Working machine with an attachment, in particular a diaphragm wall cutter, and attachment, in particular a diaphragm wall cutter

Abstract

Working machine, preferably mobile working machine, with an attachment, in particular a trench cutter, wherein the attachment comprises at least two adjustable hydraulic motors for driving independent, individually controllable loads, wherein the hydraulic supply of the adjustable hydraulic motors is provided by a hydraulic drive unit arranged externally to the attachment, in particular by a drive unit of the working machine, characterized in that the at least two adjustable hydraulic motors of the attachment are connected to a common constant pressure network provided by the hydraulic drive unit and operate with an identical supply pressure.

Description

[0001] The invention relates to a work machine with an attachment, in particular a trench cutter, wherein the attachment comprises at least two adjustable hydraulic motors for driving independent, individually controllable loads, wherein the hydraulic supply of the hydraulic motors is provided by a hydraulic drive unit arranged externally to the attachment, in particular by a hydraulic drive unit of the work machine.

[0002] Certain construction machines can be flexibly equipped with various attachments, depending on the application, particularly in the field of specialized foundation engineering. Examples of different attachments include vibrators, auger drives, or trench cutters. The latter is used to excavate trenches in the ground to construct a concrete wall. The preferred work machine is a mobile machine, such as an excavator, preferably a rope excavator, which carries the trench cutter via its boom or excavator arm and controls it accordingly. Other suitable work machines include specialized foundation engineering machines or cranes.

[0003] A well-known excavation method using a so-called diaphragm wall cutter is in the Fig. 1 is shown schematically. The milled trench 1 is filled with a support fluid 2 during its creation, and the excavation tool in the form of the trench cutter is lowered into it. The primary function of the filled support fluid 2 is to prevent the resulting wall from collapsing and thus maintain the desired geometry of the trench 1. Common trench cutters, as shown in Fig. 1, comprise a guide frame 3, to the lower end of which one or more driven cutting wheels 4 are mounted. Additionally, the trench cutter may include one or more pumps 5 to convey the excavated material to the surface. The cutter is attached to a suitable working machine, such as a cable excavator, and is supplied with power via hydraulic supply lines from a drive unit of the working machine or cable excavator located above ground.

[0004] During milling operation, the milling wheels 4 loosen and crush the excavated material (sand, earth, gravel, rock, etc.) and mix it with the supporting fluid 2 introduced into the trench 1. The resulting mixture is fed to the intake opening 6 of the pump 5 and pumped above ground for further processing. The individual drives of known milling systems are usually hydraulically operated. Examples of known hydraulic circuits for driving the hydraulic motors of the trench wall cutter are the Fig. 2a, Fig. 2b.

[0005] Hydraulic motors 10 with adjustable displacement are used as rotational drives for the cutting wheels 4 and the pump 5, allowing them to respond to different operating conditions by changing the achievable speed and drive torque. The power supply for the hydraulic motors 10 is provided by a drive unit 11, 12 of the implement. Fig. 2a, this can be an aggregate 11 with an open hydraulic circuit or according to Fig. 2b involves a unit 12 with a closed hydraulic circuit. Existing solutions provide for controlling the amount and direction of the oil flow from the drive unit 11, 12 to the consumer 10 by adjusting the flow rate using hydraulic components located above ground, particularly those that are part of the drive units 11, 12. Depending on the load, an individual operating pressure results for each individual consumer 10.

[0006] Depending on the load condition, very different operating pressures result at a given speed of the hydraulic drives 10. In the unit 11, the individually used pump 13 must always deliver the highest available pressure level. The pressure difference to the lower-load drives 10 must be reduced in the hydraulic control block 14, where it is generated as heat energy and cannot be further used. To improve the efficiency here, as in the exemplary embodiment of the Fig. 2b - several separate hydraulic circuits are used in the drive unit 12, advantageously with one pump 13a, 13b, 13c for each consumer 10.

[0007] Another disadvantage of previous solutions is that they require a large number of hydraulic lines between the attachment and the drive unit 11, 12. These are routed from the respective drive unit 11, 12 to the milling machine via a complex hose reel system 15. These hydraulic lines are independently subject to widely varying operating pressures. This constant variance in operating pressures leads to structural deformations and relative movements between the individual hydraulic lines, resulting in increased wear and damage, which requires complex technical measures.

[0008] In addition, the milling systems according to the Fig. 2a, Fig. 2b proposes that the control system 16 of the milling machine communicate with the control system 16, 17 of the drive unit 11, 12 in order to coordinate the power allocation by the drive unit 11, 12 and the setting of the consumers 10. This places increased demands on the compatibility of the control system 16, 17 of the drive unit 11, 12, since it must generally be compatible with a variety of attachments, which do not necessarily originate from the same manufacturer of the work machine.

[0009] DE 10 2007 046 696 A1 discloses a drive system for a crane operating a winch and a drive system for operating a travel drive. The hydraulic motor of the drive system can be supported by a high-pressure accumulator.

[0010] The object of the present invention is to improve the energy supply for an attachment with individually controllable drives, in particular by optimizing the achievable efficiency and, if necessary, simplifying the system.

[0011] This object is achieved by a work machine, in particular a mobile work machine according to the features of claim 1. Advantageous embodiments of the work machine are the subject of the claims following the main claim.

[0012] The starting point of the invention is a work machine, in particular a mobile work machine, preferably an excavator, particularly preferably a cable excavator, with an attachment. According to the invention, an attachment is understood to be a work tool that can be actuated with the work machine and that can be connected to the work machine in a detachable and thus interchangeable manner. In particular, the invention relates to attachments for special foundation engineering, such as vibrators, drilling drives, or trench wall cutters. The description of the invention is given below primarily with reference to the trench wall cutter; however, the invention can readily be applied to alternative attachments, in particular those that comprise at least two adjustable hydraulic motors for driving independent, individually controllable loads, such as one or more cutting wheels or one or more pumps.

[0013] The hydraulic supply to the adjustable hydraulic motors is ensured by a hydraulic drive unit which is not itself a component of the work tool. This can be either a drive unit of the work machine or an external drive unit which is neither a component of the attachment nor of the work machine. One example is a so-called external power pack. It is therefore crucial that the hydraulic energy supply to the attachment is not a component of the attachment itself. According to the invention, it is proposed that the energy supply to the at least two adjustable hydraulic motors is provided via a constant-pressure network. This means that - unlike the prior art - the present invention does not use separate hydraulic circuits to supply energy to the hydraulic motors of the attachment, but instead a common constant-pressure network is provided for the energy supply.This not only simplifies the hydraulic connection between the attachment and the work machine or external drive unit, but also reduces the control effort required by the hydraulic drive unit. Ideally, the synchronization effort between the hydraulic drive unit and the attachment is reduced as much as possible.

[0014] The constant-pressure network also has the advantage of avoiding pressure peaks that can occur with conventional attachments with variable-pressure power supplies. This also optimizes the service life of the affected hydraulic components.

[0015] Reversible variable displacement motors are preferred for variable displacement hydraulic motors. In particular, the displacement of the hydraulic motors is continuously adjustable, with a zero-crossing point explicitly provided. If a drive is to be operated in alternating directions of movement, the displacement can be continuously adjusted from a positive displacement through zero to a negative displacement.

[0016] Particularly preferably, the control system of the attachment is designed such that the speed control of the hydraulic motors used, in particular the reversible variable displacement motors, corresponds to a secondary control. In this case, the displacement of the respective hydraulic motor is varied until the motor torque is balanced with the respective load on the motor. The control objective can be a desired target speed and / or a defined temporal profile of the drive power and / or a corresponding target drive torque.

[0017] For control purposes, suitable sensors are particularly preferred on the attachment or the hydraulic connection. The sensors are particularly suitable for detecting the speed of the individual hydraulic motors and / or the set adjustment angle of the individual hydraulic motors. Furthermore, the sensors can detect the pressure level within the high-pressure line of the respective hydraulic motors and / or the return line (low-pressure line) of the individual hydraulic motors.

[0018] In brief, the invention proposes a hydraulic drive system in which power is controlled solely by adjusting the torque of the consumer (hydraulic motor). Assuming that the operating pressure of the constant-pressure network is maintained at a constant level, the speed of the consumers (hydraulic motors) and thus the delivery rate of the drive unit are a result of the adjustment, but not the actual control purpose. Previous solutions always provided power control by controlling the delivery rate, with the resulting variable operating pressure being a result of the external load. The result of the new control concept is a significantly lower flow rate through the oil lines in the partial load range, which correspondingly reduces energy losses in the system. Overall, the efficiency of the drive unit of the working machine is increased.Particularly with special attachments that require extremely long hydraulic connection lines between the working machine and the attachment, as is the case with trench cutters, the prior art solutions resulted in very high line losses, which account for a very high proportion of the total power output. The solution according to the invention achieves a significant increase in efficiency by minimizing the corresponding line losses.

[0019] In addition, the load-independent, constant pressure level (constant pressure system) noticeably reduces pressure fluctuations and the associated movement of the connecting lines. The solution places extremely simple requirements on the properties of the hydraulic energy source, thus ensuring great flexibility in its selection (carrier device, drive unit, combination of both, improvisation options in the event of a failure of the main unit).

[0020] The hydraulic drive unit advantageously comprises at least one adjustable hydraulic pump, the delivery volume of which can be adapted to the actual load requirement of the attachment, i.e. the load requirement of the respective hydraulic motors, via at least one device. In this way, unlike in the prior art, where the hydraulic pump is always operated at the maximum load requirement, the hydraulic pump can be optimally adapted to the total load requirement of the individual hydraulic consumers. This significantly optimizes the efficiency of the hydraulic drive unit. In particular, a corresponding pressure regulator is used as a device for adapting to the actual load requirement. This pressure regulator automatically increases the delivery volume of the pump when the operating pressure drops below a predefinable setpoint and reduces the delivery volume of the pump when the definable setpoint is reached or exceeded.

[0021] Overall, the constant-pressure system, meaning all hydraulic motors of the attachment operate at an identical feed pressure, significantly simplifies the hydraulic supply. This means that the number of required hydraulic connecting lines between the hydraulic drive unit and the attachment can be reduced, in particular to a single common high-pressure line for the at least two hydraulic motors of the drive unit. The same preferably applies to the return line (low-pressure line) and a possible leakage oil line. Overall, the hydraulic coupling between the drive unit and the attachment can be reduced to a minimum of three hydraulic lines.

[0022] The corresponding control of the attachment's hydraulic motors also eliminates the need for a communication interface between the attachment's control component and the drive unit's control component. This reduces the required control effort and enables a more flexible drive unit design. Of course, it is not impossible for both control components to communicate with each other, but this is not a mandatory requirement for basic functionality.

[0023] It is particularly preferred if the attachment is designed in the form of a milling machine, with at least one milling wheel being driven by an adjustable hydraulic motor of the attachment. Ideally, at least two milling wheels are provided, which can be driven by separate adjustable hydraulic motors. Furthermore, at least one pump, in particular a bentonite pump, can be provided for introducing a supporting fluid, with the bentonite pump also being driven by a separate adjustable hydraulic motor.

[0024] In addition to the mobile work machine, the present invention also relates to an attachment, in particular a trench cutter, for a hydraulic work machine, in particular according to the present invention, wherein the attachment comprises at least two adjustable hydraulic motors for driving independent, individually controllable loads. According to the invention, the attachment has a common high-pressure connection for the adjustable hydraulic motors, so that they can be supplied with hydraulic energy via a common constant-pressure network.

[0025] The adjustable hydraulic motors are preferably reversible. The adjustable hydraulic motors are ideally controlled by secondary control. At the same time, a common low-pressure connection or a common leakage oil connection can be provided for the hydraulic motors, thus reducing the required number of connecting lines between the attachment and an external hydraulic drive unit for power supply to a minimum, ideally to exactly three lines.

[0026] The attachment can preferably have at least one cutting wheel driven by a separate hydraulic motor. Ideally, at least two cutting wheels driven by separate hydraulic motors are provided. Furthermore, a pump can be provided, in particular a bentonite pump driven by another separate hydraulic motor.

[0027] The attachment can preferably also be a vibrator, drill drive or other special tool for civil engineering.

[0028] Further advantages and features of the invention will be explained below with reference to an exemplary embodiment illustrated in the drawings. They show: Fig. 1: a schematic representation of a known trench cutter; Fig. 2: different examples of hydraulic supply for a conventional trench cutter; Fig. 3: different embodiments of a representation of a hydraulic circuit for supplying energy to a trench cutter according to the present invention.

[0029] Fig. Figure 3 shows two embodiments of the hydraulic system according to the invention, comprising a trench cutter and a drive unit of the working machine. The exact number of hydraulic drives of the attachment is irrelevant for the invention. According to the invention, the drive unit 20, 21 of the working machine can be designed as a drive unit 20 with an open hydraulic circuit (see Figure 2). Fig. 3a) or as drive unit 21 with closed hydraulic system (see Fig. 3b). The design as an open or closed hydraulic circuit and the resulting design of the adjustable pump 22 is the only difference between the two embodiments of the Fig. 3a, Fig. 3b. The trench cutter and the hydraulic connection 25 are identical for both versions. The following explanations therefore refer to both examples.

[0030] At least one hydraulic pump 22 with adjustable delivery volume, powered by a primary energy source, is equipped with a device 23 that adjusts the delivery volume to the actual requirements of the trench cutter being fed. In an advantageous embodiment, this is a pressure regulator 23. If the operating pressure drops below a set target value, the regulator 23 increases the delivery volume and thus the oil flow of the pump 22. If the target value is reached or even exceeded, the pressure regulator 23 reduces the delivery volume of the pump 22 to a value sufficient to maintain the target pressure.

[0031] The hydraulic oil flows through the high-pressure line 24 through the hose system 25 to the hydraulic drives 31 of the bentonite pump 26, the right-hand cutting wheel 27, and the left-hand cutting wheel 28 of the trench wall cutter. Theoretically, this could supply power to additional hydraulic consumers as part of the cutter.

[0032] The provided pressure energy is converted into mechanical energy in these drives 31. The oil is fed back to the drive unit 20, 21 through a common return line 29 of the hydraulic motors 31 via the hose system 25. The leakage oil resulting from the volumetric efficiency of the hydraulic drives 31 is also returned to the unit 20, 21 via the common leakage oil line 30.

[0033] According to the invention, each individual consumer is equipped with a hydraulic motor 31 with continuously adjustable displacement Vg. A characteristic of the invention is that the motors 31 a) a displacement volume Vg = 0 can be set, b) the displacement can be adjusted from -Vg via 0 to +Vg if a drive is to be operated with changing direction of movement. c) all drives involved can be connected to the same lines 24, 29, 30, thus reducing the complexity of the hose system 25.

[0034] If the displacement of the hydraulic motors 31 increases, the output torque of the respective motor 31 increases due to the constant operating pressure in the high-pressure line 24. The movement of the driven load, i.e., the respective cutting wheel 27, 28 or the pump 26, is accelerated. A reduction in the displacement causes a decrease in torque due to the constant operating pressure of the high-pressure line 24, and the movement of the respective driven load 26, 27, 28 is decelerated.

[0035] Furthermore, a sensor is provided to determine the current speed [rpm] of the hydraulic motor 31 and its adjustment angle [°]. In addition, the operating pressures [N / m 2 ] in lines 24 and 29 by an installed sensor.

[0036] The integrated electronic control unit 32 of the trench cutter can now control the hydraulic motors 31 appropriately based on these sensor-detected measured values, depending on the operating requirements. Possible control objectives include, for example, a defined temporal progression of the drive power, a target speed, or a target drive torque of the respective hydraulic motor 31.

[0037] Since the drive units 20, 21 - unlike in the prior art - are supplied by a constant pressure network, any throttle points for power regulation can be dispensed with. The system shown of the Fig. 3a, Fig. 3b, in contrast to existing solutions, only three hydraulic lines can be installed to connect the working machine with the trench cutter. The actual operating pressures of the system depend on its control quality. Pressure fluctuations due to changing external loads occur, in contrast to conventional systems, according to the Fig. 2a, Fig. 2b into the background. This results in smoother pressure changes in lines 24, 29, and 30.

[0038] Finally, the system shown is the Fig. 3a, Fig. 3b without electronically processed information about the operating states of the cutter drives 31. Communication between the control system 32 of the trench wall cutter and any control system of the drive unit 20, 21 is possible, but not absolutely necessary.

Claims

[1] A working machine, preferably a mobile working machine, with an attachment, in particular a trench cutter, wherein the attachment comprises at least two adjustable hydraulic motors for driving independent, individually controllable loads, wherein the hydraulic supply of the adjustable hydraulic motors is effected by a hydraulic drive unit arranged externally to the attachment, in particular by a drive unit of the working machine, characterized by that the at least two adjustable hydraulic motors of the attachment are connected to a common constant pressure network provided by the hydraulic drive unit and operate with an identical feed pressure. [2] Working machine according to claim 1, characterized by that at least two adjustable hydraulic motors are reversible. [3] Working machine according to claim 1 or 2, characterized bythat the at least two adjustable hydraulic motors are secondary controlled by means of a control system in that the displacement of the motor is changed until there is a balance between the motor torque and the respective load on the motor and at the same time the target speed and / or a defined time profile of the drive power and / or a target drive torque is reached. [4] Working machine according to claim 3, characterized by that a sensor system is provided to detect the speed and / or the adjustment angle of the individual hydraulic motors and / or the operating pressures in the high-pressure and / or return line and that the secondary control takes place taking these measured values ​​into account. [5] Working machine according to one of the preceding claims, characterized bythat the hydraulic drive unit comprises at least one adjustable hydraulic pump, the delivery volume of which can be adapted to the load requirement of the attachment via at least one device. [6] Working machine according to claim 5, characterized by that the device is a pressure regulator which increases the pump delivery volume when the operating pressure falls below an adjustable setpoint and reduces the pump delivery volume when the adjustable setpoint is reached or exceeded. [7] Working machine according to one of the preceding claims, characterized by that the hydraulic connection between the hydraulic drive unit and the attachment comprises a common high-pressure line for the at least two hydraulic motors of the attachment, wherein preferably a common return line and / or leakage oil line is provided from the hydraulic motors to the hydraulic drive unit. [8] Working machine according to one of the preceding claims, characterized by that no communication interface is required between the control of the hydraulic motors and a control of the hydraulic drive unit, in particular is provided. [9] Working machine according to one of the preceding claims, characterized by that one cutting wheel is driven by a hydraulic motor, preferably at least two cutting wheels are each driven by a hydraulic motor, and at least one pump, in particular a bentonite pump, is driven by a hydraulic motor. [10] Attachment, in particular trench wall cutter, for a hydraulic working machine, in particular according to one of the preceding claims, with at least two adjustable hydraulic motors for driving independent, individually controllable loads, characterized by that the attachment has a common high-pressure connection for the adjustable hydraulic motors. [11] Attachment according to claim 10, characterized bythat at least two adjustable hydraulic motors are reversible. [12] Attachment according to claim 10 or 11, characterized by that a control system is provided for secondary control of the adjustable hydraulic motors. [13] Attachment according to one of claims 10 to 12, characterized by that a common low-pressure connection and / or tank return connection is provided for the adjustable hydraulic motors. [14] Attachment according to one of claims 10 to 13, characterized by that one cutting wheel is driven by an adjustable hydraulic motor, preferably at least two cutting wheels are each driven by an adjustable hydraulic motor, and at least one pump, in particular a bentonite pump, is driven by a further adjustable hydraulic motor.

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