Rotational angle detecting device

• US 20040251896A1
• Filed: 06/07/2004
• Published: 12/16/2004
• Est. Priority Date: 06/13/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Mizutani, Akitoshi, Ban, Takao
• Granted Patent: US 7,034,525 B2
• Time in Patent Office: Days
• US Class Current: 324/207.25
• CPC Class Codes: G01D 5/142 using Hall-effect devices measuring magnetic variables using Hall-effect or other galvanomagnetic devices G01R33/06

Abstract

In a rotational angle detecting device, an auxiliary magnet is disposed so as to surround a Hall element around the Z-axis, so that variation of offset magnetic flux is suppressed even when the position of the Hall element is displaced in the X-axis direction with respect to the auxiliary magnet. In addition, even when the fabrication position of the Hall element is displaced in the Y-axis direction of the auxiliary magnet, the variation of the offset magnetic flux is suppressed. By adjusting the dimension (the length in cylinder direction) in the Z-axis direction of the auxiliary magnet, the variation of the offset magnetic flux is suppressed even when the Hall element is displaced from the center of the auxiliary magnet in the Z-axis direction. That is, even when the position of the Hall element is displaced from the center of the auxiliary magnet in the three-dimensional direction, the displacement of the offset magnetic flux can be prevented, and thus reduction of the detection precision can be prevented.

Claims

1. A rotational angle detecting device having a magnetic detection element and a main magnet for applying magnetic force to the magnetic detection element, wherein variation of the relative rotational angle between the magnetic detection element and the main magnet is detected on the basis of magnetic force applied to the magnetic detection element, comprising:

an auxiliary magnet disposed in the neighborhood of the magnetic detection element so that the relative rotational angle thereof to the magnetic detection element is not varied at all times and constant magnetic force is applied to the magnetic detection element in the magnetic detection direction, wherein the auxiliary magnet is disposed so as to surround the magnetic detection element.

2. The rotational angle detecting device according to claim 1, wherein a magnetic flux direction along which the auxiliary magnet applies magnetic flux to the magnetic detection element and a magnetic detection direction of the magnetic detection element are non-parallel to each other, and have an offset angle therebetween.

3. The rotational angle detecting device according to claim 1, wherein the main magnet and the auxiliary magnet are formed of permanent magnets having the same temperature characteristic.

4. A rotational angle detecting device having a magnetic detection element and a main magnet for applying magnetic force to the magnetic detection element, wherein variation of the relative rotational angle between the magnetic detection element and the main magnet is detected on the basis of magnetic force applied to the magnetic detection element, comprising:

an auxiliary magnet disposed in the neighborhood of the magnetic detection element so that the relative rotational angle thereof to the magnetic detection element is not varied at all times and constant magnetic force is applied to the magnetic detection element in the magnetic detection direction, wherein the auxiliary magnet is disposed at both the sides of the magnetic detection element.

5. The rotational angle detecting device according to claim 4, wherein a magnetic flux direction along which the auxiliary magnet applies magnetic flux to the magnetic detection element and a magnetic detection direction of the magnetic detection element are non-parallel to each other, and have an offset angle therebetween.

6. The rotational angle detecting device according to claim 4, wherein the main magnet and the auxiliary magnet are formed of permanent magnets having the same temperature characteristic.