EP2308795B1 - Hydraulic device and method for operating same in a mobile work device - Google Patents

Description

The invention relates to a hydraulic device for a mobile work machine, in particular a truck, and a method for operating a hydraulic device of a mobile work machine, in particular an industrial truck. Above all, the invention relates to a hydraulic device for a mobile machine with an internal combustion engine, which is connected to a hydraulic pump, in particular a working hydraulic pump for supplying at least one consumer with pressure medium, from a pressure accumulator of the suction side of the hydraulic pump pressure medium can be fed. The invention also relates to a method for operating such a device, in which the hydraulic pump can operate as a hydraulic motor.

In mobile machines, especially industrial trucks, it is known to use a hydraulic drive system. The hydraulic drive system consists of a preferably controllable in the flow volume or controllable hydraulic pump, which is connected to a trained mostly as an internal combustion engine primary drive and supplies a working hydraulics with pressure medium. As drive can be provided in generic mobile work machines, a hydrostatic drive, comprising a hydraulic and driven by the engine drive drive pump and arranged on the driven wheels hydraulic traction motors, which are connected in a closed circuit with the traction drive pump. Alternatively, a Verbrennungsmotorischelektrischer traction drive, in which the internal combustion engine drives a generator for powering electric traction motors, and a hydrodynamic traction drive with a driven by the engine converter transmissions as traction drive in mobile machines known.

The consumers of the working hydraulics are, for example, load handling devices such as a fork on a mast for a forklift, for example a lifting drive, a .Neigeantrieb and possibly existing additional consumers, such as a side thruster. The trained as a working hydraulic pump hydraulic pump is in this case connected to the prime mover, such as the internal combustion engine, driving.

The internal combustion engine is usually used as fully equipped with all ancillaries engine in the mobile machine and therefore has usually for starting the engine on an electric starter, which is fed from a battery, which in turn is charged by a generator driven by the internal combustion engine.

It is known in the field of motor vehicles to combine the electric starter and the generator to form a component. These so-called start generators may e.g. be locked or integrated with the flywheel and be designed for higher performance. This hybrid concepts are possible in which a recuperation takes place. When braking the generator generates electricity that is stored in the battery and with increased power requirements, such as when accelerating, the starting generator acts in addition to its function when starting the engine as an auxiliary drive.

Such possibilities of a booster drive are of particular interest when the internal combustion engine is made smaller in its performance. A smaller internal combustion engine has less internal friction to overcome in operation and therefore lower fuel consumption. Moreover, it is more compact. However, to cover required power demand peaks, additional drive power is required.

It is also known to store energy in hydraulic systems in pressure accumulators.

Basically, in hybrid systems or recuperative systems of mobile machines, four combinations with short-term energy storage or long-term energy storage and use of a hydraulic or electrical system for energy storage can be distinguished.

When using an electrical system and a long-term energy storage electric, for example, in an internal combustion engine driven forklift, a recuperation of the braking energy can be implemented, but the system is very expensive. Usual long-term storage are additional Batteries that are significantly larger and therefore more expensive or heavier than the required for the start battery of the engine.

The combination of an electrical short-term memory and an electrical system, for example, with double-layer capacitors, as they are known as under the trade name "Ultracaps", implemented and used in addition to starting the engine for additional drive power as a booster. However, double-layer capacitors are currently not fully usable in vehicles permanently and reliably.

A combination of a hydraulic long-term storage and a hydraulic boost drive, wherein the hydraulic long-term storage is charged, for example as a pressure accumulator by recovering the braking energy is expensive and expensive. Corresponding accumulators would have to be able to store relatively large volumes of pressure medium, such as e.g. in the order of 1000 liters of pressure medium in order to be able to completely store the energy generated during braking. In this case, a fast charging in the short period of deceleration is required with the high volume flows occurring. Such a solution causes due to the complex accumulator high weight, a large volume of construction and especially high cost of the pressure accumulator and the pressure medium itself, which must meet relatively high quality standards.

In contrast, the requirements for an additional power or a boost drive in mobile machines and especially industrial trucks are often only of limited duration.

Such requirements can be implemented more with a combination of a hydraulic short-term storage and a hydraulic boost drive.

From the DE 32 47 335 A1 is a drive unit, preferably for a vehicle, with a primary energy source known, which may be, for example, an internal combustion engine, in which this primary energy source towing power can be fed. The drive unit has a hydrostatic drive and connected to the primary energy source auxiliary pump, wherein in the delivery line of the auxiliary pump a switchable in the braking state of the traction drive throttle is arranged.

Next is from the DE 32 47 335 A1 an embodiment is known in which in the braking state of the traction drive of the auxiliary pump via the switchable throttle pressure medium can be promoted in a pressure accumulator and the acceleration of the traction drive accumulator with the suction line of the auxiliary pump is connected, so that the auxiliary pump requires less drive power from the engine.

In a further embodiment, the pressure medium stored under pressure in the pressure accumulator during braking of the travel drive can be directly supplied to the consumers of the auxiliary pump.

From the EP 1 974 979 A2 a truck is known with Verbrennungsmotorischelektrischem traction drive, which has a connected to an internal combustion engine in operative connection hydraulic pump and connected to the engine and the hydraulic pump in operative connection rotary electric machine and an electric drive motor and a device for storing electrical energy. The rotating electric machine can be operated either as a motor or as a generator, for example when braking. In particular, at high power demand of the hydraulic pump, the rotating electrical machine is operable as a motor and electrical energy from the device for storing electrical energy to the rotating electric machine is transferable.

In one embodiment, from the EP 1 974 979 A2 known to operate the rotating electric machine as a starter for the internal combustion engine.

From the DE 10 2005 052 108 A1 is a generic hydraulic device known.

The present invention has for its object to provide an improved hydraulic system for a mobile work machine and a corresponding method for operation available, with the cost and energy can be saved.

This object is achieved by a hydraulic device for a mobile work machine having the features of independent claim 1 and by a method for operating a hydraulic device of a mobile work machine solved with the features of independent claim 12. Advantageous developments of the invention are specified in the subclaims.

The object is achieved by a hydraulic device for a mobile work machine, especially an industrial truck, with a drive and an internal combustion engine, which is connected to a hydraulic pump, in particular a working hydraulic pump working hydraulics, to supply at least one consumer with pressure medium solved. In the hydraulic device of a pressure accumulator suction side of the hydraulic pump pressure medium can be supplied, wherein the pressure accumulator is designed as a hydraulic short-term memory, which can be loaded at any time while driving the traction drive and stationary machine and in working mode of the working hydraulics of the mobile machine, the Hydraulic pump can also work as a hydraulic motor and the engine can start from a standstill.

Advantageously, this makes it possible to provide a boost function for a short-lasting additional power of the hydraulic device in addition to the internal combustion engine. In this case, the pressure accumulator while driving, with a stationary machine or in working independently and outside the periods of recuperation, for example, when braking the mobile machine or a way of energy recovery in the work hydraulics, for example, in the sink operation of a linear actuator, be charged. The loading of the pressure accumulator outside of the braking operation and lowering operation in normal driving, with stationary machine and working mode of the working hydraulics makes it possible to form the pressure accumulator as a hydraulic short-term memory with a small storage volume and to charge for a longer period with low charging currents. As a result, the construction cost and space requirements for the accumulator can be reduced. In the boost function for the traction drive, the hydraulic fluid pump is already supplied with the pressure medium under pressure. This reduces the power consumption of the working hydraulic pump needed to achieve the desired pressure for working hydraulics, and provides a higher power output of the internal combustion engine for driving the traction drive. As far as the working hydraulic pump is also designed so that it can also operate as a hydraulic motor, the traction drive can also be driven in addition to the internal combustion engine by the hydraulic pump to generate additional torque, resulting in the peak torque load of Internal combustion engine reduced. With the pressure accumulator according to the invention, which is charged during operation with a stationary machine and working mode of the working hydraulics with low charging currents, can thus with low construction costs support the acceleration of the engine during startup and acceleration during the driving operation and the operation of the working hydraulics, especially in the lifting operation of a lifting drive, and the peak torque demand of the internal combustion engine and the energy consumption of the internal combustion engine can be reduced. Advantageously, thereby the installation of an electric starter for the internal combustion engine can be avoided and with little effort can be made available by the hydraulic pump, which is also operable as a hydraulic motor, a very powerful starter drive. Further advantageously, this starting capability is also well suited for a start / stop system in which the internal combustion engine, when not needed, is turned off to avoid fuel consumption at idle. It is possible with respect to the starting device wear-free or low-wear frequent starting and also a start under load.

In a hydrostatic travel drive, the hydraulic pump of the traction drive and the hydraulic traction motors are usually integrated in a closed system, so that the boost function is advantageously indirectly via the hydraulic pump to prevent interference with the encapsulated and completed high-pressure system of the hydrostatic drive.

In a favorable embodiment, the loading of the accumulator depending on operating parameters, in particular of an expected imminent power demand on the hydraulic device and / or the pressure in the pressure accumulator, take place.

The charging of the accumulator can be done by an intelligent controller that evaluates information, such as the current state of charge of the accumulator, whether the mobile machine is stationary and therefore about to expect an acceleration, or whether the mobile work machine and therefore potentially the pressure accumulator when braking can be loaded.

In a favorable embodiment, the pressure accumulator can be charged by the hydraulic pump via a controllable charging valve.

Advantageously, the controllable charging valve can be controlled by a controller such that the pressure accumulator can be charged with a low pressure medium requirement of the at least one consumer.

As a result, the charging valve can always be opened when the consumers, which are supplied by the hydraulic pump with pressure medium, just have a low pressure medium requirement and a pressure medium delivery surplus of the hydraulic pump is present. In particular, even in a state of energy recovery in one of the hydraulic pump. pressurized working hydraulics, such as when lowering a raised load, the pressure accumulator are loaded. This is approximately advantageous in a forklift with its provided for load lifting and load handling and working at relatively high pressure working hydraulics possible.

In a favorable embodiment, the accumulator is rechargeable via a Zusatziadevorrichtung.

As a result, the pressure accumulator can be filled up in advance in the case of an expected requirement.

In a favorable embodiment, the additional charging device is a manual hydraulic pump.

A manual hydraulic pump allows an emergency start with empty accumulator, without tools such as a charger or jump start by another vehicle would be required. A manual hydraulic pump can be integrated with little effort and relatively inexpensive.

In an advantageous embodiment, the auxiliary charging device is a driven by an electric motor auxiliary hydraulic pump.

By a driven by an electric motor auxiliary hydraulic pump, which is already sufficient with a relatively low power for this, the pressure accumulator with low construction costs by a control regardless of the operating state of the hydraulic pump over a period of time while driving, with stationary machine and / or in working mode Working hydraulics are loaded.

Trained as a short-term memory pressure accumulator may have less than 5 liters of storage volume, in particular between 2 and 3 liters of storage volume and a maximum storage pressure of 200 to 300 bar.

A storage volume of the accumulator between 2 and 3 liters at a maximum accumulator pressure of 200 to 300 bar is a sufficiently large energy storage especially for starting the engine and supporting the engine when starting up as a power boost. Such designed as a pressure accumulator hydraulic short-term storage has a low space requirement and low costs.

In an advantageous embodiment, the accumulator is connected via a pressure reducing valve to a feed pressure medium circuit, in particular for supplying a hydraulic adjusting device in a hydraulic pump designed as a variable displacement pump.

As a result, a feed pressure supply can be ensured even when the internal combustion engine is stationary.

In a favorable embodiment, the connection of the accumulator with the suction side of the hydraulic pump by means of a control valve device is controllable.

The object is also achieved by a method for operating control of a hydrostatic device for a mobile work machine having the features of claim 13.

Advantageously, in a method for operating a hydraulic device for a mobile work machine with a drive, in particular a truck, the hydraulic device having a connected to a hydraulic pump, in particular a working hydraulic pump working hydraulics, internal combustion engine for pressure medium supply at least one consumer, from a pressure accumulator on the suction side the hydraulic pump pressure medium can be supplied and the hydraulic pump can operate as a hydraulic motor, driven to start the engine, the hydraulic pump with pressure medium from the pressure accumulator.

As a result, a starting possibility for the internal combustion engine can be provided in a simple manner.

In an advantageous embodiment of the method is supplied from an accumulator of the suction side of the hydraulic pump pressure medium at increased power demand to cause a torque boost or a short-term increase in performance, especially in the operation of the working hydraulics and / or the traction drive. With the pressure accumulator according to the invention, designed as a hydraulic short-term memory accumulator thus the startup of the engine can be assisted during startup as well as the operation of the working hydraulics and the peak torque demand of the engine can be reduced, whereby the engine can be reduced in power and a reduced noise level can be achieved.

The accumulator is designed as a hydraulic short-term memory and can be loaded during the driving operation, with the work machine stationary and during the working operation of the mobile working machine.

In a favorable embodiment, the method uses a previously described hydraulic device for a mobile working machine, resulting in the advantages already described.

The traction drive can drive the hydraulic pump when braking the mobile work machine and the controllable charging valve are controlled by a controller so that the pressure accumulator is loaded during braking.

Fig. 1

ein Schaltbild eines ersten Ausführungsbeispiels einer erfindungsgemäßen hydraulischen Vorrichtung und

Fig. 2

ein Schaltbild eines zweiten Ausführungsbeispiels einer erfindungsgemäßen hydraulischen Vorrichtung.

Further advantages and details of the invention will be explained in more detail with reference to the embodiments illustrated in the schematic figures. This shows

Fig. 1

a circuit diagram of a first embodiment of a hydraulic device according to the invention and

Fig. 2

a circuit diagram of a second embodiment of a hydraulic device according to the invention.

The Fig. 1 shows a circuit diagram of a first embodiment of a hydraulic device according to the invention. A hydraulic pump 1, which is designed as a variable displacement in the variable displacement pump, in particular electro-hydraulically adjustable variable, sucks pressure medium from a pressure medium tank 2 via a check valve designed as a check valve 3 and conveys the pressure medium in a connected to a working hydraulics 9 feed line, the here not shown consumers, such as a lifting drive of a mast on a truck, a tilt drive of the mast or other additional consumers supplied with pressure medium. The hydraulic pump 1 is drivingly connected to the drive with an internal combustion engine 13.

According to the invention designed as a hydraulic short-term memory pressure accumulator 4 is provided with a storage volume of about 3 liters and a storage boost pressure in the range of 200-300 bar, which is connected via a formed as a two-way valve 5 control valve 6 with a suction side 7 of the hydraulic pump 1 and the suction side 7 of the hydraulic pump 1 supplied under pressure pressure medium.

By means of a controllable charging valve 8, the pressure accumulator 4 can be charged from the delivery flow of the hydraulic pump 1 or a charging valve device of the working hydraulics 9 by a control, not shown. Alternatively, a shop the accumulator 4 via a manually operated hydraulic pump 10 or driven by an electric motor 11 auxiliary hydraulic pump 12 possible.

The charging of the pressure accumulator 4 takes place when the working machine is stationary, during the driving operation of the traction drive and / or during the working operation of the working hydraulics 9, so that charging can take place over a relatively long period of time with low charging currents.

The controllable charging valve 8 is opened, for example, when the consumers who are supplied by the hydraulic pump 1 in the working hydraulics 9 with pressure medium, just have a low pressure medium requirement and a pressure medium delivery surplus of the hydraulic pump 1 is present and continue the pressure accumulator 4 empty and a Additional service requirement is to be expected. In the event of a subsequent high power requirement of the working hydraulics 9, pressure medium can be supplied via the control valve device 6 from the pressure accumulator 4 to the suction side 7 of the hydraulic pump 1.

By designed as a short-term memory pressure accumulator 4, it is possible for a short period of time that the hydraulic pump 1 with unchanged power from the engine 13 at the same delivery pressure in the working hydraulics 9 a larger volume and thus provide a power boost, for example in the lifting operation of the linear actuator available can. When the internal combustion engine 13 is further connected to a traction drive, not shown, and the hydraulic pump 1 can operate as a hydraulic motor, by supplying pressure medium via the control valve device 6 from the pressure accumulator 4 to the suction side 7 of the hydraulic pump 1 in an acceleration phase and when starting the mobile Working machine of the drive are driven in addition to the drive power by the engine 13 and serve the boost function for accelerating and starting the mobile machine.

The working as a hydraulic motor hydraulic pump 1 also serves as a starter for the engine 13. It is made possible by the manual hydraulic pump 10 as additional charging an emergency start with empty accumulator 4 by the pressure accumulator 4 is charged manually. One driven by an electric motor 11 Auxiliary hydraulic pump 12 as an auxiliary charging device allows loading of the pressure accumulator 4, regardless of the operating state of the working hydraulics. 9

With the pressure accumulator 4 according to the invention, designed as a short-term memory, the run-up of the internal combustion engine 13 during start-up, during acceleration and during the actuation of a consumer of the working hydraulics 9 can be supported. Peak torques are effected in the boost mode and stalling of the internal combustion engine 13 is avoided. By a possible reduction of the maximum power of the internal combustion engine 13 and the elimination of an electric starter, the construction cost of the prime mover can be reduced.

The Fig. 2 shows a circuit diagram of a second embodiment of a hydraulic device according to the invention, wherein the embodiment of the Fig. 1 identical components are designated by the same reference numerals. The trained as a variable displacement hydraulic pump 1 is connected to the engine 13 and is adjusted by a hydraulic adjusting device 14 in the delivery volume. The hydraulic pump 1 sucks pressure medium from the pressure medium tank 2 via the check valve 3 and promotes the pressure medium in the leading to the working hydraulics 9 delivery line. From the accumulator 4 can be supplied via the form of a two-way valve 5 control valve means 6 of the suction side 7 of the hydraulic pump 1 under pressure pressure medium. With the internal combustion engine 13, a feed pressure pump 15 is further connected, which provides the control pressure for the hydraulic adjusting device 14 in a feed pressure center circuit 16. The feed pressure is ensured by a pressure relief valve 17. Via the control valve device 6 and a pressure reducing valve 18, the pressure medium circuit 16 pressure medium from the pressure accumulator 4 are supplied. The feed pressure medium circuit 16 can furthermore be used as a control pressure supply for hydraulically actuated control valves of the working hydraulics and / or as a brake release pressure of a parking brake configured as a spring-loaded brake, for example. In a hydrostatic drive in a closed circuit can be supplied from the control pressure medium circuit, a feed device with pressure medium and an adjusting device of the pump of the traction drive.

As a result, the feed pressure in the feed pressure center circuit 16 can be maintained at standstill of the internal combustion engine 13 from the pressure accumulator 4 and For example, the hydraulic adjusting device 14 of the hydraulic pump 1 are operated even when the internal combustion engine 13. This is of particular advantage when the hydraulic adjusting device 14 has to be adjusted so that the hydraulic pump 1, which also operates as a hydraulic motor, should start the internal combustion engine 13.

Claims (16)

1. Hydraulic apparatus for a mobile machine, in particular an industrial truck, having a traction drive, an internal combustion engine (13) which is connected to a hydraulic pump (1), in particular a hydraulic work pump of a hydraulic work system, for supplying at least one consumer with pressure medium, it being possible for pressure medium to be fed from a pressure accumulator (4) to the suction side (7) of the hydraulic pump (1), characterized in that the pressure accumulator (4) is configured as a hydraulic short-term accumulator and can be charged at any time during driving operation of the traction drive, when the mobile machine is at a standstill and during working operation of the hydraulic work system of the mobile machine, it also being possible for the hydraulic pump (1) to operate as a hydraulic motor and to start the internal combustion engine (13) from a standstill.
2. Hydraulic apparatus according to Claim 1, characterized in that the charging of the pressure accumulator (4) can take place in a manner which is dependent on operating parameters, in particular on an imminent performance requirement to be expected of the hydraulic apparatus and/or the pressure in the pressure accumulator (4).
3. Hydraulic apparatus according to Claim 1 or 2, characterized in that the pressure accumulator (4) can be charged by the hydraulic pump (1) via a controllable charging valve (8).
4. Hydraulic apparatus according to Claim 3, characterized in that the controllable charging valve (8) can be actuated by a controller in such a way that the pressure accumulator (4) can be charged in the case of a low pressure medium requirement of the at least one consumer.
5. Hydraulic apparatus according to one of Claims 1 to 4, characterized in that the pressure accumulator (4) can be charged via an additional charging apparatus.
6. Hydraulic apparatus according to Claim 5, characterized in that the additional charging apparatus is a manual hydraulic pump (10).
7. Hydraulic apparatus according to Claim 5 or 6, characterized in that the additional charging apparatus is an auxiliary hydraulic pump (12) which is driven by an electric motor (11).
8. Hydraulic apparatus according to one of Claims 1 to 7, characterized in that the pressure accumulator (4) has a storage volume of less than 5 litres, in particular a storage volume of between 2 and 3 litres.
9. Hydraulic apparatus according to one of Claims 1 to 8, characterized in that the pressure accumulator (4) has a maximum accumulator pressure of from 200 to 300 bar.
10. Hydraulic apparatus according to one of Claims 1 to 9, characterized in that the pressure accumulator (4) is connected via a pressure reducing valve (18) to a feed pressure medium circuit (16), in particular for supplying a hydraulic adjusting apparatus (14) in the case of a hydraulic pump (1) which is configured as a variable displacement pump.
11. Hydraulic apparatus according to one of Claims 1 to 10, characterized in that the connection of the pressure medium accumulator (4) to the suction side (7) of the hydraulic pump (1) can be controlled by means of a control valve device (6).
12. Method for operating a hydraulic apparatus for a mobile machine having a traction drive, in particular an industrial truck, the hydraulic apparatus having an internal combustion engine (13) which is connected to a hydraulic pump (1), in particular a hydraulic work pump of a hydraulic work system, for supplying at least one consumer with pressure medium, it being possible for pressure medium to be fed from a pressure accumulator (4) to a suction side (7) of the hydraulic pump (1) and for the hydraulic pump (1) to operate as a hydraulic motor, and the hydraulic pump (1) being driven by way of pressure medium from the pressure accumulator (4) in order to start the internal combustion engine (13).
13. Method according to Claim 12, characterized in that pressure medium is fed from a pressure accumulator (4) to the suction side (7) of the hydraulic pump (1) in the case of an increased performance requirement, in order to bring about a torque boost, in particular in the case of the actuation of the hydraulic work system and/or the traction drive.
14. Method according to either of Claims 12 and 13, characterized in that the pressure accumulator (4) is configured as a short-term accumulator and is charged during driving operation, when the mobile machine is at a standstill and during working operation of the mobile machine.
15. Method according to one of Claims 12 to 14 using a hydraulic apparatus according to one of Claims 1 to 11.
16. Method according to Claim 15 using a hydraulic apparatus according to Claim 3, characterized in that the traction drive drives the hydraulic pump (1) during braking of the mobile machine, and the controllable charging valve (8) is actuated by a controller in such a way that the pressure accumulator (4) is charged during braking.

Images