Rotor and axial gap motor

Abstract

To provide a rotor that can achieve cost reduction, weight reduction, and miniaturization while ensuring mechanical strength. [Solution] The rotor 1 for the axial gap motor 100 comprises a forged rotor core 2 facing the stator 6 in the axial direction Z via a gap G, and a shaft 3 coaxial with the forged rotor core 2. The forged rotor core 2 is preferably provided with a magnet 4 on the side facing the stator 6. The shaft 3 is preferably made of a non-magnetic material at least in part.

Description

Technical Field

[0001] The present invention relates to a rotor for a motor, and an axial gap motor provided with the rotor.

Background Art

[0002] In response to demands for weight reduction and size reduction of motors, axial gap motors have been attracting attention as alternatives to conventional radial gap motors. For example, Patent Document 1 discloses an axial gap motor including a rotor core configured using a dust core.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a dust core is molded, there is a limit on its size, so the rotor core needs to be, for example, a split core. In Patent Document 1, a mechanism for holding the split core is provided to resist centrifugal force during motor rotation. However, providing such a holding mechanism complicates the structure for ensuring mechanical strength, which leads to an increase in manufacturing cost, and makes it impossible to achieve weight reduction and size reduction of the motor. In addition, the material cost of the dust core itself is also high.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotor that can achieve cost reduction, weight reduction, and size reduction while ensuring mechanical strength, and an axial gap motor including the rotor.

Means for Solving the Problems

[0006] A characteristic configuration of the rotor according to the present invention for solving the above problems is as follows: A rotor for a motor, A forged rotor core that faces the stator in the axial direction with a gap between them, The system comprises a forged rotor core and a shaft that is coaxial with it.

[0007] With this rotor configuration, a forged rotor core is used, ensuring mechanical strength. Furthermore, by using a forged rotor core, complex holding mechanisms to ensure mechanical strength are unnecessary, thus reducing manufacturing costs and enabling lighter and smaller motors. Moreover, by manufacturing the rotor core using forging technology, the metal flow (forging lines) can be aligned with the shape of the rotor core, allowing even a smaller and lighter rotor core to possess mechanical strength. Therefore, by using a forged rotor core, it is possible to provide a rotor that achieves cost reduction, weight reduction, and miniaturization while ensuring mechanical strength.

[0008] In the rotor according to the present invention, The forged rotor core preferably has magnets on the side facing the stator.

[0009] With this rotor configuration, the magnets are located on the side facing the stator, which improves the rotational efficiency of the motor.

[0010] In the rotor according to the present invention, The forged rotor core preferably has an uneven surface on the side facing the stator.

[0011] With this rotor configuration, since only the side facing the stator needs to have protrusions and indentations, no other components are required, further cost reductions can be achieved.

[0012] In the rotor according to the present invention, The forged rotor core preferably comprises a laminate formed by stacking multiple plates made of magnetic material in the axial direction on the side facing the stator.

[0013] This rotor configuration, by incorporating plates made of magnetic material, can strengthen the magnetic field from the stator, thereby improving the rotational efficiency of the motor. Furthermore, since the magnetic flux from the stator flows in the circumferential direction of the forged rotor core within the plates, stacking the plates in the axial direction can suppress the generation of eddy currents.

[0014] In the rotor according to the present invention, Preferably, at least a portion of the shaft is made of a non-magnetic material.

[0015] With this rotor configuration, at least a portion of the shaft is made of a non-magnetic material, which suppresses leakage of magnetic flux generated in the stator through the shaft, thereby improving the rotational efficiency of the motor.

[0016] In the rotor according to the present invention, It comprises a second rotor core that is paired with the aforementioned forged rotor core, Preferably, the forged rotor core and the second rotor core are arranged to face each other via the stator.

[0017] With this rotor configuration, by adding a second rotor core in addition to the forged rotor core, the two rotor cores rotate in cooperation, which increases the motor's output torque.

[0018] In the rotor according to the present invention, Each of the forged rotor core and the second rotor core is provided with a plurality of magnets arranged circumferentially on the side facing the stator, It is preferable that the plurality of magnets are arranged such that the polarity of the magnets arranged in the forged rotor core and the polarity of the magnets arranged in the second rotor core are opposite to each other.

[0019] According to the rotor of this configuration, when a plurality of magnets are arranged such that the polarity of the magnets disposed in the forged rotor core and the polarity of the magnets disposed in the second rotor core are opposite to each other, the magnetic field can be strengthened by combining the magnetic field generated in the stator core and the magnetic field by the magnets, so that the rotation efficiency of the motor can be further improved.

[0020] Next, the characteristic configuration of the axial gap motor according to the present invention for solving the above problems is as follows: The motor includes the rotor described above, and a stator disposed coaxially with the forged rotor core, The stator has a plurality of stator cores arranged in the circumferential direction, Each of the stator cores is configured by laminating a plurality of magnetic plates in the radial direction.

[0021] According to the axial gap motor of this configuration, since the forged rotor core is used as the rotor core, the mechanical strength as the axial gap motor can be ensured. In addition, since the stator core is formed by laminating a plurality of magnetic plates, the configuration of the stator core is relatively simple, and manufacturing costs can be reduced. Furthermore, since the stator core is formed by laminating a plurality of magnetic plates in the radial direction, iron loss occurring at the boundaries of the plates can be suppressed, and rotation efficiency can be improved.

[0022] In the axial gap motor according to the present invention, It is preferable that the width of the plate when viewed in the axial direction is configured to increase continuously or stepwise as the distance from the axial center in the lamination direction increases.

[0023] In this axial gap motor configuration, the stator core can be made to have a shape close to a fan-shaped column by configuring it so that the width in the axial direction increases continuously or stepwise as it moves away from the axis in the stacking direction. This makes it easier to synchronize the rotational magnetic field generated by the stator with the rotation of the rotor. Therefore, it is possible to improve rotational efficiency while suppressing the manufacturing cost of the axial gap motor.

[0024] In the axial gap motor according to the present invention, The stator preferably includes a pair of fixing plates that secure the plurality of stator cores by sandwiching them from both sides in the axial direction.

[0025] This axial gap motor configuration allows for stable fixing of the stator core. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a schematic diagram illustrating the structure of an axial gap motor according to an embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram illustrating the structure of the stator of the axial gap motor shown in Figure 1. [Modes for carrying out the invention]

[0027] The present invention will be described below with reference to the drawings. In the following embodiments, the present invention will be described using as an example a rotor for an axial gap motor and an axial gap motor to which the present invention is applied. However, the present invention is not intended to be limited to the embodiments and configurations described below or shown in the drawings. Hereinafter, in this specification, when a rotating body (rotor 1, described later) rotates about a virtual centerline, that virtual centerline will be referred to as axis AL, and the direction in which axis AL extends will be referred to as the "axial direction (Z direction)". Furthermore, the direction perpendicular to the axial direction will be referred to as the "radial direction (R direction)", and within the radial direction, the direction away from axis AL will be referred to as the "R1 direction", and the direction toward axis AL will be referred to as the "R2 direction".

[0028] <Outline configuration of an axial gap motor> Figure 1 is a schematic diagram illustrating the structure of an axial gap motor 100 according to an embodiment of the present invention, and is a side view showing the main part of the axial gap motor 100 at a longitudinal cross-sectional end face. Figure 1 also includes a partially crushed cross-section. As shown in Figure 1, the axial gap motor 100 comprises a rotor 1 having a forged rotor core 2 and a shaft 3, and a stator 6. The forged rotor core 2 faces the stator 6 in the axial direction via a gap G, and the axis AL of the shaft 3 coincides with the axis AL of the forged rotor core 2 (they are coaxial). Note that in Figure 1, the various components constituting the axial gap motor 100, including the forged rotor core 2, shaft 3, magnet 4 (described later), second rotor core 5 (described later), and stator 6, have been appropriately exaggerated or simplified for the sake of clarity and ease of explanation, and do not strictly reflect the relative sizes and arrangements of the various components in an actual axial gap motor 100. Furthermore, Figure 1 shows the stacked state of multiple plates 64 that constitute the stator core 61, which will be described later. However, the relationships between the number, width, length, and thickness of the plates 64 have been exaggerated or simplified as appropriate for the sake of ease of explanation and clarity of the figure, and do not strictly reflect the actual relative sizes (scale) of the number, width, length, and thickness of the plates 64 (the same applies to Figure 2).

[0029] As shown in Figure 1, the axial gap motor 100 is equipped with a magnet 4 (e.g., a permanent magnet) on the side of the forged rotor core 2 facing the stator 6. The axial gap motor 100 also includes a second rotor core 5 that is paired with the forged rotor core 2. Figure 1 illustrates a dual-rotor type axial gap motor using an SPM motor, which is a type of synchronous motor. However, the magnet 4 and the second rotor core 5 may be provided as needed. Therefore, the technical concept of the present invention is not limited to dual-rotor type SPM motors, but can also be applied to other types of axial gap motors, such as reluctance motors and single-rotor types.

[0030] <Rotor> The rotor 1 comprises a forged rotor core 2 that faces the stator 6 in the axial direction via a gap G, and a shaft 3 that is coaxial with the forged rotor core 2. That is, the forged rotor core 2 and the shaft 3 are coaxial and configured to rotate about the axis AL.

[0031] <Forged rotor core> The forged rotor core 2 is a rotor core manufactured by forging. The forged rotor core 2 can be manufactured, for example, through a hot forging process in which it is formed by hot forging of a metal material, and a machining process in which the hot forged metal material is machined. Alternatively, it may be formed by warm forging or cold forging instead of hot forging. As the material for the forged rotor core 2, soft magnetic materials (for example, iron, silicon steel, permalloy, etc.) can be used. By forming the forged rotor core 2 by forging, it is possible to reduce costs, weight, and size while ensuring mechanical strength. In other words, since the forged rotor core 2 is manufactured using a relatively inexpensive soft magnetic material and forging technology, which is a type of mold forming technology, it is possible to reduce manufacturing costs compared to, for example, manufacturing using a powdered magnetic core. When the rotor core is constructed using a powdered magnetic core, there are problems in terms of the holding mechanism for the segmented core and material costs, as described above. In contrast, a forged rotor core 2 manufactured by forging does not require complex holding mechanisms to ensure mechanical strength, thus reducing manufacturing costs without hindering the weight reduction and miniaturization of the rotor 1. Furthermore, by manufacturing the rotor core using forging technology, the metal flow (forging lines) can be aligned with the shape of the rotor core, so even a lightweight and compact rotor core can have sufficient mechanical strength to withstand centrifugal forces during motor rotation. Thus, by using a forged rotor core 2, it is possible to reduce costs, weight, and miniaturize the rotor 1 while ensuring its mechanical strength.

[0032] The forged rotor core 2 has a cylindrical portion 2a, an inclined protruding portion 2b, and an annular plate portion 2c. The cylindrical portion 2a is fitted onto the large-diameter shaft portion 31d of the first shaft portion 31, which will be described later. The annular plate portion 2c is positioned to face one side (left side in Figure 1) of the stator 6 in the axial direction, with the magnet 4 interposed between them. The inclined protruding portion 2b is formed to protrude radially outward toward one side (left side in Figure 1) in the axial direction, so as to integrally connect one end of the cylindrical portion 2a in the axial direction with the inner circumference of the annular plate portion 2c.

[0033] <Magnet> As described above, the forged rotor core 2 can also be equipped with magnets 4 on the side facing the stator 6. Permanent magnets such as ferrite magnets or rare earth magnets can be used as magnets 4. In other words, the axial gap motor 100 can be an SPM motor, which is a type of synchronous motor. By equipping the magnets 4 on the side facing the stator 6, the rotational efficiency of the axial gap motor 100 can be improved. Here, "rotational efficiency" is an indicator that shows to what extent the electrical energy input to the axial gap motor 100 is used as mechanical energy (rotational force) of the axial gap motor 100, and can be defined, for example, by the ratio of the output power to the input power of the axial gap motor 100. In the axial gap motor 100, a rotating magnetic field is generated by passing a three-phase AC voltage through the electromagnetic coil of the stator core 61 of the stator 6, and the interaction between this rotating magnetic field and the magnets 4 makes it possible to rotate the forged rotor core 2 efficiently.

[0034] Preferably, multiple magnets 4 are arranged circumferentially on the stator 6 side of the forged rotor core 2 with alternating polarities. This allows the forged rotor core 2 to rotate in synchronization with the movement of the rotating magnetic field (achieving a synchronous motor), thereby further improving the rotational efficiency of the axial gap motor 100. Furthermore, since the magnets 4 are positioned opposite the stator core 61, a larger magnetic field can be generated in a smaller space. Consequently, the axial gap motor 100 can be miniaturized.

[0035] Furthermore, the configuration in which the magnet 4 is provided on the stator 6 side of the forged rotor core 2 is not particularly limited, but for example, it can be bonded to the surface of the forged rotor core 2 using an adhesive.

[0036] The surface of the forged rotor core 2 may have protrusions formed thereon to serve as positioning markers for the magnets 4. When the rotor core is manufactured by forging, the protrusions can be formed on the surface of the forged rotor core 2 by forming holes in the forging die that correspond to the shape of the positioning markers. If the rotor core is manufactured by machining, additional processing using an end mill or the like is required, but if the rotor is manufactured by forging, such additional processing is unnecessary. Therefore, positioning markers can be formed without significantly increasing manufacturing costs.

[0037] The surface of the forged rotor core 2 may be provided with a recess for fitting the magnet 4. In this case as well, it is sufficient to form the shape corresponding to the recess in the forging die, thus reducing additional processing. In addition, while adhesive strength generally tends to be stronger in the tensile direction (perpendicular to the adhesive surface) than in the shear direction (parallel to the adhesive surface), the structure of fitting the magnet 4 into the recess can also strengthen the fixing force in the shear direction.

[0038] Specifically, as shown in Figure 1, in the forged rotor core 2 of this embodiment, the multiple magnets 4 face one side (the left side in Figure 1) of the stator 6 (stator core 61, described later) in the axial direction via a gap G, and are arranged in the circumferential direction of the annular plate portion 2c such that the polarity of the side facing that side alternates. The multiple magnets 4 are fitted into recesses 2d provided in the annular plate portion 2c and fixed to the back surface of the recesses 2d via an adhesive layer (not shown).

[0039] <Second rotor core> As described above, the rotor 1 may also include a second rotor core 5. In this case, for example, as shown in Figure 1, the forged rotor core 2 and the second rotor core 5 are arranged to face each other via the stator 6. That is, Figure 1 illustrates a dual-rotor type axial gap motor 100, in which the second rotor core 5 faces the stator 6 in the axial direction via a gap and is configured to rotate about axis AL. By providing multiple rotor cores in this way, the two rotor cores rotate in cooperation, so that the rotor 1 can increase torque. The second rotor core 5 can be manufactured by forging, similar to the forged rotor core 2, but it may also be manufactured by methods other than forging.

[0040] As shown in Figure 1, the second rotor core 5 is equipped with magnets 4 on the side facing the stator 6. That is, each of the forged rotor core 2 and the second rotor core 5 is equipped with a plurality of magnets 4 arranged circumferentially on the side facing the stator 6. On the stator 6 side surface of the second rotor core 5, a plurality of magnets 4 are arranged circumferentially so that their polarities alternate. In this case, it is preferable that the number of magnets 4 arranged in the second rotor core 5 is the same as the number of magnets 4 arranged in the forged rotor core 2. For example, if eight magnets 4 are arranged in the forged rotor core 2, then eight magnets 4 are also arranged in the second rotor core 5. Furthermore, it is preferable to arrange the plurality of magnets 4 such that the polarity of the magnets 4 arranged in the forged rotor core 2 and the polarity of the magnets 4 arranged in the second rotor core 5 are opposite to each other. For example, when a magnet 4 with the stator 6 side facing north is arranged on the surface of a forged rotor core 2, it is preferable that the polarity of the magnet 4 of the second rotor core 5, which is arranged opposite to this magnet 4, be such that the stator 6 side faces south. By arranging the magnets 4 in this way, the direction of the magnetic paths of the multiple magnets 4 arranged on the forged rotor core 2 and the direction of the magnetic paths of the multiple magnets 4 arranged on the second rotor core 5 coincide. As a result, the magnetic field can be strengthened by combining the magnetic field from the stator 6 and the magnetic field from the magnets 4, thereby further improving the rotational efficiency of the axial gap motor 100.

[0041] As shown in Figure 1, the second rotor core 5 of this embodiment has a substantially symmetrical structure with the forged rotor core 2. The second rotor core 5, like the forged rotor core 2, has a cylindrical portion 5a, an inclined protruding portion 5b, and an annular plate portion 5c. The cylindrical portion 5a is fitted onto the large-diameter shaft portion 32c of the second shaft portion 32, which will be described later. The annular plate portion 5c is positioned to face the other side (right side in Figure 1) of the stator 6 in the axial direction, with the magnet 4 interposed between them. The inclined protruding portion 5b is formed to protrude radially outward toward the other side (right side in Figure 1) in the axial direction, so as to integrally connect the other end of the cylindrical portion 5a in the axial direction with the inner circumference of the annular plate portion 5c.

[0042] In the second rotor core 5 of this embodiment, the multiple magnets 4, similar to the forged rotor core 2, face the other side (right side in Figure 1) of the stator 6 (stator core 61, described later) in the axial direction via a gap G, and are arranged in the circumferential direction of the annular plate portion 5c such that the polarity of the side facing the other side alternates. The multiple magnets 4 are fitted into recesses 5d provided in the annular plate portion 5c and fixed to the back surface of the recesses 5d via an adhesive layer (not shown).

[0043] <Shaft> As shown in Figure 1, the shaft 3 has a first shaft portion 31 provided on the forged rotor core 2 side and a second shaft portion 32 provided on the second rotor core 5 side. The first shaft portion 31 and the second shaft portion 32 extend axially along the axis AL.

[0044] Preferably, at least a portion of the shaft 3 is made of a non-magnetic material. Here, "at least a portion" means, for example, that at least one of the first shaft portion 31 and the second shaft portion 32 is made of a non-magnetic material. Figure 1 illustrates a shaft 3 in which the second shaft portion 32 is made of a non-magnetic material. Ideally, the magnetic flux from the stator core 61 should return entirely to the stator core 61 side via the magnets 4 and the forged rotor core 2, and then back to the stator core 61 side via the adjacent magnet 4 with reversed polarity. However, if the shaft 3 is made of a magnetic material, some of the magnetic flux from the stator core 61 may leak from the forged rotor core 2 (annular plate portion 2c, inclined protruding portion 2b, and cylindrical portion 2a) through the shaft 3 to the second rotor core 5 (conversely, it may also leak from the second rotor core 5 through the shaft 3 to the forged rotor core 2). Such leaked magnetic flux reduces the magnitude of the magnetic field generated from the stator core 61. Therefore, by interposing a second shaft portion 32 (specifically, the flange portion 32d of the second shaft portion 32, described later) made of a non-magnetic material between the forged rotor core 2 and the second rotor core 5, the magnetic flux can be blocked in front of the second rotor core 5 (or forged rotor core 2), thereby suppressing leakage of magnetic flux to the second rotor core 5 (or forged rotor core 2). In this way, by making at least a part of the shaft 3 of a non-magnetic material, the rotational efficiency of the rotor 1 can be further improved.

[0045] In the configuration shown in Figure 1, instead of constructing the entire second shaft portion 32 from a non-magnetic material, the flange portion 32d and the (later described) large-diameter shaft portion 32c of the second shaft portion 32 may be made of a non-magnetic material, and the remaining portion of the second shaft portion 32 may be made of a magnetic material. With this configuration, it is possible to suppress the leakage of magnetic flux from the forged rotor core 2 from the cylindrical portion 2a of the forged rotor core 2 to the second rotor core 5 via the large-diameter shaft portion 31d and fitting projection 31e of the first shaft portion 31 and the large-diameter shaft portion 32c of the second shaft portion 32. Alternatively, at least the portion near the large-diameter shaft portion 32c of the flange portion 32d, the (later described) large-diameter shaft portion 32c, and the (later described) intermediate connecting shaft portion 32b of the second shaft portion 32 may be made of a non-magnetic material, and the remaining portion of the second shaft portion 32 may be made of a magnetic material. With this configuration, leakage of magnetic flux from the forged rotor core 2 from the cylindrical portion 2a of the forged rotor core 2 to the second rotor core 5 via the large-diameter shaft portion 31d and fitting projection 31e of the first shaft portion 31 and the large-diameter shaft portion 32c of the second shaft portion 32 can be further suppressed.

[0046] The forged rotor core 2 and shaft 3, and / or the second rotor core 5 and shaft 3, are connected by bolts (not shown), but it is preferable that the bolts are also made of a non-magnetic material such as stainless steel to prevent magnetic flux leakage through the bolts.

[0047] The first shaft portion 31 may be made of a non-magnetic material or a magnetic material (soft magnetic material). Furthermore, the first shaft portion 31 may be manufactured by forging technology or by other methods. If the first shaft portion 31 is made of a soft magnetic material, it may be manufactured by forging in conjunction with a forged rotor core 2 made of a soft magnetic material. Here, "integration" means a state in which continuous forging lines (metal flow lines) are formed that conform to the shapes of the integrated forged rotor core 2 and the first shaft portion 31.

[0048] As shown in Figure 1, in this embodiment, the first shaft portion 31 is constructed by integrally connecting a small-diameter shaft portion 31a, a bearing fitting portion 31b, a flange portion 31c, a large-diameter shaft portion 31d, and a fitting projection portion 31e, which are arranged in order from one side (left side in Figure 1) to the other side (right side in Figure 1) in the axial direction, coaxial with the axis AL.

[0049] The second shaft portion 32 is constructed by integrally connecting a bearing fitting portion 32a, an intermediate connecting shaft portion 32b, a large-diameter shaft portion 32c, and a flange portion 32d, which are arranged sequentially from the other side (right side in Figure 1) to the one side (left side in Figure 1) in the axial direction, coaxial with the axis AL. Furthermore, the second shaft portion 32 has a fitting recess 32e that can be fitted with the fitting projection 31e of the first shaft portion 31 when it is coaxial with the first shaft portion 31 on the axis AL. In Figure 1, the region including the fitting projection 31e and the fitting recess 32e is shown in a crushed cross section.

[0050] <Rotor Assembly> In this embodiment, the rotor 1 is assembled as follows. First, the cylindrical portion 2a of the forged rotor core 2 is fitted onto the large-diameter shaft portion 31d of the first shaft portion 31 such that the stepped portion provided at the boundary between the cylindrical portion 2a and the inclined protruding portion 2b of the forged rotor core 2 abuts against the flange portion 31c of the first shaft portion 31. Meanwhile, the cylindrical portion 5a of the second rotor core 5 is fitted onto the large-diameter shaft portion 32c of the second shaft portion 32 such that the end face of the cylindrical portion 5a of the second rotor core 5 abuts against the flange portion 32d of the second shaft portion 32. Next, the fitting projection 31e of the first shaft portion 31 and the fitting recess 32e of the second shaft portion 32 are fitted together. This centers the first shaft portion 31, the forged rotor core 2, the second shaft portion 32, and the second rotor core 5 so that their axes align on the axis AL. With the rotor centered, the flange portion 31c of the first shaft portion 31, the cylindrical portion 2a of the forged rotor core 2, the flange portion 32d of the second shaft portion 32, and the cylindrical portion 5a of the second rotor core 5 are fastened together with fasteners (such as bolts made of non-magnetic material) not shown. As a result, the first shaft portion 31, the forged rotor core 2, the second shaft portion 32, and the second rotor core 5 are integrally connected coaxially on axis AL. The rotor 1 assembled in this way is then incorporated into a motor case (not shown) with the bearing fitting portion 31b of the first shaft portion 31 and the bearing fitting portion 32a of the second shaft portion 32 each supported by bearings.

[0051] In rotor 1, a portion of the magnetic flux from stator core 61 attempts to flow through the annular plate portion 2c, inclined protruding portion 2b, and cylindrical portion 2a of forged rotor core 2, and then through the flange portion 32d of second shaft portion 32 to the cylindrical portion 5a of second rotor core 5. However, the flange portion 32d of second shaft portion 32 is interposed between the cylindrical portion 2a of forged rotor core 2 and the cylindrical portion 5a of second rotor core 5, and if the second shaft portion 32 is made of a non-magnetic material, the flow of magnetic flux from the cylindrical portion 2a of forged rotor core 2 to the cylindrical portion 5a of second rotor core 5 is blocked by the flange portion 32d of second shaft portion 32. Similarly, if a portion of the magnetic flux from the stator core 61 attempts to flow through the annular plate portion 5c, the inclined protruding portion 5b, and the cylindrical portion 5a of the second rotor core 5, and then through the flange portion 32d of the second shaft portion 32 to the cylindrical portion 2a of the forged rotor core 2, the flow of magnetic flux from the cylindrical portion 5a of the second rotor core 5 to the cylindrical portion 2a of the forged rotor core 2 is blocked by the flange portion 32d of the second shaft portion 32.

[0052] Thus, the shaft 3 includes a first shaft portion 31 provided on the forged rotor core 2 side and a second shaft portion 32 provided on the second rotor core 5 side, and the first shaft portion 31 and / or the second shaft portion 32 are made of a non-magnetic material (in this example, the second shaft portion 32 is made of a non-magnetic material). By adopting a configuration in which the forged rotor core 2 and the second rotor core 5 are connected with at least a part of the first shaft portion 31 and / or the second shaft portion 32 (in this example, the flange portion 32d of the second shaft portion 32) interposed between the forged rotor core 2 and the second rotor core 5, leakage of magnetic flux to the second rotor core 5 and / or the forged rotor core 2 can be suppressed, and the rotational efficiency of the rotor 1 can be further improved. Furthermore, since the configuration combines a connecting structure between the forged rotor core 2 and the second rotor core 5 via the shaft 3, and a structure to suppress magnetic flux leakage to the second rotor core 5 and / or the forged rotor core 2, there is no need to separately provide a magnetic flux leakage suppression structure, and it has the advantage of being able to suppress magnetic flux leakage to the second rotor core 5 and / or the forged rotor core 2 with a simple configuration.

[0053] <Stata> As shown in Figure 1, the stator 6 includes a stator core 61 around which electromagnetic coils are wound via bobbins (not shown). The stator 6 also includes a pair of fixing plates 62 for securing the stator core 61 and a coil housing member 63 for housing the electromagnetic coils.

[0054] Figure 2 is a schematic diagram illustrating the structure of the stator 6 of the axial gap motor 100 shown in Figure 1. Figure 2(a) is a front view of the axial gap motor 100 viewed in the axial direction from position AA in Figure 1. Note that the rotor 1 is omitted from the illustration in Figure 2(a). As shown in Figures 1 and 2(a), the stator 6 comprises a plurality of stator cores 61 arranged in the circumferential direction. A pair of fixing plates 62 fix the plurality of stator cores 61 by sandwiching them from both sides in the axial direction. The fixing plates 62 can be made of a non-magnetic material such as stainless steel. By making the fixing plates 62 of a non-magnetic material, interference of magnetic fields between adjacent stator cores 61 in the circumferential direction can be suppressed. Furthermore, it is preferable that the fixing plates 62 have openings at positions corresponding to the stator cores 61 so that magnetic flux can enter and exit the stator cores 61. In this case, for example, the stator core 61 can be fixed by sandwiching the axial end faces of the coil housing member 63 between the two fixing plates 62, with both ends of the stator core 61 fitted to the two fixing plates 62 together with a bobbin (not shown). Furthermore, the fixing plates 62 may be fixed by screwing them to the motor case (not shown) of the axial gap motor 100, for example. Also, although Figure 2(a) shows an example in which eight stator cores 61 are arranged, the number of stator cores 61 is not particularly limited.

[0055] Each stator core 61 can be constructed by stacking multiple plates 64 made of magnetic material in the radial direction. Figure 2(b) is a schematic diagram illustrating the structure of a stator core 61, illustrating a stator core 61 constructed by stacking multiple plates 64 in the radial direction (R direction). For example, in order to make the stator core 61 fan-shaped, processing the plates constituting the stator core 61 into curved plates that follow the outer surface of the stator 6 would require many steps and be costly to manufacture. In contrast, the stator core 61 according to this embodiment has multiple flat plates 64 stacked in the radial direction, so the structure of the stator core 61 is relatively simple, and manufacturing costs can be reduced. Furthermore, stacking multiple flat plates 64 made of magnetic material in the radial direction also has the effect of reducing iron loss in the stator core 61. In other words, the stator core 61 can also be constructed by stacking multiple plates 64 in the axial direction. However, in an axial gap motor, magnetic flux flows in the axial direction of the stator core, so stacking plates 64 in the axial direction results in iron loss at the plate boundaries. In contrast, stacking multiple plates 64 in the radial direction prevents the boundaries of the plates 64 from appearing in the magnetic path within the stator core 61, thereby suppressing iron loss at the plate boundaries. The type of plate 64 is not particularly limited as long as it is made of a magnetic material through which magnetic flux can pass. For example, electromagnetic steel sheets with elements such as silicon added to iron, or plates made of amorphous alloys can be used. The method of stacking multiple plates 64 is also not particularly limited, but can be done by adhesive bonding, for example. It goes without saying that in the laminate, adjacent plates in the stacking direction are joined via an insulating coating (including an adhesive layer).

[0056] Each of the stator cores 61 can also be configured such that the width of the plate 64 in the axial direction increases continuously or in steps as it moves away from the axis in the stacking direction. The stator core 61 shown in Figure 2(b) is configured such that the width of the plate 64 in the axial direction increases in steps (in three stages) as it moves away from the axis AL (towards the R1 direction). As shown in the figure, the stator core 61 comprises three blocks 65 (65a, 65b, 65c) formed by stacking multiple plates 64 in the radial direction. Of the blocks 65, block 65a, which is furthest from the axis AL (on the R1 side), has the largest width, and block 65c, which is closest to the axis AL (on the R2 side), has the smallest width.

[0057] To maximize the magnetic field generated from the stator core 61, it is preferable to make the stator core 61 fan-shaped. However, by configuring the width of the plates 64 constituting the stator core 61 to increase continuously or stepwise as they move away from the axis in the stacking direction, it is possible to approximate a fan-shaped form, making it easier to synchronize the rotational magnetic field generated from the stator with the rotation of the rotor. For example, this is effective when multiple fan-shaped magnets 4 are arranged circumferentially on the stator 6 side of the forged rotor core 2 with alternating polarities. In this case, when the stator core 61 and magnets 4 are projected onto the same plane in an axial view, one circumferential side of the stator core 61 and one circumferential side of the magnets 4 overlap. On the other hand, if the width of the plate 64 constituting the stator core 61 in the axial direction is kept constant regardless of the distance from the axis, then the circumferential side of the stator core 61 and the circumferential side of the magnet 4 will only overlap for a short distance, which is not advantageous in terms of synchronizing the rotational magnetic field generated by the stator with the rotation of the rotor. This also proves effective when applied to the reluctance motor type axial gap motor described later. This makes it possible to improve the rotational efficiency of the axial gap motor 100 while suppressing manufacturing costs.

[0058] Furthermore, manufacturing costs can be reduced by configuring the plates 64 that make up the stator core 61 so that their width in the axial direction increases gradually as they move away from the axis in the stacking direction. If the width were to increase continuously, it would be necessary to prepare many different types of plates 64 with different sizes (widths) in advance. Alternatively, a large steel plate could be prepared in advance and cut into plates 64 of various sizes using wire cutting, but this would result in wasted steel. In contrast, if the width increases gradually, for example, in the example shown in Figure 2(b), blocks 65a, 65b, and 65c can be formed by press lamination, and the stator core 61 can be constructed by stacking these three blocks, thus further reducing manufacturing costs. Even with this gradually increasing configuration, when the stator core 61 and magnet 4 are projected onto the same plane in the axial direction, one circumferential side of the stator core 61 and one circumferential side of the magnet 4 can be made to almost overlap. Therefore, it becomes easier to synchronize the rotating magnetic field generated from the stator with the rotation of the rotor, and the rotational efficiency of the axial gap motor 100 can be improved.

[0059] <Another Embodiment> In the above embodiment, the second shaft portion 32 is formed of a non-magnetic material, but instead, the first shaft portion 31 may be made of a non-magnetic material. In this case, it is preferable to interpose the flange portion 31c of the first shaft portion 31, which is made of a non-magnetic material, between the cylindrical portion 2a and the cylindrical portion 5a.

[0060] In the above embodiment, the forged rotor core 2 is assumed to be manufactured entirely by forging, but it may also be manufactured by a method other than forging. For example, the portion of the forged rotor core 2 in which the magnet 4 is installed may be constructed from a laminate formed by stacking multiple plates made of magnetic material (e.g., electromagnetic steel sheets) in the axial direction, while the remaining portion may be manufactured by forging. With such a configuration, since the laminate made of magnetic material is provided on the back side of the magnet 4 (one side in the axial direction, the left side in Figure 1), the magnetic field produced by the magnet 4 can be strengthened, and the rotational efficiency of the motor can be further improved. In addition, since the magnetic flux from the magnet 4 flows in the circumferential direction of the forged rotor core 2 within the plate, the generation of eddy currents can also be suppressed by stacking the plates in the axial direction. It goes without saying that in the laminate, adjacent plates in the stacking direction are joined via an insulating coating (including an adhesive layer).

[0061] In the above embodiment, the forged rotor core 2 is provided with magnets 4 on the side facing the stator 6, but instead, the side facing the stator 6 may be provided with an uneven surface. For example, multiple concave and convex shapes may be alternately arranged in the circumferential direction on the stator 6 side surface of the forged rotor core 2. In other words, the axial gap motor according to the present invention can also be a reluctance motor type axial gap motor. By providing such an uneven surface, it is possible to alternately provide areas with a small gap length (areas with low magnetic resistance) and areas with a large gap length (areas with high magnetic resistance) between the forged rotor core 2 and the stator 6, and the forged rotor core 2 can be rotated by utilizing this difference in magnetic resistance. With such a configuration, it becomes unnecessary to provide magnets 4 on the forged rotor core 2, so the cost of the rotor 1 can be further reduced. Furthermore, even in such a reluctance motor type axial gap motor, a laminate of multiple plates made of a magnetic material (e.g., electromagnetic steel sheets) stacked in the axial direction may be arranged on the side facing the stator 6 of the forged rotor core 2. In this case, it is preferable to place such a laminate in areas where the magnetic flux is particularly strong, that is, in areas where the magnetic resistance is small (areas where the gap length between the forged rotor core 2 and the stator 6 is small). [Industrial applicability]

[0062] The rotor and axial gap motor of the present invention are suitably used, for example, in rotating mechanisms in automobiles and robots. [Explanation of Symbols]

[0063] 1 rotor 2 Forged rotor core 3 shafts 4 Magnets 5. Second rotor core 6 staters 61 Stator Core 64 plates 100 Axial Gap Motor

Claims

1. A rotor for an axial gap motor, A forged rotor core that faces the stator in the axial direction with a gap between them, The rotor core is forged and the shaft is coaxial with it. The aforementioned forged rotor core is a rotor that is a hot-forged product.

2. The forged rotor core comprises a cylindrical portion, an inclined protruding portion, and an annular plate portion, The rotor according to claim 1, wherein the cylindrical portion is fitted onto the shaft.

3. The rotor according to claim 1, wherein the forged rotor core is provided with a magnet on the side facing the stator.

4. The rotor according to claim 1, wherein the forged rotor core is provided with an uneven portion on the side facing the stator.

5. The rotor according to claim 3 or 4, wherein the forged rotor core comprises a laminate formed by stacking a plurality of plates made of a magnetic material in the axial direction on the side facing the stator.

6. The rotor according to claim 1, wherein at least a portion of the shaft is made of a non-magnetic material.

7. It comprises a second rotor core that is paired with the aforementioned forged rotor core, The rotor according to claim 1, wherein the forged rotor core and the second rotor core are arranged to face each other via the stator.

8. Each of the forged rotor core and the second rotor core is provided with a plurality of magnets arranged circumferentially on the side facing the stator, The rotor according to claim 7, wherein the plurality of magnets are arranged such that the polarity of the magnets arranged in the forged rotor core and the polarity of the magnets arranged in the second rotor core are opposite to each other.

9. The rotor comprises the rotor described in claim 1 and a stator arranged coaxially with the forged rotor core, The stator has a plurality of stator cores arranged in the circumferential direction, Each of the stator cores is an axial gap motor constructed by stacking multiple plates made of magnetic material in the radial direction.

10. The axial gap motor according to claim 9, wherein the width of the plate when viewed in the axial direction increases continuously or stepwise as it moves away from the axis in the stacking direction.

11. The axial gap motor according to claim 9 or 10, wherein the stator comprises a pair of fixing plates that secure the plurality of stator cores by sandwiching them from both sides in the axial direction.

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