EP2237981A2

EP2237981A2 - Drive system

Info

Publication number: EP2237981A2
Application number: EP08867708A
Authority: EP
Inventors: Matthias Müller; Peter Schmuttermair
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-12-28
Filing date: 2008-12-22
Publication date: 2010-10-13
Also published as: US20100300085A1; WO2009083223A2; WO2009083223A3; DE102007062889A1

Abstract

The invention relates to a drive system (1) having a travel drive, a working hydraulic system (3) and a device for hydrostatic braking (4). The device for hydrostatic braking has a first hydrostatic piston machine (12) which is connected to a drive train (2), wherein the first hydrostatic piston machine (12) is connected via an accumulator line (14) to a pressure accumulator (15) and the accumulator line (14) is connected via an accumulator pressure line (16) to the working hydraulic system (3). As an alternative, the drive system (100) additionally has a second hydrostatic piston machine (13) which is connected mechanically to the first hydrostatic piston machine (12), wherein the first hydrostatic piston machine (12) is connected in the closed circuit via the accumulator line (14) to the pressure accumulator (15), and the second hydrostatic piston machine is connected in the open circuit via a working line (16) to the working hydraulic system (3).

Description

drive system

The invention relates to a drive system for the storage and reuse of hydraulic energy and the exchange of energy between a drive train and a working hydraulics.

From the published patent application DE 32 35 825 Al a vehicle for at least one operation during at least one holding time is shown. The vehicle includes a mechanical main drivetrain, working hydraulics and a hydrostatic braking device. The device for hydrostatic braking comprises a first hydrostatic device which can be mechanically connected to the mechanical main drive train via a clutch and a second hydrostatic device which can be mechanically connected to the first hydrostatic device. The first hydrostatic device is connectable via a storage line with a pressure accumulator. The second hydrostatic device can be connected to the working hydraulics via a working line. The vehicle can take energy from the main driveline and store it in the accumulator. In this case, the energy of the engine or the kinetic energy of the vehicle can be removed. Energy stored in the pressure accumulator can be supplied to the main drive train and / or indirectly to the working hydraulics. Energy from the main drive train is fed into the accumulator via the first and second hydrostatic devices. Energy from the accumulator is also fed through the first and the second hydrostatic device in working hydraulics. Energy stored in the pressure accumulator is supplied to the main drive train via at least one hydrostatic device.

In the proposed vehicle, it is disadvantageous that

Energy from the pressure accumulator is supplied only in holding times of the working hydraulics. The working hydraulics will therefore not supported by the accumulator outside the holding times. The stored energy is not reused outside the holding times in the working hydraulics. The proposed vehicle has the further disadvantage that the energy from the pressure accumulator of the working hydraulics is supplied only indirectly via the second hydrostatic device. As a result of this detour unnecessary energy losses occur during energy transfer from the accumulator to the working hydraulics. The hydrostatic devices flowed through by pressure medium in this energy transfer rotate and thereby generate friction and frictional heat. In addition, the two hydrostatic devices are not available for independent functions during this energy transfer.

The invention has for its object to provide a drive system which allows to supply energy stored outside of holding times with low energy losses of a working hydraulics.

The object is achieved by the drive system with the features of claim 1.

The drive system according to the invention has a travel drive, a device for hydrostatic braking and a working hydraulics. The traction drive includes a drive train. The device for hydrostatic braking has a first hydrostatic piston machine connected to the drive train and a pressure accumulator. The first hydrostatic piston engine is connected via a storage line to the first pressure accumulator. The working hydraulics are connected via a storage pressure line to the storage line. The drive system according to the invention has the advantage that an energy transfer from the drive train into the pressure accumulator and into the working hydraulics is possible in each case via only a single hydrostatic piston engine. The energy from the powertrain can drive energy or Be braking energy. As a result, there is the advantage that energy can be conveyed from the drive train into the working hydraulics even outside holding times. The drive system according to the invention also has the advantage that an energy transfer from the accumulator to the working hydraulics without detour via two hydrostatic piston machines directly on the storage pressure line is possible. As a result, unnecessary energy losses, which arise due to friction caused by rotation of a hydrostatic piston engine, are avoided. Due to the direct connection between pressure accumulator and working hydraulics, an efficient transfer of energy from the accumulator to the working hydraulics is possible even outside holding times.

In the dependent claims advantageous embodiments of the drive system according to the invention are shown.

Preferably, the first hydrostatic piston machine is designed as an adjustable hydraulic pump. The first hydrostatic piston machine form as adjustable hydraulic pump has the advantage that the delivery volume of the first hydrostatic piston engine can be adjusted so that a simultaneous energy transfer from the first hydrostatic piston engine and from the pressure accumulator in the working hydraulics is possible. The pressure accumulator is emptied more slowly by the contribution of the first hydrostatic piston engine. This avoids unnecessarily lowering the pressure in the accumulator. Thus, longer energy in the pressure accumulator can be stored and / or removed from this. The pressure accumulator can thus be used more efficiently and the primary drive source can be operated in an improved efficiency range. The simultaneous transfer of energy from the first hydrostatic piston engine and from the pressure accumulator into the working hydraulics has the advantage that at the same time an energy supply from the drive train and from the pressure accumulator is used. This makes it possible to save the energy reserves in the accumulator and at the same time to use excess energy from the powertrain. Such excess energies occur in the drive train, for example during braking. These may also occur at a time when the prime mover supplies more power to the powertrain than it needs to drive the vehicle at that time.

Furthermore, it is advantageous to design the first hydrostatic piston machine as a hydraulic pump which can be swung out in opposite directions via a zero position. Thus, it is possible over a zero position in opposite directions swing-out hydraulic pump, in the same direction of rotation adjustable in opposite directions to promote pressure medium or vice versa rotate in the same direction adjustable in opposite directions. As a result, the conveying direction ratio can be reversed via a common shaft of connected hydraulic pumps with a constant direction of rotation of the shaft.

In a preferred embodiment, a second hydrostatic piston engine is mechanically connected to the first hydrostatic piston engine and connected to the working hydraulics via a working pressure line. The second piston machine is preferably also adjustable and in particular designed for operation in two directions of delivery. The adjustability of at least one hydrostatic piston engine has the further advantage that the delivery volume ratio between the two hydrostatic piston engines is adjustable. As a result, a variable pressure ratio is possible. It can promote the second hydrostatic piston engine pressure medium in the working hydraulics. The energy required for this purpose is taken from the second hydrostatic piston engine by the drive train and / or the pressure reservoir via the first hydrostatic piston engine.

In an advantageous embodiment, a storage pressure retaining valve is formed in the storage line. With this memory pressure holding valve unnecessary emptying of the accumulator is prevented. This ensures that energy stored in the pressure accumulator does not escape at an unfavorable time beyond the accumulator pressure retention valve.

Particularly preferably, the accumulator pressure holding valve is designed in its basic position as a non-return valve opening onto the pressure accumulator. As a result, in the basic position of the accumulator pressure retaining valve pressure medium and energy can be conveyed via the accumulator pressure holding valve in the energy storage, but not escape in the opposite direction.

In an advantageous embodiment, a pressure relief valve is formed in the accumulator pressure line. By this pressure limiting valve, a first pressure limit value is predetermined, which must be exceeded in the pressure accumulator, so that the pressure accumulator can empty via the pressure relief valve. As a result, it is the accumulator until a certain degree of filling or from a certain pressure possible to deliver energy and pressure medium to the working hydraulics.

Furthermore, it is advantageous to form this pressure relief valve as a controllable pressure relief valve. As a result, the first pressure limit value can be adjusted and dynamically adapted to the requirements. This allows optimum operation of the pressure accumulator and the working hydraulics.

In a preferred embodiment, the storage pressure line between the pressure relief valve and working hydraulics is connected via a tank line to a tank, wherein in the tank line, a further pressure relief valve is formed. Through the tank line, the accumulator pressure line can be relaxed in a range between pressure relief valve and working hydraulics. The further pressure relief valve sets a second Pressure limit, which must be exceeded in this area of the storage pressure line, so that relaxes the area of the storage pressure line into the tank. As a result, a maximum pressure is set for this area of the accumulator pressure line and it is prevented that the working hydraulics are overloaded by the drive system. In addition, hydraulics can continue to be braked even when the accumulator is full.

In an advantageous embodiment, the storage pressure line between the branch of the tank line and the working hydraulics is connected to a shuttle valve, which connects the working hydraulics with another pressure medium source or with the branch. As a result, the working hydraulic pressure medium and energy from the drive train, the accumulator or alternatively from the further pressure medium source can be supplied. Thus, the working hydraulics can be supplied with pressure medium and energy even if the drive train and the pressure accumulator do not provide sufficient energy or pressure medium.

The object is also achieved by the drive system with the features of claim 12.

The drive system includes a traction drive, a hydrostatic braking device and a working hydraulics. The traction drive includes a drive train. The device for hydrostatic braking comprises a first hydrostatic piston engine connected to the drive train via a clutch and a second hydrostatic piston engine mechanically connected to the first hydrostatic piston engine. The first hydrostatic piston engine is connected via a storage line with a pressure accumulator and via a further storage line with a further pressure accumulator. The second hydrostatic piston engine is connected via a working line with the working hydraulics. The first hydrostatic piston engine is in a closed Circuit and the second hydrostatic piston engine arranged in an open circuit. The drive system according to the invention has the advantage that it can promote energy and pressure medium in the working hydraulics outside of holding times. The drive system according to the invention also has the advantage that it can also promote stored energy in the working hydraulics and, in particular, simultaneously in the drive train outside holding times, wherein pressure transmission is possible. Another advantage of the drive system according to the invention is that it can promote stored energy in the working hydraulics regardless of the operating state of the drive train.

Advantageous embodiments of the alternative drive system according to the invention are shown in the subclaims.

Preferably, the first hydrostatic piston engine and / or the second hydrostatic piston engine is an adjustable hydraulic pump. As a result, the delivery volume ratio between the two hydrostatic piston engines is variably adjustable. This allows a variable pressure ratio. If one of the pressure accumulators is full, the delivery volume of the first hydrostatic piston engine can be set to zero in order to avoid overloading the full pressure accumulator. When emptying the pressure accumulator having the higher pressure into the pressure accumulator having the lower pressure, the first hydrostatic piston engine generates a torque. This torque can be variably adjusted via the first hydrostatic piston engine via the delivery volume. If the delivery volume is pivoted to zero, the torque disappears. Due to the adjustability of the second hydrostatic piston engine, the pressure medium delivery can be controlled variably in the working hydraulics. The pressure at which the second hydrostatic piston engine depresses the working hydraulics is for a given torque with which the second hydrostatic piston engine is driven, via the delivery volume variably adjustable.

The first hydrostatic piston machine and / or the second hydrostatic piston machine are particularly preferably a hydraulic pump which can be swiveled out in opposite directions via a zero position. As a result, the conveying direction ratio of the hydraulic pumps connected via a common shaft can be reversed with a constant direction of rotation of the shaft. It is advantageously not only the amount of delivery volume ratio between the two hydraulic pumps adjustable, but also the sign. This makes it possible to simultaneously transfer energy from the powertrain to a pressure accumulator and to the working hydraulics. It is also possible to supply energy from a pressure accumulator simultaneously to the drive train and the working hydraulics. In particular, it is possible to switch between energy storage and energy reuse, without having to change the direction of rotation of the shaft common to the hydraulic pumps.

Preferably, the pressure accumulator is designed as a high-pressure accumulator and the further pressure accumulator as a low-pressure accumulator. As a result, a closed hydraulic circuit for the first piston machine is realized, can be stored in the energy and removed from the energy.

In an advantageous embodiment, the working pressure line is connected via a tank line to a tank and formed in the tank line, a pressure relief valve. A connected to the tank line area of the working pressure line can be relaxed through the tank line. The pressure relief valve sets a limit pressure that must be exceeded in the first area of the working pressure line to allow the first area of the working pressure line to relax into the tank. As a result, for the connected to the tank line area of the working pressure line is a maximum pressure established. An overload of the working hydraulics by the drive system is thus prevented.

Particularly preferably, in the working pressure line between see the junction with the tank line and the working hydraulics, a shuttle valve connected, which connects the working hydraulics either with a further pressure medium source or with the branch. This makes it possible to supply the working hydraulics pressure medium and energy from the drive train, the pressure accumulator or alternatively from the further pressure medium source. This makes it possible to feed the working hydraulics with pressure medium and energy even if the drive train and the pressure accumulator do not provide enough energy or pressure medium.

In the storage line, a storage pressure retaining valve is preferably formed. The accumulator pressure holding valve prevents emptying of the accumulator via the accumulator pressure holding valve at an unfavorable time. This ensures that energy stored in the pressure accumulator does not escape beyond the accumulator pressure retention valve.

The accumulator pressure retaining valve is particularly preferably designed in its basic position as a check valve opening in the direction of the pressure accumulator. In the basic position of the accumulator pressure holding valve, it is possible to promote pressure medium and energy via the accumulator pressure holding valve into the pressure accumulator, which, however, can not escape in the opposite direction.

The illustrated embodiments of the drive system according to the invention are particularly suitable for the operation of refuse vehicles and of presses in refuse vehicles or other vehicles with a working hydraulics and intensive driving cycles. Preferred embodiments of the drive system according to the invention are shown in the drawing and will be explained in detail with reference to the following description. Show it:

Fig. 1 is a circuit diagram of a first embodiment of the drive system according to the invention and

2 shows a circuit diagram of a second exemplary embodiment of the drive system according to the invention with an open and a closed circuit.

1 shows an inventive drive system 1 with a mechanical drive train 2, a working hydraulics 3 and a device for hydrostatic braking 4. The mechanical drive train 2 comprises a diesel engine 5, a main gear 6, a first drive shaft 7 and a rear axle 8. Der Diesel engine 5 can be replaced by any prime mover. The main transmission 6 may comprise mechanical and / or hydraulic components. The Hinterachsgetriebe 8 can be replaced by another torque and energy consumers. A second drive shaft 9 is connected to a gear stage 10. The gear stage 10 is connected via a coupling 11 with the first drive shaft 7. Overall, the first drive shaft 7 is detachably connected to the second drive shaft 9 via the clutch 11. The second drive shaft 9 is connected to a first hydraulic pump 12 and a second hydraulic pump 13. The first hydraulic pump 12 can be swung out over a zero position in opposite directions. The first hydraulic pump 12 is connected to a storage line 14. The storage line 14 connects the hydraulic pump 12 to a pressure accumulator 15. The first hydraulic pump 12 is also connected via a suction line 14 'with a tank volume 21. In the storage line 14, a storage pressure retaining valve 24 is formed between the first hydraulic pump 12 and the first pressure accumulator 15. The memory pressure holding Valve 24 can take various positions, is adjustable and has a spring 241 on. By an actuator 240, the various positions of the accumulator pressure holding valve 24 can be controlled against the force of the spring 241. The storage line 14 is connected to the working hydraulics 3 via a storage pressure line 16.

In the accumulator pressure line 16, a pressure limiting valve 17 is arranged. The pressure relief valve 17 is designed as a pressure control valve with proportional control, but can be replaced by another pressure relief valve. By the pressure control valve 17, a minimum back pressure for the brake function is ensured for the second hydraulic pump 13. The pressure regulating valve 17 opens when the pressure in the first pressure accumulator 15 exceeds a first pressure limit. In the open state, pressure medium can flow via the pressure limiting valve 17 in the direction of the working hydraulics 3. The first pressure limit is set using a first spring 171. The pressure relief valve 17 is also made adjustable by generating an adjustable counterforce by means of an actuator 171. As a result, the first pressure limit is adjustable. The pressure-limiting valve 17 can be replaced by a non-adjustable pressure relief valve in a simpler embodiment. In addition, a shuttle valve 18 is connected to the accumulator pressure line 16 between the pressure relief valve 17 and the working hydraulics 3. The shuttle valve 18 includes a first input 181, a second input 182 and an output 183. The shuttle valve 18 only connects the higher pressure input 181 and 182 to the output 183. The first input 181 is connected to a branch 220. The second input 182 is connected to the further pressure medium source 23. The outlet 183 is connected to the outlet-side working hydraulics 3 via a section of the accumulator pressure line 16. The storage pressure line 16 is connected via a working line 22 with the second hydraulic pump 13 connected. The second hydraulic pump 13 is connected via a connecting line to the suction line 14 'and thus to the tank volume 21. The working line 22 and the accumulator pressure line 16 are connected to one another and to a tank line 19. In the illustrated embodiment, the accumulator pressure line 16, the working line 22 and the tank line 19 are connected to each other via the branch 220. The tank line 19 connects the working line 22 with the tank 21. In the tank line 19, a further pressure relief valve 20 is formed. The further pressure relief valve 20 opens only when the pressure in the working line 22 exceeds a second pressure limit, which is higher than the first pressure limit. The second pressure limit value is determined by the further pressure limiting valve 20 using the second spring 201. The further pressure relief valve 20 is not adjustable, but can also be replaced by an adjustable Höchstdruckbegrenzungs- valve.

The first hydraulic pump 12 is connected to a first adjusting device 120 for adjusting the stroke volume and the conveying direction of the first hydraulic pump 12. The pressure relief valve 17 includes an actuator, for. B. a proportional solenoid 170 and the accumulator pressure holding valve 24 also includes an actuator, for. B. a further proportional solenoid 240. The pressure accumulator 15 is connected to a pressure sensor 25, which measures the pressure which prevails in the pressure accumulator 15. The first adjusting device 120, the proportional magnet 170 and the pressure sensor 25 are connected to a not shown system for energy management. The system for energy management measures the pressure prevailing in the pressure accumulator 15 via the pressure sensor 25 and actuates the first hydraulic pump 12 via the first adjusting device 120, the pressure limiting valve 17 via the proportional magnet 170 and the accumulator pressure holding valve 24 via the further proportional magnet 240. If the pressure in the pressure accumulator 15 is less than the first pressure limit value, the pressure limiting valve 17 is closed. If, however, the pressure in the pressure accumulator 15 is higher than the first pressure limit value, then the pressure-limiting valve 17 is opened. The first pressure limit of the pressure relief valve 17 is adjustable.

If the pressure in the working line 22 is higher than the second pressure limit value, then the further pressure-limiting valve 20 is open. Then the working line 22 is relaxed in the tank 21. If the pressure in the working line 22, however, is lower than the further pressure limit value, then the further pressure limiting valve 20 is closed.

If the pressure at the second input 182 of the shuttle valve 18 is higher than the pressure at the first input 181, then the shuttle valve 18 connects the further pressure medium source 23 with the working hydraulics 3. However, is the pressure at the second input 182 of the shuttle valve 18 less than the pressure at the first Input 181, the shuttle valve 18 connects the accumulator pressure line 16 and the working line 22 to the working hydraulics. 3

When the clutch 11 is open, the drive train 2 and the second drive shaft 9 are decoupled. In the decoupled state, drive train 2 and second drive shaft 9 exchange no energy. Thus, the powertrain 2 and the entire hydraulics do not exchange energy. The powertrain 2 and the hydraulics are operated independently. The drive train 2 can also be switched off. In this case, the first hydraulic pump 12 z. B. operated from the accumulator 15 as a motor, which drives the second, the hydraulic working with hydraulic pressure pump 13, drives.

In the closed clutch 11, however, the drive train 2 is coupled to the second drive shaft 9. Thus, power and torque from the powertrain 2 on the second drive shaft 9 or vice versa transmitted from the second drive shaft 9 to the drive train 2. The powertrain 2 and the hydraulics can thereby exchange energy.

The drive system 1 can be operated with an open or alternatively with a closed clutch 11 in order to set the desired energy flow.

The hydraulic decoupled from the mechanical drive train 2 can be operated in various decoupled hydraulic operating modes, which will be described below.

In a first decoupled hydraulic operating mode, stored energy and stored pressure medium are fed directly to the working hydraulics 3 in the pressure accumulator 15. The accumulator pressure holding valve 24 is positioned in its basic position. In its basic position, the accumulator pressure holding valve 24 is designed as a check valve which opens in the direction of the pressure accumulator 15. Pressure medium or stored energy stored in the pressure accumulator 15 thus does not escape via the first hydraulic pump 12. Rather, the pressure-limiting valve 17 is depressed on the input side with the pressure from the pressure accumulator 15. In the first decoupled hydraulic operating mode, the pressure in the pressure accumulator 15 is higher than the set first pressure limit value. The pressure relief valve 17 is opened thereby. Thus, the same pressure prevails in the working line 22 as in the pressure accumulator 15. In the first decoupled hydraulic operating mode, the pressure limiting valve 20 is closed. The first pressure limit is less than the second pressure limit. The pressure in the working line 22 is thus between the first and the second pressure limit. In the first decoupled hydraulic operating mode, the shuttle valve 18 connects the accumulator pressure line 16 and the working line 22 with the working hydraulics 3. Thus, the pressure accumulator 15 via the Shuttle valve 18 connected to the working hydraulics 3. The working hydraulics 3 can use the energy from the pressure accumulator 15.

In a second decoupled hydraulic operating mode of the working hydraulics 3 is supplied from the first pressure accumulator 15 indirectly stored energy. In this second decoupled hydraulic operating mode, the pressure in the pressure accumulator 15 is below the first pressure limit value. The pressure limiting valve 17 is closed. The accumulator pressure holding valve 24 is positioned by urging the proportional solenoid 240 in its other position. In this further position, the accumulator pressure holding valve 24 is unlocked. As a result, the first pressure accumulator 15 can be expanded via the first hydraulic pump 12 to generate a torque in the tank 21. In the second decoupled hydraulic operating mode, the pressure accumulator 15 is expanded via the storage line 14 and via the first hydraulic pump 12 into the tank 21. The energy stored in the first pressure accumulator 15 is delivered to the first hydraulic pump 12 and supplied from the latter via the second drive shaft 9 of the second hydraulic pump 13. The second hydraulic pump 13 delivers with this energy pressure medium from the tank 21 via the working line 22 in the direction of working hydraulics 3. The storage pressure line 16 and the working line 22 are analogous to the first decoupled hydraulic operating mode and under the same conditions via the shuttle valve 18 with the working hydraulics. 3 connected.

When the clutch 11 is closed, the hydraulics are coupled to the mechanical drive train 2. The drive train 2 and the hydraulic exchange via the clutch 11 energy and torque.

In a first coupled hydraulic mode of operation, the powertrain 2 transfers only energy from the diesel engine 5 into the hydraulics. Energy from the diesel engine 5 is via the transmission unit 6, the first Drive shaft 7, the clutch 11 and the gear stage 10 and the second drive shaft 9 are transmitted to the hydraulic system.

In a second coupled hydraulic mode of operation, the powertrain 2 transfers only energy from the rear axle 8 into the hydraulics. This operating mode is present when braking the drive system. In this case, kinetic energy is transferred from the rear axle 8 due to the inertia of a driven vehicle via the first drive shaft 7, the clutch 11, the gear stage 10, the second drive shaft 9 in the hydraulic system.

The hydraulics each receive energy in the first and second coupled hydraulic modes of operation. The second hydraulic pump 13 thereby promotes pressure medium from the tank 21 via the working line 22 in the direction of working hydraulics 3. This allows the second hydraulic pump 13 to promote pressure medium and energy in the working hydraulics 3. The first hydraulic pump 12 can be swung out in one of the two opposite directions. Thus, the first hydraulic pump 12 can promote pressure medium with energy from the drive train 2 in the direction of the pressure accumulator 15 or with energy from the pressure accumulator 15 in the direction of the tank 21 and thereby support the drive train 2.

The first hydraulic pump 12 swung out in a first direction relaxes pressure medium from the pressure accumulator 15 into the tank 21, as in the decoupled operation. The first hydraulic pump 12 drives the second hydraulic pump 13 via the second drive shaft 9. The first hydraulic pump 12 thus supports the drive of the second hydraulic pump 13 with energy from the pressure accumulator 15. The second hydraulic pump 13 is simultaneously supplied with energy from the drive train 2 and the pressure accumulator 15.

The swung in a second opposite direction first hydraulic pump 12 promotes pressure medium from the Tank 21 in the pressure accumulator 15 and / or in the storage pressure line 16. The delivery volume of the first hydraulic pump 12 is adapted to the pressure between the first hydraulic pump 12 and the accumulator pressure holding valve 24 and the rotational speed of the second drive shaft 9. If the pressure in the pressure accumulator 15 is higher than the first pressure limit value, the pressure limiting valve 17 is open. If the pressure in the first pressure accumulator 15 is additionally greater than the pressure in the working line 22, then pressure medium flows via the pressure limiting valve 17 in the direction of working hydraulics 3. In this way, energy is conveyed from the drive train 2 via the second hydraulic pump 12 and the pressure limiting valve 17 into the working hydraulics , This mode of operation is also possible without the second hydraulic pump 15.

In a third coupled hydraulic operating mode, the drive train 2 transmits energy from the hydraulics in the rear axle 8. Here, energy and torque from the second drive shaft 9 via the transmission stage 10, the clutch 11 and the first drive shaft 7 are transmitted to the rear axle 8 , The swung in the first direction first hydraulic pump 12 relaxes pressure fluid from the pressure accumulator 15 in the tank 21. The first hydraulic pump 12 thus drives via the second drive shaft 9, the rear axle 8 with energy from the pressure accumulator 15. The second drive shaft 9 can simultaneously promote pressure medium from the tank 21 in the working hydraulics 3. This makes it possible to simultaneously feed both the rear axle 8 and the working hydraulics 3 with energy from the pressure accumulator 15.

If pressure medium is conveyed in the direction of the already full pressure accumulator 15, the pressure-limiting valve 17 and the further pressure-limiting valve 20 open in each case. As a result, the excess pressure medium is returned to the tank 21 and hydraulic braking takes place with generation of heat. By using two hydraulic pumps 12, 13, the drive system 1 according to the invention can oppress the working hydraulics 3 with pressures from a wide pressure range. A combination of the drive system 1 according to the invention with a power take-off as a further pressure medium source 23 is uncomplicated executable.

FIG. 2 shows a further drive system 100 according to the invention. The further drive system 100 from FIG. 2 emerges from the drive system 1 from FIG. To avoid unnecessary repetition, only the changes are explained in detail below. Identical elements are given the same reference numerals. The second hydraulic pump 13 is replaced by the adjustable second hydraulic pump 13 '. The delivery volume ratio between the two hydraulic pumps 12, 13 'can thus be adjusted variably via both pumps. In the further drive system 100, the connection between the first hydraulic pump 12 and the tank 21 of FIG. 1 is replaced by a further storage line 140, which connects the first hydraulic pump 12 with a further pressure accumulator 150 instead of the tank 21. For the first hydraulic pump 12, the additional pressure accumulator 150 thus replaces the tank 21. The first hydraulic pump 12 is thus arranged in a closed circuit. The pressure accumulator 15 is designed as a high-pressure accumulator and the further pressure accumulator 150 as a low-pressure accumulator. The accumulator pressure line 16 and the pressure limiting valve 17 from FIG. 1 are not present in the further drive system 100. Instead, the working line 22 is connected directly to the working hydraulics 3 via the shuttle valve 18. The shuttle valve 18 is formed in the working line 22 between the spare branch 220 'and the working hydraulics 3. The replacement branch 220 'replaces the branch 220 of FIG. 1. The working line 22 is connected to the first input 181. All functions described for the drive system 1, which do not require an open pressure relief valve 17, are also with the other drive system 100 in the for the drive system 1 described manner feasible. The second hydraulic pump 13 is connected via a further suction line 22 'directly to the tank 21 and is thus operated in the open circuit. Because of the arrangement of the first pump 12 in a closed circuit higher speeds are possible, resulting in an improvement in efficiency.

The energy management system likewise not shown in FIG. 2 is connected to a second adjusting device 130, which is connected to the further second hydraulic pump 13 'and adjusts its displacement and conveying direction. The system for energy management additionally controls the further second hydraulic pump 13 'via the second adjusting device 130. Thus, optimal operation management is also possible for the further drive system 100.

The hydraulic pumps can be replaced by constant displacement pumps. However, in this case eliminates some of the described advantageous functions.

By forming a closed circuit for the first hydraulic pump 12, higher pump speeds are possible. A biasing pressure of the second pressure accumulator 150, which is higher than the tank pressure, allows the suction of pressure medium from the second pressure accumulator 150, a higher flow rate than the suction of pressure medium from the tank 21st

The drive systems according to the invention are particularly suitable for refuse vehicles, buses and for vehicles with lifting devices, such. Forklift or wheel loader.

The invention is not limited to the illustrated embodiments. Rather, individual features of the embodiments are advantageously combined. In particular, in the embodiment of FIG. 1, the second hydraulic pump 13 can be omitted.

Claims

claims

Drive system, a working hydraulic system (3) and a device for hydrostatic braking (4) with a first hydrostatic piston machine (12) connected to a drive train (2) of the traction drive, wherein the first hydrostatic piston machine (12) has a Storage line (14) with a pressure accumulator (15) is connected, characterized in that the storage line (14) via a storage pressure line (16) to the working hydraulics (3) is connected.

2. Drive system according to claim 1, characterized in that the first hydrostatic piston engine (12) is an adjustable hydraulic pump.

3. Drive system according to claim 2, characterized in that the first hydrostatic piston machine (12) is a over a zero position in opposite directions swing-out hydraulic pump.

4. Drive system according to one of claims 1 to 3, characterized in that a second with the first hydrostatic piston engine (12) coupled hydrostatic piston engine (13) via a working pressure line (22) to the working hydraulics (3) is connected.

5. Drive system according to one of claims 1 to 4, characterized in that in the storage line (14), a storage pressure retaining valve (24) is formed.

6. Drive system according to claim 5, characterized in that the accumulator pressure retaining valve (24) is designed in its basic position as in the direction of the pressure accumulator (15) opening toward the check valve.

7. Drive system according to one of claims 1 to 6, characterized in that in the accumulator pressure line (16) a pressure relief valve (17) is formed.

8. Drive system according to claim 7, characterized in that the pressure limiting valve (17) is designed as a controllable pressure relief valve (17).

9. Drive system according to claim 7 or 8, characterized in that the storage pressure line (16) between the pressure relief valve (17) and the working hydraulics (3) via a tank line (19) with a tank (21) is connected and in the tank line (19 ) is formed a further pressure relief valve (20).

10. Drive system according to claim 9, characterized in that the working hydraulics (3) via a shuttle valve (18) with the accumulator pressure line (16) or with a further pressure medium source (23) is connectable, wherein the shuttle valve (18) with the accumulator pressure line (16 ) is connected between a branch (220) of the tank line (19) and the working hydraulics (3).

11. Drive system according to one of claims 1 to 10, characterized in that the connection of the first piston machine (12) to the drive train (2) by means of a clutch (11) is separable.

12. Drive system with a travel drive, a

Working hydraulics (3) and a device for hydrostatic braking (4) with one via a clutch

(11) first hydrostatic piston machine (12) connected to a drive train (2) of the traction drive and a second hydrostatic piston machine (13) mechanically connected to the first hydrostatic piston machine (12), the first hydrostatic piston machine (12) being connected via a storage line (14 ) is connected to a pressure accumulator (15) and the second hydrostatic piston machine (13) via a working line (22) is connected to the working hydraulics, characterized in that the first hydrostatic piston machine (12) with a further pressure accumulator (150) is connected and the first hydrostatic piston machine (12) is arranged in a closed circuit and the second hydrostatic piston machine (13) is arranged in an open circuit.

13. Drive system according to claim 11, characterized in that the first hydrostatic piston machine (12) and / or the second hydrostatic piston machine (13) is an adjustable hydraulic pump.

14. Drive system according to claim 12, characterized in that the first hydrostatic piston engine (12) and / or the second hydrostatic piston engine (13) is a swinging over a zero position in opposite directions hydraulic pump.

15. Drive system according to one of claims 11 to 13, characterized in that the pressure accumulator (15) as a high-pressure accumulator and the further accumulator (150) are designed as low-pressure accumulator.

16. Drive system according to one of claims 11 to 14, characterized in that the working line (22) via a tank line (19) with a tank (21) is connected and in the tank line (19) a pressure relief valve (20) is formed.

17. Drive system according to one of claims 11 to 13, characterized in that the working hydraulics (3) via a shuttle valve (18) with the working line (22) or with a further pressure medium source (23) is connectable, wherein the shuttle valve (18) with the Working line (22) between the Ersatzabzweigung (220 ') and the working hydraulics (3) is connected.

18. Drive system according to one of claims 11 to 16, characterized in that in the storage line (14) a storage pressure retaining valve (24) is formed.

19. Drive system according to claim 17, characterized in that the accumulator pressure retaining valve (24) is designed in its basic position as opening to the pressure accumulator 15 back check valve.