Rotary encoder, method and assembly, each for determining position, and use thereof

Abstract

The invention relates to a rotary encoder for determining position, to a method for determining a position of an output shaft of a drive unit, to an assembly and to a use of the rotary encoder, the rotary encoder comprising: a multi-revolution shaft which rotates about an axis of rotation in a Z-direction; a first magnetic element which is mounted on the multi-revolution shaft; a first detection unit which is designed to sense a magnetic field of the first magnetic element; and a first transmission unit which is designed to change a relative distance between the first magnetic element and the first detection unit in an axial direction along the axis of rotation.

Description

Description Title: Rotary encoder, method and arrangement for position determination and their use CROSS-REFERENCE TO KNOWN APPLICATIONS

[0001] This application claims priority from Luxembourg patent application LU505407, filed on October 31, 2023. The entire content of Luxembourg patent application LU505407 is hereby incorporated herein by reference. FIELD OF THE INVENTION

[0002] The present invention relates generally to a rotary encoder and more particularly to a magnetic absolute encoder. BACKGROUND OF THE INVENTION

[0003] Rotary encoders are well-known in the art and are used to convert mechanical movements into electrical signals. They are generally used for measuring the position and speed of drive units by detecting unique position values. Rotary encoders are generally divided into analog and digital, linear and rotary, and incremental and absolute. Absolute encoders, or absolute value encoders, are further divided into single-turn and multi-turn encoders. Single-turn encoders detect (rotary) movements with an angle of up to 360°. Multi-turn encoders can detect positions over several revolutions.

[0004] Magnetic encoders determine an angular position using detection units, such as magnetic field sensors based on the Hall effect. A permanent magnet generates a magnetic field that is measured by the encoder's detection unit, which in turn generates a unique, absolute position measurement. Analog Hall encoders in motors are known to react strongly to stray magnetic fields, which typically require electronic compensation.

[0005] US 4,914,389 A describes a shaft position sensor for detecting the position of a multiturn shaft. The rotation of the multiturn shaft is converted into a linear movement via a multiturn spindle and two axially spaced, non-rotating nuts, which are continuously axially preloaded in opposite directions by compression springs. A magnet is attached to one of the non-rotating nuts. The linear movement of the magnet is converted into an electrical signal using a magnetoresistive structure.

[0006] EP 0 325 787 A2 also describes a shaft position sensor for detecting the position of a multiturn shaft. The rotation of the multiturn shaft is converted into a linear movement via a multiturn spindle and a non-rotatable nut. A magnet is mounted on the non-rotatable nut. The linear movement of the magnet is converted into an electrical signal via one or more magnetoresistive structures.

[0007] EP 2 932 287 A1 discloses a magnetic field sensor arrangement and associated methods for use as an angle sensor, magnetic field sensor and rotation sensor, which can detect a magnetic field in a Z-axis by means of Hall elements.

[0008] US Pat. No. 6,305,234 B1 discloses an absolute encoder for determining the absolute position of a moving workpiece. The absolute encoder comprises a movable transducer element that can be coupled to the workpiece and a sensor arranged near the transducer element.

[0009] In machine tools, rotary absolute encoders, or absolute rotary encoders, are used for position and speed measurement. A distinction is made between single-turn and multi-turn types. With single-turn encoders, the encoder restarts the measurement or counting after each revolution. With multi-turn encoders, the encoder can count multiple revolutions without a power supply, although a current number of revolutions of approximately 4096 is generally common. The resolution of an encoder is defined by the angular resolution per revolution, such as 32 bits per revolution, and the maximum number of revolutions, for example, approximately 4096, which can be stored even without a power supply.

[0010] DE 10 2016 204890 A1 discloses a method for the adjusted fastening of a magnetic sensor device to an actuator, the magnetic sensor device comprising a transmitter module with at least one permanent magnet and a sensor module with a first sensor for measuring the angle of rotation and a second sensor for counting revolutions, the actuator comprising an electric motor with a stator and a rotor.

[0011] US 2010 / 163333 A1 discloses an angular position sensor for determining the angular position comprising a shaft with a threaded portion and a structure for engagement with an external application. The shaft comprises a first permanent magnet. A nut is threaded onto the threaded portion. The nut is formed from a first magnetically permeable material or comprises a second permanent magnet. At least one limiter is connected to the nut to prevent rotational movement of the nut while allowing linear movement of the nut. A first magnetic sensor is positioned along a length of the threaded portion of the nut to measure a linear position of the nut. A second magnetic sensor is provided for measuring an angular position of the shaft.A signal processing circuit is coupled to receive both the output signals of the first magnetic sensor and the second magnetic sensor to calculate a parameter related to an angular position of the rotatable member.

[0012] EP 1 202 025 A2 discloses an angle measuring device with magnetic, optical or magneto-optical structures on a shaft or a part connected thereto, a thread on the shaft which engages in a slider movable in the axial direction of the shaft, and at least one sensor for detecting the magnetic, optical or magneto-optical structures and the displacement position of the slider.

[0013] US 2019 / 331507 A1 discloses a multi-turn sensor that may include a first and a second shaft with respective rotation axes approximately perpendicular to each other, a first magnet provided at one end of the first shaft, and a second magnet provided at one end of the second shaft. The multi-turn sensor may further include a first magnetic sensor provided adjacent to the first magnet to enable non-contact detection of the angular position of the first shaft when the first shaft rotates, and a second magnetic sensor provided adjacent to the second magnet to enable non-contact detection of the angular position of the second shaft when the second shaft rotates. The multi-turn sensor may further include a gear mechanism configured to couple the first shaft and the second shaft such that rotation of the first shaft results in rotation of the second shaft.

[0014] DE 10 2005 011099 A1 discloses a device and a method for contactlessly determining the angle of rotation of a rotatable element. The device comprises at least one magnetoresistive sensor element that emits at least a first signal for determining a rotation angle of the rotatable element within a first range. A plunger core and a coil move relative to each other in the axial direction of a shaft in accordance with the rotational movement of the shaft, and the coil emits a further signal related to the change in the coil inductance, so that angles of rotation beyond the first range can be unambiguously determined in conjunction with the first signal.

[0015] A common problem is that the precise determination of unique position values, or the recording / counting and determination of the travel or revolutions of output shafts in absolute multiturn encoders, can be disrupted if the encoder's supply voltage is interrupted, for example, due to a power failure. This can be particularly critical if the recording and determination of the travel or revolutions are lost because, after the supply voltage fails or is switched off, the output shaft to be recorded moves or rotates further before the supply voltage is restored.

[0016] To prevent such a case, the counting or storing / memorizing of the distance or revolutions without a supply voltage can be done electronically or mechanically via, for example, a gear or a combination thereof, which makes the system more complex and increases the costs.

[0017] Depending on the design, required resolution, and precision, such encoders are very expensive. Therefore, the object of the present application is to provide an encoder, a method, and an arrangement in which unambiguous position values ​​can be precisely determined even in the event of a power loss. A further object of the present application is to precisely determine the exact position of the output shaft even after the output shaft has moved during a power loss. A further object of the present application is to increase the desired resolution in a resource-efficient manner despite stray magnetic fields, while keeping or reducing the cost of the encoder. BRIEF DESCRIPTION OF THE INVENTION

[0018] These tasks are solved by a rotary encoder for position determination, a method for determining a position of an output shaft of a drive unit, an arrangement and a use of the rotary encoder.

[0019] The rotary encoder comprises a multi-turn shaft rotating about a rotation axis in a Z direction, a first magnetic element mounted on the multi-turn shaft, a first detection unit configured to detect a magnetic field of the first magnetic element, and a first gear unit configured to change a relative distance between the first magnetic element and the first detection unit in an axial direction along the rotation axis.

[0020] With the rotary encoder it is possible to remember / continue counting the measured or counted distance or revolutions of the output shaft even if the supply voltage is lost by providing a cost-effective multi-turn rotary encoder based on a single-turn rotary encoder by taking into account the change in the relative distance in the Z-axis (third dimension).

[0021] In one aspect, the first gear unit changes the relative distance depending on an angular position of the multi-turn shaft.

[0022] This allows the encoder to absolutely determine the rotation of the drive unit's output shaft at any time using the angular position and relative distance.

[0023] According to a further aspect, the first detection unit detects the change in the magnetic field of the first magnetic element in at least one of the Z direction, an X direction and a Y direction, wherein the X, Y and Z directions are each arranged orthogonally to each other.

[0024] This makes it possible to detect the change in the magnetic field of the first magnetic element in three dimensions (X, Y, Z) with a single first detection unit, thereby reducing costs.

[0025] According to another aspect, the first detection unit detects the change of the magnetic field in XY directions due to the rotation of the first magnetic element and detects the change of the magnetic field in the Z direction due to the relative distance.

[0026] This type of detection makes it possible to always determine the absolute position of the drive unit's output shaft.

[0027] The above-mentioned object is further achieved by a rotary encoder comprising a multi-turn shaft rotating about a rotation axis in a Z direction, a first gear unit provided on the multi-turn shaft, a second gear unit provided on the first gear unit, an intermediate shaft provided along one of an X direction or Y direction, a first magnetic element mounted on the multi-turn shaft, a first detection unit configured to detect a first magnetic field of the first magnetic element, a second magnetic element mounted on the intermediate shaft, and a second detection unit configured to detect a second magnetic field of the second magnetic element. The second gear unit is configured to transmit the rotation of the multi-turn shaft to a rotation of the intermediate shaft.

[0028] With the rotary encoder it is possible to remember / continue counting the measured or counted distance or revolutions of the output shaft even if the supply voltage is lost by providing a cost-effective multi-turn rotary encoder based on a single-turn rotary encoder by taking into account the change in the relative distance in the Z-axis (third dimension).

[0029] According to one aspect, the first detection unit detects the magnetic field of the first magnetic element in a first plane, and the second detection unit detects the magnetic field of the second magnetic element in a second plane, wherein the first plane is different from the second plane.

[0030] This allows the number of revolutions to be increased regardless of the angular resolution per revolution (360 degrees).

[0031] According to a further aspect, the first plane is defined by the XY directions and the second plane is defined by at least one of an X direction and a Z direction, wherein the X, Y and Z directions are each arranged orthogonally to each other.

[0032] This allows the magnetic field or a change in the magnetic field to be detected in three dimensions by the two detection units.

[0033] According to a further aspect, the rotary encoders comprise a coupling, wherein the coupling couples the multi-rotation shaft to the output shaft of the drive unit.

[0034] This allows the encoders to be coupled to the output shaft of the drive unit in order to count / measure the distance or revolution of the output shaft.

[0035] In another aspect, the multi-rotation shaft comprises at least one of a first rotation shaft and a second rotation shaft.

[0036] This makes it possible to set a direction of rotation and ratio of the multi-turn shaft to the output shaft.

[0037] According to a further aspect, the gear unit enables a change in a direction of rotation of the intermediate shaft and / or the second rotation shaft to the first rotation shaft.

[0038] This allows the direction of rotation of the intermediate shaft and / or the second rotation shaft to be reversed relative to the direction of rotation of the output shaft, if desired or required.

[0039] According to a further aspect, the gear unit enables a gear ratio of less than 1, equal to 1 or greater than 1.

[0040] This allows the desired resolution and precision of the encoders to be further adjusted.

[0041] According to a further aspect, the detection unit consists of at least one detection element.

[0042] This allows the size and cost of the first and second detection units to be adjusted.

[0043] The above-mentioned object is further achieved by a method for determining a position of the output shaft of the drive unit. The method comprises providing the rotary encoder on the output shaft by means of the coupling, rotating the multi-rotation shaft of the rotary encoder with the output shaft of the drive unit, detecting the change in the magnetic field of the first magnetic element of the rotary encoder in three directions, and determining an absolute rotational position of the output shaft as a function of the change in at least one detected magnetic field.

[0044] This method makes it possible to remember / continue counting the measured or counted distance or revolutions of the output shaft even if the supply voltage is lost.

[0045] According to one aspect, the determination of the absolute rotary position during multiple revolutions occurs with recurring voltage supply of the rotary encoder without loss of information.

[0046] This allows the absolute rotational position of the output shaft and thus the counting / measurement to be continued at any time.

[0047] The above-mentioned object is further achieved by an arrangement which comprises the rotary encoder and the drive unit.

[0048] The above-mentioned object is further achieved by using the rotary encoder or the method or the arrangement for measuring the position and speed of the output shaft of the drive unit as a function of the absolute rotational position of the output shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The invention will now be explained in more detail with reference to the drawings. They show:

[0050] Fig. 1 is a schematic representation of a rotary encoder according to a first embodiment.

[0051] Fig. 2 is a schematic representation of the rotary encoder according to a second embodiment.

[0052] Fig. 3 is a flowchart of a method for determining a position of an output shaft of a drive unit.

[0053] Fig. 4 is a schematic representation of an arrangement. DETAILED DESCRIPTION OF THE INVENTION

[0054] Fig. 1 shows a schematic representation of a rotary encoder 100 according to a first embodiment. The rotary encoder 100 comprises a multi-rotation shaft 10, a first magnetic element 20, a first detection unit 30, and a first gear unit 40. The multi-rotation shaft 10 rotates about a rotation axis Al, wherein the rotation axis Al is provided in a Z-direction Z. The multi-rotation Shaft 10 comprises at least one of a first rotation shaft 10A and a second rotation shaft 10B. The first magnetic element 20 is mounted on the multi-rotation shaft 10. The first detection unit 30 is configured to detect a magnetic field of the first magnetic element 20. The first gear unit 40 is configured to change a relative distance 60 between the first magnetic element 20 and the first detection unit 40 in an axial direction D1 along the rotation axis A1. The first gear unit 40 changes the relative distance 60 depending on an angular position of the multi-rotation shaft 10. The relative distance 60 thus changes with the rotation of the multi-rotation shaft 10, in particular the second rotation shaft 10B. The first gear unit 40 enables a change in a rotation direction of the second rotation shaft 10B to the first rotation shaft 10A.The first gear unit 40 enables a gear ratio of less than 1, equal to 1, or greater than 1. This allows the second rotation shaft 10B to rotate slower, equal to, or faster in the same or opposite direction of rotation compared to the first rotation shaft 10A.

[0055] The first detection unit 30 detects the change in the magnetic field of the first magnetic element 20 in at least one of the Z direction Z, an X direction X and a Y direction Y. The X, Y and Z directions X, Y, Z are each arranged orthogonally to one another and span three mutually orthogonal planes.

[0056] The first detection unit 30 detects the change of the magnetic field of the first magnetic element 20 in the XY directions X, Y due to the rotation of the first magnetic element 20 and detects the change of the magnetic field of the first magnetic element 20 in the Z direction Z due to the change of the relative distance 60.

[0057] The rotary encoder 100 further comprises a coupling 50, wherein the coupling 50 couples the multi-rotation shaft 10 to an output shaft 72 of a drive unit 70. The coupling 50 can comprise any type of known coupling for two shafts and is therefore not described in further detail. The drive unit 70 can comprise any type of known drive unit with an output shaft, in particular an electric motor, and is therefore not described in further detail.

[0058] Fig. 2 shows a schematic representation of the rotary encoder 200 according to a second embodiment. The rotary encoder 100 of the first embodiment is identical to the rotary encoder 100. For the sake of clarity, the technical components of the rotary encoder 200 according to the second embodiment are designated by the same reference numerals and will not be described in detail again.

[0059] The rotary encoder 200 further comprises a second gear unit 240, an intermediate shaft 210, a second magnetic element 220 and a second detection unit 230.

[0060] The second gear unit 240 is provided on the first gear unit 40. The second gear unit 240 enables a change in the rotation direction of the intermediate shaft 210 relative to the first rotating shaft 10A. The second gear unit 240 enables a gear ratio of less than 1, equal to 1, or greater than 1. This allows the intermediate shaft 210 to rotate more slowly, the same speed, or faster in the same or opposite direction of rotation compared to the first rotating shaft 10A. The rotational speed of the first rotating shaft 10A corresponds to the rotational speed of the output shaft 72.

[0061] The first gear unit 40 and the second gear unit 240 may comprise any known gear mechanism, but in particular at least one of a gear mechanism, worm gear mechanism, slide-crank mechanism or eccentric mechanism.

[0062] The second detection unit 230 detects the magnetic field of the second magnetic element 220 in a second plane, wherein the first plane is different from the second plane. The first plane is defined by the XY directions X, Y, and the second plane is defined by at least one of the X direction X and the Z direction Z.

[0063] The first detection unit and the second detection unit 230 consist of at least one detection element 30a, 30b, 30c, wherein the at least one detection element consists of at least one of a one-dimensional detection element 30a, a two-dimensional detection element 30b, and a three-dimensional detection element 30c. The two-dimensional detection element 30b can consist of two one-dimensional detection elements 30a. The three-dimensional detection element 30c can consist of a one-dimensional detection element 30a and a two-dimensional detection element 30b, or can consist of three one-dimensional detection elements 30a. This can influence the costs for the first detection unit 30.

[0064] One-dimensional means detecting the magnetic field in one of the X-direction (X), the Y-direction (Y), or the Z-direction (Z). Two-dimensional means detecting the magnetic field in one of the XY-directions (X, Y), the XZ-directions (X, Z), or the YZ-directions (Y, Z). Three-dimensional means detecting the magnetic field in the X-YZ-directions (X, Y, Z).

[0065] Fig. 3 shows a flowchart of a method for determining the position of the output shaft 72 of the drive unit 70. In the first step S1, the rotary encoder 100, 200 is provided on the output shaft 72 by means of the coupling 50. In the second step S2, the multi-revolution shaft 10 of the rotary encoder 100, 200 is rotated with the output shaft 72 of the drive unit 70. In the third step S3, the change in the magnetic field of the first and / or second magnetic element 20, 220 of the rotary encoder 100, 200 is detected in the three directions, X direction X, Y direction Y, and Z direction Z. In the fourth step S4, an absolute rotational position of the output shaft 72 is determined as a function of the change in at least one detected magnetic field. The determination of the absolute rotational position in the fourth step S4 can be carried out without loss of information during multiple revolutions with recurring voltage supply of the rotary encoder 100, 200.A loss of information would occur if the absolute rotary position or the count of the path or revolution of the output shaft were lost upon loss of the supply voltage and the absolute rotary position did not correspond to the real absolute rotary position when the supply voltage returned.

[0066] Fig. 4 shows a schematic representation of an arrangement 400. The arrangement 400 comprises the rotary encoder 100, 200 and the drive unit 70.

[0067] At least one of the rotary encoder 100, 200, the method 300 or the arrangement 400 can be used to measure the position and speed of the output shaft 72 of the drive unit 70 as a function of the absolute rotational position of the output shaft 72. List of reference symbols 100, 200 encoders 300 procedures 400 arrangement 10 multi-rotation shaft 10A first rotation shaft 10B second rotation shaft 20 first magnetic element 30 first detection unit 30a one-dimensional detection elements 30b two-dimensional detection elements 30c three-dimensional detection elements 40 first gear unit 50 coupling 60 relative distance 70 drive unit 72 Output shaft 210 intermediate shaft 220 second magnetic element 230 second detection unit 240 second gear unit Al rotation axis DI axial direction X X-direction Y Y-direction ZZ direction

Claims

Claims 1. A rotary encoder (100; 200) for position determination, the rotary encoder (100) comprising: a multi-revolution shaft (10) rotating about a rotation axis (Al) in a Z direction (Z); a first magnetic element (20) mounted on the multi-revolution shaft (10); a first detection unit (30) configured to detect a magnetic field of the first magnetic element (20); and a first gear unit (40) configured to change a relative distance (60) between the first magnetic element (20) and the detection unit (40) in an axial direction (Dl) along the rotation axis (Al).

2. Rotary encoder (100; 200) according to claim 1, wherein the first gear unit (40) changes the relative distance (60) depending on an angular position of the multi-revolution shaft (10).

3. Rotary encoder (100; 200) according to claim 1 or 2, wherein the detection unit (30) detects the change in the magnetic field of the first magnetic element (20) in at least one of the Z direction (Z), an X direction (X) and a Y direction (Y), wherein the X, Y and Z directions (X, Y, Z) are each arranged orthogonally to one another.

4. Rotary encoder (100; 200) according to one of the preceding claims, wherein the detection unit (30) detects the change of the magnetic field in XY directions (X, Y) due to the rotation of the first magnetic element (20) and detects the change of the magnetic field in the Z direction (Z) due to the relative distance (60).

5. Rotary encoder (100; 200) for position detection, the rotary encoder (200) comprising: a multi-revolution shaft (10) rotating about a rotation axis (Al) in a Z direction (Z); a first gear unit (40) provided on the multi-rotation shaft (10); a second gear unit (240) provided on the first gear unit (40); an intermediate shaft (210) provided along one of an X-direction (X) or Y-direction (Y); a first magnetic element (20) mounted on the multi-rotation shaft (10); a first detection unit (30) configured to detect a first magnetic field of the first magnetic element (20); a second magnetic element (220) mounted on the intermediate shaft (210); and a second detection unit (230) configured to detect a second magnetic field of the second magnetic element (220), wherein the second gear unit (240) is configured to transmit the rotation of the multi-rotation shaft (10) to a rotation of the intermediate shaft (210).

6. Rotary encoder (100; 200) according to claim 5, wherein the first detection unit (30) detects the magnetic field of the first magnetic element (20) in a first plane, and the second detection unit (230) detects the magnetic field of the second magnetic element (220) in a second plane, wherein the first plane is different from the second plane.

7. Rotary encoder (100; 200) according to claim 6, wherein the first plane is defined by the XY directions (X, Y) and the second plane is defined by at least one of an X direction (X) and a Z direction (Z), wherein the X, Y and Z directions (X, Y, Z) are each arranged orthogonally to one another.

8. Rotary encoder (100; 200) according to one of the preceding claims, further comprising a coupling (50), wherein the coupling (50) couples the multi-revolution shaft (10) to an output shaft (72) of a drive unit (70).

9. Rotary encoder (100; 200) according to one of the preceding claims, in which the multi-rotation shaft (10) comprises at least one of a first rotation shaft (10A) and a second rotation shaft (10B).

10. Rotary encoder (100; 200) according to claim 9, wherein the gear unit (40; 240) enables a change in a direction of rotation of the intermediate shaft (210) and / or the second rotation shaft (10B) to the first rotation shaft (10A).

11. Rotary encoder (100; 200) according to one of the preceding claims, wherein the gear unit (40; 240) enables a gear ratio of less than 1, equal to 1 or greater than 1.

12. Rotary encoder (100; 200) according to one of the preceding claims, wherein the detection unit (30; 230) consists of at least one detection element (30a; 30b; 30c).

13. A method (300) for determining a position of an output shaft (72) of a drive unit (70), the method comprising: - Providing (S1) a rotary encoder (100; 200) according to one of claims 1 to 12 on the output shaft (72) by means of a coupling (50); - rotating (S2) a multi-rotation shaft (10) of the rotary encoder (100; 200) with the output shaft (72) of the drive unit (70); - detecting (S3) a change in a magnetic field of a magnetic element (20; 220) of the rotary encoder (100; 200) in three directions (X, Y, Z); - Determining (S4) an absolute rotational position of the output shaft (72) as a function of the change in at least one detected magnetic field.

14. Method (300) according to claim 13, wherein the determination (S4) of the absolute rotational position during multiple revolutions takes place without loss of information when the power supply to the rotary encoder (100; 200) is recurring.

15. An arrangement (400) comprising: a rotary encoder (100; 200) according to one of claims 1 to 12; and a drive unit (70).

16. Use of the rotary encoder (100; 200) according to one of claims 1 to 12 or of the method (300) according to one of claims 13 to 14 or of the arrangement (400) according to claim 15 for measuring the displacement and rotational speed of an output shaft (72) of a drive unit (70) as a function of an absolute rotational position of the output shaft (72).

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