Earthmoving machine and method for operating an earthmoving machine

Abstract

To provide an earthmoving machine capable of operating a hydraulic steering system while reducing energy consumption and a method for operating the earthmoving machine.SOLUTION: An earthmoving machine such as a soil compactor includes a hydraulic steering system (30) including at least one steering mechanism (26) operated by pressure fluid and an electrohydraulic pressure fluid source (36) including at least one steering pressure fluid pump (40) capable of being driven by at least one electromotor (38) for supplying the pressure fluid to a steering pressure fluid circuit (34).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an earthmoving machine, such as a soil compactor, which may be used to compact a ground overlay material, such as asphalt, soil or gravel. The present invention further relates to a method for operating the earthmoving machine. [Background technology]

[0002] An example of such an earth moving machine configured as a soil compactor is shown in FIG. 1. The earth moving machine 10 configured as a soil compactor is configured to have a rear vehicle part 12 and a front vehicle part 14 connected to the rear vehicle part 12 so as to be pivotable about a substantially vertical steering axis. The rear vehicle part 12 is provided with drive wheels 16 which can be driven to rotate in order to move the soil compactor 10 over the ground surface 18 to be compacted. The front vehicle part 14 is rotatably mounted with an earth moving roller 20 configured as a compaction roller. In the configuration of the soil compactor shown in FIG. 1, for example, the earth moving roller 20 may also be driven to rotate. Alternatively, the earth moving roller 20 rolls on the ground surface 18 only by being driven forward by the drive wheels 16. For example, in the case of a soil compactor in which the rear vehicle part 12 is also provided with a compaction roller, one or both of the compaction rollers may be driven to rotate in order to move the soil compactor over the ground surface 18.

[0003] An operation console 22 is further provided in the rear vehicle section 12, and within the operation console 22, an operator can sit in an operator seat 24 to operate the soil compactor. The operation console 22 is further provided with various operation mechanisms, which will be described later, and an operator sitting in the operator seat 24 at the operation console 22 can operate the soil compactor through the operation mechanisms. Generally, such a soil compactor has a drive unit configured as a diesel engine in the rear vehicle section 12. It is pointed out that in the present invention, the rear vehicle section 12 is considered to be a system area of ​​the soil compactor in which the drive unit and / or the operation console 22 are stored. When the soil compactor is configured as a pivot-steering tandem roller in which steering pivots, which rotatably support the earthworking rollers, are supported at both end regions of a frame region provided in the central region of the soil compactor and generally support a drive unit and an operating table, the centrally located region of the soil compactor which rotatably supports both steering pivots is considered to be the rear of the vehicle in the present invention.

[0004] The drive unit drives one or more hydraulic pumps to supply pressure fluid in the various hydraulic circuits. For example, a traction hydraulic circuit may be provided to move the soil compactor on the ground surface 18, through which pressure fluid may be supplied to a hydraulic motor arranged on the drive wheels 16. If the soil compactor has one or more compaction or earthwork rollers 20 that are driven to rotate, these compaction or earthwork rollers 20 may also be provided with a hydraulic motor to drive them to rotate. A further hydraulic circuit may be used to drive an unbalance device in the earthwork roller 20. The unbalance device, which may be configured to generate a rocking or / and oscillating movement of the earthwork roller 20, may also include one or more hydraulic motors to drive the unbalance mass to rotate. A further hydraulic circuit may be provided in the steering system. The pressure fluid present in the steering hydraulic circuit can be directed through a hydraulic steering unit to one or two steering piston / cylinder units 28 effective as steering mechanisms 26, depending on the steering movement of a steering mechanism, such as a steering wheel. The steering piston / cylinder units 28 cause the front vehicle 14 and the rear vehicle 12 to pivot relative to each other about a steering axis, thereby steering the soil compactor as it moves over the ground surface 18. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide an earth moving machine and a method for operating such an earth moving machine in which a hydraulic steering system can be operated with reduced energy consumption. [Means for solving the problem]

[0006] According to the present invention, the problem is solved by an earthmoving machine, in particular a soil compactor, comprising a hydraulic steering system having at least one steering mechanism operated by pressure fluid and an electrohydraulic pressure fluid source with at least one steering pressure fluid pump, which can be driven by at least one electric motor, for supplying pressure fluid to a steering pressure fluid circuit.

[0007] In an earthmoving machine constructed according to the invention, the energy for operating the hydraulic steering system is provided by an electric motor, which is supplied, for example, by a battery. Such an electric motor as drive for the steering pressure fluid pump has the advantage, compared to the use of a diesel engine, that the electric motor can be adapted to the immediate demand for energy or pressure fluid, and that a spontaneous change in the speed of the electric motor provides the possibility of adapting the amount of pressure fluid transported to the changing demand. Such short-term changes cannot be realised with a diesel engine by changing the operating state of the diesel engine. However, the hydraulic steering system according to the invention offers the advantage, by including a steering hydraulic circuit, that, for example, emergency steering properties are maintained, such a hydraulic steering system has a particularly high stability against overloads or shocks, and provides the operator with mechanical feedback of the current steering state or steering movement.

[0008] An earth moving machine constructed according to the invention may include a rear vehicle section and a front vehicle section rotatable about a steering axis relative to the rear vehicle section, and at least one steering mechanism acting between the front vehicle section and the rear vehicle section includes a steering piston / cylinder unit. As already mentioned at the beginning, it is advantageous to provide two steering mechanisms, for example configured as steering piston / cylinder units, one or both of which may be configured to be double-acting, i.e. to act in both steering directions.

[0009] In order to convert an operation caused by an operator of a steering operating mechanism, i.e. for example a steering wheel, into a corresponding displacement movement of the steering mechanism, the hydraulic steering system may include a hydraulic steering unit which is supplied with pressure fluid from a steering pressure fluid circuit and which supplies pressure fluid to at least one steering mechanism depending on the operation of the steering operating mechanism.

[0010] The hydraulic steering system may include at least one steering sensor, which is configured to provide steering information representative of a steering state. For example, such a steering sensor detects the rotation of a steering shaft, and the steering information may represent a steering angle and / or a steering angle rate of change. In the present invention, it is pointed out that the steering angle rate of change represents the change in the steering angle over time, i.e. the change in the rotational position of the steering shaft over time, or the change in the angle between the front and rear of the earthmoving machine.

[0011] In order to support an operation adapted to the demands of the hydraulic steering system, it is proposed that the hydraulic steering system is configured to operate the electric motor of the electrohydraulic steering pressure fluid source at a speed that depends on the steering information.

[0012] To this end, for example, the hydraulic steering system may be configured to operate an electric motor of an electrohydraulic steering pressure fluid source at an increased rotational speed when the steering angle increases and / or to operate the electric motor at an increased rotational speed when the steering angle change rate increases.

[0013] For a demand-adapted and therefore energy-saving operation of the steering system, it is further proposed that the hydraulic steering system is arranged to operate the electric motor of the electrohydraulic steering pressure fluid source at a speed that depends on the state of the traction mode of the earthmoving machine, it being pointed out in the present invention that such a state of traction mode is characterized by conditions that are not directly related to a steering movement or that do not represent a steering movement as such.

[0014] For example, the traction mode conditions of an earthmoving machine may include the following conditions: - the traction control mechanism is in the parked position and / or the driver is not seated in the driver's seat; - a traction ready state in which the traction operating mechanism is set to the traction ready position; and - Traction state with the traction operating mechanism set to the traction position.

[0015] The hydraulic steering system must take into account what are considered to be the different traction mode conditions. In the parked state, the electric motor of the electrohydraulic steering pressure fluid source is deactivated, and / or In the traction ready state, the electric motor of the electrohydraulic steering pressure fluid source is operated at a base speed, or / and In a traction state, the electric motor of the electrohydraulic steering pressure fluid source may be configured to operate at an operating speed that is greater than the base speed.

[0016] In a structurally and control-technically simple configuration, the hydraulic steering system can be configured in such a way that the electric motor of the electrohydraulic steering pressure fluid source always operates at the operating speed in the traction state, meaning that whenever the earthmoving machine is in the traction state, the electric motor operates at the operating speed, i.e. at a speed above the base speed, regardless of whether it is steered, i.e. whether there is a change in the steering state.

[0017] In an alternative, particularly advantageous variant in terms of efficient energy use, the hydraulic steering system may be configured to operate the electric motor of the electrohydraulic steering pressure fluid source at the operating speed when entering a traction state and / or in a traction state, if the steering information indicates that a change in steering state is present. This means that during a traction state, in phases where energy must be consumed for a change in steering state, i.e. a change in steering angle, the increase in the speed of the electric motor may be limited. In phases where this is not necessary, i.e. where no steering is performed and therefore there is no change in steering angle, for example when going straight or cornering with a substantially constant curve radius, the electric motor may be operated at a lower speed, i.e. for example at a base speed and therefore with less energy use.

[0018] Energy-saving and more tailored operation to current demands can be supported by making the base speed dependent on the temperature of the hydraulic fluid in the steering hydraulic circuit and / or in the operational hydraulic system supplied from the steering hydraulic circuit, and / or by making the base speed dependent on the load demand in the operational hydraulic system supplied from the steering hydraulic circuit.

[0019] In an earthmoving machine constructed according to the invention, the operation of the hydraulic steering system adapted to the energy or pressure fluid demand is ensured in that the electric motor provided for driving the steering pressure fluid pump operates or is controlled at a speed adapted to the demand at hand. No measures are therefore required in the design of the steering hydraulic pump that would allow the delivery of the steering hydraulic pump to be adapted to the demand at hand; the steering hydraulic pump can therefore be a constant-delivery pump, with variations in the delivery of hydraulic fluid being brought about exclusively by variations in the speed of the pump or of the electric motor driving it.

[0020] In the case of the earth moving machine according to the invention, a hydraulic traction drive system may further be provided for moving the earth moving machine over the ground to be worked, the hydraulic traction drive system comprising at least one electric motor and an electrohydraulic pressure fluid source with at least one traction hydraulic pump for supplying pressure fluid to a traction hydraulic circuit, and at least one traction hydraulic motor supplied with pressure fluid from the traction hydraulic circuit. The hydraulic traction drive system is thus also an electrohydraulic system and offers the advantage that, like a steering system which also functions electrohydraulically, the operation of the electric motor of the hydraulic traction drive system can be adapted quickly or spontaneously to changes in or required changes in the operating conditions.

[0021] In a particularly advantageous manner, the hydraulic steering system and the hydraulic traction drive system contain electric motors that can operate independently of one another, meaning that each of these hydraulic systems is provided with an independent electric motor or with several independently functioning electric motors, the electric motor of the hydraulic steering system being not provided for supplying pressure fluid to the traction hydraulic motor or motors, while the electric motor of the hydraulic traction drive system is not provided for supplying pressure fluid to the hydraulic steering unit or to the steering mechanism or mechanisms, making it possible to operate each of these electrohydraulic systems independently of the other system, in order to optimally match the demands present in the respective system.

[0022] Regardless of the fact that the different hydraulic systems may be provided with independent electric motors that can be operated independently of one another, the hydraulic steering system may be configured to supply pressure fluid to the traction hydraulic circuit via the steering hydraulic circuit, making it possible, for example, to compensate for pressure fluid losses occurring in the traction hydraulic circuit or for a deliberately induced discharge of pressure fluid from the steering hydraulic circuit in the traction hydraulic circuit.

[0023] The hydraulic steering system may further be configured to pump the pressurized fluid through the steering hydraulic circuit back to the fluid tank, meaning that the hydraulic steering system or its steering hydraulic circuit may essentially be open circuit, allowing pumping back to the fluid tank to avoid overheating of the pressurized fluid present in the circuit.

[0024] The initially set out problem is further solved by a method for operating an earth moving machine, preferably configured according to the invention, which comprises a hydraulic steering system, which comprises at least one steering mechanism operated by pressure fluid, an electrohydraulic pressure fluid source with at least one steering pressure fluid pump which can be driven by at least one electric motor for supplying pressure fluid to a steering pressure fluid circuit, and at least one steering sensor, which provides steering information representative of a steering state, and the electric motor of the electrohydraulic steering pressure fluid source operates at a speed which depends on the steering information.

[0025] The method can include operating the electric motor of the electrohydraulic steering pressure fluid source at an increased rotational speed when the steering angle increases and / or operating the electric motor of the electrohydraulic steering pressure fluid source at an increased rotational speed when the steering angle rate of change increases.

[0026] In the following, the invention will be described in detail with the aid of the accompanying drawings, in which: [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a side view of an earthmoving machine configured as a soil compactor. [Diagram 2] FIG. 1 illustrates the principle of a hydraulic steering system and a hydraulic traction drive system for an earthmoving machine. [Diagram 3] 3 is a diagram showing the relationship between the steering angle change rate and the rotation speed of the electric motor of the electrohydraulic pressure fluid source of the hydraulic steering system according to FIG. 2; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Before the structure and function of the hydraulic steering system and the hydraulic traction drive system of the earthmoving machine are explained in detail below with the aid of Figure 2, it is pointed out that the system described below with reference to Figure 2 can also be used in an earthmoving machine 10 configured, for example, as a soil compactor, as shown in Figure 1. In principle, however, it is pointed out that the system described below with reference to Figure 2 can also be used in earthmoving machines of different constructions, for example earthmoving machines having earthmoving rollers at the front and rear of the vehicle.

[0029] 2 shows a hydraulic steering system generally designated by reference number 30. The hydraulic steering system 30 includes one or more steering mechanisms 26 configured as double-acting steering piston / cylinder units 28, which are connected to a steering pressure fluid circuit 34 through a hydraulic steering unit 32. The hydraulic steering system 30 includes an electrohydraulic pressure fluid source 36 with an electric motor 38 and a steering pressure fluid pump 40 driven by the electric motor 38. The electric motor 38 of the hydraulic steering system 30 is under the control of a control unit 42 and is supplied from a voltage source, for example a battery 44, to drive the steering pressure fluid pump 40. The application of voltage from the battery 44 to the electric motor 38 may be performed according to a corresponding control code from the control unit 42.

[0030] FIG. 2 further shows a hydraulic traction drive system, generally designated by reference numeral 46. The hydraulic traction drive system 46 includes a hydraulic pressure fluid source 48 having an electric motor 50 and a traction hydraulic pump 52 driven by the electric motor 50. The traction hydraulic pump 52 transports a fluid, for example hydraulic oil, in a traction hydraulic circuit 54, which supplies pressure fluid to two traction hydraulic motors 56, 58 incorporated in the traction hydraulic circuit 54. For example, both traction hydraulic motors 56, 58 may be arranged on two earthwork rollers provided in the soil compactor, so that either of these earthwork rollers can be driven to move the soil compactor. In the configuration of the earthwork machine shown in FIG. 1, one of both traction hydraulic motors 56, 58 may be arranged on one of both drive wheels 16, and the other of both traction hydraulic motors 56, 58 may be arranged on the other drive wheel 16. For example, in the case of an earthworking machine having an earthworking roller divided into two adjacent segments in the direction of the roller rotation axis, one of the traction hydraulic motors 56, 58 may be provided in each segment of the earthworking roller thus divided.

[0031] The hydraulic traction drive system 46 further includes a discharge valve device 60, through which fluid can be discharged from the hydraulic traction drive system 46 to a fluid tank 62. From this fluid tank 62, the steering hydraulic pump 40 discharges fluid into the steering hydraulic circuit 34, which is connected to the traction hydraulic circuit 54, as shown in FIG. 2, in such a way that the fluid, for example hydraulic oil, supplied as pressure fluid by the steering hydraulic pump 40 to the steering hydraulic circuit 34 can be introduced into the hydraulic traction drive system 46. This makes it possible to keep the amount of fluid present in the traction hydraulic circuit 54 approximately constant by supplying fluid from the steering hydraulic circuit 34, for example when fluid is discharged from the hydraulic traction drive system 46 to the fluid tank 62 through the discharge valve device 60. Fluid leaks that also occur in the traction hydraulic circuit 54 can be compensated for in this way.

[0032] The steering hydraulic circuit 34 further includes a return valve 64 through which fluid or pressurized fluid from the steering hydraulic circuit 34 may be returned to the fluid tank 62. The return valve 64 may be, for example, pressure controlled, whereby fluid may be sent to the fluid tank 62 if the fluid pressure in the steering hydraulic circuit 34 or in the traction hydraulic circuit 54 also exceeds a predetermined limit pressure. The return valve 64 thus functions as a pressure relief valve.

[0033] 2 further shows that one or more drive hydraulic systems 67 are connected to the steering hydraulic circuit 34, whereby the drive hydraulic systems 67 are supplied with pressurized fluid from the steering hydraulic circuit 34 or by the steering hydraulic pump 40. Such drive hydraulic systems 67 may be systems that operate, for example, when the traction hydraulic circuit 54 is inactive. For example, the parking brake of the earthmoving machine 10 may be such a drive hydraulic system 67, as may edge presses present in soil compactors used in compacting asphalt materials, which may be lifted or lowered even at a stationary soil compactor.

[0034] To steer an earth moving machine, for example the earth moving machine 10 shown in Fig. 1, a steering mechanism 66, generally configured as a handle, is provided. An operator seated at the operating platform 22 can steer the earth moving machine 10 moving over the ground surface 18 to be worked by operating the steering mechanism 66, i.e. by rotating the handle. In this regard, the steering movement of the steering mechanism 66 in the hydraulic steering unit 32 is translated into a corresponding supply of pressure fluid to one of the chambers of each steering piston / cylinder unit 28 and a corresponding discharge of pressure fluid from the other of both chambers of each steering piston / cylinder unit 28.

[0035] The operation of the steering mechanism 66 is detected by a steering sensor 68. The steering sensor 68 detects, for example, a rotational movement of a steering shaft connected to the steering mechanism 66 so as to rotate together, and can output a signal including information representative of a steering state to the control unit 42. The information can be, for example, information representative of a steering angle with respect to the current rotational position of the steering mechanism 66 or of a steering shaft connected to the steering mechanism 66. In this case, a steering angle of zero can represent, for example, a steering state corresponding to straight ahead. An increase in the value of the steering angle represents an increase in the bending of the front vehicle part 14 relative to the rear vehicle part 12, and for example the sign can represent the steering direction, i.e. the bending direction.

[0036] The rate of change of the steering angle can be determined from the change over time of the signal representative of the steering position. Alternatively, the signals representative of the rotational speed and rate of change of the steering angle can be generated directly, for example from the movement of the steering mechanism 66 or a steering shaft connected to the steering mechanism 66.

[0037] It is further noted that information representative of the steering state can be derived, for example, from the respective stationary installation or moving states of the steering piston / cylinder units 28, or can be provided directly by a sensor system acting or measuring between the front vehicle 14 and the rear vehicle 12.

[0038] The operating platform 22 is provided with further mechanisms, by means of which the operator can operate the earth moving machine 10. With the aid of a traction operating mechanism 72, configured for example as a traction operating lever 70, the operator can start the earth moving machine 10. This means that, for example by pivoting the traction operating lever 70, the electric motor 50 of the electrohydraulic pressure fluid source 48 of the hydraulic traction drive system 46 operates at a speed corresponding to the state of the traction mode set by the operator. For example, the operator can move the traction operating lever 70 to the park position. When the traction operating lever 70 is in the park position, the earth moving machine 10 is essentially at a standstill and, for example, the parking brake can be activated to prevent rolling. By pivoting from the park position to the traction ready position, the traction ready state is reached. In the traction ready state, the traction hydraulic motors 56, 58 remain inactive, i.e. for example the electric motor 50 remains inoperative, as in the parked state, but the parking brake is released. When turning from a traction ready position corresponding to a traction ready state to a traction position corresponding to a traction state, for example, the control unit 42 converts the preset values ​​of the target travel speed and the preset direction values ​​corresponding to each turning position into the rotation speed or rotation direction corresponding to the preset values ​​of the electric motor 50, so that the electric motor 50 drives the traction hydraulic pump 52 in the rotation direction corresponding to each traction direction, and pressure fluid is supplied to both traction hydraulic motors 56, 58, thereby causing the earthwork machine 10 to move on the ground surface 18.

[0039] The operator's seat 24 may be provided with a seat occupancy sensor 74 that provides information regarding whether an operator is seated at the operator's seat 24. This information, as well as information regarding each operating position or operating state of the traction operating mechanism 72, may be input to the control unit 42, which in turn causes the electric motor 38 of the electrohydraulic pressure fluid source 36 to operate as described below.

[0040] Taking into account the information representative of the seat occupancy or the operating state of the traction operating mechanism 72, the control unit 42 can control the electric motor 38 in such a way that it is deactivated or kept in an inactive state, for example when the traction operating mechanism 72 is in the parked position, which means that its control unit is deactivated. Alternatively or additionally, this can be done when the information provided by the seat occupancy sensor 74 indicates that no operator is present in the operator seat 24, as a result of which the optional parking brake is activated by no longer being supplied with a hold-open pressure to the parking brake. This also structurally ensures that the earthmoving machine comes to a safe stop in the event of failure of the control unit of the electric motor 38 or / and the electric motor 38.

[0041] When the traction operating mechanism 72 is in a traction ready position corresponding to a traction ready state, as is generally the case when an operator acting on the traction operating mechanism 72 is seated at the operator's seat 24, the control unit 42 can operate the electric motor 38 of the electrohydraulic pressure fluid source 36 to rotate at a base speed. As a result, pressure is generated in the steering hydraulic circuit 34, which can also be used to operate the driving hydraulic system or systems 67, for example to release the parking brake. In this case, for example, the base speed can be defined so that it does not vary. However, the base speed can also be adjusted depending on influencing variables, such as the temperature of the pressure fluid in the steering hydraulic circuit 34 or in the region of the driving hydraulic system or systems 67, so that, for example, with an increase in the temperature of the pressure fluid, the base speed is increased in order to ensure a faster exchange of the pressure fluid.

[0042] The base speed can also be adjusted or increased depending on the load demand on one or more operational hydraulic systems 67. For example, if it is recognized that several such operational hydraulic systems 67 are to operate simultaneously, which corresponds to a high load demand, which is manifested, for example, by one or more of such operational hydraulic systems 67 operating at too low a speed at the existing base speed, the base speed can be correspondingly increased.

[0043] When the traction operating mechanism 72 is brought into a traction position corresponding to a traction state, under the control of the control unit 42, the voltage applied to the electric motor 38 of the electrohydraulic pressure fluid source 36 can be set so that the electric motor 38 operates at an operating speed that is greater than the base speed, which may be set, for example, to be static or, like the base speed, can be adjusted depending on the temperature of the pressure fluid in the steering hydraulic circuit 34 and / or the load demands in one or more of the operating hydraulic systems 67.

[0044] Taking into account the steering information, i.e. for example information regarding the steering angle or the steering angle rate to be set in response to the operation of the steering actuation mechanism 66, the control unit 42 adjusts the operating speed of the electric motor 38 of the electrohydraulic pressure fluid source 36. This is exemplarily described below with reference to FIG. 3 using the steering angle rate L.

[0045] 3 shows the relationship between the steering angle change rate L and the rotation speed n of the electric motor 38. The rotation speed n of the electric motor 38 is, for example, a lower boundary value L 0 Until it reaches a nearly constant rotation speed n 0 The upper limit value L of the steering angle change rate L can be set to 0.5, which may correspond to the driving speed mentioned above. 1 If the rotation speed of the motor 38 is exceeded, the motor 38 rotates at a higher speed n 1 The lower boundary value L 0 and the upper boundary value L 1Between the boundary value L, the electric motor 38 operates at a rotation speed n that is, for example, linearly related to the steering angle change rate L. 0 and L 1 This means that the electric motor 38 is controlled so that its rotation speed n changes in proportion to the steering angle change rate L between the above values.

[0046] It is noted that other relationships may also be provided between the rotation speed n of the electric motor 38 and the steering angle rate L. For example, a gradual or tapered increase in the rotation speed n with the steering angle rate L may be provided as well as a stepwise increase.

[0047] By adapting the rotation speed of the electric motor 38 to the steering angle change rate L, there is a possibility to ensure that sufficient pressure fluid is supplied to the steering hydraulic system 30 to respond to high load demands in the hydraulic steering system 30 represented by a high steering angle change rate L and to provide a correspondingly fast steering response. This is therefore possible in the steering system 30 shown in FIG. 2, because the electric motor 38 responds very quickly to changes in the voltage applied to the electric motor 38 with corresponding changes in rotation speed, and thus can respond to the action on the steering operation mechanism 66 with approximately no time delay. For this reason, it is not necessary to take any adjustment means for the steering hydraulic pump 40 to adjust the delivery volume of the steering hydraulic pump 40. The change in the delivery volume of the steering hydraulic pump 40 is caused solely by changes in the rotation speed of the steering hydraulic pump 40 or by changes in the rotation speed of the electric motor 38 that drives the steering hydraulic pump 40. The steering hydraulic pump 40 may therefore be a constant delivery pump, which ensures a simple structure of the hydraulic steering system 30 and its easy controllability.

[0048] When controlling the electric motor 38, alternatively or additionally to taking into account the steering angle change rate L, it is also possible to use the steering angle itself in order to adjust the rotational speed of the electric motor 38. For example, with an increase in the steering angle, the rotational speed of the electric motor 38 can be increased, for example in a substantially linear relationship corresponding to Fig. 3, in a gradually or diminishingly increasing relationship, or in a stepwise relationship.

[0049] When entering or in a traction state, it can basically happen that the speed of the electric motor 38 is set or increased to the operating speed, possibly determined or adjusted in the above-mentioned way. In an alternative procedure, it can be provided that when entering or in a traction state, the electric motor 38 operates at the operating speed only if a change in steering state occurs, i.e. for example if a transition from straight driving to cornering is to occur, or if a transition from cornering to straight driving is to occur, or if the radius of the curve is to be changed when cornering. If the steering state does not change, i.e. for example if the earthmoving machine remains in the previously existing steering state when entering or in a traction state, this means that the earthmoving machine is operating in a straight driving state or with an approximately constant radius of the curve when cornering, the speed of the electric motor 38 is not increased to the operating speed, because no greater force has to be applied due to the change in steering state. When passing from a state in which the steering condition changes to a state in which the steering condition does not change in a traction state, the speed of the electric motor 38, which is currently operating at the operating speed, can be reduced again, for example to the base speed, thereby resulting in an efficient and energy-saving operation of the hydraulic steering system 30.

[0050] In an earth moving machine constructed according to the invention, the use of an electrohydraulic pressure fluid source creates the possibility for obtaining a very rapid adaptation of the operation of the electrohydraulic pressure fluid source to an existing or required steering operation. This reduces energy consumption, since the high power of the electric motor of the electrohydraulic pressure fluid source of the hydraulic steering system is present or utilized only when this is necessary. Nevertheless, such a system can be operated at a basic speed, for example in order to maintain the basic functions of the hydraulic steering system or the operating hydraulic system supplied by said system. In an earth moving machine constructed according to the invention, the advantages of a hydraulic steering system are combined with the advantages of the use of an electric motor for the operation of the steering hydraulic pump, also with regard to efficient energy use or energy saving or reduced noise emissions in phases in which operation at relatively low speeds is sufficient.

[0051] Finally, it should be pointed out that such an earthmoving machine can obviously be modified in various ways. For example, in a hydraulic steering system, the electrohydraulic pressure fluid source can include several steering pressure fluid pumps, which can be driven by a common or, respectively, separate electric motor of the electrohydraulic pressure fluid source. Also in the region of the hydraulic traction drive system, several traction hydraulic pumps can be provided, which can be driven by a common or, as the case may be, respectively separate electric motor. As already mentioned, it obviously goes without saying that an earthmoving machine configured, for example, as a soil compactor can be configured differently from the configuration described above or shown in FIG. 1, even with regard to the use of earthmoving rollers or drive wheels. [Additional note 1] 1. An earthmoving machine, in particular a soil compactor, comprising: An earthmoving machine including a hydraulic steering system (30) having at least one steering mechanism (26) operated with pressure fluid, and an electro-hydraulic pressure fluid source (36) including at least one steering pressure fluid pump (40) that can be driven by at least one electric motor (38) for supplying pressure fluid to a steering pressure fluid circuit (34). [Additional note 2] The earthmoving machine described in appended claim 1 includes a vehicle rear portion (12) and a vehicle front portion (14) that is rotatable about a steering axis relative to the vehicle rear portion (12), and at least one steering mechanism (26) acting between the vehicle front portion (14) and the vehicle rear portion (12) includes a steering piston / cylinder unit (28). [Additional note 3] The earthmoving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) includes a hydraulic steering unit (32), which is supplied with pressure fluid from the steering pressure fluid circuit (34) and supplies pressure fluid to at least one of the steering mechanisms (26) depending on the operation of a steering operation mechanism (66). [Additional note 4] 4. The earthmoving machine according to claim 1, wherein the hydraulic steering system (30) includes at least one steering sensor (68), the steering sensor (68) being configured to provide steering information representative of a steering state. [Additional note 5] 5. The earth moving machine according to claim 4, wherein the steering information represents a steering angle and / or a steering angle change rate (L). [Additional note 6] 6. The earthmoving machine according to claim 4 or 5, characterized in that the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a rotation speed (n) that depends on the steering information. [Additional note 7] 7. The earthmoving machine according to claim 6, wherein the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an increased rotational speed (n) when the steering angle increases, and / or the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an increased rotational speed (n) when the steering angle change rate (L) increases. [Additional note 8] 8. The earthmoving machine according to claim 1, wherein the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a rotational speed (n) that depends on a traction mode state of the earthmoving machine (10). [Additional note 9] The traction mode state of the earthmoving machine (10) is: - a parked state in which the traction operating mechanism (72) is in the parked position and / or no one is seated in the operator's seat (24); - a traction ready state in which the traction operating mechanism (72) is aligned to a traction ready position; and - a traction state in which the traction operating mechanism (72) is aligned with a traction position; Contains The hydraulic steering system (30) comprises: - in said parked state, the operation of the electric motor (38) of the electrohydraulic steering pressure fluid source is stopped, or / and - operating the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a base speed in the traction ready state, or / and The earth moving machine according to claim 8, characterized in that, in the traction state, the electric motor (38) of the electrohydraulic steering pressure fluid source (36) is operated at an operating speed that exceeds the basic speed. [Additional Note 10] 10. The earthmoving machine according to claim 9, characterized in that the base speed depends on a temperature of hydraulic fluid in a steering hydraulic circuit (34) and / or in an operating hydraulic system (67) supplied from the steering hydraulic circuit, and / or the base speed depends on a load requirement in the operating hydraulic system (67) supplied from the steering hydraulic circuit. [Additional Note 11] 11. The earth moving machine according to claim 9 or 10, characterized in that the hydraulic steering system (30) is configured to always operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at the operating speed in the traction state. [Additional Note 12] 11. The earthmoving machine according to claim 9 or 10, when referring to claim 4, characterized in that the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an operational speed when entering the traction state and / or in the traction state if the steering information indicates that there is a change in steering state. [Additional Note 13] 13. The earthmoving machine according to any one of claims 1 to 12, wherein the steering hydraulic pump (40) is a constant volume delivery pump. [Additional Note 14] 14. The earthmoving machine according to any one of claims 1 to 13, characterized in that a hydraulic traction drive system (46) is provided, the hydraulic traction drive system (46) including an electrohydraulic pressure fluid source (48) having at least one electric motor (50) and at least one traction hydraulic pump (52) for supplying pressure fluid to a traction hydraulic circuit (54), and at least one traction hydraulic motor (56, 58) supplied with pressure fluid from the traction hydraulic circuit (54). [Additional Note 15] 15. The earth moving machine according to claim 14, wherein the hydraulic steering system (30) and the hydraulic traction drive system (46) include electric motors (38, 50) that are operable independently of each other. [Additional Note 16] 16. The earth moving machine according to claim 14 or 15, wherein the hydraulic steering system (30) is configured to supply pressure fluid to the traction hydraulic circuit (54) through the steering hydraulic circuit (34). [Additional Note 17] 17. The earthmoving machine according to any one of claims 1 to 16, wherein the hydraulic steering system (30) is configured to send pressurized fluid back to a fluid tank (62) through the steering hydraulic circuit (34). [Additional Note 18] 18. A method for operating an earth moving machine (10), preferably an earth moving machine (10) according to any one of claims 1 to 17, the earth moving machine (10) comprising a hydraulic steering system (30) comprising at least one steering mechanism (26) actuated by a pressure fluid, an electro-hydraulic pressure fluid source (36) with at least one steering pressure fluid pump (40) which can be driven by at least one electric motor (38) for supplying pressure fluid to a steering pressure fluid circuit (34), and at least one steering sensor (68), the steering sensor (68) providing steering information representative of a steering state, the electric motor (38) of the electro-hydraulic steering pressure fluid source (36) operating at a speed (n) dependent on the steering information. [Additional Note 19] 19. The method according to claim 18, characterized in that the electric motor (38) of the electrohydraulic steering pressure fluid source (36) operates at an increased rotational speed (n) when the steering angle increases and / or the electric motor (38) of the electrohydraulic steering pressure fluid source (36) operates at an increased rotational speed (n) when the steering angle change rate (L) increases. [Explanation of symbols]

[0052] 10 Earthmoving Machinery 12 Rear of vehicle 14 Front of vehicle 16 Drive wheels 18 Ground 20 Earthwork roller 22 Control console 24 Operator seat 26 Steering mechanism 28 Steering piston / cylinder unit 30 Hydraulic steering system 32 Hydraulic steering unit 34 Steering hydraulic circuit, steering pressure fluid circuit 36 Electro-hydraulic pressure fluid source, electro-hydraulic steering pressure fluid source 38 Electric motor 40 Steering hydraulic pump, steering pressure fluid pump 42 Control Unit 44 Battery 46 Hydraulic Traction Drive System 48 Electrohydraulic Pressure Fluid Source 50 Electric motor 52 Traction hydraulic pump 54 Traction hydraulic circuit 56, 58 Traction hydraulic motor 60 Discharge valve device 62 Fluid Tank 64 Return valve 66 Steering mechanism 67 Driving Hydraulic System 68 Steering Sensor 70 Traction control lever 72 Traction operation mechanism 74 Seat occupancy sensor L Steering angle change rate L 0 Lower Boundary L1 Upper Boundary n,n 0 , n 1 Rotational speed

Claims

1. 1. An earthmoving machine comprising:

1. An earthmoving machine comprising: a hydraulic steering system (30) having at least one steering mechanism (26) operated with pressure fluid; and an electrohydraulic steering pressure fluid source (36) comprising at least one steering hydraulic pump (40) that can be driven by at least one electric motor (38) for supplying pressure fluid to a steering hydraulic circuit (34), wherein a hydraulic traction drive system (46) is provided, the hydraulic traction drive system (46) comprising at least one electric motor (50) and an electrohydraulic traction pressure fluid source (48) comprising at least one traction hydraulic pump (52) for supplying pressure fluid to a traction hydraulic circuit (54), and at least one traction hydraulic motor (56, 58) supplied with pressure fluid from the traction hydraulic circuit (54), the hydraulic steering system (30) and the hydraulic traction drive system (46) comprising electric motors (38, 50) that are operable independently of each other.

2. 2. The earth moving machine of claim 1, comprising a rear vehicle section (12) and a front vehicle section (14) pivotable about a steering axis relative to the rear vehicle section (12), wherein at least one of the steering mechanisms (26) acting between the front vehicle section (14) and the rear vehicle section (12) comprises a steering piston / cylinder unit (28).

3. 3. The earth moving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) includes a hydraulic steering unit (32), which is supplied with pressure fluid from the steering hydraulic circuit (34) and supplies pressure fluid to at least one of the steering mechanisms (26) depending on the operation of a steering operation mechanism (66).

4. 3. An earth moving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) includes at least one steering sensor (68), the steering sensor (68) configured to provide steering information representative of a steering condition.

5. 5. An earth moving machine according to claim 4, characterized in that the steering information represents a steering angle and / or a steering angle rate of change (L).

6. 5. An earthmoving machine according to claim 4, characterized in that the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a number of revolutions (n) dependent on the steering information.

7. 7. The earth moving machine according to claim 6, characterized in that the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an increased number of rotations (n) when the steering angle increases and / or the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an increased number of rotations (n) when the steering angle change rate (L) increases.

8. 3. An earthmoving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a speed (n) that depends on a state of traction mode of the earthmoving machine (10).

9. The traction mode state of the earth moving machine (10) is: - a parked state with the traction operating mechanism (72) in the parked position and / or with no one seated in the operator's seat (24); - a traction ready state in which the traction operating mechanism (72) is aligned to a traction ready position; and - a traction state in which the traction operating mechanism (72) is aligned to a traction position; Contains The hydraulic steering system (30) comprises: - in said parked state, the electric motor (38) of the electrohydraulic steering pressure fluid source (36) is deactivated, or / and - operating the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at a base speed in the traction ready state, or / and 9. An earth moving machine according to claim 8, characterized in that in the traction state, the electric motor (38) of the electrohydraulic steering pressure fluid source (36) is configured to operate at an operating speed which is higher than the base speed.

10. 10. An earthmoving machine according to claim 9, characterized in that the base speed depends on the temperature of hydraulic fluid in the steering hydraulic circuit (34) and / or in an operating hydraulic system (67) supplied from the steering hydraulic circuit and / or the base speed depends on the load demand in the operating hydraulic system (67) supplied from the steering hydraulic circuit (34).

11. 10. The earth moving machine of claim 9, wherein the hydraulic steering system (30) is configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at the operating speed at all times in the traction condition.

12. 10. The earthmoving machine of claim 9, wherein the hydraulic steering system (30) includes at least one steering sensor (68), the steering sensor (68) configured to provide steering information representative of a steering condition, and the hydraulic steering system (30) configured to operate the electric motor (38) of the electrohydraulic steering pressure fluid source (36) at an operational speed when entering and / or during the traction condition if the steering information indicates that a change in steering condition exists.

13. 3. An earthmoving machine according to claim 1 or 2, characterized in that the steering hydraulic pump (40) is a constant volume pump.

14. 3. An earth moving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) is configured to supply pressure fluid to the traction hydraulic circuit (54) through the steering hydraulic circuit (34).

15. 3. An earth moving machine according to claim 1 or 2, characterized in that the hydraulic steering system (30) is configured to deliver pressurized fluid through the steering hydraulic circuit (34) back to a fluid tank (62).

16. 3. An earthmoving machine according to claim 1 or 2, characterized in that the earthmoving machine (10) is a soil compactor.

17. 3. A method for operating an earth moving machine (10) as claimed in claim 1 or 2, wherein the hydraulic steering system (30) includes at least one steering sensor (68), the steering sensor (68) providing steering information representative of a steering state, and the electric motor (38) of the electrohydraulic steering pressure fluid source (36) operates at a speed (n) dependent on the steering information.

18. 18. The method according to claim 17, characterized in that the electric motor (38) of the electrohydraulic steering pressure fluid source (36) operates at an increased number of revolutions (n) when the steering angle increases and / or the electric motor (38) of the electrohydraulic steering pressure fluid source (36) operates at an increased number of revolutions (n) when the steering angle rate of change (L) increases.

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