Rotary position sensor with buffer
View Patent ↗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.
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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field which buffer zone is at least 0.5 times the largest dimension of the magnet;
a housing enclosing the buffer zone, magnet and sensor and having at least one wall and the housing prohibiting a foreign object from passing into the buffer zone; and
wherein the buffer zone includes a material surrounding at least a portion of the magnet to attenuate the magnetic field present outside of the housing.
2. The assembly of claim 1 wherein the buffer zone includes an air gap.
3. 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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field which buffer zone is at least 0.5 times the largest dimension of the magnet;
a housing enclosing the buffer zone, magnet and sensor and having at least one wall and the housing prohibiting a foreign object from passing into the buffer zone; and
wherein the buffer zone and the housing reduces the magnetic field outside of the housing to the point that a foreign ferromagnetic object outside of the housing and weighing at least 0.05 g is not held against the housing by only the magnetic field.
4. The assembly of claim 3 wherein the at least one wall of the housing is of metal or plastic material.
5. The assembly of claim 3 wherein the buffer zone includes an air gap and a material barrier.
6. The assembly of claim 3 wherein the at least one wall of the housing includes a plurality of walls collectively surrounding the buffer zone, magnet and the sensor.
7. The assembly of claim 3 wherein the buffer zone surrounding the magnet and the sensor and in which an object cannot pass is 0.5 to 1.5 times the largest dimension of the magnet.
8. 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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field which buffer zone is at least 0.5 times the largest dimension of the magnet;
a housing enclosing the buffer zone, magnet and sensor and having at least one wall and the housing prohibiting a foreign object from passing into the buffer zone; and
wherein the magnetic field strength at the exterior of the housing surrounding the buffer zone is between about 2% and 6% of the maximum magnetic field strength of the magnet at any given time.
9. 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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field which buffer zone is at least 0.5 times the largest dimension of the magnet;
a housing enclosing the buffer zone, magnet and sensor and having at least one wall and the housing prohibiting a foreign object from passing into the buffer zone; and
wherein a variation in a signal provided by a magnetic sensor caused by a foreign ferromagnetic object outside of the housing of the buffer zone is not greater than 3%.
10. 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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field that may be caused by any objects outside of the buffer zone that are not part of the fluid flow control device;
the buffer zone is at least 0.5 times the largest dimension of the magnet;
a buffer housing enclosing the buffer zone, magnet and sensor and having at least one wall, and the buffer housing prohibiting a foreign object from passing into the buffer zone; and
wherein the buffer zone includes a material surrounding at least a portion of the magnet and the sensor to attenuate the magnetic field present outside of the buffer zone.
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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field that may be caused by any objects outside of the buffer zone that are not part of the fluid flow control device;
the buffer zone is at least 0.5 times the largest dimension of the magnet;
a buffer housing enclosing the buffer zone, magnet and sensor and having at least one wall, and the buffer housing prohibiting a foreign object from passing into the buffer zone; and
wherein the buffer zone and buffer housing reduces the magnetic field outside of the buffer housing to the point that a foreign ferromagnetic object outside of the buffer housing and weighing at least 0.05 g is not held against the buffer housing by only the magnetic field.
12. The device of claim 11 wherein the buffer zone includes an air gap.
13. The device of claim 11 wherein the least one wall of the buffer housing includes a wall of metal or plastic material.
14. The device of claim 11 wherein the buffer zone includes an air gap and a material barrier.
15. The device of claim 11 wherein the at least one wall of the buffer housing includes a plurality of walls collectively surrounding the magnet and the sensor.
16. The device of claim 11 wherein the buffer zone is at least 0.5 to 1.5 times the largest dimension of the magnet.
17. The device of claim 11 wherein a variation in a signal provided by a magnetic sensor caused by an object outside of the buffer housing is not greater than 3%.
18. 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;
a buffer zone around the magnet and the sensor to limit distortion of the magnetic field that may be caused by any objects outside of the buffer zone that are not part of the fluid flow control device;
the buffer zone is at least 0.5 times the largest dimension of the magnet;
a buffer housing enclosing the buffer zone, magnet and sensor and having at least one wall, and the buffer housing prohibiting a foreign object from passing into the buffer zone; and
wherein the magnetic field strength at the exterior of the buffer housing is not greater than 6% of the maximum magnetic field strength of the magnet at any given time.