DE112008001300B4 - Compressor suction control technology - Google Patents

Abstract

A method of controlling an internal combustion engine (100) for powering a motor vehicle (10), the engine having a turbocharger with a compressor (102), the engine further having a path for recirculating exhaust gas to the engine and wherein the amount of recirculated exhaust gas is controlled by an EGR valve (107) which is controllable by a control unit (106), characterized by the following steps:detecting (301) a negative fuel rate which exceeds a predetermined threshold value and, if this is the case, occurring ( 303) to a mode in which the EGR valve is controlled to a more open position and the variable turbine geometry is controlled to a position where it produces substantially maximum turbine speed.

Description

technical field

The present invention relates to a method and a system for controlling an engine having a turbocharger and provided with an EGR valve. A corresponding computer program product and a digital storage medium are also presented.

background

Diesel engines for use in heavy vehicles, such as trucks and buses, are sometimes provided with a turbocharger, which may have a variable turbine geometry (VTG), also referred to as a variable geometry turbocharger or variable geometry turbine (VGT: English: variable geometry turbine). becomes. Such an engine can typically be provided with an EGR valve (EGR: exhaust gas recirculation). Other engines for other uses may also be turbocharged along with an EGR. One reason for adopting EGR technology is that it makes it easier to meet emission requirements for diesel engines, among others.

A turbocharger has a turbine with a variable turbine geometry that drives a compressor for supplying compressed air to the air intake of the internal combustion engine. If the difference in pressure upstream and downstream of the compressor, i.e. the pressure difference across the compressor, is high, the compressor may not be able to maintain the pressure difference and reverse gas mass flow through the compressor will occur. This is sometimes referred to as compressor surging.

One scenario that can cause compressor suck is when there is a rapid drop in fueling. In such a scenario, the turbine driving the compressor may experience a rapid drop in speed, resulting in a rapid drop in compressor performance. The turbo pressure downstream of the compressor can then be high, and at the same time the compressor can work with a low drive power. If this occurs, there is a risk that the high turbo pressure cannot be maintained and that there will be reverse gas mass flow through the compressor, i.e. compressor suction.

Reverse gas mass flow through the compressor is highly undesirable for a number of different reasons. First, such an event will produce a bang with a relatively high volume, which of course will disturb the driver of the vehicle propelled by the engine and people in the vicinity of the vehicle. Secondly, the compressor of the turbocharger is subject to an abnormal operating condition, which may shorten the life of the compressor or even directly damage the compressor. Third, a turbo pressure drop occurs, resulting in a sudden drop in torque produced by the engine, which is felt by the driver of the automobile.

It is therefore desirable to avoid reverse gas mass flow through the compressor of a turbocharged engine powering a motor vehicle. Accordingly, there is a need for a method of controlling a turbocharged internal combustion engine that avoids reverse mass flow through the turbocharger's compressor.

The document EP 1 770 270 A2 discloses an internal combustion engine that includes a block that defines at least one combustion cylinder. An intake manifold is fluidly coupled to at least one combustion cylinder and an exhaust manifold is also fluidly coupled to at least one combustion cylinder. An exhaust gas recirculation system is fluidly coupled between the exhaust manifold and the intake manifold. A turbocharger includes a variable geometry turbine that is fluidly coupled to the exhaust manifold. The variable geometry turbine is moveable to a first position effecting fluid flow of exhaust gas from the exhaust manifold to the intake manifold and to a second position effecting fluid flow of charge air to the variable geometry turbine.

The document US 2007/0 068 158 A1 discloses a method for controlling an engine having an intake manifold and an exhaust manifold, wherein an exhaust gas recirculation path is provided with a valve between the intake manifold and the exhaust manifold and the engine has a turbocharger, the method during at least one reduced engine performance condition increasing the opening of the exhaust gas recirculation valve and adjusting exhaust gas expansion through a turbine of the turbocharger to reduce expansion through the turbocharger and thereby reduce a likelihood of turbocharger surge.

outline of the invention

It is an object of the present invention, a method, a system, a computer pro to provide a gram product and digital storage medium capable of avoiding reverse gas mass flow through the compressor of a turbocharged internal combustion engine for powering a motor vehicle, such as a truck or bus.

This object and others are achieved by the method, system, computer program product and digital storage medium as set out in the appended claims. Consequently, in order to avoid reverse gas mass flow through a compressor of a turbocharged internal combustion engine, the control unit of an engine for driving a motor vehicle, for example a truck or a bus, is provided with a detector for detecting a rapid decrease in fuel supply. If the negative fueling rate is below some predetermined threshold, the controller initiates a mode in which a controller is configured to avoid surging through the turbocompressor.

In one embodiment, when the turbocompressor is provided with variable turbine geometry (VTG), the control system begins to control the VTG to produce high power when in compressor suction avoidance mode. The high power generated by the turbine will avoid a rapid power drop that can lead to compressor suction.

In one embodiment, the control system begins to control an EGR system valve to a more open position to allow gas to flow in the reverse direction in the EGR path when in compressor suction avoidance mode, thereby reducing the Charge gas pressure reduced so that compressor suction can be avoided by the turbo compressor.

In one embodiment, the control system stores a map that includes optimal EGR valve positions and optimal closed variable turbine geometry positions for different engine operating conditions, and controls the variable turbine geometry position and/or the EGR valve position to the position(s). (en) corresponding to the current engine operating states of the map. This can further reduce the risk of compressor suction.

The use of the control method according to the invention results in a smooth reduction of the charge gas pressure, thus avoiding suction through the turbocompressor, which can otherwise occur in the event of rapid fueling reduction.

character list

• 1 eine allgemeine Detailansicht eines Motors ist, der einen Turbolader mit einer VTG und einem EGR umfasst;
• 2 ein Flussdiagramm ist, das die von der Steuerungsprozedur durchgeführten Schritte darstellt, wenn ein Verbrennungsmotor gemäß einer Ausführungsform gesteuert wird, um eine rückwärts gerichtete Gasmassenströmung zu vermeiden; und
• 3 ein Flussdiagramm ist, das die von der Steuerungsprozedur durchgeführten Schritte darstellt, wenn gemäß einer anderen Ausführungsform ein Verbrennungsmotor gesteuert wird, um eine rückwärts gerichtete Gasmassenströmung zu vermeiden.

The present invention will now be described in detail, by way of non-limiting examples, with reference to the accompanying drawings, in which:

• 1 Figure 12 is a general detailed view of an engine including a turbocharger with a VTG and an EGR;
• 2 Figure 12 is a flowchart depicting the steps performed by the control procedure when controlling an internal combustion engine to avoid reverse gas mass flow according to one embodiment; and
• 3 14 is a flow chart depicting the steps performed by the control procedure when controlling an internal combustion engine to avoid reverse gas mass flow according to another embodiment.

Detailed description

In 1 selected parts of an engine 100 of a motor vehicle 10 are shown schematically. the inside 1 For example, the engine shown may be designed to be part of a truck or any other heavy vehicle such as a bus or the like. The example motor 100 in 1 is a diesel engine that is turbocharged and has five cylinders 105 . The turbocharger may be of any type, such as a variable turbine geometry (VTG) turbocharger or other turbocharger with or without a controllable turbine. The turbocharger includes a compressor 102 driven by a turbine 103. The engine also includes an EGR valve 107. The EGR valve 107 controls the amount of exhaust gas that is recirculated into the engine 100 air intake.

The engine is controlled by an electronic control unit (ECU) 106 . The ECU 106 is connected to the engine to control the engine. For example, the ECU may be configured to control EGR valve position and VTG position as well as other parameters used to control the engine. In addition, sensors provide sensor signals to the ECU 106 . Using the sensor signals, the ECU 106 performs control of the engine using some programmed computer instructions or similar means. Typically, the programmed computer instructions are provided in the form of a computer program product 110 stored on a readable digital storage medium 108, such as a memory card, read only memory (ROM), random access memory (RAM), EPROM, EEPROM, or flash memory. Storage.

In 2 1 is a flow chart depicting the steps performed in a control procedure performed by an ECU when controlling a VTG equipped engine to avoid reverse gas mass flow through a turbo compressor of the engine. In a first step 201 the ECU detects a rapid decrease in fueling, ie it detects that the change in fuel rate is below a certain predetermined level. If the fuel rate is detected to be severely negative and below a certain predetermined value, the ECU switches a control mode and proceeds to a second step 203 . In the second step 203, the position of the VTG is controlled to produce maximum turbine speed to assist the compressor in maintaining turbo pressure. By controlling the VTG position to maximize turbine speed at the reduced fueling, the risk of rapid fueling reduction resulting in reverse gas mass flow through the compressor is reduced and in most cases can be avoided.

The VTG position at which the control system is configured to control to maximize turbine power/speed may be given, for example, by a map that stores an optimal closed VTG position that provides a maximum turbine speed for each different condition provides in which the engine can work.

Because compressor surging occurs most frequently at high engine loads and within a relatively narrow engine speed range, the control system may be configured to control the VTG to the position corresponding to maximum power at these conditions. In other words, the control system can be simplified to adjust the VTG position that provides maximum turbine power/speed for gas mass flow, i.e. the gas mass flow corresponding to the operating condition where compressor suction is likely to occur.

Next, in a third step 205, the ECU checks whether a condition for exiting the reverse gas mass flow avoidance mode through the turbocompressor is met. If so, the procedure returns via a fourth step 207 to step 201 where the control system is returned to the original, regular control mode, otherwise the procedure remains in the mode to avoid reverse gas mass flow through the turbocompressor and the procedure returns to step 203.

In 3 1 is a flow chart showing the steps performed in a control procedure performed by an ECU when an engine provided with an EGR system is controlled to reverse mass flow through a turbo compressor of the engine according to another Embodiment of the present invention is avoided. First, in a first step 301, the ECU detects a rapid decrease in fueling, ie a change in fuel rate that is below some predetermined level is detected. Upon determining that the fuel rate is severely negative, ie below some predetermined value, the ECU switches a control mode and proceeds to a second step 303 . In the second step 303, the EGR valve is opened to a more open position to reduce turbo pressure by creating another gas exhaust path via reverse gas mass flow through the EGR path. Consequently, by controlling the EGR valve to a more open position, the risk of rapid fueling reduction resulting in reverse gas mass flow through the compressor is reduced because the high pressure gas of the turbocompressor is allowed to bleed through the EGR path instead it has to flow through the compressor of the turbocharger.

Next, in a third step 305, the ECU checks whether a condition for exiting the mode for avoiding reverse gas mass flow through the turbocompressor is met. If so, the procedure returns via a fourth step 307 to step 301 where the control system is returned to the original, regular control mode, otherwise the procedure remains in the reverse gas mass flow avoidance mode through the turbocompressor and the procedure to Step 203 returns.

The condition used to exit the reverse gas mass flow avoidance mode through the turbocompressor may be, for example, detecting wherein the negative fuel rate change is detected to be above a certain predetermined level. The level may, but need not, be the same level at which the turbocharger reverse gas mass flow avoidance mode is triggered.

According to the third embodiment of the present invention, the control systems as previously described in connection with 2 and 3 have been described combined. Consequently, upon sensing a severe negative rate of fuel decrease in an engine equipped with both a VTG and EGR system, the ECU will both command the VTG to a position where it produces maximum turbine speed to assist the compressor in maintaining turbo pressure, and control the EGR valve to a more open position to assist turbo pressure by creating another gas exhaust path via reverse gas mass flow through the EGR path.

In an embodiment where both VTG and EGR are controlled, the control system may be configured to account for the higher exhaust gas pressure created by a more closed VTG position. Consequently, if the exhaust gas pressure is increased above the supercharger gas pressure, there may be no gas flow in the reverse direction of the EGR path. By storing a map in the control system that provides the control system with combined positions for the VTG and the EGR for different operating states of the engine, it can be ensured that there is always a higher charge gas pressure than the exhaust gas pressure. This is accomplished by storing VTG positions that are more open when a VTG position that provides maximum turbine power would otherwise cause the exhaust gas pressure to exceed the supercharger gas pressure.

Claims (10)

A method of controlling an internal combustion engine (100) for powering a motor vehicle (10), the engine having a turbocharger with a compressor (102), the engine further having a path for recirculating exhaust gas to the engine and wherein the amount of recirculated exhaust gas is controlled by an EGR valve (107) which is controllable by a control unit (106), characterized by the following steps: detecting (301) a negative fuel rate which exceeds a predetermined threshold value and, if this is the case, occurring ( 303) to a mode in which the EGR valve is controlled to a more open position and the variable turbine geometry is controlled to a position where it produces substantially maximum turbine speed. procedure after claim 1 , characterized by the following steps: storing a map that has optimal EGR valve positions and/or optimal closed variable turbine geometry positions for different engine operating conditions, determining the current engine operating condition and controlling the variable turbine geometry position and/or the EGR valve - Position to the position(s) corresponding to the current engine operating condition according to the map. Procedure according to one of Claims 1 or 2 characterized by the step of: exiting the mode to avoid reverse gas mass flow through the compressor when the negative fuel rate is above a predetermined threshold. A system for controlling an internal combustion engine (100) for powering a motor vehicle (10), the engine having a turbocharger with a compressor (102), the engine further having a path for recirculating exhaust gas to the engine and wherein the amount of recirculated exhaust gas is controlled by an EGR valve (107) controllable by a control unit (106), characterized by : means (106) for detecting a negative fuel rate exceeding a predetermined threshold value and, if this is the case, entering (303) to a mode in which the EGR valve is controlled to a more open position and the variable turbine geometry is controlled to a position that produces substantially maximum turbine speed. system after claim 4 , characterized by : means for storing a map which has optimal EGR valve positions and/or optimal closed variable turbine geometry positions for different engine operating conditions, determining the current engine operating condition and controlling the variable turbine geometry position and/or the EGR valve Position to the position(s) corresponding to the current engine operating condition according to the map. system after claim 4 or 5 characterized by : means for exiting the mode to perform a return avoiding inward gas mass flow through the compressor when the negative fuel rate is above a predetermined threshold. A computer program product (110) for controlling an internal combustion engine (100) for powering a motor vehicle (10), the engine having a turbocharger with a compressor (102), the engine further having a path for recirculating exhaust gas to the engine and wherein the amount of recirculated exhaust gas is controllable by an EGR valve (107) which is controllable by a control unit (106), characterized in that the computer program product has program segments which, when loaded on a computer, for example a control unit (106), for controlling of the internal combustion engine, cause the computer to perform the following steps: detecting (301) a negative fuel rate that exceeds a predetermined threshold and, if so, entering (303) a mode in which the EGR valve is controlled to a more open position and the variable turbine geometry is controlled to a position that we essentially generates the maximum turbine speed. computer program product claim 7 , Characterized by program segments for: storing a map that has optimal EGR valve positions and/or optimal closed variable turbine geometry positions for different engine operating conditions, determining the current engine operating condition and controlling the variable turbine geometry and/or the EGR valve position the position(s) corresponding to the current engine operating condition according to the map. computer program product claim 7 or 8th characterized by program segments for: exiting the mode to avoid reverse gas mass flow through the compressor when the negative fuel rate is above a predetermined threshold. Digital storage medium (108) on which the computer program product according to any one of Claims 7 until 9 is saved.

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