Soil cultivation machine

Abstract

Soil cultivation machine, in particular soil compactor, comprising a hydraulic drive system (46), wherein the hydraulic drive system (46) comprises: - an electro-hydraulic pressure fluid source (48) with at least one electric motor (50) and at least one drive hydraulic pump (52), - a driving hydraulic circuit (54) supplied with pressure fluid by at least one driving hydraulic pump (52), - at least one drive hydraulic motor (56, 58) supplied with pressurized fluid from the drive hydraulic circuit (54), - a discharge valve arrangement (60) for discharging fluid from the driving hydraulic circuit (54) into a fluid reservoir (62), characterized in that a steering hydraulic circuit (34) is provided, and that the steering hydraulic circuit (34) is designed to replenish fluid in the driving hydraulic circuit (54).

Description

[0001] The present invention relates to a soil cultivation machine, such as a soil compactor, which can be used to compact the subgrade material, such as asphalt, soil or gravel.

[0002] An example of such a soil cultivation machine designed as a soil compactor is in Fig. Figure 1 shows this soil cultivation machine 10, designed as a soil compactor, which is constructed with a rear carriage 12 and a front carriage 14 pivotally connected to the rear carriage 12 about an approximately vertical steering axis. Drive wheels 16 are provided on the rear carriage 12, which can be driven to rotate the soil compactor 10 on the subsoil 18 to be compacted. A soil cultivation roller 20, designed as a compaction roller, is rotatably mounted on the front carriage 14. In the Fig. In the illustrated construction of a soil compactor, the soil cultivation roller 20 itself is generally not driven to rotate, but rolls over the ground 18, driven by the drive wheels 16. For example, in a soil compactor in which a compactor roller is also provided on the rear carriage 12, one or both compactor rollers could be driven to rotate in order to move the soil compactor over the ground 18.

[0003] The rear carriage 12 also includes an operator's platform 22, in which an operator can sit on an operator's seat 24 to operate the soil compactor. The operator's platform 22 also includes various operating devices, which will be explained below, by means of which an operator seated on the operator's seat 24 in the operator's platform 22 can operate the soil compactor.

[0004] In general, such soil compactors have a drive unit designed as a diesel internal combustion engine on the rear carriage 12. The drive unit powers one or more hydraulic pumps to supply pressurized fluid to various hydraulic circuits. For example, a travel hydraulic circuit may be provided, through which hydraulic motors assigned to the drive wheels 16 can be supplied with pressurized fluid to move the soil compactor over the ground 18. If such a soil compactor has one or more rotating compaction rollers or soil cultivation rollers 20, these may also be assigned hydraulic motors to drive their rotation. Another hydraulic circuit may be used to drive an unbalance system in the soil cultivation roller 20.Such an unbalance system, which may be designed to generate an oscillating and / or vibratory motion of the soil cultivation roller 20, may also include one or more hydraulic motors to drive the unbalanced masses into rotation. A further hydraulic circuit may be assigned to a steering system. The pressurized fluid present in such a steering hydraulic circuit can, via a hydraulic steering unit, direct hydraulic fluid to one or two steering piston / cylinder units 28, which act as steering elements 26, depending on a steering movement of a steering actuator, for example, a steering wheel. These steering piston / cylinder units 28 pivot the front carriage 14 and the rear carriage 12 relative to each other about the steering axis, thereby steering the soil compactor as it moves over the ground 18.

[0005] From DE 10 2017 215 726 A1, a soil cultivation machine according to the preamble of claim 1 is known, in which the discharge of fluid from a drive hydraulic circuit is enabled or prevented depending on the temperature of a hydraulic fluid in a drive hydraulic circuit. If the discharge of fluid is enabled due to a sufficiently high temperature of the hydraulic fluid, the amount of hydraulic fluid discharged is determined depending on the fluid pressure prevailing in the drive hydraulic circuit. The fluid discharged from the drive hydraulic circuit into a fluid reservoir is replaced by fluid taken from the fluid reservoir by means of a feed pump.

[0006] DE 10 2018 208 352 A1 discloses a hydraulic circuit in which, when the temperature of the hydraulic fluid is sufficiently high, fluid is fed to a tank depending on the fluid pressure. During the fluid feed-out, any dirt particles contained in the fluid are flushed into the tank. The fluid fed from the vehicle's hydraulic circuit into a fluid reservoir is replaced by fluid drawn from the fluid reservoir by means of a feed pump.

[0007] The object of the present invention is to provide a soil cultivation machine and a method for operating a soil cultivation machine, with which an efficient, energy-saving operation of a hydraulic drive system is achieved.

[0008] According to the invention, this problem is solved by a soil cultivation machine, in particular a soil compactor, comprising a hydraulic drive system, wherein the hydraulic drive system comprises: - an electro-hydraulic pressure fluid source with at least one electric motor and at least one drive hydraulic pump, - a driving hydraulic circuit supplied with pressure fluid by at least one driving hydraulic pump, - at least one hydraulic motor supplied with pressurized fluid from the drive hydraulic circuit, - a discharge valve arrangement for releasing fluid from the vehicle hydraulic circuit into a fluid reservoir.

[0009] To ensure that sufficient fluid is available in the driving hydraulic circuit even when or after fluid has been drained from it, a steering hydraulic circuit is provided, and the steering hydraulic circuit is designed to replenish fluid in the driving hydraulic circuit.

[0010] The hydraulic drive system can be configured to operate the discharge valve arrangement to deliver fluid to the fluid reservoir depending on at least one of the following parameters: - the temperature of the fluid in the vehicle's hydraulic circuit, - a temperature of the fluid in a fluid return to the fluid reservoir, - an ambient temperature, - the viscosity of the fluid in the vehicle's hydraulic circuit, - a degree of contamination of the fluid in the vehicle's hydraulic circuit - a time period since the last commissioning of the hydraulic drive system, - a time period since the last fluid withdrawal from the vehicle's hydraulic circuit.

[0011] By drawing fluid from the drive hydraulic circuit of the hydraulic drive system, it becomes possible to perform such a draw only when necessary or when it leads to an increase in the efficiency of the drive hydraulic circuit. This allows the energy introduced into the drive hydraulic circuit via the at least one electric motor of the electro-hydraulic pressure fluid source to be used efficiently.

[0012] In order to be able to operate at least one drive hydraulic motor in different directions of rotation in the drive hydraulic circuit, it is proposed thatthat the drive hydraulic circuit comprises a first connecting line between a first connecting port of the at least one drive hydraulic pump and a first connecting port of the at least one drive hydraulic motor for pumping pressure fluid from the first connecting port of the at least one drive hydraulic pump to the first connecting port of the at least one drive hydraulic motor for operating the at least one drive hydraulic motor in a first direction of rotation, and a second connecting line between a second connecting port of the at least one drive hydraulic pump and a second connecting port of the at least one drive hydraulic motor for pumping pressure fluid from the second connecting port of the at least one drive hydraulic pump to the second connecting port of the at least one drive hydraulic motor for operating the at least one drive hydraulic motor in a second direction of rotation.

[0013] If the fluid is drained during operation, it is particularly advantageous if the hydraulic drive system is designed to operate the drain valve assembly to drain fluid from the second connecting line when the at least one drive hydraulic motor is supplied with pressurized fluid via the first connecting line, and / or if the hydraulic drive system is designed to operate the drain valve assembly to drain fluid from the first connecting line when the at least one drive hydraulic motor is supplied with pressurized fluid via the second connecting line. This ensures that the fluid draining does not impair the supply of pressurized fluid to the at least one drive hydraulic motor.

[0014] The discharge valve arrangement can include a changeover valve with a first inlet port connected to the first connecting line, a second inlet port connected to the second connecting line, and an outlet port connected to the fluid reservoir. In a first valve position of the changeover valve, there is a connection between the first inlet port and the outlet port, and no connection between the second inlet port and the outlet port. In a second valve position of the changeover valve, there is a connection between the second inlet port and the outlet port, and no connection between the first inlet port and the outlet port. Thus, it is possible to discharge fluid from each of the connecting lines to the fluid reservoir.

[0015] In particular, if the switching valve is primarily intended to provide a connection between the fluid reservoir and one of the connecting lines, the output port of the switching valve can be connected to the fluid reservoir via a shut-off valve to define the amount of fluid discharged, wherein in an open position of the shut-off valve there is a connection between the output port and the fluid reservoir and in a closed position of the shut-off valve there is no connection between the output port and the fluid reservoir.

[0016] To adequately account for the temperature of the fluid, it is proposed that the hydraulic drive system be designed to operate the discharge valve arrangement for supplying fluid to the fluid reservoir depending on the temperature of the fluid in the first connecting line when the at least one drive hydraulic motor is supplied with pressurized fluid via the first connecting line, and to operate the discharge valve arrangement for supplying fluid to the fluid reservoir depending on the temperature of the fluid in the second connecting line when the at least one drive hydraulic motor is supplied with pressurized fluid via the second connecting line.

[0017] The hydraulic drive system can be configured to operate the discharge valve assembly to release fluid to the fluid reservoir when the temperature of the fluid in the drive hydraulic circuit is above a predetermined discharge fluid threshold temperature and / or within a predetermined discharge fluid temperature range. This ensures that the fluid is first brought to a suitable temperature and only then, when this is the case, is fluid discharged and replaced by other, generally colder, fluid, for example, from the fluid reservoir.

[0018] It can be provided that, when the discharge valve arrangement is operated to release fluid from the drive hydraulic circuit to the fluid reservoir, the quantity of fluid released to the fluid reservoir and / or the fluid discharge rate are adjusted depending on the ambient temperature, and / or the degree of contamination, and / or the time elapsed since the last commissioning of the hydraulic drive system, and / or the time elapsed since the last fluid discharge from the drive hydraulic circuit. This allows for even more precise consideration of the parameters influencing the operating state of the hydraulic drive system.

[0019] Furthermore, the hydraulic drive system can be configured to operate the discharge valve assembly to release fluid to the fluid reservoir when the fluid temperature in a leakage line leading to the fluid reservoir and / or in the area of ​​a fluid cooler leading to the fluid reservoir exceeds a predetermined discharge fluid threshold temperature and / or is within a predetermined discharge fluid temperature range. Such a leakage line, for example, which directs fluid leaks from one or more drive hydraulic motors into the fluid reservoir, or a fluid cooler through which fluid returned to the fluid reservoir flows, constitutes system sections of a fluid return. The fluid temperature present therein can also be used as an indicator for triggering a discharge process.

[0020] Alternatively or additionally to taking into account the temperature of the fluid in the drive hydraulic circuit, the hydraulic drive system can be configured to operate the discharge valve arrangement to release fluid to the fluid reservoir when the ambient temperature is above a predetermined discharge ambient threshold temperature and / or within a predetermined discharge ambient temperature range. A low ambient temperature generally means that the fluid in the drive hydraulic circuit also has a low temperature or cools down more quickly, so that even by taking the ambient temperature into account, discharge that would lead to lower efficiency can be avoided.

[0021] Furthermore, the hydraulic drive system can be configured to operate the discharge valve arrangement to supply fluid to the fluid reservoir when the viscosity of the fluid in the drive hydraulic circuit is below a predetermined threshold viscosity and / or within a predetermined viscosity range. The viscosity of the fluid in the drive hydraulic circuit can be determined, for example, by measuring the pressure drop between two pressure sensors in the drive hydraulic circuit and represents a parameter directly related to the fluid's temperature. Taking the fluid's viscosity into account, it can also be ensured that no fluid is discharged, or, for example, that only a smaller quantity of fluid is discharged, as long as the viscosity is too high, i.e., the fluid is comparatively viscous.Only when the viscosity has decreased after sufficient operating time, is fluid discharged according to this aspect of the present invention in order to maintain the viscosity in a range that is optimal for efficient energy use.

[0022] According to a further design aspect, the hydraulic drive system can be configured to operate the discharge valve arrangement to supply fluid to the fluid reservoir when the degree of contamination of the fluid in the drive hydraulic circuit exceeds a predetermined discharge threshold contamination level and / or is within a predetermined contamination level range. The degree of contamination of the fluid can be detected, for example, by optical detectors using transmission or absorption technology. If it is detected that the fluid circulating in the drive hydraulic circuit contains an excessively high proportion of contaminant particles, a portion of this fluid can be discharged and, for example, passed through a particle filter on its way to the fluid reservoir for cleaning.Alternatively or additionally, fluid newly fed into the vehicle hydraulic circuit can be subjected to filtration when draining from the fluid reservoir.

[0023] According to a further aspect of the invention, the hydraulic drive system can be configured to operate the discharge valve arrangement to discharge fluid to the fluid reservoir when a predetermined time has passed since the last commissioning of the hydraulic drive system, and / or when a predetermined time has passed since the last fluid discharge from the drive hydraulic circuit.

[0024] The present invention is described in detail below with reference to the accompanying figures. These show: Fig. 1 a side view of a soil cultivation machine designed as a soil compactor; Fig. 2 In principle, a hydraulic steering system and a hydraulic drive system of a soil cultivation machine.

[0025] Before proceeding with reference to the Fig. 2. Where the structure and function of a hydraulic steering system and a hydraulic drive system of a soil cultivation machine are explained in detail, it should be noted that the following refers to the Fig. The systems described in section 2 can be used, for example, in a soil cultivation machine 10 designed as a soil compactor, as described in Fig. 1 is shown. However, it should be noted that the following refers to the Fig. The systems described in section 2 can also be used with differently designed soil cultivation machines, for example, soil cultivation machines that have soil cultivation rollers on a front carriage and a rear carriage.

[0026] The Fig. Figure 2 shows a hydraulic steering system, generally designated 30. The hydraulic steering system 30 comprises one or more steering elements 26 designed as double-acting steering piston / cylinder units 28, which are coupled to a steering pressure fluid circuit 34 via a hydraulic steering unit 32. The hydraulic steering system 30 includes an electro-hydraulic pressure fluid source 36 with an electric motor 38 and a steering pressure fluid pump 40 driven by the electric motor 38. The electric motor 38 of the hydraulic steering system 30 is controlled by a control unit 42 and is supplied with power from a voltage source, for example, a battery 44, to drive the steering pressure fluid pump 40. The application of an electrical voltage to the electric motor 38 from the battery 44 can be carried out according to corresponding control commands from the control unit 42.

[0027] The Fig. Figure 2 further shows a hydraulic drive system, generally designated 46. The hydraulic drive system 46 comprises a hydraulic pressure fluid source 48 with an electric motor 50 and a drive hydraulic pump 52 driven by the electric motor 50. The drive hydraulic pump 52 pumps a fluid, for example hydraulic oil, in a drive hydraulic circuit 54 and thus supplies two drive hydraulic motors 56, 58 integrated into the drive hydraulic circuit 54 with pressure fluid. For example, the two drive hydraulic motors 56, 58 can be assigned to two soil cultivation rollers provided on a soil compactor in order to drive each of these soil cultivation rollers to move the soil compactor. In the case of the Fig. In the illustrated structure of a soil cultivation machine, one of the two drive hydraulic motors 56, 58 could be assigned to one of the two drive wheels 16, and the other of the two drive hydraulic motors 56, 58 could be assigned to the other drive wheel 16.

[0028] The driving hydraulic circuit 46 further comprises a discharge valve arrangement 60, through which fluid from the driving hydraulic circuit 46 can be discharged to a fluid reservoir 62. From this fluid reservoir 62, the steering hydraulic pump 40 delivers fluid into the steering hydraulic circuit 34, which, as in Fig. Figure 2 shows that the driving hydraulic circuit 54 is linked in such a way that fluid, for example hydraulic oil, supplied as pressure fluid by the steering hydraulic pump 40 into the steering hydraulic circuit 34 can be introduced into the driving hydraulic circuit 46. This makes it possible, for example, to keep the amount of fluid present in the driving hydraulic circuit 54 essentially constant by replenishing it with fluid from the steering hydraulic circuit 34 when fluid is discharged from the driving hydraulic circuit 46 into the fluid reservoir 62 via the discharge valve arrangement 60. Fluid leaks occurring in the driving hydraulic circuit 54 can also be compensated for in this way.

[0029] The steering hydraulic circuit 34 further comprises a return valve 64, through which fluid or pressure fluid can be fed back from the steering hydraulic circuit 34 into the fluid reservoir 62. The return valve 64 can, for example, be pressure-controlled, so that when the fluid pressure in the steering hydraulic circuit 34 or also in the driving hydraulic circuit 54 exceeds a predetermined threshold pressure, fluid can be discharged to the fluid reservoir 62.

[0030] To use a soil cultivation machine, for example the one in Fig. To steer the soil cultivation machine 10 shown in Figure 1, a steering actuation device 66, generally designed as a steering wheel, is provided. An operator seated in the operator's station 22 can steer the soil cultivation machine 10, which is moving over the soil to be cultivated 18, by actuating the steering actuation device 66, i.e., by turning a steering wheel. The steering movement of the steering actuation device 66 is thereby converted in the hydraulic steering unit 32 into a corresponding supply of pressurized fluid into one chamber of each steering piston / cylinder unit 28 and a corresponding discharge of pressurized fluid from the other of the two chambers of each steering piston / cylinder unit 28.

[0031] The actuation of the steering actuator 66 is detected by a steering sensor 68. This sensor can, for example, detect the rotational movement of a steering shaft coupled to the steering actuator 66 for common rotation and output a signal to the control unit 42 containing information representing the steering state. This information can, for example, be information about the current rotational position of the steering actuator 66 or the steering shaft coupled to it, which represents a steering angle.

[0032] The operator station 22 is equipped with additional controls by which an operator can operate such a soil cultivation machine 10. The operator can set the soil cultivation machine 10 in motion by means of a drive control lever 70, for example. This means that, for example, by pivoting the drive control lever 70, the electric motor 50 of the electro-hydraulic pressure fluid source 48 of the hydraulic drive system 46 is operated at a speed corresponding to the driving operating state specified by the operator. For example, the operator can move the drive control lever 70 to a park position. When the drive control lever 70 is in the park position, the soil cultivation machine 10 is generally stationary, and a parking brake can be activated, for example, to prevent it from rolling away.By pivoting from the parked position to a travel preparation position, a travel preparation state is entered. In the travel preparation state, the travel hydraulic motors 56, 58 remain inactive; that is, for example, the electric motor 50 is kept out of operation as in the parked position, but the parking brake is released. When pivoting from the travel preparation position corresponding to the travel preparation state to a travel position corresponding to a driving state, a voltage corresponding to the respective pivot position is applied to the electric motor 50, so that it drives the travel hydraulic pump 52 in a direction of rotation corresponding to the respective direction of travel, and the two travel hydraulic motors 56, 58 are supplied with pressurized fluid, thereby moving the tillage machine 10 over the ground 18.

[0033] The operator seat 24 can be equipped with a seat occupancy sensor 74, which provides information on whether an operator is seated in the operator seat 24 or not. This information, as well as information on the respective operating position or operating state of the drive control element 72, can be fed into the control unit 42 in order to operate the electric motor 38 of the electro-hydraulic pressure fluid source 36 taking this information into account.

[0034] Taking into account the information representing the seat occupancy or the operating state of the driving control element 72, the control unit 42 can, for example, control the electric motor 38 such that when the driving control element 72 is in the park position, the electric motor 38 is deactivated or kept in a deactivated state, meaning that no voltage is applied to it. Alternatively or additionally, this can also occur if the information supplied by the seat occupancy sensor 74 indicates that no operator is seated in the operator seat 24.

[0035] If the driving control element 72 is in the driving preparation position corresponding to the driving preparation state, which is generally the case when an operator is seated on the operator seat 24 and acting on the driving control element 72, the control unit 42 can operate the electric motor 38 of the electro-hydraulic pressure fluid source 36 such that it rotates at a basic speed. This results in pressure being built up in the steering hydraulic circuit 34.

[0036] When the driving control element 72 is moved into the driving position corresponding to the driving condition, the control unit 42 can adjust the voltage applied to the electric motor 38 of the electro-hydraulic pressure fluid source 36 so that the electric motor 38 operates at a speed higher than its base speed, where the operating speed can, for example, be fixed. Taking into account the steering information, i.e., information about the steering angle to be provided according to an actuation of the steering control element 66 or a steering angle change rate, the control unit 42 can adjust the operating speed of the electric motor 38 of the electro-hydraulic pressure fluid source 36.

[0037] The drive hydraulic circuit 54 comprises a first connecting line 76, which establishes a connection between a first connecting port 78 of the drive hydraulic pump 52 and a respective first connecting port 80, 82 of the two drive hydraulic motors 56, 58. Furthermore, the drive hydraulic circuit 54 comprises a second connecting line 84, which establishes a connection between a second connecting port 86 of the drive hydraulic pump 52 and a respective second connecting port 88, 90 of the two drive hydraulic motors 56, 58.

[0038] Depending on the direction of rotation in which the drive hydraulic pump 52 is driven by the electric motor 50 of the electro-hydraulic pressure fluid source 48, the fluid present in the drive hydraulic circuit 54 is conveyed as pressure fluid via the first connecting line 76 or the second connecting line 84 to the two drive hydraulic motors 56, 58. Depending on which of the two connecting lines 76, 84 supplies the drive hydraulic motors 56, 58 with pressure fluid, they rotate in one of two possible directions, thus enabling the tillage machine to be moved in different directions, i.e., forwards or backwards.

[0039] The discharge valve arrangement 60 comprises a changeover valve 92 designed as a directional control valve, which is controlled by a control unit 94 that also controls, for example, the electric motor 50. The changeover valve 92 has a first inlet port 96, which is connected to the first connecting line 76, and a second inlet port 98, which is connected to the second connecting line 84. The changeover valve 92 further comprises an outlet port 100, which is connected to the fluid reservoir 62 via a shut-off valve 102, designed, for example, as a proportional valve and also controlled by the control unit 94.

[0040] In the discharge valve arrangement 60, the changeover valve 92 serves to establish a connection between one of the two connecting lines 76, 84 and the fluid reservoir 62. The changeover valve 92 can also be set to a neutral position, in which the connection between each of the two connecting lines 76, 84 and the fluid reservoir 62 is always interrupted, regardless of the position of the shut-off valve 102. The shut-off valve 102, in turn, has the function of establishing or interrupting the connection to the fluid reservoir 62 by switching between an open position and a closed position whenever one of the two connecting lines 76, 84 or the associated first or second inlet port 96, 98 is connected to the outlet port 100 via the changeover valve 92, in order to discharge fluid from one of the two connecting lines 76, 84 to the reservoir 62 and, in particular, to control the discharge quantity.to adjust the withdrawal rate.

[0041] In the illustrated embodiment, two temperature sensors 104 and 106 are also provided in connection with the drive hydraulic circuit 54. Temperature sensor 104 is positioned such that it detects the temperature of the fluid in the drive hydraulic circuit 54 in a section of the first connecting line 76 shortly before or near the first connection ports 80 and 82 of the drive hydraulic motors 56 and 58, and transmits this information to the control unit 94. Temperature sensor 106 is positioned such that it detects the temperature of the fluid in the drive hydraulic circuit 54 in the second connecting line 84 shortly before or near the second connection ports 88 and 90 of the drive hydraulic motors 56 and 58. The temperature information supplied by temperature sensor 106 is also transmitted to the control unit 94.

[0042] Taking into account the temperature information provided by the temperature sensors 104, 106, the control unit 94 controls the discharge valve arrangement 60 in the manner described below, such that fluid is discharged from the drive hydraulic circuit 54 to the reservoir 62 at a suitable time and in a suitable quantity. In order to keep the quantity of fluid present or circulating in the drive hydraulic circuit 54 essentially constant, the electro-hydraulic pressure fluid source 36 of the hydraulic steering system 30 can be operated simultaneously in such a way that sufficient fluid is supplied to the drive hydraulic circuit 54 via the steering hydraulic circuit 34.

[0043] For example, assume that the electric motor 50 of the electro-hydraulic pressure fluid source 48 of the hydraulic drive system 46 is operated in such a way that the drive hydraulic pump 52 supplies pressure fluid via the first connecting line 76 to the two drive hydraulic motors 56, 58, thus rotating them in a first direction, for example to move the tillage machine 10 forward. In this state, with the shut-off valve 102 still held in its closed position, for example, the changeover valve 92 can be switched to a valve position in which the second inlet port 96, and thus the second connecting line 84, is connected to the outlet port 100.If the signal provided by the temperature sensor 104 indicates a fluid temperature below a predetermined discharge fluid threshold temperature of, for example, about 50°C, or not within a predetermined discharge fluid temperature range, in an area shortly upstream of the drive hydraulic motors 56, 58 to be supplied, the shut-off valve 102 remains in its closed position, so that no fluid is discharged from the drive hydraulic circuit 54.

[0044] If the temperature of the fluid in the drive hydraulic circuit 54 in the area just upstream of the drive hydraulic motors 56, 58 exceeds the discharge fluid threshold temperature, or if the discharge fluid temperature range is reached, the shut-off valve 102 is controlled by the control unit 94 such that fluid is discharged from the drive hydraulic circuit 54 into the fluid reservoir 62. For example, for each discharge process, it can be provided that a defined quantity of fluid, determined by appropriate control of the shut-off valve 102, is discharged at a defined rate to ensure that sufficient fluid can be replenished via the steering hydraulic circuit 34.

[0045] If the drive hydraulic pump 52 is operated in such a way that pressure fluid is supplied to the two drive hydraulic motors 56, 58 via the second connecting line 84, the changeover valve 92 can be moved to a valve position in which a connection is established between the first inlet port 96 and the outlet port 100, and thus a connection is established between the first connecting line 76 and the outlet port 100. If the temperature signal supplied by the temperature sensor 106 shortly before the area where the pressure fluid is supplied to the two drive hydraulic motors 56, 58 indicates that the fluid temperature in this area is above the discharge fluid threshold temperature, orWhen the discharge fluid temperature is within the discharge fluid temperature range, the control unit 94 controls the shut-off valve 102 in such a way that fluid with a predetermined quantity and / or a predetermined discharge rate is discharged from the first connecting line 76 towards the fluid reservoir 62.

[0046] By only drawing fluid from the drive hydraulic circuit 54 when it has reached a sufficiently high temperature, it is ensured that, for example, when starting up the hydraulic drive system 46 or the tillage machine 10, initial fluid withdrawal is suppressed, allowing the fluid to quickly reach a suitable operating temperature, for example, in the range of approximately 40°C to 65°C. By suppressing fluid withdrawal when the fluid temperature is not yet sufficiently high, the time required to reach a sufficient temperature is kept as short as possible, thus enabling the system to reach an operating state as quickly as possible in which a high efficiency is achieved in the hydraulic drive system 46 due to the sufficiently low viscosity of the fluid.Only when this is ensured will fluid be repeatedly drawn off in successive discharge cycles to maintain the temperature of the fluid in the drive hydraulic circuit 54 within an optimal range. Alternatively, in such an operating condition, fluid could also be continuously drawn off at a comparatively low rate and replenished from the fluid reservoir 62 via the steering hydraulic circuit 34.

[0047] Furthermore, in the procedure described above, fluid from the drive hydraulic circuit 54 is drawn from the section that is not used to supply pressure fluid to the drive hydraulic motors 56, 58. This prevents a pressure drop on the pressure side of the drive hydraulic motors 56, 58, i.e., in the section of the connecting line 76, 84 used to supply pressure fluid to the drive hydraulic motors 56, 58, due to the fluid being drawn from the circuit.

[0048] Taking into account the fluid temperature in the drive hydraulic circuit 54 in a section shortly upstream of the pressurized drive hydraulic motors 56, 58 ensures that a fluid temperature is considered that approximately corresponds to an average temperature. Generally, the fluid will have the lowest temperature in the fluid reservoir 62 and the highest temperature in a section shortly downstream of the pressurized drive hydraulic motors 56, 58. However, it should be noted that the fluid temperature in other sections of the drive hydraulic circuit 54 or the hydraulic drive system 46 can also be taken into account.

[0049] In Fig. Figure 2 represents system sections of a fluid return system through which fluid is fed back into the fluid reservoir 62. A leakage line 108 and a fluid cooler 110 are also shown. For example, fluid leakage occurring in the drive hydraulic motors 56, 58 can be fed back into the fluid reservoir 62 via the leakage line 108. Fluid returned to the fluid reservoir from various system sections can be passed through the fluid cooler 110, or possibly several, to dissipate heat. The temperature of the fluid can also be measured in the area of ​​such a fluid return system, i.e., for example, in the area of ​​the leakage line 108 and / or in the area of ​​the fluid cooler 110, and used as a basis for triggering a discharge process.

[0050] The principles of the present invention, in which fluid is drained from the drive hydraulic circuit 54 when the efficiency of the hydraulic drive 46 is not impaired or can be increased, can also be applied if, alternatively or additionally to considering the temperature of the fluid in the drive hydraulic circuit 54, other parameters are taken into account. For example, the ambient temperature in the area of ​​the tillage machine 10 can be taken into account in the same way, since a low ambient temperature generally also results in the fluid in the drive hydraulic circuit 54 having a comparatively low temperature. In connection with the ambient temperature, a drain-ambient threshold temperature or a drain-ambient temperature range can therefore be defined, the exceeding or reaching of which triggers a drain process.The viscosity of the fluid in the drive hydraulic circuit 54, which is directly related to the fluid temperature, can also be considered as a parameter when allowing or suppressing a fluid drain, as can the degree of contamination of the fluid in the drive hydraulic circuit 54. The time elapsed since the commissioning of the hydraulic drive system 46 can also be considered as a further parameter. If a predetermined operating time is reached, it can be assumed that the fluid in the drive hydraulic circuit 54 has reached a sufficiently high temperature so that draining the fluid does not impair the efficiency of the drive hydraulic circuit. The time elapsed since the last drain can also be used as a criterion for performing another drain.

[0051] Furthermore, it is possible to link several such parameters by using one or more of them as a criterion for triggering a draining process, while one or more other parameters are used to determine the quantity or rate at which fluid is drained. For example, the temperature of the fluid in the vehicle hydraulic circuit 54 can be used as a criterion for triggering a draining process in the manner described above, while the ambient temperature can be used as a criterion for the quantity of fluid to be drained and / or the draining rate, for example, such that the quantity of fluid drained and / or the draining rate also increases with increasing ambient temperature.

[0052] Finally, it should be noted that such a soil cultivation machine can, of course, be varied in many different aspects. For example, in the hydraulic steering system, the electro-hydraulic pressure fluid source can comprise several steering pressure fluid pumps, which can be operated by a common or, if necessary, separate electric motors. Similarly, the hydraulic drive system can incorporate several drive hydraulic pumps, which can be driven by a common or, if necessary, separate electric motors. As already explained, a soil cultivation machine designed, for example, as a soil compactor, can, of course, be configured differently with regard to the use of soil cultivation rollers or drive wheels than described above. Fig.Figure 1. Furthermore, in addition to the parameters mentioned above, other influencing factors relevant to the operation of the hydraulic drive system can be taken into account for the withdrawal of fluid from the drive hydraulic circuit or the suppression of a withdrawal. 10 soil cultivation machines 12 rear cars 14 Front section 16 drive wheel 18 Underground 20 soil cultivation roller 22 Control station 24 operator seats 26 Steering mechanism 28 piston / cylinder unit 30 Steering system 32 Hydraulic steering unit 34 Steering pressure fluid circuit 36 Pressure fluid source 38 Electric motor 40 Pressure fluid pump 42 Control unit 44 Battery 46 hydraulic drive system 48 Pressure fluid source 50 electric motor 52 Driving hydraulic pump 54 Driving hydraulic circuit 56 Hydraulic motor 58 Hydraulic motor 60 Discharge valve arrangement 62 Fluid reservoir 64 Return valve 66 Steering actuation device 68 Steering sensor 70 Driving control levers 72 Driving control device 74 Seat occupancy sensor 76 Connecting line 78 first connection point 80 first connection 82 first connection 84 Connecting line 86 second connection port 88 second connection port 90 second connection port 92 Diverter valve 94 Control unit 96 first input connection 98 second input port 100 output ports 102 Shut-off valve 104 Temperature sensor, 106 Temperature sensor 108 Leakage line 110 Fluid Coolers

Claims

[1] Soil cultivation machine, in particular soil compactor, comprising a hydraulic drive system (46), wherein the hydraulic drive system (46) comprises: - an electro-hydraulic pressure fluid source (48) with at least one electric motor (50) and at least one drive hydraulic pump (52), - a driving hydraulic circuit (54) supplied with pressure fluid by at least one driving hydraulic pump (52), - at least one drive hydraulic motor (56, 58) supplied with pressurized fluid from the drive hydraulic circuit (54), - a discharge valve arrangement (60) for discharging fluid from the driving hydraulic circuit (54) into a fluid reservoir (62), characterized by , that a steering hydraulic circuit (34) is provided, and that the steering hydraulic circuit (34) is designed to replenish fluid in the driving hydraulic circuit (54). [2] Soil cultivation machine according to claim 1, characterized by, that the hydraulic drive system (46) is designed to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) depending on at least one of the following parameters: - a temperature of the fluid in the drive hydraulic circuit (54), - a temperature of the fluid in a fluid return to the fluid reservoir (62), - an ambient temperature, - a viscosity of the fluid in the vehicle hydraulic circuit (54), - a degree of contamination of the fluid in the vehicle hydraulic circuit (54), - a time period since the last commissioning of the hydraulic drive system (46), - a time period since the last fluid discharge from the drive hydraulic circuit (54). [3] Soil cultivation machine according to claim 1 or 2, characterized by, that the drive hydraulic circuit (54) has a first connecting line (76) between a first connecting port (78) of the at least one drive hydraulic pump (52) and a first connecting port (80, 82) of the at least one drive hydraulic motor (56, 58) for pumping pressure fluid from the first connecting port (78) of the at least one drive hydraulic pump (52) to the first connecting port (80, 82) of the at least one drive hydraulic motor (56, 58) for operating the at least one drive hydraulic motor (56, 58) in a first direction of rotation, and a second connecting line (84) between a second connecting port (86) of the at least one drive hydraulic pump (52) and a second connecting port (88, 90) of the at least one drive hydraulic motor (56, 58) for pumping pressure fluid from the second connecting port (86) of the at least one drive hydraulic pump (52) to the second connection port (88,90) of the at least one drive hydraulic motor (56, 58) for operating the at least one drive hydraulic motor (56, 58) in a second direction of rotation. [4] Soil cultivation machine according to claim 3, characterized by , that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid from the second connecting line (84) when the at least one drive hydraulic motor (56, 58) is supplied with pressurized fluid via the first connecting line (76), or / and that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid from the first connecting line (76) when the at least one drive hydraulic motor (56, 58) is supplied with pressurized fluid via the second connecting line (84). [5] Soil cultivation machine according to claim 3 or 4, characterized by, that the discharge valve arrangement (60) comprises a changeover valve (92) with a first inlet port (96) connected to the first connecting line (76), a second inlet port (98) connected to the second connecting line (84) and an outlet port (100) connected to the fluid reservoir (62), wherein in a first valve position of the changeover valve (92) there is a connection between the first inlet port (96) and the outlet port (100) and there is no connection between the second inlet port (98) and the outlet port (100) and in a second valve position of the changeover valve (92) there is a connection between the second inlet port (98) and the outlet port (100) and there is no connection between the first inlet port (96) and the outlet port (100). [6] Soil cultivation machine according to claim 5, characterized by, that the outlet port (100) of the changeover valve (92) is connected to the fluid reservoir (62) via a shut-off valve (102), wherein in an open position of the shut-off valve (102) there is a connection between the outlet port (100) and the fluid reservoir (62) and in a closed position of the shut-off valve (102) there is no connection between the outlet port (100) and the fluid reservoir (62). [7] Soil cultivation machine according to claim 2 or one of claims 3-6, insofar as it refers back to claim 2, characterized by, that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) depending on the temperature of the fluid in the first connecting line (76) when the at least one drive hydraulic motor (56, 58) is supplied with pressurized fluid via the first connecting line (76), and to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) depending on the temperature of the fluid in the second connecting line (84) when the at least one drive hydraulic motor (56, 58) is supplied with pressurized fluid via the second connecting line (84). [8] Soil cultivation machine according to claim 2 or one of claims 3-7, insofar as it refers back to claim 2, characterized by, that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when the temperature of the fluid in the drive hydraulic circuit (54) is above a predetermined discharge fluid threshold temperature and / or within a predetermined discharge fluid temperature range. [9] Soil cultivation machine according to claim 8, characterized by , that when the discharge valve arrangement (60) is operated to discharge fluid from the drive hydraulic circuit (54) to the fluid reservoir (62), the quantity of fluid discharged to the fluid reservoir (62) and / or the fluid discharge rate is adjusted depending on the ambient temperature and / or the degree of contamination and / or the time elapsed since the last commissioning of the hydraulic drive system (46) and / or the time elapsed since the last fluid discharge from the drive hydraulic circuit (54). [10] Soil cultivation machine according to one of claims 1-9, characterized by , that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when the temperature of the fluid in a leakage line (108) leading to the fluid reservoir (62) and / or in the area of ​​a fluid cooler (110) leading to the fluid reservoir (62) is above a predetermined discharge fluid threshold temperature and / or within a predetermined discharge fluid temperature range. [11] Soil cultivation machine according to claim 2 or any one of claims 3 to 10 insofar as it refers back to claim 2, characterized by, that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when the ambient temperature is above a predetermined discharge ambient threshold temperature and / or within a predetermined discharge ambient temperature range. [12] Soil cultivation machine according to claim 2 or any one of claims 3-11, insofar as it refers back to claim 2, characterized by , that the hydraulic drive system (46) is designed to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when the viscosity of the fluid in the drive hydraulic circuit (54) is below a predetermined threshold viscosity and / or within a predetermined viscosity range. [13] Soil cultivation machine according to claim 2 or any one of claims 3-12, insofar as it refers back to claim 2, characterized by, that the hydraulic drive system (46) is designed to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when the degree of contamination of the fluid in the drive hydraulic circuit (54) is above a predetermined discharge threshold contamination level and / or within a predetermined contamination level range. [14] Soil cultivation machine according to claim 2 or one of claims 3-13, insofar as it refers back to claim 2, characterized by , that the hydraulic drive system (46) is configured to operate the discharge valve arrangement (60) to discharge fluid to the fluid reservoir (62) when a predetermined time has elapsed since the last commissioning of the hydraulic drive system (46), or / and when a predetermined time has elapsed since the last fluid discharge from the drive hydraulic circuit (54).

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