DE102015200155A1 - Control device for an internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine equipped with a first and a second supercharger. A first compressor of the first charger and a second compressor of the second charger are arranged in series, and the second compressor is disposed downstream of the first compressor. The state of charge by the first and second compressors is controlled based on an operating condition of the engine. It is determined whether or not an oil coking occurrence condition is satisfied during the charge control. The oil coking occurrence condition is a condition that oil coking may occur on at least one of the first and second compressors. The operating condition of the engine is limited to such an operating condition that occurrence of the oil coking can be suppressed when it is determined that the oil coking occurrence condition is satisfied.

Description

Background of the invention

Field of the invention

The present invention relates to a control apparatus for an internal combustion engine equipped with two superchargers, and more particularly to the controller which performs control to suppress occurrence of oil coking in superchargers of the superchargers.

Description of the Prior Art

The Japanese Patent Application Laid-open Publication No. 2006-299827 (JP'827) discloses a controller that performs a control to suppress an occurrence of oil coking in a compressor of a supercharger. According to this controller, a target maximum boost pressure that is an upper limit of the boost pressure is set based on the engine speed, an oil deterioration target boost pressure is set based on an occurrence condition of the oil coking by oil deterioration, thus, based on a Temperature of the supercharger is set, and a smaller one of the maximum target boost pressure and the oil deterioration target boost pressure is selected as a final target boost pressure.

The in JP'827 shown engine is equipped with a loader. Accordingly, with respect to the dual-load engine, JP'827 does not disclose control for suppressing occurrence of oil coking in any of compressors of the two superchargers.

Overview of the invention

The present invention has been made in consideration of the above-described point, and an object of the present invention is to provide a controller for a dual-load internal combustion engine which can surely suppress occurrence of oil coking in each of the compressors of the two superchargers ,

In order to achieve the above object, the present invention provides a control apparatus for an internal combustion engine provided with first and second loaders ( 11 . 12 ), the air in an inlet passage ( 2 ) of the engine and output the pressurized air, with a first compressor ( 115 ) of the first loader ( 11 ) and a second compressor ( 125 ) of the second loader ( 12 ) are arranged in series, and the second compressor ( 125 ) downstream of the first compressor ( 115 ) is arranged. The controller is characterized by comprising a charge control means, an oil coking occurrence condition determining means, and an oil coking occurrence suppressing means. The charging control means controls a state of charge by the first and second compressors ( 115 . 125 ) based on an operating condition of the engine. The oil coking occurrence condition determining means determines whether or not an oil coking occurrence condition is satisfied during the charge control by the charge control means. The oil coking occurrence condition is a condition that oil coking may occur on at least one of the first and second compressors. The oil coking occurrence suppressing means limits the operating condition of the engine to such an operating condition that occurrence of oil coking can be suppressed when the oil coking occurrence condition determining means determines that the oil coking occurrence condition is satisfied.

With this configuration, the state of charge is controlled by the first and second compressors based on the operating state of the engine, and it is determined when the charge control is performed, whether the Ölverkokung-emergence condition that an oil coking in at least one of the first and second compressors is satisfied or not. The operating condition of the engine is limited to such an operating condition that occurrence of the oil coking can be suppressed when it is determined that the oil coking occurrence condition is satisfied.

Since the state of charge of two chargers is controlled based on the engine operating state, such a state of charge may exist that one supercharger substantially assumes a stop state and only the other supercharger operates to pressurize the intake air. Therefore, by determining the oil coking occurrence condition that the oil coking may occur on at least one of the first and second compressors, it is possible to limit the engine operating condition so that no oil coking occurs in both the first and second compressors Occurrence of Ölverkokung in the two compressors is safely suppressed.

Preferably, the oil coking occurrence condition determining means includes an output gas temperature obtaining means for obtaining first and second output gas temperatures (TCMP1E, TCMP2E), the first output gas temperature (TCMPIE) being a temperature of one from the first compressor ( 115 ) and the second output gas temperature (TCMP2E) is a temperature of one of the second compressor ( 125 ), and the oil coking occurrence condition determining means determines that the oil coking occurrence condition is satisfied when the higher (TCMPX) of the first and second discharge gas temperatures (TCMP1E, TCMP2E) exceeds a first determination threshold (TCTH1H).

With this configuration, each of the first discharge gas temperature, which is a temperature of the gas discharged from the first compressor, and the second discharge gas temperature, which is a temperature of the gas discharged from the second compressor, is obtained, and it is determined that the oil coking Occurrence condition is satisfied when the higher of the first and second discharge gas temperatures exceeds the first determination threshold. Accordingly, the oil coking occurrence condition is determined by using the discharge gas temperature at which there is a higher possibility that the oil coking occurs, which makes it possible to surely suppress the occurrence of oil coking in the two compressors.

Preferably, the oil coking occurrence condition determining means includes a supercharging system temperature obtaining means for obtaining a temperature (TCMPTSE) from a supercharger system including the first and second compressors (TCMPTSE). 115 . 125 ), and the oil coking occurrence condition determining means determines that the oil coking occurrence condition is satisfied when a higher one (TCMPMX) of the first and second output gas temperatures (TCMP1E, TCMP2E) exceeds the first determination threshold value (TCTH1H), or if by the temperature obtained by the supercharger system temperature obtaining means (TCMPTSE) exceeds a second determination threshold (TCTH2H).

With this configuration, the temperature is obtained from the supercharger system including the first and second compressors, and it is determined that the oil coking occurrence condition is satisfied when a higher of the first and second discharge gas temperatures exceeds the first determination threshold, or if the obtained Charger system temperature exceeds the second determination threshold. That is, the temperature condition of the two compressors is determined by the two methods. Accordingly, it is possible to increase a reliability of the determination of the oil coking occurrence condition, and thus to increase the reliability of the control for suppressing the occurrence of oil coking.

The present invention is effective for the engine equipped with an exhaust gas recirculation passage (FIG. 8th ) to supply an exhaust gas of the engine to the intake passage ( 2 ), and with a blowby gas passage ( 10 ) to deliver a blow-by gas generated in the engine to the intake passage (FIG. 2 ) to deliver. The exhaust gas recirculation passage ( 8th ) is with the inlet passage ( 2 ) at a portion upstream of the first compressor ( 115 ), and the blowby gas passage ( 10 ) is with the inlet passage ( 2 ) at a portion upstream of the first compressor ( 115 ) and downstream of the connection portion of the exhaust gas recirculation passage (FIG. 8th ) connected.

With this configuration, the exhaust gas at a high temperature is returned to the section upstream of the compressors, causing the compressor temperature (or the discharge gas temperature) to increase rapidly. Further, the blowby gas supplied to the intake passage by the blow-by gas passage includes lubricating oil components in the crankcase of the engine, and the blow-by gas further increases the intake air temperature already increased by the recirculated exhaust gas, which is a likelihood of occurrence of the exhaust gas Oil coking increased. Accordingly, by using the configuration described in claim 1, a significant effect of suppressing occurrence of oil coking can be obtained.

Preferably, the oil coking occurrence suppressing means comprises a boost pressure upper limit switching means and / or an output torque upper limit switching means. The boost pressure upper limit switching means switches an upper limit value (P2LMHOC) from a target boost pressure to a value of a lower boost pressure when it is determined that the oil coking occurrence condition is satisfied, and the output torque upper limit switching means switches an upper limit value (TRQLMHOC) from an output torque of the engine to a lower torque value when it is determined that the oil coking occurrence condition is satisfied.

With this configuration, switching from the upper limit value of the target boost pressure to a value with a lower boost pressure and / or switching the upper limit value from the output torque of the engine to a value with a lower torque is performed when it is determined that the oil coking occurrence condition is satisfied. A reduction from the upper limit value of the target boost pressure or a reduction from the upper limit value of the engine output torque makes it possible to increase the output gas temperature of the working one Suppress compressor. In addition, a reduction of the two upper limit values makes it possible to more quickly obtain the effect of suppressing the occurrence of oil coking.

Brief description of the figures

1 FIG. 10 is a drawing illustrating a configuration of an internal combustion engine according to an embodiment of the present invention. FIG.

2 FIG. 10 is a block diagram showing a configuration of a control system for controlling the in 1 shown engine shows.

3 is a drawing illustrating a short description of boost pressure control.

4 FIG. 10 is a flowchart of a method for determining the oil coking occurrence condition. FIG.

5 FIG. 10 is a flowchart of a method of calculating an upper limit value of the target boost pressure (P2LMHOC) used to suppress an occurrence of oil coking.

6 FIG. 10 is a flowchart of a method for calculating an upper limit value of engine output torque (TRQLMHOC) used to suppress occurrence of oil coking; and FIG

7A to 7C Fig. 10 is timing charts showing an example of control operation in this embodiment.

Detailed Description of the Preferred Embodiments

Preferred embodiments of the present invention will now be described with reference to the figures.

1 FIG. 10 is a drawing illustrating a configuration of an internal combustion engine according to an embodiment of the present invention. FIG. The internal combustion engine (hereinafter referred to as "engine") 1 For example, having four cylinders, is a diesel engine in which fuel is injected directly into the cylinder and in which compression ignition is performed. Each cylinder is equipped with a fuel injection valve 9 fitted.

The motor 1 is equipped with an inlet passage 2 , an outlet passage 3 , a first turbocharger (supercharger) 11 and a second turbocharger (supercharger) 12 , The first turbocharger 11 is with a turbine 112 equipped with a turbine wheel 111 which is rotated by kinetic energy from the exhaust gas, and with a compressor 115 , which is a compressor wheel 114 which has a shaft 113 with the turbine wheel 111 connected is. The compressor wheel 114 puts in the engine 1 absorbed air under pressure (compresses it). It should be noted that the compressor 115 as the first compressor 115 is called, if necessary, the compressor 115 from a compressor 125 to distinguish which of the second turbocharger described below 12 forms. The turbine 112 is also called the first turbine 112 designated.

The second turbocharger 12 is with a turbine 122 equipped with a turbine wheel 121 which is rotated with kinetic energy from the exhaust gas, and with a compressor 125 , which is a compressor wheel 124 which has a shaft 123 with the turbine wheel 121 connected is. The compressor wheel 124 sets from the first compressor 115 discharged air under pressure (compresses it). It should be noted that the compressor 125 as the second compressor 125 is called, if necessary, the compressor 125 from the compressor 115 to distinguish which is the first turbocharger 11 forms as described above. The turbine 122 is also called the second turbine 112 designated.

The second turbine 122 has a plurality of variable blades ( 126 ) (only two variable blades are in 1 shown) and has a paddle actuator 126a on (shown in 2 ) to the moving blades 126 to operate so that they open and close. The majority of moving blades 126 are actuated to open and close them to change a flow rate of the exhaust gas which is to the turbine wheel 121 is injected. The second turbine 122 is configured such that the flow rate of the exhaust gas, which is to the turbine wheel 121 is injected, is changed by an opening of the movable blades 126 is changed to the speed of the turbine wheel 121 to change.

An inlet bypass passage 4 that is the second compressor 125 bypasses, is with the intake passage 2 connected, and the inlet bypass passage 4 is with a compressor bypass valve 14 equipped to control a flow rate of the gas flowing therethrough.

A first outlet bypass passage 5 , the first turbine 112 bypasses, and a second exhaust bypass passage 6 who is the second turbine 122 bypasses are with the outlet passage 3 connected. The first outlet bypass passage 5 is with a first turbine bypass valve 17 equipped to control a flow rate of the gas flowing therethrough, and the second exhaust bypass passage 6 is with a second turbine bypass valve 18 equipped to control a flow rate of the gas flowing therethrough. A DPF (Diesel Particulate Filter) 21 is downstream of the first turbine 112 in the outlet passage 3 arranged.

The motor 1 is with a first and a second exhaust gas recirculation passage 7 and 8th fitted. The first exhaust gas recirculation passage 7 is between a portion of the outlet passage 3 immediately downstream of the engine main body 1a and a portion of the intake passage 2 immediately upstream of the engine main body 1a connected. The second exhaust gas recirculation passage 8th is between a portion of the exhaust passage 3 downstream from the DPF 21 and a portion of the inlet passage 2 upstream of the first compressor 115 connected. The first and second exhaust gas recirculation passages 7 and 8th is each with a first exhaust gas recirculation control valve 19 and a second exhaust gas recirculation control valve 20 equipped to control amounts of the recirculated exhaust gas.

The inlet passage 2 is with a first and a second throttle valve 13 and 16 equipped, and with an intercooler 15 , The first throttle valve 13 is upstream of a connection portion of the second exhaust gas recirculation passage 8th and the inlet passage 2 arranged. The second throttle valve 16 is downstream of the intercooler 15 and upstream of a connection portion of the first exhaust gas recirculation passage 7 and the inlet passage 2 arranged. The intercooler 15 is downstream of the second compressor 125 (a connecting portion from the inlet bypass passage 4 ) and upstream of the second throttle valve 16 arranged. The first and the second throttle valve 13 and 16 are configured by first and second throttle actuators 13a and 16a be operated.

A blowby gas passage 10 is with the intake passage 2 connected, and the blowby gas passage 10 connects a crankcase from the engine main body 1a with a portion of the inlet passage 2 upstream of the first compressor 115 and downstream of a connection portion of the second exhaust gas recirculation passage 8th , The blowby gas passage 10 is with a one-way valve 10a equipped, and the one-way valve 10a opens when the pressure on the crankcase side becomes higher than the pressure on the side of the intake passage 2 to a value equal to or higher than a predetermined pressure.

An intake air flow rate sensor 31 for detecting an intake air flow rate GAIR is in the intake passage 2 upstream of the first throttle valve 13 arranged. An intake air temperature sensor 32 for detecting an intake air temperature TA and an intake pressure sensor 33 for detecting an intake pressure (boost pressure) PB are in the intake passage 2 downstream of the second throttle valve 16 arranged.

2 FIG. 10 is a block diagram showing a configuration of a control system that controls the engine. FIG 1 performs. The intake air flow rate sensor described above 31 , the intake air temperature sensor 32 and the inlet pressure sensor 33 are with an electronic control unit 30 (hereinafter referred to as "ECU"). In addition, there is an atmospheric pressure sensor 34 for detecting an atmospheric pressure PA, an engine speed sensor 35 for detecting a rotational speed NE of the engine 1 , an acceleration sensor 36 for detecting an amount AP by which the accelerator pedal (not shown) passes through the engine 1 driven down vehicle, a coolant temperature sensor 37 for detecting an engine coolant temperature TW and other sensors, not shown, with the ECU 30 connected. Detection signals from these sensors become the ECU 30 fed.

The fuel injectors 9 , the compressor bypass valve 14 , the first and second turbine bypass valves 17 and 18 , the first and the second exhaust gas recirculation control valves 19 and 20 , the first and second throttle actuators 13a and 16a and the paddle actuator 126a are on the output side with the ECU 30 connected.

The ECU 30 includes an input circuit, a central processing unit (hereinafter referred to as "CPU"), a memory circuit, and an output circuit. The input circuit performs various functions, including shaping the waveforms of input signals from various sensors, correcting the voltage levels of the input signals to a predetermined level, and converting analog signal values to digital values. The memory circuit preliminarily stores various operation programs to be executed by the CPU and stores the results of calculations or the like by the CPU. The output circuit provides control signals to the fuel injectors 9 , the compressor bypass valve 14 , the first and second turbine bypass valves 17 and 18 and the same.

The ECU 30 performs controls, such as fuel injection control, with the fuel injectors 9 , a boost pressure control with the compressor bypass valve 14 , the first and second turbine bypass valves 17 and 18 and the paddle actuator 126a , an exhaust gas recirculation control with the exhaust gas recirculation control valves 19 and 20 , an intake air quantity control with the throttle valves 13 and 16 The requested torque TRQD is calculated mainly in accordance with the operation amount of the accelerator AP, so that it increases as the amount of operation of the accelerator AP increases, it should be noted that the requested engine torque NEQ and a requested torque TRQD Moment TRQD is set to a value that is not the upper limit of the output torque of the motor 1 exceeds. Further, the fuel injection amount QINJ becomes the fuel injection valve 9 is set and calculated according to the requested torque TRQD so that it increases as the requested torque TRQD increases.

3 13 is a drawing for explaining a brief description of the boost pressure control in this embodiment, and engine operating ranges R1 to R3 and R1a are shown, which are defined by the engine speed NE and the fuel injection amount QINJ.

In the first operating region R1, the compressor bypass valve 14 , the first turbine bypass valve 17 and the second turbine bypass valve 18 all fully closed, and the boost pressure control / regulation is performed by opening the moving blades 126 will be changed. In the area R1a within the first operating area R1, the exhaust gas recirculation is performed, and control is performed to mainly improve the properties of the exhaust gas and the fuel consumption characteristics. In the area within the first operating area except the area R1a, control is performed to mainly improve the acceleration characteristics.

In the second operating region R2, the variable vanes 126 fully open, and the boost pressure control is performed by opening an opening from the second turbine bypass valve 18 will be changed. The control / regulation in which a charge mainly through the second turbocharger 12 is transferred, is transferred to a controller, in which a charge mainly by the first turbocharger 11 is carried out.

In the third operating range R3 are the compressor bypass valve 14 and the second turbine bypass valve 18 fully open, allowing a charge through the second turbocharger 12 is not performed, but only a charge through the first turbocharger 11 wherein the boost pressure control is performed by opening an opening of the first turbine bypass valve 17 will be changed.

4 FIG. 10 is a flowchart of a method for determining the oil coking occurrence condition, and this procedure is performed at predetermined time intervals in the ECU 30 carried out.

In step S11, a model output value TCMP1EM corresponding to a first estimated output gas temperature TCMP1E which is an estimated temperature of the gas (mainly air) received from the first compressor 115 is calculated using a model of the turbocharger, and the first estimated output gas temperature TCMP1E is calculated by subjecting the model output value TCMP1EM to a first-order lag method. The model output value TCMP1EM is calculated using the following detected parameters as input parameters from the model: the intake air flow rate GAIR, the engine speed NE, the intake air temperature TA, the intake pressure PB, and the accelerator operation amount AP.

The first-order lag method is a method shown by the following equation (1). In the equation (1), CD1 is a filter coefficient set to a value between 0 and 1, and k is a discrete time digitized with the calculation period. TCMP1E (k) = CD1 × TCMP1EM (k) + (1-CD1) × TCMP1E (k-1) (1)

In step S12, a model output value TCPM2EM corresponding to a second estimated output gas temperature TCPM2E, which is an estimated temperature of the gas (mainly air), that is from the second compressor is calculated 125 is output using the model of the turbocharger, and the second estimated output gas temperature TCPM2E is calculated by applying the model output value TCPM2EM to the following equation (2) (by subjecting the model output value TCPM2EM to the first-order lag method ). In the equation (2), CD2 is a filter coefficient set to a value between 0 and 1. The model output value TCPM2EM is calculated as the input parameter of the model using the following detected parameters: the intake air flow rate GAIR, the engine speed NE, the intake air temperature TA, the intake pressure PB and the accelerator operation amount AP. TCMP2E (k) = CD2 × TCMP2EM (k) + (1-CD2) × TCMP2E (k-1) (2)

It should be noted that a known estimation method using a model is applicable to calculate the estimated output gas temperatures TCMP1E and TCMP2E (for example, a method which is described in U.S.P. Japanese Patent Application Laid-Open Publication No. 2007-205339 is shown).

In step S13, a higher one of the first estimated discharge gas temperature TCMP1E and the second estimated discharge gas temperature TCMP2E is selected as a determination discharge gas temperature TCMPX which is applied to the determination of the oil coking occurrence condition. In step S14, it is determined whether or not a first high-temperature determination flag FHTMP1 is set to 1. The first high-temperature determination flag FHTMP1 is initially set to "0", and it is set to "1" when the determination output gas temperature TCMPX exceeds a first upper determination threshold TCTH1H (step S16).

Normally, the answer to step S14 is negative (No), and the process proceeds to step S15, where it is determined whether the determination output gas temperature TCMPMX is higher than the first upper determination threshold TCTH1H (for example, 190 ° C) or not. While the answer to step S15 is negative (NO), the process immediately proceeds to step S19. If the answer to step S15 is affirmative (YES), the process proceeds to step S16 in which the first high-temperature determination flag FHTMP1 is set to 1. The process then proceeds to step S19.

If step S16 is performed, the answer to step S14 becomes affirmative (YES). Then, it is determined whether the determination output gas temperature TCMPMX is lower than a first lower determination threshold TCTH1L (<TCTH1H, for example, 170 ° C) (step S17). First, the answer to step S17 is negative (NO), and the process immediately proceeds to step S19. If the determination output gas temperature TCMPMX falls, so that the answer to step S17 is made affirmative (YES) by performing the output torque limiting method and the boost pressure limiting method as described below or due to a change in the engine operating condition the first high-temperature determination flag FHTMP1 is set to "0" (step S18). The process then proceeds to step S19.

In step S19, a TCMPTS map is retrieved according to the engine rotational speed NE and the fuel injection amount QINJ to calculate a map value TCMPTSMP of an estimated supercharger system temperature, and the estimated supercharger system temperature TCMPTSE is calculated by substituting the map value TCMPTSMP to the following equation (3). is applied (by subjecting the map value TCMPTSMP to the first-order lag method). In the TCMPTS map, map values TCMPTSMP are respectively set corresponding to the operation areas R1 to R3 included in 3 are set, and are set so that the map value TCMPTSMP becomes higher as the engine speed NE increases, and the map value TCMPTSMP becomes higher as the fuel injection amount QINJ increases. In the equation (3), CD3 is a filter coefficient set to a value between 0 and 1. TCMPTSE (k) = CD3 × TCMPTSMP (k) + (1-CD3) × TCMPTSE (k-1) (3)

An estimation accuracy of the temperatures can be increased by performing the first-order lag method with the equations (1) to (3) because an actual temperature change with respect to a change in the engine operating state is delayed.

In step S20, it is determined whether or not a second high-temperature determination flag FHTMP2 is set to "1". The second high-temperature determination flag FHTMP2 is initially set to "0" and is set to "1" when the estimated supercharger system temperature TCMPTSE exceeds a second upper determination threshold TCTH2H (step S22).

Normally, the answer to step S20 is negative (NO), and the process proceeds to step S21, where it is determined whether the estimated supercharger system temperature TCMPTSE is higher than the second upper determination threshold TCTH2H or not (for example, 190 ° C). While the answer to step S21 is negative (NO), the process immediately proceeds to step S25. If the answer to step S21 is affirmative (YES), the process proceeds to step S22 in which the second high-temperature determination flag FHTMP2 is set to "1". The process then proceeds to step S25.

If step S22 is performed, the answer to step S20 becomes affirmative (YES). Then, it is determined whether the estimated supercharger system temperature TCMPTSE is lower than a second lower one Determination threshold TCTH2L (<TCTH2H, for example, 170 ° C) (step S23). First, the answer to step S23 is negative (NO), and the process immediately proceeds to step S25. When the estimated supercharger system temperature TCMPTSE falls, so that the answer to step S23 becomes affirmative (YES) by performing the output torque limiting method and the supercharging pressure limiting method as described below, or due to a change in the engine operating condition, the second high temperature becomes Determination flag FHTMP2 is set to "0" (step S24). The process then proceeds to step S25.

In step S25, it is determined whether or not the first high-temperature determination flag FHTMP1 and the second high-temperature determination flag FHTMP2 are both "0". If the answer to step S25 is affirmative (YES), an oil coking occurrence condition flag FCLK is set to "0" (step S26). On the other hand, if the answer to step S25 is negative (NO), that is, the first high-temperature determination flag FHTMP1 or / and the second high-temperature determination flag FHTMP2 is "1", it is determined that the oil coking occurrence condition is satisfied, and the oil coking occurrence condition flag FCLK is set to "1" (step S27).

5 FIG. 10 is a flowchart of a method of calculating an upper limit value for a boost pressure P2LMHOC, which is applied to suppress occurrence of the oil coking. This procedure is performed with predetermined time intervals in the ECU 30 carried out.

In step S31, a P2MXNEH map is retrieved according to the engine rotational speed NE and the atmospheric pressure PA to calculate a first large upper limit value P2MXNEH. The P2MXNEH map is set so that the first large upper limit P2MXNEH increases as the engine speed NE increases and the first large upper limit P2MXNEH decreases as the atmospheric pressure PA decreases.

In step S32, a P2MXTAH map is obtained according to the intake air temperature TA and the atmospheric pressure PA to calculate a second large upper limit value P2MXTAH. The P2MXTAH map is set so that the second large upper limit P2MXTAH decreases as the intake air temperature TA increases, and the second large upper limit P2MXTAH decreases as the atmospheric pressure PA decreases.

In step S33, the large upper limit value for the boost pressure P2MXH is set to be the smaller one of the first large upper limit value P2MXNEH and the second large upper limit value P2MXTAH.

In step S34, a P2MXNEL map is retrieved according to the engine rotational speed NE and the atmospheric pressure PA to calculate a first small upper limit value P2MXNEL. The P2MXNEL map is set so that the first small upper limit P2MXNEL increases as the engine speed NE increases, and the first lower upper limit P2MXNEL decreases as the atmospheric pressure PA decreases. Furthermore, the first small upper limit value P2MXNEL is set to a value smaller than the corresponding first large upper limit value P2MXNEH.

In step S35, a P2MXTAL map is retrieved according to the intake air temperature TA and the atmospheric pressure PA to calculate a second small upper limit value P2MXTAL. The P2MXTAL map is set so that the second small upper limit value P2MXTAL decreases as the intake air temperature TA increases, and the second lower upper limit value P2MXTAL decreases as the atmospheric pressure PA decreases. Further, the second small upper limit P2MXTAL is set to a value smaller than the corresponding second large upper limit P2MXTAH.

In step S36, the small upper limit value of the supercharging pressure P2MXL is set to a smaller one of the first small upper limit value P2MXNEL and the second small upper limit value P2MXTAL.

In steps S37 to S43, the upper limit switching is performed with the upper limit value for the boost pressure P2LMHOC being set to the small upper limit value for the boost pressure P2MXL or the large upper limit value for the boost pressure P2MXH according to the oil coking generation condition flag FCLK , Further, a transient method is performed in which the upper limit value for the boost pressure P2LMHOC is gradually changed from the large upper limit value for the supercharging pressure P2MXH to the small upper limit value for the supercharging pressure P2MXL, or conversely, when the oil coking generation condition -Flag FLCK changes from "0" to "1", or vice versa.

In step S37, it is determined whether or not the oil coking occurrence condition flag FCLK is "1". If the answer to step S37 is negative (NO), the upper limit value for the boost pressure P2LMHOC in the increasing direction is updated by a predetermined amount of change DP (step S38). In step S39, it is determined whether the upper limit value for the boost pressure P2LMHOC is equal to or greater than the large upper limit value for the boost pressure P2MXH. If the answer to step S39 is negative (NO), the process immediately ends. When the boost pressure upper limit value P2LMHOC is equal to or greater than the boost pressure large upper limit value P2MXH, the boost pressure upper limit value P2LMHOC is set to the large upper limit value of the boost pressure P2MXH (step S40).

On the other hand, if the answer to step S37 is affirmative (yes), the upper limit value for the supercharging pressure P2LMHOC in the decreasing direction is updated by the predetermined amount of change DP (step S41). In step S42, it is determined whether the upper limit value for the boost pressure P2LMHOC is equal to or smaller than the small upper limit value for the boost pressure P2MXL. If the answer to step S42 is negative (NO), the process immediately ends. When the boost pressure upper limit value P2LMHOC is equal to or smaller than the boost pressure small upper limit value P2MXL, the boost pressure upper limit value P2LMHOC is set to the boost pressure small upper limit value P2MXL (step S43).

If the boost pressure control is in accordance with the operating condition of the engine 1 certain target boost pressure P2CMD exceeds the upper limit value of the target boost pressure P2LMHOC, the target boost pressure P2CMD is set to the upper limit value of the boost pressure P2LMHOC.

6 FIG. 10 is a flowchart of a method for calculating an upper limit value of an output torque TRQLMHOC of the engine 1 which is used to suppress occurrence of oil coking. This procedure is performed with predetermined time intervals in the ECU 30 carried out.

In the process off 6 First, an upper limit value of the fuel injection amount QILMHOC is calculated (step S51 to S59), and the upper limit value of the output torque TRQLMHOC is calculated by the upper limit value of the fuel injection amount QILMHOC in the output torque of the engine 1 is converted (step S60).

In step S51, a QILMHH map is retrieved according to the engine rotational speed NE and the atmospheric pressure PA to calculate a large upper limit value of an injection amount QILMHH. The QILMHH map is set so that the large upper limit value of the injection amount QILMHH increases as the engine speed NE increases, and the large upper limit value of the injection amount QILMHH decreases as the atmospheric pressure PA decreases.

In step S52, a QILMHL map is retrieved according to the engine rotational speed NE and the atmospheric pressure PA to calculate a small upper limit value of an injection amount QILMHL. The QILMHL map is set so that the small upper limit value of the injection amount QILMHL increases as the engine speed NE increases, and the small upper limit value QILMHL of the injection quantity decreases as the atmospheric pressure PA decreases.

In steps S53 to S59, the upper limit value switching is performed in which the upper limit value of the fuel injection amount QILMHOC is set to the small upper limit value of the injection amount QILMHH or the large upper limit value of the injection amount QILMHH according to the oil coking generation condition flag FCLK , Further, a transition process is performed in which the upper limit value of the injection amount QILMHOC is caused to gradually change from the large upper limit value of the injection amount QILMHH to the small upper limit value of the injection amount QILMHL, or conversely, when the oil coking generation condition flag FCLK changes from "0" to "1", or vice versa.

In step S53, it is determined whether or not the oil coking occurrence condition flag FCLK is "1". If the answer to step S53 is negative (NO), the upper limit value of the fuel injection amount QILMHOC is updated in the increasing direction by a predetermined amount of change DQ (step S54). In step S55, it is determined whether the upper limit value of the fuel injection amount QILMHOC is equal to or larger than the large upper limit value of the injection amount QILMHH. If the answer to step S55 is negative (NO), the process immediately proceeds to step S60. When the upper limit value of the fuel injection amount QILMHOC is equal to or larger than the large upper limit value of the injection amount QILMHH, the upper limit value of the fuel injection amount QILMHOC is set to the large upper limit value of the injection amount QILMHH (step S56).

On the other hand, if the answer to step S53 is affirmative (YES), the upper limit value of the fuel injection amount QILMHOC is updated in the decreasing direction by the predetermined amount of change DQ (step S57). In step S58, it is determined whether the upper limit value of the fuel injection amount QILMHOC is equal to or less is the small upper limit of the injection quantity QILMHL. If the answer to step S58 is negative (NO), the process immediately proceeds to step S60. If the upper limit value of the fuel injection amount QILMHOC is equal to or smaller than the small upper limit value of the injection amount QILMHL, the upper limit value of the injection amount QILMHOC is set to the small upper limit value of the injection amount QILMHHL (step S59).

In step S60, the upper limit value of the output torque TRQLMHOC is calculated by setting the upper limit value of the fuel injection amount QILMHOC to the output torque of the engine 1 is converted.

If, at the output torque control, the requested torque is TRQD, which corresponds to the operating condition of the engine 1 is determined exceeds the upper limit of the output torque TRQLMHOC, then the requested torque TRQD is set to the upper limit of the output torque TRQLMHOC.

7A to 7C FIG. 10 is time charts showing a control operation example in this embodiment. In particular, changes in the fuel injection amount QINJ ( 7A ), the determination output gas temperature TCMPMX ( 7B ) and the oil coking occurrence condition flag FCLK ( 7C ). In the 7B dotted line L1 shown indicates changes in the determination output gas temperature TCMPMX if the upper limit value of the output torque corresponding to the small upper limit value of the injection quantity QILMHL shown in FIG 7A , always when the upper limit of the output torque TRQLMHOC is applied. The broken line L2 indicates changes in the determination output gas temperature TCMPMX if the upper limit value of the output torque corresponding to the large upper limit value of the injection quantity QILMHH shown in FIG 7A , always when the upper limit of the output torque TRQLMHOC is applied. TMAXLMT, shown in 7B , is a maximum rating, and the turbocharger 11 and 12 can not be operated at an output gas temperature exceeding the maximum evaluation temperature TMAXLMT.

The requested torque TRQD rapidly increases from a time short before the time t1, and the fuel injection amount QINJ rapidly increases to exceed the small upper limit value of the injection amount QILMHL at a time t1 and the large upper limit value of the injection amount QILMHH reached immediately after time t1. At a time t2, the determination output gas temperature TCMPMX exceeds the first upper determination threshold TCTH1H, and the oil coking occurrence condition flag FCLK changes from "0" to "1".

Consequently, the upper limit of the output torque TRQLMHOC gradually decreases from a value corresponding to the large upper limit value of the injection amount QILMHH until it reaches a value corresponding to the small upper limit value of the injection quantity QILMHL at a time t3. The determination output gas temperature TCMPMX assumes a maximum value shortly after a time t2 and then decreases. At a time t4, the determination output gas temperature TCMPMX reaches the first lower determination threshold TCTH1L, and the oil coking occurrence condition flag FCLK changes from "1" to "0". As a result, the upper limit value of the output torque TRQLMHOC increases from the value corresponding to the small upper limit value of the injection quantity QILMHL until it reaches the value corresponding to the large upper limit value of the injection quantity QILMHH at a time t5.

As shown in 7A to 7C , may, when the oil coking occurrence condition is satisfied, by reducing the upper limit of the output torque of the engine 1 (the injection quantity QINJ) the temperature (s) of the compressor 115 and / or the compressor 125 be reduced, which makes it possible to suppress the occurrence of Ölverkokung.

As described above, in this embodiment, the state of charge by the first compressor 115 and the second compressor 125 based on the operating condition of the engine 1 is controlled, and it is determined when the charging control is performed, whether the oil coking occurrence condition is satisfied or not, that the Ölverkokung in at least one of the first compressor 115 and the second compressor 125 occurs using the determination output gas temperature TCMPMX, which is the higher of the first estimated output gas temperature TCMP1E and the second estimated output gas temperature TCMP2E. When it is determined that the oil coking occurrence condition is satisfied, the boost pressure upper limit value P2LMHOC is set to the small boost pressure upper limit value P2MXL, and the output torque upper limit value TRQLMHOC is set to the small upper limit value for the injection quantity QILMHL.

The two turbochargers 11 and 12 be in every operating area, which in 3 4, are respectively controlled to different states of charge based on the engine operating state (the engine speed NE and the fuel injection amount QINJ). For example, in the operating range R3, the second turbocharger becomes 12 so controlled / regulated that it is essentially a stop state and only the first turbocharger 11 is controlled so that it performs the charging process. By determining the oil coking occurrence condition that the oil coking is in at least one of the first compressor 115 and the second compressor 125 may occur is limited according to the engine operating condition so that both in the first compressor 115 as well as the second compressor 125 no oil coking occurs, thereby making it possible to surely suppress occurrence of oil coking in each compressor.

By setting the determination output gas temperature TCMPMX to a higher one of the first estimated output gas temperature TCMP1E and the second estimated output gas temperature TCMP2E, further, the oil coking occurrence condition is determined with the discharge gas temperature which is more likely to cause the oil coking. This setting of the determination output gas temperature TCMPMX therefore makes it possible to cause the oil coking in the two compressors 115 and 125 sure to suppress.

The estimated supercharger system temperature TCMPTSE, which is an estimated temperature of the supercharger system, which is the first compressor 115 and the second compressor 125 is calculated, and it is determined that the oil coking occurrence condition is satisfied when the determination discharge gas temperature TCMPMX exceeds the first upper determination threshold TCTH1H, or when the estimated supercharger system temperature TCMPTSE exceeds the second upper determination threshold TCTH2H. That is, the temperature condition of the two compressors is determined by the two methods. Accordingly, it is possible to increase a reliability of the determination of the oil coking occurrence condition, and thus to increase a reliability of the control of the suppression of oil coking.

The determination output gas temperature TCMPMX is the higher of the first estimated output gas temperature TCMP1E and the second estimated output gas temperature TCMP2E, and estimated temperature values of comparatively high accuracy can be obtained by using models corresponding to the compressors 115 and 125 correspond. However, if one of the sensors for detecting the input parameters (GAIR, TA, etc.) of the model fails, there is a high probability that, for example, the estimated temperature may include a large deviation.

On the other hand, the estimated supercharger system temperature TCMPTSE is calculated according to two parameters from the engine speed NE and the fuel injection amount QINJ, and an accuracy of the calculated temperature value may be lower compared to the first estimated output gas temperature TCMP1E and the second estimated output gas temperature TCMP2E. However, a probability that the estimated charging system temperature TCMPTSE may contain extremely large deviations is low. Accordingly, using the two methods together makes it possible to certainly perform the safer side control.

Furthermore, in the engine 1 the exhaust gas having a high temperature to the portion upstream of the first compressor 115 which causes the compressor discharge gas temperature to increase rapidly. In addition, this contains the blowby gas passage 10 to the inlet passage 2 upstream of the first compressor 115 supplied blowby gas lubricating oil components in the crankcase of the engine body 1a and the blow-by gas further increases the intake air temperature already increased by the recirculated exhaust gas, which increases a likelihood of occurrence of oil coking. By performing the switching control of the upper limit values of the boost pressure and the switching control of the upper limit values of the output torque, according to this embodiment, a remarkable effect of suppressing occurrence of the oil coking can be obtained.

In particular, reducing the upper limit value of the boost pressure P2LMHOC or reducing the upper limit value of the output torque TRQLMHCO makes it possible to suppress the output gas temperature from the working compressor. In addition, a reduction of both upper limit values makes it possible to obtain the effect of suppressing occurrence of oil coking more quickly.

In this embodiment, the ECU 30 , the compressor bypass valve 14 , the turbine bypass valves 17 and 18 and the paddle actuator 126a the charging control, the ECU 30 , the intake air flow rate sensor 31 , the intake air temperature sensor 32 , the inlet pressure sensor 33 and the engine speed sensor 35 form the oil coking occurrence condition determining means including the discharge gas temperature obtaining means and the supercharger system temperature obtaining means, and the ECU 30 forms the oil coking occurrence suppressant, the boost pressure upper limit value Switching means and the output torque upper limit switching means.

The present invention is not limited to the above-described embodiment, and various modifications may be made. For example, in the embodiment described above, the estimated output gas temperatures TCMP1E and TCMP2E are calculated using models of the first and second turbochargers 11 and 12 and the oil coking occurrence condition is determined using the estimated output gas temperatures TCMP1E and TCMP2E. Alternatively, temperature sensors may be near the output port of the compressors 115 and 125 may be arranged, and the oil coking occurrence condition may be determined using the output gas temperatures detected by the temperature sensors. In such a case, it should be noted that it is not necessary to subject the detected output gas temperatures to the first-order lag process.

Further, with respect to the supercharger system temperature, a detected value may be used instead of the estimated value. In such a case, it is necessary to arrange the temperature sensor at a position different from the localized positions of the temperature sensors for detecting the discharge gas temperatures of the compressors. It should be noted that it is not necessary to subject the detected supercharger system temperature to the first-order lag process.

Further, in the above-described embodiment, if it is determined that the oil coking occurrence condition is satisfied, both the supercharging pressure suppression control in which the upper limit value of the supercharging pressure P2LMHOC is reduced and the output torque suppression control become performed, in which the upper limit of the output torque TRQLMHOC is reduced. Alternatively, only one of the boost pressure suppression control and the output torque suppression control may be performed.

Furthermore, in the above-described embodiment, an example is shown in which the present invention is applied to the control apparatus for a diesel engine. The present invention is also applicable to a control device for a gasoline engine. Furthermore, in the embodiment described above, there is shown a control device for an engine equipped with two chargers. The method of the present invention may be modified and applied to a motor equipped with three or more chargers. That is, the estimated output gas temperature corresponding to each loader may be calculated using a model of each loader, and the highest estimated output gas temperature may be selected and applied to the determination of the oil coking occurrence condition. In addition, it is preferable to calculate the estimated supercharger system temperature according to two parameters of the engine speed NE and the fuel injection amount QINJ, and to apply the estimated supercharger system temperature to the determination of the oil coking occurrence condition.

A control device for an internal combustion engine equipped with a first and a second supercharger. A first compressor of the first charger and a second compressor of the second charger are arranged in series, and the second compressor is disposed downstream of the first compressor. The state of charge by the first and second compressors is controlled based on an operating condition of the engine. It is determined whether or not an oil coking occurrence condition is satisfied during the charge control. The oil coking occurrence condition is a condition that oil coking may occur on at least one of the first and second compressors. The operating condition of the engine is limited to such an operating condition that occurrence of the oil coking can be suppressed when it is determined that the oil coking occurrence condition is satisfied.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2006-299827 [0002, 0003]
• JP 2007-205339 [0046]

Claims (5)

A control apparatus for an internal combustion engine provided with a first and a second superchargers pressurizing air in an intake passage of the engine and discharging the pressurized air, a first compressor of the first supercharger and a second compressor of the first supercharger second supercharger are arranged in series and the second compressor is arranged downstream of the first compressor, the controller being characterized in that it comprises: a charging control means to a state of charge by the first and the second Controlling compressor on the basis of an operating condition of the engine, an oil coking occurrence condition determining means for determining whether an oil coking occurrence condition is satisfied during the charge control by the charge control means, or not, wherein the oil coking occurrence condition is a condition that oil coking be applied to at least one of the e and an oil coking occurrence suppressing means for limiting the operating condition of the engine to such an operating condition that occurrence of the oil coking can be suppressed when the oil coking occurrence condition determining means determines that the oil coking Occurrence condition is fulfilled. The controller of claim 1, wherein the oil coking occurrence condition determining means comprises an output gas temperature obtaining means for obtaining first and second discharge gas temperatures, wherein the first discharge gas temperature is a temperature of one gas discharged from the first compressor and the second Output gas temperature is a temperature of a gas discharged from the second compressor, and the oil coking occurrence condition determining means determines that the oil coking occurrence condition is satisfied when a higher one of the first and second discharge gas temperatures exceeds a first determination threshold. The controller of claim 2, wherein the oil coking occurrence condition determining means comprises a supercharging system temperature obtaining means for obtaining a temperature of a supercharger system including the first and second compressors, and the oil coking occurrence condition determining means determines that the Oil coking occurrence condition is satisfied when a higher one of the first and second discharge gas temperatures exceeds the first determination threshold value, or when the temperature obtained by the supercharger system temperature obtaining means exceeds a second determination threshold value. The controller of any one of claims 1 to 3, wherein the engine is equipped with: an exhaust gas recirculation passage connected to the intake passage at a portion upstream of the first compressor to return an exhaust gas of the engine to the intake passage, and a blow-by gas passage connected to the intake passage at a portion upstream of the first compressor and downstream of the connection portion of the exhaust gas recirculation passage to supply a blow-by gas generated in the engine. The controller of any one of claims 1 to 4, wherein the oil coking occurrence suppressant comprises a boost pressure upper limit switching means and / or an output torque upper limit switching means, the boost pressure upper limit switching means switches an upper limit value from a target boost pressure to a value of a lower boost pressure when it is determined that the oil coking occurrence condition is satisfied, and the output torque upper limit switching means sets an upper limit value of an output torque of the engine to a lower value Moment switches when it is determined that the oil coking occurrence condition is satisfied.

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