Fin portion 56 Insertion hole 60 Circuit unit (Embodiment 2) 62 Heat sink 63 Screw 64 Lid 66 Screw 68 Fastening portion

Claims

1. A circuit unit comprising: a case having a lateral opening; a circuit board inserted into the case and positioned through the lateral opening; electrical components mounted on the circuit board; an opening window provided through a surface of the case facing the electrical components, exposing the electrical components to the outside; and a heat sink fixed to the circuit board, allowing the opening window to be inserted and in contact with the electrical components via a heat conductive member.

2. The circuit unit according to claim 1, further comprising a cover that closes the opening window, wherein a plurality of openings are provided through the cover.

3. The circuit unit according to claim 2, wherein the cover has a cylindrical wall that protrudes toward the circuit board and surrounds the electrical components.

4. The circuit unit according to claim 2 or 3, wherein the cover is bolted to the circuit board together with the heat sink while the opening window is closed.

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