Cooling device for cooling power electronics by means of a coolant, as well as power electronics equipped with such a cooling device

Abstract

The invention relates to a cooling device (10) for cooling power electronics (1), comprising a heat sink (12) that can be brought into thermal contact with the power electronics (1) and in which a coolant channel (14) through which a coolant flows is formed. In order to enable the detection of both the flow rate (F) and the temperature (T) of the coolant in the coolant channel (14) during such cooling, a detection device (20) is provided according to the invention, which is configured to generate first ultrasonic pulses and measure a first transit time (t1) of these first ultrasonic pulses traveling in the coolant channel (14) along a first upstream path (P1); to generate second ultrasonic pulses and measure a second transit time (t2) of these second ultrasonic pulses traveling in the coolant channel (14) along a second downstream path (P2);to determine the flow rate (F) based on an evaluation of the first transit time (t1) and the second transit time (t2); and to determine the temperature (T) based on an evaluation of the first and / or second transit time (t1, t2) and / or based on a measurement and evaluation of a waveform of the first and / or second ultrasound pulses at the end of the relevant path (P1, P2).

Description

[0001] The present invention relates to a cooling device according to the preamble of claim 1 for cooling power electronics (e.g., inverters) using a coolant. Furthermore, the invention relates to a method for detecting a flow rate and a temperature of a coolant flowing in such a cooling device, as well as to power electronics equipped with such a cooling device.

[0002] For example, cooling devices for cooling inverters for converting direct current to alternating current are known from the prior art in the automotive sector (e.g., relating to electric vehicles). These cooling devices comprise a heat sink in thermal contact with the inverter, in which a coolant channel through which a coolant can flow is formed. Furthermore, this type of cooling is used, for example, for cooling electrical energy storage devices (e.g., the traction battery of an electric vehicle).

[0003] The coolant in question (e.g. water, water-glycol mixture, etc.) can be circulated in a cooling circuit, for example, by a coolant pump generating a coolant flow in the cooling circuit, which is guided, among other things, through the coolant channel formed in the heat sink. The heat sink can be housed together with a power electronic circuit arrangement (power electronics), for example in an electronics module. Due to thermal contact with the circuit arrangement, the coolant flowing through the coolant channel absorbs heat from the circuit arrangement. This heat can be released again by the coolant further along the cooling circuit or by a return of the coolant to the coolant pump, for example at a heat exchanger (radiator), either to the ambient air, or alternatively, for example to a coolant in a secondary cooling circuit.

[0004] The cooling performance achieved with this type of known cooling is influenced, on the one hand, by the geometric and material conditions or the resulting heat transfer resistance between the power electronics (heat source) and the coolant (heat sink) in the cooling channel, and, on the other hand, by the temperature difference between the power electronics and the coolant flowing in the cooling channel. In order to maintain such a required temperature difference for a specific required cooling performance, the coolant must flow through the coolant channel at a specific flow rate to avoid excessive heating. Otherwise, if the flow rate and / or the coolant temperature are too low, there is a risk of insufficient cooling and, consequently, excessive heating of the power electronics.

[0005] Against this background, in many cooling applications of the type described above, there is a desire to record the flow rate and temperature of the coolant in the cooling channel during cooling operation.

[0006] In particular, information about the flow rate and temperature of the coolant can be used advantageously to increase the fault tolerance and performance characteristics of the power electronics in question.

[0007] It is known from the prior art to estimate the coolant flow rate from the coolant temperature using a previously determined relationship (e.g., using a lookup table), but this represents a very inaccurate determination of the flow rate. Furthermore, it is known, for example, to determine the coolant flow rate from the operating parameters of a coolant pump control system, which is also relatively inaccurate.

[0008] In the current state of the art, the coolant temperature is often determined using NTC / PTC temperature sensors. However, this can lead to inaccurate temperature readings, for example, if the sensors are installed in an unfavorable position. Furthermore, such sensors often have relatively long response times.

[0009] A thermal model is often used in the control or regulation of power electronics. This model limits the electrical output of the power electronics when necessary (e.g., due to the risk of excessive heating of the power electronics). Such a model requires the most current and accurate measured values ​​for the flow rate and temperature of the coolant as input variables. Otherwise, tolerance calculations of the thermal model must be used to account for the corresponding inaccuracies or deviations due to delayed and / or inaccurate measurement data acquisition. This usually disadvantageously leads to a reduction in the overall performance of the power electronics in question (e.g., inverter).

[0010] It is therefore an object of the present invention to show a novel way by which a simple and reliable detection of both a flow rate and a temperature of the coolant in the coolant channel can be realized in a cooling of the type explained above.

[0011] According to a first aspect of the invention, this object is achieved in a cooling device for cooling power electronics, comprising a heat sink which can be brought into thermal contact with power electronics and in which a coolant channel through which a coolant can flow is formed, in that the cooling device further comprises a detection device for detecting a flow rate of the coolant and a temperature of the coolant, which is designed to: - to generate first ultrasonic pulses and to measure a first transit time of these first ultrasonic pulses running in the coolant channel along a specific first path, wherein this first path runs upstream with respect to the flow direction of the coolant, - to generate second ultrasonic pulses and to measure a second transit time of these second ultrasonic pulses running in the coolant channel along a specific second path, wherein this second path runs downstream with respect to the flow direction of the coolant, - to determine the flow rate of the coolant based on an evaluation of the first run time and the second run time, and - to determine the temperature of the coolant based on an evaluation of the first runtime and / or the second runtime and / or based on a measurement and evaluation of a waveform of the first ultrasonic pulses at the end of the first path and / or second ultrasonic pulses at the end of the second path.

[0012] With the detection device provided according to the invention, a simple and reliable detection of both a flow rate and a temperature of the coolant in the coolant channel can advantageously be realized.

[0013] When determining the temperature based on a measurement and evaluation of the waveform at the end of the path in question, a measurement of the waveform at the beginning of the path in question can optionally also be provided in order to also take this into account in the evaluation (and thus to evaluate a change in the waveform during the propagation of the ultrasound pulse in question from the beginning to the end of the path).

[0014] The course of the first path, relative to the flow direction of the coolant, "upstream" means that a point at which this path ends, i.e., where the first ultrasonic pulses are received, is located upstream of the point at which this path begins, i.e., where the ultrasonic pulses are generated. For the course of the second path, relative to the flow direction of the coolant, "downstream," the situation is exactly the opposite: this path ends at a point at which the second ultrasonic pulses are received, which is located downstream of the point at which this path begins, i.e., where the second ultrasonic pulses are generated.

[0015] An "ultrasonic pulse" within the meaning of the invention can (when generated) represent a single oscillation process or "individual pulse" (e.g., a rectangular pulse), but preferably comprises a sequence of several (e.g., 3-5) identical individual pulses or oscillation periods, whereby the term "ultrasonic pulse" then refers to the entirety of these individual pulses or oscillation periods. A fundamental frequency of the ultrasonic pulse can, for example, be in a range from 100 kHz to 5 MHz.

[0016] The different orientations of the first and second paths mean that the propagation speeds and thus the aforementioned travel times of the ultrasonic pulses depend on the flow velocity of the coolant in the coolant channel. As a result, the flow of the coolant increases the travel times of the upstream first ultrasonic pulses, whereas the travel times of the downstream second ultrasonic pulses are reduced. This effect is greater the higher the flow rate and thus the flow velocity of the coolant.

[0017] Therefore, the flow rate of the coolant can be determined by appropriate evaluation of the first run time and the second run time.

[0018] In one embodiment of the invention, this evaluation also determines the speed of the ultrasonic pulses at which they would propagate in the coolant at a coolant flow velocity of zero. This information can be advantageously used, for example, in determining the coolant temperature.

[0019] Preferably, the coolant channel has a uniform cross-section at least in an area containing the first and second paths.

[0020] Regarding the determination of the coolant temperature, a temperature dependence of the ultrasonic velocity can be determined, for example, for the specific coolant used, i.e., a temperature-dependent group velocity and / or (in the presence of dispersion) a temperature-dependent phase velocity, and thus taken into account in the operation of the detection device. In particular, a determination of the temperature can therefore be provided based on an evaluation of the first transit time and / or the second transit time, taking into account a previously determined temperature dependence of an ultrasonic velocity for the coolant.

[0021] A change in the temperature of the coolant, with a corresponding change in the group velocity, causes a change in the running time of ultrasonic pulses in the coolant, so that the temperature of the coolant can be determined by taking into account the previously determined temperature dependence based on an evaluation of the first running time and / or the second running time.

[0022] The (additional) dependence of each such transit time on the flow velocity as a "disturbance factor" can be advantageously eliminated by considering both the first transit time and the second transit time in the evaluation. For example, or equivalently, to determine the temperature, for example, in a first step, as already mentioned above, the velocity of the ultrasonic pulses can be determined by evaluating the first and second transit times, which would propagate in the coolant at a flow velocity of zero. This velocity can then be used in a further step (e.g., as the input variable for a lookup table) to determine a coolant temperature associated with this velocity.

[0023] If a temperature dependence of the dispersion (frequency dependence of the phase velocity) exists for the specific coolant used, this temperature dependence of the dispersion or phase velocities can also be used within the scope of the invention to determine the temperature of the coolant, alternatively or in addition to the use of a previously determined temperature dependence of the group velocity already explained above.

[0024] The presence of temperature-dependent dispersion during the propagation of the ultrasonic pulses in the coolant leads to a continuous change in the waveform of the ultrasonic pulses during this propagation. Therefore, the temperature of the coolant can also be determined by measuring and evaluating this change in the waveform. For this purpose, an ultrasonic transducer representing the end of the relevant path can first convert the impinging ultrasonic pulse into an electrical measurement signal corresponding to the waveform of this pulse. From this measurement signal, one or more waveform parameters can then be determined which are characteristic of the change in the waveform (e.g., in comparison to the original waveform of the pulse immediately after its generation at the beginning of the relevant path). Such a parameter can be, for example, a "pulse width" (i.e.,The pulse width (duration) of the ultrasonic pulse received at the end of the path is determined in order to determine the coolant temperature based on this pulse width (or a change in the pulse width indicated by this pulse width). The determined pulse width can, for example, be used as the input variable for a lookup table to determine the coolant temperature associated with this pulse width.

[0025] To determine the coolant temperature based on a measurement and evaluation of the waveform (or its change during propagation along the relevant path), another method is to subject the waveform of the relevant measurement signal to a Fourier analysis as part of the evaluation, and to determine the temperature based on the resulting spectral composition of this waveform. In this embodiment, for example, one or more parameters describing this spectral composition can be used as input(s) to a lookup table in order to determine the coolant temperature associated with this or these parameters.

[0026] In one embodiment, a measurement of the waveform in question is also provided at the beginning of the path in question in order to take this into account when evaluating the waveform measured at the end of the path.

[0027] In one embodiment, the cooling device comprises a plurality of ultrasonic transducers, each of which is designed to convert a supplied electrical control signal into a corresponding ultrasonic signal and / or to convert an incident ultrasonic signal into a corresponding electrical measurement signal in order to thereby realize the first and second paths.

[0028] In this case, the detection device can comprise a control unit which is designed to control at least one of the ultrasonic transducers to generate the first ultrasonic pulses by supplying first control signals, to control at least one of the ultrasonic transducers to generate the second ultrasonic pulses by supplying second control signals, and to receive and evaluate the measurement signals respectively generated by at least one of the ultrasonic transducers in order to determine the flow rate and the temperature of the coolant.

[0029] In a more specific embodiment, the detection device comprises: - a first ultrasonic transducer arranged in the region of the coolant channel and a second ultrasonic transducer arranged in the region of the coolant channel upstream of the first ultrasonic transducer with respect to the flow direction of the coolant, wherein the two ultrasonic transducers are each designed to convert a supplied electrical control signal into a corresponding ultrasonic signal and to convert an incident ultrasonic signal into a corresponding electrical measurement signal, - a control unit configured to control the first ultrasonic transducer to generate the first ultrasonic pulses by supplying first control signals, to control the second ultrasonic transducer to generate the second ultrasonic pulses by supplying second control signals, and to receive and evaluate the measurement signals respectively generated by the ultrasonic transducers in order to determine the flow rate of the coolant and the temperature of the coolant.

[0030] The control unit of the detection device can, for example, be designed to determine the temperature of the coolant taking into account a temperature dependence of an ultrasonic speed in the coolant stored in the control unit.

[0031] In this embodiment, the two ultrasonic transducers can advantageously be used both to generate and receive the ultrasonic pulses required for detection. In this embodiment, the first and second paths can be identical to each other, except for their direction (first path upstream, second path downstream), and thus be provided with the same length.

[0032] However, neither of these is by any means mandatory within the scope of the invention, and this embodiment could, for example, be modified such that a first pair of ultrasonic transducers is provided for generating and receiving the first ultrasonic pulses, of which a first transducer generates these pulses and a second transducer receives these pulses, and a second pair of ultrasonic transducers is provided for generating and receiving the second ultrasonic pulses, of which a first transducer generates these pulses and a second transducer receives these pulses. In this modified embodiment, the first and second paths could differ from one another not only in their direction of travel (first path upstream, second path downstream), but also in their course and thus, for example, also in their length.

[0033] Furthermore, within the scope of the invention, an arrangement of three ultrasonic transducers can also be provided, for example, of which one transducer is provided for generating ultrasonic pulses, and the other two transducers, one arranged upstream and the other downstream of the first-mentioned transducer, are provided for receiving these ultrasonic pulses. In this case, the ultrasonic pulses generated by the first-mentioned ultrasonic transducer can represent both the first and the second ultrasonic pulses within the meaning of the invention.

[0034] In these modifications, the control device used to control the generation of the required ultrasonic pulses and to receive and evaluate the required measurement signals must be modified accordingly.

[0035] With regard to the specific design of the ultrasonic transducers, the relevant prior art can advantageously be used. In one embodiment, for example, the ultrasonic transducers used are each designed as a piezoelectric transducer in order to convert an applied electrical control voltage into a corresponding ultrasonic signal and / or to convert an incident ultrasonic signal into an electrical measurement voltage using the piezoelectric effect.

[0036] In one embodiment, the cooling device is further configured to calibrate the temperature determination in a calibration mode using a data signal supplied to the cooling device (or its control unit), which contains information representative of the temperature of the coolant.

[0037] According to a further aspect of the invention, a power electronics system is provided that is equipped with a cooling device of the type described here for cooling the power electronics. The power electronics can, for example, be housed together with the heat sink and / or other components of the cooling device in an "electronics module."

[0038] The term “power electronics” is to be interpreted broadly and, in the context of the invention, is intended to mean that a comparatively high electrical power is involved for electronic devices, which is, for example, generated, controlled, stored or consumed by the power electronics (circuit arrangement) during operation. This is generally the case, for example, when the circuit arrangement in question is not intended for the generation, control, storage and / or use of electrical energy for pure data processing, but rather this energy is used to supply “electrical consumers” (such as an electric machine for driving a vehicle). This primarily applies to devices whose power consumption during operation can exceed 100 W, in particular more than 1 kW.

[0039] For example, the power electronics may comprise power electronic components and a circuit board, with a flat side of the circuit board being in contact with a cooling surface of the heat sink of the cooling device. For example, a flat side of the circuit board not covered with electronic components or conductor tracks may have a metallization layer (e.g., made of copper or a copper alloy) that is bonded to the cooling surface of the heat sink (e.g., made of aluminum or an aluminum alloy) for heat dissipation, e.g., via a solder layer. Alternatively, the flat side of the circuit board in question may be bonded to the cooling surface of the heat sink, e.g., via an adhesive.

[0040] With regard to thermal requirements, the circuit board can advantageously have, for example, an electrically insulating substrate made of a ceramic material such as, for example, based on aluminum nitride (AIN) or, for example, based on aluminum oxide (Al2O3).

[0041] The power electronics can include, in particular, power semiconductor components such as diodes, transistors (e.g., MOSFETs), thyristors, etc. In particular, semiconductor components manufactured using SiC (silicon carbide) technology can be provided.

[0042] In one embodiment of the power electronics, this is designed as an inverter for converting direct current into alternating current. In particular, this can be an inverter for supplying power to an electrical machine (e.g., for driving a vehicle).

[0043] In one embodiment of the invention, a thermal model is used to control or regulate the power electronics, by means of which the electrical power of the power electronics is limited as needed (e.g., due to the risk of excessive heating of the power electronics). This model can advantageously be inputted as input variables, including values ​​of the flow rate and the temperature of the coolant determined according to the invention. The model can be implemented by software running in a control device of the power electronics.

[0044] According to a further aspect of the invention, a method is provided for detecting a flow rate and a temperature of a coolant flowing in a cooling device for cooling power electronics through a coolant channel formed in a heat sink of the cooling device that is in thermal contact with the power electronics, comprising the steps: - generating first ultrasonic pulses and measuring a first transit time of these first ultrasonic pulses running in the coolant channel along a specific first path, wherein this first path runs upstream with respect to the flow direction of the coolant, - generating second ultrasonic pulses and measuring a second transit time of these second ultrasonic pulses running in the coolant channel along a specific second path, wherein this second path runs downstream with respect to the flow direction of the coolant, - Determining the flow rate of the coolant based on an evaluation of the first running time and the second running time (in particular, for example, evaluating a difference between the first and second running times), and - Determining the temperature of the coolant, e.g. taking into account a temperature dependence of an ultrasonic speed determined in advance for the coolant, based on the first transit time and / or based on the second transit time and / or based on a measurement and evaluation of a waveform of the first ultrasonic pulses and / or second ultrasonic pulses at the end of the relevant path (or also measuring and evaluating a change in the waveform during ultrasonic propagation).

[0045] The embodiments and special configurations described here for the device according to the invention can, individually or in any combination, also be provided in an analogous manner as embodiments or special configurations of the method according to the invention, and vice versa.

[0046] In one embodiment of the method, it is provided that, in order to determine the temperature of the coolant, both the waveform of the first ultrasonic pulses at the end of the first path and the waveform of the second ultrasonic pulses at the end of the second path are measured and evaluated.

[0047] In one embodiment, the method further comprises a step of calibrating the temperature determination with the aid of a provided data signal which contains information representative of the temperature of the coolant.

[0048] In one embodiment of the method, - that the first ultrasonic pulses are generated by means of a first ultrasonic transducer arranged in the region of the coolant channel and, after passing through the first path, are received by a second ultrasonic transducer arranged in the region of the coolant channel upstream of the first ultrasonic transducer with respect to the flow direction of the coolant, - that the second ultrasonic pulses are generated by the second ultrasonic transducer and received by the first ultrasonic transducer after passing through the second path, wherein the two ultrasonic transducers are each designed to convert a supplied electrical control signal into a corresponding ultrasonic signal and to convert an incident ultrasonic signal into a corresponding electrical measurement signal, - that the first ultrasonic transducer is controlled to generate the first ultrasonic pulses by supplying first control signals, the second ultrasonic transducer is controlled to generate the second ultrasonic pulses by supplying second control signals, and - that the measurement signals generated by the ultrasonic transducers are received and evaluated to determine the flow rate and temperature of the coolant.

[0049] Analogous to an embodiment already explained above for the cooling device, the above embodiment of the cooling method could, for example, be modified (arrangement of two pairs of ultrasonic transducers) such that the second ultrasonic pulses are not generated and received by means of the first and second ultrasonic transducers, but are generated by a third ultrasonic transducer and, after passing through the second path, are received by a fourth ultrasonic transducer, wherein in this case, not the second ultrasonic transducer but the third ultrasonic transducer is controlled to generate the second ultrasonic pulses by supplying second control signals, and the measurement signals generated by the second and fourth ultrasonic transducers are received and evaluated to determine the flow rate and temperature of the coolant.According to another modification of the cooling method (arrangement of three ultrasonic transducers), it could also be provided that both the first ultrasonic pulses and the second ultrasonic pulses are generated by one and the same ultrasonic transducer arranged in the region of the coolant channel, and are received by a further pair of ultrasonic transducers (one transducer being arranged upstream of the pulse-generating transducer and the other transducer being arranged downstream of the pulse-generating transducer) as the first ultrasonic pulses and as the second ultrasonic pulses.

[0050] According to a further aspect of the invention, the use of a cooling device of the type described here and / or a cooling method of the type described here is proposed in order to cool an inverter for supplying power to the electric machine in a vehicle which is equipped with an electric machine for driving the vehicle (e.g. three-phase synchronous motor). The vehicle can in particular be, for example, a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV). In particular, such vehicles typically have both an inverter and an electrical energy storage device. In this respect, according to a further aspect of the invention, the use of the cooling device and / or the cooling method is also proposed in order to cool an inverter for supplying power to the electric machine in a vehicle which is equipped with an electrical energy storage device (e.g.“vehicle battery”) is equipped to supply electricity to a drive system of the vehicle, to cool this energy storage device.

[0051] An interesting application for the above-mentioned possibility of calibrating the temperature determination (with the aid of a provided data signal which contains information representative of the temperature of the coolant) arises, for example, in applications of the invention in which the nature, in particular, for example, the composition, of the coolant can vary over time. An example of this is the composition of a coolant consisting of water and an antifreeze, such as a water-glycol mixture or the like, which varies in practice. If the nature or composition (e.g., water / glycol mixture ratio) of the coolant influences the values ​​of the variables used for temperature determination (i.e., first and / or second transit time, and / or waveform(s) of the first and / or second ultrasonic pulses at the respective path end), an inaccuracy in the temperature determination results, which can be caused, for example, bycalibration carried out from time to time can be advantageously eliminated.

[0052] When using the cooling device or the cooling method in a vehicle (e.g. for cooling an inverter or an electrical energy storage device), the calibration can be carried out advantageously in a state of the vehicle in which the temperature of the coolant is known, e.g. due to cooling to the ambient temperature, e.g. after the vehicle has been parked and a certain time has passed.

[0053] In this state, one or more measured values ​​obtained from sensors elsewhere in the vehicle can be used to determine the ambient temperature and thus the coolant temperature. In one embodiment of the calibration, the information representative of the coolant temperature is obtained, for example, using (at least) one temperature sensor that measures a temperature in the area of ​​the power electronics. Such sensors are often located on semiconductor switches and / or on a circuit board (e.g., a "DCB sensor") of the power electronics.

[0054] With information about the temperature determined in this way, the data signal can then be generated and, for example, a control unit of the detection device used for temperature determination (e.g. program-controlled) can calibrate the temperature determination.

[0055] Calibration can be carried out, for example, by a suitable adjustment (calibration) of parameters in a control program running in the control unit to determine the temperature, including, for example, an adjustment or selection of lookup tables of the type already explained.

[0056] Calibration can therefore be used to bring a temperature value from the temperature determination into agreement with the temperature value known from the provided data signal.

[0057] In the example of use in a vehicle, for example, a calibration can be provided before each start of a driving cycle in order to reduce the aforementioned inaccuracy in the coolant temperature determination due to varying coolant properties or composition.

[0058] In one embodiment, the control unit of the detection device is configured to receive the data signal via a data interface in order to perform the calibration step based on the temperature information transmitted thereby. The data interface can be provided, for example, for connecting the control unit to a digital communication bus system of the vehicle and / or, for example, for communication with a control device controlling the power electronics (which obtains the temperature information required for calibration, for example, with the aid of a temperature sensor arranged in the area of ​​the power electronics).

[0059] The invention will be further described below using exemplary embodiments with reference to the accompanying drawings. They schematically depict: Fig. 1 a power electronics system with a cooling device for cooling the power electronics according to a first embodiment, in a first phase of detecting a flow rate and a temperature of a coolant flowing in the cooling device, Fig. 2 Time courses of a control signal and a measurement signal for the Fig. 1 first phase shown, Fig. 3 the power electronics of Fig. 1 in a second phase of detecting the flow rate and temperature of the coolant, Fig. 4 Time courses of a control signal and a measurement signal for the Fig. 3 shown second phase, Fig. 5 an exemplary curve of an ultrasonic speed in a coolant as a function of the temperature of the coolant, Fig. 6 Time courses of a control signal and a measurement signal for a specific temperature of the coolant, and Fig. 7 Time courses of a control signal and a measurement signal for a different coolant temperature.

[0060] Fig. 1 shows an embodiment of a power electronics 1 which is equipped with a cooling device 10 in order to cool the power electronics 1 during its operation.

[0061] The power electronics 1 shown is, for example, an inverter (or an inverter module) for converting direct current into alternating current (e.g., on board a vehicle). Alternatively, it could be, for example, a power electronics component of an electrical energy storage device (e.g., on board a vehicle).

[0062] In the example, power electronics 1 includes power electronic components, e.g. power semiconductor components such as MOSFETs, some of which are Fig. 1 and are each marked with the reference number 2. The components 2 are arranged on a circuit board 3 and are connected via metallic conductor tracks to a (in Fig. 1 lower) flat side of the circuit board 3. With regard to the thermal requirements of the power electronics 1, the circuit board 3 can, for example, comprise an electrically insulating substrate based on a ceramic material, on which the metallic conductor tracks are formed on the flat side.

[0063] In the example, the cooling device 10 comprises a heat sink 12 which is in thermal contact with the power electronics 1 and in which a coolant channel 14 is formed through which a coolant flows. The coolant, in the example water, is circulated in a cooling circuit (not shown), which, among other things, Fig. 1. This coolant channel 14 has a uniform cross-section in the area shown. In the example, this cross-section has a rectangular (e.g., approximately square) contour. The coolant channel 14 can, for example, traverse the heat sink 12 once or, for example, run in a meandering manner with several turns through the heat sink 12.

[0064] In order to cool the power electronics 1 by means of the cooling device 10 or the coolant used therein, a (in Fig. 1 upper) flat side of the circuit board 3 in thermal contact with a cooling surface of the heat sink 12 of the cooling device 10. For this purpose, the circuit board 3 can be connected to the cooling surface of the heat sink 12, for example, via a solder layer (not shown).

[0065] The cooling device 10 further comprises a detection device 20 for detecting a flow rate F of the coolant and a temperature T of the coolant flowing in the cooling device 10. The flow direction of the coolant is in Fig. 1 (from left to right) indicated by an arrow.

[0066] For this purpose, in the example shown, the detection device 20 comprises two ultrasonic transducers 22-1, 22-2 arranged in the region of the coolant channel 14, which are each designed to convert a supplied electrical control signal into a corresponding ultrasonic signal and to convert an incident ultrasonic signal into a corresponding electrical measurement signal, wherein the second ultrasonic transducer 22-2 is arranged upstream of the first ultrasonic transducer 22-1 with respect to the flow direction of the coolant.

[0067] The detection device 20 further comprises an electronic control unit 24 (e.g. microcontroller) which is program-controlled in the example and is designed to, according to a control program (software) running therein, - to control the two ultrasonic transducers 22-1, 22-2 to generate ultrasonic pulses by supplying corresponding control signals, and - to receive and evaluate the measurement signals generated by the ultrasonic transducers 22-1, 22-2 in order to determine the flow rate F and the temperature T of the coolant with the aid of these measurement signals.

[0068] In the Fig. 1 and Fig. 2 shows a first step of the detection carried out by the detection device 20 according to the control program, in which step the control unit 24 controls the first ultrasonic transducer 22-1 to generate one or more ultrasonic pulses, hereinafter referred to as “first ultrasonic pulses”, for which purpose the control unit 24 generates a control signal c1 ( Fig. 2) and fed to the first ultrasonic transducer 22-1.

[0069] In this first step, the control unit 24 receives the measurement signals m2 ( Fig. 2).

[0070] Fig. For this first step, Figure 2 shows, by way of example, a time profile of a control signal c1 for generating a first ultrasonic pulse. In this example, the control signal c1 has a profile with several consecutive rectangular "individual pulses" as shown in Fig. 2. This time period, i.e., the duration of the control signal c1, corresponds to a "pulse width of the ultrasonic pulse" at the beginning of path P1. The temporal progression of the signal c1 defines a "waveform" of this ultrasonic pulse at the beginning of path P1.

[0071] In the case of the use of piezoelectric ultrasonic transducers 22-1, 22-2, the control signal c1 represents, for example, a control voltage supplied to the ultrasonic transducer 22-1.

[0072] Fig. 2 further shows, by way of example, a temporal profile of a measurement signal m2 resulting from the impingement of the aforementioned first ultrasonic pulse on the second ultrasonic transducer 22-2 after this ultrasonic pulse has passed through the path P1 running from the ultrasonic transducer 22-1 upstream to the ultrasonic transducer 22-2. In this example, the measurement signal m2 has an approximately sinusoidal profile with an initially increasing and then decreasing amplitude. This profile results from the profile of the control signal c1 taking into account the "transmission path", i.e. the conversion of c1 into ultrasound in the ultrasonic transducer 22-1, the propagation as ultrasound in the respective medium (here: water), and the conversion of the ultrasound back into the electrical measurement signal (e.g. measurement voltage) m2.

[0073] In the example shown, the path P1 runs from the one that is suitably positioned at a point on a (in Fig. 1 upper) wall of the coolant channel 14, initially at an angle α oblique to the flow direction of the coolant (cf. arrow at reference symbol F) through the coolant channel 14 to a point on the opposite (in Fig. 1 lower) wall of the coolant channel 14. In accordance with a reflection of the ultrasonic pulse taking place there, the path P1 runs from there at the same angle α obliquely to the flow direction through the coolant channel 14 back to a point on the first-mentioned wall at which the second ultrasonic transducer 22-2 is arranged.

[0074] In Fig. 2, a start time "ts" of the control signal c1 and, consequently, the start time of the ultrasonic pulse emitted by the ultrasonic transducer 22-1, as well as a reception time "tr" of this ultrasonic pulse at the ultrasonic transducer 22-2, determined by the control unit 24 from the measurement signal m2, are identified. The reception time corresponds to a start time of the measurement signal m2 at which, for example, the amplitude of the curve ("envelope") of m2 exceeds a predetermined threshold. The control unit 24 can determine a first transit time t1 of the first ultrasonic pulses as the difference between the start time tr and the reception time ts (so-called TOS method): First transit time t1 = tr - ts (for first ultrasonic pulse)

[0075] In one embodiment, several (e.g. 2 or 3) first transit times t1 are measured in this way one after the other and an average value of t1 formed therefrom is used for the subsequent processing (evaluation).

[0076] Fig. 3 shows again the power electronics 1 equipped with the cooling device 10 of Fig. 1, but showing a second step of the detection performed by the detection device 20.

[0077] In this second step, the roles of the two ultrasonic transducers 22-1, 22-2 are swapped, ie the control unit 24 now controls the second ultrasonic transducer 22-2 to generate one or more ultrasonic pulses, referred to below as “second ultrasonic pulses”, for which second control signals c2 ( Fig. 4) and fed to the second ultrasonic transducer 22-2. The first ultrasonic transducer 22-1 generates measurement signals m1 ( Fig. 4) received.

[0078] Fig. 4 shows for this second step a time course of the control signal c2 supplied to generate a second ultrasonic pulse, which in the example has the same course as the one in Fig. 2 has the control signal c1 shown.

[0079] Fig. 4 further shows a temporal profile of the measurement signal m1 resulting from the impingement of the second ultrasonic pulse on the first ultrasonic transducer 22-1, after this ultrasonic pulse has passed through the path P2 running downstream from the ultrasonic transducer 22-2 to the ultrasonic transducer 22-1. The measurement signal m1 again has an approximately sinusoidal profile (waveform) with an initially increasing and then decreasing amplitude (envelope), which results from the profile (waveform) of the control signal c2, taking into account the "transmission path" with an ultrasonic propagation via the path P2.

[0080] In the Fig. 1 and Fig. In the embodiment shown in Figure 2, the first and second paths P1, P2 are identical to each other and of the same length, apart from the opposite directions of travel (first path P1 upstream, second path P2 downstream).

[0081] In Fig. 4, a start time "ts" of the control signal c2 and, consequently, the start time of the ultrasonic pulse emitted by the ultrasonic transducer 22-2, as well as a reception time "tr" of this ultrasonic pulse at the ultrasonic transducer 22-1, determined by the control unit 24 from the measurement signal m1 (corresponding to a start time of the measurement signal m1, which is determined in the same way as for the measurement signal m2), are identified. From this, the control unit 24 can determine a second transit time t2 of the second ultrasonic pulses as the difference between the start time tr and the reception time ts: Second transit time t2 = tr - ts (for second ultrasonic pulse)

[0082] Due to the opposite directions (orientations) of the two propagation paths P1, P2, upstream (P1) and downstream (P2), the first and second propagation times t1, t2 differ from each other. Compared to the propagation time that would result at a coolant flow rate F of zero (F = 0), the first propagation time t1 is increased and the second propagation time t2 is decreased under the influence of the flow (F > 0).

[0083] In a third step of the recording, the flow rate F of the coolant is determined based on an evaluation of the running times t1 and t2. In the present example ( Fig. 1 and Fig. 2) the control unit 24 can determine (calculate) a flow velocity “vm” of the coolant, for example, as follows: vm=L2 cos α×t1−t2t1×t2 Here, the following are used: vm flow velocity of the coolant L Length of paths P1, P2 α Angle between the paths P1, P2 and the flow direction t1 first term t2 second term

[0084] If the “flow rate F” is not to be defined or calculated in a more general sense as this flow velocity vm, but e.g. as a volume flow rate or mass flow rate, the flow velocity vm can be converted using a proportionality constant k that takes into account the properties of the coolant and the geometry (e.g. cross-sectional area) of the coolant channel 14 as follows: F=k×vm Here, the following are used: F flow rate k proportionality constant vm flow velocity

[0085] In the present example, the control unit 24 can optionally further determine, based on such an evaluation of the transit times t1 and t2, a speed “vus” or transit time “t0” of the ultrasonic pulses with which they would propagate in the coolant at a (fictitious) flow rate of the coolant of zero (F = 0), e.g. as follows: vus=L2 cos α×t1+t2t1×t2 or t0=2 cos α×t1×t2t1+t2

[0086] It is understood that the formulas given above for calculating the flow rate F and the velocity vus (or transit time t0) for the present example ( Fig. 1 and Fig. 2) deviating geometric conditions (with different courses of the first and second paths P1, P2) may need to be modified accordingly.

[0087] In addition, the third step of the acquisition process involves determining the temperature T of the coolant. This determination can be performed, for example, by taking into account a previously determined temperature dependence of an ultrasonic velocity (group velocity and / or frequency-dependent phase velocities) for the coolant.

[0088] Fig. Figure 5 shows an exemplary curve for an ultrasonic velocity “vus” (group velocity) of a specific coolant as a function of the temperature T. In the range shown, a temperature increase up to approximately T=70 °C is associated with a steady increase in the speed of sound “vus”.

[0089] Therefore, taking such a temperature dependency into account, the temperature of the coolant can also be advantageously determined based on each transit time of an ultrasonic pulse determined within the scope of the invention. For this purpose, for example, a Fig. 5 shown curve (characteristic curve) can be kept in the control unit 24 (e.g. in the form of a look-up table) in order to draw a conclusion about the temperature of the coolant and to determine this based on an evaluation of the first running time (t1) and / or second running time (t2).

[0090] The Fig. 6 and Fig. 7 illustrate the influence of such a temperature-dependent speed “vus” - as in Fig. 5 - on the transit time of an ultrasonic pulse.

[0091] Fig. Figure 6 shows, as an example, for a "first ultrasonic pulse", ie with control signal c1 and measurement signal m2, the time courses of these signals c1(t) and m2(t) for a specific temperature of the coolant. This results in the Fig. 6 marked transit time t1-1 of the ultrasonic pulse along the respective path P1.

[0092] Fig. 7 shows the same signal curves as Fig. 6, but for a different coolant temperature. This results in the Fig. 7 marked runtime t1-2, which in this example is shorter than runtime t1-1.

[0093] Thus, the temperature T can be determined by a suitable evaluation of the respective running time (here, for example, t1). The dependence of the running time on the current flow velocity of the coolant can be eliminated, for example, by first correcting the respective measured running time based on the result of a determination of the flow velocity (or flow rate) before evaluating such a corrected value to determine the temperature.

[0094] If the dependence of temperature on the running time or speed of the ultrasonic pulses is not clear over a larger temperature range, as in the example of Fig. 5 over a range including the maximum speed "vus" at approximately T=70 °C, it is contemplated within the scope of the invention to nevertheless arrive at an unambiguous determination of the temperature with the aid of a thermal model. For this purpose, the thermal model can be provided with, for example, at least one operating parameter of the power electronics (e.g., an electrical power and / or electrical current detected in the power electronics) and / or at least one operating parameter of a cooling circuit system containing the coolant channel (e.g., operating parameters from a control electronics of a pump device for pumping the coolant) as input variables. For the example of Fig. 5, such a model can then decide, based on the aforementioned operating parameters and / or their temporal course, whether the temperature T is above or below the temperature (here about 70 °C) at which the extremum (here: maximum) of the temperature-dependent velocity “vus(T)” is located.

[0095] The dependence of each running time on the current flow velocity of the coolant can also be eliminated, for example, by using both the first running time t1 and the second running time t2 for the evaluation or, for example, by first determining, as already explained above, from the first and second running times t1, t2, the “fictitious” speed of the ultrasonic pulses with which they would propagate in the coolant channel 14 without flow (F=0), in order to use this speed for determining the temperature T (e.g. as an input variable for a lookup table).

[0096] Such a determination of the temperature T of the coolant provided for in the third step of the detection taking into account a temperature dependence of an ultrasonic velocity (group velocity and / or frequency-dependent phase velocities) can alternatively or additionally also be carried out by measuring and evaluating a change in the waveform during the propagation of the first ultrasonic pulses and / or second ultrasonic pulses.

[0097] Such an additional determination of the temperature, or a determination of the temperature using more than one method, can be advantageously used in the invention, for example, for plausibility checks and / or for reasons of redundancy or increasing the accuracy of the temperature determination. Thus, in the invention, the results of more than one method used to determine the temperature T can be considered (e.g., by calculating a (possibly weighted) average of these results).

[0098] The “waveform” of the example of Fig. 1 to 4 ultrasonic pulses starting at the beginning of the respective path P1 or P2 corresponds to the Fig. 2 (for P1) or Fig. 4 (for P2) shown curves of the control signal c2(t) or c1(t), whereas the waveform of these ultrasonic pulses at the end of their respective path P1 or P2 corresponds to the Fig. 2 or Fig.4 corresponds to the curves of the measuring signal m1 or m2.

[0099] The "change in waveform" is thus defined by the difference between these waveforms at the beginning and at the end of the respective path. This change is dependent on the temperature in the presence of temperature-dependent dispersion of ultrasound propagation and can therefore also be used to determine the temperature. For this purpose, at least one waveform parameter can be determined from at least one measurement signal (generated upon reception of the ultrasound pulses), which is characteristic of a corresponding waveform change.

[0100] As such a parameter of the waveform, for example, a pulse width (duration) of the respective waveform can be provided in order to draw a conclusion about the temperature T of the coolant and thus to determine T. For example, the pulse width (or pulse width change) determined from a measurement signal (such as measurement signal m2 for first ultrasonic pulses and / or measurement signal m1 for second ultrasonic pulses) can be used, e.g. as an input variable of a lookup table, in order to determine a temperature T of the coolant associated with this pulse width.

[0101] The “pulse width” can be defined in particular as the time period within which an envelope of the measurement signal exceeds a predetermined threshold value.

[0102] Alternatively or additionally, within the scope of the invention, other parameters of the waveform can also be determined during the evaluation of the measurement signal and provided for determining the temperature of the coolant, such as at least one other parameter which (like the pulse width) relates to the course of the envelope curve (e.g. shape) of the measurement signal in question and / or at least one parameter which relates to the course of the individual “oscillation periods” in the measurement signal, for example at least one parameter which describes a deviation of the oscillation from a sinusoidal oscillation.

[0103] In this context, another method for determining the temperature is to subject the waveform of the measurement signal to Fourier analysis and to determine the temperature based on the resulting spectral composition of the waveform. This method can, for example, determine one or more parameters that describe this spectral composition, and from this, the corresponding temperature can be determined.

[0104] In the illustrated embodiment, information about the flow rate F (e.g. volume flow rate or mass flow rate) and the temperature T of the cooling device 10 obtained by the control unit 24 in a manner as described above is used within the framework of a control of the power electronics 1 (in the example: inverter) in order to reduce or limit an electrical power of the power electronics 1 when a condition that is assessed as critical based on the determined parameters F and T occurs (e.g. as long as the condition is assessed as critical).

[0105] For all methods for determining the temperature T based on a measurement and evaluation of the waveform, the transit time t1 and / or the transit time t2 can also be taken into account during the evaluation within the scope of the invention. For example, the transit time(s) and / or the parameters derived (calculated) from them can be used as (additional) input variables when using a lookup table.

[0106] The method carried out by the cooling device 10 by means of the detection device 20 for detecting the flow rate F and the temperature T of the coolant comprises, in the example shown, the following steps: a) generating first ultrasonic pulses and measuring their transit time t1 in the coolant channel 14 along the upstream first path P1, b) generating second ultrasonic pulses and measuring their transit time t2 in the coolant channel 14 along the downstream second path P2, and c) determining the flow rate F of the coolant based on a difference between the first running time t1 and the second running time t2, and Determining the temperature T of the coolant taking into account a predetermined temperature dependence of a Ultrasonic speed, e.g. based on a measurement and evaluation of a pulse width and / or other parameters in the course of the measurement signals m2, m1 corresponding to the waveform of the ultrasonic pulses at the end of the respective path P1, P2.

[0107] If the nature or composition of the coolant can vary over time, an associated dependency and thus falsification of the result of the temperature determination can be eliminated within the scope of the invention by calibrating the temperature determination as needed or from time to time.

[0108] In summary, the invention and the described embodiments make it possible to overcome, for example, the following disadvantages of cooling devices and methods known in the automotive sector: Inaccurate determination of the flow rate of the coolant, for example when cooling with water; Insufficiently rapid detection of a break in the coolant flow; Inaccurate determination of the temperature of the coolant in the cooling channel; Long response times of coolant temperature sensors; consequently, possible safety problems such as "thermal hazard". List of reference symbols 1 Power electronics 2 components 3 Circuit board 10 Cooling device 12 heat sinks 14 Coolant channel 20 Recording device 22-1 first ultrasonic transducer c1 control signal m1 measurement signal 22-2 second ultrasonic transducer c2 control signal m2 measurement signal 24 Control unit t time ts start time (of an ultrasonic pulse) tr Reception time (of an ultrasonic pulse) t1 transit time (of a first ultrasonic pulse) t2 transit time (of a second ultrasonic pulse) t0 running time (without coolant flow) T Coolant temperature t1-1 running time (at first temperature) t1-2 running time (at second temperature)

Claims

[1] Cooling device (10) for cooling a power electronics system (1), comprising a heat sink (12) which can be brought into thermal contact with a power electronics system (1), in which a coolant channel (14) through which a coolant can flow is formed, characterized by that the cooling device (10) further comprises a detection device (20) for detecting a flow rate (F) of the coolant and a temperature (T) of the coolant, which is designed to - to generate first ultrasonic pulses and to measure a first transit time (t1) of these first ultrasonic pulses running in the coolant channel (14) along a specific first path (P1), wherein this first path (P1) runs upstream with respect to the flow direction of the coolant, - to generate second ultrasonic pulses and to measure a second transit time (t2) of these second ultrasonic pulses running in the coolant channel (14) along a specific second path (P2), wherein this second path (P2) runs downstream with respect to the flow direction of the coolant, - to determine the flow rate (F) of the coolant based on an evaluation of the first running time (t1) and the second running time (t2), and - to determine the temperature (T) of the coolant based on an evaluation of the first running time (t1) and / or the second running time (t2) and / or based on a measurement and evaluation of a waveform of the first ultrasonic pulses at the end of the first path (P1) and / or a waveform of the second ultrasonic pulses at the end of the second path (P2). [2] Cooling device (10) according to claim 1, wherein the detection device (20) comprises: - a first ultrasonic transducer (22-1) arranged in the region of the coolant channel (14) and a second ultrasonic transducer (22-2) arranged in the region of the coolant channel (14) upstream of the first ultrasonic transducer (22-1) with respect to the flow direction of the coolant, wherein the two ultrasonic transducers (22-1, 22-2) are each designed to convert a supplied electrical control signal (c1, c2) into a corresponding ultrasonic signal and to convert an incident ultrasonic signal into a corresponding electrical measurement signal (m1, m2), - a control unit (24) which is designed to control the first ultrasonic transducer (22-1) to generate the first ultrasonic pulses by supplying first control signals (c1), to control the second ultrasonic transducer (22-2) to generate the second ultrasonic pulses by supplying second control signals (c2), and to receive and evaluate the measurement signals (m1, m2) respectively generated by the ultrasonic transducers (22-1, 22-2) in order to determine the flow rate (F) of the coolant and the temperature (T) of the coolant. [3] Cooling device (10) according to one of the preceding claims, further designed to calibrate the temperature determination in a calibration mode with the aid of a data signal supplied to the cooling device (10) which contains information representative of the temperature (T) of the coolant. [4] Power electronics (1), equipped with a cooling device (10) according to one of the preceding claims for cooling the power electronics (1). [5] Power electronics (1) according to claim 4, comprising power electronic components (2) and a circuit board (3), wherein a flat side of the circuit board (3) is in contact with a cooling surface of the heat sink (12) of the cooling device (10). [6] Power electronics (1) according to claim 4 or 5, designed as an inverter for converting direct current into alternating current. [7] Method for detecting a flow rate (F) and a temperature (T) of a coolant flowing in a cooling device (10) for cooling power electronics (1) through a coolant channel (14) formed in a heat sink (12) of the cooling device that is in thermal contact with the power electronics (1), comprising the steps: - generating first ultrasonic pulses and measuring a first transit time (t1) of these first ultrasonic pulses traveling in the coolant channel (14) along a specific first path (P1), wherein this first path (P1) runs upstream with respect to the flow direction of the coolant, - generating second ultrasonic pulses and measuring a second transit time (t2) of these second ultrasonic pulses running in the coolant channel (14) along a specific second path (P2), wherein this second path (P2) runs downstream with respect to the flow direction of the coolant, - Determining the flow rate (F) of the coolant based on an evaluation of the first running time (t1) and the second running time (t2), and - Determining the temperature (T) of the coolant based on an evaluation of the first running time (t1) and / or the second running time (t2) and / or based on a measurement and evaluation of a waveform of the first ultrasonic pulses at the end of the first path (P1) and / or a waveform of the second ultrasonic pulses at the end of the second path (P2). [8] The method according to claim 7, further comprising a step of calibrating the temperature determination with the aid of a provided data signal containing information representative of the temperature (T) of the coolant. [9] Method according to claim 7 or 8, wherein - the first ultrasonic pulses are generated by a first ultrasonic transducer (22-1) arranged in the region of the coolant channel (14) and, after passing through the first path (P1), are received by a second ultrasonic transducer (22-2) arranged in the region of the coolant channel (14) upstream of the first ultrasonic transducer (22-1) with respect to the flow direction of the coolant, and the second ultrasonic pulses are generated by the second ultrasonic transducer (22-2) and, after passing through the second path (P2), are received by the first ultrasonic transducer (22-1), wherein the two ultrasonic transducers (22-1, 22-2) are each designed to convert a supplied electrical control signal (c1, c2) into a corresponding ultrasonic signal and to convert an incident ultrasonic signal into a corresponding electrical measurement signal (m1, m2), - the first ultrasonic transducer (22-1) is controlled to generate the first ultrasonic pulses by supplying first control signals (c1), the second ultrasonic transducer (22-2) is controlled to generate the second ultrasonic pulses by supplying second control signals (c2), and - the measuring signals (m1, m2) generated by the ultrasonic transducers (22-1, 22-2) are received and evaluated in order to determine the flow rate (F) and the temperature (T) of the coolant.

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