EP2014908A1 - Combustion engine that can be operated either with diesel or biogenous fuel - Google Patents

Abstract

The internal combustion engine comprises a switching valve (5) arranged at an input side of a high-pressure pumping device. A low viscosity fuel conducting inlet or high viscosity fuel conducting inlet are selectively interconnected with an inflow into the high-pressure pumping device. The switching valve is a 3/ 2 directional-control valve. An independent claim is also included for a method for operating an internal-combustion engine, particularly self-igniting internal combustion engine.

Description

The invention relates to an internal combustion engine, in particular a self-igniting internal combustion engine, which is operated alternately with a low-viscosity fuel, in particular diesel, and a viscous fuel, in particular rapeseed oil, wherein the thin liquid fuel receiving additional tank via a filter device and a conveyor and the viscous fuel receiving Main tank are connected via a filter assembly and a conveyor assembly via supply lines to a common high-pressure pump means and a low-pressure outlet of the high-pressure pump means is connected via a return line system to the main tank and the auxiliary tank, and a method for operating such an internal combustion engine.

Such an internal combustion engine is from the DE 38 00 585 A1 known. This internal combustion engine relates to a device for alternative operation of a diesel engine with low-viscosity fuel, in particular diesel oil, and viscous fuel, in particular rapeseed oil, both fuels are supplied via a series injection pump to the injection valves of the internal combustion engine. In this case, a device is provided which is intended to ensure, on the one hand, an optional supply of one of the two fuels to the series injection pump and with which a rinsing of the low-pressure system of the fuel system is to take place. This whole device is essentially pressure controlled.

The invention has for its object to provide an internal combustion engine and a method for operating such an internal combustion engine, with the or a reliable, changing operation with different fuels is possible, in particular, the control of the switching operations should be optimized.

This object is achieved according to a first embodiment, characterized in that the input side of the high-pressure pumping device, a first switching valve is arranged, which selectively connects the low-viscosity fuel leading feed or the viscous fuel leading supply with the entry into the high-pressure pump device. By arranging a switching valve on the input side to the high-pressure pump device can be made very selectively a switching between different fuels. In contrast to a controlled only via the fuel pressure switching between different fuels thereby a precise switching point is known, from which the high-pressure pump device, a certain fuel is supplied. The exact knowledge of the switching point can be evaluated in many different ways. In principle, it should be pointed out that the low-viscosity fuel, in particular diesel fuel, and the viscous fuel, is a biogenic fuel. In the context of the invention, a biogenic fuel is in particular rapeseed fuel, but in principle it can also be a fuel obtained from another vegetable oil. The same advantages are achieved when the input side of the high-pressure pump device, a first switching valve is arranged, which selectively connects the viscous fuel leading supply with the entry into the high-pressure pump device or with an opening into the main tank short-circuit line and the low-viscosity fuel supply leading via a check valve in the entrance opens into the high-pressure pump device.

In a further development of the invention, the first switching valve is a 3/2-way valve. Such a valve is particularly suitable for the required switching. Furthermore, the high-pressure pump device has a fuel metering device and at least one downstream high-pressure pump. With the high-pressure pump device designed in this way, a pressure accumulator designed as a rail is filled with fuel, valve-controlled injection valves being connected to the rail. By means of the injection valves, the individual combustion chambers of the internal combustion engine, controlled by an electronic control device, which otherwise takes over the entire engine control, supplied fuel. Since the volumes of the described components are known or can be determined in the basic design of the system, it is thus possible to determine very precisely after what time a switchover from a first fuel to the second fuel at the metering device and / or in the rail is a partial one or complete replacement of the fuel. This knowledge is useful, for example, for a planned shutdown of the internal combustion engine. Thus, an optionally operated with rapeseed fuel or diesel fuel internal combustion engine is normally started with diesel fuel to ensure trouble-free starting behavior. After the successful start and the exceeding of a predetermined load request can then be switched to rapeseed fuel. By knowing exactly which fuel is in the rail, the possible Abstellzeitpunkt the internal combustion engine after operation with rapeseed oil and the subsequent switch to diesel fuel can be accurately determined. As a result, an unnecessarily long operation of the internal combustion engine is avoided. The internal combustion engine designed according to the invention is preferred for operating agricultural equipment or vehicles, such as tractors, for example. used, especially since in such an application, the use of rapeseed fuel ecological and financial benefits.

In a further embodiment of the invention, the fuel metering device opening into a Rücklaufleitungsarm low-pressure outlet, wherein in the divided into two arms return line arms, a second changeover valve and a third changeover valve are arranged, the low pressure output via an additional tank return line to the additional tank or a main tank return line to the main tank boarded. By a corresponding actuation of the second changeover valve and of the third changeover valve, it is therefore possible to precisely determine in which tank the fuel diverted by the fuel metering device is passed. It should be noted that the fuel metering device is always supplied with a larger amount of fuel than is maximally promoted by the one or more high-pressure pump (s) at maximum load of the internal combustion engine in the rail and is therefore injected from the injectors into the combustion chambers. The inventive design, it is thus possible to ensure that especially in the diesel fuel-absorbing lance no rapeseed fuel is introduced by, for example, after a switching from rapeseed fuel to diesel fuel, the second switching valve and the third changeover valve are kept in a switching position as long as the the Kraftstoffzumesseinrichtung diverted fuel into the main tank, until applied to the second switching valve and the third switching valve diesel fuel. The second switching valve and the third switching valve are consequently switched over in time to the first switching valve. Incidentally, this time delay is such that it is shorter in a switching process from diesel fuel to rapeseed fuel than vice versa. It can be tolerated, if a small amount of diesel fuel in the rapeseed fuel receiving main tank is discharged, while for the reasons listed above, the reverse process is undesirable.

In a further embodiment, the second changeover valve and the third changeover valve are two jointly operable 2/2-way valves. These two valves can therefore be operated by a common relay. It is also possible to combine the two jointly operable 2/2-way valves to a 3/2 way valve.

In a further embodiment of the invention, the conveyor assembly is a mechanically driven by the internal combustion engine feed pump. These are usually the normal on an internal combustion engine, which is equipped with a conventional, fuel-only injection system, built-in delivery pump including the filters still installed. Thus, in the event that the internal combustion engine is operated with diesel fuel, which is supported by an electrically operated and consequently switched on or off feed pump, the permanently operated mechanical feed pump does not promote against a closed valve, the rapeseed fuel promoting supply to the fuel metering device interconnected via a shut-off device with associated line connections to the main tank. When switching from rape fuel to diesel fuel, the shut-off device, which is otherwise designed as a fourth switching valve, actuated accordingly. In the second embodiment, the fourth switching valve is not needed, since then the first switching valve assumes this switching function.

In a further embodiment, a heating device is switched on in the viscous fuel leading supply, which is connected to the engine cooling medium. The heating device is designed in such a way that the temperature of the viscous fuel can be regulated as constant as possible to a predeterminable temperature.

The method steps contain advantageous details for operating a correspondingly designed internal combustion engine.

Fig. 1

ein Schaltschema des Kraftstoffsystems bei Betrieb mit Dieselkraftstoff,

Fig. 2

das Schaltschema mit der Stellung "Betrieb mit Rapskraftstoff",

Fig. 3

das Schaltschema in der Stellung "Spülbetrieb Rapskraftstoff",

Fig. 4

das Schaltschema in der Schaltstellung "Spülbetrieb Dieselkraftstoff"

Fig. 5

ein Schaltschema des Kraftstoffsystems bei Betrieb mit Dieselkraftstoff in einer zweiten Ausführungsform und

Fig. 6

das weitere Kraftstoffsystem von der Kraftstoffzumesseinrichtung bis zu den Einspritzventilen.

Further advantageous embodiments of the invention are described in the drawings, is described in more detail in the embodiments illustrated in the figures. Show it:

Fig. 1

a schematic diagram of the fuel system when operating with diesel fuel,

Fig. 2

the circuit diagram with the position "operation with rape fuel",

Fig. 3

the circuit diagram in the position "rinsing operation rapeseed fuel",

Fig. 4

the circuit diagram in the switching position "Flushing Diesel Fuel"

Fig. 5

a schematic diagram of the fuel system when operating with diesel fuel in a second embodiment and

Fig. 6

the further fuel system from the fuel metering to the injectors.

Basically, it should be noted for the operation of the internal combustion engine described below that this is operated either with diesel fuel or with a biogenic fuel, in particular rapeseed fuel. A continuous mixing operation with said fuels should not be provided. Accordingly, the internal combustion engine, which is preferably used in agricultural Appliances or vehicles is used, operated in diesel mode exclusively with diesel fuel. The diesel fuel is filled in an auxiliary tank 1, which is connected via a diesel pre-filter 2, an electric feed pump 3, a diesel main filter 4 with a first switching valve 5, which is designed as a 3/2-way valve, via line sections 6a, 6b, 6c, 6d. In the diesel mode, the line section 6d is interconnected by a corresponding position of the first changeover valve 5 with a supply line 7 to a fuel metering device 8, which controls the fuel supply ( Fig. 6 ) in particular two designed as plug pumps high pressure pumps 9 controls, of which the fuel is conveyed in a common rail 10. With the rail 10 injection valves 11 are connected, which, controlled by an electronic control device 12 (of which all other components of the internal combustion engine, including the directional control valves and the feed pump 3 can be controlled), inject fuel in each case a combustion chamber of the internal combustion engine. To generate the most uniform possible pressure in the rail 10 driven by a camshaft 13 high-pressure pumps 9 are actuated in a design of the internal combustion engine as a 6-cylinder internal combustion engine each of three correspondingly distributed on the circumference of the camshaft cam 13 per camshaft rotation. Correspondingly, in the case of a 4-cylinder internal combustion engine, two cams per high-pressure pump 9 are distributed on the circumference of the camshaft 13. Incidentally, the camshaft 13 in addition to the cam for actuating the high-pressure pumps 9 more cams for the actuation of gas exchange valves.

The fuel metering device 8 has the FIG. 1 a low-pressure side fuel return in the form of a return line 14. The return line 14 branches into two return line arms 14a, 14b, wherein the return line arm 14a via a third change-over valve 15 to the auxiliary tank 1 via an additional tank return line 16 is fluidly connected. Consequently, the fuel metering device is used 8 recycled diesel fuel fed back into the auxiliary tank 1 during diesel operation, since a second switching valve 25, which - as explained later - the return line arm 14b connected via a main tank return line 27 to a main tank 17, is connected in a blocking position. The second switching valve 25 and the third switching valve 15 are always operated simultaneously and can be operated by a common relay. Also, the two switching valves 25, 15 can be combined to form a switching valve.

Based Fig. 2 the rapeseed operation is described in detail.

The rape fuel is filled in the main tank 17 of the device or vehicle, the main tank 17 generally having a larger capacity than the auxiliary tank 1. The reason for this is that the internal combustion engine is operated predominantly with rapeseed fuel and should be operated only for starting, at low load and for stopping with diesel fuel. Accordingly, the diesel fuel consumption is significantly lower than the rapeseed fuel consumption and the auxiliary tank 1 for the diesel fuel can be made considerably smaller. Preferably, the tank volumes are sized such that at average operating conditions, both tanks reach a tank level requiring refueling at about the same time.

From the main tank 17, the rapeseed fuel via a pre-filter 18 through a heat exchanger 19 (these two components can also be connected in reverse order) via a feed pump 20 with a pressure relief valve device and a main filter 21 to a second input of the first switching valve 5, then is in a rapeseed fuel via the supply line 7 of the fuel metering device 8 supplying switching position. The aforementioned components are accordingly over fuel line sections 22 interconnected from the main tank 17 to the beginning in the switching valve 5. From the opening into the first switching valve 5 fuel line section 22 branches off a short-circuit line 23, in which a fourth switching valve 24, which is also designed as a 2/2-way valve, is turned on. The short-circuit line 23 opens into the main tank return line 27, which opens into the main tank 17. In rapeseed operation, the fourth change-over valve 24 is in a blocking position, that is to say that no rapeseed fuel delivered by the feed pump 20 reaches the main tank 17 via the short-circuit line 23.

In rapeseed operation, on the other hand, the aforesaid second change-over valve 25 is switched to passage, that is, rapeseed fuel controlled by the fuel metering device 8 is returned to the main tank 17 via the return line arm 14b and the main tank return line 27. The third switching valve 15 is thus connected in the blocking position.

The heat exchanger 19 is controlled by a fifth, also designed as a 2/2-way valve switching valve 26 connected to the cooling circuit of the internal combustion engine. The rapeseed fuel is viscous at normal ambient temperature and accordingly poorly recoverable. Therefore, the rapeseed fuel during operation of the internal combustion engine is heated to about 55 ° C to 75 ° C, preferably to 65 ° C and then has a similar viscosity as diesel fuel. Incidentally, such heating is provided up to ambient temperatures at which rapeseed fuel can still be conveyed due to its viscosity, for example minus 5 ° C. The heating can be continuous or else temperature-controlled, in this case, for example, behind the heat exchanger 19 or behind the feed pump 20, a temperature sensor is provided. At lower ambient temperatures (in winter) the rape fuel can be released from the rape fuel system and the Rapeseed fuel system can be filled with diesel fuel. This (winter) filling is especially intended to keep the tank intervals at the normal level during the pure diesel winter operation. In addition, it can finally be provided that at temperatures below -5 ° C automatically switched to diesel mode.

In Fig. 3 shows the switching from diesel operation to rapeseed operation, the components have been previously explained and only the individual switching valves are switched differently.

When switching from diesel operation to rapeseed initially the first switching valve 5 is still in the blocking circuit for rapeseed fuel to the fuel metering device 8 and the fourth switching valve 24 in the Absteuerstellung in the main tank 17. The rapeseed fuel circuit has in this switching position to a low pressure to the pumping losses keep as low as possible. For this purpose, it should be additionally stated that the delivery pump 20 with a delivery rate of about 5 liters per minute, as well as the other elements of the rapeseed fuel train, are the normal elements for fuel delivery installed on an internal combustion engine. As a result, the feed pump 20 is mechanically driven. A mechanical drive is chosen because of the required high drive power. If the first changeover valve 5 were switched over to the transfer of rapeseed fuel to the fuel metering device 8 and the fourth changeover valve 24 was switched to its blocking position at the same time, the fuel pressure in front of the fuel metering device 8 would break in the short term. In order to prevent this, when switching from diesel operation to rapeseed operation is initiated, first the fourth changeover valve 24 is connected to the blocking position and thereafter with a time delay the first changeover valve 5 into the feed position of rapeseed fuel to the fuel metering device 8 connected. Alternatively, the timing of the switching operation can be pressure-controlled, for example, by measuring and evaluating the pressure prevailing in the rapeseed fuel line section 22 before the first changeover valve 5. However, it is also possible to store a delay time value which varies as a function of the rotational speed of the internal combustion engine in the electronic control device 12 controlling the entire system. Due to the known line volumes and the speed-dependent known delivery rate of the feed pump 20, this value can be determined very accurately and accordingly the switching delay can be determined very accurately. After the first switching valve 5 is switched to continuation of rapeseed fuel to the fuel metering device 8, the second switching valve 25 and the third switching valve 15 are switched time-delayed, in the form that the first switched to Absteuerung in the auxiliary tank 1 third switching valve 15 in his Locking position is adjusted and simultaneously the second switching valve 25 is moved to the Absteuerposition of fuel in the main tank 17. The delay is such that no rapeseed fuel is discharged into the additional tank 1. Conversely, however, it is permitted that a (small) amount of diesel fuel is discharged into the main tank 17. A small quantity of diesel fuel discharged into the main tank 17 has no negative effect on the operating behavior of the internal combustion engine. On the other hand, the diesel fuel in the additional tank 1 should not be mixed as much as possible with rapeseed fuel. Simultaneously with the switching of the first switching valve 5, finally, the electric pump 3 is turned off.

In Fig. 4 is shown the switching from rapeseed fuel to diesel fuel. In an initiated changeover process, the electric feed pump 3 is first switched on before the switching of the first switching valve 5, so that in the line sections 6, a sufficient pressure is built up. Because the electric pump 3 is operated at a constant speed, the time is up to a successful pressure build-up as a constant value determined and stored accordingly in a memory of the electronic control device 12. After the pressure buildup in the line section 6d, the first switching valve 5 is switched to the passage position of diesel fuel to the fuel metering device 8, and the fourth switching valve 24 is simultaneously switched to the dumping position in the main tank 17. The second switching valve 25 and the third switching valve 15 are again delayed simultaneously switched, but in this switching operation, the time delay is so long that the return line 14 leads at least to the branching point in the return line arms 14a, 14b diesel fuel. That is, the rinsing process of the rapeseed fuel is timed so long that no rape fuel can get into the auxiliary tank 1, and it, as already stated, is completely unproblematic when a small amount of diesel fuel enters the main tank 17.

In the Fig. 5 illustrated embodiment differs from that in the Fig. 1 - 4th illustrated embodiment in that the first switching valve 5a is connected differently and the line section 6d opens via a check valve 28 directly into the supply line 7. The first switching valve 5a is switched so that it absteuert the rapeseed fuel into the short-circuit line 23 in the illustrated first switching position. In the short-circuit line 23, a throttle device may be used, which maintains the pressure level in the fuel line sections 22 at a predetermined value. As a result, when switching to the second switching position of the switching valve 5a, in which the rape fuel is fed into the supply line 7, a power loss switchover to rapeseed fuel operation ensured. In the illustrated first switching position of the feed pump 3, the diesel fuel for diesel fuel operation the internal combustion engine via the check valve 28 is conveyed directly into the supply line 7. In a rapeseed fuel operation, the check valve 28 prevents rapeseed fuel from entering the auxiliary tank 1 in the line section 6d and thus when the feed pump 3 is switched off. Accordingly, another check valve may be inserted from the first switching valve 5a coming into the supply line 7. Furthermore, in particular in the rapeseed fuel line behind the pre-filter 18, a manual feed pump be used. The switching operations correspond mutatis mutandis to the previously described switching operations according to the first embodiment.

Further circuit details are described below. If an applicable load is exceeded or undershot, which is demanded by the internal combustion engine, for example, by an accelerator pedal specification (for example, 25% of the maximum load) is only switched when the applied load level is not passed again within an applicable time again. There are two different times can be specified, one for exceeding, one for underrun. A conceivable timing is in the range between ten seconds and one minute.

This device reliably prevents the case where the internal combustion engine is operated in the preset load limit range between the two fuel supply systems continuously switched back and forth.

A switch from rape fuel operation to diesel fuel operation is possible at any time. For this purpose, for example, a corresponding switch device is provided in the control cabin of the device or vehicle, with which the switching operation is initiated. Such a switching operation is useful if, for example, an inventively designed internal combustion engine in an agricultural Device or vehicle is installed and this device or vehicle is on the way back to the depot. The driver knows that for switching off the internal combustion engine, a switching process must be carried out from rapeseed fuel operation to diesel fuel operation, because the internal combustion engine can be started or should at least normally only with diesel fuel. In order not to have to unnecessarily continue to operate the internal combustion engine for a flushing operation after arrival at the depot, which is optionally automatically initiated by the load underflow described above, the manual switching is provided. For this purpose, it may be provided within the scope of the invention that the driver or operator receives corresponding reference values, if appropriate as a function of operating conditions, for example in the form of stickers. Furthermore, it can be provided that the corresponding rinsing operations are represented by, for example, illuminant displays (for example light-emitting diodes). Thus, the rape fuel operation is indicated by a number (for example, six) of lit LEDs, while in diesel mode the LEDs are extinguished. When changing from Rapskraftstoffbetrieb to diesel fuel operation is then switched from a constant light operation to a fast flashing operation and extinguish according to the progress of the flushing the LEDs. Conversely, in a change from diesel fuel operation to rapeseed fuel operation, the light-emitting diodes light up one after the other in a slower frequency up to the aforementioned continuous light operation. The proportion of the respective fuel according to the respective display is normally related to the rail 10 and is calculated or alternatively or additionally measured by a sensor. Of course, the information about the progress of the respective rinsing process can also be displayed in a different form or else additionally or alternatively in the form of an acoustic signal transmission. Finally, in a particularly comfortable trained system in a display, the necessary Restspülzeit or Remaining running time of the internal combustion engine to be displayed directly when changing to Rapskraftstoffbetrieb. The corresponding drive unit evaluates the already basically explained signals to load, speed of the internal combustion engine, the pressures in the injection total system and the stored parameters on line diameter and line lengths including the resulting resulting volume.

In a manually initiated flushing can be provided as a further option to passively increase the idle speed when the purge operation is initiated at low idle speed. This option is provided to reduce purging time.

The electronic control device 12, which controls the internal combustion engine as a whole, can furthermore be configured such that a previously calculated volumetric flow for achieving or maintaining the desired pressure in the rail 10 is calculated via the fuel metering device. This total volume flow consists of two parts, the pilot proportion and the controller part. The pilot proportion is essentially directly proportional to the amount per injection and the speed of the internal combustion engine, in principle from the fuel consumption. In addition, the function-related leaks of the injectors 11 are already held at the pilot fraction.

As a result of, for example, a scattering of the injection quantity or fluctuations in the fuel admission pressure or even with every change in the setpoint specification for the pressure in the rail 10, regular deviations occur which can not be compensated for by the precontrol component alone. It is precisely these control deviations that form the input variables for the controller component, which is divided into three parts, namely proportional, integral and differential components. These individual shares and the pre-tax portion form additively the total volume flow requirement to the fuel metering 8th

The behavior of the fuel metering device 8 is in turn stored in the electronic control device 12 in the form of characteristic curves. This behavior is also dependent on the properties of the fuel, in particular the viscosity. Accordingly, storage can be carried out separately for diesel fuel and rapeseed fuel, but it can also be provided to store only the characteristic diagrams, for example for diesel fuel, and to determine the characteristic fields for rapeseed fuel from these characteristics maps with corresponding correction factors.

reference numeral

1

additional tank

2

Dieselvorfilter

3

feed pump

4

Diesel main filter

5

first changeover valve

6a, 6b, 6c, 6d

line section

7

feed

8th

fuel metering

9

high pressure pump

10

Rail

11 1

Injector

12

electronic control device

13

camshaft

14, 14a, 14b

Rücklaufleitungsarm

15

third changeover valve

16

Additional tank return line

17

main tank

18

prefilter

19

heat exchangers

20

feed pump

21

main filter

22

Fuel line sections

23

Short-circuit line

24

fourth changeover valve

25

second changeover valve

26

fifth changeover valve

27

Main tank return line

28

check valve

Claims (16)

Internal combustion engine, in particular autoignition internal combustion engine, which is operated alternately with a thin liquid fuel, especially diesel, and a viscous fuel, especially rapeseed oil, wherein the thin liquid fuel receiving additional tank via a filter device and a conveyor and the viscous fuel receiving main tank via a filter assembly and a conveyor arrangement are connected via feeds to a common high-pressure pump device and a low-pressure outlet of the high-pressure pump device is connected to the main tank and the auxiliary tank via a return line system,
characterized in that on the input side of the high-pressure pump device, a first switching valve (5) is arranged, which selectively connects the low-viscosity fuel leading feed or the viscous fuel leading supply with the entry into the high-pressure pump device. Internal combustion engine, in particular autoignition internal combustion engine, which is operated alternately with a thin liquid fuel, especially diesel, and a viscous fuel, especially rapeseed oil, wherein the thin liquid fuel receiving additional tank via a filter device and a conveyor and the viscous fuel receiving main tank via a filter assembly and a conveyor assembly via Feeders are connected to a common high-pressure pump device and a low-pressure outlet of the high-pressure pump device is connected to the main tank and the auxiliary tank via a return line system,
characterized in that the input side of the high-pressure pump device, a first switching valve (5a) is arranged, which selectively connects the viscous fuel leading supply with the entry into the high-pressure pump device or with a main tank (17) opening short-circuit line (23) and that the low-viscosity fuel leading Feeding via a check valve (28) opens into the inlet to the high-pressure pump device. Internal combustion engine according to claim 1 or 2,
characterized in that the first switching valve (5) is a 3/2 way valve. Internal combustion engine according to one of the preceding claims, characterized in that the high-pressure pump device has a fuel metering device (8) and at least one downstream high-pressure pump (9). Internal combustion engine according to claim 4,
characterized in that the fuel metering device (8) has a low pressure outlet opening into a return line arm (14), wherein a second changeover valve (25) and a third changeover valve (15) are arranged in the return line arms (14a, 14b) Connect the additional tank return line (16) to the additional tank (1) or via a main tank return line (27) to the main tank (17). Internal combustion engine according to claim 5,
characterized in that the second switching valve (25) and the third switching valve (15) are two jointly operable 2/2-way valves. Internal combustion engine according to one of the preceding claims, characterized in that the shut-off device is a fourth switching valve (24) which is designed as a 2/2-way valve. Internal combustion engine according to one of the preceding claims, characterized in that the conveyor assembly is a mechanically driven by the internal combustion engine feed pump (20). Internal combustion engine according to one of the preceding claims, characterized in that the viscous fuel leading supply via a shut-off device with associated line connections to the main tank (17) is connected. Internal combustion engine according to one of the preceding claims, characterized in that in the viscous fuel leading supply a heating device is provided. Internal combustion engine according to claim 10,
characterized in that the heating device is connected to the engine cooling medium. Method for operating an internal combustion engine, in particular a self-igniting internal combustion engine, which is operated alternately with a low-viscosity fuel, in particular diesel, and a viscous fuel, in particular rapeseed oil, wherein a thin tank receiving the additional fuel tank via a filter device and a conveyor and the viscous fuel receiving Main tank via a filter assembly and a conveyor assembly are connected via feeds to a common high pressure pump means and a low pressure outlet of the high pressure pump means via a return line system to the main tank and the auxiliary tank is connected, characterized in that the low-viscosity fuel supply leading or the viscous fuel leading supply by means of a first switching valve (5) alternately can be interconnected with the high-pressure pump device. Method for operating an internal combustion engine, in particular a self-igniting internal combustion engine, which is operated alternately with a low-viscosity fuel, in particular diesel, and a viscous fuel, in particular rapeseed oil, wherein a thin tank receiving the additional fuel tank via a filter device and a conveyor and the viscous fuel receiving Main tank are connected via a filter assembly and a conveyor assembly via feeders to a common high-pressure pump device and a low-pressure outlet of the high-pressure pump device via a return line system to the main tank and the auxiliary tank is connected, characterized in that the viscous fuel leading supply via a input side of the high-pressure pump means arranged first Changeover valve (5a) optionally with the entry into the high-pressure pump device or with a in the main tank (17) mü Shorting line (23) is interconnected and that the low-viscosity fuel leading feed via a check valve (28) opens into the inlet to the high-pressure pump device. Method according to claim 12,
characterized in that the viscous fuel leading supply in the event of their shut-off to the high-pressure pump device via a short-circuit line (23) to the main tank (17) is connected. Method according to one of claims 12 to 14,
characterized in that on the output side of the high-pressure pump device a switching device with a second switching valve (25) and a third changeover valve (15) is provided which connects a low-pressure outlet of the high-pressure pump device via separate return lines to the main tank (17) or the auxiliary tank (1), wherein the second changeover valve (25) and the third changeover valve (15) with a time delay to the first changeover valve (5) are switchable. Method according to claim 15,
characterized in that the time delay is variably adjustable.

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