JP6071850B2 - Electric motor - Google Patents

Description

  The present invention relates to an electric motor including a rotor that is fielded by a magnetic field generator disposed on a stator side.

  A conventional rotor field motor (see, for example, Patent Document 1) includes a rotor formed by twisting salient poles, which are N poles and S poles, into each of two stacked magnetic bodies by a half pitch, and a magnetic body. A magnetic field generated in the rotor by the magnetic field generator including a stator in which salient pole-shaped teeth are formed and wound with a coil and a magnetic field generator (permanent magnet or electromagnet) disposed on the stator. The rotor is rotated by the interaction with the rotating magnetic field generated in the stator teeth by switching the energization of the coil.

In such an electric motor, the performance is mainly determined by the following (1) to (3).
(1) Air gap between stator and rotor (2) Strength of magnetic field generated by current flowing through stator coil (field strength on stator side)
(2-1) Number of coil turns (number of turns)
(2-2) Strength of current applied to coil (2-3) Cross sectional area of stator teeth, etc. (3) Strength of magnetic field passing through rotor (field strength on rotor side)
(3-1) Magnetic field strength of the magnetic field generator disposed on the stator side (3-2) Cross-sectional area of the rotor salient pole (3-3) Shaft material, etc.

  Regarding the above (3-3), the shaft material is conventionally selected in consideration of the motor performance and mechanical strength, and a magnetic material (for example, an iron-based material) is selected. There was a concern that a part of the field magnetic flux leaked from the shaft (see, for example, Patent Document 2), and the performance deteriorated.

On the other hand, in order to control the electric motor, it is necessary to sense the rotational speed, rotational acceleration, rotational position, etc. of the shaft, and sensing is performed using a rotation sensor that detects the contact angle by replacing the rotation angle of the object with a magnetic force change. The method is general (see, for example, Patent Document 3). In Patent Document 3, using a permanent magnet (sensor target) that rotates integrally with the shaft, and a rotation sensor that is installed on the stator side and detects a magnetic flux that changes according to the rotational position of the permanent magnet, Sensing.
Alternatively, if the rotation sensor is a permanent magnet integrated type unlike the above, a magnetic material is used for the sensor target on the shaft side, and a permanent magnet and a rotation sensor are installed on the stator side so that the rotation position of the sensor target is The rotation sensor detects the magnetic flux of the permanent magnet that changes accordingly.

JP-A-8-214519 JP 2004-222418 A Special table 2012-503464 gazette

  Since the conventional electric motor is configured as described above, there is a problem in that when leakage magnetic flux from the shaft is generated, the leakage magnetic flux affects the sensing of the rotation sensor and a detection error occurs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the influence of the leakage magnetic flux of the shaft on the sensing of the rotation sensor in the rotor field type electric motor.

  An electric motor according to the present invention includes a magnetic shaft, a rotor that rotates integrally with the shaft, a stator that is wound with a coil to generate a rotating magnetic field when energized, and is installed in the stator to magnetize the rotor. A magnetic field generator, a sleeve that covers the tip of the shaft and shields leakage magnetic flux that flows from the magnetic field generator to the shaft, a sensor target that is fixed to the tip of the shaft with the sleeve interposed therebetween, and a periphery of the sensor target And a rotation sensor that detects a magnetic flux that changes according to a sensor target that rotates integrally with the shaft.

  According to this invention, since the magnetic flux leaking from the magnetic field generator through the shaft to the rotation sensor is shielded by the sleeve covering the shaft tip, the influence of the leakage magnetic flux on the rotation sensor can be reduced, The detection error of the rotation sensor can be easily reduced.

It is sectional drawing which shows the structure of the electric motor which concerns on Embodiment 1 of this invention. It is sectional drawing to which the rotation sensor and sensor target structure of FIG. 1 were expanded. FIG. 3A is a top view and FIG. 3B is a bottom view showing a sensor target structure. FIG. 3 is a reference diagram for helping understanding of the sensor target structure of the first embodiment. It is sectional drawing to which the rotation sensor used for the electric motor which concerns on Embodiment 2 of this invention, and a sensor target structure was expanded. FIG. 6 is a reference diagram for helping understanding of the sensor target structure of the second embodiment.

Embodiment 1 FIG.
An electric motor shown in FIG. 1 includes a magnetic shaft 3, two bearings 4 that rotatably support the shaft 3, a rotor 5 that rotates integrally with the shaft 3, and a coil inside the housings 1 and 2. 6 is wound around the stators 7 and 8 which generate a rotating magnetic field when energized, a field magnet (magnetic field generator) 9 which is installed between the stators 7 and 8 and magnetizes the shaft 3, A rotation sensor 20 that determines the rotational position, a bus bar 10 that energizes the coil 6, and a control board 11 that controls energization from the bus bar 10 to the coil 6 based on the rotational position of the shaft 3 are provided. In the example of FIG. 1, a housing 1 that accommodates the rotor 5, the stators 7 and 8, the field magnet 9, one bearing 4, and the like, and a housing 2 that accommodates the other bearing 4, It may be fixed with screws or the like.

  The rotor 5 made of a magnetic material is formed with two protrusions protruding outward in the circumferential direction at intervals of 180 degrees, and the protrusions are shifted by 90 degrees in the middle of the rotation axis direction X (protrusion 5a). , 5b). By fixing the shaft 3 to the rotor 5 and rotating the shaft 3 integrally with the rotor 5, the rotational force generated in the rotor 5 is externally output. When the electric motor is applied to an automobile turbocharger, an electric compressor, or the like, the shaft 3 is connected to a rotating shaft of a turbine (so-called impeller), and the turbine is driven to rotate by the electric motor.

The stators 7 and 8 made of a magnetic material are formed with a plurality of teeth 7 a and 8 a protruding inward in the circumferential direction, and the coil 6 is wound in the rotation axis direction X. A field magnet 9 for magnetizing the rotor 5 is installed between the stators 7 and 8.
In FIG. 1, the field magnet 9 is used as a magnetic field generating unit that fields the rotor 5, but an electromagnet may be used.

  The bus bar 10 is composed of a resin member that integrally molds a copper plate coil 10a. One end of the coil 10a is electrically connected to the coil 6 of the stators 7 and 8, and the other end is electrically connected to the control board 11. The control board 11 converts an external power source (not shown) into an AC power source, and sequentially switches the phase of the coil 10a (for example, three phases of U phase, V phase, and W phase) based on the output of the rotation sensor 20, while the coil 6 Current to

  A magnetic flux (rotor field magnetic field A shown in FIG. 1) by the field magnet 9 magnetized in the rotation axis direction X is projected from the stator 8 disposed on the N pole side of the field magnet 9 to the rotor 5. The field magnetic flux that flows out to the part 5b, advances in the rotor 5 in the rotation axis direction X, exits from the protrusion 5a on the S pole side, and flows into the stator 7 disposed on the S pole side of the rotor 5 Become. Thus, the field magnetomotive force of the field magnet 9 acts on the rotor 5, so that the protrusion 5 b of the rotor 5 facing the N pole side of the field magnet 9 is magnetized to the N pole. The protrusion 5a facing the S pole side of the magnet 9 is magnetized to the S pole. When a current flows through the coil 6 via the coil 10a of the bus bar 10, the teeth 7a and 8a of the stators 7 and 8 are magnetized according to the direction of the flowing current to generate a rotating magnetic field and generate torque. . By switching the direction of the current flowing through the coil 6 under the control of the control board 11, the NS polarities of the teeth 7a and 8a are rotated and the rotor 5 is rotated by the magnetic action.

  As previously described, the magnetic material is adopted for the shaft 3 in consideration of the performance and mechanical strength of the electric motor. However, if the shaft 3 is made of a magnetic material, the field magnet 9, the stator 8, the rotor 5, and part of the rotor field magnetic field A flowing through the field magnet 9 leak to the shaft 3, and the direction of the rotation sensor 20 Leakage magnetic flux B toward is generated.

Next, details of the rotation sensor 20 and the sensor target structure 21 will be described.
FIG. 2 is an enlarged cross-sectional view of the rotation sensor 20 and the sensor target structure 21.
The rotation sensor 20 is configured by an IC (Integrated Circuit) chip or the like that incorporates a Hall element or a magnetoresistive element, and is mounted on the control board 11 installed near the end of the shaft 3. On the other hand, a sensor target structure 21 having a sensor target 22 is fixed to the end of the shaft 3 facing the rotation sensor 20. The rotation sensor 20 detects a change in the sensor magnetic field C accompanying the rotation of the shaft 3 and determines the rotation position of the shaft 3.

  The sensor target structure 21 includes a sensor target 22 for generating a sensor magnetic field C, an insert nut 23 made of brass or the like, a sleeve 24 made of a magnetic material, and a molded part 25 made of a resin member integrally formed with these. It consists of and. The sensor target structure 21 is fixed to the shaft 3 by providing the male screw portion 3 a at the tip of the shaft 3 and screwing the insert nut 23.

FIG. 3A shows a top view of the sensor target structure 21 viewed from the control board 11 side, and FIG. 3B shows a bottom view of the sensor target structure 21 viewed from the shaft 3 side.
Since the sensor target structure 21 is directly screwed to the shaft 3 via the insert nut 23, it can be easily attached, and heat resistance and vibration resistance are improved.

  Further, when the sensor target structure 21 is fastened, two receiving surfaces 24a that are parallel to each other are formed to receive the stress from the tightening tool 30 so that the screw can be tightened using a tightening tool 30 such as a hexagon wrench. Thereby, it can prevent that the mold part 25 receives the stress of screw fastening and is damaged. In the example of FIG. 3, the outer shape of the sleeve 24 is a hexagonal surface, and three sets of two receiving surfaces 24a that are parallel to each other are provided.

  Further, in order to prevent the shaft 3 and the mold part 25 from being caught, the sleeve 24 is provided with a contact stop surface 24b for stopping the front end surface of the shaft 3. A resin member is not molded on the contact stop surface 24b, and the outer surface of the sleeve 24 is exposed. Further, in order to ensure the flow of the resin member during integral molding, the sleeve 24 is provided with one or more holes 24c.

  In the first embodiment, the sensor target structure 21 is attached to the tip of the shaft 3 so that the sleeve 24 made of a magnetic material wraps around the tip of the shaft 3 and blocks the leakage magnetic flux B from the shaft 3. Therefore, the influence of the leakage magnetic flux B on the sensor magnetic field C can be eliminated, and the detection error of the rotation sensor 20 can be reduced.

On the other hand, FIGS. 4A and 4B are reference views for helping understanding of the sensor target structure 21 of the first embodiment.
In the sensor target structure 100 shown in FIG. 4A, a permanent magnet sensor target 101 is bonded to the tip surface of the shaft 3. In the sensor target structure 110 shown in FIG. 4B, a permanent magnet sensor target 112 is press-fitted into a recess 111 provided on the tip surface of the shaft 3. In any configuration, the leakage magnetic flux B from the shaft 3 affects the sensor magnetic field C and causes a detection error of the rotation sensor 20. In addition, alignment work of the sensor target 101, press-fitting work of the sensor target 112, and the like are necessary, and installation is troublesome.

  As described above, according to the first embodiment, the electric motor includes the magnetic shaft 3, the rotor 5 that rotates integrally with the shaft 3, the stator 7 that is wound with the coil 6 and generates a rotating magnetic field when energized. 8, a field magnet 9 that is installed on the stators 7 and 8 and magnetizes the rotor 5, and a sleeve 24 that covers the tip of the shaft 3 and shields the leakage magnetic flux B flowing from the field magnet 9 to the shaft 3. The permanent magnet sensor target 22 is fixed to the tip of the shaft 3 with the sleeve 24 interposed therebetween, and the sensor target 22 is installed around the sensor target 22 and rotates integrally with the shaft 3. The rotation sensor 20 for detecting the sensor magnetic field C is provided. For this reason, the influence which the leakage magnetic flux B has on the sensing of the rotation sensor 20 can be reduced, and the detection error of the rotation sensor 20 can be easily reduced.

  Further, according to the first embodiment, the shaft 3 has the male screw portion 3a at the tip, and the sleeve 24 is formed from the insert nut 23 fastened to the male screw portion 3a and the tightening tool 30 at the time of fastening. The receiving surface 24a has two parallel receiving surfaces 24a that receive the above stress. For this reason, the sleeve 24 can be screwed directly to the shaft 3 via the insert nut 23, and assemblability is improved.

Further, according to the first embodiment, since the sleeve 24 is made of a magnetic material, the magnetic flux passing through the shaft 3 toward the rotation sensor 20 can be bypassed as shown by an arrow B in FIG.
When the sleeve 24 is made of a non-magnetic material, the magnetic flux passing through the shaft 3 becomes a leakage magnetic flux, and acts as an external magnetic field to the rotation sensor 20 installed at the end of the shaft 3, leading to detection errors.

  Further, according to the first embodiment, the sleeve 24 is integrally formed with the sensor target 22 and the insert nut 23, and the sensor target structure 21 is made into one component, so that the assemblability to the shaft 3 is improved.

Embodiment 2. FIG.
In the first embodiment, the configuration example using the permanent magnet as the sensor target of the rotation sensor has been described. In the second embodiment, the configuration example using the magnetic material as the sensor target will be described. In addition, since the electric motor of Embodiment 2 is the structure similar to the electric motor shown in FIG. 1, below, FIG. 1 is used.

FIG. 5A is an enlarged cross-sectional view of the rotation sensor 20-1 and the sensor target structure 21-1 according to the second embodiment, and FIG. 5B is a plan view of the sensor target 26. 5 that are the same as or correspond to those in FIGS. 1 to 3 are denoted by the same reference numerals.
The sensor target structure 21-1 has a sensor target 26 made of a magnetic material instead of the sensor target 22 (shown in FIG. 2) made of a permanent magnet. The sensor target 26 is integrally formed with a resin member together with the insert nut 23 and the sleeve 24 to form a mold portion 25.
The other structure of the sensor target structure 21-1 is the same as that of the sensor target structure 21 of the first embodiment, and a description thereof will be omitted.

  The rotation sensor 20-1 includes an IC chip that includes a magnet 20a that generates a sensor magnetic field D passing through the sensor target 26 and a Hall element or a magnetoresistive element (not shown). In the example of FIG. 5B, the sensor target 26 is made of a substantially disk-shaped magnetic body, and the outer peripheral edge of the sensor target 26 has an uneven shape, and the sensor target 26 and the rotation sensor 20 are rotated with the rotation of the shaft 3. The sensor magnetic field D is changed by changing the distance to -1. The rotation sensor 20-1 detects a change in the sensor magnetic field D accompanying the rotation of the shaft 3 and determines the rotation position of the shaft 3.

  Also in the second embodiment, as in the first embodiment, the sensor target structure 21-1 is attached to the distal end portion of the shaft 3, so that the sleeve 24 made of a magnetic material wraps around the distal end portion of the shaft 3. Is interrupted. Therefore, the influence of the leakage magnetic flux B on the sensor magnetic field D can be eliminated, and the detection error of the rotation sensor 20-1 can be reduced.

In contrast, FIGS. 6A and 6B are reference views for helping understanding of the sensor target structure 21-1 of the second embodiment.
In the sensor target structure 120 shown in FIG. 6A, the bottomed cylindrical magnetic sensor target 121 is press-fitted into the tip portion of the shaft 3. In the sensor target structure 130 shown in FIG. 6B, a bottomed cylindrical magnetic sensor target 131 is attached to a screw hole 132 provided on the tip surface of the shaft 3 using a screw 133. In any configuration, the leakage magnetic flux B from the shaft 3 passes through the sensor targets 121 and 131 and affects the sensor magnetic field D, causing a detection error of the rotation sensor 20. Further, since the sensor target 121 is press-fitted or the sensor target 131 and the screw 133 are individually attached, it takes time and effort.

  As described above, according to the second embodiment, even in the case of the rotation sensor 20-1 using the magnetic sensor target 26, the leakage flowing from the field magnet 9 to the shaft 3 covering the tip of the shaft 3. By using the sleeve 24 that shields the magnetic flux B, the influence of the leakage magnetic flux B on the sensing of the rotation sensor 20-1 can be reduced, and the detection error of the rotation sensor 20-1 can be easily reduced.

  In the present invention, within the scope of the invention, any combination of each embodiment, any component of each embodiment can be modified, or any component can be omitted in each embodiment. .

  1, 2 Housing, 3 Shaft, 3a Male thread, 4 Bearing, 5 Rotor, 5a, 5b Protrusion, 6 Coil, 7, 8 Stator, 7a, 8a Teeth, 9 Field magnet (magnetic field generator), 10 bus bar, 10a coil, 11 control board, 12 bands, 20, 20-1 rotation sensor, 20a magnet, 21, 21-1 sensor target structure, 22 sensor target (permanent magnet), 23 insert nut, 24 sleeve, 24a Surface, 24b contact stop surface, 24c hole, 25 mold part, 26 sensor target (magnetic material), 30 clamping tool, 100, 110, 120, 130 sensor target structure, 101, 112 sensor target (permanent magnet), 111 recess 121, 131 Sensor target (magnetic material), 132 Di holes 133 screws.

Claims (4)

A magnetic shaft,
A rotor that rotates integrally with the shaft;
A stator in which a coil is wound and a rotating magnetic field is generated by energization;
A magnetic field generator installed on the stator and magnetizing the rotor;
A sleeve that covers the tip of the shaft and shields leakage magnetic flux that flows from the magnetic field generator to the shaft;
A sensor target fixed to the tip of the shaft with the sleeve interposed therebetween;
An electric motor provided with a rotation sensor that is installed around the sensor target and detects a magnetic flux that changes according to the sensor target that rotates together with the shaft. The shaft has a male screw portion at the tip,
The sleeve has an insert nut fastened to the male threaded portion, and two outer surfaces that are parallel to each other for receiving stress from a tightening tool at the time of fastening are provided. 1. The electric motor according to 1.   3. The electric motor according to claim 1, wherein the sleeve is made of a magnetic material.   4. The electric motor according to claim 2, wherein the sleeve is integrally formed with the sensor target and the insert nut.

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