Inverter unit and motor unit

Abstract

One embodiment of the inverter unit of the present invention is an inverter unit that converts direct current into alternating current and supplies it to a motor. The inverter unit has: a housing having a first storage chamber and a second storage chamber that are open to the outside; a first circuit board that is located in the first storage chamber; a wiring portion that connects the first circuit board and an external power supply device; a first cover that is fixed to the housing and covers the opening of the first storage chamber; and a second cover that is fixed to the housing and covers the opening of the second storage chamber. The wiring portion has a connection portion that is connected to the external power supply device. The connection portion is located in the second storage chamber.

Description

Technical Field

[0001] The present invention relates to an inverter unit and a motor unit. Background Art

[0002] In order to control the motor, an inverter unit is known, which includes an inverter and a housing for accommodating the inverter. Patent document 1 describes an electric drive unit (inverter unit) in which components are stacked and fixed in order of size in consideration of compactness, assembly, manufacturability, and shock resistance.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-199363 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The inverter unit is connected to a connection terminal extending from an external power supply device. In the connection process of connecting the inverter unit to the connection terminal, the case of the inverter unit is opened, so the circuit board in the case may be exposed to the outside and contaminated by dust.

[0008] In view of the above circumstances, one object of the present invention is to provide an inverter unit and a motor unit capable of protecting a circuit board from contamination.

[0009] Means for solving problems

[0010] One embodiment of the inverter unit of the present invention is an inverter unit that converts direct current into alternating current and supplies it to a motor. The inverter unit has: a housing having a first storage chamber and a second storage chamber that are open to the outside; a first circuit board that is located in the first storage chamber; a wiring portion that connects the first circuit board and an external power supply device; a first cover that is fixed to the housing and covers the opening of the first storage chamber; and a second cover that is fixed to the housing and covers the opening of the second storage chamber. The wiring portion has a connection portion that is connected to the external power supply device. The connection portion is located in the second storage chamber.

[0011] One aspect of the motor unit of the present invention includes: the inverter unit described above; and the motor to which an alternating current is supplied from the inverter unit.

[0012] Effects of the Invention

[0013] According to one aspect of the present invention, an inverter unit and a motor unit capable of protecting a circuit board from contamination are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a top view of an inverter unit according to one embodiment.

[0015] Figure 2 An inverter unit is an embodiment of the Figure 1 Schematic diagram of the cross section of line II-II.

[0016] Figure 3 It is a top view of the inverter unit according to one embodiment in which the first cover and the second cover are omitted.

[0017] Figure 4 is a bottom view of a housing according to one embodiment. DETAILED DESCRIPTION

[0018] Hereinafter, an inverter unit according to an embodiment of the present invention will be described with reference to the drawings. In order to make each structure easier to understand, the scale, number, etc. of each structure in the following drawings may be different from the actual structure.

[0019] In the following description, the gravity direction is defined based on the positional relationship when the inverter unit 1 is mounted on a vehicle located on a horizontal road surface. In addition, the XYZ coordinate system is appropriately shown in the accompanying drawings as a three-dimensional rectangular coordinate system. In the XYZ coordinate system, the Z-axis direction represents the vertical direction (i.e., the up and down direction), the +Z direction is the upper side (the opposite side of the gravity direction), and the -Z direction is the lower side (the gravity direction). In addition, the X-axis direction is a direction perpendicular to the Z-axis direction, indicating the front and rear direction of the vehicle equipped with the inverter unit 1. The Y-axis direction is a direction perpendicular to both the X-axis direction and the Z-axis direction, indicating the width direction of the vehicle (left and right direction).

[0020] Hereinafter, an inverter unit 1 according to an exemplary embodiment of the present invention and a motor unit 3 including the inverter unit 1 will be described with reference to the drawings.

[0021] Figure 1 It is a top view of the inverter unit 1 .

[0022] The inverter unit 1 is disposed in the motor unit 3. The motor unit 3 includes the inverter unit 1, the motor 2, and a motor case 3a. The motor unit 3 may include a speed reduction device (not shown) for reducing the rotation speed of the motor 2.

[0023] The motor unit 3 of the present embodiment is mounted on a vehicle using a motor as a power source, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHV), or an electric vehicle (EV), and is used as the power source.

[0024] The motor case 3a has a storage space inside for storing the motor 2. The motor 2 is stored in the storage space of the motor case 3a. The inverter unit 1 is fixed to the outer peripheral surface of the motor case 3a.

[0025] The motor 2 is supplied with AC current by the inverter unit 1. The motor 2 is controlled by the inverter unit 1. The motor 2 has a rotor 2a that rotates around a motor axis J extending in the horizontal direction and a stator 2b located radially outside the rotor 2a. The coil wire of the stator 2b is connected to the inverter unit 1.

[0026] Figure 2 is the inverter unit 1 along Figure 1 Schematic diagram of the cross section of line II-II. Figure 3 It is a plan view of the inverter unit 1 with the first cover 40 and the second cover 50 omitted.

[0027] The inverter unit 1 converts the DC current into AC current and supplies it to the motor 2. Figure 2 As shown, the inverter unit 1 has a housing 10, a control substrate (second circuit board) 21, a power substrate (first circuit board) 22, a capacitor 23, an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, hereinafter referred to as IGBT) 24, a first bus bar 31, a second bus bar 32, a bus bar retainer 33, a cover opening detection device 60, a first cover 40 and a second cover 50.

[0028] The housing 10 has a storage space 13 inside. The storage space 13 stores a control board 21, a power board 22, a capacitor 23, an IGBT 24, a first bus bar 31, a second bus bar 32, a bus bar holder 33, and a cover opening detection device 60.

[0029] The storage space 13 is divided into a first storage chamber 11 and a second storage chamber 12. That is, the first storage chamber 11 and the second storage chamber 12 are provided in the housing 10. The first storage chamber 11 and the second storage chamber 12 are open to the outside. The openings of the first storage chamber 11 and the second storage chamber 12 are oriented upward. That is, the first storage chamber 11 and the second storage chamber 12 are open in the same direction. Moreover, the opening directions of the first storage chamber 11 and the second storage chamber 12 are consistent with the up-down direction. The first storage chamber 11 and the second storage chamber 12 are adjacent to each other.

[0030] The control board 21, the power board 22, the capacitor 23 and the IGBT 24 are stored in the first storage chamber 11. The first bus bar 31 is stored across the first storage chamber 11 and the second storage chamber 12. The second bus bar 32, the bus bar holder 33 and the cover opening detection device 60 are stored in the second storage chamber 12.

[0031] The housing 10 includes a first bottom wall 10a, a second bottom wall 10b, a side wall 10c, and a partition wall 10d. The storage space 13 is a space surrounded by the first bottom wall 10a, the second bottom wall 10b, and the side wall 10c.

[0032] The side wall portion 10c has a substantially rectangular ring shape when viewed in the up-down direction. The side wall portion 10c horizontally surrounds the storage space 13. The first cover 40 and the second cover 50 are fixed to the upper end surface 10ca of the side wall portion 10c.

[0033] The first bottom wall 10a and the second bottom wall 10b are located at the lower end of the side wall 10c. The first bottom wall 10a and the second bottom wall 10b are located at the lower side of the storage space 13. The first bottom wall 10a is located at the lower side of the first storage chamber 11. The second bottom wall 10b is located at the lower side of the second storage chamber 12.

[0034] The second bottom wall portion 10b is located above the first bottom wall portion 10a. Therefore, the dimension of the second storage chamber 12 in the up-down direction (the dimension along the opening direction) is smaller than the dimension of the first storage chamber 11 in the up-down direction. In addition, the volume of the second storage chamber 12 is smaller than the volume of the first storage chamber 11. The second storage chamber 12 mainly stores a part of the first bus bar 31 and the second bus bar 32. In the second storage chamber 12, the plate thickness direction of the first bus bar 31 and the second bus bar 32 is consistent with the up-down direction. According to the present embodiment, the dimension of the second storage chamber 12 in the up-down direction is made smaller than that of the first storage chamber 11, so that the inverter unit 1 as a whole can be miniaturized.

[0035] The partition wall portion 10 d divides the storage space 13 into a first storage chamber 11 and a second storage chamber 12 .

[0036] The partition wall portion 10d is provided with a partition wall opening 10da that allows the first storage chamber 11 and the second storage chamber 12 to communicate with each other. The first bus bar 31 passes through the partition wall opening 10da.

[0037] Figure 4 It is a bottom view of the housing 10 .

[0038] A plurality of (four in this embodiment) positioning recesses 19 are provided on the outer peripheral surface of the housing 10. In this embodiment, two positioning recesses 19 are provided in each of the first bottom wall 10a and the second bottom wall 10b.

[0039] The positioning recesses 19 are each open downward. The positioning recesses 19 are circular in a plan view. In the assembly process of the inverter unit 1, positioning pins provided in an assembly device (not shown) are inserted into the positioning recesses 19. Thus, the housing 10 and the assembly device are positioned relative to each other.

[0040] like Figure 2As shown, the control board 21 is located in the first storage chamber 11. The control board 21 is connected to the motor 2 to control the motor 2. For example, when the motor unit 3 has an encoder such as a resolver, the control board 21 feedback controls the rotation speed of the motor 2 according to the rotation speed of the motor 2 measured by the encoder.

[0041] The power substrate 22, the capacitor 23, and the IGBT 24 are located in the first storage chamber 11. The capacitor 23 and the IGBT 24 are connected to the power substrate 22, respectively. The power substrate 22, the capacitor 23, and the IGBT 24 constitute an inverter 25. The inverter 25 is connected to the external power supply device 9 via the first bus bar 31 and the second bus bar 32. The external power supply device 9 is, for example, a secondary battery mounted on a vehicle. The inverter 25 converts a DC current supplied from the external power supply device 9 into an AC current.

[0042] like Figure 3 As shown, in the inverter unit 1, a pair of first bus bars 31 and a pair of second bus bars 32 are provided. The first bus bars 31 and the second bus bars 32 are formed of conductive plates. The first bus bars 31 and the second bus bars 32 are connected to each other by fixing screws 30a. The pair of first bus bars 31 and the pair of second bus bars 32 constitute the wiring portion 30. That is, the inverter unit 1 has the wiring portion 30.

[0043] The wiring portion 30 is provided across the first storage chamber 11 and the second storage chamber 12. The wiring portion 30 connects the power substrate 22 and the external power supply device 9. That is, the wiring portion 30 connects the external power supply device 9 and the inverter 25. The wiring portion 30 is connected to the power cable 9a extending from the external power supply device 9. The wiring portion 30 supplies the DC current supplied from the external power supply device 9 via the power cable 9a to the inverter 25. The place where the wiring portion 30 is connected to the power cable 9a is located on the motor 2 side in the motor unit 3. With this structure, in the motor unit 3, even if a large impact is applied from the opposite side of the motor 2, the wiring portion 30 and the power cable 9a will not fall off.

[0044] According to the present embodiment, the wiring portion 30 is a plate-shaped bus bar. Generally speaking, compared with a flexible cable, a bus bar is easier to ensure insulation even under vibration. According to the present embodiment, by making the wiring portion 30 a plate-shaped bus bar, a large current can be stably supplied from the external power supply device 9 to the inverter 25.

[0045] The first bus bar 31 is provided across the first storage chamber 11 and the second storage chamber 12. One end of the first bus bar 31 is located in the first storage chamber 11 and connected to the power board 22. The other end of the first bus bar 31 is located in the second storage chamber 12 and connected to the second bus bar 32.

[0046] The second bus bar 32 is located in the second storage chamber 12. The plate thickness direction of the second bus bar 32 is consistent with the vertical direction over the entire length. That is, the plate thickness direction of the second bus bar 32 is consistent with the opening direction of the second storage chamber. When viewed in the vertical direction, the second bus bar 32 extends roughly in an L shape. The second bus bar 32 is supported by the bus bar holder 33. The second bus bar 32 is fixed to the housing 10 via the bus bar holder 33.

[0047] One end of the second bus bar 32 is connected to the first bus bar 31. In addition, a connection portion 32a connected to the external power supply device 9 is provided at the other end of the second bus bar 32. That is, the wiring portion 30 has the connection portion 32a located in the second storage chamber 12.

[0048] In the connecting portion 32a, the plate thickness direction of the second bus bar 32 is consistent with the opening direction of the second storage chamber 12. The connecting portion 32a is provided with a through hole 32c that penetrates along the plate thickness direction of the second bus bar 32. On the other hand, a connecting terminal 9b is provided at the front end of the power cable 9a extending from the external power supply device 9. The connecting terminal 9b is provided with a through hole (omitted from the figure) that overlaps with the through hole 32c. The through hole 32c of the connecting portion 32a and the through hole of the connecting terminal are inserted and threadedly fastened by fixing screws 30b. Thus, the wiring portion 30 is connected to the external power supply device 9.

[0049] According to the present embodiment, the connection portion 32a is screwed and fastened with the connection terminal 9b of the external power supply device 9 in the through hole 32c extending in the opening direction of the second storage chamber 12. Therefore, the operator can screw and fasten the connection portion 32a and the connection terminal 9b of the external power supply device 9 from the opening direction of the second storage chamber 12. Therefore, the wiring portion 30 and the external power supply device 9 can be easily connected in a state where the opening of the second storage chamber 12 is open.

[0050] The cover-opening detection device 60 is located in the second storage chamber 12. The cover-opening detection device 60 has a switch portion 61 that contacts the second cover 50. When the second cover 50 is removed from the housing 10, the switch portion 61 is separated from the second cover 50. The cover-opening detection device 60 cuts off the current supplied from the external power supply device 9 when the second cover 50 is detached from the housing 10 and the switch portion 61 is detached from the second cover 50. In addition, the cover-opening detection device 60 releases the cutoff of the current supplied from the external power supply device 9 when the second cover 50 is mounted on the housing 10 and the switch portion 61 contacts the second cover 50.

[0051] According to the present embodiment, by providing the cover opening detection device 60, it is possible to suppress the current from flowing into the wiring portion 30 when the second storage chamber 12 is open. Therefore, in the connection process between the connection portion 32a of the wiring portion 30 and the connection terminal 9b of the external power supply device 9, the operator can be protected from the influence of the high voltage current and the connection process can be safely performed.

[0052] In the present embodiment, the cover opening detection device 60 is disposed inside the second storage chamber 12. However, the cover opening detection device 60 may be disposed outside the second storage chamber 12 as long as it detects the opening of the second cover 50.

[0053] like Figure 2 As shown, the first cover 40 covers the opening of the first storage chamber 11. The first cover 40 is plate-shaped. The first cover 40 is formed by stamping. The plate thickness direction of the first cover 40 is consistent with the opening direction of the first storage chamber 11 (in this embodiment, the up-down direction).

[0054] The first cover 40 has an upper surface (second surface) 40a and a lower surface (first surface) 40b. The lower surface 40b constitutes a part of the inner side surface of the first storage chamber 11. The lower surface 40b is in contact with the upper end surface 10ca of the housing 10. The upper surface 40a is a surface facing the opposite side of the lower surface 40b. The upper surface 40a is a surface facing the opening direction of the first storage chamber 11.

[0055] like Figure 1 As shown, the first cover 40 is fixed to the housing 10 by a plurality of fixing screws 18 at the peripheral portion. A plurality of through holes (not shown) penetrating the first cover 40 in the plate thickness direction are provided at the peripheral portion of the first cover 40. The fixing screws 18 are inserted into the through holes of the first cover 40 and screwed to the housing 10. Thus, the first cover 40 is fixed to the housing 10.

[0056] A plurality of positioning holes 49 are provided at the peripheral edge of the first cover 40. In the present embodiment, two positioning holes 49 are provided on the first cover 40. The positioning holes 49 penetrate the first cover 40 in the plate thickness direction. In the assembly process of the inverter unit 1, positioning pins provided in the assembly device (not shown) are inserted into the positioning holes 49. Thus, the first cover 40 and the assembly device are positioned relative to each other.

[0057] like Figure 2 As shown, the second cover 50 is plate-shaped. The second cover 50 is formed by stamping. The second cover 50 includes a cover body 51 , a protruding portion 52 , and a pressing portion 53 .

[0058] The cover body 51 is in the shape of a plate whose thickness direction coincides with the vertical direction. The thickness direction of the cover body 51 coincides with the opening direction (the vertical direction in this embodiment) of the second storage chamber 12. The cover body 51 covers the opening of the second storage chamber 12. That is, the second cover 50 covers the opening of the second storage chamber 12.

[0059] The cover body 51 has an upper surface 51a and a lower surface 51b. The lower surface 51b constitutes a part of the inner side surface of the second storage chamber 12. The lower surface 51b contacts the upper end surface 10ca of the housing 10. The upper surface 51a is a surface facing the opposite side of the lower surface 51b. The upper surface 51a is a surface facing the opening direction of the second storage chamber 12.

[0060] like Figure 1 As shown in FIG. 1 , the cover body 51 is fixed to the housing 10 by a plurality of fixing screws 18 at the peripheral portion. A plurality of through holes (not shown) penetrating the cover body 51 in the plate thickness direction are provided at the peripheral portion of the cover body 51. The fixing screws 18 are inserted into the through holes of the cover body 51 and are screwed to the housing 10. Thus, the second cover 50 is fixed to the housing 10. Figure 2 As shown, the first cover 40 and the second cover 50 are fixed to one continuous surface (upper end surface 10ca) of the housing 10.

[0061] like Figure 1 As shown, a plurality of positioning holes 59 are provided at the peripheral edge of the cover body 51. In the present embodiment, two positioning holes 59 are provided on the cover body 51. The positioning holes 59 penetrate the cover body 51 in the plate thickness direction. In the assembly process of the inverter unit 1, the positioning holes 59 are inserted by positioning pins provided in the assembly device (not shown). Thus, the second cover 50 and the assembly device are positioned relative to each other.

[0062] like Figure 2 As shown, the protrusion 52 protrudes from the outer edge of the cover body 51 to the opposite side (ie, the upper side) of the housing 10. In the present embodiment, the protrusion 52 is inclined toward the first cover 40 side as it goes upward.

[0063] The pressing portion 53 extends from the front end (ie, the upper end) of the protruding portion 52 toward the first cover 40. The pressing portion 53 covers at least a portion of the upper surface 40a of the first cover 40.

[0064] When performing the connection process of the connection portion 32a of the wiring portion 30 and the connection terminal 9b of the external power supply device 9, the operator opens the opening of the second storage chamber 12. In the inverter unit 1 of the present embodiment, a first cover 40 covering the opening of the first storage chamber 11 and a second cover 50 covering the opening of the second storage chamber 12 are provided. According to the present embodiment, the operator can perform the connection process in a state where the opening of the first storage chamber 11 is closed. Therefore, it is possible to prevent the control substrate 21 and the inverter 25 in the first storage chamber 11 from being contaminated by dust or the like during the connection process.

[0065] According to the present embodiment, the pressing portion 53 as a part of the second cover 50 covers a part of the upper surface 40a of the first cover 40. Therefore, in order to remove the first cover 40, it is necessary to remove the second cover 50 first. According to the present embodiment, it is possible to prevent the first cover 40 from being removed during the connection process. Therefore, it is possible to prevent the control substrate 21 and the inverter 25 in the first storage chamber 11 from being contaminated by dust or the like.

[0066] According to the present embodiment, the cover opening detection device 60 detects the opening of the second storage chamber 12 and cuts off the current flowing into the wiring portion 30. A portion of the second cover 50 covering the opening of the second storage chamber 12 covers a portion of the first cover 40. Therefore, when the opening of the first storage chamber 11 is opened, the opening of the second storage chamber 12 is also opened. According to the present embodiment, even when the opening of the first storage chamber 11 is opened, the operator can be protected from the high voltage current.

[0067] (Vibration suppression structure)

[0068] In the inverter unit 1 of the present embodiment, the housing 10 is as shown in FIG. Figure 1 As shown, it is covered by a cover having a protrusion 160.

[0069] Therefore, if Figure 1 As shown, the inverter unit 1 of this embodiment includes a housing 10 having a storage chamber opened to the outside and a cover fixed to the housing 10 and covering the opening of the storage chamber. The cover has a convex portion 160 protruding toward the side opposite to the housing 10 side.

[0070] In addition, the convex portion 160 has a space 100 that is open toward the housing 10 side.

[0071] This structure can improve the rigidity of the cover, thereby reducing vibration. In addition, since the convex portion has the space 100, vibration can be reduced without increasing weight.

[0072] The convex portion 160 has an upper surface 40a and a plurality of wall portions 120 along the outer circumference of the housing 10 at a position inner than the outer end 110 of the cover. The upper surface 40a has a groove portion 150 that is perpendicular to the one end side wall portion 130 and connected to the other end side wall portion 140 and is recessed toward the housing 10 side.

[0073] This structure can further improve the rigidity of the cover, thereby reducing vibration. In addition, since the convex portion has the space 100, vibration can be reduced without increasing weight.

[0074] The groove portion 150 includes a groove portion 150 extending parallel to the other end side wall portion 140 and a groove portion 150 extending obliquely with respect to the other end side wall portion 140 .

[0075] This structure can further improve the rigidity of the cover, thereby reducing vibration. In addition, since the convex portion has the space 100, vibration can be reduced without increasing weight.

[0076] The depth h1 of the groove portion 150 is smaller than the height h2 of the convex portion 160 .

[0077] With this configuration, the cover 10 for reducing vibration is realized in consideration of the arrangement and height of the components mounted on the control substrate 21 .

[0078] Various embodiments of the present invention have been described above, but each structure and combination thereof in each embodiment are examples, and addition, omission, substitution and other changes of structures can be made within the scope not departing from the gist of the present invention. In addition, the present invention is not limited to the embodiments.

[0079] Description of symbols

[0080] 1: inverter unit; 2: motor; 3: motor unit; 9: external power supply device; 9b: connecting terminal; 10: housing; 11: first storage chamber; 12: second storage chamber; 21: control substrate (second circuit board); 22: power substrate (first circuit board); 25: inverter; 30: wiring portion; 32a: connecting portion; 32c: through hole; 40: first cover; 50: second cover; 51: cover body; 52: protrusion; 53: pressing portion; 60: cover opening detection device; 100: space; 110: outer end; 120: multiple wall portions; 130: one end side wall portion; 140: the other end side wall portion; 150: groove portion; 160: convex portion.

Claims

1. An inverter unit that converts direct current into alternating current and supplies it to a motor, wherein: The inverter unit has: A housing having a first storage chamber and a second storage chamber open to the outside; A first circuit board, which is located in the first receiving chamber; a wiring portion connecting the first circuit board and an external power supply device; a first cover fixed to the housing and covering an opening of the first receiving chamber; as well as a second cover fixed to the housing and covering the opening of the second storage chamber, The wiring portion has a connection portion connected to an external power supply device, The connecting portion is located in the second storage chamber, When performing the connecting step of connecting the connecting portion of the wiring portion and the external power supply device, the connecting step can be performed in a state where the second cover is opened to open the opening of the second storage chamber and the opening of the first storage chamber is closed by the first cover.

2. The inverter unit according to claim 1, wherein: The first cover has: A first surface constituting a portion of an inner side surface of the first receiving chamber; and a second surface, which faces the opposite side of the first surface, A portion of the second cover has a pressing portion that covers at least a portion of the second surface of the first cover.

3. The inverter unit according to claim 2, wherein: The first storage chamber and the second storage chamber open in the same direction. The second cover has: a cover body portion, which is plate-shaped and covers the opening of the second storage chamber; a protrusion that protrudes from an outer edge of the cover body toward a side opposite to the housing; as well as The pressing portion extends from a front end of the protruding portion toward the first cover.

4. The inverter unit according to any one of claims 1 to 3, wherein: The inverter unit has a cover opening detection device. The cover opening detection device cuts off the current provided by the external power supply device when the second cover is separated from the housing, and releases the cut-off of the current provided by the external power supply device when the second cover is installed on the housing.

5. The inverter unit according to any one of claims 1 to 3, wherein: The inverter unit has a second circuit board located in the first storage chamber. The second circuit board is a control substrate for controlling the motor.

6. The inverter unit according to any one of claims 1 to 3, wherein: The wiring portion is a plate-shaped bus bar.

7. The inverter unit according to claim 6, wherein: In the connection portion, the plate thickness direction of the wiring portion is consistent with the opening direction of the second storage chamber, The connecting portion is provided with a through hole penetrating in the plate thickness direction. The connection portion is threadedly fastened to the connection terminal of the external power supply device in the through hole.

8. The inverter unit according to any one of claims 1 to 3, wherein: The volume of the second storage chamber is smaller than the volume of the first storage chamber.

9. The inverter unit according to any one of claims 1 to 3, wherein: The first storage chamber and the second storage chamber open in the same direction. A dimension of the second storage chamber along the opening direction is smaller than a dimension of the first storage chamber along the opening direction.

10. A motor unit comprising: The inverter unit according to any one of claims 1 to 9; and The motor is provided with an alternating current by the inverter unit.

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