Rotation detection sensor

• US 20090058404A1
• Filed: 08/26/2008
• Published: 03/05/2009
• Est. Priority Date: 08/30/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kurumado, Norihiro
• Granted Patent: US 8,018,224 B2
• Time in Patent Office: Days
• US Class Current: 324/207.250
• CPC Class Codes: G01D 2205/85 Determining the direction of movement of an encoder, e.g. of an incremental encoder
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 13/04 Indicating positive or negative direction of a linear movement or clockwise or anti-clockwise direction of a rotational movement

Abstract

A rotation detection sensor for detecting both rotational position and direction of a rotating body with a gear includes a magnet, multiple magnetic sensors, a rotational position detection circuit, and a rotational direction detection circuit. The magnet produces a magnetic field directed to a gear tooth of the rotating body. When the rotating body rotates, the magnetic sensors output sensor signals shifted in phase from each other. The rotational position detection circuit performs a differential operation on the sensor signals received from at least two magnetic sensors and outputs a rotational position signal. The rotational direction detection circuit outputs a rotational direction signal based on the position signal and the sensor signal received from at least one of the at least two magnetic sensors.

Claims

1. A rotation detection sensor for detecting a rotational direction of a rotating body having a gear with a tooth moving with rotation of the rotating body, the rotation detection sensor comprising:

a magnet configured to produce a magnetic field directed to the tooth of the gear, the magnetic field varying with movement of the tooth;

a plurality of magnetic sensors located between the gear and the magnet and aligned along an imaginary straight line perpendicular to a magnetic center axis of the magnet, the plurality of magnetic sensors outputting

a plurality of sensor signals shifted in phase from each other, each sensor signal having a voltage or current value that changes depending on the magnetic field;

a rotational position detection circuit configured to receive the sensor signals from at least two of the plurality of magnetic sensors, the rotational position detection circuit performing a differential operation on the received sensor signals to output a position signal indicating a rotational position of the rotating body; and

a rotational direction detection circuit configured to receive the sensor signal from at least one of the at least two magnetic sensors, the rotational direction detection circuit outputting a direction signal, indicating a rotational direction of the rotating body, based on the position signal and the received sensor signal.

2. The rotation detection sensor according to claim 1,

wherein the plurality of magnetic sensors includes a first magnetic sensor configured to output the sensor signal to each of the rotational position detection circuit and the rotational direction detection circuit,

wherein the plurality of magnetic sensors includes a second magnetic sensor configured to output the sensor signal to only the rotational direction detection circuit,

wherein each of a remainder of the plurality of magnetic sensors is configured to output the sensor signal to only the rotational position detection circuit,

wherein a distance between the first magnetic sensor and an imaginary center line is equal to or less than a distance between any one of the plurality of magnetic sensors and the imaginary center line,

wherein a distance between the second magnetic sensor and the imaginary center line is greater than the distance between the first magnetic sensor and the imaginary center line,

wherein the imaginary center line connects a rotational center of the rotating body and the imaginary straight line in the shortest distance,

wherein the rotational direction detection circuit performs a differential operation on the sensor signals received from the first and second magnetic sensors to generate a differential signal, and

wherein the rotational direction detection circuit outputs the direction signal based on the position signal and the differential signal.

3. The rotation detection sensor according to claim 2,

wherein the at least two magnetic sensors are symmetrically arranged with respect to the imaginary center line, and

wherein the distance between the second magnetic sensor and the imaginary center line is greater than a distance between any one of the at least two magnetic sensors and the imaginary center line.

4. The rotation detection sensor according to claim 1,

wherein the plurality of magnetic sensors includes a first magnetic sensor configured to output the sensor signal to each of the rotational position detection circuit and the rotational direction detection circuit,

wherein the plurality of magnetic sensors includes a second magnetic sensor configured to output the sensor signal to only the rotational direction detection circuit,

wherein each of a remainder of the plurality of magnetic sensors is configured to output the sensor signal to only the rotational position detection circuit,

wherein a distance between the first magnetic sensor and an imaginary center line is equal to or greater than a distance between any one of the plurality of magnetic sensors and the imaginary center line,

wherein a distance between the second magnetic sensor and the imaginary center line is less than the distance between the first magnetic sensor and the imaginary center line,

wherein the imaginary center line connects a rotational center of the rotating body and the imaginary straight line in the shortest distance,

wherein the rotational direction detection circuit performs a differential operation on the sensor signals received from the first and second magnetic sensors to generate a differential signal, and

wherein the rotational direction detection circuit outputs the direction signal based on the position signal and the differential signal.

5. The rotation detection sensor according to claim 4,

wherein the at least two magnetic sensors are symmetrically arranged with respect to the imaginary center line, and

wherein the distance between the second magnetic sensor and the imaginary center line is greater than a distance between any one of the at least two magnetic sensors and the imaginary center line.

6. The rotation detection sensor according to claim 1,

wherein the plurality of magnetic sensors includes a first magnetic sensor and a second magnetic sensor, each of the first and second magnetic sensors being configured to output the sensor signal to each of the rotational position detection circuit and the rotational direction detection circuit,

wherein each of a remainder of the plurality of magnetic sensors is configured to output the sensor signal to only the rotational position detection circuit,

wherein the first and second magnetic sensors are located on a same side of an imaginary center line,

wherein the imaginary center line connects a rotational center of the rotating body and the imaginary straight line in the shortest distance,

wherein the rotational direction detection circuit performs a differential operation on the sensor signals received from the first and second magnetic sensors to generate a differential signal, and

wherein the rotational direction detection circuit outputs the direction signal based on the position signal and the differential signal.

7. The rotation detection sensor according to claim 6,

wherein the at least two magnetic sensors are symmetrically arranged with respect to the imaginary center line,

wherein a distance between the first magnetic sensor and the imaginary center line is equal to or greater than a distance between any one of the at least two magnetic sensors and the imaginary center line, and

wherein the second magnetic sensor is located adjacent to the first magnetic sensor and located between the first magnetic sensor and the imaginary center line.