Rotary electric machine

Abstract

To provide a rotary electric machine having a simple configuration and capable of improving an output during high rotation while maintaining high torque during low rotation without using non-magnetic fluid.SOLUTION: A rotary electric machine includes a stator core 11 having a substantially annular yoke 11a and a plurality of teeth 11a extending in a radial direction from the yoke 11b. A flow path 11c of a magnetic fluid is provided inside the teeth 11b. The magnetic fluid is circulated through the flow path 11c when rotation speed of a rotor 2 is equal to or lower than a predetermined value. The magnetic fluid is extracted from the flow path 11c when the rotation speed of the rotor 2 is higher than the predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine in which a flow path for a magnetic fluid is provided inside the teeth of a stator core. [Background technology]

[0002] A rotating electric machine is known that includes a stator having a coil wound around a stator core with multiple teeth extending radially from a substantially annular yoke, and a rotor with embedded permanent magnets. This type of rotating electric machine rotates the rotor by sequentially passing current through the multiple coils wound around the teeth, resulting in an interaction between the rotating magnetic field generated in the coils and the magnetic field of the rotor's permanent magnets. The rotational speed of the rotor is controlled by the speed at which the coils through which current is sequentially passed are switched.

[0003] In such a rotating electric machine, the rotation of the rotor, which has a permanent magnet embedded therein, generates an induced voltage in the stator coil according to the rotation speed of the rotor. This induced voltage is generated in a direction that cancels out the voltage applied from outside to the stator coil. This induced voltage tends to increase in regions where the rotor rotation speed is high. Therefore, in high rotation speed regions, the induced voltage is limited to be lower than the voltage applied from outside to the stator coil, and as the rotor rotation speed increases, the output of the rotating electric machine decreases.

[0004] Rotating electric machines for vehicle operation require high torque at low rotation speeds immediately after starting, and high output at high rotation speeds. To achieve both high torque at low rotation speeds and high output at high rotation speeds, Patent Document 1 discloses a rotating electric machine that can maintain high torque at low rotation speeds while improving output at high rotation speeds. The rotating electric machine disclosed in Patent Document 1 has multiple spaces extending axially inside the rotor, and is equipped with a partition member that separates the magnetic fluid and non-magnetic fluid contained in these spaces. The partition member can move axially due to the difference in pressure between the magnetic fluid and the non-magnetic fluid. In the rotating electric machine disclosed in Patent Document 1, pressure is applied from the non-magnetic fluid side to the magnetic fluid side at low rotation speeds, filling the spaces in the rotor with the non-magnetic fluid and preventing the formation of a short-circuit magnetic path within the rotor. Then, pressure is applied from the magnetic fluid side to the non-magnetic fluid side at high rotation speeds, filling the spaces in the rotor with the magnetic fluid, forming a short-circuit magnetic path within the rotor, and reducing induced voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-288183 Summary of the Invention [Problem to be solved by the invention]

[0006] The rotating electric machine disclosed in Patent Document 1 requires the control of two types of fluid, a magnetic fluid and a non-magnetic fluid, in order to maintain high torque at low rotation speeds while improving output at high rotation speeds, and also requires the installation of a movable partition plate in the space within the rotor, resulting in a complex structure.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotating electric machine that has a simple structure, does not use a non-magnetic fluid, and is capable of improving output at high rotation speeds while maintaining high torque at low rotation speeds. [Means for solving the problem]

[0008] The rotating electric machine of the present invention is a rotating electric machine equipped with a stator core having a substantially annular yoke and a plurality of teeth extending radially from the yoke, wherein a flow path for magnetic fluid is provided inside the teeth, and when the rotational speed of the rotor is below a predetermined value, the magnetic fluid is circulated through the flow path, and when the rotational speed of the rotor is higher than the predetermined value, the magnetic fluid is extracted from the flow path. [Effects of the Invention]

[0009] The present invention can provide a rotating electric machine that has a simple structure, does not use a non-magnetic fluid, and can improve output at high rotation speeds while maintaining high torque at low rotation speeds. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a cross section including a rotating shaft of a rotating electric machine according to an embodiment of the present disclosure. [Figure 2] 3 is a flowchart showing an example of a control routine executed by the control device for a rotating electrical machine according to the present embodiment. [Figure 3] 4 is a graph showing the results of an analysis of the relationship between the rotation speed and output of the rotating electric machine of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A rotating electric machine 10 according to an embodiment of the present disclosure will be described below with reference to Figures 1 to 3. Figure 1 is a cross-sectional view showing a cross section including the rotating shaft of the rotating electric machine 10 according to this embodiment. As shown in Figure 1, the rotating electric machine 10 includes a stator 1, a rotor 2 arranged coaxially with a gap provided radially inside the stator 1, and a shaft 3 that serves as the rotating shaft of the rotor 2. The rotor 2 includes a substantially cylindrical rotor core 21 through whose center the shaft 3 passes in the axial direction, and a plurality of permanent magnets 22 embedded near the outer circumferential surface of the rotor core 21.

[0012] The stator 1 includes a stator core 11 and coils 12. The stator core 11 includes a substantially annular yoke 11a and a plurality of teeth 11b extending radially inward from the yoke 11a. The teeth 11b are arranged at intervals along the circumferential direction on the inner peripheral surface of the yoke 11a. The coils 12 are wound around the teeth 11b.

[0013] A flow path 11c penetrating in the axial direction is provided at the tip of each tooth 11b on the radially inner side. Both ends of the flow path 11c are connected to the pump 6 by piping 5. The pump 6 can circulate the magnetic fluid through the flow path 11c provided inside the teeth 11b. When the pump 6 circulates the magnetic fluid, the magnetic fluid continues to flow in one direction inside the flow path 11c from one axial end to the other end of the flow path 11c. The pump 6 can also completely remove the magnetic fluid from the flow path 11c provided inside the teeth 11b and store it in a tank (not shown). When the magnetic fluid is completely removed from the flow path 11c in this way, the flow path 11c contains only air.

[0014] The pump 6 is controlled by a control device of the rotating electric machine 10. The control device of the rotating electric machine 10 has a CPU, which is an arithmetic processing unit, and storage units such as RAM and ROM, and controls the rotating electric machine 10 and the pump 6 by performing signal processing in accordance with a program pre-stored in the ROM while utilizing the temporary storage function of the RAM. Fig. 2 is a flowchart showing a control routine of the control device of the rotating electric machine 10. The program of the control routine shown in Fig. 2 is held in the ROM of the control device of the rotating electric machine 10, and is repeatedly executed at an extremely short cycle time of, for example, about several msec.

[0015] 2, the control device of the rotating electric machine 10 first monitors the rotation speed of the rotor 2 and determines whether it is equal to or less than a predetermined value in step S1. If the rotation speed of the rotor 2 is equal to or less than the predetermined value, the process proceeds from step S1 to step S2, where the control device of the rotating electric machine 10 causes the magnetic fluid to flow through the flow path 11c. If the rotation speed of the rotor 2 is higher than the predetermined value, the process proceeds from step S1 to step S3, where the control device of the rotating electric machine 10 extracts the magnetic fluid from the flow path 11c and stores it in a tank.

[0016] When the rotating electric machine 10 is used as a motor for driving a vehicle, high torque is required at low rotation speeds immediately after starting, and high output is required at high rotation speeds. The rotating electric machine 10 is controlled by the control routine shown in Fig. 2, and causes the magnetic fluid to flow through the flow path 11c when the rotation speed of the rotor 2 is low, that is, below a predetermined value. By causing the magnetic fluid to flow through the flow path 11c in this way when the rotation speed of the rotor 2 is low, that is, below a predetermined value, the rotating electric machine 10 can reduce the magnetic resistance of the stator core 11 and increase the magnetic flux density compared to a state in which the magnetic fluid is drained from the flow path 11c, thereby achieving high torque at low rotation speeds.

[0017] 3 is a graph showing the results of an analysis of the relationship between the rotational speed and output of the rotating electric machine 10. In FIG. 3, the solid line indicates the output when controlled using the control routine shown in FIG. 2, and the dashed line indicates the output when the magnetic fluid continues to flow through the flow path 11c even after the rotational speed of the rotor 2 exceeds a predetermined value. If the magnetic fluid continues to flow through the flow path 11c even after the rotational speed of the rotor 2 exceeds the predetermined value, the induced voltage increases as the rotational speed of the rotor 2 increases. Therefore, in a high rotation range where the rotational speed of the rotor 2 is higher than the predetermined value, the induced voltage is limited to be lower than the voltage applied from outside to the coil 12 of the stator 1, and as shown by the dashed line in FIG. 3, the output of the rotating electric machine 10 decreases as the rotational speed of the rotor 2 increases.

[0018] The rotating electric machine 10 is controlled by the control routine shown in Fig. 2, and the magnetic fluid is extracted from the flow path 11c when the rotational speed of the rotor 2 is higher than a predetermined value. By extracting the magnetic fluid from the flow path 11c when the rotational speed of the rotor 2 is higher than a predetermined value, the rotating electric machine 10 can increase the magnetic resistance of the stator 1 and reduce the induced voltage compared to when the magnetic fluid is circulated through the flow path 11c, thereby achieving a high output, as shown by the solid line in Fig. 3. For example, when the rotational speed of the rotor 2 is 1000 rpm, the output of the rotating electric machine 10 can be improved by 4% by extracting the magnetic fluid from the flow path 11c compared to when the magnetic fluid is circulated through the flow path 11c.

[0019] In this way, the rotating electric machine 10 circulates the magnetic fluid through the flow path 11c at low rotation speeds and extracts the magnetic fluid from the flow path 11c at high rotation speeds, thereby switching the magnetic resistance of the stator core 11 and improving the output at high rotation speeds while maintaining high torque at low rotation speeds. Furthermore, unlike the rotating electric machine disclosed in Patent Document 1, the rotating electric machine 10 does not use a non-magnetic fluid and does not require a movable partition plate, resulting in a simpler structure than the rotating electric machine disclosed in Patent Document 1.

[0020] Furthermore, when the rotation speed of the rotor 2 is low, that is, equal to or less than a predetermined value, the rotating electric machine 10 circulates the magnetic fluid between the flow path 11c and the pump 6. Therefore, by providing an external cooling device for the magnetic fluid, the rotating electric machine 10 can cool the stator 1 by circulating the cooled magnetic fluid through the flow path 11c.

[0021] <Supplementary information on the embodiment> The rotating electric machine of the present disclosure is not limited to the above-described embodiment, and various embodiments can be made within the scope of the present disclosure. For example, the flow path 11c for the magnetic fluid may be provided at a position radially outward from the tip end of the teeth 11b, rather than at the radially inner tip end of the teeth 11b. [Explanation of symbols]

[0022] 1 stator, 2 rotor, 3 shaft, 5 piping, 6 pump, 10 rotating electric machine, 11 stator core, 11a yoke, 11b teeth, 11c flow path, 12 coil, 21 rotor core, 22 permanent magnet.

Claims

[Claim 1] A rotating electric machine including a stator core having a substantially annular yoke and a plurality of teeth extending radially from the yoke, A flow path for magnetic fluid is provided inside the teeth, When the rotation speed of the rotor is equal to or lower than a predetermined value, the magnetic fluid is caused to flow through the flow path; When the rotation speed of the rotor is higher than the predetermined value, the magnetic fluid is extracted from the flow path.

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