Electrohydraulic drive system

Abstract

To provide an electrohydraulic drive system for a ground processing machine having at least one drive roll.SOLUTION: An electrohydraulic drive system includes: at least one traction hydraulic pump that can be driven by a drive electric motor to transport hydraulic fluid; at least two traction hydraulic motors to which hydraulic fluid is supplied by the at least one traction hydraulic pump; a valve assembly that is disposed in each traction hydraulic motor and includes at least one switching valve unit; and a control unit for operating the valve assemblies such that, in a basic drive state, hydraulic fluid is supplied from the at least one traction hydraulic pump to each traction hydraulic motor to generate a drive torque, and, in a high pressure drive state, hydraulic fluid is supplied from the at least one traction hydraulic pump to the at least one traction hydraulic motor not to generate drive torque.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an electro-hydraulic drive system for an earthworking machine having at least one drive roll, for example a soil compactor.

Background Art

[0002] An earthworking machine configured as a soil compactor may include, for example as drive rolls, two earthworking rollers, in particular compactor rollers, which are arranged continuously in the longitudinal direction of the soil compactor and are rotatable about mutually parallel axes of rotation. The two earthworking rollers each supplying a drive roll can be driven by an electro-hydraulic drive system to rotate about the respectively arranged axis of rotation. Arranged on each earthworking roller, the electro-hydraulic drive system can include one or two traction hydraulic motors, and the traction hydraulic motors are supplied with working fluid in pairs or together by one or more traction hydraulic pumps in order to generate a drive torque.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The problem of the present invention is to provide an electro-hydraulic drive system for an earthworking machine, an earthworking machine configured using the electro-hydraulic drive system, and a method for operating the earthworking machine, whereby a high utilization efficiency of the electrical energy used for driving is achieved.

Means for Solving the Problems

[0004] According to the present invention, this problem is solved by an electro-hydraulic drive system for an earthworking machine having at least one drive roll, the electro-hydraulic drive system comprising - at least one traction hydraulic pump that can be driven by a drive electric motor for transferring working fluid, and - At least two traction hydraulic motors supplied with a working fluid by at least one traction hydraulic pump, - A valve assembly, - A control unit for operating or controlling the valve assembly such that, in a basic drive state, a working fluid is supplied from at least one traction hydraulic pump to each traction hydraulic motor to generate a drive torque, and in a high-pressure drive state, a working fluid is supplied from at least one traction hydraulic pump to at least one traction hydraulic motor so as not to generate a drive torque.

[0005] The present invention utilizes the recognition that an improvement in the efficiency of a hydraulic drive system can be achieved by increasing the hydraulic pressure level. In order to obtain an increase in the pressure level, an electro-hydraulic drive system constructed according to the present invention is configured to stop the operation of each of the traction hydraulic motors supplied with the working fluid in parallel, or to switch to a non-pressurized state. Since the pressure level of the traction hydraulic motor that is still supplied with the working fluid to generate a drive torque correspondingly increases, the traction hydraulic motor operates with higher efficiency. By increasing the efficiency of the traction hydraulic motor that is still supplied with the working fluid to generate a drive torque, the flow loss in the traction hydraulic motor that has been stopped or switched to a non-pressurized state is excessively compensated.

[0006] In such a state where the working fluid is supplied only to a part of the traction hydraulic motors to generate a drive torque, for example, when a soil compactor is used to compact asphalt behind an asphalt finisher on a substantially horizontal base layer, it is possible to shift to a main operating point during work. In this state, for example, it is possible to drive only one of the two compactor rollers that are basically used as drive rolls to rotate, or to use only one of the two traction hydraulic motors disposed on each of the two compactor rollers to generate a drive torque.

[0007] To supply hydraulic fluid to different traction hydraulic motors, at least one hydraulic circuit is provided with at least two traction hydraulic motors that are supplied with hydraulic fluid in parallel by at least one traction hydraulic pump, and it is proposed that a valve assembly be arranged on at least two traction hydraulic motors of at least one traction hydraulic circuit and include at least one switching valve unit.

[0008] At this time, in order to adjust the traction hydraulic motor to be suitable for different operating modes, when at least one switching valve unit arranged on the traction hydraulic motor is switched to the basic drive state switching position, the hydraulic fluid transferred by at least one traction hydraulic pump is supplied to the traction hydraulic motor to generate driving torque. Then, when at least one switching valve unit arranged on the traction hydraulic motor is switched to the high-pressure drive state switching position, a bypass flow path arranged on the traction hydraulic motor and parallel to the traction hydraulic motor can be opened for through-flow, or / and a short circuit of the flow can be caused between two fluid connections of the traction hydraulic motor.

[0009] In a particularly advantageous embodiment for switching the traction hydraulic motor between an operating state and a non-operating state, it is possible to provide at least two traction hydraulic circuits, and each traction hydraulic circuit is provided with a traction hydraulic pump and at least two traction hydraulic motors that are supplied with hydraulic fluid in parallel by the traction hydraulic pump.

[0010] At this time, it is possible to arrange an electric drive motor on each traction hydraulic pump, and each traction hydraulic pump can operate independently of other traction hydraulic pumps by an electric drive motor arranged individually on each traction hydraulic pump.

[0011] Regarding the simple structure of the valve assembly, in each traction hydraulic circuit, the valve assembly may be disposed in each traction hydraulic motor to block a bypass flow path parallel to the traction hydraulic motor at the basic drive state switching position and open it for through-flow at the high-pressure drive state switching position, including a switching valve unit.

[0012] In an alternative structure, at least one traction hydraulic circuit may be provided in the electro-hydraulic drive system. At least one traction hydraulic circuit is provided with a traction hydraulic pump and at least two, preferably at least four, traction hydraulic motors to which the working fluid is supplied in parallel by the traction hydraulic pump.

[0013] When the electro-hydraulic drive system is configured to have one or a single traction hydraulic circuit, the valve assembly may be disposed in each traction hydraulic motor to block a bypass flow path parallel to the traction hydraulic motor at the basic drive state switching position and open it for through-flow at the high-pressure drive state switching position, including a switching valve unit.

[0014] In order to obtain high variability when operating or stopping the operation of the traction hydraulic motor, it is proposed that the traction hydraulic motor forms at least two groups of traction hydraulic motors that are each supplied in parallel by a traction hydraulic pump. The valve assembly is disposed in each group of traction hydraulic motors and includes at least one shut-off valve unit for selectively blocking the supply of the working fluid transferred by the traction hydraulic pump to the group of traction hydraulic motors and opening the group of traction hydraulic motors for the supply of the working fluid transferred by the traction hydraulic pump.

[0015] To disconnect or connect the individual traction hydraulic motor groups as determined, the valve assembly may include two shut-off valve units arranged on both sides of the traction hydraulic motor group in the fluid flow direction and disposed in each traction hydraulic motor group.

[0016] In a further alternative embodiment, the valve assembly can include two switching valve units arranged in each traction hydraulic motor. In the basic drive state switching position, the switching valve unit arranged in each traction hydraulic motor enables the supply of the hydraulic fluid transferred to the traction hydraulic motor by the traction hydraulic pump. In the high-pressure drive state switching position, a bypass flow path parallel to the traction hydraulic motor is opened to cause a short circuit of the flow between the fluid connection parts of the traction hydraulic motor.

[0017] During operation, i.e., when there is fluid pressure, it is proposed to configure at least one, preferably each switching valve unit as a proportional valve so that one or more traction hydraulic motors can be selectively switched on or off. The possibility of switching one or more traction hydraulic motors during the running operation is particularly advantageous when the traction hydraulic motor is also used to generate braking torque as required.

[0018] The problem mentioned at the beginning is further solved by an earthmoving machine, preferably a soil compactor, comprising at least one drive roll and an electro-hydraulic drive system configured according to the present invention.

[0019] Depending on the use purpose of each earthmoving machine, at least one, preferably each drive roll may include an earthwork roller. Also, it may be defined that at least one drive roll includes at least one wheel, particularly a rubber wheel.

[0020] The problem mentioned at the beginning is further solved by a method for operating an earthmoving machine configured according to the present invention. In the method, at least one of the following measures may be provided: - In the high-pressure drive state, in the first part of the traction hydraulic motor, the switching valve units arranged respectively are switched to the high-pressure drive state switching position. - When shifting from the high-pressure drive state to the braking state of the electro-hydraulic drive system, at least a part, preferably all, of the switching valve units in the first part of the traction hydraulic motor are switched to the basic drive state switching position.

[0021] In order to be able to generate sufficient drive torque in the high-pressure drive state, in the method according to the present invention, it is also possible to switch the switching valve units arranged respectively in the second part of the traction hydraulic motor to the basic drive state switching position.

[0022] For example, in order to evenly distribute the load as determined to two axles or two sides of the earthmoving machine, the first part of the traction hydraulic motor can be defined to include half of the traction hydraulic motor of the earthmoving machine. The second part of the traction hydraulic motor can include, for example, the other half of the traction hydraulic motor of the earthmoving machine.

[0023] Furthermore, at this time, the traction hydraulic motor in the first part of the traction hydraulic motor may be arranged on at least one first drive roll of the earthmoving machine that is rotatable around the first rotation axis, or / and the traction hydraulic motor in the second part of the traction hydraulic motor may be arranged on at least one second drive roll of the earthmoving machine that is rotatable around the second rotation axis. Therefore, in the high-pressure operation state, all the operating traction hydraulic motors can act on one axle.

[0024] To distribute the load to two axles, a part of the traction hydraulic motor of the first part of the traction hydraulic motor may be disposed on at least one first drive roll of the earthmoving machine rotatable around the first rotation axis, and a part of the traction hydraulic motor of the second part of the traction hydraulic motor may be disposed on at least one first drive roll of the earthmoving machine rotatable around the first rotation axis, or / and, a part of the traction hydraulic motor of the first part of the traction hydraulic motor may be disposed on at least one second drive roll of the earthmoving machine rotatable around the second rotation axis, and a part of the traction hydraulic motor of the second part of the traction hydraulic motor may be disposed on at least one second drive roll of the earthmoving machine rotatable around the second rotation axis.

[0025] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The following figures are shown:

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0027] FIG. 1 schematically shows a geotechnical machine, generally designated by reference numeral 10, configured as a soil compactor, for example. The geotechnical machine 10 configured as a soil compactor includes two drive rolls 12, 14 that are arranged continuously in its longitudinal direction and each configured as a soil roller. The drive roll 12 is rotatable about a first rotation axis D1, and the drive roll 14 is rotatable about a second rotation axis D2. Two traction hydraulic motors M1, M2 or M3, M4 are disposed on each of the two drive rolls 12, 14. For example, the traction hydraulic motors M1, M2, M3, M4 disposed on each drive roll 12 or 14 may be arranged at respective axial ends thereof.

[0028] As shown in FIG. 1, the two drive rolls 12, 14 may be configured as split soil rollers having respective segments 12a, 12b and 14a, 14b. Since one of the four traction hydraulic motors M1, M2, M3, M4 is disposed on each segment, the two segments 12a, 12b can be driven to rotate independently of each other about the rotation axis D1 by the traction hydraulic motors M1, M2 disposed on the segments, and the two segments 14a, 14b can be driven to rotate independently of each other about the rotation axis D2 by the traction hydraulic motors M3, M4 disposed on the segments. However, basically, at least one of the two drive rolls 12, 14 may be configured as a highly rigid soil roller that is driven to rotate by the traction hydraulic motors disposed at both of its axial ends, respectively.

[0029] Figure 2 shows an alternative embodiment of such a soil working machine 10 configured, for example, as a soil roller. The soil working machine 10 in Figure 2 includes a drive roll 12 configured as a soil roller at one of its longitudinal end regions. Two traction hydraulic motors M1, M2 are arranged on the drive roll 12. Also in this embodiment, the drive roll 12 may be configured as a highly rigid soil roller itself that is driven to rotate by the traction hydraulic motors arranged at both of its axial ends, or, as shown in Figure 1, it may include two segments that can be driven to rotate independently of each other around the rotation axis D1 by the traction hydraulic motors arranged respectively. At the other longitudinal end region of the soil working machine 10, drive rolls 16, 18, 20, 22 configured as wheels are provided respectively. The drive rolls may be arranged in pairs, for example, and each pair consisting of wheels or drive rolls 16, 18 or 20, 22 can be driven to rotate by a traction hydraulic motor M3 or M4 arranged for each pair.

[0030] It should be noted that other embodiments of such soil working machines are also applicable in the context of the electro-hydraulic drive system described below. For example, in a soil working machine configured as a soil compactor, a pair of drive wheels forming drive rolls may be provided at the rear of the vehicle, while at the front of the vehicle, the soil roller may act as a drive roll. The principle of the present invention is applicable to soil working machines or soil compactors with a pivot steering system, as well as to soil working machines divided into a front part and a rear part of the vehicle.

[0031] In Figure 3, an electro-hydraulic drive system configured according to the principle of the present invention is for the soil working machine 10 shown in Figure 1 or Figure 2, for example, and is generally denoted by reference numeral 24. In the illustrated embodiment, the electro-hydraulic drive system 24 includes two traction hydraulic circuits K1, K2. Two traction hydraulic motors M1, M2 may be arranged in the traction hydraulic circuit K1, and two traction hydraulic motors M3, M4 may be arranged in the traction hydraulic circuit K2.

[0032] The traction hydraulic circuit K1 is further provided with a traction hydraulic pump P1. The traction hydraulic pump P1 can be driven by an electric drive motor E1 individually arranged on the traction hydraulic pump P1 in order to transfer fluid through the traction hydraulic circuit K1 and the traction hydraulic motors M1 and M2 arranged in parallel with each other in the traction hydraulic circuit K1. Similarly, a traction hydraulic pump P2 is provided in the traction hydraulic circuit K2. The traction hydraulic pump P2 can be driven by an electric drive motor E2 arranged on the traction hydraulic pump P2 in order to transfer fluid through the traction hydraulic circuit K2 and the traction hydraulic motors M3 and M4 connected in parallel with each other and thus allowing the working fluid to flow through.

[0033] Each of the traction hydraulic motors M1, M2, M3, and M4 is provided with bypass flow paths B1, B2, B3, and B4 connected in parallel to each of the traction hydraulic motors M1, M2, M3, and M4. The valve assembly of the electro-hydraulic drive system, which is generally designated by reference numeral 26, includes switching valve units S1, S2, S3, and S4 arranged on each of the four traction hydraulic motors M1, M2, M3, and M4 and disposed in the bypass flow paths B1, B2, B3, and B4 respectively arranged.

[0034] Similar to the two electric drive motors E1, E2, the switching valve units S1, S2, S3, S4 are under the control of a control unit, which is generally designated by reference numeral 28. By means of the control unit 28, the switching valve units S1, S2, S3, S4 can be switched between a basic drive state switching position and a high-pressure drive state switching position. In the basic drive state switching position shown for each switching valve unit S1, S2, S3, S4, the bypass flow paths B1, B2, B3, B4 provided respectively are blocked against the flow-through of the hydraulic fluid, so that the hydraulic fluid transferred by each traction hydraulic pump P1 or P2 through each traction hydraulic circuit K1, K2 flows through the two traction hydraulic motors M1, M2, M3, M4 respectively, and thus, preferably, the same drive torque is generated by all four traction hydraulic motors M1, M2, M3, M4.

[0035] In the high-pressure drive state switching position of the switching valve units S1, S2, S3, S4, the bypass flow paths B1, B2, B3, B4 provided respectively are open for the flow-through of the hydraulic fluid, so that the respectively provided traction hydraulic pumps P1, P2 are still operating, and due to the reduction of the flow resistance, the hydraulic fluid transferred by each traction hydraulic pump P1, P2 is transferred through the respectively provided traction hydraulic motors M1, M2, M3, M4, and in the traction hydraulic motors M1, M2, M3, M4, as long as the respectively provided switching valve units S1, S2, S3, S4 are in the high-pressure drive state switching position, no drive torque is generated. Basically, in the high-pressure drive state of the electro-hydraulic drive system 24 or in the switching valve units S1, S2 or S3, S4 switched to the high-pressure drive state switching position, it is not necessary to operate the respectively provided traction hydraulic pumps P1 or P2. If the traction hydraulic pumps P1 or P2 are stopped, the traction hydraulic motors M1, M2 or M3, M4 are driven by the respectively provided drive rolls rolling on the ground and circulate the fluid between their fluid connections 30, 32 short-circuited through the respectively provided bypass flow paths B1, B2 or B3, B4.

[0036] The switching valve units S1, S2, S3, S4 may be configured as proportional valves, for example. By this, it is pointed out that switching between the two switching positions is possible during the running operation without causing switching surges. In the case of a simpler structure, these switching valve units S1, S2, S3, S4 may be configured as continuous valves or valves acting in a binary manner that can only be switched between an open state and a closed state. In order to avoid switching surges, it is advantageous for such valves to be switched between the two switching positions in a stopped state, i.e., a non-pressurized state.

[0037] In the normal operating operation of the geotechnical machine 10 configured as a soil compactor, for example, or the electro-hydraulic drive system 24 shown in FIG. 3, the two traction hydraulic pumps P1, P2 are driven by the arranged electric drive motors E1, E2. The switching valve units S1, S2, S3, S4 are in their basic drive state switching positions, and in the basic drive state switching positions, the through-flow of the bypass flow paths B1, B2, B3, B4 is blocked, so that the fluid transferred by the traction hydraulic pumps P1, P2 flows through the arranged traction hydraulic motors M1, M2, M3, M4, respectively, and each of these traction hydraulic motors M1, M2, M3, M4 generates a part of the total drive torque. At this time, for example, the two traction hydraulic pumps P1, P2 can be configured as fixed displacement pumps, and the traction hydraulic motors M1, M2, M3, M4 can be configured as fixed displacement motors. The change in the running state is brought about by correspondingly controlling the electric drive motors E1, E2 in order to change the rotational speeds of the electric drive motors E1, E2, and thus the rotational speeds or discharge amounts of the traction hydraulic pumps P1, P2.

[0038] For example, when the earthmoving machine 10 is switched to the high-pressure drive state when moving between two construction sites, for example, the operations of the traction hydraulic motors M3 and M4 arranged on the drive rolls 14 can be stopped. For this purpose, the switching valve units S3 and S4 arranged on the traction hydraulic motors are placed in their high-pressure drive state switching positions, and in the high-pressure drive state switching positions, the switching valve units S3 and S4 open the bypass flow paths B3 and B4 arranged respectively for fluid to flow through. At the same time, it is possible to set the drive of the traction hydraulic pump P2 so that fluid is not transferred through the fluid circuit K2 by the traction hydraulic pump P2. The traction hydraulic motors M3 and M4 are short-circuited through the bypass flow paths that are open to the through-flow and arranged on the traction hydraulic motors respectively, so that the traction hydraulic motors rotate together when the drive rolls 14 roll, and fluid can be circulated through the bypass flow path B3 or B4 that forms a short circuit of the flow. Alternatively, even in this state, it is also possible to further operate the traction hydraulic pump P2 in order to eliminate the blockage of the traction hydraulic motors M3 and M4 and the possibility that the drive rolls 14 are dragged on the ground thereby.

[0039] In this high-pressure drive state of the electro-hydraulic drive system 24, the total drive torque is generated by the traction hydraulic motors M1 and M2 of the traction hydraulic circuit K1 supplied by the traction hydraulic pump P1. The higher fluid pressure required for this in the traction hydraulic circuit K1 is generated by the corresponding higher driving force of the electric drive motor E1. In this state, due to the fact that the traction hydraulic circuit K1 operates at a fluid pressure corresponding to approximately twice the fluid pressure in the basic drive state, the traction hydraulic motors M1 and M2 clearly operate with higher efficiency, which excessively compensates for the energy loss caused by the circulation of fluid by the traction hydraulic motors M3 and M4 being towed.

[0040] For example, in order to be able to generate sufficient braking torque when driving downhill, when shifting from the high-pressure driving state to the braking state, the traction hydraulic circuit K2 of the drive roll 14 that is not currently being driven can be operated again. For this purpose, the switching valve units S3, S4 are switched to their basic drive state switching positions, so that in the braking state, braking torque is generated by the traction hydraulic motors M3, M4 or the traction hydraulic pump P1 driven by the drive roll 14, and the braking torque can also be used, for example, to feedback electrical energy through the electric drive motor E2 operating as a generator.

[0041] In the electro-hydraulic drive system 24 shown in FIG. 3, different structural variants or operational variants may be provided. In the high-pressure drive state described above, in order to generate driving torque, one drive roll, or in some cases, segments of drive rolls or earthworking rollers that are rotatable around the same axis of rotation are used, but it is also possible to distribute the driving torque to the two drive rolls 12, 14. For this purpose, in the traction hydraulic circuits K1, K2, it is necessary to arrange each traction hydraulic motor on one of the two drive rolls and arrange the traction hydraulic motor on the other drive roll. For example, the traction hydraulic motors M1, M4 may be arranged in the traction hydraulic circuit K1, and the traction hydraulic motors M2, M3 may be arranged in the traction hydraulic circuit K2. In the high-pressure drive state, one of the traction hydraulic motors acting on one side of the axis of rotation can generate driving torque, while the other traction hydraulic motor arranged on the same axis of rotation is towed. Such an arrangement is particularly advantageous when the drive rolls 12, 14 are not divided and are configured as earthworking rollers having their own rigidity. However, basically, it is also possible to work with drive rolls 12, 14 that are segmented and have a driving action divided into segments arranged on different axes of rotation.

[0042] In the earthmoving machine 10 shown in FIG. 3 or the electro-hydraulic drive system 24 shown in FIG. 3, for example, only one of the two traction hydraulic circuits K1, K2 may be switchable between a basic drive state and a high-pressure drive state, and the other traction hydraulic circuit is used to generate drive torque even in the high-pressure drive state of the electro-hydraulic drive system 24. Further, the traction hydraulic circuits K1, K2 may be configured with respect to the valve assembly 26 such that the valve assembly 26 is disposed in traction hydraulic motors M1, M2 or M3, M4 connected in parallel in pairs with each other, and includes only one bypass flow path used together by the respective traction hydraulic motors, and thus a single switching valve unit.

[0043] An alternative embodiment of the electro-hydraulic drive system 24 is shown in FIG. 4. This electro-hydraulic drive system 24 includes only a single traction hydraulic circuit K1 having a single traction hydraulic pump P1 and an electric drive motor E1 disposed in the traction hydraulic pump. The four traction hydraulic motors M1, M2, M3, M4 are divided into two groups G1, G2. Group G1 includes traction hydraulic motors M1, M2, and group G2 includes traction hydraulic motors M3, M4. In each of the groups G1, G2, the traction hydraulic motors M1, M2 or M3, M4 are connected in parallel with each other, and the two groups G1, G2 are supplied with fluid in parallel with each other by the traction hydraulic pump P1.

[0044] Switching valve units S1, S2, S3, S4 are provided in bypass flow paths B1, B2, B3, B4 disposed in each of the traction hydraulic motors M1, M2 or M3, M4 and parallel to the traction hydraulic motors. Here too, only one jointly used bypass flow path having a single switching valve unit may be provided, disposed in the traction hydraulic motors M1, M2 or M3, M4 provided in pairs in the groups G1, G2 respectively.

[0045] The valve assembly 26 further includes two shut-off valve units V1, V2 or V3, V4 disposed in each of the two groups G1, G2. The shut-off valve units V1, V2, V3, V4, which are also configured as proportional valves for example, are arranged on both sides of a pair of traction hydraulic motors M1, M2 or M3, M4 disposed in the flow direction, and are under the control of the control unit 28 shown in FIG. 3, similar to the switching valve units S1, S2, S3, S4.

[0046] In the basic drive state, the shut-off valve units V1, V2, V3, V4 are in the basic drive state switching positions shown in FIG. 4. In the basic drive state switching positions, the supply of fluid to all the traction hydraulic motors M1, M2, M3, M4 is enabled. The switching valve units S1, S2, S3, S4 are also in the basic drive state switching positions, and thus the bypass flow paths B1, B2, B3, B4 are closed.

[0047] When a transition to the high-pressure drive state is made, for example, when the traction hydraulic motors M1, M2 of group G1 are used to generate a driving torque, the shut-off valve units V1, V2 and the switching valve units S1, S2 disposed in the traction hydraulic motors remain in the basic drive state switching positions. The shut-off valve units V3, V4 and the switching valve units S3, S4 disposed in the traction hydraulic motors M3, M4 of group G2 are switched to the high-pressure drive state switching positions. In the high-pressure drive state switching positions, on the one hand, the supply of fluid to the traction hydraulic motors M3, M4 by the shut-off valve units V3, V4 is blocked, and on the other hand, the bypass flow paths B3, B4 are opened for through-flow by the switching valve units S3, S4 provided in the bypass flow paths B3, B4 respectively. Next, the traction hydraulic motors M3, M4 are pulled by the drive rolls disposed in the traction hydraulic motors, and the fluid can be circulated through the respectively disposed bypass flow paths B3, B4.

[0048] In this embodiment of the electro-hydraulic drive system 24, in the high-pressure drive state, by selecting the arrangement of the different traction hydraulic motors M1, M2, M3, M4 in the two groups G1, G2, the drive torque can be transmitted to one drive roll or two segments rotatable around the same axis of the drive roll, while no drive torque is generated on the other axis, or a part of each of the drive torques can be generated on each of the two axes, for example, on a segmented drive roll or a drive roll having its own rigidity.

[0049] A further embodiment of the electro-hydraulic drive system 24 is shown in FIG. 5. This electro-hydraulic drive system 24 also includes only a single traction hydraulic circuit K1 with a single traction hydraulic pump P1. The four traction hydraulic motors M1, M2, M3, M4 are connected in parallel to each other and fluid is supplied in parallel by the traction hydraulic pump P1.

[0050] The valve assembly 26 is arranged on each of the traction hydraulic motors M1, M2, M3, M4 or on the bypass flow paths B1, B2, B3, B4, and two switching valve units S located on both sides of the traction hydraulic motors M1, M2, M3, M4 arranged in the flow direction respectively 11 , S 12 , S 21 , S 22 , S 31 , S 32 , S 41 , S 42 are included. The switching valve units S shown in FIG. 5 11 , S 12 , S 21 , S 22 , S 31 , S 32 , S 41 , S 42In the basic drive state switching position, since the bypass flow paths B1, B2, B3, B4 that cooperate with the switching valve unit are blocked with respect to the through-flow, the fluid connection portions 30, 32 of the traction hydraulic motors M1, M2, M3, M4 are opened to receive the fluid transferred by the traction hydraulic pump P1 or to discharge the fluid in the direction of the traction hydraulic pump P1.

[0051] When shifting to the high-pressure drive state, in at least one of the traction hydraulic motors M1, M2, M3, M4, the switching valve unit S 11 、S 12 or S 21 、S 22 or S 31 、S 32 or S 41 、S 42 The arranged pair can be brought to the high-pressure drive state switching position. In the high-pressure drive state switching position, the fluid connection portions 30, 32 of the arranged traction hydraulic motors M1, M2, M3, M4 are disconnected from the traction hydraulic pump P1 or the traction hydraulic circuit K1, and are connected to the arranged bypass flow paths B1, B2, B3, B4. Each of the traction hydraulic motors M1, M2, M3, M4 that is not used for generating drive torque in the high-pressure drive state can circulate the fluid through the arranged bypass flow paths B1, B2, B3, B4.

[0052] In the embodiment shown in FIG. 5, since each of the traction hydraulic motors M1, M2, M3, M4 can be optionally used to generate drive torque or its operation can be stopped, in the high-pressure drive state, for example, only a single traction hydraulic motor is used to drive the earthmoving machine 10, or, if necessary, three of the four traction hydraulic motors can be used to generate drive torque.

[0053] In this embodiment, while the earthmoving machine 10 is moving forward, it is possible to switch between different driving states, and when the earthmoving machine 10 is operating in the high-pressure driving state, a switching valve unit S is provided to enable the connection of the traction hydraulic motor in order to generate braking torque. 11 S 12 S 21 S 22 S 31 S 32 S 41 S 42 S may be configured as a proportional valve that enables a smooth transition to avoid switching surges when switching between different switching states.

[0054] Furthermore, it should be pointed out that the present invention is also applicable to an electro-hydraulic drive system for an earthmoving machine having only two traction hydraulic motors respectively disposed on, for example, two non-segmented earthmoving rollers. In the high-pressure driving state, fluid is supplied to only one of the two traction hydraulic motors at the corresponding high pressure, and no fluid is supplied to the other traction hydraulic motor.

Explanation of Reference Numerals

[0055] 10 Earthmoving machine 12, 14, 16, 18, 20, 22 Driving rollers 12a, 12b, 14a, 14b Segments 24 Electro-hydraulic drive system 26 Valve assembly 28 Control unit 30, 32 Fluid connection parts B1, B2, B3, B4 Bypass flow paths D1 First rotating shaft D2 Second rotating shaft E1, E2 Electric drive motors G1, G2 Groups K1, K2 Traction hydraulic circuits M1, M2, M3, M4 Traction hydraulic motors P1, P2 Traction hydraulic pumps S1, S2, S3, S4, S 11 S12 , S 21 , S 22 , S 31 , S 32 , S 41 , S 42 Switching valve unit V1, V2, V3, V4 shut-off valve unit

Claims

1. 1. An electro-hydraulic drive system for an earth moving machine having at least one drive roll, comprising: - A drive motor (E １ , E ２ At least one traction hydraulic pump (P １ , P ２ )and, at least one said traction hydraulic pump (P １ , P ２ At least two traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ )and, - a valve assembly (26), - in the basic operating state of the electrohydraulic drive system (24), the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) each of which is provided with at least one traction hydraulic pump (P １ , P ２ ) is supplied with hydraulic fluid from at least one of the traction hydraulic motors (M) so as not to generate a driving torque in a high pressure driving state of the electrohydraulic drive system (24). １ , M. ２ , M. ３ , M. ４ ) from at least one of the traction hydraulic pumps (P １ , P ２ a control unit (28) for operating the valve assembly (26) so that hydraulic fluid is supplied; An electro-hydraulic drive system including:

2. At least one said traction hydraulic pump (P １ , P ２ At least two of said traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ At least one hydraulic circuit (K １ , K ２ ) and the valve assembly (26) is provided with at least one traction hydraulic circuit (K １ , K ２ At least two of said traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ ) and at least one switching valve unit (S １ , S ２ , S ３ , S ４ 2. The electrohydraulic drive system of claim 1, further comprising:

3. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ At least one of the switching valve units (S １ , S ２ , S ３ , S ４ When the traction hydraulic motor (M) is switched to the basic drive state switching position, １ , M. ２ , M. ３ , M. ４ ) includes at least one traction hydraulic pump (P １ , P ２ ) is supplied to generate a driving torque, and then the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ At least one of the switching valve units (S １ , S ２ , S ３ , S ４ When the traction hydraulic motor (M) is switched to the high pressure drive state switching position, １ , M. ２ , M. ３ , M. ４ ) and a bypass flow path (B １ , B ２ , B ３ , B ４ ) is open for flow through, or / and said traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ 3. An electrohydraulic drive system according to claim 2, characterized in that a flow short circuit is created between the two fluid connections (30, 32) of said first and second hydraulic connections (32, 34).

4. At least two traction hydraulic circuits (K １ , K ２ ) is provided, and the traction hydraulic circuit (K １ , K ２ ) each of the traction hydraulic pumps (P １ , P ２ ), and the traction hydraulic pump (P １ , P ２ At least two of said traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ 4. The electrohydraulic drive system according to claim 2 or 3, further comprising:

5. The traction hydraulic pump (P １ , P ２ ) each with an electric drive motor (E １ , E ２ 5. The electrohydraulic drive system according to claim 4, further comprising:

6. A valve assembly (26) is provided in the traction hydraulic circuit (K １ , K ２ ) each of which is a traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) and a bypass flow path (B) parallel to the traction hydraulic motor at the basic drive state switching position. １ , B ２ , B ３ , B ４ ) in the high pressure drive state switching position and opens for through-flow in the high pressure drive state switching position. １ , S ２ , S ３ , S ４ 6. An electrohydraulic drive system according to claim 4 or 5, when dependent on claim 3, characterized in that it comprises a

7. At least one traction hydraulic circuit (K １ ) is provided, and at least one of said traction hydraulic circuits (K １ ) is equipped with a traction hydraulic pump (P １ ), and the traction hydraulic pump (P １ At least two, preferably at least four of said traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ 4. The electrohydraulic drive system according to claim 2 or 3, further comprising:

8. A valve assembly (26) is provided for the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) and a bypass flow path (B) parallel to the traction hydraulic motor at the basic drive state switching position. １ , B ２ , B ３ , B ４ ) in the high pressure drive state switching position and opens for through-flow in the high pressure drive state switching position. １ , S ２ , S ３ , S ４ 8. The electrohydraulic drive system according to claim 7, when dependent on claim 3, further comprising:

9. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) are the traction hydraulic pumps (P １ At least two of said traction hydraulic motors (M １ , M. ２ , M. ３ , M. ４ The traction hydraulic pump (P １ At least two traction hydraulic motor groups (G １ , G ２ ), and the valve assembly (26) forms the traction hydraulic motor group (G １ , G ２ ) are provided in each of the traction hydraulic pumps (P １ ) for the supply of hydraulic fluid conveyed by the traction hydraulic motor group (G １ , G ２ ) is selectively shut off, and the traction hydraulic pump (P １ ) for the supply of hydraulic fluid conveyed by the traction hydraulic motor group (G １ , G ２ At least one shutoff valve unit (V １ , V ２ , V ３ , V ４ 9. An electrohydraulic drive system according to claim 7 or 8, characterized in that it comprises a

10. The valve assembly (26) is connected to the traction hydraulic motor group (G １ , G ２ ) are arranged in the direction of flow of the fluid, １ , G ２ Two shutoff valve units (S １ , S ２ , S ３ , S ４ 10. The electrohydraulic drive system of claim 9, further comprising:

11. A valve assembly (26) is provided for the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) are provided in each of the two switching valve units (S １１ , S １２ , S ２１ , S ２２ , S ３１ , S ３２ , S ４１ , S ４２ ), and the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ The switching valve units (S １１ , S １２ , S ２１ , S ２２ , S ３１ , S ３２ , S ４１ , S ４２ ) at the basic drive state switching position, the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) to the traction hydraulic pump (P'), and in the high pressure drive state switching position, a bypass flow path (B １ , B ２ , B ３ , B ４ ) to the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ 8. An electrohydraulic drive system according to claim 7, when dependent on claim 3, characterized in that the fluid connections (30, 32) of the first and second hydraulic circuits (10, 12) are opened to create a flow short circuit between the first and second hydraulic circuits (10, 12).

12. 12. An electrohydraulic drive system according to any one of claims 2 to 11, characterised in that at least one changeover valve unit, preferably each changeover valve unit, comprises a proportional valve.

13. 13. An earthmoving machine, preferably a soil compactor, comprising a plurality of drive rolls (12, 14; 12, 16, 18, 20, 22) and an electrohydraulic drive system (24) according to any one of claims 1 to 12.

14. 14. An earthmoving machine according to claim 13, characterized in that at least one drive roll (12, 14) comprises an earthmoving roller or / and at least one drive roll (16, 18, 20, 22) comprises at least one wheel.

15. A method for operating an earthmoving machine as claimed in claim 13 or 14 in conjunction with claim 3, comprising the steps of: - In the high pressure drive state, the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) in the first portion, the switching valve unit (S １ , S ２ , S ３ , S ４ ) to the high-voltage drive state switching position; - when the electrohydraulic drive system (24) transitions from a high-pressure drive state to a braking state, said traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ The first part of the switching valve unit (S １ , S ２ , S ３ , S ４ ) at least a part of, preferably all of, the basic drive state switching positions; The method includes at least one of the steps.

16. In the high pressure driving state, the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) in the second portion of the switching valve unit (S １ , S ２ , S ３ , S ４ 16. The method according to claim 15, characterized in that the basic drive state switching position is switched to the basic drive state switching position.

17. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the earth moving machine (10) １ , M. ２ , M. ３ , M. ４ 17. The method of claim 15 or 16, characterized in that it comprises half of the total amount of the sieve.

18. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the first part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is the first rotation axis (D １ 18. The method according to claim 15, wherein the driving roller is arranged on at least one first drive roll (12) of the earth-moving machine (10) which is rotatable about a center axis of the driving roller (12).

19. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the second part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is the second rotation axis (D ２ 19. The method according to claim 18, characterized in that the at least one second drive roll (14; 16, 18, 20, 22) of the earth-moving machine (10) is arranged to be rotatable about the at least one second drive roll (14; 16, 18, 20, 22) of the earth-moving machine (10).

20. The traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the first part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is a part of the first rotation axis (D １ ) of the earth moving machine (10), the at least one first drive roll (12) of the earth moving machine (10) being rotatable around the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the second part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is a part of the first rotation axis (D ４ or / and the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the first part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is a part of the second rotation axis (D ２ ) of the earth moving machine (10), the at least one second drive roll (14; 16, 18, 20, 22) of which is rotatable around said traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) of the second part of the traction hydraulic motor (M １ , M. ２ , M. ３ , M. ４ ) is a part of the second rotation axis (D ２ 18. The method according to claim 16 or 17, when dependent on claim 16, characterized in that the at least one second drive roll (14; 16, 18, 20, 22) of the earth-moving machine (10) is arranged rotatable around the at least one second drive roll (14; 16, 18, 20, 22) of the earth-moving machine (10).

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