Method for determining at least one volumetric flow rate in device for hydraulic system, computer program product, computer device

Abstract

The invention relates to a method for determining at least one volumetric flow rate in a device (31) for a hydraulic system (1), in particular of a motor vehicle, comprising a first hydraulic line (20), which can be connected, on one hand, to a hydraulic pressure source for conveying a liquid medium, in particular having at least one pump (5, 6), the first hydraulic line (20) can be connected to at least one device to be cooled and / or lubricated on the other hand, and wherein a pressure-limiting valve (22) is associated with the first hydraulic line (20), which pressure-limiting valve has a tank connection for the liquid medium reservoir (9) and connects the first hydraulic line (20) to the tank connection when the hydraulic pressure in the first hydraulic line (20) exceeds a predetermined limit value, an orifice plate (23) is arranged in the first hydraulic line (20) downstream of the pressure-limiting valve (22), a throttle (30) is arranged or formed in the first hydraulic line (20) downstream of the orifice plate (23), having the following steps: determining a temperature of the medium in the reservoir (9); determining a total volume flow delivered by the hydraulic pressure source in the first hydraulic line (20) as a function of the temperature; determining a first partial volume flow discharged through the pressure limiting valve (22) into the reservoir (9); and determining a second partial volumetric flow rate flowing through the orifice plate (23) and the throttle (30) to the device as a difference between the total volumetric flow rate and the first partial volumetric flow rate.

Description

Field of the Invention

[0001] The present invention relates to a method for determining at least one volume flow rate in a device for a hydraulic system. Furthermore, the present invention relates to a computer program product and to a computer device for performing the method. Background Art

[0002] Hydraulic systems for motor vehicle power modules are known from the prior art, which have a hydraulic circuit for cooling and / or lubricating clutches and power units. In particular, power modules for hybrid vehicles are known, which have an internal combustion engine and an electric motor for selectively driving a motor vehicle. A power module of this type usually has clutches for separately disengaging and engaging the electric motor or the internal combustion engine with the power train of the motor vehicle. In order to cool and lubricate these clutches and the electric motor itself, a cooling and lubricating oil is required, which circulates in a cooling circuit. Here, the power module usually has separate cooling circuits for the individual clutches, wherein at least the clutch assigned to the electric motor and one or more clutches assigned to the internal combustion engine are each provided with a pump, usually electrically driven, for adjusting the cooling medium flow. These at least two pumps are usually controlled by a controller, wherein, in particular, the cooling medium flow is adjusted according to the rotational speed of the pumps. Summary of the Invention

[0003] It is an object of the present invention to provide a method for determining at least one volume flow rate in a device for an improved hydraulic system with lower complexity.

[0004] The object of the present invention is achieved by a method having the features of claim 1. A device is proposed, which has a first hydraulic line that can be connected on the one hand to a hydraulic pressure source for conveying a liquid medium, in particular having at least one pump, and on the other hand to at least one device to be cooled and / or lubricated. The first hydraulic line is provided with a pressure limiting valve, which has a storage tank connection end for a liquid medium reservoir. When the hydraulic pressure in the first hydraulic line exceeds a preset limit value, the pressure limiting valve connects the first hydraulic line to the storage tank connection end. A orifice plate is arranged in the first hydraulic line downstream of the pressure limiting valve, and a throttle section is arranged or designed in the first hydraulic line downstream of the orifice plate. The following method steps are specified: determining the temperature of the medium in the reservoir; determining the total volume flow rate conveyed through the hydraulic pressure source in the first hydraulic line based on this temperature; determining the first partial volume flow rate discharged through the pressure limiting valve into the reservoir; and determining the second partial volume flow rate flowing to the device through the orifice plate and the throttle section as the difference between the total volume flow rate and the first partial volume flow rate. By this method, a particularly advantageous, simple and feasible solution for determining the partial volume flow rate of the liquid medium flowing to the device is provided, which is only related to the input quantities such as the medium temperature, the total volume flow rate conveyed, and the partial volume flow rate discharged into the reservoir. Therefore, through the combination and arrangement of the pressure limiting valve, the orifice plate and the throttle section, a favorable correlation / dependence of the volume flow rate of the medium flowing to the device through the first hydraulic line on the medium temperature is achieved. The method according to the present invention is used to model this correlation. The second partial volume flow rate is limited by the pressure limiting valve as required. If the total volume flow rate is too large, the excess medium is directly guided back to the reservoir as the first partial volume flow rate. By combining a pressure limiting valve with an as constant as possible opening pressure before the orifice plate and a temperature-related backwater reverse flow pressure in the subsequent path in the direction of the throttle section after the orifice plate, a temperature-related pressure difference is generated at the orifice plate, and thus a temperature-related second partial volume flow rate flowing to the device is generated, thereby achieving supply to the device according to the temperature. Therefore, the pressure limiting valve and the orifice plate together with the throttle section are designed to adjust the second partial volume flow rate according to the temperature of the medium. The working principle of supplying the device according to the temperature is as follows, for example: the volume flow rate flowing through an ideal orifice plate is independent of the viscosity of the medium and is only determined by the geometry of the orifice plate, in particular its diameter. If the actual orifice plate is constructed as thin-walled as possible, its performance at least basically corresponds to that of an ideal orifice plate. The volume flow rate flowing through the throttle section is not only related to the geometry of the throttle path, but also has a great relationship with the viscosity of the medium before the throttle section at the same pressure. The colder the medium, the higher the viscosity, and the less the volume flow rate flowing through the throttle section. Therefore, less medium flows to the device at lower temperatures than at higher temperatures. In addition, the second partial volume flow rate is only related to the trigger pressure of the pressure limiting valve.This advantageous effect, namely, the medium flow that is temperature-related and thus viscosity-related, is automatically generated by the assembly of these three components. Preferably, the geometries of the orifice plate and the throttle section and the triggering pressure of the pressure limiting valve are coordinated with each other such that a preset temperature-related medium flow is fed to the device. In particular, the orifice plate diameter is selected such that, in the case of a high medium temperature (e.g., 100 °C), a volume flow sufficient for cooling is fed. At the same time, in the case of a low medium temperature (e.g., -30 °C), the throttle path only allows a small volume flow that is just sufficient for lubrication. Preferably, the triggering pressure of the pressure limiting valve is selected to be as small as possible, or the triggering pressure is minimized such that the pressure limiting valve can just still operate stably, so as to keep the energy requirement of the medium source as low as possible, for example. In order to correspondingly coordinate and optimize the throttle path, the orifice plate, and the triggering pressure, in particular, corresponding simulations and model calculations are carried out.

[0005] According to a preferred refinement of the invention, for a plurality of temperatures and total volume flows, the difference is determined as a family of characteristic curves empirically, by a system of equations, or by a neural network. Thereby, in particular, a particularly simple feasible solution is provided for selecting the optimal operating point of the device during operation, in particular for adjusting a sufficiently large total volume flow according to the family of characteristic curves to ensure the cooling of the device at a given temperature.

[0006] Particularly preferably, it is provided that the hydraulic pressure source has at least one pump, and the total volume flow is determined as the product of the working volume / stroke volume of the pump, the temperature-related volumetric efficiency, and the drive speed. Thereby, a particularly simple feasible solution for determining the total volume flow is provided.

[0007] According to a preferred refinement of the invention, a plurality of total volume flows are preset by a plurality of drive speeds. By means of the drive speed, a particularly simple feasible solution for changing the total volume flow is provided, so that the drive speed is an advantageous characteristic parameter.

[0008] Particularly preferably, value ranges that are allowed are preset respectively for a plurality of temperatures and / or drive speeds. Thereby, it is particularly advantageously ensured that the family of characteristic curves only contains the desired values, in particular the values expected during the subsequent operation of the device or the hydraulic system.

[0009] For example, the following allowable value ranges are preset for the temperature, i.e., corresponding to the expected or device-operating temperature ranges allowable in relation to the component, in particular from -30 °C to +140 °C. More preferably, the preset resolution (e.g., 1 °C) and the interval between the temperature values to be considered (e.g., 10 °C) or a plurality of temperature values to be considered are preset, and for the corresponding temperature values within this value range, the method according to the invention is carried out at the preset resolution. In particular, the allowable value range for the drive speed is selected according to the technically feasible value range for the corresponding pump. Alternatively, the allowable value range is selected for the total volume flow theoretically derived from the allowable drive speed, in particular from 0 l / min to 30 l / min. More preferably, the resolution of, for example, 0.1 l / min and the interval between the values to be considered of, for example, 0.5 l / min or a plurality of values to be considered are also preset here, and for all values within this value range, the method according to the invention is carried out. In particular, the method is carried out for all such specified or feasible combinations of temperature values with drive speed values or total volume flow values.

[0010] According to a preferred refinement of the invention, it is provided that the hydraulic pressure source has a second pump that is fluid-technologically parallel to the first pump, and the total volume flow is determined as the sum of the respective products of the volumetric efficiency, drive speed, and working volume of each pump. Thereby, a particularly simple feasible solution is provided for determining the total volume flow in the case where the hydraulic pressure source has more than one pump.

[0011] It is particularly preferably provided that the first partial volume flow is determined according to the change in the liquid level of the reservoir. Thereby, a particularly simple feasible solution is provided for determining the first partial volume flow. For example, the liquid level is determined by a liquid level sensor assigned to the reservoir.

[0012] According to a preferred refinement of the invention, it is provided that the temperature of the device is determined according to the second partial volume flow and the electrical or mechanical power output of the device. Thereby, a particularly advantageous and simple possibility is provided for checking whether the device temperature is within the allowable operating temperature range, i.e., in particular whether the device is sufficiently cooled, at the selected or given operating point composed of the total volume flow and the temperature.

[0013] The computer program product according to the invention for running on a computer device having the features of claim 9 is distinguished in that, when used as prescribed, it carries out the method according to the invention. Thereby, the advantages already mentioned are obtained.

[0014] The computer device having the features of claim 10 is distinguished in that the computer device is specifically designed to carry out the method according to the invention or to run the computer program product according to the invention. Thereby, the advantages already mentioned above are also obtained. Description of the Drawings

[0015] In particular, other advantages and preferred features and combinations of features result from the above description and the claims. The invention will now be explained in more detail with reference to the drawings. Among them:

[0016] Figure 1 shows a circuit diagram of an advantageous hydraulic system,

[0017] Figure 2 shows a detail view of the hydraulic system, and

[0018] Figure 3 shows an advantageous method for determining at least one volume flow rate in the hydraulic system. Detailed Description of the Invention

[0019] Figure 1 shows a circuit diagram of an advantageous hydraulic system 1, which is designed to be used in the power module of a motor vehicle. The hydraulic system 1 has a first clutch 2, a second clutch 3 and a third clutch 4.

[0020] The first clutch 2 and the second clutch 3 are assigned to a first power unit (not shown), in particular an internal combustion engine, and the third clutch 4 is assigned to a second power unit 28, in particular an electric motor, in order to selectively couple the power unit to the motor vehicle transmission.

[0021] Furthermore, the hydraulic system 1 has a common hydraulic circuit for cooling and / or lubricating at least the clutches 2, 3, 4 and the second power unit 28. Here, the hydraulic circuit has a pump 5 for conveying a liquid medium. In addition, a further pump 6 is provided, which is optional and in this example is provided for supplying the medium to other motor vehicle components (not shown).

[0022] The two pumps 5, 6 are arranged on a common shaft driven by an electric motor 7. The electric motor 7 is preferably speed-controlled, so that the delivery power of the pumps 5, 6 and the corresponding cooling medium flow are related to the speed of the electric motor 7.

[0023] The two pumps 5, 6 are connected to a storage tank or reservoir 9 with an intermediate suction strainer 8 interposed. The storage tank or reservoir serves as a storage container or sump for the medium, and the medium is preferably stored therein under no pressure.

[0024] Furthermore, the hydraulic circuit has a controllable valve 10 interposed between the clutches 2, 3, 4 and the pump 5, which valve is used to adjust at least the cooling medium flow for the clutches 2, 3, 4 and the second power unit.

[0025] In this example, the valve 10 is designed as an electrically actuated five-port three-position valve, which has three output ports 11, 12, 13 and two input ports 14, 15. Here, the first output port 11 is assigned to the first clutch 2, the second output port 12 is assigned to the second clutch 3, and the third output port 13 is assigned to the third clutch 4. Both the first input port 14 and the second input port 15 are assigned to the pump 5. According to an embodiment not shown, only one input port assigned to the pump 5 is provided. Then, the valve 10 is designed as a four-port three-position valve.

[0026] Therefore, the valve 10 has three possible switching positions 16, 17, 18. In the first switching position 16 of the valve 10, the medium reaches the first output port 11 from the second input port 15 and flows only to the first clutch 2 through the second hydraulic line 19.

[0027] In the second switching position 17 of the valve 10, the medium reaches the third output port 13 from the first input port 14 and flows only first to the third clutch 4 and then to the second power unit 28 through the first hydraulic line 20. That is, it is specified that the medium flows not only through the third clutch 4 but also through the second power unit 28.

[0028] For this purpose, for example, a deflector plate and a cross-sectional change are provided to distribute and guide the coolant flow. Therefore, in particular, first the third clutch 4 and then the second power unit 28 are locally flowed through by a part of the coolant flow.

[0029] In particular, a part of the coolant flow is branched off and only supplied to the second power unit 28, so that the medium is supplied to the third clutch 4 and the second power unit 28 as required.

[0030] In the third switching position 18 of the valve 10, the medium reaches the second output port 12 from the second input port 15 and flows only to the second clutch 3 through the third hydraulic line 21.

[0031] After the medium has flowed through the clutches 2, 3, 4 and the second power unit 28 respectively, the medium is guided back to the reservoir 9, as shown in Figure 1 as shown.

[0032] In the first hydraulic line 20, downstream, i.e., in the direction towards the third clutch 4 and the second power unit 28, as a module 29, a pressure limiting valve 22 is first arranged and then an orifice plate 23 is arranged. Finally, a throttle portion 30 formed by the hydraulic lines extending to the clutch 4 and the second power unit 28 is arranged further downstream.

[0033] The pressure limiting valve 22, the orifice plate 23 and the throttle section 30 are components of the advantageous device 31 of the hydraulic system 1 and are themselves designed to adjust the volume flow rate of the medium flowing to the third clutch 4 according to the temperature of the medium, as described at the beginning. The pressure limiting valve redirects excessive medium back to the reservoir 9 again and is designed as a seat valve in this example.

[0034] Figure 2 A detail view of the module 29 in the second flow path 20 is shown, and the flow direction of the second flow path is indicated by an arrow. The medium flows into the region 25 through the inlet 24. The pressure limiting valve 22 designed as a seat valve is seated above the region 25.

[0035] As long as the force generated by the pressure exerted by the medium on the valve disk 26 of the pressure limiting valve 22 is less than the force exerted on the valve disk by the spring force of the spring element 27, the valve disk 26 seals the region 25, and the spring element is arranged on the side of the valve disk 26 remote from the region 25.

[0036] If the pressure exerted by the medium is greater than the pressure exerted by the spring element 27 corresponding to the spring force, the valve disk is displaced, so that the excess medium flows into the pressure limiting valve 22 through the resulting opening, and the pressure limiting valve is in turn fluid-technically connected to the reservoir 9 as described above, so that the medium flows back to the reservoir 9.

[0037] Continuing along the second flow path 20, the orifice plate 23 can be seen. In this example, the orifice plate has a constant flow cross-section and serves as an outlet for the medium to flow out of the region 25.

[0038] Here, in this example, a tubular adapter element 32 is arranged downstream of the orifice plate 23 as part of the throttle section 30 in the first hydraulic line 20, wherein the adapter element 32 fluid-technically connects the device 31 to the hydraulic lines extending to the clutch 4 and the second power unit 28.

[0039] Here, the adapter element 32 has a first open end 33 with a first cross-section assigned to the orifice plate 23 and a second open end 34 with a second cross-section assigned to the respective hydraulic lines. In this example, the second cross-section is smaller than the first cross-section. In this example, the adapter element 32 has a continuously decreasing cross-section along its longitudinal extension direction, i.e., along the flow direction, i.e., is designed to be conical.

[0040] By appropriately selecting the second cross-section and the geometric design of the adapter element 32, on the one hand, it is ensured that the device 31 is advantageously and simply adapted to the hydraulic lines with corresponding cross-sections, and on the other hand, it provides an advantageous additional influencing possibility to affect the throttle path and thus the characteristics of the throttle section 30. Therefore, advantageously, the throttle section 30 can be adapted to the cooling and / or lubrication requirements of the clutch 4 and the second power unit 28.

[0041] at last, Figure 3 An advantageous method for determining at least one volume flow in a hydraulic system 1 is also shown. The method starts with step S1. In step S1, permissible value ranges and corresponding value pairs are respectively predefined for the medium temperature and for the drive speed of at least one of the pumps 5, 6. For a plurality of temperatures and drive speeds within these value ranges, method steps S2 to S5 are carried out, as described below.

[0042] In step S2, the temperature of the medium in the reservoir 9 is first determined. Subsequently, the total volume flow delivered by the pumps 5, 6 in the first hydraulic line 20 is determined as a function of this temperature. The total volume flow is determined as the product of the temperature-dependent volumetric efficiency, the drive speed and the displacement of the pumps 5, 6. If two pumps 5, 6 are considered, the total volume flow is determined as the sum of the corresponding products.

[0043] In step S3, a first partial volume flow is determined which is discharged into the reservoir 9 via the pressure-limiting valve 22. This first partial volume flow is determined, for example, from a change in the filling level of the reservoir 9 by means of a corresponding sensor.

[0044] In step S4, the second partial volume flow to the device via the orifice 23 and the throttle 30 is determined as the difference between the total volume flow and the first partial volume flow. In step S5, the second partial volume flow is stored in a corresponding characteristic diagram.

[0045] Starting from step S4, in optional step S7, the temperature of the device is determined as a function of the second partial volume flow and the electrical or mechanical power output of the device. This temperature is stored in a corresponding characteristic diagram in step S8.

[0046] In a step S6 following steps S5 and S8 , it is checked whether a second partial volume flow has been calculated for all preset value pairs for temperature and drive speed that are within the permissible value range.

[0047] If this is not the case, the method jumps back to step S2, in which at least one of the parameters is changed accordingly, for example the drive speed or the temperature is increased or decreased. In this case, the second partial volume flow is determined in particular empirically, by a set of equations or by a neural network.

[0048] If it is determined in step S6 that the characteristic map or the characteristic maps are complete, ie the corresponding partial volume flows or temperatures have been recorded for all value pairs, the method ends in step S9 .

[0049] List of reference numerals:

[0050] 1 Hydraulic system

[0051] 2 First clutch

[0052] 3 Second clutch

[0053] 4 Third clutch

[0054] 5 Pump

[0055] 6 Additional pump

[0056] 7 Electric motor

[0057] 8 Suction strainer

[0058] 9 Reservoir

[0059] 10 Valve

[0060] 11 First output section

[0061] 12 Second output section

[0062] 13 Third output section

[0063] 14 First input section

[0064] 15 Second input section

[0065] 16 First switching position

[0066] 17 Second switching position

[0067] 18 Third switching position

[0068] 19 Second hydraulic line

[0069] 20 First hydraulic line

[0070] 21 Third hydraulic line

[0071] 22 Pressure limiting valve

[0072] 23 Orifice plate

[0073] 24 Inlet

[0074] 25 Area

[0075] 26 Valve disc

[0076] 27 Spring element

[0077] 28 Second power unit

[0078] 29 Module

[0079] 30 Throttle section

[0080] 31 Equipment

[0081] 32 Adaptation element

[0082] 33 First end portion

[0083] 34 Second end portion.

Claims

1. A method for determining at least one volume flow rate in a device (31) for a hydraulic system (1), in particular a hydraulic system of a motor vehicle, wherein, The device has a first hydraulic line (20) which can be connected on the one hand to a hydraulic pressure source for conveying a liquid medium and on the other hand to at least one device to be cooled and / or lubricated. The hydraulic pressure source especially has at least one pump (5, 6). A pressure limiting valve (22) is arranged in the first hydraulic line (20). The pressure limiting valve has a storage tank connection end for a storage tank (9) of the liquid medium. When the hydraulic pressure in the first hydraulic line (20) exceeds a preset limit value, the pressure limiting valve connects the first hydraulic line (20) to the storage tank connection end. A orifice plate (23) is arranged in the first hydraulic line (20) downstream of the pressure limiting valve (22), and a throttle section (30) is arranged or formed in the first hydraulic line (20) downstream of the orifice plate (23). The method has the following steps: - Determine the temperature of the medium in the storage tank (9); - Determine the total volume flow rate conveyed by the hydraulic pressure source in the first hydraulic line (20) according to the temperature; - Determine the first partial volume flow rate discharged into the storage tank (9) through the pressure limiting valve (22); and - Determine the second partial volume flow rate flowing to the device through the orifice plate (23) and the throttle section (30) as the difference between the total volume flow rate and the first partial volume flow rate.

2. The method according to claim 1, characterized in that, For a plurality of temperatures and total volume flow rates, the difference is determined as a characteristic curve family empirically, by an equation set or by a neural network.

3. The method according to any one of the preceding claims, characterized in that, The hydraulic pressure source has at least one pump (5, 6), and the total volume flow rate is determined as the product of the temperature-dependent volumetric efficiency, drive speed and working volume of the pump (5, 6).

4. The method according to claims 2 and 3, characterized in that, A plurality of total volume flow rates are preset by a plurality of drive speeds.

5. The method according to claim 4, characterized in that, For a plurality of temperatures and / or drive speeds, an allowable value range is preset respectively.

6. The method according to any one of claims 3 to 5, characterized in that, The hydraulic pressure source has a second pump (6) which is fluid-technologically parallel to the first pump (5), and the total volume flow rate is determined as the sum of the respective products of the volumetric efficiency, drive speed and working volume of each pump (5, 6).

7. The method according to any one of the preceding claims, characterized in that, Determine the first partial volume flow rate according to the change in the liquid level of the storage tank (9).

8. The method according to any one of the preceding claims, characterized in that, Determine the temperature of the device according to the second partial volume flow rate and the electrical or mechanical power output of the device.

9. A computer program product for running on a computer device, characterized in that, A computer program product, when used as prescribed, executes the method according to any one of the above claims.

10. A computer device, in particular a control device, characterized in that, A computer device is specifically designed to run the computer program product according to claim 9.

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