Motor unit

Abstract

This motor unit 1 comprises: an electric motor 2; a substrate 3 provided with a control unit C for the electric motor 2; a metal housing 5 accommodating the electric motor 2 and the substrate 3; and a bus bar holder 42 insulating and holding a plurality of bus bars 41 between the substrate 3 and the electric motor 2 in an axial direction. A terminal 41a provided at one end of each bus bar 41 is inserted into a corresponding terminal insertion hole 31 provided on the substrate 3 to electrically connect a coil 26 of a stator 23 and the control unit C. The housing 5 is arranged between the bus bar holder 42 and the substrate 3 in the axial direction, and has a motor cover 54 for sealing one end opening of a motor housing part 51 accommodating the electric motor 2. The terminal 41a and the substrate 3 are positioned by the motor cover 54.

Description

Motor Unit

[0001] The present invention relates to a motor unit.

[0002] For example, Patent Document 1 below describes an electric pump for a vehicle that includes a motor unit and a pump unit driven by the output of the motor unit. The motor unit includes an electric motor consisting of a three-phase motor, a circuit board on which a control unit for controlling the operation of the electric motor is mounted, and a housing that accommodates the electric motor and the circuit board. Coils (U-phase, V-phase, and W-phase coils) mounted on the stator of the electric motor are electrically connected to the circuit board (and the control unit mounted on the circuit board) by inserting terminals of pin-shaped coil wires extending axially into holes formed in the circuit board. In other words, in the motor unit of Patent Document 1, the coil wires that constitute the coils are directly connected to the circuit board without using a conductive component also known as a bus bar. With this configuration, the motor unit can be made more compact in the axial direction by eliminating the bus bar.

[0003] In the motor unit of Patent Document 1, in order to make it possible to easily connect the coil wire (or its terminal portion) to the circuit board even if the bus bar is omitted, a resin coil guide is provided between the electric motor and the circuit board in the axial direction, which guides the coil wire toward the hole in the circuit board and holds it in a predetermined position and posture.

[0004] Japanese Patent Application Laid-Open No. 2023-4062

[0005] Even if a coil guide such as the one described above is provided, it is not easy to automate the process of holding the coil wire in the coil guide, and it is thought that manual work is required. For this reason, the configuration of Patent Document 1 may complicate rather than simplify the (electrical) connection process between the coil and the board, and ultimately the assembly process of the motor unit.

[0006] Furthermore, because the coil guide is a resin part, it is necessary to set larger dimensional tolerances for each part compared to metal parts of the same size and structure. As a result, the positioning of the end of the coil wire held and guided by the coil guide is prone to variation, and there is a possibility that the end of the coil wire cannot be connected to the board (inserted into the hole in the board).

[0007] In view of the above circumstances, the main object of the present invention is to provide a motor unit that can be assembled easily and accurately, including the electrical connection between the coil wire of the stator coil and the substrate.

[0008] The present invention, which has been devised to achieve the above-mentioned object, is a motor unit comprising: an electric motor; a substrate arranged axially outside the electric motor and having a control unit for controlling the electric motor; a metal housing that houses the electric motor and the substrate; and a bus bar holder that insulates and holds a plurality of bus bars between the substrate and the electric motor in the axial direction, wherein a plurality of coils provided in a stator of the electric motor are electrically connected to the control unit by inserting terminals provided at one end of each bus bar into corresponding terminal insertion holes provided in the substrate, and the housing has a motor cover that is arranged axially between the bus bar holder and the substrate and closes one end opening of the motor accommodating section that accommodates the electric motor, and the terminals and the substrate are positioned by this motor cover.

[0009] According to the above configuration, when assembling the motor unit, first, by placing the motor cover axially outward of the bus bar holder to seal one end opening of the motor accommodating portion of the housing with the motor cover, the bus bar terminals can be positioned radially and circumferentially. Then, by placing the circuit board axially outward of the motor cover, the circuit board can be positioned (radially and circumferentially). Furthermore, because the motor cover itself, which is a component of the metal housing, is naturally made of metal, the dimensional tolerances of each part can be reduced compared to the resin coil guides used in conventional products. This allows for precise positioning of the bus bar terminals and the circuit board terminal insertion holes, simplifying and accurately assembling the motor unit, including inserting the pin terminals into the terminal insertion holes.

[0010] The positioning of the substrate (radial and circumferential positioning) using the motor cover can be performed, for example, by inserting an axial (axially extending) positioning pin provided on the motor cover into a corresponding pin insertion hole provided on the substrate.

[0011] Furthermore, the terminals can be positioned by the motor cover, for example, by fitting terminal holding portions provided on the bus bar holder into corresponding terminal insertion holes provided in the motor cover.

[0012] The motor cover may have a cylindrical bearing mounting surface on which a support bearing for the output shaft of the electric motor is mounted.

[0013] The housing may be arranged axially outward of the substrate and may have a cover member that closes one end opening of a substrate accommodating portion that accommodates the substrate.

[0014] The motor unit according to the present invention described above can be combined with a pump unit that receives the output of this motor unit (the electric motor that constitutes it) to generate hydraulic pressure, to form an electric oil pump, for example.

[0015] As described above, according to the motor unit of the present invention, assembly of the motor unit, including the electrical connection between the coil wire of the stator coil and the circuit board, can be carried out easily and accurately.

[0016] Fig. 1 is a longitudinal sectional view of a motor unit according to one embodiment of the present invention; Fig. 2 is a sectional view of the motor unit taken along line AA of Fig. 1; Fig. 3 is a perspective view of a stator unit; Fig. 4 is an exploded perspective view of the motor unit; Fig. 5 is a plan view of a motor cover according to a modified example; Fig. 6 is a longitudinal sectional view of a motor unit according to another embodiment of the present invention;

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] FIG. 1 is a longitudinal cross-sectional view of a motor unit 1 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, FIG. 3 is a perspective view of a stator unit constituting an electric motor, and FIG. 4 is an exploded perspective view of the motor unit 1 shown in FIG. 1. The circuit board 3 shown in FIG. 1 is omitted from FIG. 4. The motor unit 1 shown in FIG. 1 constitutes a part of an electric pump (electric oil pump) that is mounted on a vehicle such as an automobile and generates hydraulic pressure in the transmission while the engine is stopped. In other words, an electric pump is constituted by combining the motor unit 1 with a pump unit (not shown) that is driven by the output of the motor unit 1 (rotation of the output shaft 22 of the electric motor 2). For example, a pump rotor (inner rotor) is attached to the portion of the output shaft 22 of the electric motor 2 that protrudes outside the housing 5.

[0019] The motor unit 1 shown in FIG. 1 and other figures includes an electric motor 2, a substrate 3 that is disposed axially outward of the electric motor 2 and that includes a controller C that controls the operation of the electric motor 2, a busbar unit 4, and a housing 5 that accommodates the electric motor 2, the substrate 3, and the busbar unit 4. In the following description, the terms "axial direction," "radial direction," and "circumferential direction" refer to a direction parallel to an axis O of the output shaft 22 of the electric motor 2, a radial direction of a circle centered on the axis O, and a circumferential direction, respectively. The left and right sides of the paper in FIG. 1 are also referred to as one axial side and the other axial side, respectively. The "axially outward side of the electric motor 2" refers to a region on one axial side of one axial end of the electric motor 2 and a region on the other axial side of the other axial end of the electric motor 2.

[0020] The electric motor 2 is a radial gap type three-phase motor (three-phase brushless motor) that includes a rotor 21 and a cylindrical stator 23 that is disposed radially outwardly of and spaced from the rotor 21. Therefore, the stator 23 has coils 26 that correspond to the U-phase, V-phase, and W-phase.

[0021] The rotor 21 has an output shaft 22 of the electric motor 2, which is rotatably supported in the housing 5 via two bearings (a first rolling bearing 22A and a second rolling bearing 22B) spaced apart in the axial direction. One and other axial ends of the output shaft 22 protrude axially outward from the stator 23, with the inner ring of the first rolling bearing 22A attached to the protruding portion on one axial side and the inner ring of the second rolling bearing 22B attached to the protruding portion on the other axial side. The outer rings of both rolling bearings 22A, 22B are attached to the motor cover 54 and the motor accommodating portion 51 of the housing 5, respectively. Deep groove ball bearings, for example, are used as the rolling bearings 22A, 22B.

[0022] The motor unit 1 of this embodiment is provided with a detection unit 7 for detecting the rotation angle of the rotor 21 (output shaft 22). The detection unit 7 includes a sensor magnet 7A attached to one axial end of the output shaft 22 via a bracket, and a rotation sensor 7B arranged axially opposite the sensor magnet 7A. The rotation sensor 7B is provided on a substrate 3 arranged on one axial side of the electric motor 2.

[0023] The rotation sensor 7B is electrically connected to a control unit C provided on the circuit board 3, and the value detected by the rotation sensor 7B is input to the control unit C. As a result, the value detected by the rotation sensor 7B is used to control the operation of the electric motor 2. Note that this detection unit 7 is not necessarily provided and may be omitted in some cases. In other words, the motor unit 1 may be used in a sensorless state without the detection unit 7 (rotation sensor 7B).

[0024] As shown in Figures 3 and 4, in the motor unit 1 of this embodiment, the stator 23 is accommodated and fixed to the inner periphery of the housing 5 (the motor accommodating portion 51) in the form of an assembly (stator assembly) in which the annular bus bar unit 4 is attached to one axial end of the stator 23.

[0025] The stator 23 includes a starter core 24 having a plurality of (here, a total of 12) teeth 24a spaced apart in the circumferential direction, and a plurality of (here, a total of 12) coils 26 formed by winding coil wire 25 around the outer periphery of each tooth 24a via an insulating member such as an insulator. As described above, the coils 26 include U-phase, V-phase, and W-phase coils, and in this embodiment, where a total of 12 coils 26 are provided, four coils for each phase are provided. In the illustrated example, each coil 26 is formed by so-called concentrated winding.

[0026] The busbar unit 4 includes a plurality of busbars 41 formed of a metal material with high electrical conductivity such as copper, and a busbar holder 42 formed of an insulating material such as resin, which insulates and holds the plurality of busbars 41 in a non-contact state.

[0027] At least three bus bars 41 are provided: a U-phase bus bar electrically connected to an end portion of the coil wire 25 that constitutes the U-phase coil 26, a V-phase bus bar connected to an end portion of the coil wire 25 that constitutes the V-phase coil 26, and a W-phase bus bar connected to an end portion of the coil wire 25 that constitutes the W-phase coil 26. If the coils 26 are delta-connected, one bus bar 41 is provided for each phase, and if the coils 26 are star-connected, a neutral bus bar is provided in addition to the bus bars 41 for each phase. One longitudinal end of each of the U-, V-, and W-phase bus bars 41 is provided with a pin-shaped terminal 41a extending in the axial direction, and the other longitudinal end of each bus bar 41 is electrically connected to (the end portion of the coil wire 25 that constitutes) the coil 26 of the corresponding phase.

[0028] The busbar holder 42 includes an annular portion 43 arranged coaxially with the stator core 24 on one axial side of the stator core 24, and a cylindrical terminal holding portion 44 that holds the terminals 41 a of each busbar 41 without contacting the motor cover 54 of the housing 5. The annular portion 43 and the terminal holding portion 44 are integrally or separately formed of an insulating material such as resin. The terminal holding portion 44 may have a shape other than cylindrical, such as a rectangular shape. The busbar holder 42 is provided with a plurality of circumferentially spaced jumper wire holding portions 45 that hold the jumper wires 25 a connecting the coils 26 (by which the jumper wires 25 a are entangled). The busbar holder 42 having such a configuration can be obtained, for example, by injection molding the annular portion 43 (and the terminal holding portions 44) with resin, using the busbars 41 and the jumper wire holding portions 45 as insert parts. The bus bar holder 42 is attached to the stator core 24 by any suitable means that allows a predetermined amount of relative movement in the axial, radial and circumferential directions with respect to the stator 23 (stator core 24).

[0029] The substrate 3 is a rectangular plate-like member with a mounting surface 3a on which electronic components (not shown) are mounted, arranged along the radial direction, and is secured to the housing 5 while housed in a substrate housing portion 52 of the housing 5 by screws (screws are not shown). Examples of electronic components mounted on the mounting surface 3a include capacitors such as electrolytic capacitors, inductors, semiconductor elements (switching elements) such as MOSFETs, integrated circuits such as driver ICs, and resistors. These electronic components are electrically connected to form a control unit C that controls the operation of the electric motor 2.

[0030] The substrate 3 of this embodiment has pin insertion holes 31 and terminal insertion holes 32 formed on both its front and back surfaces (the mounting surface 3a and the surface opposite thereto). The pin insertion holes 31 are holes into which positioning pins 54a provided on the motor cover 54 are inserted, and in this embodiment, two pin insertion holes 31 are provided spaced apart in a manner corresponding to the radial and circumferential positions of the positioning pins 54a. The terminal insertion holes 32 are holes into which (the tip portions of) the terminals 41a of the bus bars 41 are inserted, and three terminal insertion holes 32 are provided spaced apart in a manner corresponding to the radial and circumferential positions of the terminals 41a of the bus bars 41 for the U, V, and W phases.

[0031] The housing 5 includes a cylindrical motor housing portion 51 that houses the electric motor 2 and the busbar unit 4, and a rectangular tubular board housing portion 52 that houses the board 3. Since the board housing portion 52 is located radially outward of the motor housing portion 51, a connecting portion 53 that extends radially to connect the two housing portions 51, 52 is formed into a rectangular shape in a plan view (see FIG. 2). The two housing portions 51, 52 and the connecting portion 53 are integrally formed using a metal material that has good electrical and thermal conductivity and is easy to process. An example of a metal material having such properties is an aluminum alloy.

[0032] The housing 5 further has a motor cover 54 that is interposed axially between the bus bar unit 4 attached to the electric motor 2 and the circuit board 3 and seals one opening of the motor accommodating portion 51. This motor cover 54 is also made of the same metal material as the accommodating portions 51, 52 and the connecting portion 53. The connecting portion 53 has a recessed cover fitting portion 53a formed on its inner periphery into which the motor cover 54 is fitted, and the motor cover 54 is fitted into the cover fitting portion 53a and then screwed to the connecting portion 53.

[0033] As shown in Figure 2, the motor cover 54 of this embodiment is provided with two positioning pins 54a that protrude axially to one side and are spaced apart in the circumferential direction. When the board 3 is assembled to the housing 5 (see Figure 1), each positioning pin 54a is inserted into a corresponding pin insertion hole 31 provided in the board 3. This positions the board 3 in the radial and circumferential directions relative to the motor cover 54 (and the housing 5 of which the motor cover 54 is a component).

[0034] The motor cover 54 is also provided with three terminal insertion holes 54b, each consisting of an axial through-hole, spaced apart in the circumferential direction, and one of the terminals 41a of the three bus bars 41 is inserted into each of the terminal insertion holes 54b. A resin terminal holder 44 that holds the terminal 41a of the bus bar 41 is fitted into each terminal insertion hole 54b. This ensures insulation of the bus bar 41 from the metal housing 5 (motor cover 54). The terminal holder 44 is fitted into each terminal insertion hole 54b with a clearance fit, taking into account fitability (assembly of the motor unit 1). The term "clearance fit" used here conforms to the definition of "clearance fit" specified in JIS B 0401-2.

[0035] As described above, the motor unit 1 of this embodiment constitutes part of the electric oil pump, and oil is present in the internal space of the motor accommodating portion 51, to which the pump unit is disposed adjacently on the other axial side, within the internal space of the housing 5. If this oil flows into the internal space of the board accommodating portion 52 and adheres to the board 3 (electronic components mounted thereon), there is a risk that the control unit C will not operate normally.

[0036] Therefore, an annular elastic member (O-ring 55) functioning as an oil seal is interposed in an elastically compressed and deformed state between the inner peripheral wall surface of the cover fitting portion 53a of the housing 5 and the opposing outer peripheral wall surface of the motor cover 54. Furthermore, an annular elastic member (O-ring 56) functioning as an oil seal is interposed in an elastically compressed and deformed state between the inner peripheral wall surfaces of the three terminal insertion holes 54b provided in the motor cover 54 and the opposing outer peripheral wall surface of the terminal holder 44. In addition, the motor cover 54 of this embodiment has an axial center hole on its inner periphery where one end of the output shaft 22 (and the sensor magnet 7A) is disposed. One end opening of this center hole is closed by a concave-shaped cover member fitted to the inner periphery of the center hole. This configuration minimizes oil intrusion into the internal space of the board accommodating portion 52.

[0037] The motor unit 1 having the above configuration is assembled generally through the following steps (1) to (4) (see also FIG. 4 ): (1) An assembly (stator assembly) of the stator core 24 (stator 23) and the busbar unit 4 is inserted into the motor accommodating portion 51 of the housing 5, and the stator 23 is fixed to the inner circumferential surface of the motor accommodating portion 51. (2) An assembly (rotor assembly) formed by mounting a rolling bearing 22A on the outer periphery of the output shaft 22 constituting the rotor 21 is placed radially inside the stator 23, and is mounted on the inner periphery of the other end of the motor accommodating portion 51, which also mounts a second rolling bearing 22B. (3) After mounting O-rings 55 and 56 on the motor cover 54, the motor cover 54 is fitted into the cover fitting portion 53a provided on the housing 5, and the motor cover 54 is screwed to the connecting portion 53. When fitting the motor cover 54 into the cover fitting portion 53a, the terminals 41a of the bus bars 41 corresponding to the terminal insertion holes 54b provided in the motor cover 54 are inserted through the terminal insertion holes 54b (the terminal holding portions 44 holding the terminals 41a of the corresponding bus bars 41 are fitted), and each terminal 41a is positioned radially and circumferentially. (4) The board 3 is placed on the inner periphery of the board accommodating portion 52 of the housing 5 and then screwed to the housing 5. When placing the board 3 on the inner periphery of the board accommodating portion 52, the positioning pins 54a provided on the motor cover 54 are inserted into the pin insertion holes 31, and the terminals 41a of the bus bars 41 are inserted into the terminal insertion holes 32. At this time, it is preferable that insertion of the positioning pins 54a into the pin insertion holes 31 begins before insertion of the terminals 41a into the terminal insertion holes 32 begins.

[0038] In the motor unit 1 of the present embodiment described above, the metal housing 5 that accommodates the electric motor 2 and the circuit board 3 is provided with a motor cover 54 that seals one end opening of the motor accommodating portion 51 between the bus bar holder 42 and the circuit board 3 in the axial direction, and the terminals 41 a of each bus bar 41 and the circuit board 3 are positioned (radially and circumferentially) by this motor cover 54. Specifically, the motor cover 54, which is disposed axially outside the bus bar holder 43, is moved relatively closer to the bus bar holder 43, and the terminals 41 a of the bus bars 41 are inserted into the terminal insertion holes 54 b formed in the motor cover 54 (the terminal holding portions 44 that hold the terminals 41 a are fitted), thereby positioning the terminals 41 a in the radial and circumferential directions. Subsequently, the circuit board 3, which is disposed axially outside the motor cover 54, is moved relatively closer to the motor cover 54, and the positioning pins 54 a formed in the motor cover 54 are inserted into the pin insertion holes 31 of the circuit board 3, thereby positioning the circuit board 3 in the radial and circumferential directions.

[0039] Furthermore, because the motor cover 54, which is a component of the metal housing 5, is itself made of metal, the dimensional tolerances of each part can be set smaller than those of the resin coil guides used in conventional motor units. This allows the terminals 41a of each bus bar 41 to be accurately positioned in the radial and circumferential directions with the corresponding terminal insertion holes 32 provided in the circuit board 3. This simplifies and accurately assembles the motor unit 1, including inserting the terminals 41a into the terminal insertion holes 32 in the circuit board 3.

[0040] Furthermore, as described above, if the terminals 41 a of the busbar 41 are positioned radially and circumferentially by the motor cover 54 of the housing 5, the stator 23 (stator core 24), to which the busbar unit 4 is attached, will not be significantly involved in the positional accuracy of the terminals 41 a of the busbar 41, and therefore the fixing accuracy of the busbar unit 4 (busbar holder 42) relative to the stator 23 and the dimensional accuracy (dimensional tolerance) required of the stator core 24 can be relaxed.

[0041] Furthermore, the bus bar 41 has a larger cross-sectional area than a typical coil wire, allowing it to carry a large current, and has excellent heat dissipation properties. Therefore, the motor unit 1 of this embodiment, in which power is supplied to the coil 26 of the stator 23 via the bus bar 41, can easily accommodate increases in the output of the electric motor 2.

[0042] Although the motor unit 1 according to one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

[0043] 5 is a schematic plan view of a modified motor cover 54. In the motor cover 54 shown in the figure, of the three terminal insertion holes 54b provided at intervals in the circumferential direction, the diameters of the terminal insertion holes 54b (54b1) located in the center and the terminal holder 44 of the corresponding terminal 41a of the bus bar 41 are adjusted so that the minimum gap (the difference between the minimum allowable dimension of the terminal insertion hole and the maximum allowable dimension of the terminal holder 44) between the central terminal insertion hole 54b (54b1, 54b2) and the terminal holder 44 of the corresponding terminal 41a of the bus bar 41 is smaller than the minimum gap between the remaining two terminal insertion holes 54b (54b2) and the terminal holder 44 of the corresponding terminal 41a of the bus bar 41. Furthermore, the fit between the central terminal insertion hole 54b1 and the corresponding terminal holding portion 44 may be a "transition fit (see JIS B 0401-2)," and the fit between the remaining two terminal insertion holes 54b2 and the corresponding terminal holding portions 44 may be a "loose fit." In this case, by fitting the terminal holding portion 44 corresponding to the central terminal insertion hole 54b (54b1), it is possible to position each terminal 41a in the radial and circumferential directions, thereby improving the ease of assembly of the motor unit 1.

[0044] In this case, the terminal holder 44 that holds the terminal 41a of the centrally located bus bar 41 is firmly fixed to the motor cover 54, so when the terminal 41a of the centrally located bus bar 41 is inserted into the terminal insertion hole 32 of the circuit board 3 (not shown), the circuit board 3 can be positioned radially and circumferentially with respect to the motor cover 54. For this reason, the positioning pins 54a of the motor cover 54 are omitted in this embodiment. Therefore, a circuit board 3 that does not have the pin insertion hole 31 can be used.

[0045] As shown in Fig. 6, the motor unit 1 of the embodiment described above can be provided with a metal cover member 57 that is disposed axially outward of the substrate 3 and seals one end opening of the substrate accommodating portion 52 that accommodates the substrate 3. In other words, the metal housing 5 can be provided with a cover member 57 that seals one end opening of the substrate accommodating portion 52. This makes it possible to realize a motor unit 1 with improved protection performance for the substrate 3.

[0046] The present invention is not limited to the above-described embodiment, and can be embodied in various other forms without departing from the spirit of the present invention.

[0047] REFERENCE SIGNS LIST 1 motor unit 2 electric motor 3 circuit board 4 bus bar unit 5 housing 21 rotor 22 output shaft 23 stator 25 coil wire 26 coil 31 pin insertion hole 32 terminal insertion hole 41 bus bar 41a terminal 42 bus bar holder 44 terminal holding portion 51 motor accommodating portion 52 circuit board accommodating portion 54 motor cover 57 lid member C control portion O shaft center

Claims

1. A motor unit comprising: an electric motor; a board arranged axially outside the electric motor and equipped with a control unit for controlling the electric motor; a metal housing accommodating the electric motor and the board; and a bus bar holder which insulates and holds a number of bus bars between the board and the electric motor in the axial direction, wherein a number of coils provided in a stator of the electric motor are electrically connected to the control unit by inserting terminals provided on one end of each bus bar into corresponding terminal insertion holes provided in the board, wherein the housing is arranged axially between the bus bar holder and the board and has a motor cover which seals an opening at one end of a motor housing section which accommodates the electric motor, and the terminals and the board are positioned by the motor cover.

2. The motor unit according to claim 1, wherein the terminals and the circuit board are positioned in the radial and circumferential directions by the motor cover.

3. A motor unit as described in claim 1, wherein the positioning of the board by the motor cover is achieved by inserting an axial positioning pin provided on the motor cover into a corresponding pin insertion hole provided on the board.

4. A motor unit as described in claim 1, wherein the positioning of the terminals by the motor cover is achieved by fitting a terminal holding portion provided on the bus bar holder into a corresponding terminal insertion hole provided in the motor cover.

5. A motor unit according to claim 1, wherein said motor cover has a cylindrical bearing mounting surface on which a support bearing for an output shaft of said electric motor is mounted.

6. A motor unit according to claim 1, wherein the housing has a cover member disposed axially outside the board and sealing one end opening of a board accommodating portion that accommodates the board.

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