Sensor arrangement, electric machine and electrically operated drive train for a motor vehicle

Abstract

Sensor arrangement (22) comprising an inductive rotor position sensor (9), with at least one energizable transmitting coil (15) and one receiving coil (16), wherein the transmitting coil (15) spans a first surface (20) and the receiving coil (16) spans a second surface (21) parallel thereto or in the same plane as the first surface (20), wherein the sensor arrangement (22) further comprises a first sensor target (10) which is movable relative to the transmitting coil (15) and receiving coil (16) such that it is always located outside the first surface (20) and the second surface (21) and their orthogonal projections (23), wherein the sensor target (10) is arranged in a shaft opening (8) of a rotor shaft (6), wherein on an inner circumferential surface (11) of the shaft opening (8) shaft sections (12) are formed which extend radially inward and / or outward therefrom and form the sensor target (10) for the rotor position sensor (9).

Description

[0001] The present invention relates to a sensor arrangement comprising an inductive rotor position sensor with at least one energizable transmitting coil and a receiving coil, wherein the transmitting coil defines a first surface and the receiving coil defines a second surface parallel to or in the same plane as the first surface. The invention further relates to an electric machine and an electrically operable drive train for a motor vehicle.

[0002] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0003] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 113, May 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, titled "Highly Integrated and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for a vehicle axle that includes an electric motor arranged concentrically and coaxially with a bevel gear differential. Such drive units are also referred to as e-axles or electrically operated drivetrains.

[0004] In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling purely electric operation—for example, in urban areas—while maintaining sufficient range and availability, especially for long-distance journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor simultaneously.

[0005] Sensors are used in many of these drivetrains to capture angular and rotational information, for example, from an electric machine. These sensors consist, in simplified form, of a sensor rotor and a sensor stator. The sensor itself is usually permanently connected to the housing of the electric machine. The sensor rotor is usually a rotationally symmetrical component that rotates with the rotor of the electric machine.

[0006] Permanent-magnet synchronous motors are used in many of the electromobility applications mentioned above. Such a permanent-magnet synchronous motor comprises a stator to be energized and a permanent-magnet rotor. The rotor typically comprises a shaft, balancing plates, rotor cores, and magnets. The magnets are generally fixed in the rotor cores.

[0007] To control such electronically commutated electrical machines, electrical control variables are applied to the machine's stator windings depending on the rotor's angular position in order to drive them. The rotor position is usually detected using a rotor position sensor and fed to a control unit to generate the control signals required for commutation of the electrical machine. Rotor position sensors provide either an analog electrical variable dependent on the rotor position, e.g., a voltage, signal pulses, or a digitized value indicating the absolute rotor position. Such rotor position sensors are generally known from the prior art. A signal generator (magnetic target) mounted on the rotor in a rotationally fixed manner is read by a magnetic field sensor mounted on the stator in a rotationally fixed manner.

[0008] For example, DE 10 2009 001 353 A1 discloses an electric machine comprising a rotor with a rotor hub, a stator arranged in a stator housing, and a cover connected to the stator housing, extending to the inner diameter of the rotor hub, and supporting the rotor by means of a rotor bearing. The electric machine has a rotor position sensor for detecting the rotational position of the rotor relative to the stator's magnetic field. The rotor position sensor is arranged on the cover near the rotor bearing in such a way that the rotor hub or a component connected to the rotor hub in a rotationally fixed manner serves as the sensor track of the rotor position sensor.

[0009] DE 10 2018 204 901 A1 discloses "The invention is based on a sensor device (10a-e) for detecting at least one item of position information of a movably mounted rotor (12a) of an electric motor (14a; 14e), in particular of a steering system (16a), with at least two position sensor units (18a, 20a; 20b; 20c; 18d, 20d) operatively connected to the rotor (12a) for detecting the position information of the rotor (12a). It is proposed that the position sensor units (18a, 20a; 20b; 20c; 18d, 20d) have different measuring principles for detecting the position information."

[0010] DE 10 2021 131 033 B3 discloses "The invention relates to a sensor arrangement for determining an angular position of a rotatable component, such as in particular a shaft, comprising a first annular sensor target with a plurality of teeth and grooves distributed over the circumference and arranged alternately over the circumference, as well as a first inductive sensor which is arranged axially spaced from the first sensor target, and the sensor target and the first inductive sensor are rotatable relative to one another about a common axis of rotation, wherein the first inductive sensor has a first coil and a second coil, each extending in a radial plane to the axis of rotation, wherein the first coil has a sinusoidal profile along a circular circumference and the second coil has a phase-shifted profile, in particular a cos-shaped profile along the circular circumference,wherein the first inductive sensor comprises a third coil which can be energized, wherein the third coil which can be energized is arranged radially offset within the first coil and the second coil and the grooves are open radially inwardly.",

[0011] DE 10 2017 104 206 A1 discloses "A sensor assembly comprising a rotatable drive shaft extending along a rotational axis and having a bore extending from a first end face of the shaft along the rotational axis; a magnet disposed at least partially within the bore and coupled to the drive shaft, the magnet configured to generate a magnetic field within the bore; a sensor element disposed at least partially within the bore and configured to detect rotation of the magnetic field in response to rotation of the drive shaft; and a magnetostatic shield disposed to surround the magnet and the sensor element, the magnetostatic shield being stationary with respect to the drive shaft."

[0012] DE 10 2017 212 039 A1 discloses “The invention relates to a rotation angle measuring device for a synchronous electric motor for measuring a rotation of a shaft about a rotation axis, in particular a shaft of the electric motor, with a magnetic element which generates a magnetic field in a measuring space enclosed by the magnetic element, wherein the magnetic element is coupled to the shaft in a rotationally fixed manner, with a magnetic field sensor which can determine a magnetic field angle in a measuring plane and which is arranged in the measuring space, and with a magnetic field sensor carrier on which the magnetic field sensor is held and which has a main longitudinal direction.In order to enable a more compact design, it is proposed that the magnetic field sensor is arranged such that the measuring plane runs substantially perpendicular to the axis of rotation of the shaft, that the magnetic field sensor carrier has a sensor board which has a first section on which the magnetic field sensor is fastened and electrically contacted, that the sensor board has a flexible section which adjoins the first section of the sensor board, that the magnetic field sensor carrier has a sensor receptacle which is arranged at an end of the magnetic field sensor carrier lying in the main longitudinal direction, and that the first section of the sensor board is held on the sensor receptacle."

[0013] DE 10 2019 122 046 A1 discloses: "The following describes a device for measuring the angular position or rotational movement of a shaft. According to one embodiment, the device comprises a first housing part and a shaft arranged in the first housing part and rotatable about a rotational axis. The shaft has a bore extending from an end face of the shaft into the shaft along the rotational axis. The device further comprises a magnet unit with at least one permanent magnet arranged within the bore and fastened to the shaft, a second housing part with a projection extending into the bore along the rotational axis, and a magnetic field sensor element arranged inside the projection of the second housing part."

[0014] In addition to rotor position sensors that operate with a magnetic target, inductive rotor position sensors are also known. These have the advantage of eliminating the need for a permanent magnet. This advantage counteracts the challenge of generating sufficiently accurate sensor signals using an inductive sensor arrangement.

[0015] The object of the invention is to provide a particularly compact and cost-effective sensor arrangement for inductively determining the position of a sensor target. It is also the object to realize an electric machine that has the most accurate rotor position sensor technology possible while maintaining a compact design. Furthermore, the object of the invention is to realize a space-optimized electrically operated drive train for a motor vehicle.

[0016] This object is achieved by a sensor arrangement comprising an inductive rotor position sensor, with at least one energizable transmitting coil and a receiving coil, wherein the transmitting coil spans a first surface and the receiving coil spans a second surface parallel thereto or in the same plane as the first surface, wherein the sensor arrangement further has a first sensor target that is movable relative to the transmitting coil and receiving coil such that it always lies outside the first surface and the second surface and their orthogonal projections, wherein the sensor target is arranged in a shaft opening of a rotor shaft, wherein on an inner circumferential surface of the shaft opening, shaft sections are formed which extend radially in and / or out of this shaft opening and form the sensor target for the rotor position sensor.

[0017] A key advantage of this sensor arrangement is its compact design, especially in the axial direction. Furthermore, the coils can be arranged cost-effectively, for example, on a circuit board.

[0018] Preferably, the rotational position sensor is configured as an inductive rotational position sensor. Such an inductive rotational position sensor consists of two main components: the sensor target and the sensor itself. The sensor target is a component formed or attached to the rotor of the electric machine and rotates with the rotor. It can be a metal disc, an electrically conductive pattern, or another material that generates a change in the magnetic field as it rotates. Preferably, the sensor target is formed integrally with the rotor shaft.

[0019] The inductive rotary position sensor is mounted near the sensor target and generates a magnetic field. As the sensor target rotates, the magnetic field detected by the sensor changes. These changes are converted by the sensor into an electrical signal. The sensor contains a coil through which an alternating current flows. This transmitter coil is sometimes referred to as the TX coil. The changing magnetic field of the sensor target creates a change in the flow of the magnetic field through a receiver coil of the sensor, which is also referred to as the RX coil. This change in the magnetic flux generates an electrical voltage in the sensor coil, which serves as the sensor's output signal. The amplitude and / or frequency of the output signal depend on the rotational position of the rotor. By evaluating the output signal, the exact rotational position of the rotor can be determined.This can be achieved through signal processing techniques such as amplitude or phase modulation.

[0020] In an inductive rotational position sensor of the sensor arrangement according to the invention, the sensor target is preferably located in the same plane as the surfaces spanned by the receiver coils (RX coils), but is positioned radially outside the receiver coils (RX coils).

[0021] The rotation position sensor can provide an absolute or relative angular position as an output signal.

[0022] The rotor shaft is preferably formed from a metallic material.

[0023] Advantageously, the first sensor target is rotatable along a circular path around the transmitting coil and the receiving coil, which makes the sensor arrangement particularly suitable for determining rotational positions, for example, of rotors. However, it would also be conceivable for the sensor target to have a movement path that deviates from a circular path. For example, it would also be conceivable for the sensor target to move along a linear path.

[0024] According to an advantageous embodiment of the invention, the rotor can be provided, at least in sections, with a rotor shaft configured as a hollow shaft, and the sensor target can be arranged in the hollow shaft, which allows for a particularly compact axial design of the sensor arrangement. In this context, it is also conceivable for the rotor shaft to be configured as a hollow shaft in sections, in which the rotor shaft has a concentric blind hole.

[0025] According to a further preferred development of the invention, it can also be provided that the rotational position sensor engages axially at least partially, preferably completely, into the hollow shaft, which also contributes to an axially particularly compact design of the sensor arrangement.

[0026] According to an advantageous embodiment of the invention, the shaft sections can be formed integrally, in particular monolithically, with the rotor shaft. The advantage of this embodiment is that the sensor target can be manufactured particularly inexpensively and precisely, for example, by milling. Furthermore, the one-piece design eliminates the need to mount the sensor target separately. This also prevents potential assembly errors.

[0027] According to a further preferred development of the invention, the rotor position sensor can also be provided with a circuit board with a circular outer contour, which is accommodated in the cylindrical shaft opening with a certain amount of play and is traversed by the shaft sections during rotation of the rotor shaft. This allows for particularly good use of the installation space within the shaft opening. Preferably, the shaft opening has a corresponding circular inner contour, with the circuit board being arranged coaxially with the shaft opening.

[0028] Furthermore, according to a likewise advantageous embodiment of the invention, the circuit board can be provided with at least one energizable transmitting coil and at least one receiving coil. With the combination of transmitting coils and receiving coils, various measurement methods and techniques can be used. For example, the phase shift between the transmitted and received signal can be used to determine the rotational position. This allows the sensor to be adapted to different requirements and applications. The coils are preferably configured for an inductive rotational position sensor.

[0029] Furthermore, the invention can also be further developed such that the shaft sections comprise axially extending grooves distributed over the circumference of the inner circumferential surface. The advantage of this design is that the grooves are easy to manufacture.

[0030] In a likewise preferred embodiment variant of the invention, it can also be provided that the rotor position sensor is completely accommodated in the shaft opening, which supports electrical machines with a particularly compact axial design.

[0031] It may also be advantageous to further develop the invention in such a way that the shaft opening extends axially completely through the rotor shaft, so that the rotor shaft is designed as a hollow shaft. This can achieve a particularly significant weight reduction and, at the same time, allow a cooling fluid to flow through the hollow shaft, which can contribute to improved rotor performance.

[0032] The object of the invention can also be achieved by an electric machine, in particular for a drive train of a motor vehicle, comprising a stator and a rotor which is rotatable relative to the stator and which is coupled in a torque-transmitting manner to a rotor shaft which has a shaft opening extending axially into the rotor shaft from one of the end faces, wherein the electric machine further has a sensor arrangement by means of which the angular position of the rotor can be determined via a sensor target which rotates with the rotor shaft, wherein the sensor arrangement is designed according to one of claims 1-8.

[0033] This makes it possible to provide an axially particularly compact electrical machine, since the rotor position sensor is positioned radially nested within the sensor target running in the rotor shaft.

[0034] Therefore, it is also preferred that the rotational position sensor interacts with the sensor target without contact. By positioning it within the rotor shaft, the sensor is partially protected from electrical and magnetic fields, which can be advantageous with regard to the EMC behavior of the rotor position sensor.

[0035] According to a further preferred embodiment of the subject matter of the invention, it can be provided that the electrical machine is configured as an electrically excited synchronous machine.

[0036] Finally, the object of the invention can be achieved by an electrically operable drive train of a motor vehicle comprising an electric machine according to claim 9.

[0037] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0038] It shows: Fig. 1 an electrical machine in a schematic axial section, Fig. 2 shows a first embodiment of a rotor shaft with a rotor position sensor in a cross-sectional and an axial sectional view, Fig. 3 a second embodiment of a rotor shaft with a rotor position sensor in a cross-sectional and an axial sectional view, Fig. 4 a motor vehicle with an electrically operated drive train in a schematic representation, Fig. 5 a first embodiment of transmitting and receiving coil(s) of the rotor position sensor in a cross-sectional view, Fig. 6 a second embodiment of transmitting and receiving coil(s) of the rotor position sensor in a cross-sectional view, Fig. 7 a third embodiment of transmitting and receiving coil(s) of the rotor position sensor in a cross-sectional view, Fig. 8 a sensor arrangement with orthogonal projections in a schematic perspective view, Fig. 9 a third embodiment of a rotor shaft with a rotor position sensor in an axial sectional view, Fig. 10 a fourth embodiment of a rotor shaft with a rotor position sensor in a cross-sectional and an axial sectional view.

[0039] The Fig. 1 shows an electric machine 1, in particular for a drive train 2 of a motor vehicle 3, as is also shown in the Fig. 4 is outlined.

[0040] The electric machine 1 comprises a stator 4 and a rotor 5 which is rotatable relative to the stator 4 and which is coupled to a rotor shaft 6 in a torque-transmitting manner, which has a shaft opening 8 extending axially into the rotor shaft 6 from one of the end faces 7.

[0041] The electric machine 1 further comprises a rotor position sensor 9, by means of which the angular position of the rotor 5 can be determined via a sensor target 10 rotating with the rotor shaft 6, which can be seen from the synopsis of the Fig. 1 with the Fig. 2-3 can be easily understood.

[0042] The rotor position sensor 9 is part of a sensor arrangement 22, as shown by way of example in the Fig. 8. The sensor arrangement 22 comprises the inductive rotor position sensor 9, with at least one energizable transmitting coil 15 and a receiving coil 16, wherein the transmitting coil 15 spans a first surface 20 and the receiving coil 16 spans a second surface 21 lying in approximately the same plane as the first surface 20. In the example shown, due to their design, the surfaces 20 and 21 do not lie exactly in the same plane but run parallel to one another and are arranged on the same circuit board 13, which typically has a thickness of between 0.8 and 2.0 mm. The receiving coil 16 and / or the transmitting coil 15 can be distributed over several layers across the thickness of the circuit board 13. It is also possible to distribute the receiving coil 16 and the transmitting coil 15 in the same layers of the circuit board 13 or to overlap them.

[0043] It is understood that multiple receiving coils may also be present to improve accuracy and signal quality. The sensor arrangement 22 shown further comprises a first sensor target 10, which is movable relative to the transmitting coil 15 and receiving coil 16 such that it always lies outside the first surface 20 and the second surface 21, as well as their orthogonal projections 23. In the embodiment shown, the first sensor target 10 rotates along a circular path around the transmitting coil 15 and the receiving coil 16. It is essential to the invention that the first sensor target 10 does not extend through the surfaces 20, 21 or their orthogonal projections 23.

[0044] On the inner circumferential surface 11 of the shaft opening 8, shaft sections 12 are formed that extend radially inward and / or outward therefrom, forming the sensor target 10 for the rotor position sensor 9. The rotor position sensor 9 engages in the shaft opening 8 while stationary relative to the rotor shaft 6, such that it is at least partially traversed by the shaft sections 12 when the rotor shaft 6 rotates.

[0045] The shaft sections 12, which are circular in cross section, are formed in one piece, in particular monolithically, with the rotor shaft 6, in that axially extending grooves 18 run through the rotor shaft 6 and are positioned equidistantly distributed over the circumference of the inner lateral surface 11.

[0046] The rotor position sensor 9 has a disk-like circuit board 13 with a circular outer contour 14, which is accommodated coaxially and with play in the cylindrical shaft opening 8 and is passed over by the shaft sections 12 during rotation of the rotor shaft 6. As shown in the Fig. 9-10, it is also possible that the circuit board 13 is arranged outside the rotor shaft 6 and is accordingly not run over by the shaft sections 12.

[0047] Since the rotor position sensor 9 is configured as an inductive sensor, the circuit board 13 has at least one energizable transmitting coil 15 and at least one receiving coil 16. In the Fig. 5-7 show different embodiments of the transmitting coil 15 and the receiving coils 15, in which the coils 15, 16 extend in a radial plane of the circuit board 13. While the transmitting coil 15 extends in a circular ring along the outer surface 17 of the circuit board 13, the receiving coils 16 are arranged radially within the circular ring-shaped transmitting coil 15. In the embodiments shown, the receiving coils 16 are designed like segments of a circular ring. The receiving coils 16 shown in dashed lines have a different winding direction than the receiving coils 16, which are shown with a solid line.

[0048] As in the Fig. 6, a further transmitting coil 15 or further turns of a transmitting coil 15 can also be present radially inside the receiving coils 16, which then have an opposite current direction than the radially outer transmitting coil 15. Only a subset of all pole pitches can be designed as coils 15,16, which is shown in the Fig. 7 can be seen.

[0049] In the shown embodiments of the Fig. 2-3, the rotor position sensor 9 is completely accommodated in the shaft opening 8 and the shaft opening 8 extends axially completely through the rotor shaft 6, so that the latter is designed as a hollow shaft.

[0050] Fig. Figure 3 shows an embodiment of the rotor position sensor 9, in which the sensor target 10 also has projections 19 extending radially inward beyond the shaft sections 12, so that in addition to a rotor position determination by the shaft sections 12 arranged radially outside the circuit board 13, a rotor position determination can also be carried out by the projections 19 axially spaced from the circuit board 13. In this case, at least one energizable transmitting coil and at least one receiving coil can be arranged along the end face of the circuit board 13 directed towards the projections 19. This can contribute to increasing the measurement accuracy or to providing a redundant rotor position sensor 9 without requiring additional installation space. As can be seen from the cross-sectional view of the Fig.As can be clearly seen in Figure 3, the projections 19 and the shaft sections 12 are designed like circular ring segments, have essentially identical center angles, and overlap essentially completely in the circumferential direction. This has particular manufacturing advantages, since the grooves 18 can then be milled from the rotor shaft 6 in one go.

[0051] If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a ranking. List of reference symbols 1 electric machine 2 Drivetrain 3 Motor vehicle 4 Stator 5 Rotor 6 Rotor shaft 7 Front side 8 shaft opening 9 Rotor position sensor 10 Sensor target 11 Shell surface 12 wave sections 13 Circuit board 14 Outer contour 15 Transmitting coil 16 Receiving coil 17 Shell surface 18 grooves 19 lead 20 area 21 area 22 Sensor arrangement 23 Orthogonal projection

Claims

[1] Sensor arrangement (22) comprising an inductive rotor position sensor (9), with at least one energizable transmitting coil (15) and one receiving coil (16), wherein the transmitting coil (15) spans a first surface (20) and the receiving coil (16) spans a second surface (21) parallel thereto or in the same plane as the first surface (20), wherein the sensor arrangement (22) further comprises a first sensor target (10) which is movable relative to the transmitting coil (15) and receiving coil (16) such that it is always located outside the first surface (20) and the second surface (21) and their orthogonal projections (23), wherein the sensor target (10) is arranged in a shaft opening (8) of a rotor shaft (6), wherein on an inner circumferential surface (11) of the shaft opening (8) shaft sections (12) are formed which extend radially inward and / or outward therefrom and form the sensor target (10) for the rotor position sensor (9). [2] Sensor arrangement (22) according to claim 1, wherein the first sensor target (10) is rotatable along a circular path around the transmitting coil (15) and the receiving coil (16). [3] Sensor arrangement (22) according to claim 1 or 2, wherein the rotor position sensor (9) engages in the shaft opening (8) in a rotationally stationary manner relative to the rotor shaft (6), [4] Sensor arrangement (22) according to one of the preceding claims, wherein the rotor position sensor (9) is at least partially traversed by the shaft sections (12) during rotation of the rotor shaft (6). [5] Sensor arrangement (22) according to one of the preceding claims, wherein the shaft sections (12) are formed integrally, in particular monolithically, with the rotor shaft (6). [6] Sensor arrangement (22) according to one of the preceding claims, wherein the rotor position sensor (9) has a circuit board (13) with a circular outer contour (14) which is received in the cylindrical shaft opening (8) with play and is traversed by the shaft sections (12) during rotation of the rotor shaft (6). [7] Sensor arrangement (22) according to claim 6, wherein the circuit board (13) carries the energizable transmitting coil (15) and the receiving coil (16). [8] Sensor arrangement (22) according to one of the preceding claims, wherein the shaft sections (12) comprise axially extending grooves (18) which are positioned distributed over the circumference of the inner circumferential surface (11). [9] Electric machine (1), in particular for a drive train (2) of a motor vehicle (3), comprising a stator (4) and a rotor (5) which is rotatable relative to the stator (4) and which is coupled in a torque-transmitting manner to a rotor shaft (6) which has a shaft opening (8) extending axially into the rotor shaft (6) from one of the end faces (7), wherein the electric machine (1) further comprises a sensor arrangement (22) by means of which the angular position of the rotor (5) can be determined via a sensor target (10) rotating with the rotor shaft (6), wherein the sensor arrangement (22) is designed according to one of claims 1-8. [10] Electrically operable drive train (2) of a motor vehicle (3) comprising an electric machine (1) according to claim 9.

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