Method for determining the temperature of a fluid conveying system

Abstract

Method for determining the temperature of a fluid conveying device (3), in particular the temperature of a fluid conveyed in a fluid circuit (4) of the fluid conveying device (3), which fluid is conveyed in the fluid circuit (4) of the fluid conveying device (3) by means of a pump device (5), wherein the pump device (5) is operated at at least one defined operating point, wherein the temperature is determined based on an operating parameter of the pump device (5).

Description

[0001] The invention relates to a method for determining a temperature of a fluid conveying device, in particular a temperature of a fluid guided in a fluid circuit of the fluid conveying device, which fluid is conveyed by means of a pump device in the fluid circuit of the fluid conveying device.

[0002] Methods for determining temperatures in fluid conveying systems, for example, of components to be tempered or lubricated by the fluid conveying system, or specifically the temperature of the fluid conveyed in the fluid conveying system, are generally known from the prior art. Typically, a temperature sensor is used to determine the temperature. This sensor is in direct or indirect thermal contact with the measuring point whose temperature is to be determined. For example, to determine the temperature of the fluid, a temperature sensor can be arranged at a section of the fluid circuit to record the temperature there.

[0003] Furthermore, it is known from the prior art that more than one temperature sensor is provided for safety reasons, or to provide redundancy or verify a temperature sensor's detection result. However, providing and operating temperature sensors is complex and expensive, especially when using high-resolution temperature sensors. Such sensors must also be operable under the prevailing environmental conditions, particularly under vibration and across wide temperature ranges.

[0004] The invention is based on the object of providing an improved method for determining a temperature of a fluid conveying device.

[0005] As described, the invention relates to a method for determining a temperature of a fluid conveying device, in particular a temperature of a fluid guided in a fluid circuit of the fluid conveying device. The fluid is conveyed by means of a pump device in the fluid circuit of the fluid conveying device. In other words, the pump device is operated to convey the fluid in the fluid circuit, for example to guide the fluid through at least one fluid and / or lubrication channel of the fluid conveying device. The fluid conveying device can be designed in particular to convey a liquid, in particular water or oil, for example as a temperature control device in order to convey the liquid as a temperature control medium for controlling the temperature of at least one component in a temperature control circuit.

[0006] The invention is based on the finding that the pump device is operated in at least one defined operating state, wherein the temperature is determined based on an operating parameter of the pump device. The invention thus proposes that a temperature sensor is not used, or not exclusively used, to determine the temperature of the fluid conveying device, but rather that the temperature can be determined based on an operating parameter of the pump device operated at the defined operating point. This makes it possible to dispense with at least one temperature sensor, for example, a temperature sensor intended to verify the function of a reference sensor. Depending on the application, it is also possible to dispense with an additional temperature sensor entirely.

[0007] The operating parameter of the pump device is related to the temperature of the fluid, so that by recording the operating parameter of the pump device, the temperature of the fluid can be determined. For example, the operating parameter of the pump device can be recorded during operation of the pump device, for example as part of performance monitoring of the pump device. The relationship between the temperature of the fluid or a temperature of the unit in thermal contact with the fluid and the operating parameter of the pump device can, for example, be predetermined, in particular based on reference measurements, a simulation or a model. In principle, there is a relationship between the operating parameter of the pump device and the viscosity of the fluid, which is temperature-dependent. Thus, by monitoring the operating parameter, conclusions can be drawn about the temperature or temperature development of the fluid.Therefore, knowing the fluid, for example a liquid, and its behavior depending on the temperature, the temperature determination is possible based on the recording of the operating parameters of the pump device.

[0008] According to one embodiment of the method, at least one electrical parameter, in particular a power consumption, of the pump device is recorded as an operating parameter. As described, electrical parameters of the pump device, in particular the power consumption, for example, the current consumed by the pump device, are related to the temperature via the viscosity of the fluid. Qualitatively, for example, the power consumption of the pump device increases when pumping the fluid the colder the fluid is, and the power consumption of the pump device decreases the warmer the fluid is.

[0009] Since the operating parameter of the pump device is determined or recorded at a defined operating point, the relationship between the temperature of the fluid and the operating parameter can be established. The defined operating point is measured, for example, in at least one reference measurement, so that a reference parameter of the pump device is available at a reference temperature. If the operating parameter deviates accordingly at the operating point, the temperature of the fluid can be determined. Likewise, a large number of different operating parameters can be pre-measured at different fluid temperatures at different operating points, so that ultimately the temperature can be determined when the defined operating point and the recorded operating parameter are reached, for example by reading a table.

[0010] According to a further embodiment of the method, it can be provided that a speed of the pump device is regulated to a defined pump speed at the defined operating point. In other words, the operating point can be defined by a specific speed of the pump device. If the pump device is operated at the defined operating point, this means that the pump device is operated at a defined pump speed. Depending on the temperature of the fluid and the set pump speed, and depending on the viscosity of the fluid, a specific operating parameter is required in the current operating situation in order to achieve the pump speed. Knowing the defined pump speed and the relationship between the temperature of the fluid, the viscosity and the power consumption, it is thus possible to determine the temperature of the fluid.

[0011] As described, the behavior of the fluid or the pumping device can be predetermined. In this case, a relationship between the temperature and the recorded operating parameter can be predetermined, particularly based on a characteristic map. Advantageously, operating parameters can be determined for a defined operating point for different fluid temperatures, so that the temperature can then be determined accordingly, knowing the operating point and the power consumption or the operating parameter of the pumping device. This procedure can be continued for a multitude of operating points, allowing temperature determination under any operating conditions.

[0012] Alternatively, it is also possible to determine the relationship between temperature and the recorded operating parameter using a model and / or simulation approach. For example, a physical model of the fluid conveying device can be used, which, knowing the operating parameters of the pumping device, can output the fluid temperature, particularly for different operating points.

[0013] The method can be further developed such that the operating parameter is recorded in a regular operating state of the pumping device, or such that a defined measurement state is carried out in which the defined operating point is set. In principle, the temperature can be determined in a regular operating state of the pumping device. This means that the temperature can be determined during regular operation of the pumping device, knowing the pump speed and the operating parameters of the pumping device.

[0014] Likewise, a defined measurement condition can be implemented in which the pump system is specifically brought to the defined operating point, i.e., a predetermined pump speed is set to determine the fluid temperature. In the second case, a measurement point or measurement condition can be selected such that the defined operating point is particularly meaningful for evaluating the relationship between the operating parameter and the temperature. For example, a pump speed can be selected such that the gradient between the operating parameter and the temperature is particularly steep or, alternatively, particularly flat in this range.

[0015] Furthermore, the method can provide for the temperature to be determined exclusively on the basis of the detected operating parameter or for a reference temperature, in particular of a temperature sensor, to be verified using the determined temperature. As already described, the temperature can be determined exclusively on the basis of the detected operating parameter, i.e. no further temperature measurement is required. However, if it is necessary, for example to meet certain safety requirements, to determine the temperature in at least two different ways or to provide a redundant temperature determination, a reference temperature can be verified using the determined temperature, as described above, or an alternative temperature determination can be provided. For this purpose, a temperature sensor that detects a reference temperature can be used.The reference temperature can be verified by comparing it with the specific temperature determined based on the operating parameter of the pumping device as described above.

[0016] As described at the outset, a defined operating point of the pump device is implemented, which can form the basis for determining the temperature. According to a further embodiment of the method, it can be provided that, starting from the at least one operating point, at least a second operating point is controlled, wherein a time measurement is recorded as the operating parameter, which describes the duration for the change in the operating point. In other words, a speed jump of the pump device can be triggered, so that a change from the first defined operating point to the second defined operating point is carried out. The control of the second operating point can in particular be carried out based on a constant, defined power, so that time differences in the change in the operating points can be recorded more effectively.Depending on the fluid's condition, such a change in the operating point will take a different amount of time. The more viscous the fluid, the longer the change from the operating point to the at least one second operating point will take. For example, as described, a transition between the operating points can be pre-measured for different temperatures, so that the fluid temperature can be determined by recording the time measurement.

[0017] In addition to the method, the invention relates to a fluid conveying device, in particular for a motor vehicle, comprising a fluid circuit in which a fluid can be guided or is guided, wherein the fluid conveying device has a pump device which is designed to convey fluid in the fluid circuit of the fluid conveying device, wherein a determination device is designed to determine a temperature based on an operating parameter of the pump device at at least one defined operating point. The fluid conveying device can in particular be assigned to a cooling system and / or a lubricating system of a motor vehicle. Furthermore, the invention relates to an electric drive train which has such a fluid conveying device. In addition, the invention relates to a motor vehicle comprising a previously described fluid conveying device and / or a previously described electric drive train.

[0018] The invention is explained below using exemplary embodiments with reference to the figures. The figures are schematic representations and show: Fig. 1 shows a schematic diagram of a motor vehicle comprising an electric machine and a fluid conveying device; Fig. 2 a schematic diagram of a diagram of an operating parameter in different operating states; and Fig. 3 a schematic diagram of a flow chart of a method for determining a temperature.

[0019] Fig. 1 shows a schematic diagram of a motor vehicle 1 comprising an electric machine 2 designed as a traction drive or component of an electric drive arrangement, specifically as an electric axle drive. To supply the electric machine 2 with a fluid, in particular for temperature control and / or lubrication, for example for cooling, the motor vehicle 1 has a fluid conveying device 3 which is thermally connected to the electric machine 2 via a fluid circuit 4. A fluid, for example oil or water, generally a liquid, is conveyed through the fluid circuit 4 by means of a pump device 5. For example, the fluid can be supplied to the electric machine 2 via the fluid conveying device 3 in order to absorb heat from the electric machine 2 and dissipate it, for example by dissipating the heat to the environment via a heat exchanger.

[0020] The fluid conveying device 3, in particular the pump device 5, is connected to a control device 6, which is designed to control the operation and to monitor operating parameters of the pump device 5. The control device can be used to determine the temperature and thus be referred to as a determination device designed to determine the temperature or can comprise such a device. For this purpose, the pump device 5 is operated at a defined operating point, in particular at a certain pump speed. During operation of the pump device 5 at the defined operating point, at least one operating parameter of the pump device 5 is recorded, in particular a power consumption, for example the electrical current supplied to the pump device 5.Knowing the relationship between the power consumption of the pump device 5 and the temperature at the defined operating point, it is possible to determine the temperature of the fluid in the fluid circuit 4. This also makes it possible, for example, to indirectly determine the temperature of the electric machine 2.

[0021] As an alternative to operating the pump device 5 at a defined operating point, it is possible to switch from the defined operating point to at least one further operating point, i.e., for example, the pump speed of the pump device 5 is changed in a defined manner. In this embodiment, the time required for changing the operating points, for example, until the pump device 5 has adjusted to the changed pump speed, is measured or recorded as the operating parameter.

[0022] The relationship between the operating parameter of the pump device 5 and the temperature of the fluid is shown purely schematically in a diagram in Fig. 2. For example, the operating parameter is the electrical current plotted against the pump speed. Here, a first curve 7 denotes the current consumption of the pump device 5 against the speed at a first temperature and curve 8 denotes the current consumption of the pump device 5 against the pump speed at a second temperature, wherein the second temperature is higher than the first temperature. With knowledge of the behavior of the fluid, in particular its temperature-dependent viscosity, the temperature of the fluid can thus be determined for a specific pump speed, i.e. for a specific operating point, based on the operating parameter, i.e. based on the current made available to the pump device 5 or the current consumed by the pump device 5.

[0023] In principle, the temperature can be determined in a regular operating state, i.e., for any operating point where the relationship between the operating point, the power consumption, and the fluid temperature is known through a reference measurement, model, or simulation. It is also possible to assume a specific operating point in a measurement state, as shown, for example, for measuring points 9 and 10. Measuring points 9 and 10 can be specifically selected so that a gradient of the operating parameter can be advantageously evaluated.

[0024] Fig. 3 shows a schematic diagram of the process for determining the temperature, as already described, for example, in relation to Fig. 1, Fig. 2 was described.

[0025] The method can, for example, start in a block 11, in which an operating point of the pump device 5 is set or an existing operating point is changed to a second operating point. Subsequently, in a block 12, the operating parameter of the pump device 5 can be recorded, for example, an electrical operating parameter of the pump device 5, specifically the power consumption or an electrical current supplied to the pump device 5. If the temperature determination is based on a change in the operating point, for example, a change in the pump speed, a time measurement can be performed as the operating parameter or a time required for the change in the operating point can be recorded.

[0026] In a block 13, the temperature can then be determined based on the relationship between the recorded operating parameter and the temperature, in particular of the fluid, in the fluid circuit 4. For example, the relationship can be determined based on reference measurements, so that for different temperatures at the operating point or for different operating points, i.e. in particular different pump speeds, the operating parameter was determined at known temperatures. The temperatures for the combinations of operating parameter and operating point can, for example, be stored in a table. Thus, with knowledge of the pump speed and the current consumed by the pump device 5, the temperature can be read out. Alternatively, it is also possible to determine the relationship by means of simulation and / or a model.

[0027] Once the temperature has been determined, it can be output in block 14, ie displayed on a display device, fed to the control device 6 or another control device for a control or regulating task.

[0028] The advantages, details and features shown in the individual embodiments can be combined with one another as desired, are interchangeable and transferable to one another. Reference symbol 1 motor vehicle 2 electric machine 3 Fluid conveying device 4 Fluid circuit 5 Pump device 6 Control device 7.8 curve 9, 10 measuring point 11-14 blocks

Claims

[1] Method for determining a temperature of a fluid conveying device (3), in particular a temperature of a fluid guided in a fluid circuit (4) of the fluid conveying device (3), which fluid is conveyed by means of a pump device (5) in the fluid circuit (4) of the fluid conveying device (3), characterized by that the pump device (5) is operated at at least one defined operating point, wherein the temperature is determined based on an operating parameter of the pump device (5). [2] Method according to claim 1, characterized by that at least one electrical parameter, in particular a power consumption, of the pump device (5) is detected as an operating parameter. [3] Method according to claim 1 or 2, characterized by that a speed of the pump device (5) is regulated to a defined pump speed at the defined operating point. [4] Method according to one of the preceding claims, characterized bythat a relationship between the temperature and the recorded operating parameter is predetermined, in particular on the basis of a characteristic map measurement. [5] Method according to one of the preceding claims, characterized by that a relationship between temperature and the recorded operating parameter is determined on a model-based and / or simulation-based basis. [6] Method according to one of the preceding claims, characterized by that the operating parameter is recorded in a regular operating state of the pump device (5) or that a defined measuring state is carried out in which the defined operating point is set. [7] Method according to one of the preceding claims, characterized by that the temperature is determined exclusively on the basis of the detected operating parameter or that a reference temperature, in particular of a temperature sensor, is verified by means of the determined temperature. [8] Method according to one of the preceding claims, characterized by that starting from the at least one operating point, at least a second operating point is regulated, wherein a time measurement is recorded as the operating parameter, which describes the duration for the change in the operating point. [9] Fluid conveying device (3), in particular for a motor vehicle (1), comprising a fluid circuit (4) in which a fluid can be guided or is guided, wherein the fluid conveying device (3) has a pump device (5) which is designed to convey fluid in the fluid circuit (4) of the fluid conveying device (3), characterized by a determining device which is designed to determine a temperature based on an operating parameter of the pump device (5) at at least one defined operating point. [10] Electric drive train comprising a fluid conveying device (3) according to the preceding claim. [11] Motor vehicle (1) comprising a fluid conveying device (3) according to claim 9 and / or an electric drive train according to the preceding claim.

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