DE3225867A1 - Internal combustion engine with an exhaust turbocharger - Google Patents

Abstract

In an internal combustion engine with an exhaust turbocharger, a bypass line is provided between the intake pipe connected to the charger and situated downstream of the throttle valve and the exhaust pipe opening into the turbine. Arranged in the bypass line is a valve which shuts off the bypass line only when the exhaust gas pressure in the exhaust pipe exceeds the charging pressure in the intake pipe by a certain amount and a connection is having a disadvantageous effect on the performance of the internal combustion engine. Below this pressure range, the valve is open and the connection between the intake pipe and the exhaust pipe is free. In the operating condition of the internal combustion engine in which the charging pressure is higher than the exhaust gas pressure, it is thereby possible for fresh gas from the intake pipe to pass into the exhaust pipe and for automatic supplying of secondary air to take place. If, on the other hand, the exhaust gas pressure is higher than the charging pressure, exhaust gas flows across from the exhaust pipe into the intake pipe, automatic exhaust gas recirculation thus taking place.

Description

Internal combustion engine with an exhaust gas turbocharger

The invention relates to an internal combustion engine an exhaust gas turbocharger according to the preamble of the claim 1.

From DE-PS 29 29 419, for example, is such a Internal combustion engine known in which between the inlet the turbine and the outlet of the supercharger a bypass line runs. A valve is arranged in the bypass line, which has a control chamber which is connected to the exhaust line of the internal combustion engine leading to the turbine is. When exposed to in the outlet line The resulting negative pressure opens the valve, which causes the negative pressure generated after a sudden release of the accelerator in this exhaust line of the internal combustion engine through the downstream of the outlet of the supercharger resulting overpressure is reduced via the bypass line and the outlet line the internal combustion engine or the inlet of the turbine is supplied. By this measure, the speed of the Turbocharger are retained so that the boost pressure at a renewed acceleration can take effect again fully and without delay. The one when the valve opens The onset of a current only takes place in this arrangement one direction, from the inlet line to the outlet line of the internal combustion engine instead, with a check valve arranged in the bypass line causing a backflow of exhaust gases to the valve and into the inlet pipe.

From DE-OS 28 23 067, however, it is known about a Bypass line a flow in the opposite direction, so an exhaust gas recirculation from the outlet line to the inlet line to enable the internal combustion engine. In this Fall prevents one arranged in the bypass line

Check valve an inflow of charge air ·> η the ■ from 1 aß 1 ei tion.

The invention is based on the object of an internal combustion engine to create according to the preamble of the patent claim, in which with simple means via the bypass Line both an exhaust gas supply in the inlet line as a supply of fresh air to the outlet pipe is also possible is.

The object is achieved by the features of the identifier Iq of claim 1.

By the proposed arrangement of a bypass line with a valve, which the bypass line only then Shuts off when the exhaust pressure exceeds the boost pressure by a certain amount, is below this pressure range the valve is open and thus the connection between the inlet line and the outlet line is released. if in this open position of the valve, the boost pressure prevailing downstream of the throttle valve is higher than the exhaust pressure, as shown, for example, in the lower rotary ; 20 number range of the internal combustion engine up to the control

of the usually existing exhaust gas relief valve

; Case is, so fresh gas can from the inlet line in

j step over the outlet pipe. With the resulting Secondary air supply, it is possible to promote the post-combustion: 25 of the exhaust gases and the harmful ones

■ To reduce components in the exhaust gas. When the exhaust pressure

when the valve is open, however, it is higher than the boost pressure prevailing downstream of the throttle valve, such as this for example at higher speeds and at higher speeds Performance range as well as in the acceleration phase of the Internal combustion engine is the case, exhaust gas occurs

the outlet line into the inlet line. Through this In particular, exhaust gas recirculation can be adjusted here the nitrogen oxide values contained in the exhaust gas are reduced. This in both directions taking advantage of the the pressure gradient prevailing in each case automatically Any gas exchange taking place thus comes into operation come about, in which an improvement in the exhaust gas values is desired anyway However, boost pressure exceeds significantly, as is the case in the higher load range, and reaches a value from which an exhaust gas recirculation is disadvantageous affect the performance of the internal combustion engine the valve is shut off and the connection is interrupted.

In order to delimit the gas exchange between the inlet line and the outlet line, the valve is therefore designed in such a way that it is shut off from an exhaust gas pressure which is approximately 5% above the boost pressure.

In order to avoid an amount of exhaust gas through the bypass line which can overflow the ignitability of the Gas in the internal combustion engine is impaired provided that the bypass line in that of the valve released state in which a connection is established between the supercharger outlet and the turbine inlet is, has such a flow cross-section that the maximum amount of exhaust gas from the outlet pipe is recyclable into the inlet line. The flow cross-section is designed differently depending on the size of the internal combustion engine, but expedient dimensioned so that, on the one hand, the amount of exhaust gas recirculated at most about 30% of that supplied to the internal combustion engine or reached by this sucked in combustion gas.

On the other hand, the flow cross-section is both large enough as the flow resistance is so low as to with a flow in the other direction one is sufficient de secondary air supply.

The valve can be designed so that it has a having a valve seat cooperating valve body, which by a spring in the sense of a release of the Bypass line is acted upon and with a membrane is connected, which delimits a control chamber, which is shut off via a line in one when it is acted upon the bypass line inducing sense with the Outlet line is connected.

For the purpose of a reliable function, the spring arranged in the valve can have a tension force which can be overcome at a pressure in the control chamber connected to the outlet line of more than 5% above the boost pressure.

An embodiment of the invention is described below described in more detail with reference to the drawing. It shows:

1 shows an internal combustion engine with an exhaust gas turbocharger and one between the charger outlet and the turbine inlet running bypass line in a schematic representation,

2 shows a simplified one arranged in the bypass line illustrated valve,

Fig. 3 is a diagram from which the pressure in the inlet line and in the outlet line against the Speed of the internal combustion engine is evident, and

Fig. 4 is a _Diagramrr} from the eggs pressure in oer intake pipe and in the AusTaßleitung from the average working pressure of the internal combustion engine can be seen.

The schematic illustration in FIG. 1 shows an internal combustion engine 1 with an exhaust gas turbocharger, or is formed in the usual way by a turbine 3 and a charger 4. The outlet 5 of the supercharger 4 is connected to the inlet line 6 and the inlet 7 of the turbine 3 is connected to the outlet line 8 of the internal combustion engine 1. The turbine 3 has a bypass line 9 with a blow-off valve 10 known per se, which releases the bypass line 9 to limit the boost pressure or, in the event of an exhaust gas jam in the outlet line 8, to relieve the turbine 3. The inlet line 6 and the outlet line 8 are connected to one another via a bypass line 11 which, downstream of one in the inlet! Aßl eiturvg 6 arranged throttle valve 12 is connected to the inlet line 6. In the bypass line 11, a valve is arranged through which the connection is released in the event of low pressure differences between the inlet line 6 and the outlet line 8 and thereby either automatic exhaust gas recirculation or secondary air supply is possible. However, if the exhaust gas pressure in the outlet line 8 exceeds the boost pressure in the inlet line 6 by a certain amount, the valve 13 is shut off. For this purpose, the valve 13 is connected via a line 14 to the exhaust gas line 8, via which the valve is actuated under the effect of the exhaust gas pressure.

In Fig. 2, the valve 13 is shown in simplified form, which, for example, two by a membrane 15 from each other has separate chambers 16 and 17, the first chamber 16 via line 14 to the exhaust gas

line 8 is connected, while the second chamber 17 via an opening 18, for example with the atmosphere communicates. The membrane 15 is connected in its center to a valve body 19, which is shown in FIG Position with the face of his valve! 1er 20 on a valve seat 21 rests in a sealing manner and the line 11 shuts off. In the chamber 17 there is one attached to the membrane 15 supporting compression spring 22 arranged, which strives is to lift the valve body 19 from the valve seat 21 and in the dashed line, a release of the bypass line 11 Bringing a provocative position.

In the case of a selected internal combustion engine, the shut-off position of the valve 13 comes about when an exhaust gas pressure in the chamber 16 ″ becomes effective via the line 14 connected to the outlet line 8 which exceeds the boost pressure in the inlet line 6 by about 5% and, for example, 1.4 bar, ie a pressure which occurs from about 50% full load. The tensioning force of the spring 22 is therefore designed so that it allows the valve to be shut off from such an operating state is, depending on the prevailing operating state, a secondary air supply can take place at a higher pressure in the inlet line 6 or an exhaust gas recirculation at a higher pressure in the outlet line 8. In the released state, the valve 13 or the bypass line 11 have a flow cross-section which a recirculation of exhaust gas of at most 30 % of the combustion gas supplied via the inlet line 6 z l leaves in order not to impair the performance of the internal combustion engine. The required diameter of the bypass line 11 is, for example, about 5-8 mm, which at the same time ensures that a sufficient secondary air supply can take place.

In a modification of the output Ii hru η α s £. Ei 5 ρ ie 1 s according to FIG. 2, the rammer 17 can also be connected to the inlet line 6 via the opening 18 but also downstream oer throttle valve 12, so the boost pressure in the chamber 17 effective and the valve 13 is actuated depending on the differential pressure rrit the same result. In this case the spring must be matched to 22, however, such a clamping force to be überwindber also at a pressure in the outlet conduit connected to the control chamber 16 S of more than IQ, 5% de ir. Laue pressure.

The diagram shown in Fig. 3 shows the pressure curve resulting in the above embodiment in the inlet line 6 and in the outlet line 8 based on the speed of the internal combustion engine when the internal combustion engine is operated at full load. The speed of the internal combustion engine is plotted on the abscissa η and the absolute pressure in bar on the ordinate P, while the pressure in the outlet line 8 from the course of our line P3 and the pressure in the inlet line 6 downstream ^{from the course of the line P2 1} the throttle valve 12 is apparent. Accordingly, the pressure P2 ¹ in the inlet line 6 rises faster than the pressure P3 in the outlet line 8, which is due to the efficiency of the exhaust gas turbocharger and its delivery characteristics in this operating state.

When the boost pressure has reached a pressure of, for example, 1.7 bar in coordination with the power requirement and the mechanical load capacity of the internal combustion engine, the relief valve 10 (FIG. 1) opens, for example, as a function of the boost pressure. As a result of this boost pressure limitation, the pressure P2 ¹ largely remains at this level, as is shown by the approximately horizontal course of the line. On the other hand, the pressure P3 increases

ίο -

continues to rise, finally exceeds the pressure P2 ¹ with increasing speed η of the internal combustion engine and takes on a flatter curve due to the open relief valve. From this pressure curve it can be seen that in an operating state of the internal combustion engine which lies within the triangle marked by hatching, fresh gas can pass from the inlet line into the outlet line.

In the diagram shown in FIG. C , the pressure curve in the inlet line 6 and in the outlet line 8, which is related to the mean working pressure of the internal combustion engine, is illustrated. The abscissa pe represents the mean working pressure and the ordinate P the absolute pressure in bar, with overpressure above the horizontal line marked with 1.0 bar and negative pressure below this line. From the line P3 the pressure curve in the outlet line 8 and from the line P2 ¹ the pressure curve in the inlet line 6 can be seen. ^{Accordingly, the pressure P2 1} prevailing in the inlet line 6 is in the negative pressure range and rises steadily with increasing mean pressure, while the pressure P 3, starting from a pressure above 1 bar in the outlet line 8, assumes a flatter pressure. From this illustration it can be seen that in an operating state of the internal combustion engine which lies within the triangle illustrated by hatching, exhaust gas can pass from the outlet line 8 into the inlet line 6.

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Claims (5)

240 / £ Z AUDI KSU AUTO UNION AKTIENGESELLSCHAFT, NeckarsuIm / Württ Internal combustion engine with an exhaust gas turbocharger Claims ! ./ 'Internal combustion engine with an exhaust gas turbocharger whose Supercharger outlet with the inlet line having a throttle valve and whose turbine inlet is connected to the exhaust line of the internal combustion engine, with a B'Dass line between the charger outlet and the turbine inlet, characterized in that the bypass line (11) is downstream of the throttle valve (12) is connected to the inlet line (6) and a valve (13) which the bypass line (11) only shuts off when the exhaust gas pressure in the outlet line (8) increases the boost pressure in the inlet line (6) exceeds a certain level. 37758R7 2. Internal combustion engine according to claim 1, characterized in that the valve (13) is shut off from an exhaust gas pressure which is approximately 5% above the boost pressure. 3. Internal combustion engine according to claim 1, characterized indicates that the bypass line (11) in the valve (13) released state in which a connection between the charger outlet (5) and the turbine inlet (7) is made, has such a flow cross-section that the maximum amount of waste gas from the Outlet line (S) can be returned to the inlet line (6) is. 4. Internal combustion engine according to claims 1 and 2, characterized characterized in that the valve (13) has a valve body (19) cooperating with a valve seat (21), which is acted upon by a spring (22) in the sense of a release of the bypass line (11) and with a Membrane (15) is connected, which delimits a control chamber (16) which via a line (14) in one at Acting on a shut-off of the bypass line (11) inducing sense connected to the outlet line (S) is. 5. Internal combustion engine according to one of claims 2 to 4, characterized in that the spring (22) has a tension force which can be overcome at a pressure in the control chamber (16) connected to the outlet line (8) of more than 5 % above the boost pressure is.