JP4284649B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine including a supercharger capable of supercharging pressure control.

  Conventionally, as an internal combustion engine equipped with a supercharger, there is known an engine that sets a basic target supercharging pressure corresponding to a standard atmospheric pressure based on an engine operating state based on an engine speed and a throttle opening ( For example, see Patent Document 1.) In this internal combustion engine, the basic target boost pressure corresponding to the standard atmospheric pressure is corrected (decreased) as the atmospheric pressure decreases, and the actual boost pressure is set to match the corrected target boost pressure. The As a result, even when the internal combustion engine is operated at a high altitude where the atmospheric pressure is low, the turbocharger overrotation that occurs due to an increase in the differential pressure between the target supercharging pressure and the atmospheric pressure. Is suppressed.

JP 2000-249511 A

  However, in the above-described conventional internal combustion engine, if the atmospheric pressure is relatively low, the basic target supercharging pressure is corrected according to the atmospheric pressure, even when the turbocharger is less likely to over-rotate. . In such a case, in the conventional internal combustion engine, the supercharging pressure set with correction by the atmospheric pressure is lower than the originally required supercharging pressure, which may cause deterioration of the combustion state.

  Therefore, an object of the present invention is to provide an internal combustion engine in which the supercharging pressure can be set according to a required value regardless of the level of atmospheric pressure.

  The internal combustion engine according to the present invention is an internal combustion engine provided with a supercharger capable of supercharging pressure control, and when the required engine supercharging pressure is low, a predetermined intake pipe downstream of the compressor outlet of the supercharger. When the supercharging pressure by the turbocharger is set using the absolute pressure detected at the location, and the engine required supercharging pressure is high, at the predetermined location of the intake pipe downstream from the compressor outlet of the turbocharger The supercharging pressure by the supercharger is set using the detected relative pressure.

  In this internal combustion engine, when the required engine supercharging pressure is low regardless of the atmospheric pressure level, the absolute pressure detected at a predetermined position of the intake pipe downstream from the compressor outlet of the turbocharger is used. When the supercharging pressure by the supercharger is set and the engine required supercharging pressure is low, the relative pressure (gauge pressure) detected at a predetermined location in the intake pipe downstream from the compressor outlet of the supercharger. ) Is used to set the supercharging pressure by the supercharger. Thus, when the engine required supercharging pressure is low, i.e., when the turbocharger is less likely to over-rotate, by setting the supercharging pressure using the absolute pressure, regardless of the level of atmospheric pressure, It is possible to set the supercharging pressure to the original required value, and a sufficient intake air amount can be secured to keep the combustion state good.

  Further, the internal combustion engine of the present invention includes an exhaust gas recirculation system including an EGR flow path for recirculating exhaust gas to the intake system, and between the EGR flow path and the merged portion of the intake pipe and the compressor outlet of the supercharger. And when the engine required supercharging pressure is low, the supercharging is performed so that an absolute pressure detected between the compressor outlet and the throttle valve matches a target value. It is preferable that the supercharging pressure by the machine is set.

  If the pressure on the downstream side of the throttle valve does not change even though the EGR rate has changed due to the back pressure change, the turbocharger will change the amount of fresh air to return the EGR rate to the normal value. Is not controlled, and there is a risk that smoke and other problems may occur. On the other hand, since the upstream side of the throttle valve is not easily affected by changes in the back pressure, the absolute pressure detected between the compressor outlet and the throttle valve is the target value when the engine required supercharging pressure is low. If the supercharging pressure by the supercharger is set so as to match the above, it is possible to accurately set the supercharging pressure to the original required value, secure a sufficient amount of intake air, and maintain a good combustion state Become.

  Further, when the opening degree of the throttle valve exceeds a predetermined amount, it is determined that the engine required supercharging pressure is high, and when the opening degree of the throttle valve is equal to or less than the predetermined amount, the engine required supercharging pressure is determined. Is preferably low.

  Thus, by determining whether the engine required supercharging pressure is high or low based on the opening of the throttle valve, when the engine required supercharging pressure is low, the supercharging pressure is reliably set to the original required value. It is possible to secure a sufficient amount of intake air, and when the engine required supercharging pressure is high, it is possible to suppress over-rotation of the supercharger. Can do.

  As described above, according to the present invention, it is possible to realize an internal combustion engine in which the supercharging pressure can be set according to the required value regardless of the level of atmospheric pressure.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an internal combustion engine according to the present invention. The internal combustion engine 1 shown in the figure is configured as, for example, a multi-cylinder type diesel engine, and is used, for example, as a travel drive source of a vehicle. The internal combustion engine 1 includes a plurality (four in the present embodiment) of combustion chambers # 1, # 2, # 3, and # 4, and is not shown by the combustion of the air-fuel mixture in each of the combustion chambers # 1 to # 4. Power is generated by reciprocating the piston.

  Air is supplied to each of the combustion chambers # 1 to # 4 via the intake pipe 2. An air cleaner (not shown) is connected to the tip of the intake pipe 2, and a throttle valve (intake throttle valve) 3 is incorporated in the intake pipe 2 between the air cleaner and each of the combustion chambers # 1 to # 4. ing. Further, the internal combustion engine 1 has a fuel pump 4, a common rail 5, and a plurality of (four bodies) injectors 6 as shown in FIG. 1 in order to supply fuel to the combustion chambers # 1 to # 4. is doing. The fuel is boosted by the fuel pump 4 and distributed to the injectors 6 of the combustion chambers # 1 to # 4 via the common rail 5. Each injector 6 injects the required amount of fuel into each combustion chamber # 1 to # 4 at a predetermined timing. Exhaust gas generated by combustion in each of the combustion chambers # 1 to # 4 is discharged to the exhaust pipe 7. The exhaust pipe 7 is provided with a catalyst device 8 including, for example, a NOx occlusion reduction catalyst, and the exhaust gas from the combustion chambers # 1 to # 4 is purified in the catalyst device 8.

  Furthermore, the internal combustion engine 1 of the present embodiment has an EGR (Exhaust Gas Recirculation) flow path 9 for recirculating the exhaust gas from the exhaust pipe 7 to the intake pipe 2. An EGR valve 10 for adjusting the exhaust gas recirculation amount is provided in the middle of the EGR flow path 9, and the EGR flow path 9 and the EGR valve 10 constitute an exhaust gas recirculation system. The recirculation amount of the exhaust gas from the exhaust pipe 7 to the intake pipe 2 is controlled by adjusting the opening degree of the EGR valve 10. Thus, by mixing the exhaust gas containing carbon dioxide into the air in the intake pipe 2 via the EGR flow path 9, the combustion temperature can be lowered, and the generation of NOx and combustion noise can be suppressed.

  The internal combustion engine 1 as described above further includes a supercharger (turbocharger) 11 in order to achieve both high output and low fuel consumption. As shown in FIG. 1, the supercharger 11 includes a compressor impeller (compressor element) 12 disposed in a compressor casing connected to the intake pipe 2, and a turbine casing connected to the exhaust pipe 7. A turbine impeller (turbine element) 14. The compressor impeller 12 and the turbine impeller 14 are connected and integrated with each other by a rotating shaft 15. An intercooler 16 is arranged between the compressor casing that houses the compressor impeller 12 and the throttle valve 3.

  The supercharger 11 is configured as a so-called variable capacity type (variable nozzle type) supercharger, and as shown in FIG. 1, a plurality of movable parts arranged near the exhaust inlet of the turbine impeller 14 (turbine casing). A vane 17 and an actuator (supercharging pressure setting means) 18 for adjusting the inclination of each movable vane 17 are included. Thereby, if the opening degree of the plurality of nozzles formed by the movable vane 17 is adjusted by operating the actuator 18, the rotational speed of the turbine impeller 14 changes, and the supercharging pressure by the supercharger 11 is set to a desired value. can do. When the turbine impeller 14 of the supercharger 11 is rotationally driven by the exhaust gas discharged from each of the combustion chambers # 1 to # 4, the compressor impeller 12 rotates via the rotating shaft 15, and the compressor impeller 12 The air flowing in through the air cleaner is compressed and supplied to the combustion chambers # 1 to # 4.

  And the internal combustion engine 1 comprised as mentioned above contains the electronic control unit (henceforth "ECU") 20 which functions as a control means. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. The fuel pump 4, the injectors 6, the EGR valve 10, and the like described above are connected to the input / output ports of the ECU 20, and these are controlled by the ECU 20. Similarly, the actuator 18 of the supercharger 11 is also connected to the input / output port of the ECU 20 and is controlled by the ECU 20. In addition, an air flow meter 19 that detects the amount of air flowing into the supercharger 11 is incorporated in the intake pipe 2. The air flow meter 19 is connected to an input / output port of the ECU 20 and gives a signal indicating a detected value to the ECU 20.

  Next, the procedure of the supercharging pressure control in the internal combustion engine 1 will be described with reference to FIG.

  When the internal combustion engine 1 is started, the ECU 20 as control means controls the supercharging pressure by the supercharger 11 according to the procedure shown in FIG. In this case, the ECU 20 acquires the opening degree of the throttle valve 3 based on the signal from the throttle opening degree sensor 23 (S10). Then, the EUC 20 determines whether or not the acquired opening degree of the throttle valve 3 is equal to or less than a predetermined threshold value (S12).

  When it is determined in S12 that the opening degree of the throttle valve 3 is equal to or less than a predetermined threshold value and the operating state of the internal combustion engine 1 is in a low load region where the engine required supercharging pressure is low, the ECU 20 Based on the signal from the 1 pressure sensor 21, the absolute pressure P1 of the air in the intake pipe 2 between the compressor outlet of the supercharger 11 and the throttle valve 3 is acquired (S14). In order to accurately detect the compressor outlet pressure of the actual supercharger 11, the pressure is increased on the upstream side of the intercooler 16 (and on the downstream side of the compressor outlet of the supercharger 11) as in this embodiment. It is preferable to detect. Further, the ECU 20 reads out the target boost pressure (absolute pressure conversion) corresponding to the required torque at that time from the first boost pressure control map stored in advance in the storage device, and compresses the turbocharger 11. The actuator 18 of the supercharger 11 is controlled so that the absolute pressure P1 between the machine outlet and the throttle valve 3 coincides with the target supercharging pressure (S16).

  In this way, the supercharger 11 using the absolute pressure P1 in the low load region (region where the engine required supercharging pressure is low) where there is little risk of excessive rotation of the supercharger 11 (compressor impeller 12 and turbine impeller 14). By setting the supercharging pressure by, the supercharging pressure is reliably set to the original required value regardless of the atmospheric pressure around the internal combustion engine 1, and the intake air amount is sufficiently ensured to be in the combustion state. Can be kept good. That is, since the upper limit value of the fuel injection amount from each injector 6 is basically set according to the intake air amount, when the supercharging pressure is set with correction by the atmospheric pressure, the supercharging pressure decreases. It is possible that the intake air amount decreases, the fuel injection amount decreases accordingly, and the output decreases. On the other hand, if the supercharging pressure by the supercharger 11 is set using the absolute pressure P1 in the low load region (region where the engine required supercharging pressure is low) like the internal combustion engine 1, the low load region (engine Even if the required supercharging pressure is low), the supercharging pressure is reliably set to the original required value, and the intake air amount and the fuel injection amount are sufficiently secured. Can do.

  In particular, in this embodiment, the absolute pressure P1 is between the throttle valve 3 and the compressor outlet of the supercharger 11 that is not affected by the operation of the throttle valve 3 or the exhaust gas recirculated through the EGR flow path 9. Since it is detected, the supercharging pressure by the supercharger 11 can be set appropriately. Further, the exhaust gas recirculation amount (the opening degree of the EGR valve 10) through the EGR flow path 9 is basically set based on the amount of air flowing into the supercharger 11 detected by the air flow meter 19. However, if the supercharging pressure by the supercharger 11 is set using the absolute pressure P1 in the low load region as described above, the amount of air flowing into the supercharger 11 is set appropriately. Accordingly, the recirculation amount of the exhaust gas through the EGR flow path 9 is also set appropriately.

  On the other hand, when it is determined in S12 that the opening of the throttle valve 3 exceeds a predetermined threshold value and the operating state of the internal combustion engine 1 is in a high load region where the required engine boost pressure is high, the ECU 20 Acquires the relative pressure P2 of the air in the intake pipe 2 on the downstream side of the throttle valve 3 based on a signal from the second pressure sensor 22 and a signal from an atmospheric pressure sensor (not shown) (S18). Note that the pressure sensor 22 may be omitted, and in S18, the relative pressure of the air in the intake pipe 2 may be acquired between the compressor outlet of the supercharger 11 and the throttle valve 3. Further, the ECU 20 reads out the target boost pressure (relative pressure conversion) corresponding to the required torque or the like from the second boost pressure control map stored in advance in the storage device, and the relative pressure on the downstream side of the throttle valve 3. The actuator 18 of the supercharger 11 is controlled so that P2 matches the target supercharging pressure (S20). Thereby, in the high load region (region where the engine required supercharging pressure is high) where the opening degree of the throttle valve 3 exceeds a predetermined threshold value, the supercharger 11 ( Excessive rotation of the compressor impeller 12 and the turbine impeller 14) is suppressed. After the processing in S16 and S20, the ECU 20 repeatedly executes the supercharging pressure control from S10 to S20 every time a predetermined timing is reached.

  Needless to say, the present invention can be applied to internal combustion engines other than diesel engines. The supercharger applied to the internal combustion engine 1 described above may be a so-called motor-assisted supercharger having a turbo electric motor mounted on a rotating shaft that connects a turbine impeller and a compressor impeller.

1 is a schematic configuration diagram showing an internal combustion engine according to the present invention. 2 is a flowchart for explaining the operation of the internal combustion engine of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake pipe 3 Throttle valve 4 Fuel pump 5 Common rail 6 Injector 7 Exhaust pipe 8 Catalytic device 9 EGR flow path 10 EGR valve 11 Supercharger 12 Compressor impeller 14 Turbine impeller 15 Rotating shaft 16 Intercooler 17 Movable vane 18 Actuator 19 Air flow meter 21 First pressure sensor 22 Second pressure sensor 23 Throttle opening sensor

Claims (3)

In an internal combustion engine equipped with a supercharger capable of supercharging pressure control,
When the engine required supercharging pressure is low, the supercharging pressure by the supercharger is set using the absolute pressure detected at a predetermined location of the intake pipe downstream from the compressor outlet of the supercharger, When the engine required supercharging pressure is high, the supercharging pressure by the supercharger is set using a relative pressure detected at a predetermined location of the intake pipe downstream from the compressor outlet of the supercharger. An internal combustion engine characterized by that.   An exhaust gas recirculation system including an EGR flow path for recirculating exhaust gas to the intake system, and a throttle valve disposed between the EGR flow path and the merged portion of the intake pipe and the compressor outlet of the supercharger; When the engine required supercharging pressure is low, the supercharging pressure by the supercharger is set so that the absolute pressure detected between the compressor outlet and the throttle valve matches a target value. The internal combustion engine according to claim 1, wherein the internal combustion engine is set. When the opening degree of the throttle valve exceeds a predetermined amount, it is determined that the engine required supercharging pressure is high. When the opening degree of the throttle valve is equal to or less than the predetermined amount, the engine required supercharging pressure is low. The internal combustion engine according to claim 2, wherein the internal combustion engine is determined.

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