Liquid pump, assembly and method

Abstract

A liquid pump (12) is specified, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, comprising a pump housing (16) in which a pump chamber (18) and a pump rotor (20) are arranged, wherein a first temperature sensor (24) and a second temperature sensor (26) are arranged in a flow path of the liquid flowing through the liquid pump (12), wherein the temperature sensors (24, 26) each have a different, non-linear temperature characteristic curve. An assembly comprising a liquid pump (12) and a method for ascertaining the temperature of a liquid conveyed by a liquid pump (12) are furthermore specified.

Description

[0001] Liquid pump, assembly and method

[0002] The invention relates to a liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, and an assembly comprising a liquid pump and a measuring unit and finally a method for ascertaining the temperature of a fluid conveyed by a liquid pump.

[0003] Liquid pumps for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle generally comprise a pump housing comprising a pump chamber in which a pump rotor is arranged, and an outlet channel in which a temperature sensor is arranged. The temperature sensor is used to monitor the temperature of the liquid being conveyed, which is usually a hydraulic fluid, such as oil.

[0004] By way of example, the temperature sensor is an NTC sensor, that is to say a temperature sensor that has an NTC thermistor as an essential component. Temperature sensors of this kind are particularly cost-effective. However, such temperature sensors have the disadvantage that, due to their non-linear characteristic curve, they do not have an equally high resolution over the entire measuring range from -40°C to 150°C.

[0005] Alternatively, it is possible to use active temperature sensors, which provide a good resolution over the entire measuring range. Active temperature sensors are comparatively expensive, however.

[0006] It is therefore an object of the invention to measure the temperature of a hydraulic liquid in a liquid pump over a measuring range of at least -40°C to 150°C in a cost-effective manner with the highest possible accuracy.

[0007] This object is achieved according to the invention by a liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, comprising a pump housing in which a pump chamber and a pump rotor are arranged, wherein a first temperature sensor and a second temperature sensor are arranged in a flow path of the liquid flowing through the liquid pump, wherein the temperature sensors each have a different, non-linear temperature characteristic curve. This can be used to use the signal from different temperature sensors in different temperature ranges, specifically in each case the range of the temperature characteristic curve that provides the higher resolution.

[0008] In particular, a different temperature range is covered by each of the two temperature sensors, and so the temperature of a liquid flowing through the liquid pump is able to be measured with sufficiently high accuracy over the entire measuring range.

[0009] The measuring range extends in particular from -40° to 150°C.

[0010] By way of example, the first temperature sensor has a higher resolution than the second temperature sensor in a first continuous temperature range, and the second temperature sensor has a higher resolution than the first temperature sensor in a second continuous temperature range. The first temperature range and the second temperature range are in particular different. That is to say that the first temperature range and the second temperature range do not overlap, but preferably directly adjoin one other. This allows a particularly wide temperature range to be covered overall.

[0011] Each temperature sensor preferably covers a measuring range that extends over a range with a temperature difference of 80 to 120°C.

[0012] According to one embodiment, each temperature sensor comprises an NTC thermistor. Temperature sensors of this kind are particularly cost-effective and provide sufficiently accurate measurement results at least within a specified temperature range.

[0013] By way of example, the NTC thermistors are identical. This can also contribute to a cost saving, since fewer different components need to be stored, which is advantageous in terms of storage costs.

[0014] The NTC thermistors of each temperature sensor may be connected in series with an additional resistor, wherein the two additional resistors are different. It is possible to shift the temperature characteristic curve of each temperature sensor into a desired range by way of appropriate design of the additional resistors. Both temperature sensors are preferably arranged in an outlet channel that is connected to the pump chamber, in particular at a maximum distance of 5 mm. The two temperature sensors therefore measure the temperature of the liquid in direct proximity to one another. This makes it possible to relate the measured values from the first temperature sensor and the measured values from the second temperature sensor to one another. In other words, the two temperature sensors may replace a single active temperature sensor due to their direct proximity to one another.

[0015] Alternatively, the temperature sensors are accommodated on a printed circuit board arranged inside a wet chamber of the fluid pump. The printed circuit board being flooded in the hydraulic fluid, the measure of the temperature is therefore improved and accurate. Placing the temperature sensors directly on the printed circuit board makes the fluid pump more compact.

[0016] The temperature sensors may be accommodated in a common housing. As a result, the temperature sensors are able to be handled as a single unit during assembly, as a result of which the assembly is simplified. Furthermore, the temperature sensors being accommodated in a common housing also allows them to be arranged in direct proximity to one other.

[0017] According to a preferred embodiment, the fluid conveyed by the fluid pump is oil, for example dielectric oil. Other types of liquid are possible.

[0018] The object is furthermore achieved according to the invention by an assembly comprising such a liquid pump and comprising a measuring unit, which is configured to capture the measured values from the two temperature sensors and, depending on a number of measurement points provided by the individual temperature sensors, to take into account the measured value from that temperature sensor that has a higher resolution in a present measuring range. As has already been described in connection with the liquid pump according to the invention, this makes it possible to determine the temperature of a liquid flowing through the liquid pump over an entire measuring range with a high level of accuracy.

[0019] The object is furthermore achieved according to the invention by a method for ascertaining the temperature of a liquid conveyed by a liquid pump by means of an assembly according to the invention, wherein the first temperature sensor provides a higher number of measurement points in a first temperature range and the second temperature sensor provides a higher number of measurement points in a second temperature range, wherein the measuring unit takes into account the measured values from the first temperature sensor in the first temperature range and the measured values from the second temperature sensor in the second temperature range.

[0020] Consequently, as has already been explained in connection with the assembly, the measured value from that temperature sensor that has the higher resolution in the range of the present temperature is used.

[0021] According to one embodiment, one of the two temperature sensors measures a voltage value across the NTC thermistor and the other of the two temperature sensors measures a voltage value across the additional resistor. This has effects on the voltage value measured in each case and thus on the temperature characteristic curve of the respective temperature sensor. In particular, the measurement of the voltage value across the additional resistor results in a shift in the temperature characteristic curve compared to the measurement of the voltage value at the NTC thermistor.

[0022] Further advantages and features of the invention will emerge from the following description and from the accompanying drawings, to which reference is made. In the drawings: figure 1 schematically shows an assembly according to the invention comprising a liquid pump according to the invention, figure 2 shows a housing for accommodating two temperature sensors, figure 3 shows a circuit diagram of a measurement set-up comprising a first and a second temperature sensor, figure 4 shows the characteristic curves of the two temperature sensors, figure 5 shows a graph to illustrate a measurement resolution of the first and the second temperature sensor, and figure 6 schematically shows an assembly according to the invention comprising a different liquid pump.

[0023] Figure 1 illustrates an assembly 10 comprising a liquid pump 12 and a measuring unit 14.

[0024] The liquid pump 12 is suitable for providing a supply of a hydraulic fluid to a transmission of an electric or hybrid drive module of a motor vehicle, for example to lubricate bearing points, to provide a coolant flow for a clutch, or to generate a pressure medium flow for activating an actuator.

[0025] The liquid pump 12 has a pump housing 16 in which a pump chamber 18 and a pump 20 are arranged.

[0026] The pump rotor 20 comprises a rotor 19 of an electric motor 21 , a shaft 22 driven by the rotor 19 and a pump impeller 23, which rests on the shaft 22 and the hydraulic fluid is conveyed by the rotation thereof.

[0027] A first temperature sensor 24 and a second temperature sensor 26 are arranged in an outlet channel 25 connected to the pump chamber 18.

[0028] The measuring unit 14 is configured to evaluate the temperature signals from the temperature sensors 24, 26, as will be explained in detail below.

[0029] The basic functionality of a liquid pump 12 of this kind is well known, which is why, for the sake of simplicity, a detailed description thereof is omitted. A corresponding liquid pump 12 is described, for example, in DE 10 2020 106 849 A1.

[0030] Figure 2 shows a housing 27, in which the two temperature sensors 24, 26 are accommodated.

[0031] It can also be seen in figure 2 that the two temperature sensors 24, 26 are arranged in direct proximity to one another.

[0032] Figure 3 shows a circuit diagram of a measurement set-up for measuring the temperature signals provided by the temperature sensors 24, 26.

[0033] It is clear from figure 3 that each temperature sensor 24, 26 comprises an NTC thermistor 28, 29 and a further resistor 30, 31. The NTC thermistor 28, 29 and the further resistor 30, 31 of a temperature sensor 24, 26 are each connected in series.

[0034] By way of example, the NTC thermistors 28, 29 are identical. However, it is also conceivable that the two NTC thermistors 28, 29 are different.

[0035] In the exemplary embodiment, the nominal resistance of each NTC thermistor is 10 kohms.

[0036] In the exemplary embodiment, the further resistor 30 of the first temperature sensor 24 is 1000 ohms, while the further resistor 31 of the second temperature sensor 26 is 22 kohms.

[0037] By way of example, a voltage of 5 volts is present at each temperature sensor 24, 26 during operation.

[0038] The measuring unit 14 measures a voltage value of the first temperature sensor 24 across the NTC thermistor 28 and a voltage value from the second temperature sensor 26 across the additional resistor 31.

[0039] A corresponding temperature characteristic curve 32 of the first temperature sensor 24 and a temperature characteristic curve 34 of the second temperature sensor 26 are illustrated in figure 4. In particular, in the graph shown in figure 4, the voltage profile is plotted over the temperature for each temperature sensor 24, 26.

[0040] It can be seen in figure 4 that the two temperature sensors 24, 26 each have a different, non-linear temperature characteristic curve. As a result, the high resolution region of the temperature characteristic curve is in a different temperature range for each of the two temperature sensors 24, 26.

[0041] In a temperature range of -40°C to 45°C, the temperature characteristic curve 34 of the second temperature sensor 26 has a gradient that is greater in terms of absolute value than the temperature characteristic curve 32 of the first temperature sensor 24. This means that the second temperature sensor 26 has a higher resolution in this temperature range than the first temperature sensor 24.

[0042] In a temperature range of 45°C to 150°C, the temperature characteristic curve

[0043] 32 of the first temperature sensor has a gradient that is greater in terms of absolute value than the temperature characteristic curve 34 of the second temperature sensor. The first temperature sensor 24 therefore has a higher resolution in this temperature range.

[0044] This is also clear from figure 5, in which, for each temperature sensor 24, 26, a number of measurement points provided by the respective temperature sensor 24, 26 is plotted per temperature difference of 5°C. The left-hand column in the graph in each case illustrates the number of measurement points from the first temperature sensor 24 and the right-hand column in each case illustrates the number of measurement points from the second temperature sensor 26.

[0045] The second temperature sensor 26 provides a higher number of measurement points than the first temperature sensor 24 in a temperature range of -40°C to 45°C, and the first temperature sensor 24 provides a higher number of measurement points than the second temperature sensor 26 in a temperature range of 45°C to 150°C.

[0046] This means that at a temperature of approximately 45°C, a change takes place to the effect that the resolution of the first temperature sensor 24 exceeds the resolution of the second temperature sensor 26; below this threshold, the temperature sensor 26 has the higher resolution.

[0047] By way of example, a 12-bit A / D converter with 4096 steps is used to capture the temperature signals.

[0048] The measured values from both temperature sensors 24, 26 are captured continuously.

[0049] However, the measuring unit 14 only takes into account the measured values from that temperature sensor 24, 26 that provides the higher number of measurement points.

[0050] Specifically, the measuring unit 14 compares the number of measurement points from the first temperature sensor 24 with the number of measurement points from the second temperature sensor 26, and only the measured value from the temperature sensor that provides the higher number of measurement points is forwarded for processing. For this purpose, the measuring unit 14 is accordingly configured to capture the measured values from the two temperature sensors 24, 26 and, depending on a number of measurement points provided by the individual temperature sensors 24, 26, to take into account the measured value from that temperature sensor that has a higher resolution in a present measuring range.

[0051] Provision may also be made for a fixed temperature limit value to be stored in the measuring unit 14, which reflects the temperature beyond which the higher resolution “changes” from one temperature characteristic curve to the other. The measuring unit 14 then takes into account that temperature characteristic curve that has the higher resolution below the temperature limit value and the other temperature characteristic curve above the temperature limit value.

[0052] Figure 6 schematically shows another type of liquid pump 12 that is intended to be used in a motor vehicle to deliver a hydraulic fluid to transmission components. The hydraulic fluid can perform lubricating or cooling functions or be used to actuate actuators.

[0053] The liquid pump 12 has a pump housing 16 in which a pump chamber 18 and a pump rotor 20 are arranged. The pump rotor 20 comprises a rotor 19 of an electric motor 21 , a shaft 22 driven by the rotor 19 and a pump impeller 23, which rests on the shaft 22 and the hydraulic fluid is conveyed by the rotation thereof. The liquid pump 12 can be a gerotor pump, a vane pump, or other type of pump.

[0054] The liquid pump 12 draws in the hydraulic fluid via an inlet channel 33 and delivers it via an outlet channel 25.

[0055] The liquid pump 12 is driven by an electric motor 21. The electric motor 21 is arranged in a wet chamber 34, i.e. an area within the housing 16 which is at least substantially filled with hydraulic fluid during operation. The wet chamber 34 is hydraulically connected to the pump chamber 18. In other words, the fluid from the pump chamber 18 can circulate within the wet chamber 34.

[0056] A circuit board 35 is arranged inside the wet chamber 34, on which various electronic or electrical components 24, 26, 36 are accommodated. These are used to control the electric motor 21 and are connected to a control unit. One of the components 36 is a Hall sensor, which can be used to detect the rotation of the shaft 22. The main difference from the previous embodiment is that a first temperature sensor 24 and a second temperature sensor 26 are accommodated on the printed circuit board 35. The printed circuit board 35 being flooded in the hydraulic fluid, the measure of the temperature is therefore improved and accurate. The temperature sensors 24, 26 are electrically connected to a measuring unit 14, which can be designed separately from the printed circuit board 35 or can also be integrated into it. The measuring unit 14 is configured to evaluate the temperature signals from the temperature sensors 24, 26.

[0057] The operation of the temperature sensors 24, 26 is identical to that described in relation to Figures 1 to 5, only the location is different.

Claims

Patent Claims1. Liquid pump (12), in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, comprising a pump housing (16) in which a pump chamber (18) and a pump rotor (20) are arranged, wherein a first temperature sensor (24) and a second temperature sensor (26) are arranged in a flow path of the liquid flowing through the liquid pump (12), wherein the temperature sensors (24, 26) each have a different, non-linear temperature characteristic curve.

2. Liquid pump according to claim 1 , characterized in that the first temperature sensor (24) has a higher resolution than the second temperature sensor (26) in a first continuous temperature range and the second temperature sensor (26) has a higher resolution than the first temperature sensor (24) in a second continuous temperature range.

3. Liquid pump (12) according to either of the preceding claims, characterized in that each temperature sensor (24, 26) comprises an NTC thermistor (28, 29).

4. Liquid pump (12) according to claim 3, characterized in that the NTC thermistors (28, 29) are identical.

5. Liquid pump (12) according to claim 3 or 4, characterized in that the NTC thermistor (28, 29) of each temperature sensor (24, 26) is connected in series with an additional resistor (30, 31), wherein the two additional resistors (30, 31) are different.

6. Liquid pump (12) according to one of the preceding claims, characterized in that both temperature sensors (24, 26) are arranged in an outlet channel (25) connected to the pump chamber (18).

7. Liquid pump (12) according to one of the preceding claims, characterized in that the temperature sensors (24, 26) are accommodated in a common housing (27).

8. Liquid pump (12) according to one of the claim 1 to 5, characterized in that the temperature sensors (24, 26) are accommodated on a printed circuit board (35) arranged inside a wet chamber (34) of the liquid pump (12).

9. Assembly (10) comprising a liquid pump (12) according to one of the preceding claims and comprising a measuring unit (14), which is configured to capture the measured values from the two temperature sensors (24, 26) and, depending on a number of measurement points provided by the individual temperature sensors (24, 26), to take into account the measured value from that temperature sensor (24, 26) that has a higher resolution in a present measuring range.

10. Method for ascertaining the temperature of a liquid conveyed by a liquid pump (12) by means of an assembly (10) according to claim 9, wherein the first temperature sensor (24) provides a higher number of measurement points in a first temperature range and the second temperature sensor (26) provides a higher number of measurement points in a second temperature range, wherein the measuring unit (14) takes into account the measured values from the first temperature sensor (24) in the first temperature range and the measured values from the second temperature sensor (26) in the second temperature range.

11. Method according to claim 10 for ascertaining the temperature of a liquid conveyed by a liquid pump (12) according to claim 5, characterized in that one of the two temperature sensors (24, 26) measures a voltage value across the NTC thermistor (28, 29) and the other of the two temperature sensors (24, 26) measures a voltage value across the additional resistor (30, 31).

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