Method for operating a hydraulic system

Abstract

The present disclosure relates to a method for operating a hydraulic system (10) of a power-split transmission (106) of a working machine (100) with a switching device (14) for switching between different driving ranges. The hydraulic system (10) has a first pump device (20) for supplying a hydraulic fluid at a first lower pressure level in a first pressure section (32) for lubricating the power-split transmission (106). Additionally, the hydraulic system (10) has a second pump device (22) for supplying the hydraulic fluid at a second higher pressure level in a second pressure section (34) for actuating the switching device (14). The hydraulic system (10) further has a cooling device (30, 48) for cooling the hydraulic fluid. The method includes sensing (1) the temperature of the hydraulic fluid.The method further includes controlling (IV) the cooling device (30, 48) to cool the hydraulic fluid of the hydraulic system (10) based on the detected temperature.

Description

Technical area

[0001] The present disclosure relates to a method for operating a hydraulic system. Furthermore, the present disclosure relates to a control device configured to carry out such a method. Furthermore, the present disclosure relates to a power-split transmission having such a control device and to a work machine having such a power-split transmission. State of the art

[0002] In the field of work machinery, power-split transmissions are used that enable continuously variable gear ratio adjustment. Such transmissions can have a hydraulic circuit for lubricating transmission components and for actuating shifting elements of the transmission. DE 10 2020 213 596 A1 relates to a method for monitoring a system pressure in a hydraulic circuit of such a power-split continuously variable transmission. Description of the invention

[0003] The present disclosure relates to a method for operating a hydraulic system of a power-split transmission of a work machine having a shifting device for shifting between different driving ranges. The work machine may be, for example, a construction, agricultural, or forestry machine. For example, the work machine may be a tractor or a wheel loader. The work machine may have a drive device that may have an engine and the power-split transmission. The engine may be an internal combustion engine and, alternatively or additionally, an electric motor. The power-split transmission may be a hydrostatic-mechanical transmission and, alternatively or additionally, an electromechanical power-split transmission.The power-split transmission can have a mechanical power branch and a hydrostatic and, alternatively or additionally, an electrical power branch. The power-split transmission has a variator to enable continuously variable adjustment of the transmission gear ratio. For example, the power-split transmission can be designed such that different fixed gear ratios can be switched between an input and an output of the transmission via a mechanical power branch. The different gear ratios can be transmission ranges. The switching device can be used to switch between the different gear ratios. The switching device can be present as a switching group and have a plurality of switching elements, for example clutches, for switching the ranges.Within the driving range, the gear ratio can be continuously adjusted using the variator. The variator can be designed as a hydrostatic unit and comprise two hydraulic units that can be hydrodynamically connected to each other.

[0004] The hydraulic system can provide one or more functions using a hydraulic fluid. For example, the hydraulic system can provide hydraulic pressure for the hydrostatic drive of the power-split transmission and, alternatively or additionally, for working hydraulics of the work machine. The working hydraulics can operate a front loader of the work machine or another attachment. The hydraulic fluid can be provided by oil, water, and, alternatively or additionally, another fluid. The hydraulic system has a first pump device for providing a hydraulic fluid at a first, lower pressure level in a first pressure section for lubricating the power-split transmission. The hydraulic system further has a second pump device for providing the hydraulic fluid at a second, higher pressure level in a second pressure section for actuating the switching device.

[0005] The first and second pump devices can each be driven mechanically, electrically, magnetically, pneumatically, hydraulically, and alternatively or additionally by other means. The first and second pump devices can each have one or more pumps. The pumps can each be adjustable or non-adjustable. Adjustable can mean that a displacement of the pump can be changed. The output of the first and second pump devices can each be variably adjustable, i.e. a higher or lower pressure increase can be set by the first and second pump devices. A pump device can have both a non-adjustable and an adjustable pump, wherein the adjustable pump can be adjusted in order to set an overall output of the pump device.

[0006] The first and second pressure levels can each have a pressure level that can exist in the first and second pressure sections during normal operation of the hydraulic system. A pressure level can be a pressure range that exists during operation of the hydraulic system. This can be a target pressure, whereby the actually existing pressure can deviate slightly from this briefly and alternatively or additionally. The first pressure level can be, for example, between 2 and 10 bar, in one embodiment between 5 and 7 bar, for example essentially 6 bar. The second pressure level can be between 10 and 50 bar, for example between 20 and 30 bar, in one embodiment essentially 25 bar. These pressures can be understood either as absolute pressures or as a differential pressure to an ambient pressure.The first pump device can be configured to increase the pressure of the hydraulic fluid from an ambient pressure to the first pressure level. The second pump device can be configured to increase the pressure of the hydraulic fluid from the first pressure level to the second pressure level.

[0007] By lubricating the power-split transmission, wear, friction, energy loss, and alternatively or additionally, overheating of the transmission can be reduced or avoided. During lubrication, the transmission, a rear axle, the shifting mechanism, and alternatively or additionally a front axle can be lubricated. Lubrication can be designed so that a brief interruption in the pressure supply does not negatively affect it. When the shifting mechanism is actuated, one or more shifting elements of the shifting mechanism can be actuated, for example, closed or opened, by the hydraulic fluid. The actuation by the hydraulic fluid can occur counter to a preload force of the respective shifting element.

[0008] The hydraulic system has a cooling device for cooling the hydraulic fluid. The cooling device can have a heat exchanger, cooling fins, fans, heat pipes, and alternatively or additionally other coolants for cooling the hydraulic fluid. The cooling device can have a cooler valve, which can be configured to control a flow through the cooling device. For example, the cooler valve can be configured to cause the hydraulic fluid to flow through the cooling device when opened, thus cooling it. For this purpose, the cooling device can be connected in parallel to other sections of the hydraulic system. When the cooler valve is opened, a portion of the hydraulic fluid can thus be withdrawn from one of the pressure sections. This can cause a pressure drop in the pressure section due to the withdrawn hydraulic fluid.The cooler valve can be a proportional valve and, through an adjustable opening degree, provide an adjustable flow rate through the cooling device. The degree of cooling or cooling performance can be adjusted by adjusting the flow rate. The section where the cooling device is located can have a slightly lower pressure than other sections of the hydraulic system. This can promote the flow of oil through the cooling device.

[0009] The cooling device can be configured to direct the flowing hydraulic fluid into a hydraulic sump. This sump can represent a common, single sump for the entire hydraulic system. This allows cooling of all the hydraulic fluid used in the hydraulic system. The cooling device can be hydraulically connected to the first pressure section. Being hydraulically connected can mean that the hydraulic fluid can flow between the cooling device and the first pressure section.

[0010] The method comprises a first step of detecting a temperature of the hydraulic fluid. Detection can include measuring, determining, estimating, calculating, modeling, and alternatively or additionally predicting a temperature. Detection can be carried out using a temperature sensor, which can transmit the detected temperature to a control device. The method further comprises a step of controlling the cooling device to cool the hydraulic fluid of the hydraulic system based on the detected temperature. The cooling device can be controlled by the control device and, for example, lead to the cooling device being opened. The cooling device can be controlled to cause the hydraulic fluid to cool. The control can be proportional to the detected temperature.For example, a higher detected temperature can result in a request for more cooling capacity, while a lower temperature can result in a request for less cooling capacity. The cooling capacity can be adjusted proportionally, for example, by proportionally opening the radiator valve.

[0011] The described steps provide a method that enables effective and efficient cooling of the hydraulic fluid of the hydraulic system. Within the scope of the present method, overheating of the hydraulic system, the transmission, a working hydraulic system, and alternatively or additionally a lubrication system can be avoided on an as-needed basis. A hydraulic system of the present disclosure is therefore comparatively efficient, durable, fail-safe, and quiet.

[0012] In one embodiment, controlling the cooling device comprises withdrawing hydraulic fluid from one of the pressure sections. In one embodiment, the method additionally comprises controlling one of the pump devices to compensate for a pressure change in the pressure section caused by the withdrawn hydraulic fluid. These steps can be carried out by the control devices. The withdrawal can comprise withdrawal from the first and alternatively or additionally from the second pressure section. As described above, the withdrawal of the hydraulic fluid can lead to a pressure drop in the corresponding pressure section. By controlling the pump device, such a pressure drop can be compensated. For example, the pump device can be adjusted such that it leads to a pressure increase in the pressure section in order to compensate for the pressure drop.Conversely, the pumping device can also be adjusted or set to reduce the pressure. Compensation can be achieved by controlling the pumping device so that a constant or nearly constant pressure is maintained in the pressure section.

[0013] In one embodiment, the method comprises determining a pressure of the hydraulic fluid. The control of one of the pump devices can be based on the determined pressure. Determining the pressure can include measuring, detecting, estimating, calculating, modeling, and alternatively or additionally predicting the pressure. The determination can be carried out, for example, using a pressure sensor, which can determine the detected pressure in one of the pressure sections and transmit it to the control device. By controlling one of the pump devices to compensate for the pressure change, efficient cooling and, at the same time, constant operation of the hydraulic system can be provided. This prevents, for example, the particularly efficient cooling process from having a disruptive effect on the hydraulic system.

[0014] In one embodiment, the removal of hydraulic fluid comprises removing hydraulic fluid from the first pressure section. The removed hydraulic fluid can, for example, be removed from the first pressure section and supplied to the cooling device. From there, it can flow into the common sump after cooling. By removing the hydraulic fluid from the first pressure section, a particularly efficient cooling process can be provided.

[0015] In one embodiment, determining the pressure of the hydraulic fluid comprises determining the pressure in the first pressure section. Thus, the pressure of the hydraulic fluid can be determined hydraulically downstream of the first pump device. The determined pressure can thus correspond to or be particularly close to an inlet pressure of the lubrication system. This enables particularly precise control of the first pump device. Furthermore, particularly efficient operation of the hydraulic system can be provided, since the required pump output can be adjusted particularly precisely.

[0016] In one embodiment, detecting the temperature of the hydraulic fluid comprises detecting the temperature of the hydraulic fluid in the first pressure section. For example, the temperature of the hydraulic fluid can be detected hydraulically downstream of the first pump device. The detected temperature can thus, for example, correspond to or be particularly close to an inlet temperature of the lubrication system. This enables particularly precise control of the cooling device. Furthermore, particularly efficient and cost-effective operation of the hydraulic system can be provided, since the required cooling capacity can be adjusted particularly precisely.

[0017] In one embodiment, the method comprises comparing the detected temperature with a threshold value. The cooling device can be activated when the detected temperature is above the threshold value. The comparison can be performed by the control device. The threshold value can correspond to a temperature above which cooling by lubrication is no longer effective or becomes less effective. The threshold value can be 50°C, 70°C, 100°C, 150°C, 200°C, 300°C, or more. Alternatively or additionally, the threshold value can also correspond to a temperature gradient. The cooling device is then activated, for example, when the detected temperature increases with a greater dynamic than a limit value.By providing a process that activates a cooling device only when a threshold value is exceeded, particularly efficient, cost-effective, and alternatively or additionally quiet operation of the hydraulic system can be enabled. This allows the cooling device to be activated only when it is actually needed. For example, hydraulic energy can be saved when the machine is at a standstill or when the workload is only minimal.

[0018] Furthermore, the present disclosure relates to a control device for a hydraulic system of a power-split transmission of a work machine. The control device is configured, i.e., specifically prepared, for example, programmed, to carry out a method according to one of the previously described embodiments. The control device can have one or more interfaces for communicating with the respective components of the hydraulic system, each of which can be configured as an input and / or output interface. The control device can be a hydraulic control device that can be configured to control the hydraulic system of the power-split transmission of the work machine. The control device can have an interface for electronic connection to a transmission control of the work machine.The transmission control can be provided spatially and functionally separate from the hydraulic control.

[0019] Furthermore, the present invention relates to a power-split transmission for a work machine having a hydraulic system and a shifting device for shifting between different driving ranges. The hydraulic system has a first and a second pressure section. It further comprises a first pump device for providing a hydraulic fluid at a first, lower pressure level in the first pressure section for lubricating the power-split transmission. Furthermore, it has a second pump device for providing the hydraulic fluid at a second, higher pressure level in the second pressure section for actuating the shifting device. The hydraulic system also comprises a cooling device for cooling the hydraulic fluid and a control device according to one of the previously described embodiments. Furthermore, the present disclosure relates to a work machine having such a power-split transmission.With regard to the configurations and advantages of the individual components, reference is made to the above statements in connection with the method of the present invention. Short description of the characters Fig. 1 schematically shows a vehicle with a power-split transmission and a hydraulic system according to one embodiment. Fig. 2 shows the hydraulic system Fig. 1. Fig. 3 shows a flowchart of a method for controlling the hydraulic system of Fig. 2 according to one embodiment. Detailed description of the characters

[0020] Fig. 1 schematically shows a work machine 100 with a drive device 102 and a working hydraulic system 16 according to one embodiment. In the present embodiment, the work machine 100 is a tractor. The working hydraulic system 16 is designed in the present embodiment to drive a front loader of the tractor. The work machine 100 comprises a plurality of wheels (not shown) that can be driven via the drive device 102. The drive device 102 comprises an engine 104, which in the present embodiment is designed as an internal combustion engine. In addition, the drive device 102 comprises a power-split transmission 106 with a mechanical power path 108 and a hydraulic power path 110. The hydraulic power path 110 has a Fig. 2. The power-split transmission 106 has a drive 112 and an output 114. The drive 112 is mechanically connected to the engine 104. The output 114 of the power-split transmission 106 is mechanically connected to the wheels (not shown) of the work machine 100.

[0021] Via the mechanical power path 108 of the power-split transmission 106, which in the present embodiment has several shifting elements, different fixed gear ratios and thus different driving ranges can be switched between the input 112 and the output 114 of the transmission 106. Within these driving ranges, the gear ratio can be continuously adjusted via the hydrostatic unit 12. In the present embodiment, the hydrostatic unit 12 has two hydraulic machines that are hydraulically connected to one another. As shown in Fig. As shown in Figure 2, the hydrostatic unit 12 has a hydraulic input 60 and a hydraulic output 58 for supplying the hydraulic machines with hydraulic fluid. One of the hydraulic machines is designed as a machine with a constant displacement, and the other hydraulic machine is designed as a machine with a variable displacement. By adjusting the displacement, the ratio of the hydraulic power path 110 and thus also the ratio of the transmission 106 can be continuously adjusted.

[0022] The power-split transmission 106 has a hydraulic system 10, which is hydraulically connected to the hydrostat 12 of the hydraulic power path 110 and the working hydraulics 16. The structure of the hydraulic system 10 is shown in Fig. 2. The hydraulic system 10 is configured to provide lubrication for the power-split transmission 106 and for a rear axle (not shown) of the work machine 100. The hydraulic system 10 is additionally configured to supply hydraulic pressure to the hydrostatic drive 12, a shifting device 14 of the transmission 106, which shifting device includes the shifting elements of the mechanical power branch 108, and the working hydraulics 16 via the hydraulic fluid. The shifting device is embodied here as a shifting group 14. In the present embodiment, the hydraulic fluid is oil.

[0023] The hydraulic system 10 comprises a first pump device, a second pump device, and a working pump 24. The first pump device is provided here by a charge pump unit 20, and the second pump device is provided by a gear pump 22. The hydraulic system 10 has a common, single sump 18 for providing the oil at ambient pressure, which is pumped through the hydraulic system 10 by the charge pump unit 20 and the pumps 22, 24. The hydraulic system 10 has a first pressure section 32, which can be pressurized to a first pressure level by the charge pump unit 20. In the present embodiment, the first pressure level is between 2 and 10 bar, for example, 6 bar.The first pressure section 32 hydraulically connects the charge pump unit 20 and the hydraulic output 58 of the hydrostatic transmission 12 to the transmission pump 22, the working pump 24, a transmission lubrication section 26, a rear axle lubrication section 28, and a cooling device. The cooling device is provided here by a cooler 30 with a cooler valve 48. When the cooler valve 48 is open, oil flows through the cooler 30 to cool the oil. The first pressure section 32 has a lubrication pressure relief valve 36, which connects the first pressure section 32 to the sump 18. The lubrication pressure relief valve 36 is closed in the initial state. It is configured to open to relieve pressure when the pressure in the first pressure section 32 exceeds a threshold value.

[0024] The hydraulic system 10 further includes a second pressure section 34, in which the oil is pressurized at a second pressure level. In the present embodiment, the second pressure level is higher than the first pressure level and is between 20 and 30 bar, for example, 25 bar. The second pressure section 34 is hydraulically arranged downstream of the transmission pump 22 and hydraulically connects it to the hydraulic input 60 of the hydrostatic unit 12 and the shift group 14 for actuating the shift elements of the mechanical power path 108 of the transmission 106.

[0025] The second pressure section 34 has an accumulator 50, which is hydraulically arranged downstream of the transmission pump 22. This accumulator stores hydraulic energy, which can be released again, thus supporting a pressure as constant as possible in the second pressure section 34. The second pressure section 34 is connected to the first pressure section 32 via a transmission pressure relief valve 38. This valve is closed in the initial state and is configured to open to release pressure when the pressure in the second pressure section 34 exceeds a threshold value.

[0026] The hydraulic system 10 further includes a third pressure section 62, in which the oil is at a pressure at a third pressure level. The third pressure section 62 connects the working pump 24 to the working hydraulics 16.

[0027] The flow direction of the oil through the hydraulic system 10 is Fig. 2 by arrows. The oil is guided from the common sump 18 through the charge pump unit 20, the transmission pump 22, and the working pump 24 through the hydraulic system 10, before flowing back into the sump 18. The oil flows from the charge pump unit 20 to the transmission lubrication section 26, the rear axle lubrication section 28, the transmission pump 22, and the working pump 24. When the cooler valve 48 is open, oil flows from the hydraulic output 58 of the hydrostat 12 to the cooler 30. The section where the cooler 30 is located has a slightly lower pressure than the sections where the lubrication sections 26 and 28 are located. This prevents unwanted flow of hot oil from the hydrostat 12 into the lubrication sections 26, 28.

[0028] The charge pump unit 20 is configured to remove the oil from the sump 18 and convey it to the first pressure section 32. The charge pump unit 20 increases the pressure of the oil from the sump 18 from ambient pressure to the first pressure level. The oil flows through the first pressure section 32 for lubrication to the transmission lubrication section 26 and the rear axle lubrication section 28, which are indicated by two rectangles. The transmission lubrication section 26 is configured to provide lubrication for the power-split transmission 106. The rear axle lubrication section 28 is configured to provide lubrication for a rear axle (not shown) of the work machine 100. The lubrication sections 26, 28 are configured to return the oil to the common sump 18. The oil can be heated by the lubrication and, when flowing back into the sump 18, can have a higher temperature than before lubrication.

[0029] To cool the oil, the cooler 30 is connected to the first pressure section 32. The cooler valve 48, which is designed as a 2 / 2-way solenoid valve, is arranged hydraulically downstream of the cooler 30. The cooler valve is closed when de-energized and open when energized. In the open state, it hydraulically connects the outlet of the cooler 30 to the sump 18 and allows oil to flow through the cooler 30. In the closed state, no oil can flow through the cooler 30. The cooler valve 48 is designed as a proportional valve here. The flow through the cooler is proportional to the degree of opening of the cooler valve 48. Controlling the degree of opening enables control of the cooler 30.

[0030] The cooler 30 is connected in parallel to other elements of the hydraulic system 10. If the cooler valve 48 is opened and oil is drawn from the first pressure section 32, the pressure in the latter drops. Due to the parallel arrangement of the cooler 30, the flow can be controlled or deactivated as needed. Since the sump 18 is a common sump for the entire hydraulic system 10 shown, cooling of the oil returned to the sump 18 by the cooler 30 leads to cooling of the oil in the entire hydraulic system 10.

[0031] The transmission pump 22 is configured to extract a portion of the oil from the first pressure section 32, convey it to the second pressure section 34, and increase the pressure of the conveyed oil to the second pressure level. The oil flows through the second pressure section 34 to the hydrostatic unit 12 and to the shift group 14 in order to supply them with hydraulic pressure and drive them. The oil flows into the hydrostatic unit 12 via the hydraulic inlet 60 and flows out again into the first pressure section 32 via the hydraulic outlet 58. The shift group 14 is schematically represented only by a rectangle. It also has a hydraulic inlet at which the oil is present at the second pressure level. The shift group 14 has the above-described shift elements of the mechanical power branch 108 for shifting the different driving ranges of the power-split transmission 106.

[0032] The working pump 24 is configured to extract a portion of the oil from the first pressure section 32, transport it to the third pressure section 62, and increase the pressure of the transported oil to the third pressure level. The oil flows into the working hydraulics 16, which is also only schematically represented by a rectangle, in order to be able to move, for example, the tractor's front loader described above. The working hydraulics 16 is hydraulically connected to the sump 18 on the output side.

[0033] The charge pump unit 20 comprises a fixed charge pump 40 and a variable charge pump 42, as well as four filters 44 and a filter bypass 46. A filter 44 is arranged upstream and downstream of the fixed charge pump 40 and the variable charge pump 42, respectively, to filter the pumped oil. The hydraulic lines of the charge pump unit 20 converge after the outlet-side filters 44. The filter bypass 46 is hydraulically arranged between the pumps 40, 42 and the outlet-side filters 44. This allows the outlet-side filters 44 to be bypassed, for example, if they are clogged.

[0034] The hydraulic system 10 has a temperature sensor 52 and a pressure sensor 54, which are arranged along the hydraulic line leading to the transmission lubrication section 26. This forms part of the first pressure section 32. The hydraulic system 10 additionally has a control device 56. The temperature sensor 52 is configured to detect a temperature of the oil in the first pressure section 32 and transmit it to the control device 56. The pressure sensor 54 is configured to determine a pressure of the oil in the first pressure section 32 and transmit it to the control device 56. The control device 56 is connected to the cooler valve 48 and configured to open and close it. The control device 56 is connected to the charge pump unit 20 and configured to control it in order to set a pressure in the first pressure section and to compensate for a pressure drop therein.For this purpose, the control device 56 can, for example, adjust the adjustable charge pump 42 to control the pressure increase of the charge pump unit 20. The control device 56 is also connected to the hydrostat 12 and the switching group 14 for controlling the same. The connections of the control device 56 are shown by dashed lines.

[0035] Fig. 3 shows a flow chart of a method for operating the hydraulic system 10 from Fig. 2 according to one embodiment. The control device 56 of the hydraulic system 10 is configured to carry out the method described below. In a first step I of detecting, the temperature of the oil is detected by the temperature sensor 52 and transmitted to the control device 56. The temperature is detected or measured at the oil in the first pressure section 32. Thus, the temperature of the oil at the first pressure level is determined. Alternatively or additionally, it is also possible to determine the temperature of the oil in the sump 18. The temperature of the oil in the hydraulic system 10 depends on the oil sump temperature, i.e., the temperature of the oil in the sump 18. The temperature of the oil also depends on the operation of the power-split transmission 106 or the hydrostatic transmission 12. These can heat the oil through their operation and increase its temperature. The oil can also be heated by the lubrication in the lubrication sections 26, 28.

[0036] In a second step II of determining the oil pressure, the oil pressure is determined or measured by the pressure sensor 54 and transmitted to the control device 56. The oil pressure in the first pressure section 32 is determined. The oil pressure depends on the operation of the charge pump unit 20. As already explained, the pressure can fluctuate due to the activation of the cooler 30. The pressure is an inert element, meaning it reacts slowly to changes in the operation of the hydraulic system 10.

[0037] In a third step III of comparing the detected temperature with a threshold value, the temperature detected in step I is compared with a threshold value by the control device 56. In this process, it is determined whether the detected temperature is above this threshold value and thus whether cooling is necessary.

[0038] In a fourth step IV of controlling the cooling device, the cooler valve 48 is controlled by the control device 56 to cool the oil. This step is carried out if step III of the comparison has shown that the temperature detected in step I is above the threshold value. In the present hydraulic system 10, in this step, the cooler valve 48 is energized by the control device 56 to open it and allow oil to flow through the cooler 30 and into the sump 18. In the process, oil is taken from the first pressure section 32 and supplied to the cooler 30. This results in a pressure drop in the first pressure section 32. Step IV of the control is carried out by the control device 56 depending on the detected temperature. In this case, the cooler valve 48 is opened proportionally to the detected temperature in order to provide proportional cooling.

[0039] In a fifth step V of controlling one of the pump devices, the charge pump unit 20 is controlled by the control device 56 in order to compensate for a pressure change in the hydraulic system 10. In the case of the Fig. In the hydraulic system 10 shown in Figure 2, the adjustable charge pump 42 is controlled by the control device 56 to maintain a constant pressure in the first pressure section 32 despite the removal of oil during cooling in step IV. Control step V is performed as a function of the pressure determined in step II. In the embodiment shown, a control loop is closed by returning the determined pressure. Control step V thus comprises closed-loop control in the present embodiment. The greater the pressure drop due to the removed oil, the greater the pressure increase by the charge pump unit 20. Reference symbol 10 Hydraulic system 12 Hydrostat 14 switching group 16 Working hydraulics 18 Swamp 20 Charging pump unit 22 Gear pump 24 Working pump 26 Gearbox lubrication section 28 Rear axle lubrication section 30 coolers 32 first printing section 34 second printing section 36 Lubrication pressure relief valve 38 Transmission pressure relief valve 40 non-adjustable charging pump 42 adjustable charging pump 44 filters 46 Filter bypass 48 Radiator valve 50 accumulator 52 Temperature sensor 54 Pressure sensor 56 Control device 58 hydraulic output 60 hydraulic input 62 third printing section 100 work machines 102 Drive device 104 Engine 106 power-split transmission 108 mechanical power path 110 hydraulic power path 112 drive 114 downforce I Recording a temperature II Determining a pressure III Comparing a recorded temperature with a threshold value IV Control of the cooling system V Controlling one of the pump devices QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 213 596 A1

[0002]

Claims

[1] Method for operating a hydraulic system (10) of a power-split transmission (106) of a work machine (100) having a switching device (14) for switching different driving ranges, wherein the hydraulic system (10) has a first pump device (20) for providing a hydraulic fluid at a first lower pressure level in a first pressure section (32) for lubricating the power-split transmission (106), a second pump device (22) for providing the hydraulic fluid at a second higher pressure level in a second pressure section (34) for actuating the switching device (14), and a cooling device (30, 48) for cooling the hydraulic fluid, comprising detecting (I) a temperature of the hydraulic fluid, and controlling (IV) the cooling device (30, 48) for cooling the hydraulic fluid of the hydraulic system (10) based on the detected temperature. [2] Method according to claim 1, characterized byin that the actuation (IV) of the cooling device (30, 48) comprises withdrawing hydraulic fluid from one of the pressure sections (32; 34), and in that the method comprises actuation (V) of one of the pump devices (20; 22) to compensate for a pressure change caused by the withdrawn hydraulic fluid. [3] Method according to claim 2, characterized by in that the method comprises determining (II) a pressure of the hydraulic fluid, and in that the actuation (V) of one of the pump devices (20; 22) comprises actuation of one of the pump devices (20; 22) based on the determined pressure. [4] Method according to claim 2 or 3, characterized by that the removal of hydraulic fluid comprises a removal of hydraulic fluid from the first pressure section (32). [5] Method according to claim 4, characterized bythat determining (II) the pressure of the hydraulic fluid comprises determining (II) the pressure in the first pressure section (32). [6] Method according to one of the preceding claims, characterized by that detecting (I) the temperature of the hydraulic fluid comprises detecting (I) the temperature of the hydraulic fluid in the first pressure section (32). [7] Method according to one of the preceding claims, characterized by in that the method comprises comparing (III) the detected temperature with a threshold value, and in that the cooling device (30, 48) is controlled (IV) when the detected temperature is above the threshold value. [8] Control device (56) for a hydraulic system (10) of a power-split transmission (106) of a work machine (100), which is designed to carry out a method according to one of the preceding claims. [9] Power-split transmission (106) for a work machine (100) with a hydraulic system (10) and a switching device (14) for switching different driving ranges, wherein the hydraulic system (10) has a first and a second pressure section (32, 34), a first pump device (20) for providing a hydraulic fluid at a first lower pressure level in the first pressure section (32) for lubricating the power-split transmission (106), a second pump device (22) for providing the hydraulic fluid at a second higher pressure level in the second pressure section (34) for actuating the switching device (14), a cooling device (30, 48) for cooling the hydraulic fluid and a control device (56) according to claim 8. [10] Work machine (100) with a power-split transmission (106) according to claim 9.

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