Work machine with energy recuperation and method for operating a work machine

Abstract

The invention relates to a work machine comprising an internal combustion engine and at least one secondary pneumatic or hydraulic working circuit, wherein during operation of the secondary working circuit energy is recuperated and can be fed to a pressure accumulator of the work machine for energy storage, characterized in that at least one auxiliary compressor is provided which can be driven by the energy stored in the pressure accumulator, and an engine control is provided and configured to detect a highly dynamic increase in the power requirement of the internal combustion engine and, if necessary, to generate additional charge air by means of the auxiliary compressor, which is fed to the charge air path of the internal combustion engine in addition to the regular charge air flow of the internal combustion engine.

Description

[0001] The invention relates to a working machine with energy recuperation and a method for operating such a working machine

[0002] In vehicle technology, energy recuperation and its reuse have long been state-of-the-art. The combination of an internal combustion engine with an electric system is also the most common form of hybridization. There are varying degrees of hybridization. In a so-called micro-hybrid vehicle, comparatively low levels of power can be recuperated compared to the power of its internal combustion engine. Therefore, the recuperation energy is not used as propulsion energy, but exclusively to power secondary functions, such as the electric starter of the internal combustion engine and other electrical consumers in the vehicle.Even during braking maneuvers that exceed the time-related kinetic energy generated during a maneuver, only a small portion of the excess power can be recuperated. Despite the fact that only a very small portion of the theoretically available energy can be recovered, a micro-hybrid vehicle also has a justification for its existence within its framework. For example, its additional acquisition costs, additional weight, and additional resource consumption are comparatively low compared to a comparable vehicle, which, apart from the alternator, has no means of deriving any additional recuperation power.

[0003] For vehicles that already fall into the next higher category of so-called mild hybrid vehicles within hybridization, considerable additional effort is required to enable purely electric-powered maneuvering, to provide a certain amount of electric-powered propulsion in addition to that available from the combustion engine, and to perform recuperation whose upper performance limit exceeds that of a micro-hybrid. The following text will omit the relevant classification.

[0004] With regard to possible combinations of drive units, there is not only the combination of an internal combustion engine with an electric motor, or more precisely with an electric drive system, but also combinations of an internal combustion engine with a flywheel energy storage system or a hydraulic drive system including a pressure accumulator. The latter category has a particularly high potential for success in the field of mobile machinery, since, unlike in the passenger car sector, for example, high hydraulic power flows and corresponding hydraulic systems are already present. For example, the functional and beneficial integration of a pressure accumulator is known for a serially constructed diesel engine-hydraulic power path of a basic system, e.g., a diesel engine that drives a hydraulic pump to provide hydraulic power for a lifting cylinder or a hydraulic motor.

[0005] One example of a machine that allows for effective energy recuperation during a work cycle is an excavator. Here, the operation of the so-called lift is predestined for energy recuperation. (The lift or boom refers to the segment of the work equipment in question attached to the uppercarriage; the other two segments are called the bucket and stick.) When lifting this work equipment, a correspondingly high amount of energy must be supplied to the boom hydraulic cylinder in order to achieve the required vertical positioning of the bucket via a pivoting movement of the boom with the cooperation of the stick and bucket. When one considers the length of the possible lever arm and the fact that the bucket is filled with bulk material during lifting, it becomes clear that very high power is required for the lifting process described.During lowering, even though the bulk material is usually no longer inside the bucket, high levels of power are available from which recuperation energy can be drawn. In the majority of excavator applications, high levels of power are also required for the bucket to penetrate the bulk material or excavated material. The sub-sequences of a work cycle considered, starting with the lowering of the working equipment, the subsequent penetration of the bucket into the bulk material and the subsequent raising of the working equipment including the picked-up bulk material, result in the following power profile in the above-mentioned sequence and in a temporally parallel manner to the work sections: At the beginning of the lowering, at least a low power requirement is available and towards the end of the lowering at the latest, power is generated which can be recuperated. During the penetration process into the bulk material orInstead, the insertion of the excavated material requires high to very high power, which should be available as quickly as possible. Lifting also requires high power.

[0006] However, the short-term increase in power demand (highly dynamic power increase) that occurs during a working cycle poses a problem for certain engine concepts, because a significantly increased amount of air must be supplied to the combustion chambers of the internal combustion engine within an extremely short response time, which is often impossible to achieve through the engine's regular air path. This problem is known, for example, as turbo lag.

[0007] US 2010 / 0236232A1 discloses a work machine that recovers hydraulic energy when lowering a load. In this known system, the previously recovered hydraulic energy stored in a pressure accumulator is reused to drive a hydraulic motor, which then supplies mechanical power directly to the machine's drive system in the form of an internal combustion engine. However, such a system is comparatively complex to implement.

[0008] The object of the invention is therefore to provide a working machine or a method that can overcome the aforementioned problem.

[0009] The above object is achieved by a work machine according to the features of claim 1 or by a method for operating a work machine according to the features of claim 16.

[0010] The inventive approach of the application consists in making the temporarily required additional charge air, which cannot be provided via the regular charge air path in a sufficiently short time, available in another way, whereby the necessary modification of the working machine or the combustion engine used requires comparatively low requirements in terms of provision and integration and the use is therefore particularly energy-efficient.

[0011] According to the invention, a work machine is therefore proposed which, in addition to an internal combustion engine, comprises at least one secondary pneumatic or hydraulic working circuit. During operation of the work machine, energy from the secondary working circuit can be recuperated and fed to a pressure accumulator of the work machine for storage in the form of compression energy. According to the invention, the work machine comprises at least one auxiliary compressor which can be driven by the energy stored in the pressure accumulator. Said auxiliary compressor is to be understood as an additional compressor to the regular charge air path of the internal combustion engine. This means that the auxiliary compressor should only be used as an auxiliary function under special conditions and should provide compressed additional charge air to the regular air path of the internal combustion engine. The regular air path comprises the air intake and the corresponding supply of combustion air to the combustion chambers of the internal combustion engine.In the regular charge air path, compression of the intake charge air can already be performed, for example, by means of an exhaust gas turbocharger or another driven compressor. The auxiliary compressor of the present invention is therefore to be understood as a compressor additional to any compression component of the regular charge air path.

[0012] The work machine further comprises an engine control system configured to activate the auxiliary compressor in the event of a highly dynamic increase in the power demand on the internal combustion engine in order to generate compressed additional charge air and to supply this to the regular charge air path of the internal combustion engine, i.e., in addition to the regular charge air flow. According to the invention, additional charge air is to be made available to the internal combustion engine using the energy stored in the pressure accumulator in the event of a highly dynamic increase in the power demand, and this until the regular air path of the internal combustion engine can provide a charge air flow of sufficient magnitude to reach or maintain the currently desired engine operating point. In other words, the additional charge air generated using the recuperated energy is only provided temporarily and briefly for a transitional phase of the power increase.A typical example is bridging the so-called turbo lag. An example of a highly dynamic increase in power demand is, for example, a sharp increase in power demand due to work to be performed by the secondary circuit, whereby such a power demand cannot be provided without delay by the combustion engine without the additional charge air.

[0013] Advantageously, a first hydraulic displacement unit can be provided, the pressure output of which is connected or connectable to an inlet of the pressure accumulator. A liquid fluid, preferably an oil, in particular hydraulic oil, can be supplied to the pressure accumulator by means of the first displacement unit, whereby compression energy can be built up and stored within the pressure accumulator.

[0014] Recuperation energy can be supplied to the pressure accumulator directly from an actuator in the working circuit, for example, by hydraulic fluid flowing from the cylinder into the pressure accumulator when a hydraulic cylinder is actuated. However, energy recuperation can also occur indirectly by the first hydraulic displacement unit operating in pump mode and, during certain operating states in which kinetic energy must be extracted from the overall system, supplying the corresponding recuperation power via its drive shaft. The first displacement unit driven in this way then pumps fluid into the pressure accumulator. For example, the first hydraulic displacement unit can be integrated into the overall system in such a way that it can only draw power from a passively moving part in order to convert this power into hydraulic power.This could be an axle used to move the working machine, which cannot be actively driven but is only moved passively and the drive shaft of the displacement unit can be driven.

[0015] However, the hydraulic displacement unit 12 can also be activated during increased operating hours of the internal combustion engine 10, thus incurring increased fuel consumption, in order to prevent the pressure within the pressure accumulator 13 from falling below a specified minimum level. This ensures that a sufficient energy reserve is available in the pressure accumulator for the temporary provision of the additional charge air even if no or less energy is currently being recuperated by the secondary working circuit.

[0016] The first hydraulic displacement unit can, for example, be driven by an auxiliary drive of the combustion engine. It is also conceivable to connect the first displacement unit via a pump distribution gear driven by the combustion engine. Alternatively or additionally, the first hydraulic displacement unit could also be driven independently of the combustion engine by an auxiliary drive, such as an electric drive.

[0017] The first displacement unit can be a displacement unit that operates rotary in pump mode, such as an axial piston or in-line piston pump.

[0018] According to an advantageous embodiment, a second hydraulic displacement unit can be provided, which can be driven using the compression energy present in the pressure accumulator, and whose mechanical output power drives the auxiliary compressor. The second displacement unit can therefore be a hydraulic motor, preferably a high-speed hydraulic motor. In an advantageous embodiment, the hydraulic motor can be an axial piston machine or a gear pump suitable for operation in the required high-speed range. A transmission gear can be connected between the second displacement unit and the auxiliary compressor.

[0019] It is particularly preferred if the second hydraulic displacement unit can also be operated in pump mode. This also enables recuperation of the rotational energy of the auxiliary compressor into the pressure accumulator, for example, when the compressor is shut down and drains.

[0020] The auxiliary compressor can be a volumetric compressor, preferably an internal gear compressor or a gerotor compressor. The pressure accumulator used can be a bladder accumulator, a diaphragm accumulator, or a dual-piston accumulator. Any type of accumulator is conceivable, provided it is suitable for absorbing a sufficient amount of the energy that can be recovered in the secondary working circuit.

[0021] It is sensible for an internal combustion engine according to the invention to have such an intercooler, which can be used to cool the charge air flowing through the auxiliary compressor. The auxiliary compressor can have a dedicated, downstream intercooler. However, it is also conceivable to feed the generated additional charge air to an integral intercooler of the regular charge air path, i.e., the additional charge air is fed to the regular charge air path upstream of any intercooler installed there.

[0022] If the internal combustion engine already includes charge air compression, particularly in the form of an exhaust gas turbocharger, it is advisable to feed the additional charge air generated by the auxiliary compressor upstream of the existing compression unit of the exhaust gas turbocharger associated with the internal combustion engine. If the internal combustion engine's regular air path includes a throttle valve, the additional charge air from the auxiliary compressor is preferably fed downstream of the throttle valve into the regular air path.

[0023] According to an advantageous embodiment of the invention, the pressure accumulator is connected to the secondary working circuit of the working machine via a valve arrangement, preferably at least one switchable directional control valve. Ideally, at least three valve positions are possible via the one or more valves. According to a first valve position, liquid fluid from the secondary working circuit can be supplied to the pressure accumulator as part of energy recuperation or from the first displacement unit. In a second valve position, liquid fluid can be withdrawn from the pressure accumulator to drive the compressor or the second displacement unit. According to a third valve position, neither liquid fluid can be withdrawn from the pressure accumulator nor can liquid fluid be supplied to the pressure accumulator. In a preferred embodiment, the pressure accumulator is connected via a three-way valve that can implement the aforementioned three valve positions.The pressure accumulator therefore comprises only a single port, which is connected to the relevant port of the three-way valve.

[0024] Alternatively, it is also conceivable for the pressure accumulator to be connected via multiple fluid connections. A first connection of the pressure accumulator is indirectly connected to the high-pressure outlet of the first displacement unit or to a line of the secondary working circuit, via which recovered energy can be fed into the pressure accumulator. It is expedient to integrate a check valve or a functionally similar component between the connection of the pressure accumulator and the first displacement unit or said line for energy recovery in order to prevent backflow of fluid from the pressure accumulator towards the first displacement unit or the working circuit. A second fluid connection of the pressure accumulator is preferably connected via a valve to the high-pressure inlet of the second displacement unit.The valve, which is fluidically integrated between the second displacement unit and the pressure accumulator, can be remotely set to a first switching state in which no liquid fluid flows from the pressure accumulator toward the second displacement unit, and to a second switching state in which liquid fluid flows from the pressure accumulator toward the second displacement unit. Preferably, this embodiment also provides for a state in which the pressure accumulator can neither absorb nor release fluid, regardless of the prevailing pressure conditions, to be set by appropriately controlling the valves and components.

[0025] According to an advantageous embodiment of the invention, the first displacement unit can be placed into an idle operating state in the event that no liquid fluid is to be supplied to the pressure accumulator at any time. In this state, the power consumption of the first displacement unit from the drive system is significantly lower than during the first displacement unit's operating mode. Such an implementation is conceivable using a hydraulic valve, via which the relevant fluid flow through the displacement unit can be reduced or completely blocked. Such a hydraulic valve enables (i) opening and holding open or (ii) closing and holding closed by remote control, depending on the requirements.

[0026] Alternatively, it can also be provided that the first displacement unit can be mechanically decoupled from its drive shaft, preferably via a magnetic coupling. The coupling used can preferably assume the states (i) momentary opening, (ii) keeping open, (iii) momentary closing, and (iv) keeping closed.

[0027] The secondary working circuit can be an open or closed hydraulic circuit. The work machine can be used on-road or off-road. Furthermore, it can be a mobile work machine or a stationary work machine.

[0028] In addition to the work machine according to the invention, the present invention also relates to a method for operating a work machine, in particular a work machine according to the present invention. According to the invention, energy is recuperated during operation of the secondary working circuit and stored in a pressure accumulator of the work machine. The energy stored in the pressure accumulator can then be used to drive an auxiliary compressor of the work machine, wherein additional charge air is generated by means of the auxiliary compressor, which is temporarily supplied to the internal combustion engine as additional charge air to the air path of the internal combustion engine, specifically when a highly dynamic increase in the power requirement of the internal combustion engine is detected. If there is a sharp increase in the power requirement, e.g.Due to work to be performed by the secondary working circuit, this power requirement often cannot be provided without delay by the combustion engine, for example, due to or caused by an existing turbo lag. According to the method according to the invention, additional charge air is provided by the auxiliary compressor for such a case. Since the auxiliary compressor is operated using stored energy from the pressure accumulator, this additional charge air is available almost immediately.

[0029] Under the assumption that the engine design is not determined by the maximum power but primarily by the engine dynamics, the method according to the invention also allows a "downsizing" of the combustion engines used, since these can achieve an increase in engine dynamics by means of the proposed method.

[0030] If the combustion engine can meet the current power requirement without drawing additional charge air, the existing rotational energy of the auxiliary compressor is preferably recuperated into the pressure accumulator using the relevant conversion chain, e.g. by the second displacement unit operating in pump mode to drive the auxiliary compressor and pumping hydraulic fluid into the pressure accumulator.

[0031] Preferably, a first displacement unit is used to charge the pressure accumulator even in the event of an insufficient amount of recuperation energy. Since such a first displacement unit is preferably driven by a power take-off drive of the internal combustion engine, via a pump distribution gear driven by the internal combustion engine, the first displacement unit should have the lowest possible power consumption when not in use. It is preferred if the first hydraulic displacement unit has an idle power consumption of less than 10%, preferably less than 5%, and particularly preferably less than 2%, relative to its power consumption during full-load operation.

[0032] The process is particularly advantageous when the internal combustion engine is operated with a fuel containing molecular hydrogen. For example, the fuel used contains at least 50% molecular hydrogen, or pure hydrogen is supplied to the internal combustion engine as fuel.

[0033] According to a preferred embodiment of the method, the internal combustion engine is operated with a lambda combustion air ratio that does not fall below a defined limit of at least 1.5 during operation, or at least does not fall below it permanently. Preferably, the limit is at least 2.0 and particularly preferably at least 2.5.

[0034] The concept of the so-called lean-burn engine, i.e., an internal combustion engine operating with a high air / fuel ratio (lambda), is well known. The presence of a combustion air / fuel ratio of lambda = 2 within an engine's combustion chamber means that, for complete combustion of the fuel (e.g., hydrogen), there is twice the amount of air or twice the amount of oxygen than would theoretically be required for complete combustion of the total amount of fuel present.

[0035] The operation of a hydrogen engine is fundamentally dependent on a high air-fuel ratio and also offers potential advantages. In the range of a roughly balanced air-fuel ratio, a hydrogen-powered internal combustion engine exhibits a comparatively low knock limit. A significantly higher knock limit only occurs in areas with a comparatively large deviation from the stoichiometric fuel-air ratio. In internal combustion engine applications with a proportion of molecular hydrogen significantly above the stoichiometric fuel-air ratio, the risk of misfiring only arises with an extremely high hydrogen excess, which is far above the corresponding operating limit for methane.In contrast to the combustion of fuels containing carbon, the sharply increasing emission of unburned hydrocarbons during combustion of molecular hydrogen does not pose a special requirement for exhaust gas aftertreatment. Furthermore, the use of such fuels, or fuel blends, in combustion engines, which contain an increasingly high proportion of molecular hydrogen, results in a significant reduction in NOx emissions and a tendency towards an increase in engine efficiency.

[0036] In order to be able to permanently utilize these advantages in a dynamically operated hydrogen engine, as well as the resulting consequential advantages of a respective reduction in the size of the exhaust gas aftertreatment system and the amount of reducing agent used to reduce nitrogen oxides, the air supply in a highly dynamically operated hydrogen engine must be able to be increased in line with the capacity to increase the quantity of hydrogen supplied, even in the case of transiently pronounced high power increases. (Although hydrogen is known to be a gaseous fuel, its high capacity to increase the quantity over time does not represent a major additional requirement, at least if the hydrogen available from the on-board tank has a high pressure level.) The air quantity required here, which can be increased very sharply in the short term, is ensured by the inventive extension of the working machine by means of the auxiliary compressor using the inventive method.

[0037] According to a further advantageous embodiment of the method, the method according to the invention allows a reduction in the engine speed during partial load operation of the internal combustion engine, since additional charge air can be provided by the auxiliary compressor when the power requirements of the internal combustion engine dynamically increase. The reduction in the engine speed is logically determined dynamically depending on the compression energy available in the pressure accumulator. In particular, a reduction in the engine speed is only carried out if the charge level of the pressure accumulator does not fall below a lower limit.

[0038] With increasing storage volume, the reduction in speed can also be increased.

[0039] For example, in a liquid-fueled work machine designed according to the invention, which in particular includes a diesel engine as the internal combustion engine, the potential increase in dynamic capability enabled by the invention can preferably be used primarily for "downspeeding." Accordingly, in the lower and middle operating range of its utilization, the internal combustion engine is operated at a reduced engine speed. This means that the engine speed is lower than the speed at which a conventional work machine without an auxiliary compressor operates in a comparable application. In other words: If the dynamic capability of a particular existing engine is considered sufficiently high, this or the work machine can be enhanced according to the invention. During its operation, the speed spectrum can then be shifted to a specific, lower level while maintaining its dynamic capability.Overall, the implementation of the invention opens up a certain gain, which can be used more to increase engine dynamics or more to increase energy efficiency, depending on the user's preference.

[0040] In the work machine according to the invention or in the method according to the invention, the energy recuperated from the secondary working circuit into the pressure accumulator can be obtained, for example, from a translational movement function of a single actuator of the secondary working circuit. Such an actuator is, for example, a hydraulic cylinder that actuates a segment of a lever arm of the work machine. Energy recuperation is also conceivable from a rotating movement function of a single actuator of the secondary working circuit, e.g., from an axial piston machine that causes the acceleration and deceleration of the rotary movement of a superstructure of the work machine. Energy recuperation from a drive system of the work machine that serves for the translational movement of the work machine is also possible.

[0041] Further advantages and features of the invention will be described in more detail below using possible embodiments. They show: Figure 1: a basic circuit diagram of the invention according to a possible embodiment, Figures 2a-2i: chronological representations of the state of a working machine and the circuit diagram for the method embodiment according to the invention, Figure 3: a basic representation of the fluidic integration of the auxiliary compressor according to the invention into the air path of the internal combustion engine, Figure 4: a diagram for comparing the temporal torque curve for different engine types, Figure 5: a temporal power diagram to illustrate possible downspeeding when applying the invention, and Figure 6: diagram representation of instantaneous variables of the auxiliary compressor during the method embodiment.

[0042] Figure 1shows the diagram of an embodiment of the invention. As far as the components are concerned, the internal combustion engine 10 according to the invention has a hydraulic pressure accumulator 13, a first hydraulic displacement unit (hydraulic pump) 12 and a second hydraulic displacement unit (hydraulic motor) 14, a compressor 15, also referred to as an auxiliary compressor, corresponding hydraulic valves 16, 17, hydraulic lines, a control unit, and a hydraulic oil tank 18. In the event that the system according to the invention is used in an application in which corresponding hydraulic components are already naturally installed in an open hydraulic circuit, the hydraulic oil storage tank 18 already existing due to the existing mobile hydraulics can of course also be used for those hydraulic components required for the additional system according to the invention.

[0043] If the first hydraulic displacement unit 12 is used, it operates in pump mode. The hydraulic displacement unit 12 is preferably integrated into the overall system consisting of the combustion engine 10 and the output drives in such a way that, during certain operating conditions in which kinetic energy must be extracted from the overall system, the hydraulic displacement unit 12 can be supplied with appropriate power via its drive shaft in order to recuperate this energy. A fluid connection exists between the high-pressure connection of the hydraulic displacement unit 12 and the pressure accumulator 13 to supply hydraulic oil to the pressure accumulator 13. However, a backflow of hydraulic oil from the pressure accumulator 13 toward the hydraulic displacement unit 12 is prevented.

[0044] A fluid connection is established between the hydraulic displacement unit 14, which is preferably designed as a hydraulic motor for 1-quadrant operation and is particularly preferably configured as a high-speed hydraulic motor, and the pressure accumulator 13 via a 3 / 2-way valve 16. In a first switching position of the 3 / 2-way valve 16, hydraulic oil coming from the pressure accumulator 13 can be supplied to the hydraulic displacement unit 14, and in a second switching position, this fluid connection can be interrupted.

[0045] The auxiliary compressor 15 is integrated into the overall system in such a way that it can draw rotational power from the drive shaft of the hydraulic displacement unit 14 and thereby increase the combustion air supply to the internal combustion engine 10. The mechanical coupling between the hydraulic displacement unit 14 and the compressor 15 can be implemented via a transmission gear.

[0046] The hydraulic displacement unit 12 can be designed as a power take-off of the internal combustion engine 10 or, if present, can be mounted on the primary or secondary side of a pump distribution gearbox. In an advantageous embodiment, the invention is such that the hydraulic displacement unit 12 is integrated into the overall system in such a way as to place as little load as possible on the internal combustion engine 10 during operating situations in which no recuperation power is available. In a design according to the Figure 1In the diagram shown, for the operating case in which power is to be supplied to the pressure accumulator 13 using the hydraulic displacement unit 12, the 2 / 2-way valve 17 is closed and at the same time the 3 / 2-way valve 16 is set such that the hydraulic fluid delivered by the hydraulic displacement unit 12 can be supplied to the pressure accumulator 13. If no hydraulic fluid is to be supplied to the pressure accumulator 13 or no hydraulic fluid can be supplied, the 2 / 2-way valve 17 is opened, whereby the hydraulic fluid delivered by the hydraulic displacement unit 12 is directly returned to the hydraulic oil storage tank 18.

[0047] For certain applications, a further development of the invention may be advantageous in which, when the hydraulic displacement unit 12 is actuated, energy is preferably only supplied to the pressure accumulator 13 when recuperation power is available. However, when the pressure within the pressure accumulator 13 falls below a certain minimum pressure level, the hydraulic displacement unit 12 is actuated with increased operating speed of the internal combustion engine 10 and thus at the expense of increased fuel consumption in order to prevent the pressure within the pressure accumulator 13 from falling below a specified minimum pressure level. As a result, the ability to provide additional charge air with the energy stored in the pressure accumulator 13 can be maintained even when the available recuperation energy is not sufficiently high. A corresponding scenario could, for example,This may occur when the work machine is driving on the road and is moving in a prolonged stop-and-go mode due to the current traffic situation; particularly if these driving maneuvers extend along an uphill driveway.

[0048] In addition to or as an alternative to the 2 / 2-way valve 17, the hydraulic displacement unit 12 can be integrated into the overall system in such a way that the relevant frictional connection between the drive shaft of that hydraulic displacement unit 12 and its external drive can be selectively closed or interrupted, for example, using a magnetic coupling. In addition to or as an alternative to the above, a hydraulic displacement unit 12 whose delivery effect can be deactivated can be used.

[0049] The Figures 2a-2ieach show specific snapshots of a specific embodiment of the work machine according to the invention in an exemplary application. The application is the lever arm of an excavator 1. Figures 2a-2iOn the left-hand side, a schematic silhouette of the excavator 1 is shown, while on the right-hand side, the operating mode of the system according to the invention is shown, with the excavator silhouettes and the indicated operating situations of the system according to the invention corresponding with one another in time in each individual figure. The subsystem shown on the right-hand side is largely reduced and comprises the previously mentioned components: combustion engine 10, first displacement unit 12, pressure accumulator 13, second displacement unit 14, and auxiliary compressor 15. The system also contains the two 3 / 2-way valves 20, 21 for fluidically connecting the components for the different operating states or for disconnecting the fluid connections. The illustration also shows a hydraulic cylinder 19 of the excavator's secondary working circuit, which serves to hydraulically actuate the excavator's lever arm.Although the supported movement sequence of the excavator 1 can involve the components lift 2, arm 3 and bucket 4, the right-hand side illustrations of the . Figures 2a-2i to the respective representation of a single linear cylinder 19, namely the linear cylinder for actuating the stroke 2. It is known to those skilled in the art that the stroke is actuated via two lifting cylinders operating in parallel. Since this fact is irrelevant to the understanding of the presented embodiment of the invention, it will not be considered.

[0050] In the Figure 2a The stroke of the excavator silhouette shown on the left is in the area of ​​its upper end stop. Corresponding to this, the right-hand illustration of the Figure 2aThe piston rod of the hydraulic cylinder 19 is fully extended. The stem 3 of the excavator silhouette is angled. The dashed connecting line to the 3 / 2-way valve 21 indicates that, in the snapshot shown here, no hydraulic fluid can flow from the hydraulic displacement unit 12 through the 3 / 2-way valve 21. Other hydraulic displacement units that can be driven by the combustion engine 10 are not shown in this highly reduced schematic diagram; nor is the regular air path of the combustion engine 10, etc.

[0051] Within the schematic diagram on the right-hand side, there is another 3 / 2-way valve 20. A fluid connection exists between the linear cylinder 19 and the pressure accumulator 13 via the two 3 / 2-way valves 20, 21, which is indicated by solid lines. The fact that these are solid lines is intended to indicate that a combination of the switching positions of these two 3 / 2-way valves 20, 21 exists, due to which a fluid connection exists between the working chamber of the linear cylinder 19 and the storage volume of the pressure accumulator 13, which is used to hold hydraulic fluid. On each of these three solid lines, an arrow is drawn in a direction that is intended to show that hydraulic fluid can flow from the working chamber of the linear cylinder 19 towards the storage volume of the pressure accumulator 13.The hydraulic fluid column located within the working chamber of the linear cylinder 13 is subjected to high pressure via the piston rod due to the force of the bucket lever arm, while the fill level and thus the internal pressure within the pressure accumulator 13 is comparatively low. Unless there is a corresponding hydraulic and / or mechanical blockage, the piston rod of the linear cylinder 19 moves in such a way that hydraulic fluid flows out of the working chamber of the linear cylinder 19 in the direction of the arrow markings.

[0052] In the Figure 2a In the snapshot shown, the auxiliary compressor 15 and the second hydraulic displacement unit 14 serving to drive it, which is designed as a hydraulic motor according to the circuit diagram symbol used, remain in a passive state.

[0053] A movement starting from the Figure 2ashown condition of the excavator 1 in the Figure 2b as well as in the Figure 2c The illustrated state results in a comparatively low hydraulic power being required for the slight lifting of the handle 3, while a comparatively high output power is required for the lowering of the stroke 2, which is used according to the invention to supply compression energy to the storage volume of the pressure accumulator 13. Accordingly, the consumer system of the bucket arm has a low power requirement for the combustion engine 10, and hydraulic energy can be recuperated in the pressure accumulator 13. A snapshot of the movement of the bucket arm as well as the changes in the fill levels of the pressure accumulator 13 and the linear cylinder 19 is shown in Figure 2b shown on the right. A snapshot taken at a later time, just before the bucket 4 is inserted to pick up the bulk material 22, is shown in Figure 2cIn this way, part of the dissipated stroke energy can be converted into compression energy by forcing hydraulic oil into the pressure accumulator 13, which may be designed, for example, as a bladder accumulator, diaphragm accumulator, or double-piston accumulator.

[0054] In the Figures 2d , 2e Two chronologically successive snapshots are shown, which depict the penetration of the bucket 4 into the bulk material 22. Within the intervening period, a slight further reduction of the stroke may occur, which is of secondary importance in relation to the respective power conversion within the linear cylinders, which determine the position changes of the three components in focus, lift 2, stick 3 and bucket 4, during that operating phase. Therefore, in the illustrated linear cylinder 19, via which the movement of the stroke is determined, when comparing the Figures 2d , 2eno change in fill level can be detected by simple visual inspection.

[0055] For the linear cylinder that now achieves the required movement of handle 3, a much higher hydraulic power requirement exists during that time interval. This linear cylinder is not depicted in the aforementioned schematic diagrams, which illustrate the considered movement sequence of the bucket arm, although the linear movement, which is used to position the relevant piston rod in its axial direction, is self-explanatory in the overall context.

[0056] With regard to the subsection of the work sequence in focus here, in which the bucket 4 is inserted into the bulk material 22, based on a temporally detached consideration, the beginning of a quasi-sudden increase in the power requirement that the combustion engine 10 must meet is evident. With regard to the respective points in time, increases in demand are far less predictable. An operation according to the invention for the efficient execution of the described work process now provides that, by opening the corresponding fluid connection by means of the valve 20, hydraulic power is supplied from the pressure accumulator 13 to the hydraulic motor 14. This puts the auxiliary compressor 15 into its intended operating mode and maintains this mode for a certain period of time.A comparatively short period of time passes before the auxiliary compressor 15, upon activation of a corresponding requirement, generates the required additional charge air and supplies it to the air path of the combustion engine. Such a requirement arises when there is an extremely high increase in the target output of the combustion engine, both in absolute terms and in relation to the required increase rate, and this requirement can be met by the fuel supply system due to its nature and suitable operability, or at least to such an extent that a sufficiently high air supply quantity cannot be provided within the currently existing state of the regular air path using the latter alone. A more detailed focus on the supply support of charge air achieved through the use of the auxiliary compressor 15 will be provided in a separate section.

[0057] Depending on the design of the respective subsystem, the available recuperation energy, the required air support by the auxiliary compressor 15, and especially the prevailing bulk material conditions at the time, it may be possible that in a first scenario, the ability to supply additional charge air to the combustion engine 10 is already exhausted or would be exhausted before the bucket 4 has completed its penetration into the bulk material 22 (e.g., due to an empty pressure accumulator). In another scenario, however, support by additional charge air may still be possible when the lifting of the bulk material in the bucket 4 has already begun or is even completed.An application according to the first scenario does not represent a disadvantage, provided that the charge air support that can be provided by means of the auxiliary compressor 15 can be provided to such an extent in terms of time and quantity that the internal combustion engine 10 can be operated without the action of the auxiliary compressor and there is no restriction of its current power output capability as a result, ie for example the potential occurrence of the phenomenon referred to as turbo lag has already been overcome.

[0058] In the Figures 2f , 2g , 2h and 2iThree sequential snapshots are shown, which demonstrate the lifting of the bucket 4 filled with bulk material 22. In these operating states, the directional control valve 20 is closed and interrupts any fluid flow to and from the pressure accumulator 13. Instead, the linear cylinder 19 can be filled with hydraulic oil, which is pumped from the hydraulic displacement unit 12 to the linear cylinder 19 through the directional control valve 21.

[0059] Figure 3 shows a schematic diagram of how the additional compressor 15 can be connected as a supplement to the regular charge air path of the combustion engine 10. For the sake of simplicity, the figure does not show how liquid hydraulic fluid can be supplied to the pressure accumulator 13, since this has already been explained above with reference to the Figures 2a to 2i and the text referring to it. In the execution according to Figure 3the internal combustion engine is a hydrogen engine 10, which is why a throttle valve 23 is present along the regular air path 24. However, the following explanations are not limited to a design as a hydrogen engine. Advantageously, the throttle valve 24 is arranged such that its potential throttling effect on the air path extending via the auxiliary compressor 15 is completely absent. The regular air path 24 extends via a compressor stage in the form of an exhaust gas turbocharger 25, which is arranged downstream of the supply line section at which both partial air flows, i.e. the air flow extending permanently via the throttle valve 23 and the air flow optionally generated by the auxiliary compressor 15, are combined. Concerning the combustion engine 10, four cylinders 29, the air distributor 26, the exhaust manifold 27, an intercooler 28 and the exhaust gas turbocharger 25 are indicated as examples.

[0060] In order to provide the combustion chambers with a significantly increased mass flow of charge air after only a short response time when a corresponding need arises, the auxiliary compressor 15 shown is driven by the hydraulic displacement unit 14, which is preferably designed as a high-speed hydraulic motor. The auxiliary compressor 15 is preferably a volumetric compressor, in particular a gerotor compressor or an internal gear compressor. To achieve a sufficiently high compressor speed, which has a value of 15,000 revolutions per minute and preferably 20,000 revolutions per minute, the rotational transmission between the hydraulic motor 14 and the compressor 15 is achieved via a transmission gear 30.In order for the hydraulic motor 14 to provide mechanical power to the compressor 30 at a predefined, preset level, the compressor 30 draws hydraulic power, which can be provided by the pressure accumulator 13 and extends via a fluid connection running through a controllable valve 31. Advantageously, the adjustment of this valve 31 is carried out via a control loop, with the required valve position preferably being determined by a control unit.

[0061] The following are design examples for the components for use in a hydrogen engine with intake manifold injection: Hydrogen engine 10: ∘ Displacement approx. 10 liters / power of 200 kW / application in a 30 t excavator for earthmoving ∘ Displacement approx. 15 liters / power of 450 kW / application in an 80 t excavator for earthmoving Pressure accumulator 13, designed as a bladder accumulator: The capacity for the liquid fluid is 2 liters to 6 liters, the presence of which in the accumulator compresses the required gas pressure level to a maximum pressure of 240 bar. Compressor 15 to provide the additional charge air: ∘ Delivery rate 900 kg / h to 2000 kg / h ∘ Technology: ▪ A volumetric compressor is preferred, in particular a gerotor compressor or an internal gear compressor (speed range up to 20,000 rpm, at least 15,000 rpm). Alternatively, the use of an external gear compressor would be possible, although this may involve certain disadvantages. ▪ A dynamic compressor (screw compressor) is less suitable but still possible, as the extremely high speeds (50,000 rpm to 100,000 rpm) mean that the required power is not sufficient.000 rpm) a gearbox with a high gear ratio to the high-speed hydraulic motor 14 is required. Design example for a diesel engine:

[0062] Diesel engine with intake manifold injection, a displacement of 9 liters and an output of 200 kW; 13.5 l at 450 kW pressure accumulator and application as mentioned above

[0063] Possible advantageous modifications of the aforementioned work machine or the method according to the invention are described below. Extension form

[0064] The system features a control function that sets a dynamic threshold for a speed reduction for the internal combustion engine 10. If the compression energy already present within the pressure accumulator 13 is sufficiently high, the engine speed setpoint is set to a minimum limit when a low power demand is encountered. If the currently available compression energy within the pressure accumulator 13 is lower, the lower engine speed setpoint is set to a threshold that is higher than the aforementioned minimum limit, corresponding to the shortfall in compression energy within the pressure accumulator 13. Systematics

[0065] The hydraulic displacement unit 12, via which recuperation can take place, is used ∘ (i) both for working operation or primarily for working operation and can also be used for recuperation: ▪ Example 1: Linear cylinder 19, which carries out work to lift a load and which can deliver hydraulic power when lowering that load; ▪ Example 2: Hydraulic displacement unit which carries out the slewing movement of the upper carriage of an excavator ∘ (ii) only for recuperation: ▪ Hydraulic pump which can obtain torque from a power take-off of the combustion engine, from an output of a pump distribution gearbox or from a passive drive axle, ie an axle which is not supplied with drive energy from the drive system in order to be able to generate its own torque.The hydraulic displacement unit, through which recuperation can take place, is an energy converter (i) between rotational power and hydraulic power or (ii) between lifting power and hydraulic power.

[0066] The advantages achieved by the invention can be summarized as follows: Starting with a low charge air supply rate, a significant increase in the charge air supply rate can be achieved within a short period of time. See, for example, Figure 4, which shows in a diagram the possible output torque versus time for a hydrogen engine and a diesel engine with «downspeeding». In particular, the diagram shows the curve for a conventional hydrogen engine, ie a hydrogen engine according to the state of the art (dashed line) and for a hydrogen engine with the auxiliary compressor 15 according to the invention (dotted line). In this comparison, the achievable increase in dynamics is evident, since the desired higher output torque is achieved significantly faster with the embodiment according to the invention. In addition, the diagram shows the Figure 4The solid line shows the torque curve for a diesel engine operated with "downspeeding," i.e., a reduction in the speed spectrum. Thanks to the use of the invention, sufficient dynamic capability of the diesel engine can be ensured here too, despite "downspeeding." Application to a dynamically operated gas engine that is to be operated with a consistently high excess air -> the design according to the invention enables a significant increase in dynamic capability with comparatively little effort. Application to a dynamically operating internal combustion engine operated with a liquid fuel -> the increase in dynamic potential can be used entirely or partially for downspeeding.Overall, there is scope for optimization, as the increase in dynamic capability allows the combustion engine to be operated at lower speeds in the operating range of low to medium power outputs. A comparison of the engine performance of a diesel engine without speed reduction (1800 rpm), a diesel engine with speed reduction to 400 rpm but without an auxiliary compressor, and a diesel engine with speed reduction to 1400 rpm and the auxiliary compressor according to the invention is shown in the following. Figure 5It can be seen here that a diesel engine according to the invention, despite a reduction in speed from 1800 rpm to 1400 rpm, comes close to the engine power of the diesel engine without a reduction in speed. The system solution is robust / durable in terms of downtimes and operational loads. The system solution is comparatively cost-effective in terms of acquisition and maintenance costs. With regard to the application spectrum of mobile work machines, the system solution can be limited to the use of components that belong to technology areas that are already in standard use. Modularity (particularly useful because the use of a system according to the invention is very advantageous for a specific application [e.g.[for an excavator used for excavation work], whereas on the same basic machine, which is used for a different purpose, the presence of a system according to the invention cannot achieve a significant increase in efficiency [e.g., for an excavator used for house demolition work]. [For certain applications, it can be used dedicatedly on a single drive, on several drive units, or for a group of several or all drive units [application example]. Excavator. Example 1 of the earthing system for the lifting device; example 2 for the slewing gear]. Retrofit capability

[0067] Unlike a hybrid drive system known from the prior art, in a corresponding operating situation, the temporary power deficit of the combustion engine is not reduced by the use of an additional drive. Instead, the invention enables the combustion engine to be ready to deliver correspondingly higher power in a shortened and thus acceptable time. As a result, although the full potential of recuperable energy available in principle is often not utilized, the additional equipment is comparatively cost-effective, compact, and therefore more suitable as an optional add-on. It is also more suitable for retrofitting an existing vehicle.

[0068] If an internal combustion engine is operated in a highly dynamic manner and is to always operate while maintaining a high combustion air ratio lambda, i.e. even if there is a (time-related) short-term and (in relation to the total amount) high increase in engine output, the internal combustion engine in question must be designed in such a way that a correspondingly time- and quantity-related strong increase in the air supply quantity can be provided to each of the combustion chambers when required.

[0069] The diagrams of the Figure 6 show the respective time course of four instantaneous variables that occur during the activity phase of the compressor 15. The first section I of the hump-shaped rotor speed time course ( Figure 6a ) and the associated time course of the air mass flow leaving the volumetric compressor ( Figure 6b) shows the acceleration phase I. Due to the correspondingly high air demand, the rotor pair exhibits a significant inertia corresponding to its required size. In addition, a high speed must be achieved. Therefore, a certain period of time (here approximately 0.5 s) elapses until the volumetric compressor 15 can provide an air mass flow corresponding to the initial setpoint.

[0070] Due to the increase in air support caused by the volumetric compressor 15 and the accompanying increase in the fuel supply rate, there is a particularly strong increase in the exhaust gas energy escaping from the combustion engine, resulting in a very high increase in the charge air compression caused solely by the exhaust gas turbocharger 25. For this reason, the respective support of the volumetric compressor 15 can be reduced quite significantly and briefly after reaching its maximum support. This is achieved by a corresponding control that causes a correspondingly adjusted throttling of the hydraulic fluid flowing out of the pressure accumulator 13. This leads to a reduction in the charge air compression caused by the volumetric compressor 15 via the hydraulic motor 14. This reduction is shown in the two diagrams. Figure 6a, 6band concerns the middle time interval II of the three marked sections. Due to the high mass moment of inertia of the two rotors of the volumetric compressor 15, air compression decreases but initially continues, which is in principle usable. In terms of time, this availability only exists over a short time interval. However, if one considers the power curve shown in the diagram in Figure 6c, one can see that this energy content is by no means negligibly small in relation to the total energy content introduced into the volumetric compressor 15.This, in turn, opens up a particularly interesting perspective for those devices that, while possessing a certain energy recuperation potential, are too low to utilize it to generate charge air support that, in turn, has sufficient power to bridge the so-called turbo lag according to the invention. Indeed, by appropriately expanding the system according to the invention, it could be ensured that a portion of this rotational energy is converted accordingly, whereby a certain portion of the energy is returned to the pressure accumulator 13, thereby creating an overall energy reserve that enables a sustainable supply to the volumetric compressor 15.

Claims

1. A working machine comprising an internal combustion engine (10) and at least one secondary pneumatic or hydraulic working circuit, wherein during operation of the secondary working circuit energy is recuperated and can be fed to a pressure accumulator (13) of the working machine for energy storage, characterized in that at least one auxiliary compressor (15) is provided which can be driven by the energy stored in the pressure accumulator (13), and an engine control is provided and configured to detect a highly dynamic increase in the power requirement of the internal combustion engine (10) and, if necessary, to generate additional charge air by means of the auxiliary compressor (15), which is supplied to the charge air path (24) of the internal combustion engine (10) in addition to the regular charge air flow of the internal combustion engine (10).

2. Working machine according to claim 1, characterized in thata first hydraulic displacement unit (12, 19) is provided to supply a liquid fluid, preferably an oil, in particular hydraulic oil, to the pressure accumulator (13).

3. Working machine according to claim 2, characterized in that the first hydraulic displacement unit (12) is driven via a secondary drive of the internal combustion engine (10) or via a pump distribution gear driven by the internal combustion engine and / or via an additional drive, for example an electric drive.

4. Working machine according to claim 2 or 3, characterized in that the first displacement unit (12) is a displacement unit which operates rotaryly in pump operation and is preferably designed as an axial piston or radial or in-line piston pump.

5. Working machine according to one of the preceding claims, characterized in thata second hydraulic displacement unit (14) is provided which can be driven by means of the compression energy stored in the pressure accumulator (13) and whose mechanical output power serves to drive the auxiliary compressor (15).

6. Working machine according to claim 5, characterized in that the second displacement unit (14) is a hydraulic motor, preferably a high-speed hydraulic motor, particularly preferably an axial piston machine suitable for the high-speed range and / or a gear pump / motor.

7. Working machine according to one of claims 5 or 6, characterized in that the second hydraulic displacement unit (14) can be operated in pump mode, whereby energy can be recuperated into the pressure accumulator (13) from the rotational energy of the auxiliary compressor (15).

8. Working machine according to one of claims 5 to 7, characterized in that a transmission gear (30) is connected between the auxiliary compressor (15) and the second displacement unit (14).

9. Working machine according to one of the preceding claims, characterized in that the auxiliary compressor (15) is a volumetric compressor, preferably an internal gear compressor or gerotor compressor.

10. Working machine according to one of the preceding claims, characterized in that the pressure accumulator (13) is a bladder accumulator, diaphragm accumulator or a double piston accumulator.

11. Working machine according to one of the preceding claims, characterized in that the additional charge air generated by the auxiliary compressor (15) can be fed to the air path of the internal combustion engine (10) via at least one charge air cooler, preferably to the air path of the internal combustion engine (10) upstream of a charge air cooler (28) of the internal combustion engine (10).

12. Working machine according to one of the preceding claims, characterized in thatthe additional charge air of the auxiliary compressor (15) can be fed to the charge air path (24) of the internal combustion engine (10) upstream of a compressor of the internal combustion engine (10), wherein the compressor is preferably the compressor wheel of an exhaust gas turbocharger (25).

13. Working machine according to one of the preceding claims, characterized in that the regular charge air path (24) of the internal combustion engine (10) comprises a throttle valve (23) and the additional charge air from the auxiliary compressor (15) can be fed to the charge air path downstream of the throttle valve (23).

14. Working machine according to one of the preceding claims, characterized in thatthe pressure accumulator (13) is integrated into the secondary working circuit via a switchable valve arrangement (16, 17, 20, 21, 31), in particular at least one directional control valve, wherein liquid fluid for energy storage can be supplied to the pressure accumulator (13) in a first valve position, liquid fluid for driving the auxiliary compressor (15) can be removed in a second valve position and in a third valve position neither liquid fluid can be removed from the pressure accumulator (13) nor liquid fluid can be supplied to the pressure accumulator (13).

15. Working machines according to one of the preceding claims, characterized in that the first displacement unit (12) can be mechanically decoupled from its drive shaft, preferably via a magnetic coupling, and the coupling can preferably assume the following states: (i) momentary opening, (ii) keeping open, (iii) momentary closing and (iv) keeping closed.

16. A method for operating a working machine, in particular a working machine according to one of the preceding claims, with an internal combustion engine (10) and at least one secondary working circuit, wherein during the operation of the secondary working circuit energy is recuperated and stored in a pressure accumulator (13) of the working machine, characterized in that upon detection of a highly dynamic increase in the power requirement of the internal combustion engine (10), an auxiliary compressor (15) is driven by the extraction of such energy stored in the pressure accumulator (13) in order to supply additional charge air to the internal combustion engine (10).

17. Method according to claim 16, characterized in that Rotational energy of the auxiliary compressor (15), which exists after the end of the compressor operation for generating the additional charge air, is recuperated in the pressure accumulator (13) by a second displacement unit (14) operating as a pump to drive the auxiliary compressor (15).

18. Method according to one of claims 16 or 17, characterized in that the first hydraulic displacement unit (12) has an idle power consumption of less than 10%, preferably less than 5% and particularly preferably less than 2%, relative to its power consumption during full load operation.

19. Method according to one of the preceding claims 16 to 18, characterized in that the internal combustion engine (10) is operated with a fuel which contains molecular hydrogen, preferably contains at least 50% molecular hydrogen, or the fuel is pure hydrogen.

20. Method according to one of the preceding claims 16 to 19, characterized in that the combustion air ratio lambda of the internal combustion engine (10) does not fall below a defined limit value, wherein the limit value corresponds to a value of at least 1.5, preferably of at least 2.0 and particularly preferably of at least 2.

5.

21. Method according to one of the preceding claims 16 to 20, characterized in that during partial load operation of the internal combustion engine (10), the engine speed is reduced, which is determined dynamically as a function of the compression energy available in the pressure accumulator.

22. Method according to one of the preceding claims, characterized in that the pressure accumulator (13) is supplied with recuperation energy from a movement function of an actuator of the secondary working circuit, for example from a hydraulic cylinder (19) which actuates a single segment of a lever arm, and / or from a rotating movement function of a single actuator of the secondary working circuit, for example from an axial piston machine (12) which causes the acceleration and braking of the rotary movement of an upper carriage of the working machine, and / or from a drive system of the working machine which serves for the translational movement of the working machine.

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