DE10127392A1 - Diesel engine turbocharging system comprises a switching valve adjusting waste gate to charging air pressure against rev count for controlled exhaust line feed - Google Patents

Abstract

The charging pressure (p) is matched to the engine torque against rev count by the waste gate (9). The current charging air pressure ( pi ) is compared with an ideal pressure ( theta ) in the control unit (16) against rev count (n) to give a correction signal(s) used to directly or indirectly actuate the waste gate (9). Waste gate (9) is linked by air line (13) to the charging air line (5) and air line pressure can be modified by control (16) linked by valve operation as a function of charging air pressure versus rev count. The switcher unit (20) to transfer charging air to exhaust has a controller (21) switched in parallel to the exhaust return device.

Description

The invention relates to a method for operating an internal combustion engine, in particular a diesel internal combustion engine with an exhaust gas turbocharger a turbine part arranged in an exhaust pipe and one in a drawer Air line arranged compressor part, being upstream of the turbine part a blow-off valve is arranged in the exhaust pipe, as well as with a blow-by Device for the controlled transfer of compressed charge air from the drawer Air line to the exhaust line, especially at low speeds the blowing device a controlled transfer of compressed charge air to Exhaust pipe is carried out.

The invention further relates to an internal combustion engine, in particular a diesel engine. Internal combustion engine, with an exhaust gas turbocharger with one in an exhaust pipe arranged turbine part and a arranged in the charge air line Ver sealing part, being upstream of the turbine part in the exhaust pipe Blow-off valve is arranged, and a blow-off device for controlled Transfer of compressor charge air from the charge air line to the exhaust line.

It is known to circulate a portion of the air compressed by the compressor Direct the internal combustion engine around directly into the exhaust gas flow in front of the turbine, to increase the efficiency of the exhaust gas turbocharger in certain operating areas increase. The blow-off quantity can be adjusted accordingly via a blow-off valve the requirements in the engine map can be set variably. The DE 32 25 867 A1, for example, shows an internal combustion engine at the outlet The pipe and inlet pipe are connected to one another via such a blow-by pipe they are.

The volume flow through the ver be increased more densely. The direct and desired consequence is moving away from the surge limit of the compressor. This principle is Internal combustion engines applied. For operating state-dependent control However, relatively complex measures must be taken so that the Engine operating behavior or driveability not undesirable, both is influenced in stationary as well as in transient operating states.

Blow-off valves are increasingly used in modern vehicle internal combustion engines - so-called waste gates - used to keep the boost pressure at full load increasing engine speed not to increase excessively. Thereby there is an increase in the pressure upstream of the turbine above the pressure of the La  exhales after the compressor. In the lower engine speed range close to full load however, the boost pressure after the compressor is higher than the exhaust pressure before the turbine.

To simplify the blow-off device, DE 32 44 928 A1 Internal combustion engine proposed to blow-off valve and blow-off valve too a combined device are combined. However, this is also a relative one complex control of the blow-around required.

AT 002 540 U1 is an internal combustion engine with an exhaust gas feedback device integrated blowing device known. This can help A blow-around can be achieved as simply as possible.

EP 0 685 638 A2 describes a turbocharger management system with one Blow-off valve and a blow-off valve, which depending on the speed, the load, the ambient temperature and the ambient pressure. At low speed, a controlled is carried out via the blowing device Transfer of compressed charge air to the exhaust pipe.

Internal combustion engines with exhaust gas turbocharging are designed for a specific geo designed height. If the internal combustion engine at other geodesics operating heights than at design height, the operating conditions change conditions for the exhaust gas turbocharger, which makes its operating point in operation map is moved. With the altitude, i.e. with falling ambient air pressure, the operating points of the exhaust gas turbocharger move towards higher Boost pressure ratio, depending on the basic design safe operating limits would be exceeded if a reduction in performance was not previously proposed is taken. Overall, however, the boost pressure before the internal combustion engine increases shine with the height, whereby the air mass flow through the internal combustion engine machine and thus the excess air is negatively influenced.

The operating limits mentioned can be:

• 1.charger surge limit at low engine speeds,
• 2. Speed limit of the charger at nominal speed,
• 3. exhaust gas temperature in front of the turbine,
• 4. soot emissions.

It is the goal of every engine manufacturer to increase the geodetic height to that it is not yet necessary to reduce the power to go as far up as possible ben. Usually at altitudes above 1500 to 2000 meters above sea level  the performance of the internal combustion engine is reduced. For a certain performance the user must therefore purchase a larger motor than at nied higher heights would be necessary.

The object of the invention is to avoid this disadvantage and as far as possible simple way to reduce the height-related performance reduction or Relocate power reduction to greater heights.

According to the invention, this is done in that the boost pressure curve by means of the Blow-off valves over the speed to the torque curve of the internal combustion engine machine is adjusted, the actual boost pressure with one in a tax Unit stored target boost pressure curve compared to the speed and off the comparison, a correction signal is generated with which the relief valve is operated directly or indirectly. With the well-known technique of blowing lower engine speeds will be the operating point of the compressor in its Map shifted to the right, causing it to move away from the surge limit moved. The adjustment of the boost pressure curve to the geodetic height allows it, the otherwise occurring decrease in the boost pressure upstream of the internal combustion engine largely to compensate, whereby both the exhaust gas temperature, as well as the Soot emissions remain unaffected. It is preferably provided that the controlled transfer of compressed charge air to the exhaust pipe depending ambient pressure is carried out. This enables through the Combination of blowing with a fully flexible boost pressure control the Leis installation reduction to greater heights, without the need for safe operating limits zen are exceeded.

To carry out the method, it is provided that the relief valve in Ab Dependency of the boost pressure is actuated, the boost pressure curve over the Speed to the torque curve of the internal combustion engine and preferably is adaptable to the changed ambient pressure. The relief valve is in front preferably connected via an air line to the charge air line, the Pressure in the air line via an electronic control unit in Ab Dependency of the charge air pressure and the engine speed actuable control valve is changeable. The relief valve is either direct, for example electro actuated magnetically or indirectly via an actuator. The actuator consists of for example from a pneumatic box, which draws its auxiliary energy from the charging unit pressure related. The auxiliary energy can also come from a compressed air system of the vehicle, for example an air brake system, or to be electrical. It is preferably provided that the relief valve indirectly via an air line connected to the blow-off valve preferably arranged between the charge air line and relief valve, and with the Control unit connected control valve is actuated. The control valve is at  arranged for example between the charge air line and relief valve. alternative but it can also be provided that the control valve in one with the Air line connected ventilation line is arranged. Is the compressed one If the auxiliary energy is air, the available pressure is determined by the electri cal control valve modulated so that the actuator meets the requirements is moved accordingly. If an electrical actuator is used as an actuator, so can be controlled directly by the engine electronics.

In a simple embodiment of the invention it is provided that the Blow-around device is integrated in an exhaust gas recirculation device. The umbla The device advantageously has a blow-by control device, which in terms of circuitry parallel to an exhaust gas recirculation control device the exhaust gas recirculation device is arranged. The blow-by control device consists of a blow-off control valve and one in the direction of the exhaust pipe opening blow-by check valve. The exhaust gas recirculation control device has an exhaust gas check valve, and preferably an exhaust gas recirculation control valve on. Air blow check valve and exhaust gas check valve are anti arranged parallel to each other.

The blow-around control valve and / or the exhaust gas recirculation control valve can be in one simple design can be formed by a control flap. In addition or at place of the control valve (s) can be provided that in the exhaust gas recirculation tion or in a line common for exhaust gas recirculation and blow-by a three-way valve is provided, which either the exhaust gas recirculation or the blowing is activated.

The blow-by control device is expedient - in the blow-by direction considered - arranged in front of an exhaust gas recirculation cooler.

The invention is explained in more detail below with reference to the figures. Show it

Fig. 1 to 3 schematics of the invention Brennkraftma machines in three different variants,

Fig. 4 is a diagram in which torque and boost pressure is plotted against the speed and

Fig. 5 shows a compressor map of the exhaust gas turbocharger.

1 to 3 schematically each show a diesel internal combustion engine 1 with an inlet system 2 and an outlet system 3 , and an exhaust gas turbola of FIG. 4 . The exhaust gas turbocharger 4 has a compressor part 6 arranged in the charge air line 5 and a turbine part 8 arranged in the exhaust line 7 .

A blow-off valve 9 , which is actuated pneumatically via a can 10 , is arranged upstream of the turbine part 8 in the exhaust gas line 7 . By pressurizing the can 10 , the relief valve 9 is opened via a membrane 11 against a return spring 12 . Exhaust gas is directed past the turbine part 8 by opening the relief valve 9 .

The pressure cell 10 is connected via an air line 13 to the charge air line 5 in connection, a control valve 14 being arranged in the air line 13 ( FIGS. 1 and 3). Between the control valve 14 and the charge air line 5 , a throttle 15 is provided in the embodiment from FIG. 1. This control valve 14 can also be arranged as a one-way valve in a vent line 13 c downstream of the throttle 15 ( FIG. 2). Another advantageous arrangement of the control valve 14 in one-way form is possible by interchanging the positions of throttle 15 and one-way valve ( Fig. 3). In this case, a particularly rapid system reaction for rapid boost pressure build-up in connection with a reduction in air consumption can be achieved, since the control valve 14 remains closed when no exhaust gas is blown off. The control valve 14 is actuated via an electronic control unit 16 . Via a pressure signal line 17 , the electronic control unit 16 receives signals from a pressure sensor 17 a via the charge air pressure p in the charge air line 5 . Furthermore, the electronic control unit 16 is connected via a speed signal line 18 to a speed sensor 19 and receives data on the respective engine speed n.

The setpoint boost pressure curve is stored in the electronic control unit 16 over the speed.

The electronic control unit 16 determines the desired value for the boost pressure p _s from the current engine speed n. From the comparison of the desired boost pressure p _s with the actual boost pressure p _i received via the pressure signal line 17 , the control unit 16 determines a correction signal s, which is supplied to the control valve 14 as a manipulated variable, whereupon the control valve 14 opens accordingly. The relief valve 9 is opened by the charge air pressure p thus applied to the can 10 via the throttle 15 . The charge air pressure p thus serves as auxiliary energy for the actuation of the relief valve 9 . The available pressure is modulated via the electric control valve 14 so that the relief valve 9 is moved accordingly.

Instead of the charge air pressure p via the air sub-line 13 a, the auxiliary energy for the air line 13 can also be obtained from the air-braking system of the vehicle, as is arranged in FIGS . 1 to 3 by dashed lines 13 b. It is also conceivable that the relief valve 9 is moved via an electrical actuator. If an electric actuator is used as an actuator, it can be controlled directly by the engine electronics.

As can be seen in FIG. 4, the course of the boost pressure p over the speed n is largely adapted to the course of the torque M. For comparison, the constant course of the boost pressure p _{k is} indicated by dashed lines, as was previously the case with known diesel internal combustion engines. In comparison to the invention, the dashed constant boost pressure curve from a preset blow-off point A has the disadvantage that with increasing engine speed from the point with the maximum torque, the mass emission is unnecessarily high. By adjusting the boost pressure p over the speed n to the torque curve, there is a significant improvement in the emission load, both at full load and with a decreasing load up to that point A in Fig. 4, at which the natural boost pressure of the exhaust gas turbocharger closed relief valve is no longer above the desired boost pressure.

Between the exhaust pipe 7 and the charge air line 5 , a Umblaseeinrich device 20 with a blow-by control device 21 is provided in a blow-by line 22 . Compressed charge air can be transferred from the charge air line 5 to the exhaust gas line 7 in a controlled manner via this blow-off device 20 .

In FIGS. 2 and 3, the Umblasevorrichtung 20 is processing in a Abgasrückführvorrich 30 integrated. The exhaust gas recirculation device 30 has an exhaust gas recirculation control device 31 arranged in an exhaust gas recirculation line 32 , which consists of an exhaust gas recirculation control member 33 and an exhaust gas return valve 34 . The exhaust gas recirculation line 32 opens into the charge air line 5 via a venturi device 35 . The venturi device 35 enables exhaust gas recirculation even with an unfavorable pressure difference between the exhaust gas line 7 and the charge air line 4 . In terms of circuitry parallel to the exhaust gas recirculation control device 31 , the blow-by control device 21 is provided, which includes a blow-by control valve 23 and a blow-by check valve 24 . The exhaust gas check valve 34 and the blow-back check valve 24 are arranged antiparallel to one another, the exhaust-gas check valve 34 opening in the direction of the charge air line 5 and the blow-back check valve 24 in the direction of the exhaust line 7 . Downstream of the blow-around control device 21 or upstream of the exhaust gas recirculation control device 31 , a cooler 41 is arranged in a common line 40 .

Since the blow-off effects occur automatically in the desired operating range solely on the basis of the conveying characteristics of the exhaust gas turbocharger 4 , complicated control can be dispensed with. The switching valves 23 and 33 connected to the control unit 16 via lines 23 a and 33 a serve only to prevent an undesired influencing of the exhaust gas recirculation by the Umbla solution. Optionally, the switching valves 23 and 33 can also be replaced by a three-way valve 42 which switches between exhaust gas recirculation and blow-by. This variant is shown by dashed lines in FIGS. 2 and 3.

Combined blowing by means of the blowing device 20 on the one hand and carrying out a fully flexible boost pressure control by means of the relief valve 9 on the other hand can prevent safe operating limits in the compressor map from being exceeded when the ambient air pressure decreases. This is shown on the basis of the compressor map shown in FIG. 5. The compression ratio p ₂ / p _{1 of} the compressor 6 is plotted against the volume flow v. n _L denote constant supercharger speeds. n _mot denotes constant engine speeds. Η are shell curves with constant efficiency. The dashed line P _G represents the surge line of the compressor. Approach If the internal combustion engine from an operating point A ₀ with an engine speed of, for example 1000 rev / min would very quickly reach the surge limit P _G at the point A ₁ at startup of the Ver dichters 6 become. By blowing at low engine speeds, the operating point of the compressor shifts from A ₀ to A ₂ in the map to the right, causing it to move away from the surge limit P _G. Without further measures, the decrease in the boost pressure p in front of the engine would lead to a loss of performance. To compensate for this, a fully flexible boost pressure control is carried out by blowing off the relief valve 9 as a function of the engine speed n and the ambient pressure in front of the turbine 8 such that the boost pressure p corresponds to the desired course over the engine speed n and is largely independent of it the geodetic height.

Claims (15)

1. Method for operating an internal combustion engine ( 1 ), in particular a diesel internal combustion engine, with an exhaust gas turbocharger ( 4 ) with a turbine part ( 8 ) arranged in an exhaust gas line ( 7 ) and a compressor part ( 6 ) arranged in a charging air line ( 5 ) ), a blow-off valve ( 9 ) being arranged upstream of the turbine part ( 8 ) in the exhaust line ( 7 ), and with a blow-off device ( 20 ) for the controlled transfer of compressed charge air from the charge air line ( 5 ) to the exhaust line ( 7 ), in particular at low speeds, a controlled transfer of compressed charge air to the exhaust line ( 7 ) is carried out via the blow-off device ( 20 ), characterized in that the boost pressure course (p) by means of the blow-off valve ( 9 ) above the speed (n) to the torque curve of the Internal combustion engine ( 1 ) is adjusted, the actual boost pressure (p _i ) being compared with a setpoint value stored in a control unit ( 16 ). Charging pressure curve (p _s ) compared to the speed (n) and a comparison signal (s) is generated from the comparison, with which the relief valve ( 9 ) is actuated di rectly or indirectly. 2. The method according to claim 1, characterized in that the controlled transfer of compressed charge air to the exhaust pipe ( 7 ) is carried out in dependence on the ambient pressure. 3. The method according to claim 1 or 2, characterized in that the blow-off valve ( 9 ) indirectly via a in a with the blow-off valve ( 9 ) connected air line ( 13 ), preferably between the charge air line ( 5 ) and blow-off valve ( 9 ), and with the control unit ( 16 ) connected nes control valve ( 14 ) is actuated. 4. Internal combustion engine ( 1 ), in particular diesel internal combustion engine, with egg nem turbocharger ( 4 ) with a turbine part ( 8 ) arranged in an exhaust gas line ( 7 ) and a compressor part ( 6 ) arranged in the charge air line ( 5 ), being upstream of the Turbine part ( 8 ) in the exhaust line ( 7 ), a relief valve ( 9 ) is arranged, and a Umblasevorrich device ( 20 ) for the controlled transfer of compressor charge air from the charge air line ( 5 ) to the exhaust line ( 7 ), characterized in that the relief valve ( 9 ) can be actuated as a function of the boost pressure (p), the boost pressure curve (p) being adaptable to the torque curve of the internal combustion engine via the speed (n). 5. Internal combustion engine ( 1 ) according to claim 4, characterized in that the relief valve ( 9 ) via an air line ( 13 ) with the charge air line ( 5 ) is connected, the pressure in the air line ( 13 ) via an electronic control unit ( 16 ) depending on the charge air pressure (p) and the engine speed (n) actuatable control valve ( 14 ) can be changed. 6. Internal combustion engine ( 1 ) according to claim 5, characterized in that the control valve ( 14 ) is arranged in the air line ( 13 ). 7. Internal combustion engine ( 1 ) according to claim 5, characterized in that the control valve ( 14 ) in a with the air line ( 13 ) connected vent line ( 13 c) is arranged. 8. Internal combustion engine ( 1 ) according to one of claims 4 to 7, characterized in that the blowing device ( 20 ) in an exhaust gas recirculation device ( 30 ) is integrated. 9. Internal combustion engine ( 1 ) according to claim 8, characterized in that the blow-around device ( 20 ) has a blow-around control device ( 21 ), which is arranged in circuitry parallel to an exhaust gas recirculation control device ( 31 ) of the exhaust gas recirculation device ( 30 ). 10. Internal combustion engine ( 1 ) according to claim 9, characterized in that the blow-by control device ( 21 ) consists of a blow-by control valve ( 23 ) and a blow-off check valve ( 24 ) opening in the direction of the exhaust pipe ( 7 ). 11. Internal combustion engine ( 1 ) according to one of claims 9 or 10, characterized in that the exhaust gas recirculation control device ( 31 ) has a gas check valve ( 34 ) and preferably an exhaust gas recirculation control valve ( 33 ). 12. Internal combustion engine ( 1 ) according to claim 10 and 11, characterized in that the blow-back check valve ( 24 ) is arranged anti-parallel to the exhaust gas check valve ( 34 ) of the exhaust gas recirculation control device ( 30 ). 13. Internal combustion engine ( 1 ) according to one of claims 9 to 12, characterized in that the blow-around control valve ( 23 ) and / or the exhaust gas recirculation control valve ( 33 ) is formed by a control flap. 14. Internal combustion engine ( 1 ) according to one of claims 8 to 13, characterized in that a three-way valve ( 42 ) is provided in the exhaust gas recirculation line ( 32 ) or in a common for gas recirculation and blow-off ( 40 ), which optionally the Exhaust gas recirculation or recirculation activated. 15. Internal combustion engine ( 1 ) according to one of claims 8 to 14, characterized in that the blow-by control device ( 20 ) - viewed in the blow-by direction - is arranged in front of a cooler ( 41 ).