Assembly for detecting more than one rotation through a position encoder magnet

• US 20110080162A1
• Filed: 08/11/2010
• Published: 04/07/2011
• Est. Priority Date: 10/06/2009
• Status: Active Grant

• Current Assignee: ASM Automation Sensorik Messtechnik GmbH
• Original Assignee: ASM Automation Sensorik Messtechnik GmbH
• Inventors: Steinich, Klaus Manfred, Wirth, Peter
• Granted Patent: US 8,847,584 B2
• Time in Patent Office: Days
• US Class Current: 324/207.25
• CPC Class Codes: B62D 15/0215 by measuring on the steering column
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 2205/26 Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation
• CPC Class Codes: G01D 2205/28 The target being driven in rotation by additional gears
• CPC Class Codes: G01D 5/04 using levers; using cams; using gearing
• 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 5/2452 incorporating two or more tracks having an (n, n+1, ...) relationship

Abstract

The rotational position of an encoder magnet can be scanned over more than 360° by respective sensor elements in that magnets are disposed on different stages of a suitable transmission, in particular of a differential transmission, and the magnets are scanned by separate sensor elements, whose signals are computed with one another and yield a total number of revolutions.

In particular, when an assembly of this type shall be built very small, undesirable magnetic interferences for the sensor elements have to be avoided through flux conductor elements since the interferences distort the measurement results. Thus, a differentiation is made between active and passive flux conductor elements.

Claims

1. An arrangement for magnets (4a . . . ) as a position encoders for detecting more than one revolution, comprising:

at least two rotatably supported magnet units (5a, b) operatively connected with respect to their rotatabilities, wherein one of the magnet units is driven in rotation and the magnet units rotate at different speeds of rotation but at a fixed speed ratio relative to one another;

an angle sensor element (12) is associated with each magnet unit (5a, b), which detects the magnetic field of the magnet unit (5a, b), wherein

at least one, in particular each magnet unit (5a, b) includes a co-rotating flux conductor element; and

each magnet unit (5a, b) supports at least one magnet (4a . . . ).

2. The arrangement according to the preceding claim, wherein

the at least one magnet (4a, b) is preferably disposed eccentric to the respective rotation axis (10, 10′

) of the magnet unit (5a, b), and/or

the angle sensor elements (12) have the same resolution and the same measuring precision and are in particular configured in the same manner or identical.

3. The arrangement according to one of the preceding claims, wherein the magnetic field sensitive angle sensor element (12) is an element measuring the magnet vector, in particular

an XMR-element, in particular an AMR-element or

a Hall-array, in particular made from four or more particular HALL-elements or

a vertical Hall-element.

4. The arrangement according to one of the preceding claims, wherein

the arrangement includes processing electronics (30) configured to detect the number of complete revolutions, in particular of the magnet unit (5a, b), directly driven from the outside, from the signals of the two angle sensor elements (12), and in particular

the processing electronics (30) are disposed in the housing (22) of the sensor, and in particular on one of the angle sensor elements (12) configured as a chip.

(Rotational connection)

5. The arrangement according to one of the preceding claims, wherein the rotational connection of the magnet units (5a, b) is an operative mechanical connection, in particular through a teething, in particular of an external teething (28), or a contactless operative connection, in particular through a magnetic coupling, to which the magnet units (5a, b) are rotationally connected.

(Transmission ratio)

6. The arrangement according to one of the preceding claims, wherein

the outer length, in particular the outer teethings (28) of the magnet units differ, e.g. with respect to the numbers of their teeth as little as possible, in particular differ only by one tooth, and thus a differential transmission is formed, or

the two magnet units (5a, b) are operatively connected with a transmission ratio that is as big as possible, and in particular for an external teething (18) at the magnet units (5a, b) the one magnet unit is configured as a one-tooth gear and only the angle sensor element at the magnet unit (5a, b) with the lower speed is a high resolution angle sensor element (12).

7. The arrangement according to one of the preceding claims, wherein

the flux conductor element and the teething are integrally configured and the magnet unit (5a, b) is disposed in particular in the interior of the pot shaped flux conductor element, or

the flux conductor element is a plastic based component in which magnetic particles are embedded, in particular encased, or

the flux conductor element and the teething (28) are separate components, and the flux conductor element is in particular made from ferromagnetic steel and the teething (28) is in particular made from plastic material.

(Passive flux conductor elements)

8. The arrangement according to one of the preceding claims, wherein

when the teething is configured integral with the flux conductor element, the flux conductor element is made from a material with a suitable remanence μ

, in particular with a μ

of 500 to 1,000, in particular 100 to 800, or

for a configuration of the flux conductor element as a separate component, in particular without teething, the flux conductor element is made from a material with suitable remanence μ

, in particular a μ

of over 1,000, in particular over 5,000.

9. The arrangement according to one of the preceding claims, wherein

the flux conductor element envelopes the magnet unit (5a, b) radially, in particular at a distance as a rim, in particular envelopes it in an annular manner as a circular or polygonal flux conductor ring (9), and/or

the flux conductor element covers the magnet unit (5a, b) on the backside facing away from the angle sensor element (12) as a base, in particular as a flux conductor plate (7), and is configured in particular as a flux conductor pot (8).

(Active flux conductor element)

10. The arrangement according to one of the preceding claims, wherein the flux conductor element in a particular composition, arrangement or configuration of the at least one magnet (4) of the magnet unit (5a, b) is made from discrete elements in such a manner that its scatter fields, in particular its radially outer scatter fields, are minimized, but its usable fields supplement and amplify one another.

11. The arrangement according to one of the preceding claims, wherein the angle sensor includes a flux concentrator which guides the field lines to the angle sensor element in a controlled manner, and the flux concentrator is configured in particular as a respective configuration of the surface(s) of the magnet(s) (4) of the magnet unit (5a, b) oriented towards the angle sensor element, and in particular the two magnets (4a, b) disposed eccentric and with their pole axes parallel to the rotation axis (10, 10′

) include a flux exit surface (20), which is inclined towards the rotation axis (10) on the side facing towards the angle sensor element (12).

12. The arrangement according to one of the preceding claims, wherein

the magnet unit (5a, b) in addition to the two eccentric magnets (4a, b) with a pole direction in the direction of the rotation axis (10, 10′

) includes a magnet (4c) there between with a pole orientation transversal to the rotation axis (10, 10′

), which is oriented from one of the first two magnets (4a, b) to the other of the four magnets (4a, b), and/or

the magnet arrangement of the magnet unit (5a, b) is a Hallbach-arrangement, in particular an annular rod shaped Hallbach-arrangement.

(Housing shape)

13. The arrangement according to one of the preceding claims, which is received in a housing, wherein viewed in the direction of the rotation axis (10, 10′

)

the housing (22) is disposed rotation symmetrical with respect to an input shaft, or

the housing has a circular segment shaped, triangular or slotted hole shaped outer contour and the input shaft protrudes in particular into an end portion of the housing (22).

(Multistage transmission)

14. The arrangement according to one of the preceding claims, wherein

the angle sensor comprises more than two magnet units (5b), which respectively have different speed ratios, in particular with reference to the directly driven magnet unit (5a, c, d, e), and in particular all magnet units are disposed in a common plane, and in particular in the rotation symmetrical housing (22), and in particular

about a central driven magnet unit (5a, b), at least four magnet units are arranged with an even distribution, each respectively comprising an external teething (28), and differing with respect to their numbers of teeth from the numbers of teeth of the respective other magnet units (5a, c, d, e) as little as possible.

(Intermediary gear)

15. The arrangement according to one of the preceding claims, wherein an intermediary spacer element, in particular a center gear, is disposed between the two rotating magnet units (5a, b), wherein the intermediary element is in particular the driven gear (1c), and the two magnet units (5a, b) are disposed opposite to one another with respect to the center gear.

(Arrangement of the angle sensor elements)

16. The arrangement according to one of the preceding claims, wherein

the two angle sensor elements (12) are disposed without an offset in the plane of the circuit board (25) and opposite to one another, and the two magnet units (5a, b) rotate about a common rotation axis (10, 10′

), or

the two magnet units rotate about rotation axis (10, 10′

) disposed in parallel to one another and the magnet units (5a, b) are disposed on faces of gears (1a, b) oriented in opposite directions, or

the angle sensor elements (12) are disposed on both sides of the same circuit board (25) oriented away from one another and the magnet units (5a, b) are disposed opposite to one another with respect to the circuit board (25) with the magnet units oriented against one another.

(Support)

17. The arrangement according to one of the preceding claims, wherein at least the non-driven magnet unit (5a, b) is supported in a straight bearing in a housing (22) through a ferrofluid in that either

the shaft extension (11) of the magnet unit (5a, b) supported in a ferrofluidic manner is a magnet (4) with a pole orientation, in particular transversal to the rotation axis (10, 10′

), wherein the magnet is in particular in direct contact with the magnets of the magnet arrangement, and in particular

the magnetic shaft extension (11) with its rear housing side end contacts a retaining ball (26) which is pressed into the support bore hole of the housing (22), in particular made from plastic material, or

the magnet unit (5a, b) is supported rotatable in a ferrofluidic manner with respect to an axle extension which is disposed torque proof in a housing (22) and configured as a magnet (4).

(Pole orientation)

18. The arrangement according to one of the preceding claims, wherein

the two magnets (4a, b) of the magnet unit (5a, b) are disposed eccentric and symmetrical to the angle sensor element (12) with parallel opposite pole orientations, which are disposed parallel to the rotation axis (10) of the magnet unit (5a, b) and the angle sensor element (12) is disposed axially offset from the magnets (4a, b), or

the magnets (4a, b) are disposed eccentric and symmetrical to the angle sensor element (12), wherein the magnets have an identical pole orientation which is oriented transversal to the rotation axis (10, 10′

) of the magnet unit (5a, b), and the angle sensor element (12) is disposed between the magnets (4a, b).