Rotating electric machine having a magnetic sensor that detects a rotation position of a rotor core
A rotating electric machine has a semiconductor magnetic sensor and a cylindrical housing with a cylinder part, which is made of a soft magnetic material, positioned closer to the semiconductor magnetic sensor relative to a back yoke of a stator core. The semiconductor magnetic sensor is positioned away from the cylindrical housing so that a shortest distance between a center of the semiconductor magnetic sensor and the cylindrical housing is equal to or greater than 50 times of a sum of a first space distance and a second space distance. With such an arrangement, a leak magnetic field generated by magnetic poles that leaks in an axial direction is prevented from disturbing the semiconductor magnetic sensor. Thus, a rotation position detection accuracy of the semiconductor magnetic sensor is improved.
1. A rotating electric machine comprising:
a rotation shaft;
a rotor core fixed on the rotation shaft;
a plurality of magnetic poles extending radially outward from the rotor core;
a plurality of soft magnetic poles extending radially outward from the rotor core at positions between the plurality of magnetic poles;
a plurality of teeth extending radially inward to face the plurality of magnetic poles and the plurality of soft magnetic poles;
a cylindrical back yoke connected to each of radial outside ends of the plurality of teeth;
a first housing fixing the cylindrical back yoke relative to the rotation shaft;
a stator conductor positioned between each of the plurality of teeth;
a detection magnet fixed on one end of the rotation shaft and generating a magnetic field to indicate a rotation position of the rotor core; and
a magnetic sensor facing the detection magnet, detecting the magnetic field, and outputting a signal according to the magnetic field as the rotation shaft rotates, wherein
when (i) a radial distance of a space between magnetic poles and the plurality of teeth is designated as a first space distance, (ii) a radial distance of a space between soft magnetic poles and the plurality of teeth is designated as a second space distance, and (iii) a consequential component is positioned a shortest distance from a center of the magnetic sensor, and the consequential component is defined as one of the cylindrical back yoke or the first housing,
the shortest distance between the center of the magnetic sensor and the consequential component is equal to or greater than 50 times of a sum of the first space distance and the second space distance.
2. The rotating electric machine of claim 1 , further comprising:
a second housing supporting the rotation shaft at a position between the rotor core and the magnetic sensor; and
a third housing supporting the rotation shaft at an opposite position that is opposite to the second housing relative to the rotor core, wherein
the first housing has a cylindrical shape and houses the cylindrical back yoke, and
the second housing is made of a non-magnetic material.
3. The rotating electric machine of claim 2 , wherein
the consequential component is the first housing.
4. The rotating electric machine of claim 1 , wherein
the magnetic sensor includes a magneto-resistive element.
5. The rotating electric machine of claim 1 , further comprising:
a projection of the magnetic pole projecting from the rotor core in the radial direction and having a magnet accommodation hole; and
a magnetic pole magnet that is accommodated in the magnet accommodation hole.
6. The rotating electric machine of claim 1 , further comprising:
a bearing supporting the rotation shaft at a position between the rotor core and the detection magnet, wherein
an axial direction interspace between the bearing and the magnetic sensor is greater than an axial direction interspace between the bearing and the rotor core.
7. The rotating electric machine of claim 6 , wherein the axial direction interspace between the bearing and the magnetic sensor is equal to or greater than 1.5 times the axial direction interspace between the bearing and the rotor core.
8. The rotating electric machine of claim 1 , wherein
the rotating electric machine is used in a vehicle electric power steering device.
9. The rotating electric machine of claim 1 , wherein the consequential component includes a component located at a nearest position to the center of the magnetic sensor from one of the cylindrical back yoke or the first housing.
10. The rotating electric machine of claim 1 , wherein the first space distance is a shortest distance in a radial direction defining of a space between the plurality of magnetic poles and the plurality of teeth.
11. The rotating electric machine of claim 1 , wherein the second space distance is a shortest distance in the radial direction defining a space between the plurality of soft magnetic poles and the plurality of teeth.
12. The rotating electric machine of claim 1 , wherein (i) the first space distance is a radial distance of a space between magnetic poles extending radially outward from the rotor core and the plurality of teeth located in a stator core, (ii) the second space distance is a radial distance of a space between soft magnetic poles extending radially outward from the rotor core and the plurality of teeth located in the stator, and (iii) the consequential component is positioned at the shortest distance from the center of the magnetic sensor to one of the cylindrical back yoke or the first housing.
13. The rotating electric machine of claim 1 , wherein first space distance is 0.6 mm, the second space distance is 0.6 mm, and the shortest distance from the center of the magnetic sensor to the consequential component is equal to or greater than 60 mm.
14. The rotating electric machine of claim 1 , wherein first space distance is 0.8 mm, the second space distance is 0.5 mm, and the shortest distance from the center of the magnetic sensor to the consequential component is equal to or greater than 65 mm.