CN110520617B

CN110520617B - Fuel injection with reduced amount of backflow

Info

Publication number: CN110520617B
Application number: CN201880024314.1A
Authority: CN
Inventors: A·西门子
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-04-10
Filing date: 2018-03-13
Publication date: 2022-06-07
Anticipated expiration: 2038-03-13
Also published as: CN110520617A; DE102017206084A1; WO2018188869A1

Abstract

The invention relates to a method (100) for operating an injection system (1) of an internal combustion engine (2), wherein the injection system (1) comprises a high-pressure accumulator (11) for one or more fuels (3) and a setpoint pressure p in the high-pressure accumulator (11)_SAccording to at least one characteristic map (16), a load demand L of the internal combustion engine (2) is followed, wherein excess fuel (3,31) from the high-pressure accumulator (11) is depressurized (99) in order to reduce the actual pressure p in the high-pressure accumulator (11), wherein a setpoint pressure p in the high-pressure accumulator (11) is reduced at least temporarily when the load demand L falls to an operating point (29) with a lower load_SRelative to a value p set for the operating point (29) according to the characteristic map (16)_KIs increased (110,110a-110 c). The invention also relates to a corresponding computer program product.

Description

Fuel injection with reduced amount of backflow

Technical Field

The invention relates to a method for operating a fuel injection system, in which method fuel is held in a high-pressure accumulator at a variable pressure.

Background

In high-pressure common rail systems for internal combustion engines, fuel, for example diesel fuel or Liquefied Natural Gas (LNG), is compressed to a high pressure level by means of a high-pressure pump and is held in a high-pressure accumulator (rail). The high-pressure accumulator generally supplies a plurality of injectors which inject fuel into the combustion chambers of the individual cylinders of the internal combustion engine. Such an injection system is known, for example, from US 6,024,064 a.

The required injection quantity q per injection cycle depends on the load demand L of the internal combustion engine. If the load demand L drops, less fuel is required. When the load demand L drops strongly, the fuel quantity cannot be reduced by merely shortening the injection time, but the pressure p in the high-pressure accumulator must additionally be reduced. Independently of this, the combustion behavior for the same fuel quantity is also related to the pressure p, by means of which the fuel is supplied to the injector.

When there is a need to reduce the pressure p in the high-pressure reservoir, excess fuel is led back from the high-pressure reservoir into the storage container (tank). In this led back fuel, the energy that has been used to compress the fuel to a high pressure level is stored in the form of heat. Furthermore, the temperature of the compressed fuel is determined jointly by heat exchange with the immediate surroundings of the fuel (e.g. rail body, pipe, engine compartment).

Although this heat can be used, for example, according to EP 1319821 Bl in order to preheat diesel fuel and prevent clogging of the fuel filter in the event of low external temperatures, heating of the fuel supply has an adverse effect in most operating situations. Thus, US 6,647,968 Bl discloses that the consumption efficiency is related to the fuel temperature and proposes to reduce the temperature of the returned fuel by increasing the flow rate. Furthermore, the energy which is usually used first for compressing the fuel and which is converted into heat when being returned cannot be used for driving the vehicle, i.e. is actually lost.

Disclosure of Invention

Within the scope of the present invention, a method for operating an injection system of an internal combustion engine has been created. The injection system comprises a high-pressure accumulator for one or more fuels. Rated pressure p in a high-pressure accumulator_SThe load demand L of the internal combustion engine is followed according to at least one characteristic map. In order to reduce the actual pressure p in the high-pressure accumulator, the excess fuel from the high-pressure accumulator is depressurized.

The fuel can be returned to the storage tank, for example, wherein an intermediate tank can optionally also be provided between the high-pressure accumulator and the storage tank as a buffer for tempering the fuel before the return feed or also as a test point for additional consumers. However, at least a partial quantity of the fuel can also be depressurized, for example, to an intermediate pressure level between the prefeed pump and the high-pressure pump which supplies the high-pressure accumulator. At least a portion of the energy that has been used to compress the fuel is then further utilized. The characteristic map may, for example, specify the injection quantity q required per injection cycle for each load demand L. Depending on the boundary conditions for the injection period, the required setpoint pressure p can be determined or at least defined _S. The minimum injection time is defined by the minimum pulse time, with which the injector can be actuated. The maximum injection period is defined according to the engine speed by: the injection must take place in a partial region of the crankshaft rotation determined by the angle.

The same characteristic map, or another characteristic map, may also be used to establish the required target pressure p_SCoupled to the load demand L directly or also in combination with further variables.

The characteristic map can be optimized in particular with regard to the least possible fuel consumption or also with regard to the least possible pollutant or noise emissions. In the case of a plurality of internal combustion engines, the use of such characteristic maps is essential for achieving the standard specifications for consumption and environmental characteristics.

According to the invention, the setpoint pressure p in the high-pressure accumulator is reduced at least temporarily when the load demand L falls to an operating point with a lower load_SRelative to the value p set for this operating point according to the characteristic diagram_KIs improved.

In the case of a temporary drop in the load demand L, a drop is understood in particular to mean that this drop is compensated for at a large probability immediately, completely or partially, by an increase in the load demand L.

Rated pressure p_SHas the following effects: significantly reduced or even completely reduced when the load demand L drops brieflyThe fuel cut is returned from the high-pressure accumulator to the storage container. Thereby significantly reducing the heat input in the storage container. This results in significant energy savings in two respects, on the one hand, the energy that has been put into the fuel compression is less lost in the form of heat that cannot be further utilized. On the other hand, less energy is consumed for removing this undesirable heat from the fuel accumulator by means of the fuel cooling device.

The reduced heat input into the storage vessel has other significant advantages, particularly when using Liquefied Natural Gas (LNG) as fuel. Natural gas is liquid only when the temperature is much lower than the ambient temperature. Thus, heat input into the storage vessel can result in evaporation and boiling point excursions. As a result, an overpressure in the storage container can occur and, as a result, a safety-dependent release of gas into the surroundings occurs. This can create an explosive atmosphere in enclosed spaces such as parking buildings. Further, the main component of the unburned natural gas is specific CO₂Methane, which is significantly more responsible for the greenhouse effect. For this reason, it is provided that the storage container for LNG is at least so well insulated that a predefined holding time between two drives can be achieved without gas emissions. The reduction of the additional heat input by the return of fuel results in that the regulation can be implemented with a low degree of insulation of the LNG storage container and/or that a longer holding time can be implemented between two drives.

Thus, the cost to obtain the illustrated advantages is: by rated pressure p_SRelative to the value p which is originally set for the operating point with the lower load according to the characteristic diagram_KThe improvement deviates from the optimum value determined in the characteristic map in terms of injection. This may result in: the injection accuracy deteriorates in this operating point, so that the fuel consumption efficiency and the harmful emissions and the noise emissions may instantaneously deteriorate.

However, it is known that this temporary deterioration is insignificant when considering the entire operation of the internal combustion engine. Thus, the cost paid for the advantage is less than it would appear at first sight.

For example, a brief (transient) operating phase with a sharply decreasing load demand L therefore constitutes only a very small proportion of the operating time of the internal combustion engine. Thus, the temporary increase in consumption and emissions is eventually overcompensated by the energy and fuel savings due to the reduced lead back.

If a brief increase in the load demand L immediately after a drop is to be expected, the idle-noise level, which is increased as a result of the deviation from the characteristic map, is not important, in particular for this short time interval. Furthermore, the rate of decrease of the actual pressure p in the high-pressure accumulator is technically limited throughout so that at the load demand L and thus the nominal pressure p _SBefore being raised again, the actual pressure p may not drop at all to the sharply reduced nominal pressure p_SThe above. Possibly, the consumption and emission characteristics of the internal combustion engine are even completely unimportant in operating points with lower loads, since the vehicle is coasting at this operating point and no fuel is injected due to coasting shut-down.

For these reasons, it is known that, if the load demand L drops only temporarily, it is not significant that the setpoint pressure Ps follows this drop completely according to the characteristic map and, in accordance therewith, the actual pressure p in the high-pressure accumulator drops sharply.

An example of a temporary drop in the load demand L is a shifting process in which the vehicle is running. Each such shifting process requires an interruption of the force transmission from the combustion engine for about 0.5-1 second. In particular during an upshift during the acceleration process, the phase with the higher load demand L will immediately follow this brief phase with the reduced load demand L. The method comprises the following steps: suppression of setpoint pressure p during a shifting operation_SThus not only saving energy but also slightly improving acceleration characteristics.

The advantageous effects of the invention according to the preceding statements are not limited to the following: the setpoint pressure p is only applied when a temporary drop in the load demand L is detected or is about to occur _SRelative to a predetermined value p from a family of characteristic curves_KAnd (4) improving. The described advantages can also be achieved permanently, independently of the actually prevailing temporary drop in the load demand L, or in general in dependence on the measures taken at the operating point. Is only andonly on the balance of the advantages achieved by reducing the return of fuel with respect to greater consumption and greater emissions due to deviations from the characteristic map over the average time of vehicle operation, i.e. for example the cumulative exhaust gas value.

Furthermore, the advantageous effects of the invention are in principle not limited to the following: which fuel is used for the operation of the internal combustion engine. In principle, independent of the location in the fuel supply system at which the fuel from the high-pressure accumulator is depressurized and which fuel is involved, additional heat is input into the fuel supply system as a whole. This is known from the law of conservation of energy. The fuel type only has an effect on how much this heat input is and how much can be tolerated in the operation of the vehicle. The invention can therefore also be used in single internal combustion engines, for example running on diesel fuel or on Liquefied Natural Gas (LNG), as in dual-unit (bi-fuel) internal combustion engines which can be selectively run on one of the fuels. Particular advantages are ensured in the case of a two-component internal combustion engine and are used here exclusively when changing from single operation with diesel fuel to two-component operation with diesel fuel or LNG. Here, the advantages of operating with LNG only come at the cost of: LNG is particularly sensitive to heating due to the introduced fuel. This cost is significantly reduced by the present invention.

In a particularly advantageous embodiment of the invention, the setpoint pressure p_SIs maintained at least at a predetermined base level p_BAbove, the base level is higher than a value p set for idling of the internal combustion engine according to the characteristic map_K. As long as the load demand L is so high that the corresponding setpoint pressure p is dependent on the characteristic map_KGreater than p_BThen the measure has virtually no effect. Only if the load demand L is reduced to such an extent that p_KDown to p_BOnly when this is the case will the actual deviation from the characteristic diagram occur. Thus, at a suitably chosen base level p_BEven if no further monitoring is carried out at all, a significant improvement can be achieved overall if there is or is about to occur a temporary drop in the load demand L.

In another aspect of the present inventionIn a particularly advantageous embodiment, the nominal pressure p_SAt a maximum and/or minimum time rate of change dp_SThe maximum and/or minimum temporal rate of change dp/dt of the actual pressure p and/or the load demand L is more strongly limited when the load demand L decreases than when the load demand L increases. This is also understood in particular to mean the case: the time change rate is limited when the load demand L falls, but such a limitation is not set when the load demand L rises.

For example, the inflow regulator for increasing the pressure p in the high-pressure accumulator and/or the return regulator for reducing the pressure p are designed in such a way that the regulator is predefined with a time rate of change dp/dt of the pressure p as a control variable. The regulator opens the valves internally in each case so precisely that a predefined time rate dp/dt occurs. The temporal rate of change dp/dt can thus be limited by: limiting the manipulated variable delivered to the actuator in relation to the time rate of change.

As long as the reduction of the load demand L continues, the setpoint pressure p_SFinally falls to the value p_KThis value is predefined by the characteristic map for operating points with lower loads. However, this takes place with a time delay such that, when the load demand L drops only temporarily (transitionally), the setpoint pressure p is significantly reduced or even interrupted_SIs reduced. Conversely, when the load demand L rises, the speed limit is less favorable, the nominal pressure p_SAs the speed increases. Such a limitation would make the engine less dynamically responsive.

When the operating point of the internal combustion engine, in particular the load demand L, changes over time, the setpoint value p of the pressure in the high-pressure accumulator, which is optimized according to the characteristic map, changes _KAlso over time. From a time-dependent target value p according to a characteristic diagram_KThe departure (t) can be formed, for example, by temporal attenuation, smoothing, filtering and/or asymptotic weighting to form the final setpoint pressure p_S. The rated pressure p_SOr from a family of alternative value-characteristic curves. For example, p may be_K(t) the falling edge of the curve reaches the nominal pressure p with a delay by means of a delay element_S。

In a further particularly advantageous embodiment of the invention, the decoupling of the internal combustion engine is evaluated as a temporary reduction in the load demand L. The decoupling is a temporary state that is essentially independent of whether it is effected by actuating the clutch pedal or automatically.

In a further particularly advantageous embodiment of the invention, the request for a shifting process by the automatic transmission is evaluated as a temporary reduction in the load request L. The term "automatic transmission" includes any transmission in which the shifting process is automated to such an extent that a clutch pedal in the vehicle is superfluous, i.e. both fully automatic transmissions and automated manual transmissions are included. In contrast to the engine controller, the transmission controller can in particular inform beforehand that a gear change process is imminent. The engine controller then has previously learned: the following brief interruption of the force transmission with the drop in the load demand L will be temporary. Accordingly, the nominal pressure p _SIs reduced or interrupted, i.e. the nominal pressure p_SCan be increased to a value p predetermined by a characteristic map_KThe above.

In a further particularly advantageous embodiment of the invention, the drop in the load demand L is evaluated as temporary when the rate of change of the magnitude dL/dt of the drop in the load demand exceeds a predefined threshold value Δ L. Typically, neither the road conditions nor the driver's desire f to involve a sudden change in speed. In contrast, the interruption of the force transmission during decoupling is switched as abruptly as possible, so that the clutch is in a state of friction and therefore high wear only for as little time as possible.

In a further particularly advantageous embodiment of the invention, the drop in the load demand L is first evaluated as temporary. When the load demand L is below a threshold Ls for a predetermined time interval, the setpoint injection quantity q is below a predetermined threshold q_SThe drop is only evaluated as non-temporary when the driver wishes f to correspond to an operating point with a lower load. The idea behind is that in a typical driving situation, the temporary drop in the load demand L is more than the driver wishesThe change in f occurs significantly more frequently. That is, when a drop in the load demand L occurs, it is highly probable that the drop is temporary. In individual cases it is shown that: the drop may be sustained. As explained above, but in particular with regard to the emission behavior, it depends on the time-dependent behavior of the internal combustion engine. On this sum, the advantage achieved by the reduced return of the warmed-up fuel overcomes the disadvantage of a few phases with low load, in which the injection accuracy is not optimal. This applies in particular to the context that at low loads, significantly less fuel is consumed per unit time or per path than at higher loads, so that at least in part relatively more emissions are generated at low loads.

In general, for the purpose of detecting a temporary drop in the load demand L, for example, the driver's desire f (corresponding to the accelerator pedal position), the load demand L after a transmission intervention by the vehicle and/or an evaluation and logical correlation of statistical data from a direct operating point history can be considered.

Furthermore, characteristic variables of the current operating point, for example the rotational speed of the internal combustion engine and the vehicle speed v, may also be taken into account.

The nominal pressure p can advantageously be set_SRelative to a value p set according to a characteristic map_KThe degree of change is related to the effect of how the introduction of warmed fuel back will currently cause disturbances to the fuel system. For this purpose, the degree can be linked, for example, to the state variable x of the storage container₁(e.g. filling level, pressure and/or temperature), and a state variable x of the fuel supply system part influenced by the fuel depressurization or by a drop in the actual pressure p₂With the state variable x of the fuel to be depressurized₃(e.g. gas temperature and/or energy) and/or ambient conditions x₄(e.g., ambient temperature).

The degree may be expressed, for example, in the pressure excursion, in the maximum pressure drop rate, and/or in the filter time constant. This or another variable can be coupled, for example, in a computational manner to the initial setpoint pressure p _SUp to the load demand L, to the required injection quantity q, to the gas pedal, transmission or clutchOn the information of the device, on the vehicle speed v, or also on the rate of change and/or derivative of these signals, said variables being the pressure values p suggested for the characteristic map_KA quantitative measure of deviation. Rate of change limitation, i.e. for rated pressure p_SThe limitation of the maximum and/or minimum rate of change dp/dt of the actual pressure p, and/or the limitation of the maximum rate of change of the control value or control signal associated therewith may be stored in the control unit, for example, as a characteristic map associated with the setpoint injection quantity q. This correlation makes it possible to set the modified setpoint pressure p, on the one hand, by maintaining it longer_SA compromise between minimizing the quantity of fuel introduced back and on the other hand approaching normal operation by a faster pressure drop. Temporal control of the measures, for example with respect to a temporally stepped filter time constant, can also be of interest.

For example, the intervention to the nominal pressure p can be started and stopped continuously (without a step)_SOr in a time profile to the nominal pressure. For this purpose, the intervention can be calculated (Fade-In/Out), Crossfade (Crossfade), stepped filter constants, asymptotic/hyperbolic functions) by means of a ramp (Rampen) which is controlled over time or is dependent on the operating point, for example.

The method may be performed, in particular, on an engine controller. For this purpose, it is necessary to advantageously neither change the control unit itself nor the associated sensor or actuator of the internal combustion engine. The method can be embodied in particular in a pure software update for the engine controller, which in this respect is also a product that is separately marketable for the retrofit market. The invention therefore also relates to a computer program product having machine-readable instructions which, when executed by a computer and/or controller, cause the computer and/or controller to carry out the method according to the invention.

Drawings

Further measures which improve the invention are explained in detail below together with the description of preferred embodiments of the invention on the basis of the figures.

The figures show:

fig. 1 illustrates an exemplary implementation of the method 100 on an injection system 1 of an internal combustion engine 2;

fig. 2 shows a time course of the pressure p in the high-pressure accumulator 11, the setpoint injection quantity q and the vehicle speed v during an exemplary acceleration.

Detailed Description

According to fig. 1, the injection system 1 comprises a high-pressure accumulator 11 which is supplied with fuel 3 from a storage tank 13 by a high-pressure pump 12. The prefeed pump required for operating the plurality of high-pressure pumps 12 is not shown for the sake of clarity. Increasing the pressure p of the fuel 3 in the high-pressure accumulator 11 to the setpoint pressure p by means of the inflow regulator 14 _S. If the setpoint pressure ps drops, the excess quantity 31 of fuel 3 overflows the high-pressure accumulator 11 via the return regulator 15 and is depressurized in step 99 of the method 100 by: the fuel is led back into the storage container 13.

From the high-pressure accumulator 11, fuel 3 is supplied to the injector 17 and is injected by the injector 17 into the cylinder 22 of the internal combustion engine 2. The combustion of fuel 3 in the cylinder 22 drives a piston 21, which is connected to a crankshaft 25 via a connecting rod 23 and a crank 24 and puts the crankshaft 25 in rotational motion. The crankshaft 25 is connected to an automatic transmission 27 via a clutch 26. The torque m generated by the internal combustion engine 2 resists the mechanical load demand L and drives the vehicle.

Since the demand for fuel 3 is dependent on the load demand L, characteristic map 16 provides each load demand L with a value p of this type for the pressure to be set in high-pressure accumulator 11_K: at which the combustion of the fuel 3 takes place most efficiently and at which the emissions of noxious substances and noise are minimal. When the load demand L falls to the operating point 29 with a low load or such a fall is imminent, the value p is set in step 110 of the method 100_KModified to nominal pressure p _SThis setpoint pressure is finally transmitted to the injection system 1.

In block 110a, it is ensured in substep 111 that the setpoint pressure p is present_SNot falling to a predetermined base level p_BThe following. The rate of pressure drop is limited in sub-step 112.On the one hand, the rated pressure p is limited_SDecrease rate dp of_SDt, which affects the nominal pressure p_SModification of (2). On the other hand, the rate of decrease dp/dt of the actual pressure p is limited, which is achieved by acting directly on the return flow regulator 15.

In sub-step 113, the decoupling 26a is evaluated as a signal in which the drop in the load demand L has a temporary characteristic. In sub-step 114, the shift request 27a of the automatic transmission 27 is also evaluated as such a signal. In sub-step 115, the drop in the load demand L is evaluated as temporary when the rate of change of magnitude dL/dt of the drop in the load demand exceeds a predetermined threshold value Δ L. In a substep 116, the time profile l (t) of the load demand is compared with a threshold Ls, and the target injection quantity q is compared with a threshold q_SAnd if necessary by evaluating the driver's desire f: the load demand L drop, which is initially evaluated as temporary, is not temporary but rather continuous.

When it is determined in sub-steps 113 to 116 that there is no temporary drop in the load demand L, then sub-steps 111 and 112 are applied to the nominal pressure p _SAnd the influence on the actual pressure p is neutralized, i.e. the modified nominal pressure variation is disabled.

As long as the rated pressure p_SWith respect to the value p proposed by the characteristic map 16_KIs modified, the strength of the modification is fine-tuned in

blocks

110b and 110 c. In block 110b, the degree of modification is related to the vehicle speed v and to the last engaged gear 27b of the transmission 27. In block 110c, the state variable x of the storage container 13 is additionally taken into account₁State variable x of the part of the fuel supply system affected by the return of fuel 31₂State variable x of fuel 31 to be returned₃And the state variable x of the ambient conditions₄。

Fig. 2 shows a graph of vehicle speed v, required setpoint injection quantity q, which is a measure for load demand L, and pressure p in high-pressure accumulator 11 over time t, according to an exemplary driving operation. The driving is divided into a first acceleration phase I, a stationary phase II and a second acceleration phase III. With respect to the pressure p, in orderComparing the nominal pressure p proposed by the characteristic diagram 16_KAnd modified nominal pressure p_STwo examples of (2) p_S,1And p_S,2Plotted into the same graph.

The first acceleration phase I is briefly interrupted by the two shift phases a and b. Since the transmission of force to the transmission 27 must be interrupted briefly in this case, the load demand and thus the setpoint injection quantity q, respectively, drop to zero. Accordingly, the proposal p according to characteristic diagram 16 _KThe nominal pressure will be substantially reduced to the idling speed p_LL. According to two examples p_S,1And p_S,2Modified nominal pressure p_SRespectively, are significantly higher. Example p_S,1Set mainly against rated pressure p_SRate of change dp of_SBoundary of/dt, and example p_S,2The rate of decrease dp/dt of the actual pressure p is mainly limited.

Any sudden drop in load demand L is first evaluated as a temporary drop. This also applies to the two shift phases a and b in the acceleration phase I.

However, in the stationary phase II, the drop in the load demand L is long, since the vehicle is now travelling in a plane at an almost constant speed. Therefore, an injection quantity q close to zero is first required during freewheeling before a slightly larger injection quantity q is then required again. When at the time point t₁After the modified setpoint pressure change has first been activated, the modified setpoint pressure change is initiated at a time t₂After the end of the predetermined time interval Δ t, the load demand L is again disabled without increasing again.

Example p is also shown in stationary phase II_S,1And p_S,2Another difference between, in example p_S,1Medium rated pressure p_SAdditionally maintained at least at the base pressure p_BUpper, i.e. idling pressure p_LLActually increased to level p _BThe above.

The second acceleration phase III comprises a further shift phase c in which the load demand L briefly drops and, in accordance therewith, the modified setpoint pressure is activated again.

Claims

1. Method (100) for operating an injection system (1) of an internal combustion engine (2), wherein the injection system (1) comprises a high-pressure accumulator (11) for one or more fuels (3) and a setpoint pressure p in the high-pressure accumulator (11)_SAccording to at least one characteristic map (16), a load demand L of the internal combustion engine (2) is followed, wherein excess fuel (3,31) from the high-pressure accumulator (11) is depressurized (99) in order to reduce the actual pressure p in the high-pressure accumulator (11), wherein a setpoint pressure p in the high-pressure accumulator (11) is reduced at least temporarily when the load demand L falls to an operating point (29) with a lower load_SRelative to a value p set for the operating point (29) according to the characteristic map (16)_KIs increased (110,110a-110c), characterized in that the decoupling (26a) of the internal combustion engine (2) is evaluated (113) as a temporary reduction of the load demand L.

2. Method according to claim 1, characterized in that the nominal pressure p_SIs maintained at least at a predetermined base level p _BUpper (111), the base level being higher than a value p set for idling of the internal combustion engine according to a characteristic map_K。

3. Method (100) according to claim 1 or 2, wherein said nominal pressure p is_SAt a maximum and/or minimum time rate of change dp_SThe maximum and/or minimum temporal rate of change dp/dt of the actual pressure p is/are more strongly limited (112) when the load demand L decreases than when the load demand L increases.

4. Method (100) according to claim 1 or 2, characterized in that a request (27a) through an automatic transmission (27) to cause a gear shift process is evaluated (114) as a temporary drop of the load request L.

5. The method (100) according to claim 1 or 2, wherein the amount is madeConstant pressure p_SRelative to a value p set according to a characteristic map (16)_KThe degree of modification is related to the vehicle speed v and/or the last engaged gear (27b) of the manual or automatic transmission (27) (110 b).

6. The method (100) according to claim 1 or 2, characterized in that the drop in the load demand L is evaluated (115) as temporary when the rate of change of the magnitude dL/dt of the load demand drop exceeds a predefined threshold value al.

7. Method (100) according to claim 1 or 2, characterized in that the drop in the load demand L is first evaluated (116) as temporary and, when the load demand L remains below a threshold value Δ L for a predefined time interval, when a nominal injection quantity q exceeds a predefined threshold value q_SThe drop is evaluated as non-temporary and/or when the driver wishes f to correspond to the operating point (29) with lower load.

8. Method (100) according to claim 1 or 2, characterised in that the nominal pressure p is brought to_SRelative to a value p set according to a characteristic map (16)_KThe extent of the modification and the state variable x of the storage container (13)₁A state variable x associated with a fuel supply system part affected by the pressure reduction of the fuel (31) or by the drop in the actual pressure p₂And a state variable x of the fuel (31) to be depressurized₃And/or with ambient environmental conditions x₄And (6) correlating (110 c).

9. Method according to claim 1 or 2, characterized in that liquefied natural gas is used as fuel.

10. A storage medium having stored thereon a computer program product comprising machine-readable instructions which, when executed by a computer and/or controller, cause the computer and/or controller to carry out the method of any one of claims 1 to 9.