DE102018213405A1 - Sensor system for determining a temperature and at least one rotational property of an element rotating about at least one axis of rotation - Google Patents

Abstract

A sensor system (110) for determining a temperature and at least one rotational property of an element (114) rotating about at least one rotational axis (112) is proposed. The sensor system (110) comprises at least one temperature sensor (128), which is set up to record at least one temperature of the rotating element (114), the temperature sensor (128) comprising an interrogation unit (138), an antenna (140) and a sensor element ( 142), wherein the interrogation unit (138) is set up to transmit an electrical transmission signal to the antenna (140) and to receive an electrical reception signal from the antenna (140), the antenna (140) for generating a surface wave in the sensor element ( 142) based on the transmission signal and for generating the reception signal based on a surface wave reflected in the sensor element (142), the reception signal being proportional to the temperature of the rotating element (114). The sensor system (110) further comprises at least one inductive position sensor (124), which is set up to record at least one piece of information about the rotational property of the rotating element (114). The sensor system (110) further comprises at least one evaluation unit (130), which is set up, at least one first signal (134), which has at least one item of information about the detected temperature, and at least one second signal (136), which has at least one item of information about which has the rotational property.

Description

State of the art

Numerous sensors are known from the prior art which detect at least one rotational property of rotating elements. Examples of such sensors are described in Konrad Reif (ed.): Sensors in a motor vehicle, 2nd edition, 2012, pages 63-74 and 120-129. For example, a position of a camshaft of an internal combustion engine relative to a crankshaft with a so-called phase generator can be determined by means of a Hall sensor.

For example, to implement traction in electric vehicles, either asynchronous machines or synchronous machines are often used, each of which consists of a stationary stator and a rotating rotor. The stator generally carries three winding strands, for example offset by 120 ° / p to one another, where p represents a number of pole pairs. In asynchronous machines, the rotor usually consists of electrically conductive rods which are short-circuited at the ends. When a rotor field rotates, a voltage can be induced in the rods, which causes a current to flow, which in turn builds up a counter-magnetic field and a rotational movement occurs. The induced voltage is zero if the rotor field and stator rotate at the same speed. There is a speed difference, which is called slip and which defines the torque of the motor. In synchronous machines, the rotor comprises a rotor which carries an excitation coil in which a direct current flows and generates a static magnetic field. Alternatively, a permanent magnet can be used as the rotor. It is then a permanently excited synchronous machine, which has a higher efficiency due to the powerless excitation and can therefore be more suitable for traction applications. In principle, a speed of the rotor can be identical to the speed of an excitation field. The torque can depend on a phase offset, that is to say an angular difference between the stator field and the rotor. In order to regulate the torque, control an inverter and provide stator coil signals accordingly, the speed of the rotor must be known for asynchronous machines and an absolute angular position of the rotor for synchronous machines. In both cases, synchronous machines and asynchronous machines, the direction of rotation must also be determined, in particular for reasons of functional safety. The maximum power of the machine can also be limited by a stator and rotor temperature.

To determine the rotor position, it is known to use so-called resolvers. This is an electromagnetic transmitter in which a rotor package is mounted on the shaft of the motor so that it does not rotate. An excitation coil and several receiver coils are mounted on a stator all the way round in a ring. An AC voltage signal is applied to the excitation coil and passes through the entire arrangement with an alternating electromagnetic field. Depending on the angle of rotation, a sinusoidal amplitude-modulated voltage can be induced in a first receiver coil, while a cosine-shaped amplitude-modulated voltage is induced in a second receiver coil. The provision of the excitation signal and the reading of the signals can be implemented within the power electronics or dedicated modules within a control unit for motor control. However, resolvers require a relatively large amount of installation space, require complex signal preparation and processing, and must be assembled with very low mechanical tolerances in order to achieve a sufficiently high level of accuracy. For these reasons, system costs can be correspondingly high. Furthermore, for reasons of space, it may not be possible to mount a redundant receiving coil system on the stator of the resolver in order to increase the availability of the sensor. A failure of the sensor can lead to the vehicle "stopping".

Due to the limited temperature resistance of the insulating varnish of the stator windings, the stator temperature can determine the maximum current in the stator coils, and thus the torque output. It is known to use a temperature sensor for determining the temperature, which is wound into the stator coils. A temperature distribution can be inferred from models. The rotor temperature, which can be critical especially with asynchronous machines because high currents flow in the squirrel-cage rotor, has not been determined so far and is only calculated using models. Above all, the lack of measurement information about the rotor temperature limits the performance of the electrical machine and makes modeling indispensable with the corresponding effort and inaccuracies, see DE 10 2014 213 103 , In the case of the permanently excited synchronous machine, too high a rotor temperature can lead to demagnetization of the permanent magnets. In the case of the asynchronous machine, the rotor temperature determines the quality of the torque accuracy.

Temperature sensors based on surface waves (SAW = surface acoustic waves) are also known. These are mainly used for temperature monitoring by High-voltage overhead lines are used because they can be read wirelessly and high temperature resolutions / accuracies are possible. The underlying measurement principle is based on the temperature dependence of the speed of sound.

Disclosure of the invention

In the context of the present invention, therefore, a sensor system for determining a temperature and at least one rotational property of an element rotating about at least one axis of rotation is proposed. In the context of the present invention, a “sensor” is basically understood to mean any device which is suitable for detecting at least one measurement variable. A “system” can be understood to mean any device that has at least two components. A sensor system for determining the temperature and the rotation property is accordingly understood to mean a sensor system which is set up to detect, for example measure, the at least one temperature and at least one rotation property and which, for example, can generate at least one electrical signal in accordance with the detected property, such as a voltage or a current. Combinations of properties can also be recorded. In the context of the present invention, a “rotation property” will basically be understood to mean a property that at least partially describes the rotation of the rotating element. This can be, for example, an angular velocity, a rotational speed, an angular acceleration, an angular position or another property which can at least partially characterize a continuous or discontinuous, uniform or non-uniform rotation or rotation of the rotating element. For example, the rotational property can be a position, in particular an angular position, a rotational speed, an angular acceleration or a combination of at least two of these quantities. Other properties and / or other combinations of properties can also be ascertainable. In the context of the present invention, an “angular position” is basically understood to mean an angle of rotation of a device capable of rotation, for example of the rotating element or of a sensor wheel, with respect to an axis perpendicular to the axis of rotation.

The sensor system can in particular be set up for use in a motor vehicle, in particular for traction applications for electrical machines. In the context of the present invention, a “rotating element” is basically understood to mean any element which rotates about at least one axis. For example, the rotating element can be a shaft, for example a shaft in a drive machine, for example a camshaft or a crankshaft. For example, an angular position of a camshaft or a rotational speed of a camshaft or an angular acceleration of a camshaft or a combination of at least two of these variables can be determined. Other properties and / or other combinations of properties can also be ascertainable.

The sensor system comprises at least one temperature sensor, which is set up to record at least one temperature of the rotating element. The temperature sensor has an interrogation unit, an antenna and a sensor element. The interrogation unit is set up to send an electrical transmission signal to the antenna and to receive an electrical reception signal from the antenna. The antenna is designed to generate a surface wave in the sensor element based on the transmission signal and to generate the reception signal based on a surface wave reflected in the sensor element. The received signal is proportional to the temperature of the rotating element.

The sensor system further comprises at least one inductive position sensor, which is set up to record at least one item of information about the rotational property of the rotating element. An “inductive position sensor” can in principle be understood in the context of the present invention to be any sensor that can generate information, in particular a signal, according to a detected property, in particular a measurement signal, in particular an electrical measurement signal, for example a voltage or a current, wherein the generation of the measurement signal is based on a change in a magnetic flux. In particular, the detected property can include a position, for example an angular position. In particular, the inductive position sensor can be an inductive magnetic sensor. In particular, the inductive position sensor can be an inductive rotor position sensor or rotor position sensor. However, other configurations are also possible in principle.

The sensor system further comprises at least one evaluation unit, which is set up to generate at least one first signal, which has at least one item of information about the detected temperature, and at least one second signal, which has at least one item of information about the rotation property. An “evaluation unit” can generally be understood to mean an electronic device which is set up to detach from the inductive Evaluate position sensor and / or signals generated by the temperature sensor. For example, one or more electronic connections between the inductive position sensor and / or the temperature sensor and the evaluation unit can be provided for this purpose. The evaluation unit can comprise, for example, at least one data processing device, for example at least one computer or microcontroller. The data processing device can have one or more volatile and / or non-volatile data memories, it being possible for the data processing device to be set up, for example, in terms of programming, in order to control the inductive position sensor. The evaluation unit can, for example, be constructed centrally or decentrally. Other configurations are also conceivable. The signal evaluation in the evaluation unit can take place in such a way that the evaluation unit evaluates all signals received by the temperature sensor and the inductive position sensor and converts them into two output signals, ie the first and the second signal. The first signal can represent the temperature, while the second signal represents the rotation property, for example the rotation rate. The first and the second signal can both be analog, both digital or one analog and one digital.

The interrogation unit can face the rotating element. This does not hinder the transmission and detection of the electrical signals to and from the antenna.

The interrogation unit and / or the antenna and / or the sensor element can be arranged on or within the inductive position sensor. This specifies a compact arrangement of the temperature sensor and the inductive position sensor.

The sensor element can have a generating element for generating the surface wave and at least one reflector, the generating element being produced from a piezoelectric material. Lithium niobate or lithium tantalate is preferably used here, since these materials have a high temperature coefficient and therefore the speed of the surface wave is maximally temperature-dependent. The surface wave can be generated by applying an electrical voltage to the generating element.

The generating element can be designed as an interdigital structure. By applying an electrical voltage, the generating element is temporarily partially braced (piezoelectric effect). The interdigital structure is preferably made of aluminum, since this material has low damping. Alternatively, all other electrically conductive materials are possible.

The sensor element can have several reflectors. The plurality of reflectors are preferably arranged at a distance from one another. This makes it possible to make statements about a temperature distribution.

The antenna can be electrically contacted with the sensor element. This facilitates signal transmission. The contacting can be realized directly or indirectly by means of further elements.

The antenna can be designed as a half-wave dipole antenna. The antenna can consist of one or more electrically conductive elements. These have to be adapted to the frequency of the system in order to ensure optimal transmission. Alternatively, the antenna can be designed as a spiral circular coil. For example, the antenna is implemented in the form of a planar, essentially spiral circular coil, such as, for example, in the case of RFID tags, which is implemented on a printed circuit board.

The inductive position sensor can have at least one circuit carrier. A “circuit carrier” can be understood to mean a device on which at least one electrical component can be arranged. The circuit carrier can be designed flexibly. In particular, the circuit carrier can comprise a flexible material. The circuit carrier can in particular be selected from the group consisting of: a printed circuit board, in particular a rigid-flex printed circuit board, for example a bent rigid-flex printed circuit board; a rigid circuit board, in particular a rigid circuit board with notches; a circuit board; a circuit board and a printed circuit, in particular a “printed circuit board” (PCB).

The circuit carrier can be arranged essentially coaxially to the axis of rotation. The circuit carrier can, for example, surround a sensor wheel or a circle segment of the sensor wheel of a sensor system described below in a substantially circular or circle segment shape. In the context of the present invention, the term “essentially circular” is basically understood to mean that the component described has a radius of curvature. The radius of curvature can vary within the component by a value from 0% to 80%, preferably from 0% to 50%, more preferably from 0% to 20% and particularly preferably from 0% to 5%. In particular, the radius of curvature can also be constant. Alternatively or additionally, the circuit carrier can also be composed of two or more segments which, for example, can each be flat or curved and which can be connected to one another, for example. The In total, segments can also be arranged coaxially to the axis of rotation, even if the individual segments are then arranged, for example, tangentially. Furthermore, the circuit carrier can be arranged in a housing, in particular in an injection molded housing.

The inductive position sensor can have at least one coil arrangement which is arranged on the circuit carrier. The coil arrangement can comprise at least one excitation coil and at least two receiver coils. In the context of the present invention, a “coil arrangement” can basically be understood to mean any device which comprises at least one coil. In the context of the present invention, a “coil” is basically understood to mean any component which has an inductance and is suitable for generating a magnetic field when current flows and / or vice versa. For example, a coil can comprise at least one completely or partially closed conductor loop or turn. In the context of the present invention, an “excitation coil” can in principle be understood as a coil that generates a magnetic flux when an electrical voltage and / or an electrical current is applied. The excitation coil can have at least one excitation turn. In the context of the present invention, a “receiver coil” is basically understood to be a coil which is set up to generate a signal based on an inductive coupling between the excitation coil and the receiver coil, which signal is dependent on the inductive coupling. For example, the coil arrangement can have a receiver coil system. In the context of the present invention, a “receiver coil system” can in principle be understood to mean any device which comprises at least two, preferably at least three, receiver coils.

The excitation coil can be essentially circular. With regard to the term “essentially circular”, reference is made to the above definition. The excitation coil and the receiver coils can be as in DE 10 2017 210 655.7 , submitted on June 23, 2017. The receiver coils can substantially completely revolve around the axis of rotation in a circumferential direction, each receiver coil being formed by a plurality of adjacent partial turns, with adjacent partial turns being oriented in opposite directions with respect to the current flow direction. In this case, each partial turn with respect to a radial direction, which extends outward from the axis of rotation, is formed from sections of at least two circular arcuate conductor tracks curved to the left and from sections of at least two circular arcuate conductor tracks curved to the right. All left-curved and all right-curved conductor tracks have the same radius of curvature. All left-curved conductor tracks and all right-curved conductor tracks extend between two concentric circles around the axis of rotation, a first circle with a first radius and a second circle with a second radius, with a third circle being located concentrically to the first circle and a third Radius, which results from the average of the first radius and the second radius, wherein a first right-hand curved conductor runs through three points: through a first point that lies on the first circle; by a second point that lies on the third circle and is circumferentially rotated by a quarter of the measuring range with respect to the first point; and by a third point that lies on the second circle and is rotated in the circumferential direction by half of the measuring range with respect to the first point. The further right-curved conductor tracks result from the tracking right-curved conductor track by rotating about the axis of rotation by half of the measuring range in the circumferential direction. The left-curved conductor tracks result from reflections of the right-curved conductor tracks in each case on a radial line which extends from the axis of rotation through the intersection of the respective right-curved conductor track with the third circle. A partial turn of a receiver coil can be defined as a part of the receiver coil that is surrounded by conductor tracks of the receiver coil that do not intersect one another. The orientation of a partial turn is determined by a current flow through the receiver coil. Counter-oriented partial windings each have a counter-current flow when the current flows through the receiver coil, i.e. with a partial winding with a first orientation the current runs clockwise or to the right through the partial winding, with a partial winding with a second, opposite orientation the current runs against the Clockwise or to the left through the partial turn. A partial turn can be constructed, for example, like a diamond with curved side surfaces. The four side surfaces of such a diamond can be formed, for example, by two sections of two left-curved conductor tracks and two right-curved conductor tracks. For example, the current direction in at least two sections of the left-curved conductor tracks, which form a partial turn, can be opposite to one another. Likewise, the current flow direction can be opposite to one another in at least two sections of the right-curved conductor tracks, which form a partial turn. The structure of the partial turns is to be understood in such a way that an imaginary straight line, which starts from the axis of rotation and runs in the radial direction, intersects an arcuate conductor track of the receiver coil that is curved to the left and to the right, when the straight line runs through the inside of the receiver coil. In this way it can also be achieved, for example, that the amplitude of the alternating voltage induced in the receiver coil or the measurement signal essentially depends on the angle of rotation as a sine function.

The inductive position sensor can comprise a number of n receiver coils, where n is a positive integer. The generated sinusoidal signals of the n receiver coils can be out of phase with one another. For example, adjacent sinusoidal signals can have a phase separation of 2π / (2n) and / or 360 ° / (2n) for n = 2. Furthermore, for example, adjacent sinusoidal signals can have a phase separation of 2π / (n) and / or 360 ° / (n) for n≥3. In particular, adjacent sinusoidal signals from exactly two receiver coils can have a phase separation of 90 °. In particular, adjacent sinusoidal signals from exactly three receiver coils can have a phase spacing of 120 °.

The inductive position sensor can have at least one application-specific integrated circuit (ASIC) which is arranged on the circuit carrier. An “application-specific integrated circuit” (ASIC) can be understood to mean any electronic circuit that is implemented as an integrated circuit.

The application-specific integrated circuit can be set up to provide an excitation signal for the excitation coil. The application-specific integrated circuit can be arranged on the circuit carrier and connected to exactly one excitation coil and at least two receiver coils. “Providing an excitation signal” can be understood to mean that the application-specific integrated circuit is set up to generate the excitation signal and / or that the application-specific integrated circuit is set up to apply the excitation signal to the excitation coil. In the context of the present invention, an “excitation signal” can be understood to mean an electrical signal, in particular at least one alternating voltage and / or at least one alternating current. The excitation signal can be a substantially sinusoidal excitation signal. In the context of the present invention, “sinusoidal” is understood in principle to mean any shape which has a course of a sine curve. For example, a course of a complete sine curve can be included or only part of a sine curve. “Essentially sinusoidal” can be understood to mean embodiments with a completely sinusoidal course, deviations being conceivable which are not more than 20%, in particular not more than 10% or even not more than 5%, of the absolute value of the sinusoidal shape. A “complete sinus curve” can in particular be understood to mean a course of a sinus curve which comprises at least one period. The sine curve can start at the zero point or any other point on the sine curve. The sinusoidal shape can also be composed, for example, in sections from other functions, so that an approximate sinusoidal shape results overall. The excitation signal can have an amplitude in the range from 0.1 V to 10 V, preferably from 5 V. The excitation signal can have a frequency in the range from 1 MHz to 10 MHz, preferably 3.5 MHz. The application-specific integrated circuit can have at least one oscillator circuit. The oscillator circuit can drive an LC oscillator, for example, in which the excitation coil and a capacitor act as frequency-determining elements. By applying the excitation signal to the excitation coil, an alternating electromagnetic field can arise which couples into the receiver coils and induces, for example, corresponding alternating voltages and / or alternating currents. The inductive position sensor can be set up to detect an inductive coupling and / or a change in an inductive coupling between the excitation coil and the at least one receiver coil. The excitation coil can be configured to generate an alternating electromagnetic field in response to the application of the excitation signal. The excitation coil and the receiver coils can be coupled such that the alternating electromagnetic field induces an alternating voltage in the receiver coils. The receiver coils can be arranged in such a way that the receiver coils generate rotation angle-dependent signals when the rotating element rotates at a constant angular velocity about the axis of rotation.

The application-specific integrated circuit can be set up to process signals generated by the receiver coils and to provide them as at least one first output signal at at least one first output and at least one second output signal at at least one second output. The designation as "first" and "second" output signal are to be understood as pure designations and in particular do not provide any information about a sequence or whether there are further output signals. “Processing” can basically be understood to mean any operation of signal processing in order to generate an output signal, for example evaluation, filtering, demodulation. The signal processing can be digital and / or analog. The signal processing can preferably be pure done analogously. The application-specific integrated circuit can, in particular, be set up to infer an amount and a phase of the coupling by demodulating a signal induced in the receiver coils with a carrier signal, that is to say a signal from the excitation coil. The amount can in particular vary continuously with the angle of rotation. A phase position can be 0 ° or 180 °, for example. The application-specific integrated circuit can have at least one demodulation device which is set up to demodulate the signals of the receiver coils, in particular synchronously. The demodulation can include multiplying by the excitation signal. For example, multiplying the amount by a cosine function can result in a preferably offset-free Sin / Cos system, in particular when using two receiver coils with a 90 ° phase offset in relation to the measuring range. When using three receiver coils with a typically 120 ° phase offset in relation to the measuring range, a three-phase sine signal can arise in particular, which can be converted into a Sin / Cos system, for example, by using the Clarke transformation. With the help of the arctangent function, the angle of rotation can then be deduced. The application-specific integrated circuit can have at least one low-pass filter. The low-pass filter can have a cut-off frequency in the range from 50 kHz to 500 kHz, preferably 100 kHz. The lower limit frequency can be significantly lower, since only offsets are to be compensated, so that, for example, 0.1 Hz would be sufficient. For example, the application-specific integrated circuit can first demodulate the signals of the receiver coils and then filter using the low-pass filter. The application-specific integrated circuit can have at least one amplifier. The amplifier can be set up to amplify the signals of the receiver coils, in particular the filtered signals. “Amplification” can be understood to mean an increase in the amplitude of a signal. The application-specific integrated circuit can also be set up to apply a DC (direct current) offset to the signals of the receiver coils. The first output signal and the second output signal can be transmitted from the first and second outputs, for example via at least one electrical signal line, in particular a cable, to a second evaluation unit, in particular an evaluation unit designed separately from the circuit carrier.

The sensor system can have at least one sensor wheel that can be connected to the rotating element. In the context of the present invention, a “transmitter wheel” can basically be understood to mean any component that can be connected to the rotating element and that is set up to cause at least one measurable signal, in particular a magnetic field change, per revolution of the rotating element when connected to the rotating element. The sensor wheel can, for example, be permanently or reversibly connected or connectable to the rotating element or can also be formed in one piece with the rotating element or integrated into the rotating element. The sensor wheel can have a sensor wheel profile. In the context of the present invention, a “transmitter wheel profile” can in principle be understood to mean an entirety of profile elements and of spaces that are arranged between the profile elements. In the context of the present invention, a “profile element” of the sensor wheel can basically be understood to mean any shape of the contour of the sensor wheel, in particular a bulge, for example a pin-shaped, a tooth-shaped or a tooth-shaped bulge, or an indentation or a recess, for example a hole.

The sensor wheel can, for example, be designed to “shade” areas of a receiver coil structure depending on its position. As a result, a coupling between a transmitter coil structure and the receiver coils can be influenced as a function of the angle of rotation. A typical range of values for a coupling factor can be, for example, -0.3 to +0.3. A coupling factor can in particular be understood to mean an amplitude ratio between a received signal and a transmitted or excitation signal. The coupling factor can in particular run sinusoidally with the angle of rotation.

The coil arrangement can surround the sensor wheel or at least one circle segment of the sensor wheel essentially in the form of a segment of a circle or in a circle. In particular, the coil arrangement, in particular the coil arrangement arranged on the circuit carrier, can cover at least one profile element and at least one intermediate space between two profile elements of the sensor wheel in at least one angular position of the sensor wheel.

The encoder wheel can be designed to be rotationally symmetrical. The sensor wheel can have an identical number of electrically conductive blades and electrically non-conductive or less conductive blades and / or recesses. The electrically conductive wings can have a first opening angle α and the electrically non-conductive or less conductive wings and / or the cutouts can have a second opening angle β. A sum of the first and the second opening angle can correspond to a full angle measuring range of the inductive position sensor. The first and the second opening angle can be identical or different. The The encoder wheel can be attached to the rotating element by means of a screw and / or adhesive connection.

The evaluation unit can be set up to infer an angular position Φ of the sensor wheel from signals from the receiver coils. The sensor system, in particular the inductive position sensor, can be set up to detect an inductive coupling and / or a change in an inductive coupling between the excitation coil and the at least one receiver coil. In particular, the sensor system can be set up to detect the inductive coupling caused by a movement and / or a position of the transmitter wheel and / or the change in the inductive coupling caused by a movement and / or a position of the transmitter wheel between the excitation coil and the receiver coils. The sensor system can in particular be set up to determine an absolute or relative angular position of the rotating element from the change in the inductive coupling caused by the movement and / or by a position of the sensor wheel between the excitation coil and the receiver coils. A “relative angular position” can basically be understood to mean a position with respect to a period defined by the receiver coils. In particular, the second evaluation unit can be set up to generate at least one quotient signal of at least two signals from at least two receiver coils. For example, the law tanΦ = sinΦ / cosCD can be used to calculate the angular position Φ from two signals generated by two receiver coils. For example, the Clarke transformation can be used to calculate the angular position Φ from three signals generated by three receiver coils. In particular, the evaluation unit can have at least one evaluation circuit. In particular, the evaluation circuit can be set up to evaluate the signals of the position sensor. The evaluation circuit can be, for example, a processor. The evaluation unit can in particular be configured separately from the circuit carrier and can be connectable to the circuit carrier via at least one connection, for example a cable. The inductive position sensor can be set up to transmit the first and the second output signal to the evaluation unit.

• Erfassen mindestens einer Temperatur des rotierenden Elements mit dem mindestens einen Temperatursensor,
• Aussenden eines elektrischen Sendesignals an die Antenne,
• Erzeugen einer Oberflächenwelle in dem Sensorelement mittels der Antenne,
• Erzeugen des Empfangssignals basierend auf einer in dem Sensorelement reflektierten Oberflächenwelle mittels der Antenne,
• Empfangen eines elektrischen Empfangssignals von der Antenne mittels der Abfrageeinheit, wobei das Empfangssignal proportional zur Temperatur des rotierenden Elements ist,
• Erfassen mindestens einer Information über eine Rotationseigenschaft des rotierenden Elements mit dem mindestens einen induktiven Positionssensor;
• Erzeugen mindestens eines ersten Signals, welches mindestens eine Information über die erfasste Temperatur aufweist, und mindestens eines zweiten Signals,
• welches mindestens eine Information über die Rotationseigenschaft des rotierenden Elements aufweist, mit mindestens einer Auswerteeinheit.

In a further aspect of the present invention, a method for determining at least one temperature and at least one rotational property of an element rotating about at least one axis of rotation is proposed. The method comprises the use of at least one sensor system. The method comprises the following steps, preferably in the order given. In addition to the method steps mentioned, the method can also comprise further method steps. The process steps are:

• Detecting at least one temperature of the rotating element with the at least one temperature sensor,
• Sending an electrical transmission signal to the antenna,
• Generating a surface wave in the sensor element by means of the antenna,
• Generating the received signal based on a surface wave reflected in the sensor element by means of the antenna,
• Receiving an electrical reception signal from the antenna by means of the interrogation unit, the reception signal being proportional to the temperature of the rotating element,
• Detecting at least one piece of information about a rotational property of the rotating element with the at least one inductive position sensor;
• Generating at least one first signal, which has at least information about the detected temperature, and at least one second signal,
• which has at least one piece of information about the rotational property of the rotating element, with at least one evaluation unit.

The method is carried out using a sensor system according to the present invention, that is to say according to one of the above-mentioned embodiments or according to one of the embodiments described in more detail below. Accordingly, reference can largely be made to the description of the sensor system for definitions and optional configurations. However, other configurations are also possible in principle.

Furthermore, a computer program is proposed within the scope of the present invention, which executes the method according to the invention in one of its configurations when it runs on a computer or computer network. Furthermore, in the context of the present invention, a computer program with program code means is proposed in order to carry out the method according to the invention in one of its configurations when the program is executed on a computer or computer network. In particular, the program code means can be stored on a computer-readable data carrier. In addition, in the context of the present invention, a data carrier is proposed on which a data structure is stored, which after loading into a working and / or main memory of a computer or computer network, the inventive method in can perform one of its configurations. In the context of the present invention, a computer program product with program code means stored on a machine-readable carrier is also proposed in order to carry out the method according to the invention in one of its configurations when the program is executed on a computer or computer network. A computer program product is understood to mean the program as a tradable product. In principle, it can be in any form, for example on paper or a computer-readable data carrier, and can in particular be distributed over a data transmission network. Finally, within the scope of the present invention, a modulated data signal is proposed, which contains instructions that can be executed by a computer system or computer network for executing a method according to one of the described embodiments.

Advantages of the invention

The proposed device and the proposed method have numerous advantages over known devices and methods. In particular, it is possible to provide an inexpensive sensor concept for temperature measurement up to high temperatures of more than 400 ° C. and determination of further mechanical variables. For example, a spatially resolved temperature measurement is possible. No active components are required on a hot rotor, which increases the reliability of the system. No energy source is required for the temperature sensor, since it works purely passively. A directly measured rotor speed can be used to check the plausibility of successive rotor position measurements and thus increase functional safety. Condition monitoring of the rotor or the bearing, vibration, unbalance may be possible. The high cut-off frequency of photodiodes enables rapid measurement and detection of dynamic changes. The measuring principle according to the invention for detecting the angle of rotation further branches no influence of external magnetic fields, for example as a result of high currents within cables which are arranged near the sensor. The measuring principle according to the invention for detecting the angle of rotation is practically not speed-limited due to a high carrier frequency.

list of figures

Further optional details and features of the invention result from the following description of preferred exemplary embodiments, which are shown schematically in the figures.

• 1 eine schematische Darstellung eines erfindungsgemäßen Sensorsystems gemäß einer Ausführungsform;
• 2 schematische Darstellung eines Temperatursensors;
• 3 eine schematische Darstellung einer Antenne und eines Sensorelements des Temperatursensors;
• 4 ein Ausführungsbeispiel eines Geberrads;
• 5 einen erfindungsgemäßen Aufbau eines ASICs und Weiterverarbeitung der Signale des induktiven Positionssensors und
• 6 Signalformen des erfindungsgemäßen Sensorsystems.

Show it:

• 1 a schematic representation of a sensor system according to the invention according to one embodiment;
• 2 schematic representation of a temperature sensor;
• 3 a schematic representation of an antenna and a sensor element of the temperature sensor;
• 4 an embodiment of a sensor wheel;
• 5 an inventive structure of an ASIC and further processing of the signals of the inductive position sensor and
• 6 Signal forms of the sensor system according to the invention.

Embodiments of the invention

1 shows a schematic representation of a sensor system according to the invention 110 according to one embodiment. The sensor system 110 is set up to determine at least one rotational property about at least one axis of rotation 112 rotating element 114 , The sensor system 110 can in particular be set up for use in a motor vehicle. In particular, the sensor system 110 be set up to detect at least one rotational property of a camshaft. For example, the sensor system 110 be set up to detect an angular position of the camshaft. Accordingly, the rotating element may 114 for example, a wave. In the illustrated case of a permanently excited synchronous machine, the shaft can be a permanent magnet 116 wear. Cylindrical around this permanent magnet 116 can a stator coil package 118 be arranged. An output can be arranged in the negative z direction and is not shown further. On the opposite side of the output there can be a B-bearing 120 be arranged, which is the axis 114 receives. The B camp 120 can with a B-end shield 122 be connected. The sensor system 110 has at least one inductive position sensor 124. The inductive position sensor 124 can have at least one circuit carrier 125 include. The circuit carrier 125 can have, for example, a printed circuit board, which essentially has the rotating element in a circular shape 114 rotates and preferably covers an angular range of 360 °. The B camp 120 can with the B-end shield 122 be connected, which is the inductive position sensor 124 holds. The sensor system 110 has at least one with the rotating element 114 connectable encoder wheel 126 on. Between B-bearings 120 and inductive position sensor 124 can the encoder wheel 126 be arranged, which is connected to the shaft and rotates with it. The inductive position sensor 124 can have packaging. The packaging can allow the inductive position sensor 124 to be provided with chip protection and to ensure a sufficiently high mechanical strength. The packaging can be realized by one or more of the methods direct injection molding, transfer molding with thermoset, thermoplastic injection molding or by casting. The packaging can contain all components of the inductive position sensor 124 completely or partially surrounded. The packaging can have at least one connecting element, preferably bores and / or recesses, through which the inductive position sensor 124 , for example with a screw connection on the B-end shield 122 can be attached. Alternatively or additionally, the inductive position sensor 124 also with clips, an adhesive connection or other processes on the B-end shield 122 be attached. In principle, the structure can also be attached on the other side (A-bearing).

The sensor system 110 also has at least one temperature sensor 128 which is set up, at least one temperature of the rotating element 114 capture. For example, the temperature sensor 128 be set up to temperatures of the rotating element 114 and / or the encoder wheel 126 and / or the permanent magnet 116 , capture. It can be assumed that the rotor temperature is identical to the temperature of the sensor wheel 126 or the wave.

The sensor system 110 has at least one evaluation unit 130 on. For example via a cable 132 can the inductive position sensor 124 with the evaluation unit 130 be connected. The evaluation unit 130 can be a power supply for the inductive position sensor 124 provide. The evaluation unit 130 can output signals of the inductive position sensor 124 received and calculate a rotor position and rotor temperature from these. The inductive position sensor 124 can have at least one contact element on which the cable 132 can be attached. The contact element can be a hole for ram contacts, a soldered plug or pads with which the cable 132 with the circuit carrier 125 can be connected by a soldering process.

The evaluation unit 130 is set up, at least a first signal 134 , which has at least one item of information about the detected temperature, and at least one second signal 136 which has at least one item of information about the rotational property. For example, one or more electronic connections between the evaluation unit can be used for this purpose 130 and the temperature sensor 128 and / or the inductive position sensor 124 be provided. The evaluation unit 130 can for example comprise at least one data processing device, for example at least one computer or microcontroller. The data processing device can have one or more volatile and / or non-volatile data memories, wherein the data processing device can be set up, for example in terms of programming, around the inductive position sensor 124 head for. The signal evaluation in the first evaluation unit 130 can be done in such a way that the evaluation unit 130 all from the temperature sensor 128 and the inductive position sensor 124 received signals and evaluated into two output signals, i.e. the first signal 134 and the second signal 136 , changes. The first signal 134 can represent the temperature during the second signal 136 represents the rotation property, for example the rotation rate. The first signal 134 and the second signal 136 can both be analog, both digital or one analog and one digital.

2 shows a schematic representation of the temperature sensor 128 , The temperature sensor 128 assigns a query unit 138 , an antenna 140 and a sensor element 142 on. The query unit 138 is set up to send an electrical transmission signal to the antenna 140 and for receiving an electrical reception signal from the antenna 140 , The antenna is for generating a surface wave in the sensor element 142 based on the transmission signal and for generating the reception signal based on one in the sensor element 142 reflected surface wave set up. The received signal is proportional to the temperature of the rotating element 114 , The query unit is according to the invention 138 spatially from the antenna 140 and the sensor element 142 separately and preferably part of the inductive position sensor 124 , The antenna 140 and the sensor element 142 are on the rotating element 114 attached as in 1 is shown. The antenna 140 and the sensor element 142 can alternatively on the encoder wheel 126 be arranged. The query unit 137 is the rotating element 114 facing. The query unit 138 and / or the antenna 140 and / or the sensor element 142 are on or inside the inductive position sensor 124 arranged.

3 shows a schematic representation of an antenna 140 and a sensor element 142 of the temperature sensor 128 , The sensor element 142 has a generating element 144 to generate the surface wave. The generating element 144 is made of a piezoelectric material that can be crystalline. Lithium niobate or lithium tantalate is preferably used here, since these materials have a high temperature coefficient and therefore the speed the surface wave is maximally temperature-dependent. The generating element 144 is designed as an interdigital structure. The wave can be generated, for example, by the generation element 144 is temporarily tensioned by applying an electrical voltage. The interdigital structure, which is preferably made of aluminum, is preferably used for this purpose, since this material has low damping. Alternatively, all other electrically conductive materials are possible. The voltage is across two contacts 146 . 148 fed. It has a frequency in the range of a few hundred kHz to a few GHz and amplitudes in the range of a few mV to a few V, for example 100 mV to 10 V. The amplitude and / or frequency can be constant over time or variable over time depending on the concept of the interrogation unit 138 , It now spreads in the positive x-direction of a wave along the surface of the crystal and penetrates into the material about half a wavelength deep. On one or more reflectors 150 of the sensor element 142 , which consist of electrically conductive material and can consist essentially of interconnect pieces with an extension along the y-axis or in turn of interdigital structures, at least parts of the original surface wave are reflected and run back in the negative x direction until they are in the interdigital structure of the generating element 144 generate an electrical signal, which on the contacts 146 . 148 can be tapped. The amplitude and / or the phase of the signal depends on the signal transit time, which, in addition to the distance between the reflector 148 and interdigital structure of the generating element 144 , depends on the speed of the surface wave. Since this decreases linearly with increasing temperature in a first approximation, a temperature measurement is possible in this way. When arranging several reflectors 148 statements about a temperature distribution can also be made.

Both the feeding in of a voltage for generating the surface wave and the reading back of the electrical signals, ie the received signals, as a result of the reflected wave for temperature calculation, are carried out via the antenna 140 , which consists of one or more electrically conductive elements 152 can exist. These have to be adapted to the frequency of the system in order to ensure optimal transmission. For example, implementation as a λ / 2 dipole antenna with two connections is possible 154 . 156 which directly or via further elements (not shown) with the contacts 146 . 148 of the interdigital structure. Alternatively, the antenna 140 can also be implemented in the form of a planar, essentially spiral circular coil which is implemented on a printed circuit board.

The query unit 138 is used to send an electrical transmission signal to the antenna 140 and receiving the received signal from the antenna. The signals are high-frequency signals. Here, a concept from radar technology can be adapted, such as FMCW radar (FMCW - frequency modulated continuous wave). In principle, a high-frequency AC voltage signal is generated and measured back in order to determine phase and / or / amplitude relationships from the comparison of the signals and to calculate the temperature therefrom.

The signals of the interrogation unit 138 are either directly through separate lines in the cable 132 to the evaluation unit 130 guided or preferably by means of an evaluation circuit, which is part of the inductive position sensor 124 is processed and then via a suitable interface, which can be digital or analog, to the evaluation unit 130 transfer.

4 shows an encoder wheel 126 in the first embodiment. The plan view of the axis from the direction of the inductive position sensor is shown 124 , The encoder wheel 126 can be designed rotationally symmetrical. The encoder wheel 126 can have an identical number of electrically conductive wings 158. with a first opening angle α and electrically non or less conductive wings and / or recesses 160 have a second opening angle β. A sum of the first and the second opening angle can cover a full angle measuring range δ of the inductive position sensor 124 correspond. The first and the second opening angle can be identical or different in size. An embodiment with α = β can be preferred, where α corresponds to half the angle measurement range δ. In a further embodiment, α can also be smaller as long as the condition α + β = δ is fulfilled. The angle measuring range can correlate with a number of pole pairs of the synchronous machine p according to δ = 360 ° / p and for the number n of the electrically conductive blades 158. can apply: n = p = 360 ° / δ. The attachment of the encoder wheel 126 on the rotating element 114 can be done via a screw and / or adhesive connection and / or with a longitudinal pressing process.

The inductive position sensor 124 can at least one application-specific integrated circuit (ASIC) 162 have which in 5 is shown.

5 shows an inventive structure of the ASIC 162 and further processing of the signals of the inductive position sensor 124 , The inductive position sensor 124 can have at least one coil arrangement 164 which on the circuit board 125 is arranged. The coil arrangement 164 can have at least one excitation coil 166 and at least two receiver coils 168 exhibit. The application specific integrated circuit 162 is set up to provide an excitation signal for the excitation coil 166 provide. The application specific integrated circuit 162 can be set up by the receiver coils 168 to process generated signals and as output signals, for example the evaluation unit 130 to provide. For example, the ASIC 162 exactly to an excitation coil 166 and at least two receiver coils 168 be connected. With a block, not shown 170 can be a substantially sinusoidal excitation signal 172 are provided, which is the excitation coil 166 fed. For example, the block 170 are an oscillator circuit which drives an LC oscillator in which the excitation coil 166 and at least one capacitor, not shown, act as frequency-determining elements. The amplitude of the excitation signal 172 can be in the range from 0.1 V to 10 V, preferably 5 V, at frequencies in the range from 1 MHz to 10 MHz, preferably 3.5 MHz.

The application specific integrated circuit 162 can be set up by the receiver coils 168 generated signals 174 . 176 to process The application-specific integrated circuit 162 can have at least one demodulation device 178 which is set up to receive the signals 174 . 176 the receiver coils 168 to demodulate, especially synchronously. Demodulation can be multiplied by the excitation signal 172 include. The application specific integrated circuit 162 can have at least one low pass filter 180 exhibit. The low pass filter 180 can have a cut-off frequency in the range from 50 kHz to 500 kHz, preferably 100 kHz. For example, the application specific integrated circuit 162 first the signals 174 . 176 the receiver coils 168 demodulate and then using the low pass 180 filter. The application specific integrated circuit 162 can still have at least one amplifier 182 exhibit. The amplifier 182 can amplify the filtered signals. Optionally, it is also possible to apply a DC offset to them. The application specific integrated circuit 162 can be set up to process the signals as at least a first output signal 184 at at least one first exit 186 and at least a second output signal 188 at at least one second exit 190 provide. The first output signal 184 and the second output signal 188 can over the cable 132 to the evaluation unit 130 be transmitted. The query unit 138 provides an output signal 192 which contains digital or analog temperature information and which directly with the evaluation unit 130 is contacted or which is further processed, such as with a microcontroller, not shown.

Exemplary signal profiles as a function of the angle of rotation for a continuous rotary movement are shown in 6 shown. With the inventive design of the receiver coils 168 and the encoder wheel 126 a demodulated sinusoidal signal results as a function of the angle of rotation 188 and a demodulated cosine signal 184 , In the evaluation unit 130 can the signals 184 . 188 be digitized and then converted into the angle of rotation by subsequently calculating an arctangent.

Although the elements of the inductive position sensor 124 separate from the interrogation unit 138 mixing is also possible. For example, the excitation coil 166 also for communication with the antenna 140 of the temperature sensor 128 be used.

Alternatively or in addition to signal processing of the first signal 134 and second signal 136 in the inductive position sensor 124 can preprocessing already in the temperature sensor 128 itself and / or in the evaluation unit 130 respectively. So the application-specific integrated circuit 162 have at least one switching element. The inductive position sensor 124 can have at least one control unit, which is set up to control the switching element, such that, in the event of an error, a signal chain of the application-specific integrated circuit 162 to the first and the second exit 186 . 190 is interrupted and the first and the second output 186 . 190 be overwritten with at least one error signal. The switching element can in particular have a switch. In order to be able to react quickly in the event of a fault, for example a runaway of the engine, that is to say the uncontrollable increase in the speed, it may be advantageous to process the signal not only in the second evaluation unit 130 make. If an error is detected, it may be possible to have an “interrupt” via the output signals 184 . 188 of the inductive position sensor 124 make. The control unit can be set up to control the switching element and, in the event of a fault, the signal chain of the inductive position sensor via the switching element 124 to interrupt and the first and second outputs 186 . 190 to overwrite each with the at least one error signal. For this purpose, the error signal can assume values which are not in the otherwise valid signal range of the signals of the usual first and second output signals 184 . 188 of the ASIC 162 , lie. For example, the error signal for the first and the second output 186 . 190 assume identical values, which are either maximum or minimum, based on the available voltage swing. In this case, the otherwise valid trigonometric relationship sin ² + cos ² = 1 is no longer valid and the evaluation unit 130 can put the machine in a safe state, e.g. an active short circuit. In this way, functional safety can be significantly increased. In principle, mixed forms of the described embodiments can also be implemented. It is conceivable, for example, that the temperature via an interface to the evaluation unit 130 is sent while the mechanical quantity is preprocessed and the signals of the inductive position sensor only when a certain condition occurs 124 overrides.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102014213103 [0004]
• DE 102017210655 [0021]

Claims (14)

Sensor system (110) for determining a temperature and at least one rotational property of an element (114) rotating about at least one rotational axis (112), comprising: at least one temperature sensor (128) which is set up detect at least one temperature of the rotating element (114), wherein the temperature sensor (128) has an interrogation unit (138), an antenna (140) and a sensor element (142), the interrogation unit (138) being set up for transmitting an electrical transmission signal to the antenna (140) and for receiving an electrical reception signal from the antenna (140), the antenna (140) being set up to generate a surface wave in the sensor element (142) based on the transmission signal and to generate the reception signal based on a surface wave reflected in the sensor element (142), the received signal being proportional to the temperature of the rotating element (114), at least one inductive position sensor (124), which is set up to detect at least one item of information about the rotational property of the rotating element (114), at least one evaluation unit (130) which is set up, at least one first signal (134) which has at least one item of information about the detected temperature, and at least one second signal (136), which has at least one item of information about the rotational property. Sensor system (110) according to Claim 1 , wherein the interrogation unit (138) faces the rotating element (114). Sensor system (110) according to Claim 1 or 2 , wherein the interrogation unit (138) and / or the antenna (140) and / or the sensor element (142) is arranged on or within the inductive position sensor (124). Sensor system (110) according to one of the Claims 1 to 3 , further comprising at least one sensor wheel (126) which can be connected to the element (114) rotating about the axis of rotation (112). Sensor system (110) according to one of the Claims 1 to 4 , wherein the sensor element (142) has a generating element (144) for generating the surface wave and at least one reflector (150), wherein the generating element (144) is made of a piezoelectric material. Sensor system (110) according to Claim 5 , wherein the generating element (144) is designed as an interdigital structure. Sensor system (110) according to Claim 5 or 6 , wherein the sensor element (142) has a plurality of reflectors (150). Sensor system (110) according to one of the Claims 1 to 7 , wherein the antenna (140) is electrically contacted with the sensor element (142). Sensor system (110) according to one of the Claims 1 to 8th , wherein the antenna (140) is designed as a half-wave dipole antenna or as a spiral circular coil. Sensor system (110) according to one of the Claims 1 to 9 , wherein the inductive position sensor (124) has at least one circuit carrier (125) and at least one coil arrangement (164) which is arranged on the circuit carrier (125), the coil arrangement (164) at least one excitation coil (166) and at least two receiver coils ( 168). Sensor system (110) according to Claim 10 , wherein the inductive position sensor (124) has at least one application-specific integrated circuit (ASIC) (162) which is arranged on the circuit carrier (125), the application-specific integrated circuit (162) being set up to detect the signals from the receiver coils (166) to process generated signals (174, 176) and to provide them as at least one first output signal (182) to at least one first output (184) and as at least one second output signal (186) to at least one second output (188). Sensor system (110) according to Claim 11 , wherein the application specific integrated circuit (162) is arranged to provide an excitation signal (172) for the excitation coil (166), the excitation signal (172) being a substantially sinusoidal excitation signal, the excitation signal (172) having an amplitude in the range of 0.1 V to 10 V, wherein the excitation signal (172) has a frequency in the range of 1 MHz to 10 MHz. Sensor system (110) according to one of the Claims 1 to 12 , wherein the inductive position sensor (124) is an inductive rotor position sensor. Method for determining at least one temperature and a rotational property of an element (114) rotating about at least one axis of rotation (112), the method comprising the use of at least one sensor system (110) according to one of the preceding claims, the method further comprising the following steps: detecting at least one temperature of the rotating element (114) with the at least one temperature sensor (128), sending an electrical transmission signal to the antenna (140), generating a surface wave in the sensor element (142) by means of the antenna (140), generating the received signal based on a surface wave reflected in the sensor element (142) by means of the antenna (140), receiving an electrical received signal from the antenna (140) by means of the interrogation unit (138), the received signal being proportional to the temperature of the rotating one Element (114), detecting at least one item of information about a rotational property of the rotating element (114) with the at least one inductive position sensor (124); Generating at least one first signal (134), which has at least one piece of information about the detected temperature, and at least one second signal (136), which has at least one piece of information about the rotating property of the rotating element (114), with at least one evaluation unit (130) ,

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