DE60103047T2 - Apparatus for exhaust gas recirculation in an intake air flow - Google Patents

Description

Territory of invention

This invention relates to a device to return from Exhaust gas in an intake air stream in an internal combustion engine.

background the invention

A conventional air intake and exhaust gas recirculation arrangement includes a housing with an intake duct for Intake air, a throttle valve with a throttle valve, which in the Intake channel is arranged so that it is about a pivot axis between an opening and closed position is rotatable, and an exhaust gas recirculation line, connected to the intake duct downstream of the throttle valve stands to introduce exhaust gas into the air flow flowing through the intake duct.

There are several issues related with such an air intake and Exhaust gas recirculation arrangement on:

The exhaust gas should flow into the intake air so introduced be that it is evenly distributed to each engine cylinder. When a only intake point in the intake system between the throttle valve body and the inlet openings is used on the cylinder head, it is very important for good Ensure that the exhaust gas is mixed with the intake air.

The exhaust gas contains many combustion products and residual substances from the combustion chamber during the combustion process be dissipated. These components of the exhaust gas lead As is well known, deposits on the housing surfaces with which they come into contact. Deposits on the throttle valve housing pose a serious difficulty in that they become a The throttle valve can get stuck. With electronically controlled Throttle valves are also serious deposits Problem when they blocked the airflow past the throttle valve in the Can lock emergency operation. For engine safety concepts this is a serious problem.

When operating the internal combustion engine in a cold environment it is possible that is on the throttle valve body Ice forms. Ice forms when there is sufficient moisture in the intake air is present to condense and cool surfaces then turn into ice. Ice formation affects the air flow through the intake duct in a similar way Way as deposits and therefore affects the operation of the Internal combustion engine considerably. The throttle valve housing freezes then when the surfaces of the throttle valve body are cold and there is sufficient moisture in the intake air is. Moisture comes out of both inside the air distributor the exhaust gas as well as the gas flowing past in the crankcase.

If the air distributor is downstream of the Throttle body is made of plastic, it is necessary to withstand the thermal loads to be managed so that the plastic is not damaged. Introducing Exhaust gas in the intake air flow therefore poses a difficult problem on than the gases can be supplied at a temperature that above that for the plastic allowed Temperature. It is to avoid deposits in the exhaust gas recirculation circuit required to maintain a gas temperature above 350 ° C. Most air distributors made of plastic have a temperature limit of approximately 170 ° C. Therefore the exhaust gas should be introduced like this be that it is not the plastic air manifold damaged.

The following patent publications, who try to solve at least some of the problems outlined above, have become known:

EP 0 881 378 A3 describes a method for introducing exhaust gas in such a way that it is drawn into the air distributor downstream of the throttle valve housing through tangential openings. The tangential feed results in a spiral movement of the inflowing gas, which is intended to facilitate thorough mixing with the intake air.

US-A-4 697 569 describes a method for Introduce of exhaust gas on the throttle valve housing semicircular Ring openings to facilitate thorough mixing with the intake air.

US-A-4 461 150 describes a method for introducing exhaust gas into the air manifold downstream of the throttle valve housing through a number of symmetrically arranged, inclined inlets to form a spiral flow pattern in the air manifold. Similar to the one mentioned above EP 0 881 378 is said of such a spiral gas flow that it ensures a good mixing of inlet air and exhaust gas. In addition, such a spiral gas flow has the purpose of preventing the exhaust gas from coming into contact with the throttle valve housing. For this reason, the exhaust gas is fed into a region downstream of the throttle valve, in order not to be entrained into the backflow region in the “dead space” of the throttle valve.

DE 4 420 247 A1 describes a method for introducing exhaust gas into the air manifold downstream of the throttle valve housing through a plurality of openings arranged in a circular symmetrical pattern around the axis of the intake duct. This patent also discloses another embodiment in which the plurality of openings is replaced by a single annular opening. The intake duct includes a venturi section in the area into which the exhaust gas is introduced through the openings. Such a venturi section produces a higher flow rate of the intake air, which causes the intake air to mix and improve recirculated exhaust gas. This patent also speaks of thermal insulation between the throttle valve housing and the plastic air distributor in order to prevent damage to the air distributor.

Summary the invention

It is a primary object of this invention a device for recycling To create exhaust gas in an intake airflow at the deposits and ice formation on the surfaces of the throttle valve and adjacent walls of the intake duct are minimized become.

Another goal is for good Ensure mixing of intake air and recirculated exhaust gas.

Another goal is to heat the throttle valve body Optimize throttle valve.

The invention is in the claim 1 defined. Further developments and modifications of the invention are in the dependent claims Are defined.

According to the device of the In the present invention, the intake duct includes an elbow section between the throttle element of the throttle valve and an exhaust gas inlet, for the entry of exhaust gas into the return flow area downstream of the throttle element to prevent.

The manifold section of the present Invention enables It is to introduce exhaust gas in an area where there is no backflow of air. Rather, the exhaust gas is introduced into an area of the air flow that flows freely into the air distributor. Thereby, that exhaust the inner surfaces of the throttle valve body and the throttle element (the throttle valve) cannot touch, Is it possible, to prevent deposits from forming in this area. It also contains exhaust gas as is well known, great Amounts of moisture that are in contact with cold surfaces Ice formation leads. By preventing exhaust gas from contacting the surfaces of the throttle valve contact arrives, it is also possible to significantly increase the risk of ice formation to reduce.

The throttle element is preferably immediately adjacent an upstream end of the manifold section arranged so that the backflow area in the manifold section extends. Moreover the exhaust gas inlet is preferably immediately adjacent to one downstream end of the manifold section arranged. This offers the opportunity the inflowing name is Exhaust with cooler Intake air as soon as possible Mix downstream of the throttle valve so that the mixing time is maximized and thereby the heat of the exhaust gas is well distributed before it reaches the inner surfaces of the Air distributor reached. It was calculated that for an exhaust gas at 350 ° C (highest expected temperature), which in an intake air flow of 40 ° C (highest to expected ambient air) in a mass fraction of 30% exhaust gas (largest amount to be expected of the exhaust gas) occurs, assuming the total end temperature perfect mixing 170 ° C would be. Is 170 ° C the maximum temperature that a typical plastic air distributor can withstand can. In that the manifold section as close as possible arranged on the throttle valve and the gas is introduced so that mixing is maximized, it ensures that Exhaust gas cannot damage a plastic air distributor.

According to another training the invention provides that the manifold section from a separate housing part exists between the throttle valve housing and the air distributor is. The housing parts are preferably of the manifold section and the throttle valve body connected so that there is an optimal heat transfer comes between them. Thus, heat from the exhaust gas is used to the housing part of the manifold section heat, what warmth to the throttle valve body emits to raise its temperature.

As mentioned above, it is believed that the Moisture present in the exhaust gas is the main cause of icing of the surfaces of the throttle valve body is. It is therefore intended to heat the throttle body only to feed if she needed becomes. The thermal inertia of the elbow section and the throttle valve body should be minimized so that they are as soon as necessary heated can be to prevent ice formation. The level to which the temperature of the throttle valve body must be carefully checked, to make sure it's not too high. This could be due to the use of an appropriate CFD analysis.

The optimal heat transfer connection of the housing part of the manifold section with the throttle valve body is provided to the warming of the throttle valve body to optimize, and not so much to the temperature of the housing part of the manifold section to reduce. Another consequence of this optimal heat transfer and minimal thermal inertia, that in a hot soak condition the throttle valve housing with the greatest possible Speed depending can cool down from the ambient temperature.

In summary, the present invention and their further training on the following advantages:

The manifold section between the Throttle element and the air distributor serves to introduce the exhaust gas in such a way that it is not in the air backflow area arrives downstream of the throttling element to form deposits and ice to prevent.

The body part of the manifold section is connected to the throttle valve body in such a way that heat is transferred from the exhaust gas to the throttle valve body to prevent ice formation.

The housing part of the manifold section and the throttle valve body have the lowest possible Inertia to the hot soak temperature and the time to warm the throttle body reduce.

The exhaust gas is in the intake air flow introduced so that the temperature of the exhaust gas during mixing with fresh intake air is mixed sufficiently so that it is too no damage an air distributor made of plastic.

Short description of the drawings

These and other goals, characteristics and advantages of this invention will appear from the following detailed Description of the preferred embodiment and the best embodiment, the attached claims and attached Drawings in which:

1 Figure 3 is a schematic sectional view of an intake duct of the present invention;

2 is a schematic sectional view in the direction of arrows II-II in 1 is.

detailed Description of the preferred embodiment

According to 1 is an air intake duct 2 provided to supply intake air to a plurality of cylinders of an internal combustion engine (not shown). The intake duct 2 has a throttle valve housing 4 and a manifold section 6 on that with an air manifold 8th connected is.

The throttle valve body 4 contains a throttle element 10 , In the illustrated embodiment, the throttle valve 10 a conventional throttle valve that is about an axis 11 is rotatable between an open and closed position in order to control the flow rate of the air intake flow.

An exhaust gas recirculation line 12 that receives exhaust gas from an exhaust system (not shown) of the internal combustion engine ends in an exhaust gas inlet 14 , the exhaust gas into the intake duct 2 introduces to mix it with the inlet stream.

In operation, intake air flows through the intake duct 2 on the throttle element 10 past. This results in an air backflow area 16 downstream of the throttle element 10 whose extent depends on the angular position of the throttle element 10 depends.

As explained above, the manifold section 6 , which is a 90 ° elbow, uses the exhaust gas introduced into the intake air flow to the return flow area 16 not reached. Regardless, the exhaust gas in the intake airflow becomes as close as possible to the throttle member 10 and the backflow area 16 introduced to ensure a good mixing of intake air and exhaust gas.

In particular, the throttle element 10 immediately adjacent to the upstream end of the manifold section 6 arranged so that the backflow area 16 inside the manifold section 6 extends. In addition, the exhaust gas inlet 14 immediately adjacent to the downstream end 24 (indicated by dashed lines) of the manifold section 6 arranged.

As in 2 shown, there is the exhaust gas inlet 14 from a single opening that is arranged so that the exhaust gas in the intake duct tangential to the peripheral wall 20 of the intake duct is inserted in order for a spiral flow 22 of the exhaust gas. The tangential entry of the exhaust gas helps to ensure that the exhaust gas does not go up into the "neck" of the manifold section into the backflow area 16 emigrated. It is also important to note that the exhaust gas inlet 14 introduces the exhaust gas at a point where the intake air flow is unimpeded, such as by arrows 18 is indicated.

If only the throttle valve housing 4 and the manifold section 6 could be formed in one piece, they are preferably made from separate housing parts. The body part of the manifold section 6 is with the exhaust gas inlet 14 provided so that the exhaust gas for heating the manifold section 6 is used. The manifold section 6 is with the throttle valve body 4 through flanges 26 connected to ensure good heat transfer between them. The throttle valve body 4 and the manifold section 6 are made of a metal with low thermal inertia, preferably cast aluminum. To heat transfer between the manifold section 6 and the throttle valve body 4 could improve thermally conductive sealants (not shown) within the flanges 26 be provided.

As a result of this construction, heat from the exhaust gas is rapidly supplied to the throttle valve body 4 released to prevent ice formation. In addition, the throttle valve body 4 cool down at the highest possible speed in hot soak conditions.

As in 1 shown is the manifold section 6 with the air distributor 8th through flanges 28 connected. The air distributor is preferably present 8th made of plastic. The flanges 28 could be designed to provide thermal insulation between the air manifold and the body portion of the manifold section 6 to care. In any case, the arrangement shown includes the throttle valve housing 4 , the manifold section 6 and the exhaust gas inlet 14 for a good mixing of fresh intake air and exhaust gas in order to damage the air distributor 8th to avoid.

Claims (10)

Device for returning exhaust gas into an intake air flow in an internal combustion engine, with an intake duct ( 2 ) for supplying intake air to an air distributor (8), a throttle valve with a throttle element ( 10 ) in the intake duct ( 2 ) is arranged in such a way that it can be moved between an open and a closed position, with a backflow area () 16 ) downstream of the throttle element ( 10 ) is present, and an exhaust gas recirculation line ( 12 ), the exhaust gas in the intake duct ( 2 ) through an exhaust gas inlet ( 14 ) downstream of the throttle element ( 10 ), characterized in that the intake duct ( 2 ) a manifold section ( 6 ) between the throttle element ( 10 ) and the exhaust gas inlet ( 14 ) has the entry of exhaust gas into the backflow area ( 16 ) to prevent. The device of claim 1, wherein the manifold section ( 6 ) has a 90 ° elbow. Apparatus according to claim 1 or 2, wherein the throttle member ( 10 ) immediately adjacent to an upstream end of the manifold section ( 6 ) is arranged so that the backflow area ( 16 ) in the manifold section ( 6 ) extends. Device according to one of claims 1 to 3, wherein the exhaust gas inlet ( 14 ) immediately adjacent to a downstream end of the manifold section ( 6 ) is arranged. Device according to one of the preceding claims, in which the exhaust gas inlet ( 14 ) is an inlet with a single opening. Apparatus according to claim 5, wherein the exhaust gas inlet ( 14 ) is arranged so that it exhausts the exhaust gas ( 2 ) tangential to a peripheral wall ( 20 ) of the intake duct ( 2 ) introduces a spiral exhaust gas flow ( 22 ) to create. Device according to one of the preceding claims, in which the elbow section ( 6 ) consists of a separate housing part, which is between a throttle valve housing ( 4 ) and an air distributor ( 8th ) is used. Apparatus according to claim 7, wherein the exhaust gas inlet ( 14 ) in the housing part of the manifold section ( 6 ) is arranged. Apparatus according to claim 8, wherein the housing part of the elbow section ( 6 ) and the throttle valve housing ( 4 ) are connected to each other in such a way that optimal heat transfer between them occurs. Apparatus according to claim 8 or 9, wherein the housing part of the elbow section ( 6 ) and the throttle valve housing ( 4 ) have minimal thermal inertia.