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

Abstract

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

Description

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

[0002] Hydraulic systems for motor vehicle drive modules are known from the prior art. These systems have hydraulic circuits for cooling and / or lubricating clutches and drive motors. In particular, drive modules for hybrid vehicles are known, which have an internal combustion engine and an electric motor for selectively driving the motor vehicle. Such drive modules typically each have clutches for disconnecting and connecting the electric motor of the internal combustion engine to a drive train of the motor vehicle. Cooling and lubricating oil, which circulates in cooling circuits, is required to cool and lubricate the clutches and the electric motor itself.The drive module typically has separate cooling circuits for the clutches, with at least one pump, usually driven by an electric motor, being assigned to the clutch assigned to the electric motor and the clutch(es) assigned to the internal combustion engine for adjusting a cooling medium flow. The at least two pumps are typically controlled via a control unit, with the cooling medium flow being adjusted, in particular, depending on the speed of the pumps.

[0003] From the published patent application DE 10 2008 000 679 A1, a hydraulic control arrangement for controlling a variable fluid volume flow to a consumer is known, comprising a hydraulically pilot-operated control valve connected to a fluid supply, wherein a first, independent control valve is designed to deliver a predetermined initial volume flow without a pilot pressure, wherein this first control valve delivers a continuously increasing volume flow with a continuous increase in the variable pilot pressure, and wherein at least one second independent, likewise hydraulically pilot-operated control valve is designed to be activated in a predetermined range of the variable pilot pressure.

[0004] The invention is based on the object of providing a method for determining at least one volume flow in a device for an improved hydraulic system which has a reduced complexity.

[0005] The object underlying the invention is achieved by a method having the features of claim 1. A device is provided, comprising a first hydraulic line which can be connected to a hydraulic pressure source, in particular having at least one pump, for conveying a liquid medium on the one hand and to at least one device to be cooled and / or lubricated on the other hand, wherein the first hydraulic line is assigned a pressure relief valve which has a tank connection to a reservoir for the liquid medium and connects the first hydraulic line to the tank connection when a hydraulic pressure in the first hydraulic line exceeds a predetermined limit value, wherein an orifice is arranged in the first hydraulic line downstream of the pressure relief valve, and wherein a throttle is arranged or formed in the first hydraulic line downstream of the orifice.The following method steps are provided: determining a temperature of the medium in the reservoir, determining a total volume flow delivered by the hydraulic pressure source in the first hydraulic line as a function of the temperature, determining a first partial volume flow delivered into the reservoir through the pressure relief valve, and determining a second partial volume flow through the orifice and the throttle to the device as a difference between the total volume flow and the first partial volume flow. The method provides a particularly advantageous, simple option for determining a partial volume flow of the liquid medium to the device, which depends solely on the input variables of the temperature of the medium, the total volume flow delivered, and the partial volume flow delivered into the reservoir.The combination and arrangement of the pressure relief valve, orifice, and throttle achieves an advantageous dependence of the volume flow of a medium flowing through the first hydraulic line to the device on the temperature of the medium. The method according to the invention serves to model this dependence. The pressure relief valve limits the second partial volume flow as needed. If the total volume flow is too large, excess medium is returned directly to the reservoir as the first partial volume flow.The combination of a pressure relief valve with a preferably constant opening pressure upstream of an orifice and a temperature-dependent backpressure from the downstream section after the orifice in the direction of the throttle results in a temperature-dependent differential pressure at the orifice and thus a temperature-dependent second partial volume flow to the device, thus achieving a temperature-dependent supply to the device. Together with the throttle, the pressure relief valve and the orifice are designed to adjust the second partial volume flow depending on the temperature of the medium. The temperature-dependent supply to the device works as follows, for example: the volume flow through the ideal orifice is independent of the viscosity of the medium and is determined solely by the geometry of the orifice, in particular its diameter.If the real orifice plate is designed with as thin a wall as possible, its behavior corresponds at least largely to that of the ideal orifice plate. On the other hand, the volume flow through the throttle depends not only on the geometry of the throttle section, but also strongly on the viscosity of the medium at the same pressure upstream of the throttle. The colder the medium, the higher the viscosity and the lower the volume flow through the throttle. At low temperatures, therefore, less medium flows into the device than at high temperatures. In addition, the second partial volume flow depends only on the trigger pressure of the pressure relief valve. The advantageous effect, i.e. a temperature- and thus viscosity-dependent media flow, arises automatically from the arrangement of the three components.The geometry of the orifice and throttle as well as the trigger pressure of the pressure relief valve are preferably coordinated in such a way that a predetermined, temperature-dependent media flow is supplied to the device. The orifice diameter is particularly selected such that when the medium is hot, for example 100 °C, a volume flow sufficiently high for cooling is supplied. At the same time, when the medium is cold, for example -30 °C, the throttle section only allows a small volume flow that just barely permits lubrication. The trigger pressure of the pressure relief valve is preferably selected to be as small as possible or minimized such that the pressure relief valve still functions robustly, for example in order to keep the energy consumption of a media source as low as possible. Appropriate simulations and model calculations are carried out in particular to coordinate and optimize the throttle section, orifice and trigger pressure.

[0006] According to a preferred development of the invention, the difference for a plurality of temperatures and total volume flows is determined empirically as a characteristic map, using a system of equations, or using a neural network. This then creates a particularly simple possibility for selecting an optimal operating point for the device during operation, in particular for setting a sufficiently high total volume flow depending on the characteristic map to ensure cooling of the device at a given temperature.

[0007] Particularly preferably, the hydraulic pressure source comprises at least one pump, and the total volume flow is determined as the product of a temperature-dependent volumetric efficiency, a drive speed, and a displacement of the pump. This provides a particularly simple method for determining the total volume flow.

[0008] According to a preferred development of the invention, the plurality of total volume flows are predetermined by a plurality of drive speeds. The drive speed provides a particularly simple way of varying the total volume flow, thus representing an advantageous parameter.

[0009] Particularly preferably, it is provided that permissible value ranges are specified for the plurality of temperatures and / or drive speeds. This particularly advantageously ensures that the characteristic map contains only the desired values, in particular those to be expected during later operation of the device or the hydraulic system. For example, a permissible value range for the temperature is specified which corresponds to an expected or component-dependent permissible operating temperature range of the device, in particular from -30 °C to +140 °C. Further preferably, a resolution, for example 1 °C, and a distance between the temperature values ​​to be considered from one another, for example 10 °C, or a plurality of temperature values ​​to be considered are specified, and the method according to the invention is carried out for all corresponding temperature values ​​within this value range with the specified resolution.In particular, a permissible value range for the drive speed is selected depending on a technically possible value range for the corresponding pump. Alternatively, a permissible value range is selected for the total volume flows theoretically resulting from the permissible drive speeds, in particular from 0 l / min to 30 l / min. Further preferably, a resolution, for example 0.1 l / min, and a distance between the values ​​to be considered from one another, for example 0.5 l / min, or a plurality of values ​​to be considered are also specified here, and the method according to the invention is carried out for all values ​​within this value range. In particular, the method is carried out for all combinations of temperature values ​​and drive speed or total volume flow values ​​thus specified or possible.

[0010] According to a preferred development of the invention, the hydraulic pressure source comprises a second pump fluidically parallel to the first pump, and the total volume flow is determined as the sum of the respective products of volumetric efficiency, drive speed, and displacement of the respective pump. This provides a particularly simple method for determining the total volume flow when the hydraulic pressure source comprises more than one pump.

[0011] Particularly preferably, the first partial volume flow is determined as a function of a change in the reservoir's fill level. This provides a particularly simple method for determining the first partial volume flow. For example, the fill level is determined by a fill level sensor assigned to the reservoir.

[0012] According to a preferred embodiment of the invention, a temperature of the device is determined as a function of the second partial volume flow and an electrical or mechanical power output of the device. This provides a particularly advantageous and simple way to check whether, at the selected or given operating point consisting of total volume flow and temperature, the temperature of the device lies within a permissible operating temperature range, i.e., in particular, whether the device is sufficiently cooled.

[0013] The computer program product according to the invention for execution on a computer device having the features of claim 9 is characterized in that, when used as intended, it executes the method according to the invention. This results in the advantages already mentioned.

[0014] The computer device with the features of claim 10 is characterized in that it is specifically designed to carry out the method according to the invention or to execute the computer program product according to the invention. This also results in the advantages already mentioned above.

[0015] Further advantages and preferred features and combinations of features emerge in particular from the above description and from the claims. The invention will be explained in more detail below with reference to the drawings. Fig. 1 a circuit diagram of an advantageous hydraulic system, Fig. 2 a detailed view of the hydraulic system, and Fig. 3 an advantageous method for determining at least one volume flow in the hydraulic system.

[0016] The Fig. Figure 1 shows a circuit diagram of an advantageous hydraulic system 1 designed for use in a drive module of a motor vehicle. The hydraulic system 1 has a first clutch 2, a second clutch 3, and a third clutch 4.

[0017] The first clutch 2 and the second clutch 3 are assigned to a first drive machine (not shown), in particular an internal combustion engine, and the third clutch 4 is assigned to a second drive machine 28, in particular an electric machine, in order to selectively couple the second drive machine 28 to a transmission of the motor vehicle.

[0018] The hydraulic system 1 also has a common hydraulic circuit for cooling and / or lubricating at least the clutches 2, 3, 4 and the second drive motor 28. The hydraulic circuit includes a pump 5 for pumping a liquid medium. A further pump 6 is also provided, which is optional, however, and is intended in this case to supply other, not shown, components of the motor vehicle with fluid.

[0019] 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 capacity of the pumps 5, 6 and the respective cooling medium flow depend on the speed of the electric motor 7.

[0020] The two pumps 5, 6 are connected via a suction filter 8 to a tank or reservoir 9, which serves as a storage container or sump for the medium and in which the medium is preferably stored without pressure.

[0021] Furthermore, the hydraulic circuit has a controllable valve 10 interposed between the clutches 2, 3, 4 and the pump 5 for adjusting a cooling medium flow at least for the clutches 2, 3, 4 and the second drive machine.

[0022] The valve 10 is designed here as an electrically actuated 5 / 3-way valve with three outputs 11, 12, 13 and two inputs 14, 15. A first output 11 is assigned to the first clutch 2, a second output 12 to the second clutch 3, and a third output 13 to the third clutch 4. A first input 14 and a second input 15 are both assigned to the pump 5. According to an embodiment not shown, only one input is provided, which is assigned to the pump 5. The valve 10 is then designed as a 4 / 3-way valve.

[0023] The valve 10 thus has three possible switching positions 16, 17, 18. In a first switching position 16 of the valve 10, the medium flows from the second inlet 15 to the first outlet 11 through a second hydraulic line 19 only to the first clutch 2.

[0024] In a second switching position 17 of the valve 10, the medium flows from the first inlet 14 to the third outlet 13 through a first hydraulic line 20 only initially to the third clutch 4 and subsequently to the second drive motor 28. It is therefore provided that the medium flows through both the third clutch 4 and the second drive motor 28.

[0025] For this purpose, for example, guide plates and cross-sectional changes are provided to divide and guide the cooling medium flow. In particular, a portion of the cooling medium flow first flows through the third clutch 4 in certain areas, followed by the second drive motor 28.

[0026] In particular, a part of the cooling medium flow is diverted and supplied only to the second drive machine 28, so that medium is supplied to the third clutch 4 and the second drive machine 28 as required.

[0027] In a third switching position 18 of the valve 10, the medium flows from the second inlet 15 to the second outlet 12 through a third hydraulic line 21 only to the second clutch 3.

[0028] After the medium has flowed through the couplings 2, 3, 4 and the second drive machine 28, it is led back into the reservoir 9, as shown in the Fig. 1 indicated.

[0029] In the first hydraulic line 20, downstream, i.e., in the direction of the third clutch 4 and the second drive motor 28, there is first a pressure relief valve 22 and then an orifice 23 as a module 29. Finally, further downstream, a throttle 30 is arranged, formed by hydraulic lines leading to the clutch 4 and the second drive motor 28.

[0030] The pressure relief valve 22, the orifice 23, and the throttle 30 are components of an advantageous device 31 of the hydraulic system 1 and, as such, are designed to adjust the volume flow of the medium to the third clutch 4 depending on the temperature of the medium, as described above. The pressure relief valve 22, in turn, discharges excess medium into the reservoir 9 and, in this case, is designed as a seat valve.

[0031] The Fig. Figure 2 shows a detailed view of the module 29 in the second flow path 20, the flow direction of which is indicated by an arrow. The medium flows through an inlet opening 24 into a region 25. The pressure relief valve 22, designed as a seat valve, is located above the region 25.

[0032] A valve plate 26 of the pressure relief valve 22 seals off the area 25 as long as the force resulting from the pressure exerted by the medium on the valve plate 26 is smaller than the force exerted on the valve plate by the spring force of a spring element 27 arranged on the side of the valve plate 26 facing away from the area 25.

[0033] If the pressure exerted by the medium is greater than the pressure exerted by the spring element 27 according to the spring force, the valve disk is displaced so that excess medium flows through the opening thus created into the pressure relief valve 22, which in turn is fluidically connected to the reservoir 9, as described above, so that the medium flows back into the reservoir 9.

[0034] Further along the second flow path 20, the aperture 23 can be seen. In this case, it has a constant flow cross-section and serves as an outlet opening for the medium from region 25.

[0035] Downstream of the orifice 23, a tubular adapter element 32 is arranged as part of the throttle 30 in the first hydraulic line 20, wherein the adapter element 32 fluidically connects the device 31 to the hydraulic lines leading to the clutch 4 and the second drive machine 28.

[0036] The adapter element 32 has a first open end 33 assigned to the orifice plate 23 and a first cross-section, and a second open end 34 assigned to the hydraulic lines and having a second cross-section. In this case, the second cross-section is smaller than the first cross-section. The adapter element 32 has a continuously decreasing cross-section along its longitudinal extent, i.e., along the flow direction, and is thus conical in shape.

[0037] By appropriately selecting the second cross-section and the geometric design of the adapter element 32, on the one hand, an advantageously simple adaptation of the device 31 to hydraulic lines with corresponding cross-sections is ensured and, on the other hand, an advantageous additional possibility for influencing a throttle section and thus the properties of the throttle 30 is created. The throttle 30 can therefore be advantageously adapted to the cooling and / or lubrication requirements of the clutch 4 and the second drive motor 28.

[0038] Finally, the Fig.3 shows another advantageous method for determining at least one volume flow in the hydraulic system 1. The method begins with a step S1. In step S1, permissible value ranges for a temperature of the medium and for drive speeds of at least one of the pumps 5, 6, as well as corresponding value pairs, are specified. Method steps S2 to S5 are performed for a plurality of temperatures and drive speeds within the value ranges, as explained below.

[0039] In a step S2, the temperature of the medium in the reservoir 9 is first determined. Subsequently, the total volume flow delivered by the pump 5, 6 in the first hydraulic line 20 is determined as a function of the temperature. The total volume flow is determined as the product of a temperature-dependent volumetric efficiency, a drive speed, and a displacement of the pump 5, 6. If both pumps 5, 6 are considered, the total volume flow is determined as the sum of the respective products.

[0040] In a step S3, a first partial volume flow delivered into the reservoir 9 through the pressure relief valve 22 is determined. This is determined as a function of a change in the fill level of the reservoir 9, for example, using a corresponding sensor.

[0041] In step S4, a second partial volume flow through the orifice plate 23 and the throttle 30 to the device is determined as the difference between the total volume flow and the first partial volume flow. This is stored in a corresponding characteristic map in step S5.

[0042] Starting from step S4, in an optional step S7, a temperature of the device is determined as a function of the second partial volume flow and an electrical or mechanical power output of the device. This is stored in a corresponding characteristic map in step S8.

[0043] In a step S6 following steps S5 and S8, it is checked whether a second partial volume flow has been calculated for all specified value pairs for the temperature and the drive speeds within the permissible value ranges.

[0044] If this is not the case, the method returns 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. The first partial volume flow is determined empirically, using a system of equations, or using a neural network.

[0045] If it is determined in step S6 that the characteristic map or maps are complete, i.e. corresponding partial volume flows or temperatures have been entered for all value pairs, the method ends in step S9. LIST OF REFERENCE SYMBOLS: 1 hydraulic system 2 first clutch 3 second clutch 4 third clutch 5 Pump 6 additional pumps 7 Electric motor 8 suction filters 9 Reservoir 10 Valve 11 first exit 12 second exit 13 third exit 14 first entrance 15 second entrance 16 first switching position 17 second switching position 18 third switching position 19 second hydraulic line 20 first hydraulic line 21 third hydraulic line 22 Pressure relief valve 23 aperture 24 Inlet opening 25 Area 26 valve plates 27 Spring element 28 second drive engine 29 Module 30 Throttle 31 Device 32 adapter element 33 first end 34 second end

Claims

[1] A method for determining at least one volume flow in a device (31) for a hydraulic system (1), wherein the device has a first hydraulic line (20) which is connectable to a hydraulic pressure source for conveying a liquid medium on the one hand and to at least one device to be cooled and / or lubricated on the other hand, wherein the first hydraulic line (20) is assigned a pressure relief valve (22) which has a tank connection to a reservoir (9) for the liquid medium and connects the first hydraulic line (20) to the tank connection when a hydraulic pressure in the first hydraulic line (20) exceeds a predetermined limit value, wherein an orifice (23) is arranged in the first hydraulic line (20) downstream of the pressure relief valve (22), and wherein a throttle (30) is arranged or formed in the first hydraulic line (20) downstream of the orifice (23), comprising the 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 delivered into the reservoir (9) through the pressure relief valve (22), and - Determining a second partial volume flow through the orifice (23) and the throttle (30) to the device as a difference between the total volume flow and the first partial volume flow. [2] Method according to claim 1, characterized by that the difference for a variety of temperatures and total volume flows is determined empirically as a characteristic field, by a system of equations or by a neural network. [3] Method according to one of the preceding claims, characterized bythat the hydraulic pressure source has at least one pump (5, 6), and that the total volume flow is determined as the product of a temperature-dependent volumetric efficiency, a drive speed and a displacement of the pump (5, 6). [4] Method according to claims 2 and 3, characterized by that the multitude of total volume flows are determined by a multitude of drive speeds. [5] Method according to claim 4, characterized by that permissible value ranges are specified for the multitude of temperatures and / or drive speeds. [6] Method according to one of claims 3 to 5, characterized by that the hydraulic pressure source has a second pump (6) fluidically parallel to the first pump (5), and that the total volume flow is determined as the sum of the respective products of volumetric efficiency, drive speed and stroke volume of the respective pump (5,6). [7] Method according to one of the preceding claims, characterized by that the first partial volume flow is determined as a function of a change in the filling level of the reservoir (9). [8] Method according to one of the preceding claims, characterized by that a temperature of the device is determined as a function of the second partial volume flow and an electrical or mechanical power output of the device. [9] Computer program product for execution on a computer device, characterized by that the computer program product, when used as intended, carries out a method according to one of the preceding claims. [10] Computer equipment, characterized by that the computer device is specially adapted to execute the computer program product according to claim 9.

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