ROTARY POSITION SENSOR WITH BUFFER

• US 20130068974A1
• Filed: 09/04/2012
• Published: 03/21/2013
• Est. Priority Date: 09/19/2011
• Status: Active Grant

• Current Assignee: Walbro LLC
• Original Assignee: Walbro Engine Management LLC (Sun Capital Partners Incorporated)
• Inventors: Galka, William E., Speirs, David L.
• Granted Patent: US 9,464,577 B2
• Time in Patent Office: Days
• US Class Current: 251/65
• CPC Class Codes: F02D 9/105 having a throttle position sensor detection of actuation F02D11/106
• CPC Class Codes: F16K 1/22 with axis of rotation crossing the valve member, e.g. butterfly valves
• CPC Class Codes: F16K 37/0033 using a permanent magnet, e.g. in combination with a reed relays
• CPC Class Codes: F16K 37/0041 for measuring valve parameters F16K37/0033 takes precedence
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A rotary position sensor for determining the rotary position of a rotary component may include a sensor and a magnet. The sensor may be responsive to a characteristic of a magnetic field that changes as the magnetic field moves. The magnet may be carried by the rotary component for rotation with the rotary component. A buffer may be provided around the magnet to limit distortion of the magnet field. The buffer is effective against objects normally located in the area of a device with which the sensor is used (e.g. adjacent components) as well as against foreign objects not normally in the area of the device.

Claims

1. A rotary position sensor assembly for determining the rotary position of a rotary component, comprising:

a magnet carried by the rotary component for rotation with the rotary component;

a sensor responsive to a characteristic of a magnetic field that changes as the magnet rotates or is rotated; and

a buffer provided around the magnet to limit distortion of the magnet field.

2. The assembly of claim 1 wherein the buffer includes an air gap.

3. The assembly of claim 1 wherein the buffer includes at least one wall of metal or plastic material.

4. The assembly of claim 1 wherein the buffer includes a material surrounding at least a portion of the magnet to attenuate the magnetic field present outside of the buffer.

5. The assembly of claim 1 wherein the buffer includes an air gap and a material barrier.

6. The assembly of claim 1 wherein buffer includes a plurality of walls surrounding the magnet.

7. The assembly of claim 1 wherein the buffer reduces the magnetic field to the point that a foreign object outside of the buffer and weighing at least 0.05 g is not held against the housing by only the magnetic field.

8. The assembly of claim 1 wherein the buffer creates a buffer zone surrounding the magnet in which an object cannot pass and the buffer zone is at least 0.5 times the largest dimension of the magnet.

9. The assembly of claim 1 wherein the magnetic field strength at the exterior of the buffer is between about 2% and 6% of the maximum magnetic field strength of the magnet at any given time.

10. The assembly of claim 9 wherein a variation in a signal provided by a magnetic sensor caused by an object outside of the buffer is not greater than 3%.

13. The device of claim 1 wherein the buffer includes at least one wall of metal or plastic material.

11. A fluid flow control device for a combustion engine, comprising:

a housing;

a throttle valve carried by the housing for rotation to vary a flow of fluid past the throttle valve;

a magnet carried by the throttle valve for rotation with the throttle valve;

a sensor responsive to a characteristic of a magnetic field that changes as the magnet rotates or is rotated; and

a buffer provided around the magnet to limit distortion of the magnet field that may be caused by objects outside of the buffer that are not part of the fluid flow control device.

12. The device of claim 11 wherein the buffer includes an air gap.

14. The device of claim 11 wherein the buffer includes a material surrounding at least a portion of the magnet to attenuate the magnetic field present outside of the buffer.

15. The device of claim 11 wherein the buffer includes an air gap and a material barrier.

16. The device of claim 11 wherein buffer includes a plurality of walls surrounding the magnet.

17. The device of claim 11 wherein the buffer reduces the magnetic field to the point that a foreign object outside of the buffer and weighing at least 0.05 g is not held against the housing by only the magnetic field.

18. The device of claim 11 wherein the buffer creates a buffer zone surrounding the magnet in which an object cannot pass and the buffer zone is at least 0.5 times the largest dimension of the magnet.

19. The device of claim 11 wherein the magnetic field strength at the exterior of the buffer is between about 2% and 6% of the maximum magnetic field strength of the magnet at any given time.

20. The device of claim 19 wherein a variation in a signal provided by a magnetic sensor caused by an object outside of the buffer is not greater than 3%.