DE4240239A1 - Turbo-charged combustion engine with bypass valve serving intake air-cooler - allows cooling of recirculated combustion prods. or of fresh air for combustion purposes according to engine load. - Google Patents

Abstract

The combustion prods. from e.g. four cylinders (12) are exhausted (14) through a turbocharger (16) whose turbine (18) drives a compressor (20) of the intake air (22). A changeover valve (28) closes the bypass line (34) to the compressed air which passes through the cooler (32) when higher engine output is demanded. For lower output, the exhaust gas turbine is bypassed (44) by a regulator valve (46) and exhaust is admitted by another valve (56) to the cooler, while the changeover valve holds the bypass line (34) open. The throttle valve is electrically controlled. ADVANTAGE - NOx emission is reduced over a wide range of load, with the same cooler operating on the combustion air at higher loads and on recirculated exhaust gas at lower loads.

Description

The invention relates to an internal combustion engine, the with exhaust gas recirculation and charge air cooling is equipped. In addition, the recirculated exhaust gases can Cooler to be cooled.

The charging of the air leading to the engine serves u. a. to Performance increase of the corresponding internal combustion engine seem. So it can in the respective cylinder for the combustion air mass used per combustion cycle are increased, what combined with a correspondingly higher fuel quantity leads to the desired higher power yield.

Because the air mass available for combustion the higher, the cooler this air is into the combustion chamber reaches, the charge air is cooled in many cases before it enters the combustion chamber.

By recirculating parts of the exhaust gas into the combustion chamber of an internal combustion engine, the combustion peak temperature is reduced. This is extremely desirable for reasons of reduced NO _x emissions. This effect can be significantly increased if the recirculated exhaust gases are additionally cooled before they are fed into the combustion chamber of the internal combustion engine again. This applies to both petrol and diesel engines.

The higher the efficiency, the greater the efficiency of a cooler Temperature of the gas entering the cooler.  

State of the art

From EP-A-0 080 327 it is known to have a separate one cooler for the exhaust gases to be returned and for the drawer to provide air. However, placing two coolers bumps especially in the case of passenger cars in almost insoluble space problems. The economic is also not to be neglected che effort caused by the arrangement of two coolers stands.

In addition, it is known from DE-PS 23 21 970, the Charge air and the amount of exhaust gas to be recycled together to manage a single cooler and thus cool down together len. However, this has the disadvantage that, for. B. at niedi low engine load, at which there are still no significant temperatures the charge air is present, the recirculated exhaust gas in terms of flow in front of the radiator through the cold charge air is cooled, which reduces the efficiency in the cooler.

Presentation of the invention

The invention is based, based on the task state of the art, an improved internal combustion engine Specify the machine at which the above described parts are avoided.

This invention is given by the features of claim I. The internal combustion engine according to the invention, he makes it possible that through the existing cooler for cooling the recirculated exhaust gases, the air to be introduced into the combustion chamber of the internal combustion engine can also be passed between zero and 100 percent and thus cooled. The invention is thus based on the knowledge that the fresh air or the charge air and the exhaust gas led out preferably not at the same time, but offset in time and thus can be passed in succession through one and the same cooler. At z. B. low and medium partial load of the internal combustion engine can then preferably preferably be recirculated exhaust gas through the cooler before it enters the combustion chamber. At higher loads, including full load, more or less charged air can be sent through this cooler in any quantity and the exhaust gases cannot be sent through. At low partial loads, the air does not need to be cooled, so that the cooling capacity can then be more or less completely available for cooling the recirculated exhaust gas. Depending on the cooling of the air that becomes necessary at higher partial loads, the cooling of the recirculated exhaust gas can then be reduced accordingly. This allows an additional reduction in temperature-dependent nitrogen emissions (NO _x emission) to be achieved in wide load ranges of an internal combustion engine, with the aid of a single cooler, which can also be used for cooling the more or less charged air.

Such an internal combustion engine can be thereby realize in a very simple way that the cooler immediate bypass line for the in the combustion chamber air is arranged. This bypass line can both of the charge air between the turbocharger and cooler Supply line as well as from the turbocharger or its air Branch off the fresh air supply line leading the compressor. over an air baffle can then the cooler or Air compressor flowing air between zero and 100 percent be released or blocked.

The amount of exhaust gas recirculated can preferably be by a timing valve or by a throttle valve or the like be regulated or controlled.  

Depending on the cooling performance of the single cooler and / or the spatial conditions, the cooler can for example a gas / gas or gas / liquid heat exchanger his. The cooling capacity can also be increased by another cooler, such as a precooler. A such additional cooler could be used as a heat exchanger be formed by that provided for the engine cooling Cooling water would flow through.

In order to increase the mass of discharged into the combustion chamber the fresh air can be directed through the turbocharger and be condensed with it. Combustion is also a compression because of the higher efficiency of the cooler arrested.

The higher the air and / or exhaust gases are compressed in the combustion chamber are initiated, the more important it becomes to cool them down Gases. By cooling the expansion downstream In the turbocharger, very highly compressed gases can be achieve additional cooling of the gases.

In cases where the exhaust gas is through an exhaust gas purification system (Catalyst and / or soot filter) is derived, the amount of exhaust gas to be recycled only after this exhaust gas purification location. In order to still be sufficient Pressure drop in the lines returning to the combustion chamber si can either be in the exhaust and thus flow out on the side behind the exhaust gas cleaning system and / or in or throttling the gas flows in the lines leading into the engine Facilities are provided.

Further features and advantages of the invention are those in the Claims further specified features and the follow the exemplary embodiments.  

Brief description of the drawing

The invention is described below with reference to the drawing illustrated embodiments described and he purifies. Show it:

Fig. 1 to intermediate part load, a schematic flow chart for the gas passage in an exhaust gas recirculation and charge air cooler having engine at low,

Fig. 2 is an illustration corresponding to FIG. 1, in the motor for higher full load and partial load,

Carried Fig. 3 is a representation corresponding to FIG. 1, that for an engine under low to medium load part, in which the removal of the exhaust gas system for an exhaust purifier,

Fig. 4 is a view corresponding to Fig. 3 in a motor for higher full load and partial load,

Fig. 5 is an illustration corresponding to FIG. 1, that for an engine under low to medium load part, in which also the recirculated exhaust gas can be compressed,

Fig. 6 is an illustration corresponding to FIG. 5, in a motor for higher full load and partial load,

Fig. 7 is a representation corresponding to FIG. 5, that is, for an engine under low to medium partial load, in which the removal of the exhaust gas takes place after an exhaust gas cleaning system and in which the recirculated gas can also be compressed, and

Fig. 8 is a representation corresponding to FIG. 7, with an engine for full load and higher part load.

Ways of Carrying Out the Invention

In the drawing, an engine 10 with exhaust gas turbocharging is shown schematically. The exhaust gas turbocharger is representative of any type of charging, such as. B. mechanical charging, charging with Comprex and vibrating tube and / or sonorous charging. For this purpose, the exhaust line 14 leading away from the engine 10 or its, for example, four cylinders 12 is connected to a turbocharger 16 . The exhaust gas line 14 can drive the exhaust gas turbine 18 of the turbocharger 16 . The air compressor 20 of the turbocharger 16 is connected in a rotationally fixed manner to the exhaust gas turbine 18 . As a result, the compressor 20 is driven when the turbine 18 rotates. The air 22 sucked into the compressor 20 is compressed and flows via a line 24 to a branch point 26 . There is a Umschaltven valve 28 available, which releases the charge air coming in line 24 from the compressor 20 either into a line 30 leading to an air cooler 32 , or the charge air from line 24 into a cooler 32 short-circuiting bypass line tion 34 releases.

A line 36 leads from the cooler 32 into a supply line 38 which leads into the engine 10 or its four cylinders 12 in the present example. The by pass line 34 opens into this supply line 38 at the point 40 .

An exhaust pipe 42 leads from the turbocharger 16 or from its exhaust gas turbine 18 via silencers and, if appropriate, via an exhaust gas cleaning system to the outside. The exhaust gas turbine 18 can be bypassed by the exhaust gas through a bypass duct 44 . In this bypass channel 44 there is a charge pressure control valve 46 (wastegate), via which the bypass channel 44 is opened or closed. The boost pressure control valve 46 opens, for example, when the inflow of exhaust gas into the turbocharger is to be protected to protect the turbocharger 16 when the load is too high or the engine speed is too high. In addition to the known protective effect of this bypass channel for the turbocharger 16 and the engine 10 can also be achieved by opening the charge pressure control valve 46 that charge air is not compressed. The heat generated by the compression process is avoided by the non-compression, so that there is no need to cool the charge air in order to get the heating up again. This makes sense for certain partial loads. In addition, the compressor 20 can be bypassed by the air 22 because of its back pressure via a bypass line 58 . This is by a switching element in the by-pass line 58 , z. B. valve 59 . The same effect can also be achieved by a compressor with variable geometry.

The charge air compressed by the turbocharger 16 is cooled in the cooler 32 . This device acting generally as a cooling device is an air cooler in the present example.

An exhaust gas recirculation line 54 also leads from the exhaust gas line 14 to the cooler 32 . The cooler 32 then preferably flows before either charge air flowing in from line 30 or exhaust gas flowing in from line 54 . Via an electrically controlled valve 56, for example, the amount of gas flowing through line 54 can be controlled. This valve 56 can also be opened or closed in a clocked manner. Characterized an arbitrary amount of exhaust gas from the engine 10 to the engine 10 per unit time can Coming be recirculated through the cooler 32 again.

In the full-load operation shown in FIG. 2 or operation with a higher partial load, the valves 56 , 59 are closed. The exhaust gas flowing away from the engine 10 flows into the exhaust line 42 via the turbine 18 . The compressor 20 driven by the turbine 18 ensures that the intake air 22 is charged. This charge air is pressed through line 24 to the cooler 32 and further through the supply line 38 into the engine 10 . The changeover valve 28 completely shuts off the bypass line 34 in this operating state.

The boost pressure control valve 46 present in the bypass channel 44 is used in this full-load operation or in operation with a higher partial load only to limit the maximum boost pressure and therefore also to protect the engine 10 . The boost pressure control valve 46 will therefore release the bypass channel 44 if, for. B. the speed or the boost pressure of the engine should be too high.

In part-load operation, which can be seen in the flow chart of FIG. 1, no charge air needs to be cooled. The turbocharger 16 can therefore be shut down. The exhaust gas flowing from the exhaust line 14 into the exhaust line 42 does not need to drive the turbocharger 16 , so that it can be passed around the turbine 18 through the bypass duct 44 . The boost pressure control valve 46 can therefore be in its bypass channel 44 opening opening position.

In this case, the intake air 22 is not compressed by the compressor 20 and therefore does not flow heated through the line 24 in the direction of the changeover valve 28 . The air flows bypassing the compressor 20 via the valve 59 through the bypass line 58 directly into the line 24 . The switching valve 28 closes the line 30 , since charge air does not need to be led to the cooler 32 and thus needs to be cooled, and opens the bypass line 34 . The charge air 34 then continues to flow through the feed line 38 into the engine 10 .

The exhaust gas branched off from the exhaust gas line 14 is passed through the line 54 , with the valve 56 in the correspondingly open position, through the cooler 32 and then continues to flow through the line 36 into the supply line 38 .

A check valve 60 can be present in line 36 , which prevents air flowing through line 34 from flowing backwards into line 36 and thus towards cooler 32 .

The system variants shown in FIGS . 3 and 4 differ from the flow diagrams shown in FIGS . 1 and 2 because the exhaust gas recirculation takes place downstream of a catalytic converter 62 . The corresponding exhaust gas recirculation line 54 therefore branches off from the exhaust line 42 after the catalyst 62 at point 64 . While in FIG. 4, similar to FIG. 2, full-load operation or operation at higher part-load is shown in terms of flow, in FIG. 3, similar to FIG. 1, the corresponding part-load operation is shown. An exhaust gas purification system is to be understood in general terms with the catalyst 62 shown in FIGS. 3 and 4. For example, in the case of a diesel unit, a soot filter could also be present either in place of the catalyst 62 or in combination with the same.

In order to ensure a sufficient pressure drop in the lines leading back to the engine 10 , a throttle valve 70 and 72 are provided in the exhaust line 42 and in the air line 24, respectively. In addition, the air recirculation or exhaust gas recirculation takes place in a corresponding manner, as described in connection with FIGS . 1 and 2; to this extent reference can be made to the above description parts.

When in Figs. 5 and 6, gas conduit for an engine 10, the possibility is given for a charging of the recirculated exhaust gases. Thus, the exhaust gas recirculation line 54 does not lead directly to a cooler, but first to the air compressor 20 . In this line 54 , a flow rate regulating valve 56 is also present. From the air compressor 20 then leads another exhaust gas recirculation line 74 to a precooler 76 and from there to the cooler 32nd In the present example, the precooler 76 , which may also not be present, is one of a z. B. liquid coolant flowing through heat exchanger. The cooling liquid 78 present in the heat exchanger 76 can also be used to cool the engine 10 . This precooler can also be provided in FIGS . 1 and 2 and 3 and 4.

The cooled gas flows from the pre-cooler 76 to the air cooler 32 , where it is further cooled. The air cooler 32 can be a conventional charge air cooler, which is exposed, for example, to the wind of a passenger car, for example, and which is therefore located in the immediate front region of the vehicle. The precooler 76 , on the other hand, can be attached to the vehicle at other locations that are not exposed to the wind.

The cooled gases continue to flow from the cooler 32 to an expansion valve 80 , which may be provided. Here, a further cooling effect is achieved by relaxing the gas. The expansion is particularly important when there are highly compressed gases and the gases in the air compressor 20 have been highly charged.

In full load operation or in operation under higher partial load ( FIG. 6) of the engine 10 , only the air to be introduced into the engine 10 is charged in the compressor 20 . The exhaust pipe 54 leading to the compressor is closed by valve 56 . The exhaust gases therefore escape exclusively from the gas line 14 into the open. In order to set the compressor 20 in rotation, the exhaust gas turbine 18 is set in rotation by the exhaust gases flowing through the line 14 . The charge pressure control valve 46 present in the bypass channel 44 is therefore closed.

The fresh air 22 flowing in from the outside flows through a switching valve 28 into a device 82 leading to the air compressor 20 . The switching valve 28 is switched so that it closes the inflow into the bypass line 34 , with which the two coolers 32 , 76 are bypassed. This applies to the above-mentioned full-load operation. By the precooler 76 pre scarf tetes changeover valve 86 in the return line 74 to precooler 76 the inflowing fresh air bypass line 84 can take place for the pre-cooler 76 in a rerouted and the air cooler 32 are fed so directly. This air flow is useful if the temperature of the air flowing through line 74 is lower than the temperature of the coolant 78 flowing through the precooler 76 . This prevents the fresh air from being heated in the pre-cooler 76 . The pre-cooler 76 is thus optionally used to cool the exhaust gases to be returned and, moreover, that fresh air whose temperature is higher than that of the pre-cooler 76 .

For low to medium partial load, the flow diagram of which is shown in FIG. 5, the changeover valve 28 is in a position closing the feed line 82 . The fresh air 22 therefore only flows into the bypass line 34 . For this purpose, exhaust gas to be returned flows through the inflow line 54 to the compressor 20 . The valve 56 is for this purpose in a correspondingly open position. The amount of exhaust gas not to be returned flows via the gas line 14 via the exhaust gas turbine 18 to a muffler and then further outside. This amount of exhaust gas drives the exhaust gas turbine 18 and thus also the air compressor 20 . As a result, the amount of exhaust gas to be recycled flowing through line 54 is compressed in air compressor 20 and then flows in the compressed state through line 74 to precooler 76 and further into cooler 32 . The bypass line 84 is closed for this purpose. The cooled, compressed exhaust gases are expanded in the expansion valve 80 and thereby further cooled.

Depending on the load level, the changeover valve 28 can assume any middle position, so that fresh air can flow into both the air compressor 20 and the bypass line 34 .

In the system variants shown in FIGS. 7 and 8, in contrast to the illustration according to FIGS . 5 and 6, there is an exhaust gas recirculation downstream of a catalytic converter 62 . In a similar manner as in FIGS. 3 and 4 branching off at a point 64 return line 54, the recirculated exhaust gases 20 performs flow-back to the Luftver closer to. Under full load operation ( Fig. 8) this Lei device 54 is closed by the valve 56 present in it, so that only fresh air from the compressor 20 is compressed and the downstream coolers 76 , 32 is supplied. Compare the remarks that the pre-cooler is bypassed by the fresh air at full load operation 76, if it is cooler than the Vorküh ler 76 regarding 6. Also here the Figs. 5 and.

At partial load ( FIG. 7), exhaust gas to be recycled is passed through line 54 to compressor 20 . There, the exhaust gas is compressed and then passed on to the cooling devices 76 , 32 . Here, too, a relaxation of the compressed gases and thus a further cooling of the same can be achieved by a downstream expansion valve 80 . In a corresponding manner, as shown in FIG. 5, the fresh air 22 is fed directly into the bypass line 34 . However, it is also possible, like the exhaust gas, to charge fresh air, at least partially, through the air compressor 20 . This charged fresh air would then be fed together with the charged exhaust gas through line 74 to cooler 32 or possibly first to cooler 76 and then to cooler 32 .

Otherwise, the statements made with reference to FIGS . 1 to 4 also apply to the flow plans shown in FIGS . 5 to 8. For example, appropriate throttle valves can be provided in the lines returning to the engine 10 to ensure a sufficient pressure drop.

While in Figs. 5, 6 and 7.8, the afferent into the compressor 20 lines 54, 82 combine to form a single line 88 can also both lines 54, 82 are supplied to the compressor 20 separately from each other instead.

Claims (19)

1. Internal combustion engine ( 10 ) with exhaust gas recirculation, charge air cooling and a cooler ( 32 ) for recirculated exhaust gases, characterized in that the air to be introduced into the combustion chamber is between zero and 100 percent either through this cooler ( 32 ) in the combustion chamber or bypassing ( 34 ) of the cooler ( 32 ) can be passed into the combustion chamber. 2. Internal combustion engine according to claim 1, characterized in that

• a bypass line ( 34 ) for the air to be introduced into the combustion chamber is bypassed by the cooler ( 32 ),
• - This bypass line ( 34 ) branches off from the air compressor ( 20 ) and cooler ( 32 ) existing charge air supply line ( 24 ) or from the air compressor ( 20 ) leading fresh air supply line ( 82 ).

3. Internal combustion engine according to claim 2, characterized in that

• - An air baffle ( 28 ) is present, with which in the charge air supply line ( 24 ) to the cooler ( 32 ) flowing charge air or in the fresh air supply line ( 82 ) to the air compressor ( 20 ) flowing fresh air between zero and 100 percent instead of the cooler ( 32 ) or the air compressor ( 20 ) directly into the bypass line ( 34 ) is redirectable.

4. Internal combustion engine according to one of the preceding claims, characterized in that the branch ( 64 ) to the cooler ( 32 ) or to the air compressor ( 20 ) returning exhaust gas supply line ( 54 ) is provided on the outflow side behind an exhaust gas cleaning system ( 62 ). 5. Internal combustion engine according to one of the preceding claims, characterized in that a device ( 56 ) for limiting the amount of exhaust gas to be recycled is present. 6. Internal combustion engine according to claim 5, characterized in that the device ( 56 ) for restricting the amount of exhaust gas to be returned is present in the exhaust gas line ( 54 ) returning to the cooler ( 32 ) or to the air compressor ( 20 ). 7. Internal combustion engine according to any one of the preceding claims, characterized in that a device ( 70 ) for throttling the amount of gas leaving the exhaust gas cleaning system ( 62 ) downstream of the branch ( 64 ) for the cooler ( 32 ) or the air compressor ( 20 ) returning exhaust gas line ( 54 ) is present. 8. Internal combustion engine according to one of the preceding claims, characterized in that a device ( 72 ) for throttling the air to be introduced into the combustion chamber is present. 9. Internal combustion engine according to claim 7 or 8, characterized in that the device ( 70 , 72 ) for throttling the amount of gas is a throttle valve. 10. Internal combustion engine according to claim 9, characterized in that the throttle valve is electrically controllable.   11. Internal combustion engine according to one of the preceding claims, characterized in that in the cooler ( 32 ) or to the air compressor ( 20 ) returning exhaust pipe ( 54 ) existing device for limiting the amount of exhaust gas is a cyclically ansteuerba res valve ( 56 ). 12. Internal combustion engine according to one of the preceding claims, characterized in that the exhaust gas turbine ( 18 ) bypass line ( 44 ) is present and the flow through this line ( 44 ) through a switching element ( 46 ) in terms of quantity between zero and 100 percent is. 13. Internal combustion engine according to one of the preceding claims, characterized in that the bypass line ( 58 ) bypassing the air compressor ( 20 ) is present and the flow through this line ( 58 ) by a switching element ( 59 ) can be limited in quantity between zero and 100 percent is. 14. Internal combustion engine according to one of the preceding claims, characterized in that a device ( 80 ) for relaxing the cooler ( 32 ) leaving gases is present. 15. Internal combustion engine according to claim 14, characterized in that the device ( 80 ) for relaxing in the cooler ( 32 ) leaving line ( 36 ) is present. 16. Internal combustion engine according to one of the preceding claims, characterized in that the cooler ( 32 ) is assigned a further cooler ( 76 ). 17. Internal combustion engine according to claim 16, characterized in that the further cooler is a pre-cooler ( 76 ). 18. Internal combustion engine according to claim 16 or 17, characterized in that the further cooler or the pre-cooler ( 76 ) is a heat exchanger which can be flowed through by the cooling water cooling the engine ( 78 ). 19. Internal combustion engine according to one of the preceding claims, characterized in that

• - A bypass line ( 84 ) bypassing the precooler ( 76 ) is present and
• - An air guide device ( 86 ) is provided, through which between zero to 100 percent of the gas flowing to the precooler ( 76 ) can be diverted into the bypass line ( 84 ).