CN105667291B

CN105667291B - Hydrostatic drive system

Info

Publication number: CN105667291B
Application number: CN201510883657.1A
Authority: CN
Inventors: L·克里特蒂安; A·朗根
Original assignee: Linde Hydraulics GmbH and Co KG
Current assignee: Linde Hydraulics GmbH and Co KG
Priority date: 2014-12-08
Filing date: 2015-12-04
Publication date: 2021-02-23
Anticipated expiration: 2035-12-04
Also published as: CN105667291A; DE102014118139A1

Abstract

The invention relates to a hydrostatic drive system (1) having a hydrostatic drive device (7; 7a, 7b) which is drivingly connected to an internal combustion engine (2), wherein the hydrostatic drive device (7; 7a, 7b) is operated as a hydraulic motor which is driven by pressure medium from a pressure medium reservoir (10), wherein the drive device (7; 7a, 7b) which is operated as a hydraulic motor forms a hydraulic starter for assisting the power-assisted drive of the operating internal combustion engine (2) and the start-stop function of the stopped internal combustion engine (2). According to the invention, the pressure medium storage device (10) comprises a first pressure medium storage unit (10a) and a second pressure medium storage unit (10b), and a loading valve device (30) is provided, which can load the first pressure medium storage unit (10a) independently of the loading operation of the second pressure medium storage unit (10 b).

Description

Hydrostatic drive system

Technical Field

The invention relates to a hydrostatic drive system having a hydrostatic drive unit which is drivingly connected to an internal combustion engine, wherein the hydrostatic drive unit is operated as a hydraulic motor which can be driven by a pressure medium from a pressure medium storage device, wherein the drive unit which is operated as a hydraulic motor is configured such that: a power assist drive for assisting the operated internal combustion engine; a hydraulic starter for a start-stop function of a stopped internal combustion engine.

Such drive systems are used in vehicles, in particular mobile work machines.

Background

In order to reduce the fuel consumption of an internal combustion engine, it is known to implement the drive system as a hydraulic drive system, in which, in addition to the internal combustion engine as an energy source, a pressure medium storage device is used as a further energy source, and the operating mechanism device, which is in driving connection with the internal combustion engine, is operated as a hydraulic motor, which is driven by the pressure medium from the pressure medium storage device.

A hydraulic starter for a start-stop function of an internal combustion engine can be formed by means of a running gear device by the motor running of the running gear device driven by pressure medium from a pressure medium storage device. This start-stop function enables: the internal combustion engine is stopped during a work break or work interruption and is automatically started again by the work function or the travel drive when torque is required in order to achieve fuel savings.

By operating the motor of the running gear arrangement, which is driven by the pressure medium from the pressure medium reservoir, a power-assisted drive of the already operating internal combustion engine can be further realized by means of the running gear arrangement for an additional torque with which the already operating internal combustion engine can be assisted during driving operation, or during acceleration, of a vehicle that is traveling stationary at the target speed, or during operation of the hydraulic device. The hydrostatic power-assisted drive, which is formed by the motor operation of the operating mechanism driven by the pressure medium from the pressure medium reservoir, makes it possible to save fuel and to compact the internal combustion engine.

The capacity of the pressure medium storage device can be adapted to the respective use. For the use of the hydraulic drive, which is formed by the operating mechanism device and the pressure medium reservoir device, as a hydraulic starter for an internal combustion engine, a smaller capacity of the pressure medium reservoir device is sufficient: in order to accelerate the internal combustion engine to the starting speed, a few revolutions of the crankshaft of the internal combustion engine are sufficient. For the use of a hybrid drive, which is composed of a travel mechanism device and a pressure medium reservoir device, as a power-assisted drive for an internal combustion engine, a large capacity of the pressure medium reservoir device is required in order to be able to provide a permanently continuous power-assisted drive for the operating internal combustion engine (for example, when the vehicle is in motion or when the working hydraulic device is operated) in order to be able to save fuel to a large extent by means of the power-assisted drive.

A hybrid drive system of this type is known from DE 102012111296 a1, in which a hydrostatic drive unit, which is operated as a hydraulic motor, is driven by pressure medium from a pressure medium reservoir, and in which the drive unit, during motor operation, forms: a hydraulic starter for an internal combustion engine within the scope of a start-stop function, and a power-assisted drive for assisting an already running internal combustion engine. In DE 102012111296 a1, the pressure medium reservoir is formed by a single pressure medium reservoir.

If the hybrid drive, which is formed in the drive system by the hydrostatic drive and the pressure medium reservoir, is to function as a hydraulic starter and as a power assist drive for the internal combustion engine, the capacity of the pressure medium reservoir should be adapted to the functional requirements with high requirements, that is to say to the requirements as a power assist drive for assisting the already operating internal combustion engine.

In such a drive system, it is desirable for the pressure medium reservoir to be charged with recovered energy, for example, in a braking state of the vehicle, as a result of which energy recovery and further fuel saving are achieved by means of the pressure medium reservoir. If the drive system is used in a vehicle (e.g. a work machine) having a travel drive and a working hydraulic unit and the vehicle is used partially stationary, for example if only the working hydraulic unit is operated in a vertical work machine, this cannot be achieved: in the braking state of the vehicle, the pressure medium reservoir is charged with recovered braking energy for the start-stop operation of the internal combustion engine. As soon as the converted recoverable energy is not sufficient for loading the pressure medium storage device, the pressure medium storage device needs to be loaded by the pump operation of the operating mechanism device in such a way that the operating mechanism device is driven by the internal combustion engine. For loading the pressure medium reservoir, the operating device is initially driven by the power supplied by the internal combustion engine, so that the loading operation of the pressure medium reservoir is initially carried out using the energy of the internal combustion engine. Since the pressure medium reservoir is designed to function as a booster drive, the following energies are correspondingly large: the energy must be applied by the internal combustion engine in order to charge a pressure medium reservoir, which is designed as a booster drive in terms of capacity, in order to build up sufficient pressure in the pressure medium reservoir, which enables the operating mechanism device to operate as a hydraulic starter for the start-stop function. The initial charging of the pressure medium reservoir, which is designed as a booster drive, with the energy to be initially applied by the internal combustion engine results in a reduction of the fuel saving potential of the start-stop function, since the pressure medium reservoir, which is designed as a booster drive, for starting the internal combustion engine must initially be charged with energy and therefore must also be charged with an excess capacity of the pressure medium reservoir, which is not required for starting the internal combustion engine, with the energy of the internal combustion engine.

Disclosure of Invention

The object of the present invention is to provide a drive system of the type mentioned at the outset, which is improved with regard to energy saving in relation to the start-stop function.

According to the invention, the object is achieved in that the pressure medium storage device has a first pressure medium storage unit and a second pressure medium storage unit, wherein a loading valve device is provided which enables a loading operation of the first pressure medium storage unit independently of a loading operation of the second pressure medium storage unit. In the drive system according to the invention, the capacity of the pressure medium storage means is thus divided into a first pressure medium storage unit and a second pressure medium storage unit. The loading valve device is capable of loading the pressure medium only to the first pressure medium storage unit. If the hybrid drive, which is formed by the pressure medium reservoir and the operating mechanism, is used not only as a booster drive but also as a hydraulic starter for a stopped internal combustion engine, it is advantageous in the drive system according to the invention, since the hydraulic motor can be operated functionally as a hydraulic starter with pressure medium only by the first pressure medium reservoir unit. Since the charging valve device enables a charging process of the first pressure medium storage unit alone, a high degree of energy saving of the start-stop function is achieved, since for the charging process of the first pressure medium storage unit only the first pressure medium storage unit has to be charged with pressure medium before the internal combustion engine is stopped, for which purpose only a small amount of energy is required, which can be recovered or initially applied by the internal combustion engine. It is therefore particularly advantageous with the aid of the invention if there is a small conversion of the recoverable energy in the operation of the drive system, since a start-stop function of the internal combustion engine can be achieved without the pressure medium storage device initially having to be loaded with energy from the internal combustion engine to an intensified extent to the full capacity provided for the power-assisted drive.

According to an advantageous embodiment of the invention, the first pressure medium storage unit has a pressure medium reservoir, the capacity of which is designed as a hydraulic starter for starting the stopped internal combustion engine as a function of the requirements of the operating device. For the start-stop operation, therefore, only the first pressure medium storage unit needs to be charged with pressure medium, so that before the internal combustion engine is stopped, only a small amount of energy is required for the charging operation of the first pressure medium storage unit and therefore the first pressure medium storage unit can already be charged with the required charging state for the starting process of the internal combustion engine with a low amount of recoverable energy, or only a small amount of energy of the internal combustion engine initially needs to be used, in order to charge the first pressure medium storage unit with the required charging state for the starting process of the internal combustion engine.

According to an advantageous embodiment of the invention, the second pressure medium storage unit has at least one pressure medium reservoir, wherein the total capacity of the first pressure medium storage unit and the second pressure medium storage unit is designed as a function of the requirement of the actuator device as a power-assisted drive. By means of the additional pressure medium reservoir or reservoirs of the second pressure medium storage unit, the total capacity of the pressure medium storage device, which is designed for the power-assisted drive, can be used in a simple manner.

It is particularly advantageous according to one embodiment of the invention for the operating device, which is operated as a hydraulic starter of a stopped internal combustion engine, to be driven with pressure medium from the first pressure medium storage unit. If the operating device, which operates as a hydraulic starter, is driven exclusively with pressure medium from the first pressure medium storage unit, it is sufficient to ensure sufficient loading of the first pressure medium storage unit with respect to the start-stop function before the internal combustion engine is stopped, for which only a small amount of energy is required.

It is also particularly advantageous according to one embodiment of the invention if the operating device, which is to be operated as a hydraulic starter of a stopped internal combustion engine, is first driven with pressure medium from the first pressure medium storage unit, as long as the pressure of the first pressure medium storage unit corresponds to the pressure of the second pressure medium storage unit, and then the operating device, which is to be operated as a hydraulic starter of a stopped internal combustion engine, is driven with pressure medium from the first pressure medium storage unit and the second pressure medium storage unit. Thereby it is achieved that: for a starting process of the internal combustion engine which has been stopped, the operating mechanism device which is operated during operation of the motor is first driven only with pressure medium from the first pressure medium storage unit, as long as the pressure in the first pressure medium storage unit is higher than the pressure in the second pressure medium storage unit. If the pressure of the first pressure medium storage unit drops to the level of the second pressure medium storage unit as a result of the removal of pressure medium from the first pressure medium storage unit, the operating mechanism device, which operates in the motor mode from this point in time, is driven with pressure medium from the first pressure medium storage unit and the second pressure medium storage unit. In this way, the starting process of the internal combustion engine can be carried out over a relatively long period of time without the storage volume of the first pressure medium storage unit having to be increased, if necessary, by the motor operation of the operating mechanism device.

It is particularly advantageous according to one embodiment of the invention for the operating device, which is operated as a power-assisted drive of the already operating internal combustion engine, to be driven with pressure medium from the first pressure medium storage unit and the second pressure medium storage unit. In this way, the booster drive of the already operating internal combustion engine can be carried out in a simple manner over a relatively long period with pressure medium from the two pressure medium storage devices.

According to an advantageous embodiment of the invention, the charging valve device is connected on the input side to the charging line and on the output side to the first charging branch line of the first pressure medium storage unit and to the second charging branch line of the second pressure medium storage unit. Thus, it is possible to realize in a simple manner: the loading valve device can be used to perform a separate loading operation of the first pressure medium storage unit and a loading operation of the second pressure medium storage unit.

It is particularly advantageous according to one embodiment of the invention if the charging valve device has a first control position in which the charging line is connected to the first charging branch line and the connection of the charging line to the second charging branch line is blocked. In the first control position, therefore, the first pressure medium storage unit for the start-stop function can be operated by loading itself in a simple manner by means of the loading valve device.

According to an advantageous embodiment of the invention, the charging valve device has a second control position in which the charging line is connected to the second charging branch line and the connection of the charging line to the first charging branch line is blocked. Such a loading valve device enables pressure medium storage units to be loaded one after the other in a simple manner. After the first pressure medium storage unit has been loaded to a loading state which is sufficient for the starting process of the internal combustion engine, the second pressure medium storage unit can then be loaded for power-assisted driving in a simple manner by operating the loading valve into the second control position.

The loading valve device preferably operates as follows: first, the first pressure medium storage unit is loaded with pressure medium and, in the event of a predefined loading state of the first pressure medium storage unit, the second pressure medium storage unit is loaded with pressure medium. It is thus possible to realize: only a small amount of energy is required for loading the first pressure medium storage unit into the predefined loading state required for the starting process of the internal combustion engine, so that a small amount of recoverable energy or a small amount of initial energy to be applied by the internal combustion engine is already sufficient for loading the first pressure medium storage unit sufficiently for the start-stop function.

According to an advantageous, alternative embodiment of the invention, the charging valve device has a second control position in which the charging line is connected to the first charging branch line and to the second charging branch line. In the second control position, the two pressure medium storage devices can therefore be loaded with pressure medium at the same time. A high energy recovery can thereby be achieved if the pressure medium storage unit is loaded with recoverable energy and there is sufficient recoverable energy.

According to an advantageous embodiment of the invention, the charging valve device is operated in such a way that it is operated in the first control position or in the second control position as a function of the recoverable energy of the drive system. The loading valve device, which in the first control position connects only the first pressure medium storage unit to the loading line and in the second control position connects only the second pressure medium storage device to the loading line, can be controlled in a simple manner as a function of the recoverable energy of the drive system in such a way that, when the recoverable energy of the drive system is low, the loading valve device is operated into a first control position in order to ensure loading of the first pressure medium storage unit for the starting process of the internal combustion engine, and, when the recoverable energy of the drive system is high, the loading valve device is operated into a second control position in which both pressure medium storage units can be loaded.

According to a suitable embodiment of the invention, the charge valve device is designed as a switching valve. The construction outlay for the loading valve device is therefore low.

According to an advantageous embodiment of the invention, the charge valve device can be operated as a function of the charge pressure of the first pressure medium storage unit. The loading valve arrangement, which in the first control position connects only the first pressure medium storage unit to the loading line and in the second control position connects only the second pressure medium storage unit to the loading line, can be controlled in a simple manner as follows depending on the loading pressure of the first pressure medium storage unit: first, the first pressure medium storage unit is loaded with pressure medium and, in the event that the first pressure medium storage unit achieves a predefined loading state (which is defined by the loading pressure of the first pressure medium storage unit), the second pressure medium storage unit is loaded with pressure medium.

An advantage that can be achieved with regard to a simple construction with little structural outlay is that, according to one embodiment of the invention, the charging valve device can be hydraulically operated. The charging valve device, which is controlled as a function of the charging pressure of the first pressure medium storage unit, can thus be hydraulically controlled in a simple manner directly by the charging pressure.

According to an alternative embodiment of the invention, the charging valve device can be operated electrically and is operatively connected to an electronic control device for operation. The loading valve device can thus also be operated in a simple manner depending on the loading pressure of the first pressure medium storage unit or depending on the recoverable energy of the drive system.

For this purpose, the electronic control device is operatively connected on the input side to the pressure sensor of the first pressure medium storage unit and to the pressure sensor of the second pressure medium storage unit. The loading pressure and thus the loading state of the pressure medium reservoir can be determined in a simple manner by the electronic control device using a corresponding pressure sensor.

It is particularly advantageous if, according to one embodiment of the invention, the electronic control device determines the recoverable energy of the drive system and, when a determination is made that there is sufficient recoverable energy for the charging of the first pressure medium storage unit and the second pressure medium storage unit, the electronic control device actuates the charging valve device into the second control position. The use of an electronic control device makes it possible in a simple manner to determine the recoverable energy of the drive system as a function of its current operating state in order to control the loading valve device accordingly.

According to a preferred embodiment of the invention, the charging valve device is operated by spring means from a first control position and hydraulically or electrically into a second control position. In this way, it is achieved in a simple manner that the loading valve arrangement is in the inoperative state in the first control position, in which a loading operation of the first pressure medium storage unit for the start-up process is effected by the start-stop function.

According to a further advantageous development of the invention, a delay valve (Retarderventil) is arranged in the charging line. If the charging operation of the pressure medium reservoir is implemented in a recoverable manner in the braking operation of the vehicle, this can be implemented in a simple manner by means of a delay valve provided in the charging line: if the loading pressure of the pressure medium reservoir is low and is not sufficient to build up the required braking torque, the pressure can be adjusted accordingly by means of the delay valve in order to generate the desired braking power.

In the charging line, a shut-off valve, in particular a check valve, which opens in the direction of the charging valve device, is arranged in a suitable manner. With such a shut-off valve, the pressure medium reservoir can be charged with pressure medium in a simple manner with the shut-off valve open, and, after the charging process, the pressure medium reservoir charged with pressure medium is shut off in the direction of the charging line with the shut-off valve in the shut-off position, in order to prevent an undesired discharge of the pressure medium reservoir.

According to a further advantageous development of the invention, the first pressure medium storage unit is connected to a first unloading line and the second pressure medium storage unit is connected to a second unloading line, wherein the unloading lines are connected to each other and to the operating device, wherein a shut-off valve, in particular a check valve, is arranged in the second unloading line, which shut-off valve is closed in the direction of the second pressure medium storage unit. If the first loading branch line is connected to the first unloading line, it can be ensured in a simple manner by means of a shut-off valve provided in the second unloading line: in the first control position of the charging valve device, only the first pressure medium storage unit is charged.

The invention further relates to a vehicle having a hydrostatic drive system according to the invention, said vehicle having a travel drive and/or a working hydraulic device. In such vehicles, the charging operation of the pressure medium reservoir is effected by recovering energy in the braking state of the vehicle and/or in the energy recovery operation of the working hydraulics (for example in the lowering operation of the lifting drive of the working hydraulics).

In order to ensure an internal combustion engine start-stop function in such a vehicle, an electronic control device is provided that controls the charge valve device, wherein the electronic control device is configured to: before the internal combustion engine is stopped, the state of charge of the first pressure medium storage unit is checked during the interruption of operation.

Here, the electronic control device is configured to: in the event of a detection that the loading state of the first pressure medium storage unit is insufficient for the starting process of the internal combustion engine, the first pressure medium storage unit is caused to perform a loading operation. If the first pressure medium storage unit is loaded by the previous recuperation loading operation and is not sufficient to be able to carry out a starting process of the stopped internal combustion engine by means of the motor operation of the drive, the first pressure medium storage unit is initially loaded with energy from the internal combustion engine by the electronic control device in a simple manner in order to be able to carry out the start-stop function.

The electronic control device is suitably configured to: the recoverable energy is determined by an electronic control device depending on the current operating state of the vehicle and controls the loading valve device. By means of the electronic control device, it is possible in a simple manner to determine the recoverable energy of the vehicle, for example the kinetic energy of the vehicle and/or the potential energy of the working hydraulic means lifting drive, in dependence on the current operating state of the vehicle, in order to control the loading valve device appropriately.

Drawings

Further advantages and details of the invention are explained in more detail below with the aid of exemplary embodiments shown in the schematic drawings. The figures show:

FIG. 1 is a schematic diagram of a first embodiment of the hydrostatic drive system according to the invention,

FIG. 2 is a schematic diagram of a second embodiment of the hydrostatic drive system according to the invention, and

fig. 3 is a circuit diagram of a third embodiment of the hydrostatic drive system according to the invention.

Detailed Description

Fig. 1 to 3 each show a hydrostatic drive system 1 according to the invention of a vehicle, not shown in detail. The vehicle is configured, for example, as a mobile work machine, a ground transport vehicle or a construction machine or a farm machine. Like parts are designated by like reference numerals.

The drive system 1 according to the invention has: an internal combustion engine 2, such as a diesel engine; a vehicle travel drive device 3 driven by the internal combustion engine 2; and a vehicle working hydraulic device 4 driven by the internal combustion engine 2.

The travel drive 3 is in the illustrated exemplary embodiment designed as a hydrostatic travel drive, which has an operating pump 5, which is adjustable with respect to the delivery volume and which is drivingly connected for driving purposes to a driven shaft 6 of the internal combustion engine 2. The operating pump 5 is connected in a closed circuit with one or more hydraulic motors, not shown in detail, of fixed or adjustable displacement, which are operatively connected to the drive wheels of the vehicle in a manner not shown in detail.

The travel drive 3 may alternatively be designed as an electric travel drive, which has: a generator driven by the internal combustion engine 2; one or more electric running motors. Furthermore, a mechanical travel drive can be provided as a travel drive, which has a mechanical transmission, for example a stepped shifting transmission or a power split transmission or a torque converter transmission.

The working hydraulics 4 comprise the working functions of a working machine, for example for operating a load carrier on a lifting bar in an industrial truck, or of a working equipment consisting of a bucket in a construction machine, for example in the form of a shovel.

The drive system 1 has a hydrostatic drive unit 7, which is in driving connection with the internal combustion engine 2 and for this purpose is in driving connection with a driven shaft 6 of the internal combustion engine 2. The hydrostatic drive 7 can be operated as a hydraulic motor, which can be driven by means of pressure medium from the pressure medium reservoir 10. The operating mechanism device 7, which can be operated as a hydraulic motor, together with the pressure medium reservoir 10 forms a hybrid hydraulic system, which makes it possible to: a start-stop function of the internal combustion engine 2; the internal combustion engine 2 that is already running is power-assisted driven. The operating mechanism 7, which operates as a hydraulic motor, thus forms a power assist drive for assisting the already operating internal combustion engine 2 and a hydraulic starter for carrying out a start-stop function of the already stopped internal combustion engine 2.

In the exemplary embodiment shown, the operating mechanism arrangement 7 comprises a first hydrostatic operating mechanism 7a and a second hydrostatic operating mechanism 7b, each of which is in driving connection with the output shaft 6.

In the case of identical rotational directions and identical throughflow directions of the pressure medium, the operating means 7a and the operating means 7b can each be operated as a hydraulic pump.

The first operating device 7a, which operates as a hydraulic pump, is used to supply the working hydraulic unit 4 with pressure medium. In the exemplary embodiment shown, the operating element 7a is designed as an actuating drive with a variable displacement volume, for example as an axial piston machine in the form of a swash plate. The operating mechanism 7a may alternatively be configured as a constant pump with a constant displacement volume.

The operating means 7a operates in an open circuit and is connected on the input side with the suction side to the container 12 by means of the suction line 11. The supply line 13, which is connected on the output side to the supply side of the operating means 7a, is connected to a control valve device, not shown in detail, by means of which a hydraulic consumer, not shown in detail, of the working hydraulic device 4 can be controlled. The control valve means preferably comprise one or more directional valves for operating the consumers of said working hydraulics 4. In addition, in the exemplary embodiment shown, a priority valve 14 is shown, with which a priority supply of consumers 15 (for example hydraulic steering systems of a vehicle) supplied by the operating element 7a during pump operation can be ensured. The priority valve 14 is connected on the input side to the delivery side of the operating element 7a and on the output side to a delivery line 13 leading to the hydraulic working unit 4 and to a delivery line 16 leading to the steering unit. The priority valve 14 is controlled by a spring 17 and by the load pressure of the preferred consumer in a load pressure line 18.

The second operating device 7b, which operates as a hydraulic pump, is used to supply the supply pressure circuit 20 of the drive system 1 with pressure medium. The second operating member 7b is designed as a constant machine with a constant displacement volume, which operates in an open circuit. The second operating member 7b is connected on the suction side to the container 12 via a suction line 21 and feeds into a supply pressure line 22 connected to the delivery side, to which supply pressure line respective consumers of the supply pressure circuit 20 are connected, for example: a control device for controlling the displacement volume of the operating pump 5, a control device 23 of the first operating means 7a, a feed device of the hydrostatic traction drive 3, a brake device of the vehicle, and pilot control valves for control valves of the working fluid pressure device 4.

In the pump mode, the first operating element 7a, which is driven by the internal combustion engine 1, draws pressure medium out of the reservoir 12 via the suction line 11 and feeds it into the feed line 13 of the hydraulic working unit 4 or into the feed line 16 of the steering unit 15 via the priority valve 14. In the motor operation of the first operating means 7a, the first operating means 7a is driven on the suction side with pressure medium from the pressure medium reservoir 10. In motor operation, the first operating means 7a generates a torque on the output shaft 6.

In the pump mode, the second operating mechanism 7b, which is driven by the internal combustion engine 1, draws pressure medium out of the tank 12 via the suction line 21 and feeds the pressure medium into the supply pressure circuit 20. In the motor operation of the second operating means 7b, the second operating means 7b is driven on the suction side with pressure medium from the pressure medium reservoir 10. In the motor mode, the second operating element 7b generates a torque on the output shaft 6.

The assistance drive for assisting the already operating internal combustion engine 2 can be realized by an individual motor operation of the first operating device 7a or of the second operating device 7b or by a common motor operation of the first operating device 7a and of the second operating device 7 b. Accordingly, the hydraulic start for starting the start-stop function of the stopped internal combustion engine 2 can be achieved by an individual motor operation of the first operating device 7a or of the second operating device 7b or by a common motor operation of the first operating device 7a and of the second operating device 7 b.

According to the invention, the pressure medium storage device 10 has a first pressure medium storage unit 10a and a second pressure medium storage unit 10 b. A charging valve device 30 is provided, which makes it possible to carry out a charging operation of the first pressure medium storage unit 10a and thus of the first pressure medium storage unit 10a alone, independently of a charging operation of the second pressure medium storage unit 10 b.

In the embodiment shown, the first pressure medium storage unit 10a is formed by a single pressure medium reservoir 10 c. The capacity of the first pressure medium storage unit 10a is designed and adapted to the requirements of the operating device 7 operating as a hydraulic motor as a hydraulic starter for starting the stopped internal combustion engine 2.

In the embodiment shown, the second pressure medium storage unit 10b is formed by at least one pressure medium reservoir 10 d. The total capacity of the first pressure medium storage unit 10a and the second pressure medium storage unit 10b is designed and adapted to the demand of the operating mechanism device 7 operating as a hydraulic motor as a booster drive of the already operating internal combustion engine 2.

The pressure

medium reservoirs

10c, 10d are each designed as a hydraulic reservoir.

In the drive system 1 according to the invention, if the running gear mechanism 7 is used as a hydraulic starter for the stopped internal combustion engine 2, the running gear mechanism 7, which is operated as a hydraulic motor, is first driven exclusively with pressure medium from the first pressure medium storage unit 10 a. The operating mechanism device 7, which operates as a hydraulic motor, is driven by pressure medium from the first pressure medium storage unit 10a alone for such a long time as the pressure in the first pressure medium storage unit 10a is higher than the pressure in the second pressure medium storage unit 10 b. If the pressure of the first pressure medium storage unit 10a drops to the pressure of the second pressure medium storage unit 10b after a certain period of time as a result of the pressure medium being drawn off, the starting process of the internal combustion engine 2 is carried out from this point in time by the operating mechanism device 7 operating as a hydraulic motor, which is driven with pressure medium from the first pressure medium storage unit 10a and the second pressure medium storage unit 10 b.

In the drive system 1 according to the invention, if the running gear mechanism 7 is used as a power-assisted drive for the already operating internal combustion engine 2, the running gear mechanism 7, which operates as a hydraulic motor, is driven with pressure medium from the first pressure medium storage unit 10a and the second pressure medium storage unit 10 b.

For the loading of the pressure medium, the pressure medium reservoir 10 is connected by means of a loading line 31 to the feed line 13 of the first operating means 7a leading to the working fluid pressure device 4.

In the feed line 13, an electrically operable charging valve 32 is provided, which can be actuated in a controlled manner to a throttle position in which the feed line 13 is throttled for pressure build-up. Here, the charging line 31 is connected to the delivery line 13 upstream of the charging valve 32 and further between the charging valve 32 and the priority valve 14.

The charging valve arrangement 30 is connected on the input side to a charging line 31. On the output side, the charging valve device 30 is connected to a first charging branch line 33a of the first pressure medium storage unit 10a and to a second charging branch line 33b of the second pressure medium storage unit 10 b.

The charging valve device 30 of fig. 1 to 3 has a first control position 30a in which the charging line 31 is connected to the first charging branch line 33a and the connection of the charging line 31 to the second charging branch line 33b is blocked. In the first control position 30a, therefore, a loading operation of the first pressure medium storage unit 10a alone is possible.

In fig. 1 and 2, the charging valve device 30 has a second control position 30b in which the charging line 31 is connected to the second charging branch line 33b and the connection of the charging line 31 to the first charging branch line 33a is blocked. Thus, a load-only operation of the second pressure medium storage unit 10b can be achieved in the second control position 30 b.

In fig. 3, the charging valve device 30 has a second control position 30b in which the charging line 31 is connected to the first charging branch line 33a and to the second charging branch line 33 b. In the second control position 30b, therefore, the first pressure medium storage unit 10a and the second pressure medium storage unit 10b can be jointly operated in a load-bearing manner.

In fig. 1 to 3, the charge valve devices 30 are each configured as a switching valve.

In fig. 1 to 3, the loading valve means 30 is operated into a first control position 30a by spring means 35. In fig. 1 to 3, the loading valve arrangement 30 can be electrically operated into the second control position 30 b. For this purpose, an electronic control device 40 is provided, which is connected for control purposes to an electronic operating device 41 (for example a magnet) of the loading valve device 30. In fig. 2, the charging valve arrangement 30 can be hydraulically operated into a second control position 30 b.

In fig. 1 and 2, the loading valve device 30 operates as follows: first, the first pressure medium storage unit 10a is charged with pressure medium, and the second pressure medium storage unit 10b is charged with pressure medium when the first pressure medium storage unit 10a achieves a predetermined charging state (which is sufficient for starting the stopped internal combustion engine by operating the motor of the operating mechanism device 7). For this purpose, the loading valve device 30 can be operated into the second control position 30b depending on the loading pressure of the first pressure medium storage unit 10a and thus the loading state.

For this purpose, the electronic control unit 40 is connected on the input side to the pressure sensor 42a of the first pressure medium reservoir unit 10 a. The pressure sensor 42a is used to monitor the loading pressure and thus the loading state of the first pressure medium storage unit 10 a. The electronic control unit 40 is operatively connected to the pressure sensor 42b of the second pressure medium storage unit 10 b. The pressure sensor 42b is used to monitor the loading pressure and thus the loading state of the second pressure medium storage unit 10 b.

In fig. 2, in order to actuate the loading valve device 30 into the second control position 30b as a function of the loading pressure and thus the loading state of the first pressure medium storage unit 10a, a control pressure line 43 which leads the loading pressure of the first pressure medium storage unit 10a is led to a control pressure surface of the loading valve device 30 which acts in the direction of the second control position 30 b.

In fig. 3, the loading valve arrangement 30 works such that the loading valve arrangement 30 is operated in either the first control position 30a or the second control position 30b depending on the recoverable energy of the drive system 1. For this purpose, the electronic control device 40 for controlling the charging valve device 30 determines the recoverable energy of the drive system 1 from the current operating state of the drive system 1, and, when sufficient recoverable energy has been found for charging the first pressure medium storage unit 10a and the second pressure medium storage unit 10b, the charging valve device 30 is operated into the second control position 30 b.

A delay valve 50 is arranged in the charging line 31, which can be actuated in the throttle position during a braking operation of the vehicle, in order to be able to build up a sufficient braking torque in the event of insufficient charging pressure of the pressure medium reservoir 10. By controlling the delay valve 50 to the throttle position, the pressure in the charging line 30 is regulated according to the desired braking power. The delay valve 50 is connected to the electronic control device 40 for control. By accumulating the pressure in the charging line 31, an additional braking torque can be applied to the output shaft 6, which counteracts the torque acting on the motor drive on the operating pump 5 and thus brakes the vehicle.

A shut-off valve 55, which opens in the direction of the charging valve device 30 and which is configured in the exemplary embodiment shown as a non-return valve, opens in the direction of the charging valve device 30, is arranged in the charging line 31. In the illustrated embodiment, a shut-off valve 55 is arranged in the charging line 31 between the delay valve 50 and the charging valve arrangement 30.

The first pressure medium storage unit 10a is connected to a first discharge line 60a, which is connectable to the suction side of the operating mechanism device 7. Correspondingly, the second pressure medium storage unit 10b is connected to a second discharge line 60b, which is connectable to the suction side of the operating mechanism device 7. The

relief lines

60a, 60b are connected to each other and to the suction side of the actuator device 7, and a shut-off valve 61, which is shut off in the direction of the second pressure medium reservoir unit 10b, is arranged in the second relief line 60 b. In the exemplary embodiment shown, the shut-off valve 61 is designed as a non-return valve which shuts off in the direction of the second pressure medium storage unit 10 b.

The connection between the pressure medium reservoir 10 and the suction side of the actuator device 7 for the motor operation of the actuator device 7 can be controlled by means of an electrically operable control valve device 70. In the illustrated embodiment (in which the first operating mechanism 7a and the second operating mechanism 7b can each be operated as hydraulic motors), the control valve device 70 includes: a first control valve 70a, by means of which the connection between the pressure medium reservoir 10 and the suction side of the first operating member 7a can be controlled; a second control valve 70b, by means of which the connection between the pressure medium reservoir 10 and the suction side of the second operating member 7b can be controlled. The

control valves

70a, 70b each have a shut-off position 71a and a flow-through position 71b, wherein the shut-off position 71a is preferably embodied as a leak-proof seal and has a shut-off valve which is shut off in the direction of the respective operating means 7a, 7 b.

The control valve 70a is arranged in a connecting line 75 which leads from the

interconnected relief lines

60a, 60b to the suction line 11, which suction line 11 leads to the suction side of the first operating means 7 a.

A shut-off valve 76, which is shut off in the direction of the container 12 and is preferably designed as a non-return valve 77 shut off in the direction of the container 12, is arranged in the suction line 11 of the first operating means 7 a.

The control valve 70b is arranged in a connecting line 78 which leads from the

interconnected discharge lines

60a, 60b to the suction line 21, which suction line 21 leads to the suction side of the second operating means 7 b.

A shut-off valve 79, which is shut off in the direction of the container 12 and is preferably designed as a non-return valve 80, which is shut off in the direction of the container 12, is arranged in the suction line 21 of the second operating means 7 b.

The electronic control device 40 is connected to the

control valves

70a and 70b for control. In addition, the electronic control device 40 controls the charge valve 32 and the retard valve 50.

In order to ensure the pressure of the pressure medium reservoir 10, a pressure limiting valve 85 is provided. Fig. 1 to 3 also show a discharge valve 86, by means of which the pressure medium reservoir 10 can be relieved to achieve a pressure-free state.

In the drive system 1 according to the invention of fig. 1 to 3, the charging operation of the pressure medium reservoir 10 is preferably carried out during a braking state of the vehicle and during a braking energy recovery of the vehicle, by using the kinetic energy of the braking vehicle for charging the pressure medium reservoir 10 and thus for energy recovery. In the event of a braking of the vehicle by means of the hydrostatic travel drive 3, the operating pump 5 is operated as a motor which drives the operating element 7a which operates as a pump, so that the pressure medium reservoir 10 can be charged with pressure medium via the charging valve 32 which is controlled in the direction of the throttle position and via the charging line 31. The torque received in the braking state can be set at will depending on the current loading pressure of the pressure medium reservoir 10 by means of a continuously adjustable displacement volume of the actuating mechanism 7a, which is designed as an adjustable actuating mechanism. If the current charging pressure of the pressure medium reservoir 10 is not sufficient to build up the required braking torque for vehicle braking, a corresponding pressure can be built up in the charging line 31 by controlling the delay valve 50 arranged in the charging line 31 into the throttle position in order to build up the required braking torque and the desired braking power. Alternatively or additionally, a mechanical vehicle brake, not shown in detail, can be used in an auxiliary manner.

Alternatively or additionally, in the drive system 1 according to the invention of fig. 1 to 3, the charging operation of the pressure medium reservoir 10 is carried out in the energy recovery operation of the working hydraulic device 4 (for example in the lowering operation and in the potential energy recovery of the lifting drive), so that the potential energy of the load received by means of the lifting drive is used for charging the pressure medium reservoir 10 and thus for energy recovery.

Alternatively, the pressure medium reservoir 10 is initially charged with energy from the internal combustion engine 2, in that the internal combustion engine 2 drives an operating means 7a which operates as a pump and which delivers pressure medium to the pressure medium reservoir 10 via a charging line 31.

In the drive system according to the invention of fig. 1 to 3, it is possible to implement by dividing the provided capacity of the pressure medium storage device 10 into a first pressure medium storage unit 10a and a second pressure medium storage unit 10b and by means of the loading valve device 30: in the loading mode of the pressure medium reservoir device 10, in the first control position 30a of the loading valve device 30, only the first pressure medium reservoir unit 10a is loaded, which serves to drive the operating mechanism device 7 as a hydraulic starter of the stopped internal combustion engine for the start-stop function.

Here, in fig. 1 and 2, the loading valve device 30 is operated by a spring 35 into a first control position 30a, so that the first pressure medium storage unit 10a is first loaded. As soon as the loading pressure of the first loading valve device 30 has achieved a predefined loading state, which in combination with the motor operation of the operating mechanism device 7 enables the stopped internal combustion engine 2 to be started, the loading valve device 30 is operated into the second control position 30b in order to load the second pressure medium storage unit 10b after the loading process of the first pressure medium storage unit 10 a. For this purpose, in fig. 1 and 2, the charge valve device 30 is controlled in the direction of the second control position 30b as a function of the charge pressure of the first pressure medium storage unit 10 a. For this purpose, in fig. 1, the electronic control device 40 detects the charging pressure of the first pressure medium storage unit 10a by means of the pressure sensor 42a and controls the charging valve device 30.

In fig. 1 and 2, therefore, in the charging mode, the first pressure medium storage unit 10a is initially charged with pressure medium and, if the charging state of the first pressure medium storage unit 10a is sufficient for a starting process of the stopped internal combustion engine 2 in the motor mode of the operating mechanism device 7, is switched to the second pressure medium storage unit 10b, so that the charging volume flow is used for charging the second pressure medium storage unit 10b, provided that sufficient recoverable energy is still available for conversion in the charging mode by means of recoverable energy.

In fig. 3, the loading valve arrangement 30 is operated and controlled according to the recoverable energy of the drive system 1. Here, the recoverable energy (e.g. converted kinetic and/or potential energy) is determined by the electronic control device 40 and controls the loading valve device 30, depending on the current operating state of the vehicle. If the electronic control device 40 determines that the currently converted recoverable energy is sufficient to load the total capacity of the pressure medium storage device 10 to a loading pressure sufficient for the starting process of the stopped internal combustion engine 2 by the motor operation of the operating mechanism device 7, the loading valve device 30 is operated into the second control position 30b, so that the two pressure medium storage units 10a, 10b are loaded. If the electronic control device 40 determines that the currently converted recoverable energy is low, the charging valve device 30 is in a first control position 30a, in which only the first pressure medium storage unit 10a is charged with pressure medium.

In the drive system 1 according to the invention, the electronic control device 40 is designed in such a way that the loading state of the first pressure medium reservoir unit 10a is determined in the range of the start-stop function during the interruption of operation before the internal combustion engine 2 is stopped. If the first pressure medium reservoir unit 10a is not yet loaded into the loading state required for the starting process of the internal combustion engine 2 by the motor operation of the operating mechanism device 7 (for example, by means of recoverable energy), the electronic control device 40 causes the loading operation of the first pressure medium reservoir unit 10a to be carried out into the loading state required for the starting process of the internal combustion engine 2 (for example, initially by means of energy of the internal combustion engine 2) for enabling the internal combustion engine 2 to be stopped at rest and then started again by the motor operation of the operating mechanism device 7.

In the electronic control device 40, corresponding countermeasures for loading the first pressure medium storage unit 10a and the second pressure medium storage unit 10b are stored according to the respective operating state of the vehicle. The loading state of the two pressure medium storage units 10a, 10b can be detected and monitored by the electronic control device 40 using the two

pressure sensors

42a, 42 b.

By dividing the total capacity of the pressure medium reservoir 10 into the two pressure medium reservoir units 10a, 10b described above and by designing the capacity of the first pressure medium reservoir unit 10a such that the requirement of the operating device 7 as a start-stop function for a hydraulic starter for a stopped internal combustion engine 2 is met, in combination with the charge valve device 30, the charge process of the pressure medium reservoir 10 can be specifically limited to the first pressure medium reservoir unit 10a and thus the first pressure medium reservoir unit 10a to a smaller capacity adapted to the start-stop function, depending on the current operating state of the vehicle. Therefore, what is avoidable in the drive system 1 according to the invention is: before the internal combustion engine is stopped, the set total capacity of the pressure medium reservoir 10 must be loaded in the start-stop function range to the loading state required for the starting process of the internal combustion engine 2. The excess capacity of the pressure medium storage device 10 (i.e. the capacity of the second pressure medium storage unit 10b) which is not required for starting the internal combustion engine is therefore not loaded with energy intensive force (for example initially with the aid of energy from the internal combustion engine 2) in order to ensure that the starting process of the stopped internal combustion engine 2 is carried out by the motoring of the operating mechanism device 7. The drive system 1 according to the invention is therefore improved with regard to energy saving in the start-stop function.

With the drive system 1 according to the invention it is thus possible to realize: even in operating states in which only a small amount of recoverable energy is converted, the first pressure medium storage unit 10a provided for the starting process of the internal combustion engine 2 can be charged with recoverable energy into a charging state required for the starting process of the internal combustion engine 2, or the first pressure medium storage unit 10a provided for the starting process of the internal combustion engine 2 can be charged with a small amount of initial energy into a charging state required for the starting process of the internal combustion engine 2. The drive system 1 according to the invention thus enables: in vehicles whose use is characterized by conversion of small amounts of recoverable energy, the start-stop function is implemented by means of a hydraulic starter of the internal combustion engine 2 without the need for energy-intensive loading of the total capacity of the pressure medium storage device 10 provided for additional power-assisted driving of the already operating internal combustion engine 2 by initial energy.

It goes without saying that the invention is not limited to the configuration of the hybrid system running gear arrangement 7 and the arrangement of the running gear arrangement 7 in the drive train of the internal combustion engine 2 according to fig. 1 to 3. The operating device 7 can alternatively comprise only a single operating device which can be operated as a hydraulic motor, which can be arranged at any desired point in the drive train of the internal combustion engine 2 formed by the output shaft 6 as an additional energy source or as an auxiliary drive in driving connection with the internal combustion engine 2.

Claims

1. A hydrostatic drive system (1) having a hydrostatic operating mechanism device (7; 7a, 7b) which is in driving connection with an internal combustion engine (2), wherein the operating mechanism device (7; 7a, 7b) is operated in an open circuit and is connected on the input side on the suction side to a tank (12) by means of a suction line (11), wherein the hydrostatic operating mechanism device (7; 7a, 7b) can be operated as a hydraulic motor which can be driven by means of a pressure medium from a pressure medium storage device (10), wherein during operation of the hydraulic motor of the operating mechanism device (7; 7a, 7b) is driven on the suction side by means of the pressure medium from the pressure medium storage device (10), wherein the operating mechanism device (7; 7a, 7b) operating as a hydraulic motor is configured such that: a power-assisted drive for assisting a running internal combustion engine (2) and a hydraulic starter for a start-stop function of a stopped internal combustion engine (2), characterized in that the pressure medium storage device (10) containing the pressure medium for driving the actuator device (7; 7a, 7b) operating as a hydraulic motor on the suction side has a first pressure medium storage unit (10a) and a second pressure medium storage unit (10b), wherein the running gear device, which operates in the operation of the hydraulic motor, is driven on the suction side with pressure medium from the first pressure medium storage unit and the second pressure medium storage unit, wherein a loading valve device (30) is provided, which can carry out a loading operation of the first pressure medium storage unit (10a) independently of a loading operation of the second pressure medium storage unit (10 b).

2. The hydrostatic drive system as claimed in claim 1, characterized in that the first pressure medium storage unit (10a) has a pressure medium accumulator (10c), the capacity of which is designed as a hydraulic starter for starting the stopped internal combustion engine (2) as a function of the requirements of the operating mechanism device (7; 7a, 7 b).

3. The hydrostatic drive system according to claim 1 or 2, characterized in that the second pressure medium storage unit (10b) has at least one pressure medium reservoir (10d), wherein the total capacity of the first pressure medium storage unit (10a) and the second pressure medium storage unit (10b) is designed as a booster drive as a function of the requirements of the running gear arrangement (7; 7a, 7 b).

4. The hydrostatic drive system according to claim 1 or 2, characterized in that the operating mechanism device (7; 7a, 7b) which operates as a hydraulic starter of the stopped internal combustion engine (2) is driven with pressure medium from the first pressure medium storage unit (10 a).

5. The hydrostatic drive system as claimed in claim 1 or 2, characterized in that the operating mechanism device (7; 7a, 7b) which operates as a hydraulic starter of the stopped internal combustion engine (2) is first driven with pressure medium from the first pressure medium storage unit (10a) until the pressure of the first pressure medium storage unit (10a) corresponds to the pressure of the second pressure medium storage unit (10b), and subsequently the operating mechanism device (7; 7a, 7b) which operates as a hydraulic starter of the stopped internal combustion engine (2) is driven with pressure medium from the first pressure medium storage unit (10a) and the second pressure medium storage unit (10 b).

6. The hydrostatic drive system as claimed in claim 1 or 2, characterized in that the running gear arrangement (7; 7a, 7b) which operates as a booster drive of the already operating internal combustion engine (2) is driven with pressure medium from the first pressure medium storage unit (10a) and the second pressure medium storage unit (10 b).

7. The hydrostatic drive system as claimed in claim 1 or 2, characterized in that the charge valve device (30) is connected on the input side to a charge line (31) and on the output side to a first charge branch line (33a) of the first pressure medium storage unit (10a) and to a second charge branch line (33b) of the second pressure medium storage unit (10 b).

8. The hydrostatic drive system of claim 7, characterized in that the charging valve device (30) has a first control position (30a) in which the charging line (31) is connected to the first charging branch line (33a) and the connection of the charging line (31) to the second charging branch line (33b) is blocked.

9. The hydrostatic drive system of claim 8, characterized in that the charging valve device (30) has a second control position (30b) in which the charging line (31) is connected to the second charging branch line (33b) and the connection of the charging line (31) to the first charging branch line (33a) is blocked.

10. The hydrostatic drive system of claim 7, wherein the charge valve device (30) operates as follows: first, the first pressure medium storage unit (10a) is loaded with pressure medium, and, when the first pressure medium storage unit (10a) has achieved a predefined loading state, the second pressure medium storage unit (10b) is loaded with pressure medium.

11. The hydrostatic drive system of claim 8, characterized in that the charging valve device (30) has a second control position (30b) in which the charging line (31) is connected to the first charging branch line (33a) and to the second charging branch line (33 b).

12. The hydrostatic drive system of claim 11, wherein the charge valve device (30) operates as follows: the loading valve arrangement (30) is operated to the first control position (30a) or the second control position (30b) depending on the recoverable energy of the drive system (1).

13. The hydrostatic drive system of claim 1 or 2, characterized in that the charge valve device (30) is configured as a switching valve.

14. The hydrostatic drive system as claimed in claim 1 or 2, characterized in that the charge valve device (30) is operable as a function of a charge pressure of the first pressure medium storage unit (10 a).

15. The hydrostatic drive system of claim 1 or 2, wherein the charge valve arrangement is hydraulically operable.

16. The hydrostatic drive system according to claim 1 or 2, characterized in that the charge valve device (30) is electrically operable and is operatively connected to an electronic control device (40) for operation.

17. The hydrostatic drive system according to claim 16, characterized in that the electronic control device (40) is operatively connected on the input side to the pressure sensor (42a) of the first pressure medium storage unit (10a) and to the pressure sensor (42b) of the second pressure medium storage unit (10 b).

18. The hydrostatic drive system of claim 16, characterized in that the charge valve device (30) is connected on the input side to a charge line (31), the charge valve device (30) having a second control position (30b), in the second control position, the charging line (31) is connected to a first charging branch line (33a) of the first pressure medium storage unit (10a) and to a second charging branch line (33b) of the second pressure medium storage unit (10b), and the electronic control device (40) determines the recoverable energy of the drive system (1), and when it is found that the recoverable energy is sufficient for the loading of the first pressure medium storage unit (10a) and the second pressure medium storage unit (10b), the electronic control device operates the loading valve device (30) into the second control position (30 b).

19. The hydrostatic drive system of claim 9 or 11, characterized in that the charge valve device (30) is operated by a spring device (35) into the first control position (30a) and can be operated hydraulically or electrically into the second control position (30 b).

20. The hydrostatic drive system of claim 7, characterized in that a delay valve (50) is provided in the charge line (31).

21. The hydrostatic drive system as recited in claim 7, characterized in that a shut-off valve (55) which opens in the direction of the charge valve device (30) is provided in the charge line (31).

22. The hydrostatic drive system according to claim 1 or 2, characterized in that the first pressure medium storage unit (10a) is connected to a first discharge line (60a) and the second pressure medium storage unit (10b) is connected to a second discharge line (60b), wherein the discharge lines (60a, 60b) are connected to one another and to the operating mechanism device (7; 7a, 7b), wherein a shut-off valve (61) is provided in the second discharge line (60b) and is shut off in the direction of the second pressure medium storage unit (10 b).

23. The hydrostatic drive system of claim 21, wherein the shut-off valve (55) is a check valve.

24. The hydrostatic drive system of claim 22, wherein the shut-off valve (61) is a check valve.

25. Vehicle with a hydrostatic drive system according to one of the preceding claims, wherein the vehicle has a travel drive (3) and/or a working hydraulic device (4), characterized in that the charging operation of the pressure medium storage device (10) is carried out by recovering energy in a braking operation of the vehicle and/or in an energy recovery operation of the working hydraulic device (4).

26. Vehicle according to claim 25, characterized in that an electronic control device (40) is provided, which controls the loading valve device (30), wherein the electronic control device (40) is configured to: before the internal combustion engine (2) is stopped, the state of charge of the first pressure medium storage unit (10a) is checked during a power interruption.

27. Vehicle according to claim 26, characterized in that said electronic control device (40) is configured to: when it is detected that the loading state of the first pressure medium storage unit (10a) is insufficient for a starting process of the internal combustion engine (2), a loading operation of the first pressure medium storage unit (10a) is carried out.

28. Vehicle according to claim 26 or 27, characterized in that said electronic control device (40) is configured to: the electronic control device (40) determines recoverable energy from the current operating state of the vehicle and controls the loading valve device (30).