Hydraulic drive system

Abstract

We provide hydraulic drive systems for self-propelled construction machinery. [Solution] A hydraulic drive system, particularly for a self-propelled construction machine, includes: at least one hydraulic pump that can be driven by a drive unit to transport hydraulic fluid; a hydraulic circuit that receives the hydraulic fluid transported by the at least one hydraulic pump and returns the hydraulic fluid to the at least one hydraulic pump; at least one hydraulic motor supplied with the hydraulic fluid transported by the at least one hydraulic pump through the hydraulic circuit; a discharge conduit assembly for discharging the hydraulic fluid from the hydraulic circuit to a hydraulic fluid storage device; and at least one cleaning conduit supplied from the hydraulic circuit for cleaning at least one hydraulic component of the hydraulic drive system with hydraulic fluid, wherein the at least one cleaning conduit branches off from the discharge conduit assembly and / or forms a conduit region of the discharge conduit assembly.

Description

Technical Field

[0001] The present invention relates to a hydraulic drive system used, for example, in construction machinery such as a soil compactor to drive the construction machinery to move on the ground or / and to supply hydraulic oil to an operating device of the construction machinery to operate the operating device of the construction machinery.

Background Art

[0002] A hydraulic drive system used for the operation of construction machinery generally includes at least one hydraulic pump that can be driven by a drive device such as a diesel power unit or an electric motor to transport hydraulic fluid, a hydraulic circuit that receives the hydraulic fluid transported by the at least one hydraulic pump and returns the hydraulic fluid to the at least one hydraulic pump, and at least one hydraulic motor through which the hydraulic fluid transported by the at least one hydraulic pump is supplied, for example, a hydraulic motor that drives one or more drive wheels or one or more earthwork rollers. When a device such as a hydraulic pump or a hydraulic motor that forms the hydraulic components of the hydraulic drive system operates, heat is generated, so it is necessary to release the heat from the area of the hydraulic components. For this purpose, hydraulic fluid is withdrawn from the hydraulic circuit, and the hydraulic fluid is guided to pass through the hydraulic components to be cooled, for example, in parallel to the hydraulic fluid guided to one or more hydraulic motors. As a result, the amount of hydraulic fluid transported to the hydraulic circuit by one or more hydraulic pumps is determined by the amount of hydraulic fluid required for the operation of one or more hydraulic motors and the amount of hydraulic fluid required to cool one or more hydraulic components.

[0003] Because the fluid pressure of the hydraulic fluid transported by at least one hydraulic pump or supplied to the hydraulic circuit is relatively high, relatively high power loss occurs when a portion of this hydraulic fluid, which is under relatively high pressure, is diverted to cool one or more hydraulic components of the hydraulic drive system. Furthermore, the amount of fluid under relatively high pressure that can be guided through the hydraulic components to be cooled or cleaned is limited, especially during the cold start phase, to avoid excessive pressure increases within the hydraulic components through which the hydraulic fluid used for cleaning or cooling flows, in the case of relatively viscous hydraulic fluids, generally hydraulic oil. Because the amount of hydraulic fluid diverted from the hydraulic circuit must be limited considering the pressure limitations during the cold start phase, there is a risk that, at high temperatures, a sufficient amount of hydraulic fluid will not be transported through the hydraulic components to be cooled. [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a hydraulic drive system that enables effective cooling of hydraulic components of a hydraulic drive system with minimal power loss, particularly for construction machinery such as soil compactors. [Means for solving the problem]

[0005] According to the present invention, this problem is solved in particular by a hydraulic drive system for self-propelled construction machinery, and said hydraulic drive system is - At least one hydraulic pump that can be driven by a drive unit to transport hydraulic fluid, - A hydraulic circuit that receives hydraulic fluid transported by at least one hydraulic pump and returns the hydraulic fluid to at least one hydraulic pump, - A hydraulic motor supplied with hydraulic fluid transported by at least one hydraulic pump via a hydraulic circuit, - A discharge conduit assembly for discharging hydraulic fluid from the hydraulic circuit to a hydraulic fluid storage device, - At least one cleaning conduit supplied from a hydraulic circuit for cleaning at least one hydraulic component of a hydraulic drive system with hydraulic fluid, Includes.

[0006] At least one flush conduit branches off from and / or forms a conduit region of the discharge conduit assembly.

[0007] In a hydraulic drive system configured according to the present invention, hydraulic fluid discharged toward a hydraulic fluid reservoir is used to clean or cool one or more hydraulic components, and this hydraulic fluid generally has a relatively low pressure. This significantly reduces the risk of mechanical overload on the hydraulic components to be cooled due to excessively high pressure of the hydraulic fluid used for cooling. Furthermore, it is not necessary to correspondingly increase the transport rate of at least one hydraulic pump to supply the hydraulic fluid used to cool the hydraulic components, because the hydraulic fluid used according to the present invention needs to be discharged from the hydraulic circuit anyway, i.e., discharged toward a hydraulic fluid reservoir. This results in relatively low power losses required to cool one or more hydraulic components.

[0008] A particularly advantageous configuration, especially when considering hydraulic fluid pressure, is proposed in which the discharge conduit assembly includes a discharge cooling conduit leading to a hydraulic fluid storage device, including a hydraulic fluid cooler, and a discharge bypass conduit running parallel to the discharge cooling conduit and leading to the hydraulic fluid storage device, and that at least one cleaning conduit branching from the discharge conduit assembly branches from and / or forms a conduit region of the discharge cooling conduit. The hydraulic fluid cooler provided in such a discharge cooling conduit is also a pressure-sensitive component and cannot be subjected to excessively high hydraulic fluid pressure. In such a drive system, the hydraulic fluid pressure of the hydraulic fluid supplied to the discharge cooling conduit and guided through the discharge cooling conduit to the hydraulic fluid storage device does not exceed a predetermined pressure, and at the same time, the hydraulic fluid used to cool at least one hydraulic component is designed to have a relatively low hydraulic fluid pressure to eliminate the potential risk of damage.

[0009] At least one cleaning conduit can branch off from a discharge cooling conduit upstream of the hydraulic fluid cooler, and / or form a conduit region of the discharge cooling conduit located upstream of the hydraulic fluid cooler. This allows for a structure in which at least one cleaning conduit is positioned parallel to the hydraulic fluid cooler, so that the cleaning conduit and the hydraulic fluid cooler can each be passed through by a portion of the hydraulic fluid flowing through the discharge cooling conduit. This can further reduce the hydraulic fluid pressure applied to the hydraulic components to be cooled.

[0010] Alternatively or additionally, at least one cleaning conduit may be specified to branch off from a discharge cooling conduit downstream of a hydraulic fluid cooler, and / or to form a conduit region of a discharge cooling conduit located downstream of the hydraulic fluid cooler. This embodiment takes advantage of the particular benefit that the hydraulic fluid flowing into the cleaning conduit is already cooled in a hydraulic fluid cooler located further upstream and can therefore be used particularly efficiently to cool at least one hydraulic component disposed in the cleaning conduit.

[0011] Regardless of whether the cleaning conduit branches off from the discharge cooling conduit upstream or downstream of the hydraulic fluid cooler, at least one cleaning conduit may be arranged in series with the hydraulic fluid cooler.

[0012] A bypass valve may be provided in the discharge bypass conduit to allow for selective opening or closing of the discharge bypass conduit to the flow, thereby allowing adjustment of the proportion of hydraulic fluid flowing through the discharge cooling conduit and thus imparting a mechanical load to the hydraulic fluid cooler, the bypass valve being switchable between a closed position, which preferably completely isolates the discharge bypass conduit from the flow of hydraulic fluid, and an open position, which preferably opens the discharge bypass conduit to the flow of hydraulic fluid to the maximum extent.

[0013] In this case, to avoid mechanical overload of the hydraulic fluid cooler due to excessively high hydraulic fluid pressure, it is advantageous, for example, if a bypass valve is switchable depending on the hydraulic fluid temperature of the hydraulic fluid flowing through the discharge conduit assembly.

[0014] In particular, for this reason, the bypass valve may be specified to be preferably fully open to through-flow when the hydraulic fluid temperature is lower than the switching temperature, and at least partially, preferably completely closed to through-flow when the hydraulic fluid temperature is higher than the switching temperature. When the hydraulic fluid has a relatively high temperature, the fluid pressure is generally lower due to the lower viscosity of the hydraulic fluid, so when the hydraulic fluid temperature is higher, mechanical overload of the hydraulic fluid cooler can be largely eliminated. When the hydraulic fluid temperature is lower, opening the bypass valve allows most of the discharged hydraulic fluid to flow through the discharge bypass conduit, so even with relatively viscous hydraulic fluid, it is possible to reduce or maintain the hydraulic fluid pressure in the discharge conduit assembly at a low pressure level, and therefore, in some cases, it is impossible for the portion of relatively cold, viscous hydraulic fluid flowing through the hydraulic fluid cooler to cause mechanical overload to the hydraulic fluid cooler.

[0015] Alternatively or additionally, the bypass valve may be specified to be switchable between a closed position and an open position, for example, depending on the hydraulic fluid pressure in the discharge conduit assembly.

[0016] For this reason, for example, the bypass valve may be preferably fully open to the flow when the hydraulic fluid pressure is higher than the switching pressure, and at least partially, preferably completely closed to the flow when the hydraulic fluid pressure is lower than the switching pressure. This method also ensures that the hydraulic fluid cooler is not subjected to excessive load, especially in the cold start phase when the hydraulic fluid has relatively high viscosity.

[0017] Bypass valves are, for example, - A thermostat valve, that is, for example, a valve that switches when it reaches a switching temperature, or - A check valve, that is, for example, a valve that switches when the switching pressure is reached, or -Valves that can be electrically switched depending on pressure and / or temperature, i.e., valves that can be switched depending on pressure and / or temperature, under control that takes hydraulic fluid pressure and / or hydraulic fluid temperature as input variables.

[0018] In the hydraulic drive system according to the present invention, at least one hydraulic pump may be a hydraulic component to be cleaned by at least one cleaning conduit. Alternatively or additionally, at least one hydraulic motor may be a hydraulic component to be cleaned by at least one cleaning conduit.

[0019] It should be noted that in the present invention, a hydraulic motor is understood not only as a device that generates driving torque for driving wheels, such as drive wheels or chainwheels, but also as any type of device that generates driving force or driving torque by supplying pressurized fluid. For example, in the present invention, a hydraulic piston / cylinder unit used to move parts or work devices of construction machinery can also be considered a drive motor supplied with hydraulic fluid by one or more hydraulic pumps.

[0020] Furthermore, the present invention relates to a construction machine, preferably a soil compactor, including a hydraulic drive system configured according to the present invention.

[0021] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The drawings show the following.

Brief Description of the Drawings

[0022] [Figure 1] It is a side view of a self-propelled construction machine configured as a soil compactor. [Figure 2] It is a circuit diagram of the hydraulic drive system for the construction machine illustrated in FIG. 1. [Figure 3] It is a circuit diagram of a hydraulic drive system having an alternative configuration for the construction machine illustrated in FIG. 1.

Modes for Carrying Out the Invention

[0023] FIG. 1 shows a side view of a self-propelled construction machine 10 configured in the form of a soil compactor. The construction machine 10 includes drive wheels 14 that can be driven to rotate by a drive device provided on the vehicle rear part 12 on both sides of the vehicle rear part 12. The vehicle rear part 12 is further provided with an operator's seat 16 for an operator who operates the construction machine 10. <00,00098>

[0024] In order to operate the construction machine 10, a soil roller 20 is provided on a vehicle front part 18 that is pivotally connected to the vehicle rear part 12. When the construction machine 10 moves on the ground 22 that is the work target, the soil roller 20 rolls on the ground. Depending on the surface structure of the soil roller, the soil roller can be used to compress the ground 22 that has been traveled on, or, in the case of a structured surface, to break up a hard ground such as a concrete ground.

[0025] Before describing in detail below, with reference to Figures 2 and 3, the hydraulic drive system for such earthmoving machinery 10, it should be noted that the self-propelled construction machine 10 shown in Figure 1 is merely one example of such construction machinery. When the construction machine 10 is configured as a soil compactor, it may also have earthmoving rollers at the rear of the vehicle 12, in which case one or both earthmoving rollers may be driven to rotate in order to move the construction machine 10 on the ground 22. It can also be configured as a pivot-steering soil compactor, a wheel loader, etc. Furthermore, when such construction machine 10 is configured as, for example, a bulldozer, it may have a tracked chassis.

[0026] Figure 2 shows the main system areas of a hydraulic drive system 24 for such a self-propelled construction machine 10. The hydraulic drive system 24 includes a hydraulic pump 28 driven by a drive unit 26. In a conventional configuration, the drive unit 26 may be powered, for example, by a diesel internal combustion engine. When configured as an electro-hydraulic drive system, the drive unit may include an electric motor.

[0027] The hydraulic drive system 24 further includes a hydraulic circuit 30 through which, in the illustrated embodiment, two hydraulic motors 32, 34 are hydraulically connected to a hydraulic pump 28, thereby supplying pressurized hydraulic fluid, generally hydraulic oil, to the two hydraulic motors 32, 34, or allowing hydraulic fluid to recirculate from the two hydraulic motors 32, 34.

[0028] The hydraulic circuit 30 includes a first conduit region 36 connecting a hydraulic pump 28 to two hydraulic motors 32 and 34, and a second conduit region 38 connecting the hydraulic pump 28 to the two hydraulic motors 32 and 34. Depending on the planned direction of movement and the corresponding rotation direction of the hydraulic motors 32 and 34, the hydraulic fluid discharged from the hydraulic pump 28 is guided through the conduit region 36 to the hydraulic motors 32 and 34 and returned to the hydraulic pump 28 through the second hydraulic region 38, or the hydraulic fluid is guided through the second conduit region 38 to two hydraulic motors 32 and 34, which may be located on each of the drive wheels 14 positioned on the sides of the rear 12 of the vehicle in the case of the construction machine 10 shown in Figure 1, for example, and returned to the hydraulic pump 28 through the first conduit region 36.

[0029] The hydraulic circuit 30 shown in Figure 2 is basically a closed circuit, but under various conditions of the hydraulic drive system 24, it is necessary to supply hydraulic fluid to the hydraulic circuit 30 from the hydraulic fluid storage device 42 or the installed pressure fluid storage device 44, or to discharge hydraulic fluid from the hydraulic circuit 30. Supply of hydraulic fluid may be necessary, for example, when the pressure in the hydraulic circuit 30 falls below an assigned threshold, particularly on the low-pressure side, due to unavoidable leakage in the hydraulic motors 32, 34 or the hydraulic pump 28, or when hydraulic fluid is actively discharged, for example, because the temperature of the hydraulic fluid in the hydraulic fluid circuit is too high.

[0030] A supply valve assembly, collectively indicated by reference numeral 46, is provided to supply hydraulic fluid. The supply valve assembly 46 includes two first supply valves 461 and 462, located in the first conduit region 36 of the hydraulic fluid circuit 30, and second supply valves 463 and 464, located in the second conduit region 38 of the hydraulic fluid circuit 30. Depending on whether the shut-off valves 68 and 70 of the main brake 72 are in a shut-off state when the main brake is operating as shown in Figures 2 and 3, or in an open state that allows hydraulic fluid transported by the hydraulic pump 28 to flow through the conduit regions 36 and 38 to the hydraulic motors 32 and 34, hydraulic fluid supplied from the hydraulic fluid storage device 42, through a hydraulic pump (not shown), or supplied from the pressure fluid storage device 44, is supplied to the hydraulic fluid circuit 30 through one of the four supply valves 461, 462, 463, and 464, each connected to the low-pressure side in the operating state.

[0031] A discharge valve assembly, collectively designated 48, is provided for discharging hydraulic fluid. The discharge valve assembly 48 includes a shut-off valve 50 that opens or closes the flow path to the discharge conduit assembly, collectively designated 52, and a control valve 54 located upstream of the shut-off valve 50 that selectively connects the shut-off valve 50 to a first conduit region 36 and a second conduit region 38, or does not selectively connect to either of these conduit regions. In this manner, it can be ensured that the discharge of hydraulic fluid always occurs on the low-pressure side of the hydraulic circuit 30, i.e., from the conduit region of the first conduit region 36 and the second conduit region 38, which is used to return the hydraulic fluid transported by the hydraulic pump 28 to the two hydraulic motors 32, 34 after it has flowed through them. The discharge valve assembly 48 further includes pressure-holding valves 74, 76 in the direction of flow between the two valves 50, 54 and downstream of the shut-off valve 50, which ensure that as a result of the discharge process, the fluid pressure in the hydraulic fluid circuit 30 cannot fall below a certain minimum pressure level.

[0032] The discharge conduit assembly 52 includes a discharge cooling conduit 56 and a discharge bypass conduit 58 running parallel to the discharge cooling conduit 56. Both the discharge cooling conduit 56 and the discharge bypass conduit 58 lead to the hydraulic fluid storage device 42.

[0033] A hydraulic fluid cooler 60 is provided in the discharge cooling conduit 56. Inside the hydraulic fluid cooler 60, the hydraulic fluid discharged from the hydraulic circuit 30 transfers heat to, for example, the ambient air, thereby cooling at least a portion of the discharged hydraulic fluid before it is introduced into the hydraulic fluid storage device 42.

[0034] A bypass valve 62 is provided in the discharge bypass conduit 58. In the closed position, the bypass valve 62 preferably completely isolates the discharge bypass conduit 58 from the flow of hydraulic fluid, so that the entire discharged hydraulic fluid flows through the discharge cooling conduit 56 and the hydraulic fluid cooler 60 provided in the discharge cooling conduit 56. In the open position, the discharge bypass conduit 58 is opened to the maximum extent from the flow of hydraulic fluid. In this state, the flow resistance of the bypass valve 62 is relatively low compared to the flow resistance of the hydraulic fluid cooler 60, so in the open position of the bypass valve 62, most of the discharged hydraulic fluid flows through the discharge bypass conduit 58 to the hydraulic fluid storage device 42.

[0035] The bypass valve may be configured as a thermostat valve that switches from an open position to a closed position when the hydraulic fluid reaches a switching temperature in the range of approximately 60°C, thereby opening the discharge bypass conduit 58 to the flow when the hydraulic fluid temperature is lower than the switching temperature, and thus avoiding excessive load on the hydraulic fluid cooler 60 due to excessively high fluid pressure, especially in the case of relatively viscous hydraulic fluids. When the switching temperature is reached, that is, when the temperature of the hydraulic fluid rises and the viscosity decreases, the bypass valve 62 moves to the closed position, thereby ensuring that the hydraulic fluid directed towards the hydraulic fluid storage device 42 is sufficiently cooled, provided that no excessive pressure load is applied to the hydraulic fluid cooler 60.

[0036] In an alternative embodiment, the bypass valve 62 may be configured as a check valve, which is switched to the open position by a relatively large pressure drop when the temperature of the hydraulic fluid decreases and therefore the viscosity of the hydraulic fluid increases, and is switched to the closed position as the temperature of the hydraulic fluid increases and the viscosity decreases, the pressure drop also decreases, and as the temperature of the hydraulic fluid rises, the hydraulic fluid is directed to the discharge cooling conduit 56 to flow through the hydraulic fluid cooler 60.

[0037] Furthermore, the bypass valve 62 may be under the control of the control unit and configured as an electrically switchable valve. Possible input variables for switching such a valve include the pressure and / or temperature of the hydraulic fluid. Therefore, when the temperature of the hydraulic fluid is relatively low, and consequently a relatively large pressure drop occurs in the hydraulic fluid cooler 60, opening such a valve opens the discharge bypass conduit 58, ensuring that most of the hydraulic fluid is discharged through the discharge bypass conduit 58 to avoid an excessively large pressure rise in the hydraulic fluid cooler 60. When the temperature of the hydraulic fluid is sufficiently high and its viscosity is low, and consequently the pressure rise in the hydraulic fluid cooler 60 is small, the electrically switchable valve can be set to the closed position, thereby ensuring sufficient cooling of the hydraulic fluid discharged from the hydraulic circuit 30.

[0038] Regardless of its structure, the bypass valve 62 can transition almost continuously between the open and closed positions depending on temperature and / or pressure. Thus, from the cold start phase, when relatively low-temperature and therefore highly viscous hydraulic fluid is used, the bypass valve 62 gradually transitions from the open to the closed position as the temperature of the hydraulic fluid rises and the viscosity decreases accordingly, allowing more of the discharged hydraulic fluid to flow through the hydraulic fluid cooler 60.

[0039] The pressure-dependent or temperature-dependent switching of the bypass valve 62 is performed primarily to protect the hydraulic fluid cooler 60 from overload and the resulting potential damage; therefore, the variables considered for switching the bypass valve 62, namely temperature or pressure, can be detected, for example, in the region of the hydraulic fluid cooler 60. For example, pressure sensors can be provided in the discharge cooling conduit 56 upstream and downstream of the hydraulic fluid cooler 60 to detect the pressure difference occurring in the hydraulic fluid cooler 60 and to open or close the bypass valve 62 depending on that pressure difference. The temperature of the hydraulic fluid can also be detected, if it is also considered as an operating variable, in the region of the hydraulic fluid cooler 60, for example, upstream of it. Obviously, in other regions of the hydraulic circuit 30, such as the region of the hydraulic fluid storage device 42, consideration of temperature and / or pressure values ​​is possible if it is possible to adequately predict the mechanical load that occurs in the hydraulic fluid cooler 60 depending on temperature or pressure.

[0040] The hydraulic drive system 40 further includes a cleaning conduit 64, which, in the embodiment shown in Figure 2, branches off from the discharge cooling conduit 56 upstream of the hydraulic fluid cooler 60, or supplies the conduit region of the discharge conduit assembly 52 or the discharge cooling conduit 56 located upstream of the hydraulic fluid cooler 60. Through the cleaning conduit 64, the hydraulic fluid flowing through the discharge cooling conduit 56 is led to the hydraulic components of the hydraulic drive system 40, which are to be cleaned with the hydraulic fluid and thereby cooled. In the embodiment shown in Figure 2, the hydraulic pump 28 forms a hydraulic component such that the hydraulic fluid discharged from the hydraulic circuit 30 is supplied to the hydraulic fluid cooler 60 to cool the fluid in the hydraulic fluid cooler 60 before releasing the heat generated in the region of the hydraulic pump 28 and introducing the heat-absorbing fluid into the hydraulic cleaning tank 42.

[0041] In the illustrated embodiment, the hydraulic pump 28 is also a hydraulic component and needs to be protected from excessively high pressure, especially in the system region through which the hydraulic fluid flows. Therefore, it is particularly advantageous to integrate the cleaning conduit 64 into the discharge cooling conduit 56 or to branch it off from the discharge cooling conduit 56. This is because, due to the function of the bypass valve 62 described above, the discharge cooling conduit 56, and consequently the cleaning conduit 64, are only permeated by some or most of the discharged hydraulic fluid when the temperature of the discharged hydraulic fluid is sufficiently high or its viscosity is sufficiently low. For this reason, for example, if the bypass valve 62 is switched depending on temperature or pressure, it is advantageous to detect the temperature or pressure of the discharged hydraulic fluid upstream of the cleaning conduit 64, or upstream of the hydraulic components to be cleaned or cooled by the cleaning conduit 64. For example, at the branching point 66, that is, at the point in the discharge conduit assembly 52 where the discharge bypass conduit 58 on one side and the discharge cooling conduit 56 or cleaning conduit 64 on the other side branch off from each other, temperature sensors or pressure sensors can be provided to detect variables that need to be considered.

[0042] An alternative embodiment of the hydraulic drive system 40 is shown in Figure 3. This is consistent with the embodiment in Figure 2, particularly with respect to the structure of the hydraulic circuit 30, and can therefore be referred to in the description above.

[0043] The main difference from the embodiment shown in Figure 2 is that the cleaning conduit 64 either branches off from the discharge cooling conduit 56 downstream of the hydraulic fluid cooler 60, or forms a conduit region of the discharge cooling conduit 56 downstream of the hydraulic fluid cooler 60. This modified example has the advantage of enabling more efficient cooling of the hydraulic component, in this case the hydraulic pump 28, because the hydraulic fluid discharged from the hydraulic circuit 30 and introduced into the discharge cooling conduit 56 is already cooled in the hydraulic fluid cooler 60 before flowing through the hydraulic component to be cooled (in the illustrated embodiment, the hydraulic pump 28).

[0044] Basically, the cleaning conduit 64 can be routed parallel to the hydraulic fluid cooler 60, and therefore, obviously, parallel to the hydraulic bypass conduit 58. As shown in Figure 2, the cleaning conduit 64 could branch off from the discharge cooling conduit 56 upstream of the hydraulic fluid cooler 60, and rejoin the discharge cooling conduit 56 downstream of the hydraulic fluid cooler 60, as shown in Figure 3. In this variation as well, the system regions of the hydraulic fluid cooler 60 and the hydraulic pump 28, which pass through each other parallel to one another, are passed through only by the discharged hydraulic fluid when the discharge cooling conduit 56 is open to the flow of most of the discharged hydraulic fluid, or when the discharge bypass conduit 58 is isolated from the flow by the bypass valve 62.

[0045] Furthermore, it is possible to combine the two modified examples shown in Figures 2 and 3 in order to cool multiple hydraulic components of the hydraulic drive system 40 with the discharged hydraulic fluid. In addition, multiple hydraulic components to be cooled can be incorporated into the cleaning conduit 64 in series and / or parallel, thereby allowing components such as the hydraulic motors 32 and 34, rather than just the hydraulic pump 28, to be cooled by the discharged hydraulic fluid, or vice versa. [Explanation of Symbols]

[0046] 10 Construction Machinery 12 Rear of the vehicle 14 drive wheels 16 Control seat 18 Front of the vehicle 20 Earthmoving roller 22 Ground 24 Hydraulic drive system 26 Drive unit 28 Hydraulic pump 30 Hydraulic Circuit 32, 34 Hydraulic motor 36. First conduit region 38 Second conduit region 40 Hydraulic drive system 42. Hydraulic fluid storage devices, hydraulic cleaning tanks 44 Pressure fluid storage device 46 Supply valve assembly 461, 462 First supply valve 463, 464 Second supply valve 48. Discharge valve assembly 50 Shut-off valve 52 Discharge conduit assembly 54. Regulating valve 56 Discharge cooling conduit 58 Discharge Bypass Conduit 60 Hydraulic fluid cooler 62 Bypass valve 64. Flushing conduit 66 Branching Point 68, 70 Shut-off valves 72 Main brake 74, 76 Pressure-holding valve

Claims

1. In particular, a hydraulic drive system for self-propelled construction machinery, - At least one hydraulic pump (28) which can be driven by a drive unit (26) to transport hydraulic fluid, - A hydraulic circuit (30) that receives hydraulic fluid transported by at least one of the hydraulic pumps (28) and returns the hydraulic fluid to at least one of the hydraulic pumps, -Through the hydraulic circuit (30), at least one hydraulic motor (32, 34) is supplied with hydraulic fluid transported by at least one hydraulic pump (28), - A discharge conduit assembly (52) for discharging hydraulic fluid from the hydraulic circuit (30) to a hydraulic fluid storage device (42), - At least one cleaning conduit (64) supplied from the hydraulic circuit (30) for cleaning at least one hydraulic component of the hydraulic drive system (40) with hydraulic fluid, Includes, A hydraulic drive system in which at least one of the cleaning conduits (64) branches off from the discharge conduit assembly (52) and / or forms a conduit region of the discharge conduit assembly (52).

2. The hydraulic drive system according to claim 1, characterized in that the discharge conduit assembly (52) includes a discharge cooling conduit (56) that includes a hydraulic fluid cooler (60) and leads to the hydraulic fluid storage device (42), and a discharge bypass conduit (58) that runs parallel to the discharge cooling conduit (56) and leads to the hydraulic fluid storage device (42), and at least one of the cleaning conduits (64) that branches off from the discharge conduit assembly (52) is branched off from the discharge cooling conduit (56) and / or forms a conduit region of the discharge cooling conduit (56).

3. The hydraulic drive system according to claim 2, characterized in that at least one of the cleaning conduits (64) branches off from the discharge cooling conduit (56) upstream of the hydraulic fluid cooler (60), and / or forms a conduit region of the discharge cooling conduit (56) located upstream of the hydraulic fluid cooler (60).

4. The hydraulic drive system according to claim 3, characterized in that at least one of the cleaning conduits is arranged parallel to the hydraulic fluid cooler (60).

5. The hydraulic drive system according to any one of claims 2 to 4, characterized in that at least one of the cleaning conduits (64) branches off from the discharge cooling conduit (56) downstream of the hydraulic fluid cooler (60), and / or forms a conduit region of the discharge cooling conduit (56) located downstream of the hydraulic fluid cooler (60).

6. The hydraulic drive system according to any one of claims 2 to 5, characterized in that at least one of the cleaning conduits (64) is arranged in series with respect to the hydraulic fluid cooler (60).

7. A bypass valve (62) is provided in the discharge bypass conduit (58), and the bypass valve (62) is switchable between a closed position which preferably completely isolates the discharge bypass conduit (58) from the flow of hydraulic fluid and an open position which preferably opens the discharge bypass conduit (58) to the maximum extent possible from the flow of hydraulic fluid, as described in any one of claims 2 to 6.

8. The hydraulic drive system according to claim 7, characterized in that the bypass valve (62) is switchable between the closed position and the open position depending on the hydraulic fluid temperature, preferably the temperature of the hydraulic fluid flowing through the discharge conduit assembly (52).

9. The hydraulic drive system according to claim 8, characterized in that the bypass valve (62) is preferably maximally open to through-flow when the hydraulic fluid temperature is lower than the switching temperature, and at least partially, preferably completely closed to through-flow when the hydraulic fluid temperature is higher than the switching temperature.

10. The hydraulic drive system according to any one of claims 7 to 9, characterized in that the bypass valve (62) is switchable between the closed position and the open position depending on the hydraulic fluid pressure, preferably the hydraulic fluid pressure in the discharge conduit assembly (52).

11. The hydraulic drive system according to claim 10, characterized in that the bypass valve (62) is preferably maximally open to the flow when the hydraulic fluid pressure is higher than the switching pressure, and is at least partially, preferably completely closed to the flow when the hydraulic fluid pressure is lower than the switching pressure.

12. The bypass valve (62) - Thermostat valve, or - Check valve, or - A valve that can be electrically switched depending on pressure and / or temperature. A hydraulic drive system according to any one of claims 7 to 11, characterized by including the following:

13. The hydraulic drive system according to any one of claims 1 to 12, characterized in that at least one of the hydraulic pumps (28) is a hydraulic component to be cleaned by at least one of the cleaning conduits (64).

14. The hydraulic drive system according to any one of claims 1 to 13, characterized in that at least one of the hydraulic motors (32, 34) is a hydraulic component to be cleaned by at least one of the cleaning conduits (64).

15. Earthmoving machinery, preferably a soil compactor, comprising a hydraulic drive system (24) according to any one of claims 1 to 14.

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