Electric motor system

Patent metadata

Field	Value
Publication number	US-11316403-B2
Application number	US-201716324135-A
Country	US
Kind code	B2
Filing date	Jul 13, 2017
Priority date	Aug 12, 2016
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

An electric motor system includes a rotary shaft having an axis line displaceable relative to a rotation center, a magnetic bearing for supporting the rotary shaft, a permanent magnet mounted on the rotary shaft and having a plurality of magnetic poles arranged in a circumferential direction around the axis line of the rotary shaft, three detection elements arranged in the circumferential direction around the rotation center for detecting a magnetic flux generated from the permanent magnet, and a coordinate detection section for determining coordinates of the axis line of the rotary shaft based on output values of two detection elements selected out of the three detection elements in accordance with a rotation angle of the rotary shaft.

First claim

What is claimed is:

1. An electric motor system comprising:
a rotor;
a rotary shaft provided to have an axis line thereof to be displaceable relative to a rotation center and outputting a rotational force of the rotor;
a stator for generating the rotational force on the rotor by an electromagnetic force;
a magnetic bearing for rotatably supporting the rotary shaft by an electromagnetic force;
a permanent magnet mounted on and in contact with the rotary shaft and having a plurality of magnetic poles arranged in a circumferential direction around the axis line of the rotary shaft;
three detection elements arranged in the circumferential direction around the rotation center and detecting a magnetic flux generated from the permanent magnet;
a coordinate detection section for determining coordinates of the axis line of the rotary shaft based on output values of two detection elements selected out of the three detection elements in accordance with a rotation angle of the rotary shaft; and
a control section for controlling the magnetic bearing so that the axis line of the rotary shaft is brought to be close to the rotation center based on the coordinates determined by the coordinate detection section.

2. The electric motor system according to claim 1 , wherein:
the three detection elements are arranged such that an imaginary line connecting any two detection elements among the three detection elements deviates from the rotation center.

3. The electric motor system according to claim 1 , wherein:
the three detection elements are arranged at equal angular intervals in the circumferential direction around the rotation center.

4. The electric motor system according to claim 1 , further comprising:
a rotation angle detection section for detecting a rotation angle of the rotary shaft based on the output value of one detection element among the three detection elements; and
a rotation control section for controlling the stator to generate the rotational force on the rotor based on the rotation angle detected by the rotation angle detection section.

5. The electric motor system according to claim 4 , wherein:
the rotation angle detection section detects the rotation angle of the rotary shaft by detecting an arrival of a boundary, which is between adjacent two magnetic poles among the plurality of magnetic poles of the permanent magnet, at an angle, at which the one detection element is positioned based on the output value of the one detection element.

6. The electric motor system according to claim 4 , wherein:
the coordinate detection section determines the coordinates of the axis based on the output values of the two detection elements other than the one detection element among the three detection elements; and
among the three detection elements, the detection elements used in the coordinate detection section and the detection element used in the rotation angle detection section are switched over in accordance with a rotation of the rotary shaft.

7. The electric motor system according to claim 1 , wherein:
the permanent magnet does not contact any component of the electric motor system other than the rotary shaft.

8. The electric motor system according to claim 1 , wherein:
the permanent magnet is in contact with only the rotary shaft.

9. The electric motor system according to claim 1 , wherein:
the three detection elements are spaced apart from and opposed to the permanent magnet.

Assignees

• Denso Corp

Inventors

• Tokunaga Masao
• Yasuda Masanori
• Ito Koji

Classifications

• H02K11/33

  Drive circuits, e.g. power electronics (H02K11/38 takes precedence) · CPC title

• F16C32/0446

  Determination of the actual position of the moving member, e.g. details of sensors · CPC title

• F16C32/048

  with active support of two degrees of freedom, e.g. radial magnetic bearings · CPC title

• H02K11/215

  Magnetic effect devices, e.g. Hall-effect or magneto-resistive elements · CPC title

• F16C32/0468

  of moving parts of the magnetic circuit, e.g. of the rotor · CPC title