DE102007025348A1 - Automotive engine with urea injection to exhaust system has fuel return pipe surrendering heat to urea tank - Google Patents

Abstract

An internal combustion engine has a cylinder with a combustion chamber discharging exhaust gases via an outlet valve to an exhaust system (4). Fuel is measured and introduced to the combustion chamber by an injection valve (18). Excess fuel not injected is returned by a pipe to a fuel tank. The engine has a urea tank (40) with a tube (41) to an injection valve (54) that releases urea into the exhaust system. The return fuel pipe (44) surrenders heat to the urea tank (40) contents.

Description

The The invention relates to an internal combustion engine, the at least one Includes cylinder with a combustion chamber and an exhaust tract, which depends on a switching position of a gas outlet valve communicates with the combustion chamber. A fuel injection valve for metering fuel for a combustion process in the combustion chamber is provided. Not to return metered fuel from the fuel injection valve toward a fuel tank the internal combustion engine, the internal combustion engine has a fuel return line. The internal combustion engine has a urea injection valve for metering of urea in the exhaust tract. The urea can be from a urea tank via a Urea line are led to the urea injection valve.

to Reduction of a nitrogen oxide content in the exhaust gas of an internal combustion engine can an exhaust aftertreatment with aqueous urea solution and a SCR catalyst performed become. The watery urea solution can also be referred to as urea. For exhaust aftertreatment becomes the watery urea solution with a liquid pump pumped to a urea injection valve, which is the urea solution upstream of the SCR catalyst in an exhaust gas stream in an exhaust tract of the internal combustion engine attaches. The urea solution reacts in the hot Exhaust gas flow to ammonia and carbon dioxide. In the SCR catalyst then the ammonia reacts with the nitrogen oxide mixture of the exhaust gas to nitrogen and water.

A Freezing temperature of the urea may be, for example, about -11 ° C. Thus, for example, in winter, the urea solution freeze what can lead to a failure of the urea injection. This prevents the exhaust aftertreatment by means of the urea and leads to a undesirable increase harmful Exhaust emissions.

It Object of the invention, an internal combustion engine and a method and a device for heating of urea, which is a beneficial one Injection of urea into an exhaust tract of an internal combustion engine allows.

The Task is solved by the characteristics of the independent Claims. Advantageous embodiments of the invention are specified in the subclaims.

The Invention is characterized according to a first Aspect of the invention by an internal combustion engine. The internal combustion engine includes at least one cylinder with a combustion chamber. The internal combustion engine has an exhaust tract that depends on a switching position of a gas outlet valve communicates with the combustion chamber. Furthermore, the internal combustion engine comprises a fuel injection valve for metering fuel for a combustion process in the combustion chamber and a fuel return line not to return metered fuel out of the fuel injection valve to a fuel tank of the internal combustion engine. A urea injection valve for metering urea into the exhaust tract and a urea tank are provided. From the urea tank can urea via a urea line are directed to the urea injection valve. The urea tank is so with the fuel return line thermally coupled to the recirculated fuel in the fuel return line the urea can be heated in the urea tank.

The thermal coupling of the fuel return line with the urea tank allows just heating of urea in the urea tank. This can help too prevent the urea from freezing at low temperatures. This carries to the fact that the exhaust aftertreatment by means of urea also possible at low temperatures is.

Further can the heating of the urea contribute to the urea in the hot exhaust stream evaporates better and thus the urea better distributed and the Exhaust gas aftertreatment is further improved. Furthermore, this can do so contribute to a cooler for cooling of the recirculated fuel to renounce.

In an advantageous embodiment of the first aspect of the invention is the fuel return line at least partially passed through the urea tank. This is especially possible simply, the urea in the urea tank by means of the fuel in the fuel return line to warm up.

In a further advantageous embodiment of the first aspect of Invention, the internal combustion engine comprises a first heat exchanger. The first heat exchanger couples the fuel return line thermally with the urea tank. This can help that the urea in the urea tank is heated particularly effectively. In particular, this may help to prevent heat transfer from the fuel in the fuel return line to the urea in the urea tank is particularly effective.

In a further advantageous embodiment of the first aspect of the invention, the internal combustion engine comprises a bypass line and a bypass valve. The bypass passage and the bypass valve are formed and arranged so that the recirculated fuel depends on an opening degree of the Bypass valve can be passed through the bypass line to the fuel tank, without heating the urea in the urea tank. This can help prevent the urea from heating above a threshold temperature where the urea will clot. This can help that the exhaust aftertreatment by means of the urea can be carried out effectively even at high temperatures.

The Invention is characterized according to a second Aspect of the invention by a method and an apparatus for heating Urea. In this case, the fuel is on the fuel return line returned to the fuel tank that the Fuel in the fuel return line heats the urea in the urea tank.

In an advantageous embodiment of the second aspect of the invention Only then will the fuel overflow the fuel return line returned to the fuel tank that the fuel in the fuel return line the urea in heated the urea tank, when a urea temperature of urea in the urea tank is less than a predetermined threshold. This can help to prevent the urea from freezing in the urea tank and / or that the urea over the limit temperature warmed up becomes.

In a further advantageous embodiment of the second aspect of Invention, the fuel is over the bypass line is returned to the fuel tank so that the fuel Urea in the urea tank is not heated when a urea temperature of urea in the urea tank is greater than a predetermined threshold is. This can lead to a particularly economical operation of the internal combustion engine contribute. It can also help to prevent the urea in the urea tank over the limit temperature warmed up is where the urea clots.

embodiments The invention are explained in more detail below with reference to schematic drawings.

It demonstrate:

1 a first view of an internal combustion engine,

2 a second view of the internal combustion engine,

3 a method for heating urea.

elements same construction or function are cross-figurative with the same Reference number marked.

An internal combustion engine 14 ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 , The intake tract 1 preferably comprises a throttle valve 5 , a collector 6 and a suction tube 7 leading to a cylinder Z1-Z4 via an inlet channel into a combustion chamber 9 of the engine block 2 is guided. The combustion chamber 9 communicates depending on a switching position of a gas inlet valve 12 or a gas outlet valve 13 with the intake tract 1 or with the exhaust gas tract 4 , The engine block 2 includes a crankshaft 8th , which has a connecting rod 10 with a piston 11 of the cylinder Z1-Z4 is coupled. The internal combustion engine 14 preferably comprises further cylinders Z1-Z4. The internal combustion engine 14 is preferably arranged in a motor vehicle. The motor vehicle is preferably a passenger vehicle.

In the cylinder head 3 is preferably a fuel injection valve 18 arranged. If the internal combustion engine 14 is not a diesel engine, so preferably each cylinder Z1-Z4 are each assigned a spark plug. Alternatively, the fuel injection valve 18 also in the intake manifold 7 be arranged. A fuel return line 44 allows for recirculation of unappropriated fuel from the fuel injector 18 towards a fuel tank.

Furthermore, the exhaust tract 4 preferably associated with a urea metering device ( 2 ). The urea metering device comprises a urea tank 40 for taking up the urea, a urea injection valve 54 and preferably a pump 42 for supplying the urea injection valve 54 with urea from the urea tank 40 , The urea may be from the urea tank 40 via a urea line 41 by means of the pump 42 to the urea injection valve 54 be directed. The metering of urea into the exhaust tract 4 may additionally or alternatively to the urea injection valve 54 via a urea valve 52 at the urea line 41 to be controlled.

Upstream of the urea injection valve 54 is preferably a soot particle filter 21 arranged. Downstream of the urea injection valve 54 is preferably a mixing device 56 for mixing the metered urea with the exhaust gas. Further, downstream of the mixing device 21 an SCR catalyst 23 arranged. In addition to the SCR catalyst 23 may be upstream of the SCR catalyst 23 and downstream of the mixing device 56 a hydrolysis catalyst may be provided downstream of the SCR catalyst 23 An oxidation catalyst may be provided.

If the internal combustion engine 14 is operated with a lean mixture and thus is in lean operation is in a combustion process of the internal combustion engine 14 the combustion chamber 9 supplied less fuel than with the oxygen in the combustion chamber 9 can be burned. This forms over a stoichiometric operation of the internal combustion engine 14 Increases nitrogen oxides, which are then contained in the exhaust gas. In the presence of ammonia, the nitrogen oxides in the SCR catalyst can 23 react to elemental nitrogen and water. That's why the exhaust tract 4 with the urea injection valve 54 Preferably, the urea is metered from which emerges in a chemical reaction of ammonia. The urea, especially the ammonia, mix mainly in the mixing device 56 with the exhaust gas of the internal combustion engine 14 , The urea may also be referred to as an aqueous urea solution.

A control device 25 is provided, the sensors are assigned, which detect different parameters and each determine the value of the measured variable. The control device 25 determined depending on at least one of the measured variables at least one manipulated variable, which are then converted into one or more control signals for controlling the actuators by means of corresponding actuators. The control device 25 can also be used as a device for operating the internal combustion engine 14 be designated. In particular, the control device 25 be referred to as a device for heating the urea.

The sensors are, for example, a pedal position transmitter 26 , the accelerator pedal position of an accelerator pedal 27 detected, an air mass sensor 28 , the air mass flow upstream of the throttle 5 detected, a temperature sensor 32 sensing an intake air temperature, an intake manifold pressure sensor 34 that produces a manifold pressure in the collector 6 detected, a crankshaft angle sensor 36 , which detects a crankshaft angle, then a speed of the internal combustion engine 14 can be assigned, a urea temperature sensor 43 for detecting a urea temperature TEMP_UREA of the urea in the urea tank 40 , Furthermore, an exhaust gas probe 38 provided, for example, downstream of the SCR catalyst 23 is arranged and detects, for example, the nitrogen oxide content and / or a urea content of the exhaust gas.

ever according to embodiment The invention may be any subset of said sensors be present or it can also additional Sensors be present.

The actuators are, for example, the throttle 5 , the gas inlet and outlet valves 12 . 13 , the fuel injection valve 18 , the urea injector 54 , the urea valve 52 , the pump 42 , a bypass valve and / or possibly the spark plug.

To prevent the urea in the urea tank 40 freezes, is the urea tank 40 thermally with the fuel return line 44 coupled. By means of the fuel return line 44 may be the fuel leading to the fuel injection valve 18 was directed and not the combustion chamber 9 for the combustion process of the internal combustion engine 14 was metered to the fuel tank of the internal combustion engine 14 be returned. The fuel may then again out of the fuel tank to the fuel injection valve 18 for metering the fuel into the combustion chamber 9 the internal combustion engine 14 be directed. Due to the pressure acting on the fuel in the fuel injection valve 18 acts, the fuel heats up, then through the fuel return line 44 is returned. The heated fuel heats the fuel return line 44 , By the thermal coupling of the fuel return line 44 with the urea tank 40 can the urea in the urea tank 40 by means of the warm fuel in the fuel return line 44 to be heated. This can help to prevent the urea in the urea tank 40 freezes. The freezing of the urea impedes or prevents the metering of the urea into the exhaust tract 4 , This reduces or prevents the exhaust aftertreatment by means of the urea. This leads to an increase in harmful pollutant emissions. Further, the heated urea contributes to the urea being injected into the exhaust tract 4 better evaporated and thus finer is distributed in the exhaust system. This may help to make the reaction with the nitrogen oxides in the exhaust more effective than when metering cold urea.

The thermal coupling between the fuel return line 44 and the urea tank 40 is particularly effective when using a first heat exchanger 48 he follows. The first heat exchanger 48 may be part of the fuel return line 44 included by the urea in the urea tank 40 is guided. In addition, a second heat exchanger 50 be provided, the fuel return line 44 thermally with the urea line 41 coupled. The first and the second heat exchanger 48 . 50 can be connected in series.

On a storage medium of the control device 25 is preferably a program for heating the urea provided ( 3 ). The program serves to heat the urea only when it is beneficial, for example, to prevent the urea in the urea tank 40 one freezes. Furthermore, the program is used to prevent the urea is heated too much, for example, to a limit temperature at which the Urea coagulates. The clotting of urea can also help to reduce or completely prevent the effect of exhaust aftertreatment with urea. The program is preferably in a computing unit of the internal combustion engine 14 processed, for example, within the control device 25 ,

The Program is preferably started in a step S1 in which if necessary variables are initialized.

In a step S2, the urea temperature TEMP_UREA of the urea in or on the urea tank 40 determined, for example by means of the urea temperature sensor 43 ,

In one step 53 it is checked whether the urea temperature TEMP_UREA is smaller than a predetermined threshold THD. For example, the threshold value THD may be slightly higher than a freezing temperature of the urea. Alternatively, for example, the threshold may be slightly below the threshold temperature at which the urea coagulates. If the condition of step S3 is met, the processing is in one step 54 continued. If the condition of step S3 is not satisfied, the processing is continued in step S5.

In step S4, by means of an opening instruction OPEN, a bypass valve is activated such that the heated fuel is supplied via a bypass line 46 is directed to the fuel tank, thereby the urea in the urea tank 40 heated at most negligible. For example, the bypass valve may include a first valve downstream of the branch of the fuel return line 44 and upstream of the fuel tank. Alternatively or additionally, the bypass valve may be a second valve upstream of the first heat exchanger 48 and downstream of the branch of the fuel return line 44 include, which may optionally be closed depending on the opening instruction OPEN.

In a particularly simple embodiment of the bypass valve, the bypass valve comprises a heat valve 47 , for example, within the first heat exchanger 48 or downstream of the first heat exchanger 48 is arranged. An opening degree of the heat valve 47 decreases with increasing fuel temperature, especially downstream of the first heat exchanger 48 directly related to the urea temperature TEMP_UREA, and increases at the same time with appropriate dimensioning of the bypass line 46 the fuel flow through the bypass line 46 , In a particularly simple embodiment of the internal combustion engine 14 can the heat valve 47 the program for heating the urea and / or the first and / or second valve and / or the urea temperature sensor 43 replace.

In step S5, the bypass valve, preferably the first valve, is activated by means of a closing instruction CLOSE in such a way that the bypass line 46 is closed and that the fuel preferably via the first heat exchanger 48 and that's how the urea in the urea tank 40 is heated. If necessary, the second valve is opened depending on the closing instruction CLOSE.

In a step S6, the program can be terminated. Preferably, the program is during operation of the internal combustion engine 14 regularly processed.

The heated urea in the urea tank 40 serves as an energy store, so that the next time you start the engine 14 the heated urea is available. Further, by the heat transfer to the urea, the fuel in the fuel return passage cools 44 from. This can help to dispense with a fuel cooler for cooling the recirculated fuel.

The invention is not limited to the specified embodiment. For example, only the urea in the urea tank 40 be heated and on the second heat exchanger 50 be waived. Further, the urea heating program may be implemented in a parent program or divided into one or more subprograms.

Claims (8)

Internal combustion engine ( 14 ), - at least one cylinder (Z1) with a combustion chamber ( 9 ), - an exhaust tract ( 4 ), which depends on a switching position of a gas outlet valve ( 13 ) with the combustion chamber ( 9 ), - a fuel injection valve ( 18 ) for metering fuel for a combustion process in the combustion chamber ( 9 ), - a fuel return line ( 44 ) for returning unallocated fuel from the fuel injection valve ( 18 ) to a fuel tank of the internal combustion engine ( 14 ), - a urea injection valve ( 54 ) for metering urea into the exhaust gas tract ( 4 ), - a urea tank ( 40 ) from which via a urea line ( 41 ) Urea to the urea injection valve ( 54 ) and the so with the fuel return line ( 44 ) is thermally coupled with the recirculated fuel in the fuel return line ( 44 ) the urea in the urine fuel tank ( 40 ) is heated. Internal combustion engine ( 14 ) according to claim 1, wherein the fuel return line ( 44 ) at least partially through the urea tank ( 40 ) is guided. Internal combustion engine ( 14 ) according to one of the preceding claims, comprising a first heat exchanger ( 48 ), the fuel return line ( 44 ) thermally with the urea tank ( 40 ) couples. Internal combustion engine ( 14 ) according to one of the preceding claims, which is a bypass line ( 46 ) and a bypass valve which are formed and arranged so that the recycled fuel depending on an opening degree of the bypass valve via the bypass line ( 46 ) can be directed to the fuel tank without the urea in the urea tank ( 40 ) to heat. Process for heating urea in the urea tank ( 40 ) of the internal combustion engine ( 14 ) according to one of the preceding claims, in which the fuel is thus supplied via the fuel return line ( 44 ) is returned to the fuel tank, that the fuel in the fuel return line ( 44 ) the urea in the urea tank ( 40 ) is heated. Method according to Claim 5, in which the fuel is then supplied via the fuel return line ( 44 ) is returned to the fuel tank, that the fuel is the urea in the urea tank ( 40 ) when a urea temperature (TEMP_UREA) of the urea in the urea tank ( 40 ) is less than a predetermined threshold (THD). Method according to one of claims 5 or 6, wherein the fuel via the bypass line ( 46 ) is returned to the fuel tank such that the fuel urea in the urea tank ( 40 ) is not heated when a urea temperature (TEMP_UREA) of the urea in the urea tank ( 40 ) is greater than a predetermined threshold (THD). Device for heating urea in the urea tank ( 40 ) of the internal combustion engine ( 14 ) according to one of claims 1 to 4, wherein the device is adapted to the fuel via the fuel return line ( 44 ) to the fuel tank that the fuel is the urea in the urea tank ( 40 ) is heated.