Magnetic sensor unit less responsive to leaking magnetic flux

• US 7,019,516 B2
• Filed: 06/11/2003
• Issued: 03/28/2006
• Est. Priority Date: 06/26/2002
• Status: Expired due to Term

• Current Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Takeda, Kenji, Kamiya, Tomomitsu, Tokunaga, Masao
• Primary Examiner(s): Ledynh, Bot
• Assistant Examiner(s): Schindler, David M
• Application Number:
  US10/458,661
• Publication Number:
  US 20040000902A1
• Time in Patent Office: 1,021 Days
• Field of Search: 324/207.25, 324/207.2, 324/207.21, 324/207.22, 310/46, 310/103, 310/152, 310/156.01, 310/154.01, 310/68.B, 310/156.06
• US Class Current: 324/207.25
• CPC Class Codes: G01D 2205/77 Specific profiles
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A magnetic sensor unit includes an actuator motor and a magnetic position sensor. The actuator motor has a magnetic circuit including motor magnets. The magnetic position sensor includes a sensor magnet and a hall element for detecting magnetic flux. Magnet clearances are formed between the motor magnets. The hall element is disposed outside of the motor to detect the magnetic flux in a direction penetrating through the magnet clearances, and which is perpendicular to a direction from one of the motor magnets to the other. In this disposition of the hall element, it is restricted that the hall element detects leaking magnetic flux from the motor magnets.

Claims

1. A magnetic sensor unit unit comprising:

an actuator motor having a magnetic circuit; and

a magnetic position sensor for magnetically detecting a rotational position of the actuator motor, the magnetic position sensor including;

a magnetic flux detecting means; and

a magnetic flux generating means, which is movable with the actuator motor and generates a predetermined amount of magnetic flux toward the magnetic flux detecting means in accordance with the rotational position of the actuator motor,

wherein the magnetic flux detecting means is disposed in a position and a direction outside of the magnetic circuit, where the magnetic flux detecting means is substantially unresponsive to leaking magnetic flux of the magnetic circuit, wherein;

the magnetic circuit includes two motor magnets, wherein the motor magnets are disposed apart, and opposed surfaces of the motor magnets are magnetized in different magnetic poles; and

the magnetic detecting means is disposed to detect the magnetic flux, wherein a direction of the magnetic flux detecting means to detect the magnetic flux penetrates through magnet clearances between the motor magnets and is perpendicular to a direction from one of the motor magnets to the other.

3. A magnetic sensor unit according to claim 1 wherein the magnetic flux generating means includes a sensor magnet made of a permanent magnet, one magnetic surface of which is opposed to the magnetic flux detecting means and generates the magnetic flux whereto.

2. A magnetic sensor unit comprising:

an actuator motor having a magnetic circuit; and

a magnetic position sensor for magnetically detecting a rotational position of the actuator motor, the magnetic position sensor including;

a magnetic flux detecting means; and

a magnetic flux generating means, which is movable with the actuator motor and generates a predetermined amount of magnetic flux toward the magnetic flux detecting means in accordance with the rotational position of the actuator motor,

wherein the magnetic flux detecting means is disposed in a position and a direction outside of the magnetic circuit, where the magnetic flux detecting means is substantially unresponsive to leaking magnetic flux of the magnetic circuit,

further comprising a partitioning board, which is disposed between the magnetic circuit and the magnetic position sensor, wherein the partitioning board serves as a yoke that collects the leaking magnetic flux, whereby the magnetic flux detecting means is substantially unresponsive to the leaking magnetic flux,

wherein the partitioning board has a stepped portion facing and projecting toward the magnetic flux detecting means.

4. A magnetic sensor unit comprising:

an actuator motor having a magnetic circuit; and

a magnetic position sensor for magnetically detecting a rotational position of the actuator motor, the magnetic position sensor including;

a magnetic flux detecting means; and

a magnetic flux generating means, which is movable with the actuator motor and generates a predetermined amount of magnetic flux toward the magnetic flux detecting means in accordance with the rotational position of the actuator motor,

wherein the magnetic flux detecting means is disposed in a position and a direction outside of the magnetic circuit, where the magnetic flux detecting means is substantially unresponsive to leaking magnetic flux of the magnetic circuit,

wherein the magnetic flux generating means includes a sensor magnet made of a permanent magnet, one magnetic surface of which is opposed to the magnetic flux detecting means and generates the magnetic flux whereto, wherein;

the sensor magnet is a sloped arc-shaped magnet unit essentially composed of two sloped arc-shaped magnet portions;

the arc-shaped magnet portions have substantially same shapes and same magnetic forces;

one of the arc-shaped magnet portions is magnetized in a magnetic detecting direction of the magnetic flux detecting means, and the other is magnetized in a direction contrary to the magnetic detecting direction;

each of the sloped arc-shaped magnet portions has a sloped magnetic surface in opposition to the magnetic flux detecting means and tapers in one circumferential direction; and

thinnest circumferential ends of the arc-shaped magnet portions are integrated and form a thinnest part of the arc-shaped magnet unit.

5. A magnetic sensor unit comprising:

a motor having first magnet means for generating first magnetic flux to rotate a motor shaft;

second magnet means, coupled to the motor shaft to be rotated by the motor and disposed radially outside the motor, for generating second magnetic flux;

magnetic flux detecting means, disposed between the motor and the second magnet means, for detecting the second magnetic flux applied from the second magnet means to thereby detect a rotational position of the motor shaft; and

a magnetic shield plate, disposed between the motor and the magnetic flux detecting means, for providing a magnetic circuit of leaking magnetic flux of the first magnet means so that the magnetic flux detecting means is responsive to the second magnetic flux and substantially unresponsive to the leaking magnetic flux of the first magnet means of the motor.

6. A magnetic sensor unit according to claim 5, wherein the magnetic shield plate has a step raised toward the magnetic flux detecting means.

7. A magnetic sensor unit according to claim 5, wherein the second magnet means is arc-shaped to rotate around an axis perpendicular to the motor shaft and has a varying thickness in a circumferential direction thereby to vary the second magnetic flux applied to the magnetic flux detecting means in accordance with the rotational position of the motor shaft.