Eddy current reduction gear

Abstract

To provide a highly durable eddy current reduction gear.SOLUTION: An eddy current reduction gear (100) includes a rotor (10) and a stator (20). The rotor (10) includes a rotor body (11), a hub (12), and a spoke (13). The spoke (13) extends from the hub (12) toward the rotor body (11), has one end fixed to one axial end of the rotor body (11), and has the other end inserted into a recess provided on the hub (12). In the spoke, the hardness of the side surface (135) of the portion inserted into the recess of the hub (12) is higher than the hardness of the inner peripheral surface (122) of the recess of the hub (12).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an eddy current reducer. [Background technology]

[0002] Eddy current reduction gears have conventionally been used as auxiliary brakes for large vehicles such as trucks and buses. For example, as disclosed in Patent Document 1, an eddy current reduction gear includes a rotor fixed to the rotating shaft of the vehicle and a stator fixed to a non-rotating portion of the vehicle. The rotor includes a rotor body that is a cylindrical conductor, a hub attached to the rotating shaft, and spokes. The spokes extend from the hub toward the rotor body, with one end fixed to one axial end of the rotor body and the other end inserted into a recess provided in the hub. This connects the rotor body to the hub via the multiple spokes. The stator holds multiple magnets arranged circumferentially inside the rotor body.

[0003] In an eddy current reducer, the rotor rotates within a magnetic field created by a magnet, and the interaction between the magnetic field and eddy currents generated in the conductive rotor body generates a braking force in the opposite direction to the rotor's rotation. The state in which a braking force is generated is called the braking state. In the braking state, Joule heat is generated in the rotor body through which eddy currents flow, causing the rotor temperature to rise. When the temperature of the rotor body rises during braking, the rotor body expands due to heat, increasing its diameter.

[0004] Patent Document 2 discloses a technology for suppressing plastic deformation of the rotor body even when the rotor body thermally expands. In Patent Document 2, a rubber bushing is placed in a recess in the hub, and one end of the spoke is fixed to the rubber bushing. According to Patent Document 2, when the rotor body deforms due to thermal expansion, the spokes expand and contract in response to the deformation, resisting the shear force of the rubber bushing, thereby suppressing plastic deformation of the rotor body. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-78425 [Patent Document 2] Japanese Utility Model Application Publication No. 3-117375 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, when the eddy current reduction gear device is in a braking state, Joule heat is generated in the rotor body through which eddy currents flow, causing the temperature of the rotor body to rise. When the temperature of the rotor body rises during braking, the rotor body thermally expands and increases in diameter. On the other hand, when the eddy current reduction gear device is in a non-braking state, no magnetic field acts on the rotor body. In the non-braking state, no braking force is generated in the rotor body, and the rotor body does not generate heat. Therefore, when switching from the braking state to the non-braking state, the temperature of the rotor body decreases. When the temperature of the rotor body decreases during non-braking, the rotor body, which has thermally expanded, contracts in diameter. In other words, the rotor body repeatedly expands and contracts in diameter as it is repeatedly braked and non-braked.

[0007] When the rotor body thermally expands during braking, the spokes inserted into the recesses in the hub move radially outward, absorbing the deformation of the rotor body due to thermal expansion. This allows the rotor body to remain connected to the hub even in a thermally expanded state. When the rotor body contracts after switching to a non-braking state, the spokes move radially inward within the recesses in the hub. The repeated braking and non-braking of the eddy current reducer causes the spokes to repeatedly move within the recesses in the hub. During this process, the side surfaces of the spokes inserted into the recesses in the hub slide against the inner circumferential surface of the recesses in the hub.

[0008] When the eddy current reduction gear is in a braking state, the interaction between the eddy currents generated in the rotor body and the magnetic field generates a braking force in the rotor body in the direction opposite to the rotational direction. At this time, a load is applied in the circumferential direction of the rotor body to each spoke fixed to the rotor body. In other words, a braking force in the direction opposite to the rotational direction acts on the rotor body, and a load in the direction opposite to the rotational direction is applied to each spoke. As a result, when the eddy current reduction gear is in a braking state, the side of the portion of each spoke inserted into the recess in the hub slides against the inner surface of the recess in the hub while a load in the rotational direction is applied.

[0009] Furthermore, when the eddy current reduction gear device is in a braking state, the rotor body thermally expands and its diameter increases. At this time, deformation of one axial end of the rotor body is restricted by the spokes being fixed thereto. On the other hand, the other axial end of the rotor body is free to deform because the spokes are not fixed thereto. Therefore, the diameter of the rotor body at the end opposite to the spoke end is larger than the diameter of the end closest to the spoke. As a result, the axial load of the rotor body is applied to each spoke. As a result, when the eddy current reduction gear device is in a braking state, the side of the portion of each spoke inserted into the recess in the hub slides against the inner circumferential surface of the recess in the hub while an axial load is applied.

[0010] When the eddy current reduction gear is switched from the braking state to the non-braking state, the temperature of the rotor body drops, causing the rotor body to shrink in diameter and return to its original shape. As the switching between the braking state and the non-braking state is repeated, the side of the portion of each spoke inserted into the recess in the hub repeatedly slides against the inner surface of the recess in the hub while loads are applied in the rotational and axial directions.

[0011] In this way, the side surfaces of the spokes inserted into the recesses of the hub repeatedly slide against the inner circumferential surface of the recesses of the hub when loads are applied in the rotational and axial directions. However, conventional eddy current reduction gears such as those disclosed in Patent Documents 1 and 2 do not particularly consider wear and breakage caused by sliding of the spokes. If spoke wear can be suppressed by increasing durability against sliding under the above-mentioned loads, the durability of the eddy current reduction gear device will be improved.

[0012] An object of the present disclosure is to provide an eddy current reduction gear device that is excellent in durability. [Means for solving the problem]

[0013] The eddy current reduction device of the present disclosure is a rotor that rotates together with the rotary shaft, the rotor including: a cylindrical rotor body; a hub attached to a rotary shaft; and spokes extending from the hub toward the rotor body, one end of which is fixed to one axial end of the rotor body and the other end of which is inserted into a recess provided in the hub; a stator disposed inside or outside the rotor body; Equipped with In the spoke, The hardness of the side surface of the portion of the hub that is inserted into the recess is greater than the hardness of the inner peripheral surface of the recess of the hub. [Effects of the Invention]

[0014] The eddy current reduction gear device of the present disclosure has excellent durability. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an eddy current reduction gear according to an embodiment. [Figure 2] FIG. 2 is a front view of the eddy current reduction gear device according to the embodiment. [Figure 3] FIG. 3 is a view of the rotor included in the eddy current reduction gear device shown in FIGS. 1 and 2, viewed from the spoke side. [Figure 4] FIG. 4 is a schematic diagram for explaining the circumferential load applied to the spokes in the rotor of the eddy current reduction gear device. [Figure 5] FIG. 5 is a schematic diagram for explaining the axial load applied to the spokes in the rotor of the eddy current reduction gear device. [Figure 6] FIG. 6 is a schematic diagram for explaining the braking state of the eddy current reduction gear device shown in FIGS. [Figure 7] FIG. 7 is a schematic diagram for explaining the non-braking state of the eddy current reduction gear device shown in FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0016] As described above, when the eddy current reduction gear is in a braking state, the spokes slide against the inner circumferential surface of the recess in the hub while the rotor body is subjected to circumferential and axial loads. Fig. 4 is a schematic diagram illustrating the circumferential load applied to the spokes in the rotor of the eddy current reduction gear. Fig. 5 is a schematic diagram illustrating the axial load applied to the spokes in the rotor of the eddy current reduction gear.

[0017] As shown in FIG. 4 , when a braking force F in a direction opposite to the rotational direction R is generated in the rotor body 11 of the rotor 10 of the eddy current reduction gear, a load P1 is applied to the spokes 13 connecting the rotor body 11 to the hub 12 in the circumferential direction z of the rotor body 11. In this specification, when the eddy current reduction gear is not braking, the portions of the spokes 13 inserted into the recesses of the hub are referred to as insertion portions 131. In this specification, when the eddy current reduction gear is not braking, the portions of the spokes 13 exposed from the recesses of the hub are referred to as non-insertion portions 132. When the eddy current reduction gear is braking, a load P1 in the same direction as the braking force F is applied to the ends of the spokes 13 connected to the rotor body 11. At this time, a load P2 in the opposite direction to the load P1 is applied to the insertion portions 131 in the circumferential direction z of the rotor body 11, with the boundary between the insertion portions 131 and the non-insertion portions 132 serving as a fulcrum.

[0018] 5, when rotor body 11 thermally expands and the end of rotor body 11 opposite spokes 13 expands in diameter relatively significantly, a load P3 is applied to spokes 13 in the axial direction x of rotor body 11. A load P4 is applied to insertion portion 131 in the axial direction x of rotor body 11 in the opposite direction to load P3, with the boundary between insertion portion 131 and non-insertion portion 132 as a fulcrum.

[0019] As described above, when the eddy current reducer is braked, the rotor body 11 expands in diameter due to thermal expansion. As the rotor body 11 expands in diameter, the spokes 13 move radially outward in the recessed portion of the hub 12. At this time, the side surfaces of the insertion portions 131 slide against the inner circumferential surface of the recessed portion of the hub 12. By switching from the braked state to the unbraked state, the spokes 13 move radially inward in the y direction in the recessed portion of the hub 12 and return to their original positions. By repeatedly switching between the braked state and the unbraked state, the side surfaces of the insertion portions 131 repeatedly slide against the inner circumferential surface of the recessed portion of the hub 12.

[0020] If the insertion portions 131 of the spokes 13 are worn and damaged due to repeated sliding under load, there is a possibility that the spokes 13 will break. On the other hand, if the inner circumferential surfaces of the recesses in the hub 12 are worn and damaged due to repeated sliding under load, the recesses in the hub 12 will expand and deform. In this case, the spokes 13 will not be able to be held in their predetermined positions within the recesses in the hub 12, resulting in so-called rattle. When considering the durability of the eddy current reduction gear device, breakage of the spokes 13 has a greater impact than rattle of the hub 12. Therefore, by increasing the hardness of the side surfaces of the insertion portions 131 of the spokes 13 compared to the hardness of the inner circumferential surfaces of the recesses in the hub 12, breakage of the spokes 13 can be suppressed. This improves the durability of the eddy current reduction gear device.

[0021] The eddy current reduction gear of this embodiment, which was completed based on the above findings, has the following configuration.

[0022] [1] An eddy current reduction gear, a rotor that rotates together with the rotary shaft, the rotor including: a cylindrical rotor body; a hub attached to a rotary shaft; and spokes extending from the hub toward the rotor body, one end of which is fixed to one axial end of the rotor body and the other end of which is inserted into a recess provided in the hub; a stator disposed inside or outside the rotor body; Equipped with In the spoke, the hardness of the side surface of the portion of the hub inserted into the recess is higher than the hardness of the inner peripheral surface of the recess of the hub; Eddy current reduction device.

[0023] In the spokes of the eddy current reduction gear device configured as in [1], the hardness of the side of the portion (insertion portion) inserted into the recess of the hub is greater than the hardness of the inner peripheral surface of the recess of the hub. This prevents wear on the insertion portion of the spoke even when the eddy current reduction gear device repeatedly slides under radial and axial loads due to repeated braking and unbraking. This prevents breakage of the spoke. As a result, the durability of the eddy current reduction gear device is improved.

[0024] Eddy current reduction gears are required to be small and lightweight in order to improve the ease of mounting on vehicles and the fuel efficiency of vehicles. In order to make eddy current reduction gears small and lightweight, the spokes must also be made small. According to the configuration of [1], the spokes are less likely to break, making it possible to make the spokes smaller. As a result, the eddy current reduction gear can be made small and lightweight.

[0025] Eddy current reduction gears are required to have high braking force, for example, to overcome the lack of braking performance of vehicles with heavy loads. In an eddy current reduction gear with high braking force, the high braking force and the resulting large amount of heat generated increase the load on the spokes, making them more susceptible to breakage. However, with the configuration of [1], spoke breakage can be suppressed even when loads are applied in the circumferential and axial directions of the rotor body. Therefore, the eddy current reduction gear with the configuration of [1] can accommodate high braking force.

[0026] [2] [1] The eddy current reduction gear according to the present invention, In the spoke, The Vickers hardness of the side surface of the portion of the hub inserted into the recess is 2.00 to 4.00 times the Vickers hardness of the inner peripheral surface of the recess of the hub. Eddy current reduction device.

[0027] According to the configuration of [2], the Vickers hardness of the side of the spoke insertion portion is 2.00 to 4.00 times the Vickers hardness of the inner peripheral surface of the recessed portion of the hub. This more stably suppresses spoke wear, which in turn more stably suppresses spoke breakage. Furthermore, wear of the recessed portion of the hub is suppressed, which in turn suppresses hub rattle.

[0028] [3] The eddy current reduction gear according to [1] or [2], In the spoke, the hardness of the side surface of the portion of the hub inserted into the recess is higher than the hardness of the surface of the portion of the hub exposed from the recess; Eddy current reduction device.

[0029] According to the configuration [3], the Vickers hardness of the side surface of the inserted part of the spoke is higher than the Vickers hardness of the surface of the non-inserted part of the spoke. This improves the weldability of the ends of the spokes that are fixed to the rotor body, and suppresses weld cracks, even when the spokes are fixed to the rotor body by welding.

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0031] [Configuration of eddy current reducer] FIG. 1 is a longitudinal cross-sectional view showing the schematic configuration of an eddy current reduction gear 100 according to this embodiment. The eddy current reduction gear 100 is used, for example, as an auxiliary brake for a vehicle such as a truck or a bus. The longitudinal cross-section refers to a cross-section taken along a plane including an axis X of a rotating shaft 200 of a vehicle in which the eddy current reduction gear 100 is used. The rotating shaft 200 is, for example, a propeller shaft or a drive shaft. Hereinafter, the direction in which the axis X extends will be referred to as the axial direction x, and the radial direction y and circumferential direction z of a ring or cylinder centered on the axis X will be simply referred to as the radial direction y and the circumferential direction z.

[0032] 1, the eddy current reduction gear 100 includes a rotor 10 and a stator 20. The rotor 10 rotates around an axis X together with a rotating shaft 200 of a vehicle. The stator 20 is fixed to a non-rotating part of the vehicle, such as a transmission cover, so as not to rotate together with the rotating shaft 200.

[0033] The rotor 10 includes a rotor body 11, a hub 12, and a plurality of spokes 13. The rotor body 11 is substantially cylindrical and centered on the axis X of the rotation shaft 200. The rotor body 11 is made of a ferromagnetic material such as carbon steel, low-alloy steel, or cast steel. More specifically, the rotor body 11 is made of chromium-molybdenum steel, low-alloy cast steel, or the like. Furthermore, the rotor body 11 may be made of steel containing, for example, in mass %, C: 0.05 to 0.15%, Si: 0.10 to 0.40%, Mn: 0.5 to 1.0%, P: 0.05% or less, Ni: 0.50% or less, Mo: 0.2 to 1.0%, Nb: 0.01 to 0.03%, V: 0.03 to 0.07%, B: 0.0005 to 0.003%, Sol.Al: 0.02 to 0.09%, N: 0.01% or less, and the balance being Fe and impurities. The material constituting the rotor body 11 preferably has high heat resistance. The inner peripheral surface of the rotor body 11 may be coated with a copper plating layer having high conductivity. A plurality of heat dissipation fins 14 are provided on the outer peripheral surface of the rotor body 11.

[0034] Referring to FIG. 1, the hub 12 is disposed inward of the rotor body 11 in the radial direction y. Referring to FIG. 1, the hub 12 is disposed offset from the rotor body 11 to one side in the axial direction x. The hub 12 has a generally annular plate shape centered on the axis X of the rotating shaft 200. The hub 12 is attached to the rotating shaft 200 via a support member 15. The hub 12 is made of, for example, steel, and typically cast iron. The hub 12 is made of, for example, carbon steel for machine structures as specified in JIS G4051 (2016) or spheroidal graphite cast iron as specified in JIS G5502 (2001).

[0035] FIG. 2 is a front view of the eddy current reducer 100. Referring to FIG. 2, a plurality of spokes 13 are arranged radially around the hub 12. Each spoke 13 extends in the radial direction y from the hub 12 toward the rotor body 11. Each spoke 13 connects the rotor body 11 to the hub 12 attached to the rotating shaft 200. Therefore, the rotor body 11 rotates around the axis X together with the rotating shaft 200, the hub 12, and the spokes 13. Although not particularly limited, for example, about 8 to 10 spokes 13 are provided between the rotor body 11 and the hub 12.

[0036] 3 is a view of the rotor 10 included in the eddy current reducer 100 shown in FIGS. 1 and 2, viewed from the spoke 13 side. Referring to FIG. 3, an outer end 133 of each spoke 13 in the radial direction y is fixed to one end of the rotor body 11 in the axial direction x. An inner end 134 of each spoke 13 in the radial direction y is inserted into a recess 121 provided on the outer peripheral surface of the hub 12. The end 134 is not fixed to the hub 12.

[0037] The spokes 13 are made of a ferromagnetic material such as carbon steel or cast steel. More specifically, the spokes 13 are made of, for example, chromium-molybdenum steel or low-alloy cast steel. The material making up the spokes 13 preferably has high strength. For example, SCM415, SCM420, SCM435, and SCM440 as specified in JIS G4053 (2016) can be used as the material making up the spokes 13. The material of the spokes 13 may be different from or the same as the material of the rotor body 11.

[0038] 1, the stator 20 is disposed inside the rotor body 11 in the radial direction y. The stator 20 includes a stator case 21, a magnet holding member 22, a plurality of permanent magnets 23, and a plurality of pole pieces 24.

[0039] The stator case 21 includes a case body 211 and a body holding member 212. The case body 211 is formed in a roughly annular plate shape centered on the axis X. The case body 211 faces the surfaces of the spokes 13. It is preferable that the surfaces of the case body 211 facing the spokes 13 are flat surfaces that are substantially parallel to the surfaces of the spokes 13. The case body 211 is fixed to the body holding member 212.

[0040] Body holding member 212 includes a side portion 212a facing case body 211 and a bottom portion 212b protruding from side portion 212a toward case body 211. Bottom portion 212b is attached to a non-rotating portion of the vehicle via a support portion 212c. An accommodation space is formed inside stator 20 by case body 211 and side portion 212a and bottom portion 212b of body holding member 212. Magnet holding member 22, a plurality of permanent magnets 23, and a plurality of pole pieces 24 are arranged in this accommodation space.

[0041] The magnet holding member 22 has a cylindrical shape centered on the axis X. The magnet holding member 22 is disposed substantially coaxially with the rotor body 11. The magnet holding member 22 is made of a ferromagnetic material such as carbon steel or cast steel.

[0042] The magnet holding member 22 is attached to the stator case 21 via, for example, a ring-shaped slide plate (not shown) so as to be slidable in the circumferential direction z. The magnet holding member 22 is connected to a drive device (not shown) such as an air cylinder or an electric actuator by a link mechanism (not shown). When this drive device is activated, the magnet holding member 22 rotates around the rotation axis 200 and moves in the circumferential direction z relative to the stator case 21. By rotating the magnet holding member 22 around the rotation axis 200, the eddy current reduction gear 100 is switched between a braking state and a non-braking state.

[0043] 6 is a partial cross-sectional view of the eddy current reduction gear device 100 taken along a plane perpendicular to the axis X of the rotating shaft 200. In FIG. 6, the stator case 21 is omitted.

[0044] As shown in Fig. 6, the magnet holding member 22 holds a plurality of permanent magnets 23 on its outer circumferential surface. These permanent magnets 23 are arranged at predetermined intervals in the circumferential direction z. Each of the permanent magnets 23 is fixed to the outer circumferential surface of the magnet holding member 22 by, for example, an adhesive. The permanent magnets 23 are, for example, neodymium magnets, ferrite magnets, samarium-cobalt magnets, or the like.

[0045] Each of the permanent magnets 23 has a pair of magnetic poles (North and South poles). The direction of the magnetic poles of each permanent magnet 23 is along the radial direction y and is opposite to the direction of the magnetic poles of the adjacent permanent magnets 23. That is, each permanent magnet 23 has a North or South pole on the inner side in the radial direction y and an opposite South or North pole on the outer side in the radial direction y.

[0046] The pole pieces 24 are made of a ferromagnetic material such as carbon steel or cast steel. The pole pieces 24 are arranged at predetermined intervals in the circumferential direction z between the rotor body 11 and the permanent magnets 23. In this embodiment, the number of pole pieces 24 is equal to the number of permanent magnets 23.

[0047] [Detailed rotor configuration] The configuration of the rotor 10 will be described in more detail below with reference to FIG.

[0048] 3 is a view of the rotor 10 included in the eddy current reducer 100 shown in FIGS. 1 and 2, viewed from the spoke 13 side. Referring to FIG. 3, the spokes 13 extend in the radial direction y between the rotor body 11 and the hub 12. Of both ends 133, 134 of the spokes 13 in the radial direction y, the outer end 133 is fixed to the end surface of the cylindrical rotor body 11 by, for example, welding. The inner end 134 is inserted into a recess 121 of the hub 12 so that the spoke 13 is movable in the radial direction y relative to the hub 12. The recess 121 of the hub 12 includes an inner circumferential surface 122 and a bottom surface 123.

[0049] The insertion portions 131 of the spokes 13 include side surfaces 135 and a bottom surface 136. The hardness of the side surfaces 135 of the insertion portions 131 of the spokes 13 is greater than the hardness of the inner circumferential surfaces 122 of the recesses 121 of the hub 12. The hardness of the side surfaces 135 of the insertion portions 131 can be increased by subjecting the insertion portions 131 of the spokes 13 to a treatment selected from the group consisting of quenching, carburizing, nitriding, and plating layer formation. The surface hardness of the entire spokes 13 may be increased, or the surface hardness of only the insertion portions 131 of the spokes 13 may be increased. Preferably, the hardness of the side surfaces 135 of the insertion portions 131 is greater than the surface hardness of the non-insertion portions 132. This improves the weldability of the ends 133 of the spokes 13 fixed to the rotor body 11, thereby suppressing weld cracking, even when the non-insertion portions 132 of the spokes 13 are fixed to the rotor body 11 by welding.

[0050] The surface hardness of the spokes 13 may be increased by quenching. When increasing the surface hardness of the entire spokes 13, the surface hardness may be increased by quenching the entire spokes 13. When increasing the surface hardness of only the insertion portions 131 of the spokes 13, only the insertion portions 131 of the spokes 13 may be heated and quenched, or the entire spokes 13 may be quenched and then only the non-insertion portions 132 may be softened by tempering. Well-known conditions may be used for quenching. For example, quenching conditions include holding at 830 to 900°C for 30 to 60 minutes, followed by rapid cooling.

[0051] The surface hardness of the spokes 13 may be increased by carburizing or nitriding. The carburizing and nitriding conditions may be well-known. For example, the carburizing conditions are 900-950°C for 60-240 minutes in a CO-containing gas atmosphere. For example, the nitriding conditions are 500-580°C for 24-72 hours in an ammonia gas atmosphere. The entire spokes 13 may be carburized or nitrided. This increases the surface hardness of the entire spokes 13. If the surface hardness of only the insertion portions 131 of the spokes 13 is to be increased, an anti-carburizing or anti-nitriding agent may be applied to the non-insertion portions 132 of the spokes 13, and then the carburizing or nitriding treatment may be performed under the above-mentioned conditions.

[0052] The surface hardness of the entire spoke 13 or only the insertion portion 131 of the spoke 13 may be increased by forming a plating layer. The plating layer is selected from the group consisting of chromium plating, nickel phosphorus plating, and nickel boron plating, for example. Well-known plating conditions may be used. When forming chromium plating, a plating solution containing 175 to 300 g / L of chromic anhydride and 1.75 to 3.0 g / L of sulfuric acid at a temperature of 40 to 55°C is used, and the current density is, for example, 10 to 60 dA / m 2 When forming nickel phosphorus plating, a plating solution containing 15 to 150 g / L of nickel sulfate, 5 to 130 g / L of sodium hypophosphite, pH 4 to 11, and temperature 30 to 100°C may be used. When forming nickel boron plating, a plating solution containing 15 to 80 g / L of nickel sulfate, 0.2 to 2.0 g / L of sodium borohydride, pH 12 to 14, and temperature 60 to 100°C may be used. The plating bath may contain other components such as surfactants and reducing agents in addition to the above-mentioned components.

[0053] [Surface hardness measurement method] The hardness of the side surface 135 of the insertion portion 131 of the spoke 13, the surface hardness of the non-insertion portion 132, and the hardness of the inner surface 122 of the recess 121 of the hub 12 are determined by measuring Vickers hardness (HV). A Vickers hardness test is conducted in accordance with JIS Z 2244 (2009). The test force is 9.8 N (1 kgf). The measurement is performed at room temperature (23 ± 5°C). After polishing the side surface 135 of the insertion portion 131 of the spoke 13, the Vickers hardness is measured at five arbitrary points on the side surface 135 of the insertion portion 131. After polishing the surface of the non-insertion portion 132 of the spoke 13, the Vickers hardness is measured at five arbitrary points on the surface of the non-insertion portion 132. The hub 12 is cut so that the inner circumferential surface 122 of the hub recess 121 is exposed (for example, by cutting the center of the recess 121 in the radial direction y (a direction perpendicular to the bottom surface 123 of the recess 121)), and the inner circumferential surface 122 of the recess 121 is exposed and polished. The Vickers hardness is measured at five arbitrary points on the polished inner circumferential surface 122. The arithmetic mean of the values ​​obtained at the five arbitrary points is defined as the surface hardness of each portion.

[0054] Preferably, the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is 2.00 to 4.00 times the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12. If the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is 2.00 or more times the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12, wear of the spoke 13 can be more reliably suppressed. This more reliably suppresses breakage of the spoke 13. On the other hand, if the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is 4.00 or less times the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12, wear of the inner circumferential surface 122 of the recess 121 of the hub 12 can be suppressed, and rattle of the hub 12 can be suppressed.

[0055] Preferably, the lower limit of the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is 2.10 times, more preferably 2.20 times, more preferably 2.30 times, even more preferably 2.50 times, and even more preferably 2.70 times the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12. Preferably, the upper limit of the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is 3.90 times, more preferably 3.70 times, even more preferably 3.50 times, even more preferably 3.30 times, and even more preferably 3.10 times the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12.

[0056] Although not particularly limited, the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is, for example, more than 300 HV. The lower limit of the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is more preferably 350 HV, even more preferably 400 HV, even more preferably 500 HV, even more preferably 600 HV, and even more preferably 650 HV. The upper limit of the Vickers hardness of the side surface 135 of the insertion portion 131 of the spoke 13 is not particularly limited, but is, for example, 750 HV.

[0057] If the surface hardness of the non-insertion portions 132 of the spokes 13 is low, the weldability of the non-insertion portions 132 can be stably improved. Preferably, the Vickers hardness of the surfaces of the non-insertion portions 132 of the spokes 13 is 400 HV or less. The upper limit of the Vickers hardness of the surfaces of the non-insertion portions 132 of the spokes 13 is more preferably 390 HV, even more preferably 370 HV, even more preferably 350 HV, even more preferably 330 HV, even more preferably 300 HV, even more preferably 280 HV, and even more preferably 240 HV. The lower limit of the Vickers hardness of the surfaces of the non-insertion portions 132 of the spokes 13 is not particularly limited, but is, for example, 170 HV.

[0058] Although not particularly limited, the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12 is, for example, 300 HV or less. The upper limit of the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12 is more preferably 280 HV, even more preferably 250 HV, even more preferably 200 HV, and even more preferably 160 HV. The lower limit of the Vickers hardness of the inner circumferential surface 122 of the recess 121 of the hub 12 is not particularly limited, but is, for example, 120 HV.

[0059] [Operation of eddy current reducer] The operation of the eddy current reduction gear 100 will be described below mainly with reference to Figures 6 and 7. Figures 6 and 7 are schematic diagrams for explaining the braking state and non-braking state of the eddy current reduction gear 100, respectively.

[0060] (braking state) First, referring to FIG. 6, when the eddy current reducer 100 is in a braking state, each permanent magnet 23 is positioned directly below the pole piece 24. Therefore, magnetic flux B from each permanent magnet 23 passes through the pole piece 24 and reaches the rotor body 11, which rotates together with the rotating shaft 200. This generates eddy currents on the inner circumferential surface of the rotor body 11. Due to the interaction between this eddy current and the magnetic field generated by the permanent magnets 23, a braking force F is generated in the rotor body 11 in the direction opposite to the rotation direction R. Furthermore, with the generation of eddy currents, Joule heat is generated in the rotor body 11, causing the temperature of the rotor body 11 to rise. This causes thermal expansion of the rotor body 11.

[0061] (non-braking state) 7, when the eddy current reduction gear 100 switches from the braking state to the non-braking state, the magnet holding member 22 rotates, and each permanent magnet 23 is positioned so as to straddle the adjacent pole piece 24. In the non-braking state, a magnetic circuit is formed among the magnet holding member 22, permanent magnet 23, and pole piece 24, and magnetic flux B from the permanent magnet 23 does not reach the rotor body 11. Therefore, the braking force on the rotor body 11 is released.

[0062] [effect] In the eddy current reduction gear 100 of this embodiment, the hardness of the side surface 135 of the insertion portion 131 of the spokes 13 is greater than the hardness of the inner circumferential surface 122 of the recess 121 of the hub 12. This makes it possible to suppress wear of the spokes 13 even when the eddy current reduction gear 100 repeatedly slides while being subjected to loads in the radial direction y and the axial direction x due to repeated braking and unbraking. This increases the durability of the eddy current reduction gear 100. [Example]

[0063] The effects of the eddy current reduction gear device of this embodiment will be explained more specifically using examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the eddy current reduction gear device of this embodiment. Therefore, the eddy current reduction gear device of this embodiment is not limited to this one example of conditions.

[0064] An eddy current type reduction gear was manufactured, and a thermal load durability test was carried out in which braking and non-braking were repeated to check whether or not the spokes had worn out.

[0065] The eddy current reduction gear included a rotor and a stator. The rotor included a rotor body, a hub, and spokes. The rotor body had a chemical composition, in mass%, of C: 0.05-0.15%, Si: 0.10-0.40%, Mn: 0.5-1.0%, P: 0.05% or less, Ni: 0.50% or less, Mo: 0.2-1.0%, Nb: 0.01-0.03%, V: 0.03-0.07%, B: 0.0005-0.003%, Sol.Al: 0.02-0.09%, N: 0.01% or less, and the balance being Fe and impurities. The rotor body had an inner diameter of 390 mm, an outer diameter of 440 mm, and a fin height of 14 mm.

[0066] The hubs were made of spheroidal graphite cast iron (JIS G 5502 (2001) FCD450) or carbon steel for mechanical structures (JIS G 4051 (2016) S45C). The hubs for test numbers 1 to 3 and 7 were manufactured by casting and then machining. The hubs for test numbers 4 to 6 and 8 were manufactured by hot forging and then machining. The hubs had an outer diameter of 325 mm and a hole in the center for passing the propeller shaft through. The diameter of this hole was 230 mm at its maximum and 160 mm at its minimum. For test numbers 1 to 3 and 7, the chemical composition of the hubs was changed within the range of the FCD450 standard, and the hardness of the inner surface of the hub recess was adjusted to the values ​​shown in Table 1. For test numbers 4 to 6 and 8, the machined hubs were normalized at temperatures ranging from 820 to 880°C, and the hardness of the inner peripheral surface of the hub recess was adjusted to the values ​​shown in Table 1.

[0067] [Table 1]

[0068] The spokes were made of JIS G 4051 (2009) SCM415 chrome-molybdenum steel. After hot forging, a carburizing inhibitor was applied to the surface of the non-inserted section, and gas carburizing and quenching were performed to increase the hardness of the side of the inserted section. The overall length of the spoke, including the inserted section and non-inserted section, was 85 mm. The inserted section was cylindrical, with a diameter of 15 mm and a length of 22 mm. The gas carburizing and quenching conditions were adjusted appropriately within the range of 900–930°C and 60–180 minutes in a CO-containing gas atmosphere to vary the hardness of the side of the inserted section. There were eight spokes, evenly spaced around the hub.

[0069] The eddy current reducer for each test number was assembled using hubs and spokes whose hardness was adjusted as shown in Table 1.

[0070] [Heat load durability test] A thermal load durability test was conducted on the eddy current reduction gear device with each test number. The temperature measurement point was a point 2 mm deep in the thickness direction at the axial center of the inner surface of the rotor body. The eddy current reduction gear device was repeatedly braked and unbraked while the rotor rotation speed was kept constant at 3,000 rpm. The eddy current reduction gear device was placed in the braked state, and when the temperature at the temperature measurement point reached 700°C, it was switched to the unbraked state. The eddy current reduction gear device was placed in the unbraked state, and when the temperature at the temperature measurement point reached 100°C, it was switched to the braked state. This cycle of switching between the braked and unbraked states was repeated 20,000 times.

[0071] The surface of the spoke insertion point was visually inspected after the heat load endurance test. If no scratches were found, it was rated "E" (Excellent). If only thin stripe-like scratches less than 1 mm wide were found, it was rated "A" (Acceptable). If planar scratches and / or defects 1 mm or wider were found, it was rated "NA" (Not Acceptable). The results are shown in the "Evaluation Results" and "Spoke" columns in Table 1.

[0072] After the heat load endurance test, the state of the spokes inserted into the recesses in the hub was visually observed. If there was no wobble in the spokes, it was rated "E" (Excellent). If there was no wobble in the spokes but a small gap was confirmed between the spokes and the recesses in the hub, it was rated "G" (Good). If wobble in the spokes was confirmed, it was rated "A" (Acceptable). The results are shown in the "Evaluation Results" and "Hub" columns in Table 1.

[0073] [Surface hardness measurement test] The Vickers hardness was measured on the side of the spoke insertion portion, the surface of the non-inserted portion, and the inner surface of the recessed portion of the hub. Vickers hardness tests were conducted in accordance with JIS Z 2244 (2009). The test force was 9.8 N (1 kgf). Measurements were performed at room temperature (23 ± 5°C). The Vickers hardness tests were conducted on test specimens manufactured under the same conditions as the spokes and hubs for each test number. After polishing the surface of the test specimen corresponding to the spoke insertion portion, the Vickers hardness was measured at five random locations on the surface of the test specimen. These were recorded as the Vickers hardness of the side of the spoke insertion portion. The results are shown in Table 1 under the columns "Spoke" and "Hardness (HV) of the side of the inserted portion." After polishing the surface of the test specimen corresponding to the non-inserted portion of the spoke, the Vickers hardness was measured at five random locations on the surface of the test specimen. These were recorded as the Vickers hardness of the surface of the non-inserted portion of the spoke. The results are shown in Table 1 under the columns "Spoke" and "Surface hardness (HV) of the non-inserted portion." After polishing the surface of the test piece corresponding to the hub, the Vickers hardness was measured at five random locations on the surface of the test piece, and this was taken as the Vickers hardness of the inner surface of the hub recess. The results are shown in the "Hub" and "Hardness (HV) of Inner Surface" columns in Table 1. The Vickers hardness of each location was calculated as the arithmetic mean of the values ​​obtained at five random locations.

[0074] The "Hardness ratio of sliding parts" and "(Hardness of spokes / hardness of hub)" columns in Table 1 show the values ​​obtained by dividing the Vickers hardness corresponding to the side of the spoke insertion part by the Vickers hardness corresponding to the inner surface of the recess in the hub.

[0075] [Evaluation results] In the eddy current reduction gears of test numbers 1 to 6, the hardness of the side surfaces of the spokes where they were inserted into the recesses of the hub (insertion portions) was greater than the hardness of the inner peripheral surfaces of the recesses of the hub. As a result, after the thermal load endurance test, no scratches were found on the side surfaces of the spoke insertion portions, or only thin stripe-like scratches less than 1 mm wide were found. In other words, the eddy current reduction gears of test numbers 1 to 6 were able to suppress damage caused by wear of the spokes and had excellent durability.

[0076] Furthermore, for the eddy current reduction devices of test numbers 2 to 5, the Vickers hardness of the side of the spoke where it was inserted into the recess of the hub (insertion portion) was between 2.00 and 4.00 times the Vickers hardness of the inner circumferential surface of the hub recess. As a result, no scratches were found on the insertion portion of the spoke after the thermal load endurance test, and no wobbling of the spoke was found after the thermal load endurance test. In other words, the eddy current reduction devices of test numbers 2 to 5 were able to more stably suppress damage caused by spoke wear and also suppress wear on the inner circumferential surface of the hub recess.

[0077] On the other hand, for the eddy current reduction devices of test numbers 7 and 8, the Vickers hardness of the side of the spoke where it was inserted into the recess of the hub (insertion portion) was lower than the hardness of the inner surface of the recess of the hub. As a result, for the eddy current reduction device of test number 7, a planar defect with a width of 1 mm or more was confirmed at the insertion portion of the spoke after the thermal load endurance test. For the eddy current reduction device of test number 8, a planar scratch mark with a width of 1 mm or more was confirmed at the insertion portion of the spoke after the thermal load endurance test. In other words, the eddy current reduction devices of test numbers 7 and 8 were unable to suppress damage due to wear of the spokes and were unable to improve durability.

[0078] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0079] In the above embodiment, the surfaces of the spokes 13 facing the rotor body 11 are substantially flat. However, the shape of the surfaces of the spokes 13 is not limited to this. For example, the surfaces of the spokes 13 may be convexly curved surfaces facing the rotor body 11, or concavely curved surfaces facing in the opposite direction.

[0080] In the above embodiment, the stator 20 is disposed inside the rotor body 11 in the radial direction y. However, the stator 20 may be disposed outside the rotor body 11 in the radial direction y.

[0081] In the above embodiment, the rotor 10 including the spokes 13 is used in the permanent magnet type eddy current reduction gear 100. However, the rotor 10 can also be used in an electromagnet type eddy current reduction gear. That is, in the eddy current reduction gear 100, electromagnets can be provided in place of the magnet holding members 22, permanent magnets 23, pole pieces 24, etc. When adopting the cross-sectional shape of the spokes 13 in the above embodiment, the structure of the stator 20 is not particularly limited. [Explanation of symbols]

[0082] 100: Eddy current reduction device 10: Rotor 11: Rotor body 12: Hub 13: Spoke 20: Stator 121: Recess 122: Inner surface 131: Insertion section 132: Non-insertion part 135: Side 200: Rotation axis

Claims

1. An eddy current reduction gear, a rotor that rotates together with the rotary shaft, the rotor including: a cylindrical rotor body; a hub attached to a rotary shaft; and spokes extending from the hub toward the rotor body, one end of which is fixed to one axial end of the rotor body and the other end of which is inserted into a recess provided in the hub; a stator disposed inside or outside the rotor body; Equipped with In the spoke, the Vickers hardness of the side surface of the portion of the hub inserted into the recess is 2.00 to 4.00 times the Vickers hardness of the inner peripheral surface of the recess of the hub; Eddy current reduction device.

2. 2. The eddy current reduction gear according to claim 1, In the spoke, the hardness of the side surface of the portion of the hub inserted into the recess is higher than the hardness of the surface of the portion of the hub exposed from the recess; Eddy current reduction device.

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