DE102016224401A1 - Work hydraulic system and vehicle with the working hydraulic system - Google Patents

Abstract

The invention relates to a working hydraulic system (8) for a vehicle. The working hydraulic system (8) comprises a hydraulic actuator (11), a hydraulic pump (9) for driving the hydraulic actuator (11), a drive unit for driving the hydraulic pump (9) and a pressure accumulator (37), wherein the working hydraulic system (8) is set to increase the pressure within the pressure accumulator (37) and to use the pressure within the pressure accumulator (37) for driving the hydraulic actuator (11). Furthermore, the invention relates to a vehicle with the working hydraulic system (8).

Description

The invention relates to a working hydraulic system for a vehicle, in particular an off-highway vehicle. Another claim is directed to a vehicle, in particular an off-highway vehicle, with the working hydraulic system.

Stricter emission standards for off-highway vehicles mean that drive units for corresponding travel drives and industrial hydraulics systems are dimensioned smaller ("downsizing"). This has the consequence that the dynamics of the drive units becomes sluggish during torque build-up, which leads to a sluggish behavior of the working hydraulics or the traction drive. One measure for assessing the dynamics is the so-called "T90" time, which indicates the time required by the power plant to set from 0 Nm to 90% of the respective maximum torque of the drive unit. The T90 time increases with smaller sized drive units and constant torque decreases by drive and hydraulic system.

An object of the present invention may therefore be to provide a working hydraulic system for a vehicle, which has improved dynamics with constant torque decreases by travel drive and working hydraulic system and a relatively small drive unit.

The object is solved by the subject matters of the independent claims. Advantageous embodiments are subject of the dependent claims, the following description and the figures.

According to a first aspect of the invention, a working hydraulic system for a vehicle, in particular an off-highway vehicle, is provided. The off-highway vehicle may be, but is not limited to, a construction machine, in particular a wheel loader. However, the working hydraulic system according to the invention is also suitable in principle for any other off-highway vehicle with a working hydraulics.

The working hydraulic system according to the invention comprises a hydraulic actuator, e.g. a hydraulic cylinder for raising and lowering a bucket of a wheel loader. Furthermore, the working hydraulic system comprises a hydraulic pump for driving the hydraulic actuator and a drive unit for driving the hydraulic pump.

The hydraulic pump can generate hydraulic energy, which can be passed on in particular via control blocks to the hydraulic actuator to do work. The hydraulic pump may in particular be a load-sensing pump or the working hydraulic system may be a load-sensing system with elements necessary therefor and a hydraulic pump arranged therefor. Electrically controlled hydraulic pumps are particularly suitable for the working hydraulic system, as the delivery volume of such hydraulic pumps is freely adjustable.

The drive unit may comprise, for example, an internal combustion engine which can drive at least one output shaft directly or via a transmission. The output shaft is also referred to as PTO or Power Take Off (PTO) and can be coupled to the hydraulic pump to drive it. Furthermore, the working hydraulic system comprises a pressure accumulator, in particular a hydropneumatic accumulator, wherein the working hydraulic system is adapted to increase the pressure within the pressure accumulator and to use the pressure within the pressure accumulator to drive the hydraulic actuator.

A core of the invention is, in particular, in situations in which the working hydraulic system or its drive unit has sufficient power reserves to store energy in the pressure accumulator and feed it back into the working hydraulic system at a later time. This can be done, for example, during deceleration processes via the hydraulic pump of the working hydraulic system, which has the advantage, in particular at high delays with subsequent change of direction, that no additional fuel has to be injected to provide the deceleration energy and must be converted into heat in a converter and in a clutch. Consequently, fuel can be saved.

If the hydraulic actuator is a hydraulic cylinder for actuating a blade of a wheel loader, for example, potential energy can be stored in the preferably hydropneumatic pressure accumulator when the blade is lowered via the hydraulic cylinder and fed back into the working hydraulic system at a later point in time.

In the event of load peaks that exceed the power of the drive unit, additional energy can still be provided by the pressure accumulator. Load peaks occur especially when a travel drive and the hydraulic actuator simultaneously require power from the drive unit. The load peaks therefore determine the size of the drive unit in the design. The working hydraulic system according to the invention enables a smoothing of the load peaks and a reduction of the required peak power or the required peak torque of the drive unit.

Furthermore, mechanically-hydraulically power-split transmissions have a significantly slower delay due to their construction than comparable transducers. In deceleration operations from higher speeds, especially at speeds above 4 km / h, in mechanical-hydraulic power-split transmissions, the deceleration can be done exclusively via the drag torque of the rotor or the drive unit and load the hydraulic pump of the working hydraulic system (for example, by lifting a blade a wheel loader by means of the hydraulic actuator). In this situation, the working hydraulic system according to the invention enables the provision of an additional torque via the hydraulic pump, in which the hydraulic pump fills the pressure accumulator. As a result, a higher deceleration torque is generated, as a result of which a vehicle with the working hydraulic system according to the invention, in particular a wheel loader, can turn or hold faster without braking intervention.

The loading of the pressure accumulator can thus take place in a deceleration of a vehicle with the working hydraulic system according to the invention by an additional torque is built up by the working hydraulic system for drag torque of the drive unit. The working hydraulic system or its hydraulic pump fills in this way the accumulator and the vehicle is decelerated. Furthermore, energy can be stored in the accumulator in situations in which only a fraction of the engine torque or the moment of the drive unit is retrieved and in which the working hydraulic system does not decrease power. Although this leads in the short term to an increase in consumption, however, the filling of the pressure accumulator can also be applied in such a way that the engine map of the drive unit is moved into more efficient areas.

The unloading of the pressure accumulator and the associated supply of hydraulic power from the pressure accumulator hydraulic system ("Boosten") can be used to compensate for dynamics disadvantages, which arise from the fact that are used to comply with more stringent emission standards relatively small drive units. The pressure accumulator can supply the working hydraulic system with hydraulic energy, whereby the drive unit only has to apply the energy for a drive train (driving energy). Since the drive unit has to provide its maximum torque, especially when the traction drive and the working hydraulic system require energy at the same time, the maximum torque required can be reduced. The drive unit must therefore provide only a starting torque available, which results from the difference between the moment of the drive and the working hydraulics, but at least the moment of the working hydraulics minus the "zugeboosteten" moment of the hybrid system.

The hydraulic fluid does not necessarily have to flow into a tank of the working hydraulic system during unloading of the pressure accumulator ("boosting"). Likewise, the hydraulic fluid does not necessarily have to be removed from the tank during charging of the pressure accumulator. As an alternative to the tank, at least one corresponding additional low-pressure accumulator may be provided.

The working hydraulic system according to the invention makes it possible, in particular, that no additional hydraulic pump or additional hydraulic motor is required for a sufficient supply of the hydraulic actuator, but that existing components can be used. Furthermore, it is not necessary to convert energy, whereby conversion losses can be avoided. This means that hydraulic energy does not first have to be converted into mechanical energy in a hydraulic motor, but can be fed directly from the pressure accumulator into corresponding sections of the working hydraulic system.

According to a first embodiment, the working hydraulic system may be configured to increase the pressure within the pressure accumulator by means of the hydraulic pump. The hydraulic pump can be driven for example via a PTO of the drive unit. The hydraulic pump generates energy needed to perform the work of the hydraulic actuator. Between the hydraulic pump and the hydraulic actuator, a control valve can be arranged, which can be actuated by an operator of the working hydraulic system. If the working hydraulic system is a load-sensing system with necessary elements and a hydraulic pump arranged therefor, the hydraulic pump can recognize that the control valve has been actuated, and a volumetric flow and pressure generated by the hydraulic pump can be increased. In this case, the pickup power of the hydraulic pump increases, and the hydraulic actuator is operated to move, for example, a bucket of a wheel loader upward. If a desired position is reached, the control valve can be closed again by the user, whereby the volume flow of the hydraulic pump is reduced by the load-sensing system. The accumulator, for example, hydraulically be arranged parallel to the hydraulic actuator or to a supply line which leads from the hydraulic pump to the hydraulic actuator, wherein both the hydraulic actuator and the pressure accumulator can be fed by the hydraulic pump.

For storing hydraulic energy in the pressure accumulator, the pressure of the hydraulic pump can be increased. When using a load-sensing system, this could be manipulated, for example, by acting via a valve, the pressure in the accumulator to a pressure comparison of the load-sensing system, whereby the flow and the pressure of the hydraulic pump can be increased. Once the pressure outside the accumulator is higher than the pressure within the accumulator, the accumulator can be filled, e.g. by opening a valve, which is arranged in front of the pressure accumulator. Hydraulic fluid can then flow into the pressure accumulator and in particular compress a glass bubble of a hydropneumatic pressure accumulator. With continuous filling, the pressure within the accumulator increases. For the intended termination of a charging process of the pressure accumulator (in particular when a permissible maximum pressure is reached within the pressure accumulator) or at the termination of the filling of the pressure accumulator (in particular when the hydraulic actuator is to be actuated), the valve arranged in front of the pressure accumulator can be closed.

To feed the working hydraulic system with pressurized hydraulic fluid from the accumulator, for example, a valve arranged in front of the accumulator valve can be opened. When using a load-sensing system, the volume flow of the hydraulic pump is reduced, whereby the power consumption of the hydraulic pump decreases and the drive unit is relieved.

According to a further embodiment, the working hydraulic system may be configured to increase the pressure within the pressure accumulator by means of the hydraulic actuator. In particular, when the hydraulic actuator serves to lift a load, e.g. To operate a bucket of a wheel loader, potential energy released by lowering the load can be stored in the accumulator, for example, via a return line within the working hydraulic system. At a later time stored in the pressure accumulator potential energy can be fed back into corresponding sections of the hydraulic system work. Furthermore, the hydraulic actuator and the hydraulic pump can also be hydraulically coupled to the pressure accumulator such that the pressure accumulator is filled by the hydraulic actuator and the hydraulic pump at the same time.

This can be done in particular by the fact that the hydraulic actuator is reversely controlled, but this is only possible with electrically controllable hydraulic pumps. In this context, "reversely actuated" can be understood in particular to mean that hydraulic fluid of the working hydraulic system is lowered when a load, e.g. a blade of a wheel loader, and thus corresponding movement or actuation of the hydraulic actuator flows into the pressure accumulator, in providing a load-sensing system, in particular via a shuttle valve and a pressure compensator. In this case, a return line or a return to a flow or to a flow line and vice versa, via the return hydraulic fluid can be sucked from a corresponding tank of the working hydraulic system.

The working hydraulic system may further include a pressure sensor within a return line between the hydraulic actuator and a tank of the working hydraulic system, wherein the working hydraulic system is adapted to connect the return line to the accumulator, if the pressure within the return line exceeds a predetermined limit. In particular, the volume flow within the return line can be controlled in such a way that a user of the working hydraulic system does not experience a slowdown of a mechanical load, e.g. a bucket of a wheel loader, noticed by the hydraulic actuator. This can be done, for example, by venting part of the volume flow within the return line into an oil tank of the working hydraulic system, e.g. via a control panel.

According to a further embodiment, the working hydraulic system further comprises a control block, wherein the control block is adapted to control a pressure increase within the pressure accumulator. The control block may in particular comprise a controllable directional control valve. For example, the control block may comprise at least one directional control valve and a control unit for adjusting a switching position of the directional control valve, wherein the directional control valve is connected to the hydraulic pump on the one hand and with the preferred hydropneumatic pressure accumulator on the other hand. In the following, "connected" can be understood in particular to mean that corresponding elements are hydraulically connected to one another such that hydraulic fluid can flow from one element to the other element. In a particularly simple embodiment, for example, a 2/2-way valve can be used, wherein the 2/2-way valve controlled by the control unit is and wherein an input to the hydraulic pump and an output connected to the pressure accumulator. In a first switching position, the input and the output can be shut off, and in a second switching position, the input and the output can be connected to each other. The 2/2-way valve may, for example, be spring-biased in the first position and be brought against the bias by means of a controllable electromagnet in the second position, wherein the control unit can control the solenoid accordingly. The control block allows demand-driven and simple control or regulation of the filling or emptying of the pressure accumulator by means of hydraulic fluid of the working hydraulic system.

According to a further embodiment, the working hydraulic system further comprises a hydraulic motor, wherein the working hydraulic system is adapted to drive the hydraulic motor by means of the pressure accumulator, and wherein the hydraulic motor is adapted to drive the hydraulic pump and / or the drive unit. By means of the additional hydraulic motor, which can be driven in particular by a PTO of the drive unit, energy stored in the pressure accumulator can be converted back into mechanical energy and fed back into the overall system. This results in particular the advantage that a drive of a vehicle equipped with the working hydraulic system according to the invention or the vehicle driving the drive unit can be supported in any situation. In addition, the accumulator can be particularly small dimensions, since a usable pressure difference of the pressure accumulator can be between 110 and 330 bar, which corresponds to a pressure difference between the pressure accumulator and a tank of the working hydraulic system instead of a pressure difference between the pressure accumulator and a pressure within the working hydraulic system. Furthermore, the pressure difference can easily be above 400 bar. The additional hydraulic motor may be arranged in series with the hydraulic pump on one and the same PTO. The additional hydraulic motor and the hydraulic pump can continue to be arranged parallel to each other and driven by different PTOs. Furthermore, the additional hydraulic motor between the drive unit and a transmission may be arranged, which is driven by the drive unit.

Furthermore, the pressure accumulator can be integrated as a load-controlled consumer in the working hydraulic system. This is particularly appropriate in connection with the embodiment described in the previous paragraph, if this is designed as a load-sensing system, as is typically the case in modern construction equipment.

According to another embodiment, the working hydraulic system further comprises an adjustable (combined) hydraulic pump / motor unit, wherein the working hydraulic system is adapted to increase the pressure within the accumulator by means of the hydraulic pump / motor unit. Furthermore, by the engine function of the hydraulic pump / motor unit, the drive unit and / or the hydraulic pump can be supported. The adjustable hydraulic pump / motor unit may be arranged in series with the hydraulic pump on one and the same PTO. The adjustable hydraulic pump / motor unit and the hydraulic pump may further be arranged parallel to each other and driven by different PTOs. Furthermore, the adjustable hydraulic pump / motor unit may be arranged between the drive unit and a transmission which is driven by the drive unit.

According to a further embodiment, the working hydraulic system further comprises an adjustable further hydraulic pump and an adjustable hydraulic motor, wherein the working hydraulic system is adapted to increase the pressure within the pressure accumulator by means of the further hydraulic pump and to drive the hydraulic motor by means of the pressure accumulator, and wherein the hydraulic motor is arranged to drive the hydraulic pump and / or the drive unit. The further hydraulic pump or the hydraulic motor may be arranged in series with the hydraulic pump on one and the same PTO, wherein the not connected to the hydraulic pump in series hydrostat can be driven by another PTO of the drive unit. Furthermore, the further hydraulic pump can be arranged in series with the hydraulic motor on one and the same PTO, wherein the hydraulic pump can be driven by another PTO of the drive unit. Further, the further hydraulic pump and the hydraulic motor between the drive unit and a transmission may be arranged, which is driven by the drive unit. Furthermore, the further hydraulic pump and the hydraulic motor may be connected without a hydraulic pump of the working hydraulic system.

According to a second aspect of the invention there is provided a vehicle, in particular an off-highway vehicle, which comprises a working hydraulic system according to the first aspect of the invention.

• 1 eine Draufsicht auf einen Antrieb eines Off-Highway-Fahrzeugs,
• 2 einen Hydraulikschaltplan eines Ausführungsbeispiels eines erfindungsgemäßen Arbeitshydrauliksystems mit einem Druckspeicher für das Fahrzeug nach 1,
• 3 das Arbeitshydrauliksystem nach 2 in alternativer Konfiguration,
• 4 das Arbeitshydrauliksystem nach 2 in weiterer alternativer Konfiguration,
• 5 das Arbeitshydrauliksystem nach 2 in weiterer alternativer Konfiguration mit einem Hydraulikmotor,
• 6 das Arbeitshydrauliksystem nach 2 in weiterer alternativer Konfiguration mit einem als lastgesteuerter Verbraucher integrierten Druckspeicher,
• 7 das Arbeitshydrauliksystem nach 2 in weiterer alternativer Konfiguration mit einer verstellbaren Hydraulikpumpen-/Motoreinheit an einem PTO und
• 8 das Arbeitshydrauliksystem nach 7 in weiterer alternativer Konfiguration mit einer verstellbaren Pumpe und einem verstellbarem Motor an einem PTO.

In the following, embodiments of the invention will be explained in more detail with reference to the schematic drawing, wherein the same or similar elements are provided with the same reference numerals. This shows

• 1 a top view of a drive of an off-highway vehicle,
• 2 a hydraulic circuit diagram of an embodiment of a working hydraulic system according to the invention with a pressure accumulator for the vehicle after 1 .
• 3 the working hydraulic system after 2 in an alternative configuration,
• 4 the working hydraulic system after 2 in a further alternative configuration,
• 5 the working hydraulic system after 2 in a further alternative configuration with a hydraulic motor,
• 6 the working hydraulic system after 2 in a further alternative configuration with an accumulator integrated as load-controlled consumer,
• 7 the working hydraulic system after 2 in another alternative configuration with an adjustable hydraulic pump / motor unit on a PTO and
• 8th the working hydraulic system after 7 in another alternative configuration with an adjustable pump and an adjustable motor on a PTO.

1 shows a drive unit 1 an off-highway vehicle 2 , in the through 1 The embodiment shown is the drive unit 1 around an internal combustion engine. The drive unit 1 drives a gearbox 3 at. The gear 3 On the output side, it has a PTO shaft or a power take-off PTO ,

The gear 3 is further configured to have two more output shafts 4 and 5 a front axle 6 and a rear axle 7 of the vehicle 2 drive. The drive unit 1 This way it is set up via the gearbox 3 Torques on the PTO and on the output shafts 4 and 5 transferred to.

2 shows a working hydraulic system 8th which is a hydraulic pump 9 includes, wherein the hydraulic pump 9 of the PTO out 1 is driven. The hydraulic pump 9 delivers hydraulic fluid in the form of oil from a tank T in a supply or in a supply line 10 which is a hydraulic actuator in the form of a hydraulic cylinder 11 leads. About a first branch 10.1 the supply line 10 can be parallel to the hydraulic cylinder 11 another hydraulic consumer 12 with oil from the tank T through the hydraulic pump 9 be fed.

The supply line 10 includes a check valve 13 , which provides an unintended return of oil from the supply line 10 into the hydraulic pump 9 prevented. Furthermore, the flow line includes 10 a control valve 14 in the form of an aperture with adjustable cross-section. In the by 2 shown working hydraulic system 8th it is a load-sensing system. To enable the load sensing function, the work hydraulic system includes 8th in particular a pressure balance 15 which are within the supply line 10 is arranged, control lines 16 to 21 and a pressure comparison valve 22 , Furthermore, it is the hydraulic pump 9 to an electrically controlled load-sensing pump.

In front of the hydraulic cylinder 11 is a shuttle valve 23 arranged. The shuttle valve 23 has a first input side port 24 and a second input side terminal 25 on. The first input side connection 24 is with the supply line 10 connected. The second input side connection 25 is with a return or with a return line 26 connected, which in turn with the tank T connected is. Furthermore, the shuttle valve includes 23 a first output side port 27 , a second output side port 28 and a third party exit 29 , The first output side connection 27 is via a first connection line 30 with a first work space 31 of the hydraulic cylinder 11 connected. The second output side connection 28 is with the pressure comparison valve 22 connected, which within one of the control lines 19 is arranged. The third output side connection 29 is via a second connection line 32 with a second workspace 33 of the hydraulic cylinder 11 connected. The first workroom 31 and the second workspace 33 of the hydraulic cylinder 11 be about a piston 34 of the hydraulic cylinder 11 separated from each other. A piston rod 35 is on the one hand with the piston 34 connected and on the other hand with a blade, not shown, of the vehicle 2 connected. In the vehicle 2 it is a wheel loader. By means of the piston rod 35 of the hydraulic cylinder 11 can the bucket of the wheel loader 2 be raised and lowered.

The shuttle valve 23 can be put in three positions. In the by 2 shown middle switch position are the flow line 10 and the return line 26 shut off. On the other side are also the first connecting line 30 , the control line 19 and the second connection line 32 shut off. In this middle switching position of the piston 34 and the piston rod 35 in her by 2 shown position within a socket 36 of the hydraulic cylinder 11 held. In a left switch position of the shuttle valve 23 is the supply line 10 with the first connection line 30 and with the control line 19 connected. Furthermore, in the left switching position of the shuttle valve 23 the second connection line 32 with the return line 26 connected. In this left switching position of the piston 34 and the piston rod 35 inside the socket 36 shifted to the right, reducing the bucket of the wheel loader 2 can be raised. In a right switching position of the shuttle valve 23 is the supply line 10 with the second connection line 32 and with the control line 19 connected. Furthermore, in the right switching position of the shuttle valve 23 the first connection line 30 with the return line 26 connected. In this right switch position, the piston 34 and the piston rod 35 inside the socket 36 shifted to the left, causing the bucket of the wheel loader 2 can be lowered.

The hydraulic pump 9 Generates the necessary hydraulic energy needed to load the wheel loader's bucket 2 by means of the hydraulic cylinder 11 raise and lower. The control valve 14 can by a worker of the working hydraulics 8th be actuated, which by the hydraulic pump 9 is detected, which then increases the flow and the pressure. This increases the power of the hydraulic pump 9 and the hydraulic cylinder 11 moves so that, for example, the bucket of the wheel loader 2 is raised. Once a desired position is reached, the operator can control the control valve 14 close again, reducing the flow rate of the hydraulic pump 9 through the load-sensing system 8th is reduced.

The working hydraulic system 8th further includes a pressure accumulator 37 in the embodiment shown, a hydropneumatic pressure accumulator. The accumulator 37 is over a second branch 10.2 the supply line 10 and a control block 38 with a directional valve 39 and a control unit 40 to the hydraulic pump 9 connected. Within the hydropneumatic accumulator 37 can be compressed by the oil, a gas, in the embodiment shown nitrogen.

The control block 38 is designed to increase the pressure within the hydropneumatic accumulator 37 by means of the directional valve 39 and the control unit 40 to control. The control unit 40 is to adjust a switching position of the directional control valve 39 set up, the directional valve 39 with the hydraulic pump 9 on the one hand and with the hydropneumatic pressure accumulator 37 on the other hand. In the embodiment shown, it is the directional control valve 39 around a 2/2-way valve, with an input 41 over the first branch 10.1 the supply line 10 with the hydraulic pump 9 and an exit 42 with the accumulator 37 connected is. In a through 2 shown first switching position of the directional control valve 39 are the entrance 41 and the exit 42 shut off, and in a second switching position of the directional control valve 39 can the entrance 41 and the exit 42 be connected to each other. The 2 / 2 -Wegeventil is spring-biased in the first position and can be against the bias by means of a controllable electromagnet 43 be placed in the second position. The control unit 40 is set to the electromagnet 43 to control accordingly.

In the by 2 shown embodiment, the pressure accumulator 37 hydraulically parallel to the supply line 10 and thus also hydraulically parallel to the hydraulic actuator 11 arranged. By means of the control block 38 can be a filling and emptying of the pressure accumulator 37 be managed. By filling the pressure accumulator 37 with oil from the second branch 10.2 the supply line 10 can the nitrogen within the accumulator 37 be compressed and in this way hydraulic energy within the pressure accumulator 37 get saved. By emptying the pressure accumulator 37 (by draining oil into the second branch 10.2 the supply line 10 ) can the nitrogen within the pressure accumulator 37 be relaxed and in this way hydraulic energy from the accumulator 37 in the supply line 10 are discharged to the drive of the hydraulic cylinder 11 and / or the other consumer 12 to support ("boosting").

To store the energy, the pressure of the hydraulic pump 9 increase. This can be done by using the load-sensing system 8th is manipulated. For example, via a not shown valve, the pressure in the pressure accumulator 37 on the pressure comparison of the load-sensing system 8th act, reducing the flow and the pressure of the hydraulic pump 9 climb. Once the pressure within the second branch 10.2 the supply line 10 is higher than the pressure in the accumulator 37 (which for example by the control unit 40 can be determined), the control unit 40 the directional valve 39 so control that the directional control valve 39 moved to its second switching position, so that the second branch 10.2 the supply line 10 with the accumulator 37 connected is. The hydraulic fluid from the second branch 10.2 can in the second switching position of the directional control valve 39 in the accumulator 37 flow and compress the gas bubble with nitrogen. In this way, the pressure in the accumulator increases 37 , When the charging process is completed (eg when a maximum allowable pressure within the pressure accumulator 37 is reached) or the charging is canceled (for example because of the hydraulic cylinder 11 is to be actuated), the control unit 40 the directional valve 39 be controlled so that it moves to its first switching position, in which the second branch 10.2 of the supply line 10 is shut off and thus the accumulator 37 is neither filled nor emptied.

For emptying the pressure accumulator 37 can the control unit 40 the directional valve 39 control such that it moves to its second switching position, so that hydraulic fluid from the accumulator 37 again the second branch 10.2 the supply line 10 can flow back. The hydraulic pump 9 In this case, it can reduce the volume flow emitted by it, which reduces the power consumption of the hydraulic pump 9 decreases and the internal combustion engine 1 is relieved. The working hydraulics can thus from the pressure accumulator 37 and from the hydraulic pump 9 be fed by the displacement of the hydraulic pump 9 is reduced so far that the desired moment on the hydraulic pump 9 established.

When decelerating or braking the vehicle 2 can in addition to the drag torque of the internal combustion engine 1 an additional moment through the working hydraulic system 8th be built by the hydraulic pump 9 as described above hydraulic fluid in the pressure accumulator 37 promotes, eliminating the vehicle 2 is further delayed. In situations where only a fraction of the engine torque of the internal combustion engine 1 and in which the working hydraulic system 8th no or hardly any torque decreases, energy can also be stored in the accumulator. Emptying the pressure accumulator 37 can be done as described above, especially when peak loads occur and the internal combustion engine 1 should be supported.

3 shows the working hydraulic system 2 with an alternative directional valve 39 in front of the accumulator 37 and with a pressure sensor 44 within the return line 26 , that through 3 shown working hydraulic system 8th Also allows energy while lowering the bucket of the wheel loader 2 over the hydraulic cylinder 11 and the return line 26 in the accumulator 37 can be stored. In the return line 26 is the pressure sensor 44 , When the pressure within the return line 26 higher than in the accumulator 37 (which for example by the control unit 40 can be determined), the control unit 40 the directional valve 39 so control that hydraulic fluid from a third branch 3 the return line 26 via the directional valve 39 in the accumulator 37 instead of via the return line 26 in the tank T to drain.

At the directional valve 39 is it in the by 3 shown embodiment to a 3/3-way valve. A first input side connection 45 of the directional valve 39 is with the second branch 10.2 the supply line 10 connected, a second input side connection 46 of the directional valve 39 is with the third branch 10.3 of the return line 26 connected, and an output-side connection 47 is with the accumulator 37 connected.

The directional valve 39 can in a through 3 shown right switching position are moved, in which the second branch 10.2 the supply line 10 is shut off, and in which the third branch 10.3 of the return line 26 with the accumulator 37 connected is. In this right switch position can pressure medium from the return line 26 over the third branch 10.3 and over the way valve 39 in the accumulator 37 flow and the gas bubble within the accumulator 37 compacted. The shuttle valve 23 in front of the hydraulic cylinder 11 is also in its right switching position, in which the hydraulic pump 9 via the supply line 10 with the second workspace 33 of the hydraulic cylinder 11 is connected, and in which the first working space 31 of the hydraulic cylinder 11 with the return line 26 connected is. This right switching position of the shuttle valve 23 corresponds to a "lowering" position, in which the weight of the blade of the wheel loader 2 on the piston rod 35 and the piston 34 of the hydraulic cylinder 11 acts, so the piston rod 35 and the piston 34 be moved to the left. The hydraulic pump 9 can support this shifting force even further. In this way, hydraulic fluid is pressurized from the first working space 31 of the hydraulic cylinder 11 in the return line 26 promoted and can store energy in the accumulator 37 be used.

The volume flow hydraulic fluid, which from the return line 26 in the accumulator 37 flows, is controllable, in particular via a controllable throttle valve 14.1 which, for example, by the control unit 40 can be controlled. The throttle valve 14.1 allows a defined volume flow of hydraulic fluid into the tank T drains off and the remaining volume flow of hydraulic fluid pressure accumulator 37 over the third branch 10 , 3 of the return line 26 is supplied. In this way, it can be avoided that lowering the bucket of the wheel loader 2 by filling the accumulator 37 is delayed.

The directional valve 39 can continue to be moved to a middle switching position, in which the second branch 10.2 the supply line 10 with the accumulator 37 can be connected, wherein the third branch 10.3 of the return line 26 is locked. In this way, as related to 2 described the gas bubble within the accumulator 37 by hydraulic fluid passing through the hydraulic pump 9 in the second branch 10.2 the supply line 10 is promoted, compressed become. Furthermore, the directional control valve 39 be moved to a left switch position, in which both the second branch 10.2 the supply line 10 and the third branch 10.3 of the return line 26 are locked. Furthermore, the accumulator is also 37 shut off, so the accumulator 37 neither hydraulic fluid can be supplied nor removed.

In the by 4 shown embodiment, which according to the embodiment 2 is similar, the supply line 10 to the return line 26 and vice versa, being via the return line 26 Hydraulic fluid from the tank T can be sucked. In the by 4 shown left switching position of the shuttle valve 23 and the right switching position of the directional control valve 39 can hydraulic fluid from the first working space 31 over the shuttle valve 23 as well as the pressure balance 15 in the supply line 10 flow, which over the second branch 10.2 and the directional valve 39 with the accumulator 37 connected is. The hydraulic cylinder 11 is thus "reversed" as by 2 shown, but this is only possible if the hydraulic pump 9 is electrically controlled. Thus, the pressure accumulator 37 lowering the bucket of the wheel loader 2 (which is a displacement of the piston rod 35 and the piston 34 to the left) through the hydraulic cylinder 11 filled with hydraulic fluid and thus stored energy.

That through 5 The embodiment shown differs from the exemplary embodiment 2 in that the accumulator 37 can be filled and emptied in another way. Furthermore, the working hydraulic system 8th to 5 a hydraulic motor 48 on, in front of another directional control valve 49 is arranged. In the by 5 shown right switching position of the directional control valve 39 is the hydraulic pump 9 with the supply line 10 whereas a first supply line 50 of the accumulator 37 is locked. The pressure balance 15 is located in the 5 shown left switching position, in which the supply line 10 is locked. Thus, the hydraulic pump 9 not the hydraulic cylinder 11 press and not the accumulator 37 fill. Instead, it works through the hydraulic pump 9 generated pressure over the first branch 10.1 to the second consumer 12 , A branch 51 the supply line 50 leads to the further directional control valve 49 , The further directional valve 49 is in the through 5 shown embodiment in its left switching position, in which the branch 51 the supply line 50 is locked. Thus, the pressure accumulator 37 Hydraulic fluid can neither be supplied nor removed.

Unless the directional valve 39 remains in its right switch position and the other way valve 49 is moved to its right switch position, the branch 51 the supply line 50 with the hydraulic motor 48 connected so that hydraulic fluid from the accumulator 37 can escape under pressure, over the branch 51 the supply line 50 and the further directional valve 49 the hydraulic motor 48 can be supplied and thereby can drive it. In this way, by means of the hydraulic motor 48 in the accumulator 37 stored hydraulic energy is converted back into mechanical energy and into the working hydraulic system 8th be fed back. This results in the advantage that the drive of the vehicle 2 can be supported and thus in every situation the internal combustion engine 1 can be supported.

In the by 5 embodiment shown is the hydraulic motor 48 in series with the hydraulic pump 9 switched, that is both the hydraulic pump 9 as well as the hydraulic motor 48 be of the PTO of the transmission 3 of the vehicle 2 driven (the hydraulic pump 9 and the hydraulic motor 48 lie on the same PTO of the transmission 3 ). Alternatively, the hydraulic motor 48 but also parallel to the hydraulic pump 9 be arranged and another one PTO (not shown) of the transmission 3 are driven. Furthermore, the hydraulic motor 48 also between the combustion engine 1 and the transmission 3 be located and directly from the internal combustion engine 1 are driven.

To the accumulator 37 To fill, the directional valve can 39 for example by the control unit 40 be moved to its left switch position, in which the hydraulic pump 9 with the supply line 50 connected is. In this way, the hydraulic pump 9 via the directional valve 39 and the supply line 50 the accumulator 37 fill. If there is the further directional control valve 49 is in its left switch position, only the pressure accumulator 37 filled and there can be no hydraulic fluid over the branch 51 the supply line 50 to the hydraulic motor 48 flow.

In the by 6 shown embodiment of a working hydraulic system according to the invention 8th replaces the accumulator 37 the hydraulic cylinder 11 ie the accumulator 37 is behind the shuttle valve 23 arranged and as a load-controlled consumer in the working hydraulic system 8th integrated. In the by 6 shown left switching position of the pressure compensator 15 is the second branch 10.2 the supply line 10 shut off, so the hydraulic pump 9 over the first branch 10.1 the supply line 10 the other consumer 12 drives. The other consumer 12 is with the Return line 26 connected such that the hydraulic motor 48 from the other consumer 12 can be driven when hydraulic fluid under pressure from the other consumer 12 exit.

In the by 6 shown middle position of the shuttle valve 23 is the accumulator 37 locked off and can neither over the second branch 10.2 the supply line 10 be filled, still on the return line 26 be emptied. Unless the shuttle valve 23 is moved to its left switch position, the pressure accumulator 37 with the output line 26 connected so that hydraulic fluid from the accumulator 37 under pressure via the shuttle valve 23 and via the return line 26 the other consumer 12 and the hydraulic motor 48 can be supplied to drive this. The accumulator 37 can by means of the hydraulic pump 9 be filled, provided the pressure balance 15 is in its right switch position and provided the shuttle valve 23 is in its right switch position.

In the by 6 embodiment shown is the hydraulic motor 48 in series with the hydraulic pump 9 switched, that is both the hydraulic pump 9 as well as the hydraulic motor 48 be of the PTO of the transmission 3 of the vehicle 2 driven (the hydraulic pump 9 and the hydraulic motor 48 lie on the same PTO of the transmission 3 ). Alternatively, the hydraulic motor 48 but also parallel to the hydraulic pump 9 be arranged and another one PTO (not shown) of the transmission 3 are driven. Furthermore, the hydraulic motor 48 also between the combustion engine 1 and the transmission 3 be located and directly from the internal combustion engine 1 are driven.

That through 7 shown embodiment of a working hydraulic system according to the invention 8th differs from the embodiment according to 2 through the arrangement, filling and emptying of the pressure accumulator 37 , Furthermore, the working hydraulic system includes 8th to 7 an adjustable hydraulic pump / motor unit 52 which by the PTO is driven, which is also the hydraulic pump 9 drives. Alternatively, the hydraulic pump / motor unit 52 but also parallel to the hydraulic pump 9 be arranged and by another PTO (not shown) of the transmission 3 are driven. Furthermore, the hydraulic pump / motor unit 52 also between the combustion engine 1 and the transmission 3 be located and directly from the internal combustion engine 1 are driven.

In the by 7 shown left switching position of the directional control valve 39 are both the hydraulic pump / motor unit 52 as well as the accumulator 37 shut off, so that the accumulator 37 can neither be filled nor emptied. Unless the directional valve 39 in its right switch position is the hydraulic pump / motor unit 52 with the accumulator 37 connected so that the accumulator 37 by means of the hydraulic pump / motor unit 52 can be filled. Furthermore, in this switching position of the pressure accumulator 37 be emptied so that hydraulic fluid under pressure the pressure accumulator 37 leaves and over the way valve 39 the hydraulic pump / motor unit 52 is supplied and this drives.

That through 8th shown embodiment of a working hydraulic system according to the invention 8th differs from the embodiment according to 7 in that instead of the hydraulic pump / motor unit 52 an adjustable pump 53 and an adjustable engine 54 are provided. The working hydraulic system 8th is set to the pressure within the accumulator 37 by means of the adjustable pump 53 to increase and the adjustable engine 54 by means of the pressure accumulator 37 drive. The hydraulic motor 54 is in turn set up, the hydraulic pump 9 and / or the drive unit 1 drive. The adjustable pump 53 or the engine 54 can be in series with the hydraulic pump 9 at one and the same PTO be arranged, wherein the not connected in series with the hydraulic pump Hydrostat 53 respectively. 54 from another PTO (not shown) of the power plant 1 can be driven. Furthermore, the adjustable pump 53 in series with the engine 54 at one and the same PTO be arranged, the hydraulic pump 9 from another PTO of the drive unit 1 can be driven. Furthermore, the adjustable pump 53 and the hydraulic motor 54 between the drive unit 1 and a gearbox 3 be arranged, which by the drive unit 1 is driven. Furthermore, the adjustable pump 53 and the engine 54 even without a hydraulic pump 9 of the working hydraulic system 8th be connected.

PTO

Power-Take-Off

T

Tank

1

Antriebsaggregat

2

Off-Highway-Fahrzeug

3

Getriebe

4

Ausgangswelle

5

Ausgangswelle

6

Vorderachse

7

Hinterachse

8

Arbeitshydrauliksystem

9

Hydraulikpumpe

10

Zulaufleitung

10.1

erster Zweig

10.2

zweiter Zweig

11

Hydraulikzylinder

12

weiterer Verbraucher

13

Rückschlagventil

14

Steuerblende

14.1

Steuerblende

15

Druckwaage

16

Steuerleitung

17

Steuerleitung

18

Steuerleitung

19

Steuerleitung

20

Steuerleitung

21

Steuerleitung

22

Druckvergleichsventil

23

Hydraulikzylinder

24

erster eingangsseitiger Anschluss

25

zweiter eingangsseitiger Anschluss

26

Rücklaufleitung

27

erster ausgangsseitiger Anschluss

28

zweiter ausgangsseitiger Anschluss

29

dritter ausgangsseitiger Anschluss

30

erste Verbindungsleitung

31

erster Arbeitsraum

32

zweite Verbindungsleitung

33

zweiter Arbeitsraum

34

Kolben

35

Kolbenstange

36

Zylinderbuchse

37

Druckspeicher

38

Steuerblock

39

Wegeventil

40

Steuerungseinheit

41

eingangsseitiger Anschluss

42

ausgangsseitiger Anschluss

43

Elektromagnet

44

Drucksensor

45

erste eingangsseitiger Anschluss

46

zweiter eingangsseitiger Anschluss

47

ausgangsseitiger Anschluss

48

Hydraulikmotor

49

Wegeventil

50

Versorgungsleitung

51

Zweig der Versorgungsleitung

52

Hydraulikpumpen-/Motoreinheit

53

verstellbare Pumpe

54

verstellbarer Motor

reference numeral

PTO

Power-Take-Off

T

tank

1

power unit

2

Off-highway vehicle

3

transmission

4

output shaft

5

output shaft

6

Front

7

rear axle

8th

Working hydraulic system

9

hydraulic pump

10

supply line

10.1

first branch

10.2

second branch

11

hydraulic cylinders

12

other consumers

13

check valve

14

control panel

14.1

control panel

15

pressure compensator

16

control line

17

control line

18

control line

19

control line

20

control line

21

control line

22

Pressure comparison valve

23

hydraulic cylinders

24

first input-side connection

25

second input-side connection

26

Return line

27

first output side connection

28

second output side connection

29

third output side connection

30

first connection line

31

first working space

32

second connection line

33

second workspace

34

piston

35

piston rod

36

cylinder liner

37

accumulator

38

control block

39

way valve

40

control unit

41

input side connection

42

output side connection

43

electromagnet

44

pressure sensor

45

first input side connection

46

second input-side connection

47

output side connection

48

hydraulic motor

49

way valve

50

supply line

51

Branch of supply line

52

Hydraulic pump / motor unit

53

adjustable pump

54

adjustable engine

Claims (10)

Work hydraulic system (8) for a vehicle (2) comprising a hydraulic actuator (11), a hydraulic pump (9) for driving the hydraulic actuator (11), a drive unit (1) for driving the hydraulic pump (9), a pressure accumulator (37), wherein the working hydraulic system (8) is adapted to - To increase the pressure within the accumulator (37) and - To use the pressure within the pressure accumulator (37) for driving the hydraulic actuator (11). Working hydraulic system (8) after Claim 1 , wherein the working hydraulic system (8) is adapted to increase the pressure within the pressure accumulator (37) by means of the hydraulic pump (9). Working hydraulic system (8) after Claim 1 or 2 , wherein the working hydraulic system (8) is adapted to increase the pressure within the pressure accumulator (37) by means of the hydraulic actuator (11). Working hydraulic system (8) after Claim 3 , the working hydraulic system (8) further comprising a pressure sensor (44) within a return line (26) between the hydraulic actuator (11) and a tank (T) of the working hydraulic system (8), wherein the working hydraulic system (8) is adapted to the return line (26) to connect to the pressure accumulator (37), provided that the pressure within the return line (26) exceeds a predetermined limit. The work hydraulic system (8) of any of the preceding claims, the work hydraulic system (8) further comprising a control block (38, 39, 40), the control block (38, 39, 40) being adapted to increase pressure within the accumulator (37) Taxes. Work hydraulic system (8) according to any one of the preceding claims, the working hydraulic system (8) further comprising a hydraulic motor (48), wherein the working hydraulic system (8) is adapted to drive the hydraulic motor (48) by means of the pressure accumulator (37), and wherein the hydraulic motor (48) is adapted to drive the hydraulic pump (40) and / or the drive unit (1). Working hydraulic system (8) after Claim 6 , wherein the pressure accumulator (37) is integrated as a load-controlled consumer in the working hydraulic system (8). The work hydraulic system (8) according to any one of the preceding claims, the work hydraulic system (8) further comprising an adjustable hydraulic pump / motor unit (52), wherein the drive unit (1) is adapted to drive the hydraulic pump / motor unit (52), and wherein the Work hydraulic system (8) is adapted to increase the pressure within the pressure accumulator (37) by means of the hydraulic pump / motor unit (52). Work hydraulic system (8) according to one of the preceding claims, the working hydraulic system (8) further comprising an adjustable further hydraulic pump (53) and an adjustable hydraulic motor (54), wherein the working hydraulic system (8) is adapted to increase the pressure within the pressure accumulator (37) by means of the further hydraulic pump (53) and to drive the hydraulic motor (54) by means of the pressure accumulator (37), and wherein the hydraulic motor (54) is adapted to drive the hydraulic pump (9) and / or the drive unit (1). Vehicle (2) comprising a working hydraulic system (8) according to one of the preceding claims.

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