Vehicle having a drive engine/motor for driving a locomotive drive and a working hydraulic system

The invention relates to a vehicle having a drive motor for driving a traction drive for driving and at least one working hydraulics.

In vehicles or commercial vehicles, it is the rule that it provides only for a prime mover, with the different loads of the vehicle be driven. In particular, it is common to provide a single diesel engine. In the case of several different functions, such as a drive system and an additional working hydraulics, the emitted by the diesel engine power is branched. The respective buyers is thereby allocated according to a specified control strategy, a portion of the total available capacity of the diesel engine. This leads, for example, for short-term occurrence of load peaks in a decrease in engine speed. Trucks and heavy equipment, such as forklifts, loaders or garbage trucks are often accelerated to low speed and then decelerated to a stop. At the same time or in the occurring driving breaks work is done with the working hydraulics. In order to use the heat released during braking energy, it is from the<patcit id="pcit0001" dnum="DE3235825A1"><text>DE 32 35 825 A1</text></patcit> known to provide a means for storing energy.

In the out of <patcit id="pcit0002" dnum="DE3235825A1"><text>DE 32 35 825 A1</text></patcit> known vehicle is connected to a prime mover via a code converter having a drive axle. The output shaft of the prime mover is coupled to a power take-off which is connected via a clutch and a freewheel to a working hydraulic system. With the working hydraulics is connected via a further clutch a hydraulic machine can be coupled, which is connected via a line to a memory. This can convert the kinetic energy of the vehicle into storable energy pressure in closing the appropriate couplings the hydraulic machine in the shift operation of the vehicle. Should no one occurring shift operation of the memory to be reloaded, so a drive of the hydraulic machine indirectly via the PTO and the couplings is possible.

In the proposed vehicle, it is disadvantageous that the activation of the hydraulic machine must be consuming a split transmission and at least one clutch. This not only increases the losses when saving the energy, so that only a part of the braking energy can be stored in the memory, but also increases at a recovery of the stored energy again the losses. In any case, it is necessary to drag the working hydraulic system in the recovery of energy, which despite not using the hydraulics significant losses. In an alternative embodiment can be carried out by bypassing the working device, a coupling to the drive axle of the vehicle. However, an additional transfer transmission is required to achieve a speed adaptation of the hydraulic machine.

<patcit id="pcit0003" dnum="DE4333564A1"><text>DE 43 33 564 A1</text></patcit> shows a vehicle according to the preamble of claim 1.

<patcit id="pcit0004" dnum="WO8803123A1"><text>WO 88/03123 A1</text></patcit> shows a hydraulic working circuit consisting of two hydraulic machines for operating auxiliary units without direct coupling of hydraulic machines with a traction drive.

<patcit id="pcit0005" dnum="EP1433648A2"><text>EP 1433648 A2</text></patcit> shows a drive with a known arrangement of pumps and storage.

The invention is based is to provide a vehicle with a simple way to store energy and transfer the energy between at least one working hydraulics and drive system on the object.

The object is solved by the vehicle with the features of claim 1.

The vehicle of the invention has a drive motor for driving a traction drive and for driving at least one hydraulic work or a hydraulic working circuit. Further, the vehicle comprises a hydraulic accumulator which is connected to a hydraulic machine. The working hydraulic system comprises a hydraulic pump. The hydraulic machine is connected to a connecting the drive motor to the traction drive output shaft. The hydraulic unit is directly coupled to the drive system. The drive motor is connected via the hydraulic pump, which is connected to the output shaft and directly connected to the drive with the working hydraulics.

The vehicle has the advantage that the coupling of the hydraulic machine carried on the output shaft of the motor with the traction drive, where the moment of the drive motor is coupled to the drive mechanism. This has the advantage that the flow of force is unchanged, regardless of whether the generated torque due to the stored energy is present, or due to a drive by the drive motor. Furthermore, it is advantageous that the hydraulic machine is coupled for charging the accumulator directly connected to the traction drive. An elaborate power passing through a PTO or a transfer gearbox can be omitted.

In the dependent claims, advantageous refinements are made.

In particular, it is advantageous to connect the hydraulic unit for storing a low-pressure accumulator and a high pressure accumulator. Such a compound with a low-pressure accumulator and a high pressure accumulator has the advantage that, also on the suction side of the hydraulic machine through the low-pressure accumulator, a minimum pressure can be maintained always. During suction of pressure medium thus the occurrence of cavitation is prevented. The low-pressure accumulator and the high-pressure reservoir to a hydraulic cooperate cradle. By maintaining a minimum pressure on the suction side of the hydraulic machine also such hydraulic machines can be used which are problematic when sucking pressure medium from a pressure-free tank volume.

According to a preferred embodiment of the traction drive of the vehicle is constructed as a hydrostatic transmission. The forming of the drive mechanism as a hydrostatic transmission has in cooperation with the storage of energy in a hydraulic machine which can be filled via a memory has the advantage that during a braking operation a continuous change of the transmission can be carried out in the hydrostatic transmission. This can be one hand, the braking force individually adjusted, on the other hand, the speed at which the hydraulic machine is operated to adjust. With a customized speed allows the hydraulic machine to save energy operate in a particularly preferred rpm range, which in turn can reduce the losses. One result is an efficient storage of the released braking energy.

It is further advantageous for the hydraulic machine as an adjustable hydrostatic piston engine. By adjusting the absorption volume of the hydraulic machine during braking can also vary the braking power. In particular, it is advantageous to use a hydrostatic transmission as a propulsion and additionally execute the hydrostatic piston engine adjustable. With proper control of the transmission ratio of the hydrostatic transmission and the absorption volume of the hydraulic machine is therefore a particularly efficient use of the available kinetic energy of the vehicle can be achieved.

Furthermore, it is advantageous to provide a working hydraulic system, which comprises at least one working in a closed circuit hydraulic pump. When using a working in a closed circuit hydraulic pump not only the heat released by the traction drive during vehicle braking energy can be used, but it is also possible the hydraulic machine for storing energy to drive through the working hydraulics. For example, a double-acting lifting cylinder connected to a hydraulic pump in a closed circuit of working hydraulics, so can be driven when lowering a load, the hydraulic pump for the working hydraulics. Which then acts as a hydraulic motor hydraulic pump then drives the mechanical hydraulic machine, which in turn promotes the pressure medium into the memory. This regenerative use of energy is possible from both the traction drive in the direction of the working hydraulics as well as of the working hydraulics in the direction of travel drive. The stored energy can be used in the same circle, so the working hydraulics or the traveling drive again.

Furthermore, it is advantageous to design the hydraulic machine uncoupled. In the arrangement of the hydraulic machine, which is coupled to a connecting the drive motor to the traction drive shaft according to the invention, such a disconnectable arrangement is particularly advantageous. For example, in the completely filled memory when entrainment of the hydraulic machine for example, would result in churning losses, the hydraulic machine can be uncoupled. A coupling is required at any time possible, provided that a recovery of the energy is required. In the intervening period in which, for example, a transfer drive is carried out at a constant speed, on the other hand gives the uncoupled hydraulic machine no losses.

Preferred embodiments of the vehicle according to the invention are shown in the drawing and are explained in the following description. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic representation illustrating the arrangement of the invention;</dd><dt>FIG. 2</dt><dd>a schematic representation of a first embodiment of a vehicle according to the invention and</dd><dt>Fig. 3</dt><dd>a schematic representation of a second embodiment of a vehicle according to the invention.</dd></dl>

In the <figref idrefs="f0001">Fig. 1</figref> are first of all the essential components of a vehicle with a hydraulic working circuit and a drive system shown. The vehicle 1 has a shared by the elements to be driven drive motor. 2 The drive motor 2 drives the vehicle by driving a drive axle. 3 In order to additionally operate more tools to the driving tasks, the drive motor 2 is connected to a hydraulic working circuit. 4

The drive motor 2 transmits its output torque through an output shaft 5 to a vehicle drive 6 which acts on a differential gear 8 of the drive shaft 3 via a vehicle drive shaft. 7 The differential gear 8 is 'connected with the driven vehicle wheels 10, 10' with a first half shaft 9 and a second half-wave 9 are connected. The vehicle drive 6 may be performed in any manner. In particular, it may be designed as a purely mechanical drive, so that the vehicle drive 6 preferably consists of a mechanical transmission. On the input side, a separating clutch is provided at the vehicle drive 6 in this case. The travel drive 6 can also be designed as an automatic gearbox which is connected via a hydrodynamic torque converter to the output shaft fifth For simplicity's<figref idrefs="f0001">Fig. 1</figref> only represented a driven vehicle axle. 3 However, it is also possible that the drive system 6 includes a transfer case of a four-wheel drive.

In the illustrated embodiment, the hydraulic working circuit 4 is an open circuit. If the vehicle 1 is braked, so there is a shift operation due to inertia. The on the vehicle wheels 10, 10 'initiated torque is opposite to a normal driving on the half shaft 9, 9' continued, the differential gear 8 and the vehicle output shaft 7 and the vehicle drive 6 through to the output shaft. 5 At ordinary vehicles without a memory device, this is supported on the output shaft 5 executed led to the drive motor 2 torque on the drive motor 2nd For a drive with energy recovery is, as in the<figref idrefs="f0001">Fig. 1</figref> a memory is shown, 11 provided for storing pressure energy. The memory 11 is equipped with a compressible volume, so that a pressure medium under compression of the compressible volume can be conveyed into the memory eleventh In order to enable a delivery of pressure medium, a hydraulic machine 12 is provided, which is connected to the output shaft of the fifth The hydraulic machine 12 conveys pressure medium via an accumulator line 13 in the memory 11. The pressure medium is drawn in via a suction line 14 from a tank volume 15th The hydraulic unit 12 is preferably designed adjustable. The adjustable hydrostatic piston engine is provided for delivery of pressure medium in two directions and can be operated as a pump as well as during the recovery of the stored energy as a hydraulic motor. In the recovery of the stored energy the pressurized pressure medium is supplied from the memory 11 via the accumulator line 13 of the hydraulic engine 12. The hydraulic machine 12 then acts as a hydraulic motor and generated by relaxation of the pressure medium, a torque, which is transmitted from the hydraulic machine 12 to the output shaft fifth

The transmitted to the output shaft torque can be 5 used in the same way as it would be possible at a production by the drive motor 2nd This means that the torque generated by the energy recovery can be provided to both the vehicle drive and the hydraulic Arbeitskreisläuf available. The hydraulic working circuit 4 also includes an adjustable hydraulic pump 17. The adjustable hydraulic pump 17 is also provided for funding in both directions. The hydraulic pump 17 draws via a second suction line 16 from another tank volume 15 'pressure medium and delivers this via a working line 18 to a working hydraulic system 19. In the illustrated embodiment, the hydraulic working circuit 4 is designed as an open circuit.

In the <figref idrefs="f0002">FIG. 2</figref> is shown a further embodiment of the vehicle according to the invention. The with the<figref idrefs="f0001">Fig. 1</figref> matching features will not be described again to avoid repetition, and are <figref idrefs="f0002">FIG. 2</figref> provided with the same reference numerals. The hydraulic working circuit 4 is in contrast to the hydraulic working circuit 4<figref idrefs="f0001">Fig. 1</figref> designed as a closed circuit. The hydraulic pump 17 is thus connected to a first working line 20 and a second working line 21st The working lines 20 and 21 are connected to a double-acting hydraulic cylinder 19 'and open there into a first pressure chamber 22 and in a second pressure chamber 23rd The first pressure chamber 22 and the second pressure chamber 23 are arranged in the hydraulic cylinder 19 on different sides of a piston 24th In consequence of the pressure difference between the first pressure chamber 22 and the second pressure chamber 23 results in a displacement of the piston 24. The piston movement of the piston 24 is transmitted via a piston rod 25, for example, on a boom of an excavator or a lift arm of a wheel loader. Due to the piston rod 25 there is a difference between the supplied and the displaced volume in the pressure chambers 22, 23. To compensate the difference in volume of the first working line 20 and the second working line 21 are connected to each other through a valve block 26th The valve block 26 permits necessary to compensate for the difference volume flow. In the illustrated form a closed circuit, the hydraulic circuit 6 may also include a separate energy storage device in the form of a further hydraulic accumulator.

The vehicle drive 6 is provided with a second embodiment of the <figref idrefs="f0002">FIG. 2</figref> designed as a hydrostatic transmission. The hydrostatic transmission comprises a hydraulic pump 30, which is adjustable and is provided for conveying in two directions. Via a first transmission line 31 and a second transmission line 32, the hydrostatic pump 30 is coupled to a hydraulic motor 33rd In the illustrated embodiment of<figref idrefs="f0002">FIG. 2</figref> is the hydraulic motor 33 designed as a fixed-displacement motor, which can be flowed through in two directions. For other programs, such as the feeding of pressure medium in the after starting the vehicle initially unpressurized circulation of the drive mechanism 6, a feed pump 34 is provided. The feed pump 34 is the same as the pump 30 and the hydrostatic piston engine 17 of the hydraulic working circuit 4 connected to the output shaft. 5

A third embodiment is in the <figref idrefs="f0003">Fig. 3</figref> shown. The traction drive 6 and the hydraulic working circuit 4 corresponds to the embodiment of the<figref idrefs="f0002">FIG. 2</figref>, In addition to the designed as a high-pressure storage reservoir 11, which is provided for storing braking energy, is in the embodiment of<figref idrefs="f0003">Fig. 3</figref> a second memory 35 is provided. The second memory 35 is connected to the suction line 14 '. Accordingly, no longer sucks the hydraulic machine 12 during the storing of pressure energy in the memory 11 pressure medium from a tank volume which is pressureless in the rule, to but from a second memory 35. The second memory 35 is designed as a low-pressure accumulator. In the spread-out low-pressure accumulator as second memory 35 prevails a slight overpressure, so that even when sucking a large volume flow in each case a sufficient inlet pressure exists to cavitation on the suction side of the hydraulic machine to avoid 12th This allows the use of hydraulic machines, which are not suitable due to their low suction to automatically suck from an unpressurized tank volume leverage.

The described embodiments make it possible to store both by the braking of the vehicle 1 by the drive unit 6 as well, for example during the lowering of a load on the hydraulic circuit 4 the energy released in the memory 11, which is designed as a high-pressure accumulator. The energy stored there can be recovered by means of operating in reverse the hydraulic machine 12, which then acts as a motor then. The torque generated by the hydraulic machine 12 is as well as the torque of the engine 2 provided on the output shaft 5 is available., Through the available at the output shaft 5 torque the power flow is in both the traction drive 6 as well as in the hydraulic circuit 4 compared with a production the torque unchanged by the drive motor 2nd

The invention is not limited to the embodiments illustrated. In particular, different combinations of individual features of the different embodiments are conceivable.