JP5034849B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  In an internal combustion engine, the exhaust valve of each cylinder is sequentially opened and exhaust gas is discharged into the exhaust manifold, thereby pulsating the exhaust manifold pressure. On the other hand, the intake manifold pressure is substantially constant. The exhaust manifold pressure at the valley of the pulsation is lower than the intake manifold pressure depending on operating conditions.

  In JP-A-11-324746 and JP-A-10-176558, the pulsation valley of the exhaust manifold pressure coincides with the valve overlap period in which the exhaust valve opening period and the intake valve opening period overlap. A technique for improving the intake air amount by controlling in such a manner is disclosed. According to this technique, the exhaust manifold pressure can be made lower than the intake manifold pressure during the valve overlap period. As a result, fresh air easily flows into the cylinder from the intake valve, and burned gas in the cylinder can be reliably driven out to the exhaust valve by the fresh air flowing from the intake valve. That is, the scavenging effect can be exhibited. As a result, the amount of residual gas is reduced, and the amount of fresh air sucked into the cylinder can be improved. That is, the filling efficiency can be improved.

Japanese Patent Laid-Open No. 11-324746 Japanese Patent Laid-Open No. 10-176558 JP 2004-257306 A Japanese Utility Model Publication No. 6-40343

  By the way, an internal combustion engine (particularly a diesel engine) having an EGR passage for returning a part of exhaust gas in the exhaust manifold to an intake passage is known. Such an internal combustion engine often further includes an EGR cooler for cooling the EGR gas in the middle of the EGR passage. According to the knowledge of the present inventors, the internal combustion engine having such an EGR path has a problem that it is difficult to exert the effect of the charging efficiency improvement control using the pulsation of the exhaust manifold pressure as described above. The reason is considered as follows.

  When the internal volume of the exhaust manifold is large, the pulsation of the exhaust manifold pressure is weakened and the amplitude thereof is reduced. In an internal combustion engine having an EGR path, the EGR passage and the EGR cooler communicate with the exhaust manifold, so that the volume of the exhaust manifold is substantially enlarged by the volume of the EGR passage and the EGR cooler. As a result, the amplitude of the pulsation of the exhaust manifold pressure becomes smaller, and the pulsation valley becomes shallower. For this reason, the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is reduced. Therefore, the scavenging effect is not sufficiently exhibited, and the filling efficiency is hardly improved.

  The present invention has been made in view of the above points, and even in an internal combustion engine equipped with an EGR passage and an EGR cooler, an internal combustion engine that can sufficiently exhibit the effect of the charging efficiency improvement control utilizing the exhaust pressure pulsation. An object of the present invention is to provide an engine control device.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
In addition to providing a valve overlap period in which the intake valve opening period and the exhaust valve opening period of the internal combustion engine overlap with each other, the charging efficiency improvement control is performed so that the timing at which the pulsation of the exhaust manifold pressure becomes a valley coincides with the valve overlap period. Viable filling efficiency improvement means;
Differential pressure determination means for determining whether or not the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is less than a predetermined value;
An exhaust system volume reducing means for reducing an exhaust system volume that is a volume of a space in the exhaust manifold and communicating with the exhaust manifold when the differential pressure is determined to be less than the predetermined value;
It is characterized by providing.

The second invention is the first invention, wherein
An EGR passage for recirculating exhaust gas of the internal combustion engine to an intake passage;
An EGR cooler for cooling EGR gas passing through the EGR passage;
An EGR control valve that is installed downstream of the EGR cooler and controls the amount of EGR;
An EGR passage shut-off valve capable of shutting off the EGR passage on the upstream side of the EGR cooler;
With
The exhaust system volume reducing means reduces the exhaust system volume by closing the EGR passage shut-off valve.

The third invention is the second invention, wherein
A bypass passage that allows EGR gas to flow downstream of the EGR passage without passing through the EGR cooler;
The EGR passage shut-off valve includes a shut-off position for shutting off the EGR passage upstream of the EGR cooler and the bypass passage, a cooler position for passing EGR gas through the EGR cooler, and a bypass position for passing EGR gas through the bypass passage. It has the valve body which displaces to.

Moreover, 4th invention is set in 1st invention,
The internal combustion engine has a plurality of exhaust valves in at least one cylinder, and independent exhaust passages are formed from the cylinder head to the exhaust manifold for each of the exhaust valves.
An independent exhaust passage shutoff valve capable of shutting off the other independent exhaust passage in the vicinity of the downstream end of at least one of the plurality of independent exhaust passages of the same cylinder;
The exhaust system volume reducing means reduces the exhaust system volume by closing the independent exhaust passage shut-off valve.

The fifth invention is a control device for an internal combustion engine,
An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
In addition to providing a valve overlap period in which the intake valve opening period and the exhaust valve opening period of the internal combustion engine overlap with each other, the charging efficiency improvement control is performed so that the timing at which the pulsation of the exhaust manifold pressure becomes a valley coincides with the valve overlap period. Viable filling efficiency improvement means;
An EGR passage for recirculating exhaust gas of the internal combustion engine to an intake passage;
An EGR cooler for cooling EGR gas passing through the EGR passage;
A bypass passage for allowing EGR gas to flow downstream of the EGR passage without passing through the EGR cooler;
A valve body that is displaced into a blocking position for blocking the EGR passage upstream of the EGR cooler and the bypass passage, a cooler position for passing EGR gas through the EGR cooler, and a bypass position for passing EGR gas through the bypass passage. An EGR passage shut-off valve having
When the engine load exceeds a predetermined high load judgment value, the exhaust system volume, which is the volume of the space inside the exhaust manifold and the space communicating therewith, is moved by moving the valve body of the EGR passage cutoff valve to the cutoff position. Exhaust system volume reducing means for reducing;
It is characterized by providing.

The sixth invention is the third or fifth invention, wherein
The EGR cooler has a cooler inlet, a cooler outlet adjacent to the cooler inlet, and an EGR gas outflow direction is opposite to an EGR gas inflow direction to the cooler inlet;
The EGR passage shut-off valve is
An inlet through which EGR gas flows,
An outlet through which EGR gas flows out;
An upstream chamber communicating with both the inlet and the cooler inlet;
A downstream chamber communicating with both the outlet and the cooler outlet;
A bypass opening for communicating the upstream chamber and the downstream chamber;
Have
The valve body is configured by a swing valve that can swing around a rotating shaft located on the opposite side of the EGR cooler through the bypass opening,
The swing valve includes a blocking position for blocking the inlet, a cooler position for introducing the EGR gas in the upstream chamber into the cooler inlet by blocking the bypass opening, and the inlet from the inlet through the bypass opening. It is possible to displace to a bypass position that allows flow to the outlet.

The seventh invention is the third, fifth or sixth invention, wherein
The blocking position is between the cooler position and the bypass position.

The eighth invention is the third, fifth or sixth invention, wherein
The shut-off position is outside the cooler position and the bypass position.

The ninth invention is a control device for an internal combustion engine,
An internal combustion engine having a plurality of exhaust valves in at least one cylinder, and an independent independent exhaust passage extending from the cylinder head to the exhaust manifold for each of the exhaust valves;
In addition to providing a valve overlap period in which the intake valve opening period and the exhaust valve opening period of the internal combustion engine overlap with each other, the charging efficiency improvement control is performed so that the timing at which the pulsation of the exhaust manifold pressure becomes a valley coincides with the valve overlap period. Viable filling efficiency improvement means;
An independent exhaust passage shut-off valve capable of shutting off the other independent exhaust passage in the vicinity of the downstream end of at least one of the plurality of independent exhaust passages of the same cylinder;
When the engine load exceeds a predetermined high load judgment value, the exhaust system volume reducing means for reducing the exhaust system volume, which is the volume of the space inside and communicating with the exhaust manifold, by closing the independent exhaust passage shut-off valve When,
It is characterized by providing.

The tenth invention is the fourth or ninth invention, wherein
An EGR passage for recirculating exhaust gas of the internal combustion engine to the intake passage;
The upstream end of the EGR passage is connected to the independent exhaust passage provided with the independent exhaust passage cutoff valve.

The eleventh aspect of the invention is the tenth aspect of the invention,
An independent exhaust passage shut-off valve group of a first system including the independent exhaust passage shut-off valve;
A second independent exhaust passage including a second independent exhaust passage cutoff valve capable of shutting off other independent exhaust passages while leaving the independent exhaust passage in a cylinder having an independent exhaust passage to which the upstream end of the EGR passage is connected. A shutoff valve group;
When the engine representative temperature is lower than a predetermined cold determination temperature and / or when the engine load is light load smaller than a predetermined light load determination value, the exhaust system is closed by closing the independent exhaust passage shut-off valve group of the second system. An exhaust temperature reduction suppressing means for reducing the surface area;
It is characterized by providing.

The twelfth invention is the tenth invention, in which
The independent exhaust passage cutoff valve of the cylinder having the independent exhaust passage to which the upstream end of the EGR passage is connected and the independent exhaust passage cutoff valve of other cylinders can be opened and closed independently.
A cylinder having an independent exhaust passage to which the upstream end of the EGR passage is connected when the engine representative temperature is lower than a predetermined cold determination temperature and / or when the engine load is lower than a predetermined light load determination value. An exhaust temperature reduction suppressing means for reducing the surface area of the exhaust system by closing the independent exhaust passage cutoff valves of the other cylinders while the independent exhaust passage cutoff valve is opened is provided.

A thirteenth aspect of the invention is a control device for an internal combustion engine,
An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
In addition to providing a valve overlap period in which the intake valve opening period and the exhaust valve opening period of the internal combustion engine overlap with each other, the charging efficiency improvement control is performed so that the timing at which the pulsation of the exhaust manifold pressure becomes a valley coincides with the valve overlap period. Viable filling efficiency improvement means;
A valve body that is displaceable to a normal position and an exhaust system volume reduction position that reduces an exhaust system volume that is a volume of a space in the exhaust manifold and communicating with the exhaust manifold;
Valve body pressing means for pressing the valve body from the normal position to the exhaust system volume reduction position by the exhaust pressure of the internal combustion engine;
Biasing means for biasing the valve body in a direction to return the exhaust system volume reduction position to the normal position;
With
When the exhaust pressure exceeds a threshold value, the exhaust system volume is reduced by the valve body being pressed by the exhaust pressure and moving from the normal position to the exhaust system volume reduction position. .

The fourteenth invention is the thirteenth invention, in which
An EGR passage for recirculating exhaust gas of the internal combustion engine to the intake passage;
When the valve body moves to the exhaust system volume reduction position, the valve body blocks the EGR passage in the vicinity of the upstream end of the EGR passage.

  According to the first invention, when the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is less than a predetermined value, the exhaust system volume can be reduced. By reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation increases, and the exhaust manifold pressure at the pulsation valley can be lowered. For this reason, since the differential pressure between the intake manifold pressure and the exhaust manifold pressure during the valve overlap period increases, the scavenging effect can be sufficiently exerted, and the charging efficiency (air amount) can be sufficiently improved.

  According to the second invention, when the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is less than a predetermined value, the EGR passage shut-off valve disposed upstream of the EGR cooler is closed. Thus, the exhaust system volume can be reduced. Further, in a situation where the differential pressure is sufficiently large and the effect of the charging efficiency improvement control is sufficiently exerted, it is possible to avoid blocking the EGR path and continue the EGR. For this reason, the advantages of EGR such as emission reduction can be enjoyed in a wide range.

  According to the third aspect of the present invention, both the switching of whether or not to block the EGR passage and the switching of passing the EGR gas through the EGR cooler or the bypass passage when the EGR gas is recirculated are performed with one valve body. Can be done by. For this reason, the EGR device can be simplified and miniaturized.

  According to the fourth aspect of the invention, when the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is less than a predetermined value, the exhaust system volume is reduced by closing the independent exhaust passage shut-off valve. be able to.

  According to the fifth aspect of the present invention, the exhaust system volume can be reduced by closing the EGR passage shut-off valve disposed on the upstream side of the EGR cooler at the time of high load. By reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation increases, and the exhaust manifold pressure at the pulsation valley can be lowered. For this reason, since the differential pressure between the intake manifold pressure and the exhaust manifold pressure during the valve overlap period increases, the scavenging effect can be sufficiently exerted, and the charging efficiency (air amount) can be sufficiently improved. Further, in the EGR passage shut-off valve, both the switching of whether or not the EGR passage is shut off and the switching of whether the EGR gas is passed through the EGR cooler or the bypass passage when the EGR gas is recirculated are performed by one valve. Can be done by the body. For this reason, the EGR device can be simplified and miniaturized.

  According to the sixth aspect, when bypassing the EGR cooler, the EGR gas can be bypassed through the bypass opening provided in the EGR passage shutoff valve. For this reason, it is not necessary to provide the bypass passage as a separate pipe line, and the EGR device can be simplified and downsized.

  According to the seventh aspect, since the shut-off position is between the cooler position and the bypass position, the swing valve can quickly move to the shut-off position from the cooler position or the bypass position. it can. For this reason, the effect of the filling efficiency improvement control can be quickly increased at the start of acceleration. Therefore, the engine torque can be increased quickly and an excellent acceleration response can be obtained.

  According to the eighth aspect of the invention, since the shut-off position is outside the cooler position and the bypass position, the flow of EGR gas is momentarily switched between the state in which the EGR gas is passed through the EGR cooler and the state in which the EGR cooler is bypassed. There will be no breaks. For this reason, smooth switching can be performed.

  According to the ninth aspect of the present invention, the exhaust system volume can be reduced by the amount of the independent exhaust passage blocked by the independent exhaust passage shut-off valve by closing the independent exhaust passage shut-off valve at the time of high load. . By reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation increases, and the exhaust manifold pressure at the pulsation valley can be lowered. For this reason, since the differential pressure between the intake manifold pressure and the exhaust manifold pressure during the valve overlap period increases, the scavenging effect can be sufficiently exerted, and the charging efficiency (air amount) can be sufficiently improved.

  According to the tenth aspect, when the independent exhaust passage shut-off valve is closed, the exhaust system volume can be further reduced by the amount of the EGR path. For this reason, the amplitude of the exhaust manifold pressure pulsation can be further increased, and the charging efficiency (air amount) can be further improved.

  According to the eleventh aspect of the present invention, the exhaust system surface area can be reduced by closing the independent exhaust passage shutoff valve group of the second system during cold or light loads. As a result, the amount of heat escaping from the exhaust gas to the outside can be reduced, so that the temperature of the exhaust gas flowing into the exhaust purification catalyst can be increased, contributing to early activation of the exhaust purification catalyst or maintenance of the activation temperature. Further, EGR is required during cold or light load, but the EGR can be executed because the independent exhaust passage shut-off valve of the independent exhaust passage connected to the upstream end of the EGR passage is open.

  According to the twelfth aspect of the present invention, during cold or light load, the independent exhaust passage shutoff valves of other cylinders remain open while the independent exhaust passage shutoff valve of the cylinder having the independent exhaust passage connected to the upstream end of the EGR passage is open. By closing the valve, the exhaust system surface area can be reduced. As a result, the amount of heat escaping from the exhaust gas to the outside can be reduced, so that the temperature of the exhaust gas flowing into the exhaust purification catalyst can be increased, contributing to early activation of the exhaust purification catalyst or maintenance of the activation temperature. Further, EGR is required during cold or light load, but the EGR can be executed because the independent exhaust passage shut-off valve of the independent exhaust passage connected to the upstream end of the EGR passage is open.

  According to the thirteenth invention, the exhaust system volume is automatically reduced by providing the valve body that moves from the normal position to the exhaust system volume reduction position by the exhaust pressure at the time of high load when the exhaust pressure becomes high. be able to. By reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation increases, and the exhaust manifold pressure at the pulsation valley can be lowered. For this reason, since the differential pressure between the intake manifold pressure and the exhaust manifold pressure during the valve overlap period increases, the scavenging effect can be sufficiently exerted, and the charging efficiency (air amount) can be sufficiently improved. Further, since an actuator and control for driving the valve body are unnecessary, the system can be simplified and the cost can be reduced.

  According to the fourteenth aspect, the exhaust system volume is reduced by providing the valve body that automatically shuts off the EGR passage in the vicinity of the upstream end of the EGR passage by the exhaust pressure when the exhaust pressure becomes high. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a four-cycle diesel engine (compression ignition internal combustion engine) 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Although the diesel engine 10 of the present embodiment is an in-line four-cylinder type, the number of cylinders and the cylinder arrangement of the diesel engine in the present invention are not limited to this.

  Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. In the common rail 14, high-pressure fuel pressurized by the supply pump 16 is stored. Then, fuel is supplied from the common rail 14 to the injectors 12 of each cylinder. The exhaust gas discharged from each cylinder is collected by the exhaust manifold 20 and flows into the exhaust passage 18.

  The diesel engine 10 includes a turbocharger 24. The turbocharger 24 includes a turbine 24a that is operated by a flow of exhaust gas, and a compressor 24b that is driven by the turbine 24a and compresses intake air.

  The turbine 24 a of the turbocharger 24 is disposed in the middle of the exhaust passage 18. A DPF 26 for capturing PM (Particulate Matter) in the exhaust gas is installed in the exhaust passage 18 on the downstream side of the turbine 24a. In addition to the DPF 26, the exhaust passage 18 may be provided with a catalyst for purifying harmful components in the exhaust gas. Alternatively, a catalyst component may be supported on the DPF 26.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air sucked through the air cleaner 30 is compressed by the compressor 24 b of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by the intake manifold 34 and flows into each cylinder.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of an EGR passage 40 is connected to the intake passage 28 in the vicinity of the intake manifold 34. The other end of the EGR passage 40 is connected to the exhaust manifold 20 of the exhaust passage 18. In this system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed.

  An EGR cooler 42 for cooling the exhaust gas (EGR gas) passing through the EGR passage 40 is provided in the middle of the EGR passage 40. An EGR valve 44 is provided downstream of the EGR cooler 42 in the EGR passage 40. By changing the opening degree of the EGR valve 44, the amount of exhaust gas passing through the EGR passage 40, that is, the amount of external EGR can be adjusted.

  Further, a location upstream of the EGR cooler 42 and a location downstream of the EGR passage 40 are connected by a bypass passage 46. A flow path switching valve 48 is installed at a connection portion between the upstream end of the bypass passage 46 and the EGR passage 40. The flow path switching valve 48 includes a state in which EGR gas flows to the EGR cooler 42 (hereinafter referred to as “cooler-passed state”), a state in which EGR gas flows to the bypass passage 46 (hereinafter referred to as “bypass state”), and EGR gas to EGR. It is possible to switch between three states: a state where the air does not flow through either the cooler 42 or the bypass passage 46, that is, a state where the EGR passage 40 is blocked (hereinafter referred to as “blocking state”).

  When the EGR gas is cooled by the EGR cooler 42 at a light load, the in-cylinder temperature becomes too low, and the combustion deteriorates and the HC emission amount is likely to increase. Therefore, in the system of this embodiment, such a problem can be avoided by flowing the EGR gas through the bypass passage 46 without passing through the EGR cooler 42 at a light load.

  Further, the system of this embodiment includes an accelerator opening sensor 66 that detects the amount of depression of the accelerator pedal (accelerator opening) of a vehicle on which the diesel engine 10 is mounted, and an intake pressure that detects an intake manifold pressure (intake pressure). A sensor 68, an exhaust pressure sensor 70 for detecting an exhaust manifold pressure (exhaust pressure), and an ECU (Electronic Control Unit) 50 are further provided. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 controls the operating state of the diesel engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

  FIG. 2 is a view showing a cross section of one cylinder of the diesel engine 10 in the system shown in FIG. Hereinafter, the diesel engine 10 will be further described. As shown in FIG. 2, a crank angle sensor 62 that detects a rotation angle of the crankshaft 60, that is, a crank angle, is attached in the vicinity of the crankshaft 60 of the diesel engine 10. The crank angle sensor 62 is connected to the ECU 50. The ECU 50 can also calculate the engine speed based on the detection signal of the crank angle sensor 62.

  The diesel engine 10 also includes an intake variable valve operating device 54 that varies the valve opening characteristics of the intake valve 52 and an exhaust variable valve operating device 58 that varies the valve opening characteristics of the exhaust valve 56. The specific configurations of the intake variable valve operating device 54 and the exhaust variable valve operating device 58 are not particularly limited, and a phase variable mechanism that continuously varies the opening / closing timing by changing the phase of the camshaft. In addition, a mechanism for driving the cam with an electric motor, an electromagnetically driven valve, a hydraulically driven valve, or the like can be used.

  According to the intake variable valve operating device 54 and the exhaust variable valve operating device 58, the valve overlap period in which the valve opening period of the exhaust valve 56 and the valve opening period of the intake valve 52 overlap (hereinafter simply referred to as “valve overlap period”). ) Can be changed.

[Features of Embodiment 1]
The system according to the present embodiment improves the charging efficiency by improving the charging efficiency η _v (in-cylinder air amount) of the diesel engine 10 by using the pulsation of the exhaust manifold pressure in a predetermined operation region (for example, a low rotation high load region). Control can be executed. FIG. 3 is a diagram showing the relationship between the intake manifold pressure and the exhaust manifold pressure and the crank angle during the execution of the charging efficiency improvement control.

  As shown in FIG. 3, in the charging efficiency improvement control, the intake variable valve operating device 54 and the exhaust variable valve operating device 58 are controlled so that the valve overlap period is sufficiently long.

  Further, as shown in FIG. 3, the intake manifold pressure is substantially constant regardless of the crank angle. On the other hand, the exhaust manifold pressure pulsates (periodically varies) as the exhaust gas is intermittently discharged from the exhaust valve 56 of each cylinder.

As the opening timing of the exhaust valve 56 is later, the timing at which the exhaust gas is discharged into the exhaust manifold 20 is delayed, so the waveform of the exhaust manifold pressure pulsation shifts to the right in FIG. That is, the waveform of the exhaust manifold pressure pulsation moves to the left and right in FIG. 3 by changing the opening timing of the exhaust valve 56. Therefore, by setting the opening timing of the exhaust valve 56 to an appropriate timing, the valley portion of the exhaust manifold pressure pulsation can coincide with the valve overlap period as shown in FIG. In the charging efficiency improvement control, the exhaust variable valve operating device 58 is controlled so that the opening timing of the exhaust valve 56 is realized, so that the valley portion of the exhaust manifold pressure pulsation coincides with the valve overlap period. . As a result, the exhaust manifold pressure can be made lower than the intake manifold pressure during the valve overlap period. Accordingly, fresh air easily flows into the cylinder, and a scavenging effect for quickly expelling burned gas in the cylinder to the exhaust port 22 by the new air that has flowed in is obtained. By executing the charging efficiency improvement control in this way, the residual gas amount can be sufficiently reduced, and the amount of fresh air filled in the cylinder can be increased accordingly. That is, the filling efficiency η _v can be increased. As a result, the torque of the diesel engine 10 can be improved.

  By the way, the exhaust manifold pressure indicated by the dotted line in FIG. 3 is a waveform when the flow path switching valve 48 is in the state of being passed through the cooler, that is, when the EGR gas is allowed to flow to the EGR cooler 42. On the other hand, the exhaust manifold pressure indicated by the solid line in FIG. 3 is a waveform when the flow path switching valve 48 is shut off.

  The pulsation of the exhaust manifold pressure becomes weaker as the volume of the exhaust manifold 20 and the volume of the space communicating with the exhaust manifold 20 (hereinafter collectively referred to as “exhaust system volume”) are increased. This is because even if the same amount of exhaust gas is discharged from the exhaust valve 56, the exhaust manifold pressure is less likely to increase as the exhaust system volume increases.

  In the diesel engine 10 of the present embodiment, when the flow path switching valve 48 is in the state via the cooler, the EGR passage 40 and the EGR cooler 42 communicate with the exhaust manifold 20, so the volume of the EGR passage 40 and the EGR cooler 42 is divided. Only the exhaust system volume is increased. For this reason, as shown by the dotted line in FIG. 3, the exhaust manifold pressure pulsation tends to be weakened, and the amplitude tends to be small. As a result, since the differential pressure (A in FIG. 3) between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley tends to be small, the scavenging effect is not sufficiently exhibited, and the effect of the charging efficiency improvement control is small. Easy to be. That is, it is difficult to sufficiently improve the engine torque.

  Further, when the flow path switching valve 48 is in the bypass state, the volume of the bypass passage 46 is added to the exhaust system volume instead of the EGR cooler 42, so that the effect of the charging efficiency improvement control is reduced as described above. easy.

  On the other hand, when the flow path switching valve 48 is shut off, the EGR passage 40, the EGR cooler 42, and the bypass passage 46 (hereinafter collectively referred to as “EGR passage”) are separated from the exhaust manifold 20, and their volumes are reduced. Can be prevented from being added to the exhaust system volume, so that the exhaust system volume can be reduced. Therefore, as shown by the solid line in FIG. 3, the exhaust manifold pressure exhausted from the exhaust valve 56 increases the exhaust manifold pressure at the initial stage of the exhaust stroke, and as a reaction, the exhaust manifold pressure at the late stage of the exhaust stroke may be lowered. it can. That is, the pulsation of the exhaust manifold pressure can be increased and the amplitude thereof can be increased. For this reason, the differential pressure (B in FIG. 3) between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley can be increased, and the scavenging effect can be sufficiently exhibited. As a result, the effect of the charging efficiency improvement control is greatly exerted, and the engine torque can be sufficiently improved.

  Therefore, in this embodiment, when the charging efficiency improvement control is executed, it is determined that the difference between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is small, and the effect of the charging efficiency improvement control is not sufficiently exhibited. In this case, the flow rate switching valve 48 is switched to the shut-off state so that the effect of the charging efficiency improvement control is sufficiently exerted.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 4, first, the intake manifold pressure detected by the intake pressure sensor 68 is acquired (S1). Next, the exhaust manifold pressure at the valley of the pulsation is acquired based on the detection signal of the exhaust pressure sensor 70 (S2).

  Subsequently, it is determined whether or not the differential pressure between the intake manifold pressure acquired in S1 and the exhaust manifold pressure in the pulsation valley acquired in S2 is smaller than a predetermined determination value (S3). . This determination value is a value set in advance as a boundary on whether or not the effect of the filling efficiency improvement control is sufficiently exhibited. In S3, when it is recognized that the differential pressure is smaller than the determination value, it can be determined that the effect of the filling efficiency improvement control is not sufficiently exhibited. Therefore, in this case, the EGR path is blocked from the exhaust manifold 20 by switching the flow path switching valve 48 to the cutoff state (S4). As a result, the exhaust system volume is reduced and the amplitude of the exhaust manifold pressure pulsation can be increased, so that the effect of the charging efficiency improvement control can be improved and the engine torque can be sufficiently increased.

  On the other hand, if it is determined in S3 that the differential pressure is greater than or equal to the determination value, it can be determined that the effect of the filling efficiency improvement control is sufficiently exhibited. Therefore, in this case, since it can be determined that it is not necessary to block the EGR route, the process of S4 is not executed.

  As described above, according to the present embodiment, in a situation where the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is small and the effect of the charging efficiency improvement control is not sufficiently exhibited, By shutting off the EGR path from the exhaust manifold 20 and reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation can be increased, thereby improving the effect of the charging efficiency improvement control.

  Also, in a situation where the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation trough is sufficiently large and the effect of the charging efficiency improvement control is sufficiently exerted, avoiding blocking the EGR path, EGR can be continued. For this reason, the advantages of EGR such as emission reduction can be enjoyed in a wide range.

  By the way, as a configuration for blocking the EGR path from the exhaust manifold 20, a valve (flow path switching valve 48) is provided on the upstream side of the EGR cooler 42 separately from the configuration of the present embodiment, that is, the EGR valve 44. In addition to the configuration in which the valve is closed, a configuration in which the EGR valve itself is disposed on the upstream side of the EGR cooler 42 (the inlet side of the EGR passage 40) and the EGR path is closed by closing the EGR valve is also conceivable. However, when the EGR valve is arranged on the upstream side of the EGR cooler 42, the distance from the intake passage 28 to the EGR valve becomes longer, so the EGR gas inflow into the intake passage 28 after changing the opening of the EGR valve. There will be a delay before the quantity actually changes. As a result, it becomes difficult to accurately control the EGR amount. On the other hand, in this embodiment, since the EGR valve 44 is on the downstream side of the EGR cooler 42, the control delay of the EGR amount can be suppressed, and highly accurate EGR control can be performed.

  In the present embodiment, the exhaust manifold pressure is detected by the exhaust pressure sensor 70, but the method for acquiring the exhaust manifold pressure is not limited to this. For example, since there is a correlation between the pressure on the downstream side of the turbine 24a and the exhaust manifold pressure, the exhaust manifold pressure may be calculated based on the detection value of the pressure sensor provided on the downstream side of the turbine 24a. . Also, an estimated value of the exhaust manifold pressure calculated based on the intake air amount, the exhaust temperature, and the like can be used. In this case, the intake air amount can be detected by the air flow meter 38, and the exhaust temperature is detected by an exhaust temperature sensor (not shown) or estimated based on the detected engine speed and the engine load (fuel injection amount). be able to.

  In the first embodiment described above, the ECU 50 executes the above-described filling efficiency improvement control, so that the “filling efficiency improvement means” in the first invention executes the processes of S1 to S3. The “exhaust system volume reducing means” according to the first aspect of the present invention is realized by executing the process of S4. The flow path switching valve 48 corresponds to the “EGR passage cutoff valve” in the second aspect of the invention.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 5 to FIG. 8. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit. The system configuration of the present embodiment is the same as that of the first embodiment described above except that the structures of the EGR cooler, the bypass passage, and the EGR passage cutoff valve are different.

  FIG. 5 is a cross-sectional view showing structures of the EGR cooler, the bypass passage, and the EGR passage cutoff valve according to Embodiment 2 of the present invention. As shown in FIG. 5, the EGR cooler 42 ′ in the present embodiment has a cooler inlet 71 and a cooler outlet 72 adjacent to the cooler inlet 71. The EGR gas that has flowed in from the cooler inlet 71 flows to make a U-turn in the EGR cooler 42 ′, and flows out from the cooler outlet 72. That is, the EGR gas inflow direction to the cooler inlet 71 and the EGR gas outflow direction from the cooler outlet 72 are opposite to each other. The outward path that continues from the cooler inlet 71 and the return path that continues to the cooler outlet 72 are separated by a partition wall 73. Heat exchangers 74 and 75 are installed on the forward path and the return path, respectively. Engine cooling water flows through the heat exchangers 74 and 75, and the EGR gas is cooled by the cooling water.

  An EGR passage shut-off valve 76 is provided in the vicinity of the EGR cooler 42 '. The EGR passage shut-off valve 76 includes an inlet 77 through which EGR gas flows from the upstream EGR passage 40, an outlet 78 through which EGR gas flows into the downstream EGR passage 40, and both the inlet 77 and the cooler inlet 71. An upstream chamber 79 that communicates, a downstream chamber 80 that communicates with both the outlet 78 and the cooler outlet 72, a bypass opening 81 that communicates the upstream chamber 79 and the downstream chamber 80, and a swing valve 82 are provided.

  The bypass opening 81 has a function similar to that of the bypass passage 46 of the first embodiment, that is, a function of flowing EGR gas downstream of the EGR passage 40 without passing through the EGR cooler 42 ′.

  The swing valve 82 is installed to be swingable about a rotation shaft 83 located on the opposite side of the EGR cooler 42 ′ via the bypass opening 81. The swing valve 82 includes a cooler position for passing EGR gas through the EGR cooler 42 ', a bypass position for passing EGR gas downstream of the EGR passage 40 without passing through the EGR cooler 42', and upstream of the EGR cooler 42 '. It can be displaced to a blocking position for blocking the EGR passage 40. The swing valve 82 is driven by an actuator (not shown) such as a negative pressure actuator or an electric motor, and is displaced to the above three positions. A contact surface 84 is formed on the inner wall of the upstream chamber 79 so that the tip of the swing valve 82 contacts when the swing valve 82 is in the blocking position.

  FIG. 5 shows a state where the swing valve 82 is at the cooler position, that is, a state via the cooler. In this state, the tip of the swing valve 82 faces the end surface of the partition wall 73 through a minute clearance. As a result, the bypass opening 81 is blocked by the swing valve 82. For this reason, the EGR gas that has flowed into the upstream chamber 79 from the inlet 77 is introduced into the cooler inlet 71, and sequentially passes through the heat exchangers 74 and 75, the cooler outlet 72, and the downstream chamber 80, and then passes through the EGR from the outlet 78. It flows out downstream of the passage 40.

  FIG. 6 is an enlarged view showing the vicinity of the clearance between the swing valve 82 and the partition wall 73 when the swing valve 82 is in the cooler position. As shown in this figure, a flange 85 may be provided at the end of the partition wall 73. By providing the flange 85, the width of the end face of the partition wall 73 is enlarged, so that the clearance can be prevented from increasing even if the stop position of the swing valve 82 is slightly deviated. For this reason, the sealing performance between the swing valve 82 and the partition wall 73 can be improved.

  FIG. 7 shows a state where the swing valve 82 is in the bypass position, that is, a bypass state. In this state, the bypass opening 81 is opened. Therefore, the EGR gas that has flowed into the upstream chamber 79 from the inflow port 77 passes through the bypass opening 81 as it is to the downstream chamber 80 and flows out from the outflow port 78 to the downstream side of the EGR passage 40. When the load is light, the EGR can be performed without passing through the EGR cooler 42 ′ by setting the swing valve 82 to such a bypass position. For this reason, the deterioration of combustion due to the in-cylinder temperature becoming too low can be avoided, and the HC emission amount can be reduced. Further, according to the present embodiment, it is not necessary to separately provide a pipe line such as the bypass passage 46 in FIG. 1, and the EGR gas is bypassed through the bypass opening 81 provided in the EGR passage shut-off valve 76. Can do. For this reason, the EGR device can be simplified and miniaturized.

  FIG. 8 shows a state where the swing valve 82 is in the cutoff position, that is, a cutoff state. In this state, the tip of the swing valve 82 abuts against the abutment surface 84, whereby the inflow port 77 and the upstream chamber 79 are blocked by the swing valve 82. By adopting this state, it is possible to prevent the volume of the EGR cooler 42 ′ from being added to the exhaust system volume as in the first embodiment, and the exhaust system volume can be reduced. For this reason, the pulsation of the exhaust manifold pressure becomes strong, and the effect of the filling efficiency improvement control can be exerted greatly.

  As described above, according to the present embodiment, the single swing valve 82 can realize switching to the shut-off state in addition to switching between the state via the cooler and the bypass state. For this reason, the structure can be simplified and downsized.

  Further, in the present embodiment, with respect to the position of the swing valve 82, there is a blocking position shown in FIG. 8 outside the cooler position shown in FIG. 5 and the bypass position shown in FIG. For this reason, during the EGR, when switching between the cooler-passed state and the bypass state, the flow of EGR gas is not interrupted even for a moment, and smooth switching can be performed.

  Since this embodiment is the same as Embodiment 1 except for the points described above, further description is omitted. However, in the first embodiment, when it is determined that the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is small, the flow path switching valve 48 is closed to reduce the exhaust system volume. However, in this embodiment, it is not necessary to perform control based on the differential pressure. That is, in the present embodiment, when the engine load is high, that is, when the engine load (for example, accelerator opening, fuel injection amount, required torque, etc.) exceeds a predetermined high load determination value, the engine torque is increased. In addition, the exhaust system volume may be reduced by setting the swing valve 82 to the cutoff position. In this case, the high load determination value may be changed according to the engine speed.

  In the second embodiment described above, the bypass opening 81 is the “bypass passage” in the third and fifth inventions, and the swing valve 82 is the “valve element” in the third and fifth inventions. It corresponds.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 9 to FIG. 11. The description will focus on the differences from the above-described second embodiment, and the same matters will be described. Simplify or omit. This embodiment is the same as Embodiment 2 described above, except that the structure of the EGR passage cutoff valve is different.

  FIG. 9 is a cross-sectional view showing structures of the EGR cooler, the bypass passage, and the EGR passage cutoff valve according to Embodiment 3 of the present invention. As shown in FIG. 9, the EGR cooler 42 'in the present embodiment is the same as that in the second embodiment described above. On the other hand, the EGR passage cutoff valve 76 ′ in the present embodiment is different from the second embodiment described above in the arrangement of the bypass position and the cutoff position of the swing valve 82. FIG. 9 shows a state in which the swing valve 82 is at the cooler position, and this state is the same as in the second embodiment described above.

  FIG. 10 shows a state where the swing valve 82 is in the cutoff position, that is, a cutoff state. In this state, the tip of the swing valve 82 and the inner wall surface 85 of the upstream chamber 79 face each other with a minute clearance. As a result, the inflow port 77 is blocked by the swing valve 82. By adopting this state, it is possible to prevent the volume of the EGR cooler 42 ′ from being added to the exhaust system volume as in the first embodiment, and the exhaust system volume can be reduced. For this reason, the pulsation of the exhaust manifold pressure becomes strong, and the effect of the filling efficiency improvement control can be exerted greatly.

  When the swing valve 82 further rotates in the same direction from the cooler position beyond the shut-off position, the bypass position is reached. FIG. 11 shows a state where the swing valve 82 is in the bypass position, that is, a bypass state. In this state, since the bypass opening 81 is opened, the EGR gas flows downstream of the EGR passage 40 without passing through the EGR cooler 42 '.

  According to the present embodiment, with respect to the position of the swing valve 82, the blocking position (FIG. 10) is between the cooler position (FIG. 9) and the bypass position (FIG. 11). For this reason, both the rotation angle of the swing valve 82 from the cooler position to the shut-off position and the rotation angle of the swing valve 82 from the bypass position to the shut-off position can both be reduced (both about 45 °). Therefore, the swing valve 82 can be quickly moved to the shut-off position from either the cooler position or the bypass position. That is, it is possible to quickly switch to the shut-off state from either the state via the cooler or the bypass state.

  During normal operation of the diesel engine 10, EGR is normally executed, so the swing valve 82 is in either the cooler position or the bypass position. On the other hand, at the time of acceleration (at the time of high load), charging efficiency improvement control is executed, and the swing valve 82 moves to the cutoff position in order to enhance the effect of this charging efficiency improvement control. At this time, if the time required for the swing valve 82 to move from the cooler position or the bypass position to the shut-off position is long, it becomes late to increase the effect of the charging efficiency improvement control, that is, to sufficiently increase the engine torque. Therefore, it becomes difficult to obtain a good acceleration response. On the other hand, in this embodiment, since the swing valve 82 can be quickly moved from the cooler position to the shut-off position at the start of acceleration, the effect of the charging efficiency improvement control can be quickly increased. That is, the engine torque can be increased quickly. Therefore, an excellent acceleration response can be obtained.

  Since this embodiment is the same as Embodiment 2 described above except for the points described above, further description thereof is omitted.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. 12. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted. FIG. 12 is a diagram for explaining a system configuration according to the fourth embodiment of the present invention. As shown in FIG. 12, the diesel engine 10 of the present embodiment is provided with two exhaust valves 56 per cylinder. An exhaust passage extending from the exhaust port formed in the cylinder head 88 of the diesel engine 10 to the collecting portion of the exhaust manifold 20 is formed independently for each of the exhaust valves 56. This independent exhaust passage is referred to as an “independent exhaust passage” in this specification, and the independent exhaust passage communicating with one exhaust valve 56 of the two exhaust valves 56 of each cylinder is denoted by reference numeral 86 and the other exhaust valve 56. An independent exhaust passage communicating with is denoted by reference numeral 87.

  In the vicinity of the downstream end of the independent exhaust passage 86 of each cylinder, an independent exhaust passage shut-off valve 89 that can shut off the independent exhaust passage 86 is installed. That is, the independent exhaust passage shut-off valve 89 is disposed on the independent exhaust passage 86 and before the collective portion of the exhaust manifold 20. In the illustrated configuration, the independent exhaust passage shut-off valve 89 is a butterfly valve, but the valve type is not limited to this. The independent exhaust passage shutoff valve 89 for each cylinder is fixed to a common rotating shaft 90. When the rotary shaft 90 is driven by the actuator 91, the independent exhaust passage shutoff valve 89 of each cylinder is uniformly opened and closed. The operation of the actuator 91 is controlled by the ECU 50.

  The upstream end of the EGR passage 40 is connected to the middle of the independent exhaust passage 86 of the rightmost cylinder in FIG. When EGR is executed, the independent exhaust passage shut-off valve 89 for each cylinder is opened. Accordingly, since the exhaust gas also flows through the independent exhaust passage 86 of the rightmost cylinder in FIG. 12, the exhaust gas can be taken out into the EGR passage 40 as EGR gas.

  On the other hand, when the independent exhaust passage shutoff valve 89 of each cylinder is closed, the exhaust gas does not flow through the independent exhaust passage 86 of each cylinder, and the exhaust gas flows only through the independent exhaust passage 87. That is, when the independent exhaust passage shutoff valve 89 of each cylinder is closed, the independent exhaust passage 86 of each cylinder is shut off from the collecting portion of the exhaust manifold 20, and only the independent exhaust passage 87 communicates with the collecting portion of the exhaust manifold 20. For this reason, the volume of the independent exhaust passage 86 of each cylinder does not add to the exhaust system volume. Further, in this state, since the EGR passage 40 is also cut off from the collecting portion of the exhaust manifold 20, the volume of the EGR passage 40 and the EGR cooler 42 does not add to the exhaust system volume. For this reason, when the independent exhaust passage shutoff valve 89 of each cylinder is closed, the exhaust system is equivalent to the combined volume of the EGR passage 40, the EGR cooler 42, and the independent exhaust passage 86 of each cylinder, as compared with the normal time. The volume can be reduced. For this reason, during the execution of the charging efficiency improvement control, the pulsation of the exhaust manifold pressure can be increased by closing the independent exhaust passage shutoff valve 89 of each cylinder, so that the charging efficiency (air amount) can be further increased. it can. When the independent exhaust passage shutoff valve 89 for each cylinder is closed, the EGR valve 44 is also closed.

  Since this embodiment is the same as Embodiment 1 except for the points described above, further description is omitted. However, in the first embodiment, when it is determined that the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is small, the flow path switching valve 48 is closed to reduce the exhaust system volume. However, in this embodiment, it is not necessary to perform control based on the differential pressure. That is, in this embodiment, when the engine is in a high load state, that is, when the engine load (for example, accelerator opening, fuel injection amount, required torque, etc.) exceeds a predetermined high load determination value, the effect of the charging efficiency improvement control is achieved. Therefore, the exhaust system volume may be reduced by closing the independent exhaust passage shut-off valve 89 of each cylinder. In this case, the high load determination value may be changed according to the engine speed.

  In this embodiment, the independent exhaust passage shutoff valve 89 is provided in the independent exhaust passage 86 of all cylinders. However, in the present invention, the independent exhaust passage shutoff valve 89 is provided only in the independent exhaust passage 86 of some cylinders. May be. In that case, it is preferable to provide the independent exhaust passage shut-off valve 89 in the independent exhaust passage 86 connected to the EGR passage 40 so that the EGR passage can be shut off from the exhaust manifold 20 when the independent exhaust passage shut-off valve 89 is closed. .

Embodiment 5 FIG.
Next, the fifth embodiment of the present invention will be described with reference to FIG. 13. The description will focus on the differences from the fourth embodiment described above, and the same matters will be simplified or described. Omitted. FIG. 13 is a diagram for explaining a system configuration according to the fifth embodiment of the present invention. As shown in FIG. 13, in the diesel engine 10 of the present embodiment, as in the fourth embodiment, an independent exhaust passage shut-off valve 89 is installed in the independent exhaust passage 86 of each cylinder. The exhaust passage cutoff valve 89 is fixed to a common rotating shaft 90.

  Furthermore, in this embodiment, an independent exhaust passage shut-off valve 92 that can shut off the independent exhaust passage 87 is provided near the downstream end of the independent exhaust passage 87 of each cylinder. The independent exhaust passage shut-off valves 92 for these cylinders are fixed to a common rotating shaft 93. The actuator 94 can rotate the rotation shafts 90 and 93 independently. Thereby, the independent exhaust passage cutoff valve 89 and the independent exhaust passage cutoff valve 92 can be opened and closed independently. The operation of the actuator 94 is controlled by the ECU 50. At normal times, the independent exhaust passage shut-off valves 89 and 92 of each cylinder are controlled to be open.

  When the independent exhaust passage shut-off valve 92 is opened and the independent exhaust passage shut-off valve 89 is closed, the EGR passage 40, the EGR cooler 42, and the independent exhaust of each cylinder are compared with the normal state as in the fourth embodiment. The exhaust system volume can be reduced by an amount corresponding to the total volume of the passage 86. For this reason, during the execution of the charging efficiency improvement control, the pulsation of the exhaust manifold pressure can be increased by closing the independent exhaust passage shutoff valve 89 of each cylinder, so that the charging efficiency (air amount) can be further increased. it can.

  On the other hand, in the present embodiment, the control is performed so that the independent exhaust passage shut-off valve 89 is opened and the independent exhaust passage shut-off valve 92 is closed during cold or light load. In this state, in each cylinder, the exhaust gas does not flow through the independent exhaust passage 87 and the exhaust gas flows only through the independent exhaust passage 86. For this reason, compared with the normal time, the surface area of the exhaust system can be reduced by the surface area of the independent exhaust passage 87 of each cylinder. Further, in this state, since the independent exhaust passage shut-off valve 89 is open, the exhaust gas flows through the independent exhaust passage 86 of the rightmost cylinder in FIG. For this reason, EGR gas can be taken out from the EGR passage 40, and EGR can be executed.

  Since the exhaust temperature is likely to be low during cold or light loads, it may be difficult to activate the exhaust purification catalyst early or maintain the activation temperature. In the present embodiment, by closing the independent exhaust passage shut-off valve 92 during cold or light load, the exhaust system surface area is reduced by the surface area of the independent exhaust passage 87, so the amount of heat escaping from the exhaust gas to the outside is reduced. be able to. For this reason, the temperature of the exhaust gas flowing into the exhaust purification catalyst can be increased, which contributes to early activation of the exhaust purification catalyst or maintenance of the activation temperature. Further, although EGR is required during cold or light load, as described above, EGR can be executed even when the independent exhaust passage shut-off valve 92 is closed.

  In the present embodiment, whether or not the engine is cold can be determined based on whether the engine representative temperature (for example, cooling water temperature) is higher or lower than a predetermined determination temperature. Whether or not the vehicle is in a light load state can be determined based on whether the engine load (for example, accelerator opening, fuel injection amount, required torque, etc.) is higher or lower than a predetermined light load determination value.

  In the fifth embodiment described above, the independent exhaust passage cutoff valve 89 of each cylinder is the “first independent exhaust passage cutoff valve group” in the eleventh aspect of the invention, and the independent exhaust passage cutoff valve 92 is the eleventh of the eleventh aspect. In the invention, the “second independent exhaust passage shut-off valve” corresponds to the “second independent exhaust passage shut-off valve group” in the eleventh aspect of the invention. Further, the “exhaust temperature decrease suppressing means” according to the eleventh aspect of the present invention is realized by the ECU 50 controlling the actuator 94 so as to close the independent exhaust passage shutoff valve 92 of each cylinder during cold or light load. .

Embodiment 6 FIG.
Next, the sixth embodiment of the present invention will be described with reference to FIG. 14. The description will focus on the differences from the above-described fourth embodiment, and the same matters will be simplified or described. Omitted. FIG. 14 is a diagram for explaining a system configuration according to the sixth embodiment of the present invention. As shown in FIG. 14, in the diesel engine 10 of the present embodiment, an independent exhaust passage shutoff valve 89 is installed in the independent exhaust passage 86 of each cylinder. The independent exhaust passage shut-off valves 89 for each cylinder can be opened and closed independently of each other by driving an actuator (not shown) controlled by the ECU 50. Under normal conditions, the independent exhaust passage shutoff valves 89 for each cylinder are controlled to be open.

  When the independent exhaust passage shut-off valve 89 for each cylinder is closed, as in the fourth embodiment, the volume of the combined EGR passage 40, EGR cooler 42, and independent exhaust passage 86 for each cylinder is compared with that in the normal state. Only the exhaust system volume can be reduced. For this reason, during the execution of the charging efficiency improvement control, the pulsation of the exhaust manifold pressure can be increased by closing the independent exhaust passage shutoff valve 89 of each cylinder, so that the charging efficiency (air amount) can be further increased. it can.

  On the other hand, in the present embodiment, during cold or light load, the independent exhaust passage shutoff valve 89 of the # 1 cylinder (the rightmost cylinder in FIG. 14) to which the EGR passage 40 is connected is opened, and other cylinders are opened. Control is performed to close the independent exhaust passage shutoff valve 89 of (# 2 to # 4 cylinders). In this state, in the # 2 to # 4 cylinders, the exhaust gas does not flow through the independent exhaust passage 86, and the exhaust gas flows only through the independent exhaust passage 87. For this reason, the surface area of the exhaust system can be reduced by the surface area of the independent exhaust passages 86 of the # 2 to # 4 cylinders as compared with the normal time. In this state, the # 1 cylinder's independent exhaust passage shut-off valve 89 is opened, so that exhaust gas flows through the # 1 cylinder's independent exhaust passage 86. For this reason, EGR gas can be taken out from the EGR passage 40, and EGR can be executed.

  Since the exhaust temperature is likely to be low during cold or light loads, it may be difficult to activate the exhaust purification catalyst early or maintain the activation temperature. In this embodiment, by closing the # 2- # 4 cylinder independent exhaust passage shut-off valve 89 during cold or light load, the exhaust system surface area is increased by the surface area of the # 2- # 4 cylinder independent exhaust passage 86. Since the size is reduced, the amount of heat escaping from the exhaust gas to the outside can be reduced. For this reason, the temperature of the exhaust gas flowing into the exhaust purification catalyst can be increased, which contributes to early activation of the exhaust purification catalyst or maintenance of the activation temperature. Further, although EGR is required during cold or light load, as described above, EGR can be executed by opening the # 1 cylinder independent exhaust passage shutoff valve 89.

  In the present embodiment, whether or not the engine is cold can be determined based on whether the engine representative temperature (for example, cooling water temperature) is higher or lower than a predetermined determination temperature. Whether or not the vehicle is in a light load state can be determined based on whether the engine load (for example, accelerator opening, fuel injection amount, required torque, etc.) is higher or lower than a predetermined light load determination value.

  Further, in the illustrated configuration, each of the # 1 to # 4 cylinder independent exhaust passage shut-off valves 89 can be opened and closed independently, but in this embodiment, the # 1 cylinder # 1 independent exhaust passage shut-off valve 89 is provided. And the independent exhaust passage shut-off valves 89 for the # 2 to # 4 cylinders can be opened and closed independently of each other. That is, the independent exhaust passage shut-off valves 89 for the # 2 to # 4 cylinders may be configured to open and close uniformly.

  In the above-described sixth embodiment, the ECU 50 opens the # 1 cylinder independent exhaust passage shut-off valve 89 during cold or light load, and closes the # 2- # 4 cylinder independent exhaust passage shut-off valve 89. By controlling in this manner, the “exhaust temperature decrease suppressing means” in the twelfth aspect of the present invention is realized.

Embodiment 7 FIG.
Next, the seventh embodiment of the present invention will be described with reference to FIG. 15 to FIG. 17. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit. FIG. 15 is a diagram for explaining a system configuration according to the seventh embodiment of the present invention.

  The execution of the charging efficiency improvement control using the pulsation of the exhaust manifold pressure is necessary when the diesel engine 10 is operated at a high load, such as during acceleration. When the load is high, the external EGR is normally cut (EGR valve 44 is closed). Further, when the load is high, the fuel injection amount is increased, so that the exhaust temperature is also increased. For this reason, the exhaust manifold pressure increases as the engine load increases. Therefore, it can be said that the charging efficiency improvement control is executed when the exhaust manifold pressure is high.

  Therefore, in the present embodiment, when the exhaust manifold pressure becomes high, an EGR passage shut-off valve 95 that operates so as to automatically shut off the EGR passage 40 on the upstream side of the EGR cooler 42 by the exhaust manifold pressure is provided. It was.

  As shown in FIG. 15, in the present embodiment, an EGR passage cutoff valve 95 that can shut off the EGR passage 40 is provided in the middle of the EGR passage 40 on the upstream side of the EGR cooler 42. A valve driving passage 96 is branched from the exhaust manifold 20, and this valve driving passage 96 is connected to an EGR passage cutoff valve 95. Exhaust manifold pressure is supplied to the EGR passage cutoff valve 95 via the valve drive passage 96.

  FIG. 16 is a cross-sectional view of the vicinity of the EGR passage cutoff valve 95. As shown in the figure, the EGR passage shut-off valve 95 has a cylinder 97, in which a piston 98 and a spring 99 for urging the piston 98 upward in the figure are provided. It has been. A valve driving passage 96 communicates with the pressure chamber 100 surrounded by the cylinder 97 and the piston 98. As a result, the exhaust manifold pressure acts on the pressure chamber 100 via the valve drive passage 96. A partition plate 102 that can block the EGR passage 40 is connected to the piston 98 via a rod 101.

  FIG. 16 shows the state of the EGR passage cutoff valve 95 when the exhaust manifold pressure is low. In this state, the spring 99 is extended because the exhaust manifold pressure acting on the pressure chamber 100 has a weak force to push the piston 98 downward in the drawing. As a result, the partition plate 102 is retracted from the EGR passage 40, and the EGR passage 40 is opened.

  On the other hand, FIG. 17 shows a state of the EGR passage cutoff valve 95 when the exhaust manifold pressure is high. When the exhaust manifold pressure increases, the piston 98 moves downward in the figure against the biasing force of the spring 99 by the force exerted on the piston 98 by the exhaust manifold pressure in the pressure chamber 100. As a result, as shown in FIG. 17, the partition plate 102 enters the EGR passage 40 and blocks the EGR passage 40. In this state, the volume of the EGR passage 40 and the EGR cooler 42 is not added to the exhaust system volume, so that the exhaust system volume is reduced by the combined volume of the EGR passage 40 and the EGR cooler 42 compared to the normal time.

  When the exhaust manifold pressure exceeds a certain threshold value, the partition plate 102 of the EGR passage cutoff valve 95 moves from the normal position shown in FIG. 16 to the exhaust system volume reduction position shown in FIG. The threshold value is determined by the spring constant of the spring 99. The spring constant of the spring 99 is set so that the threshold value corresponds to the exhaust manifold pressure at the engine load at which the charging efficiency improvement control is started.

  According to such an EGR passage shut-off valve 95, when entering the operation region in which the charging efficiency improvement control is executed, the EGR passage 40 is automatically shut off by the increased exhaust manifold pressure to reduce the exhaust system volume. can do. As a result, the pulsation of the exhaust manifold pressure can be strengthened, so that the effect of the filling efficiency improvement control is enhanced and the filling efficiency (air amount) can be further increased.

  Further, in this embodiment, since an actuator and control for driving the EGR passage cutoff valve 95 are not required, the system can be simplified and the cost can be reduced.

  In the seventh embodiment described above, the partition plate 102 is the “valve element” in the thirteenth aspect of the invention, the piston 98 is the “valve element pressing means” in the thirteenth aspect of the invention, and the spring 99 is the thirteenth aspect. It corresponds to the “biasing means” in the invention.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the cross section of one cylinder of the diesel engine in the system shown in FIG. It is a figure which shows the relationship between the intake manifold pressure and exhaust manifold pressure in execution of filling efficiency improvement control, and a crank angle. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is sectional drawing which shows the structure of the EGR cooler in the Embodiment 2 of this invention, a bypass passage, and an EGR passage cutoff valve. It is a figure which expands and shows the clearance gap vicinity of a swing valve and a partition when a swing valve exists in a cooler position. It is a figure which shows the state which has the swing valve in the EGR channel | path cutoff valve of Embodiment 2 of this invention in a bypass position. It is a figure which shows the state which has the swing valve in the EGR channel | path cutoff valve of Embodiment 2 of this invention in the interruption | blocking position. It is sectional drawing which shows the structure of the EGR cooler in the Embodiment 3 of this invention, a bypass channel, and an EGR channel | path cutoff valve. It is a figure which shows the state in which the swing valve in the EGR channel | path cutoff valve of Embodiment 3 of this invention exists in the interruption | blocking position. It is a figure which shows the state which has the swing valve in the EGR channel | path cutoff valve of Embodiment 3 of this invention in a bypass position. It is a figure for demonstrating the system configuration | structure of Embodiment 4 of this invention. It is a figure for demonstrating the system configuration | structure of Embodiment 5 of this invention. It is a figure for demonstrating the system configuration | structure of Embodiment 6 of this invention. It is a figure for demonstrating the system configuration | structure of Embodiment 7 of this invention. It is sectional drawing of the EGR channel | path cutoff valve vicinity vicinity in Embodiment 7 of this invention. It is sectional drawing of the EGR channel | path cutoff valve vicinity vicinity in Embodiment 7 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 20 Exhaust manifold 22 Exhaust port 24 Turbocharger 24a Turbine 24b Compressor 26 DPF
28 Intake passage 34 Intake manifold 35 Intake port 36 Intake throttle valve 38 Air flow meter 40 EGR passage 42 EGR cooler 44 EGR valve 46 Bypass passage 48 Flow path switching valve 50 ECU
52 Intake valve 54 Intake variable valve operating device 56 Exhaust valve 58 Exhaust variable valve operating device 62 Crank angle sensor 64 Piston 68 Intake pressure sensor 70 Exhaust pressure sensor 71 Cooler inlet 72 Cooler outlet 73 Partition walls 74, 75 Heat exchanger 76 EGR passage shut off Valve 77 Inlet 78 Outlet 79 Upstream chamber 80 Downstream chamber 81 Bypass opening 82 Swing valve 83 Rotating shaft 84 Abutting surface 85 Inner wall surface 86, 87 Independent exhaust passage 88 Cylinder head 89, 92 Independent exhaust passage shut-off valve 90, 93 Rotation Shafts 91, 94 Actuator 95 EGR passage shutoff valve 96 Valve drive passage 97 Cylinder 98 Piston 99 Spring 100 Pressure chamber 101 Rod 102 Partition plate

Claims (14)

An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
The provided with a valve overlap period during which an exhaust valve open period overlap and the intake valve open period of the internal combustion engine, to match the timing of the pulsation of the exhaust manifold pressure is a valley to the valve overlap period, the valve overlap and viable charging efficiency enhancement means charging efficiency enhancement control you lower than the exhaust manifold pressure intake manifold pressure in the period,
Differential pressure determination means for determining whether or not the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is less than a predetermined value;
An exhaust system that reduces the exhaust system volume, which is the volume of the space in the exhaust manifold and the space communicating therewith, when the filling efficiency improvement control is executed and the differential pressure is determined to be less than the predetermined value Volume reduction means;
A control device for an internal combustion engine, comprising: An EGR passage for recirculating exhaust gas of the internal combustion engine to an intake passage;
An EGR cooler for cooling EGR gas passing through the EGR passage;
An EGR control valve that is installed downstream of the EGR cooler and controls the amount of EGR;
An EGR passage shut-off valve capable of shutting off the EGR passage on the upstream side of the EGR cooler;
With
2. The control device for an internal combustion engine according to claim 1, wherein the exhaust system volume reducing means reduces the exhaust system volume by closing the EGR passage shut-off valve. A bypass passage that allows EGR gas to flow downstream of the EGR passage without passing through the EGR cooler;
The EGR passage shut-off valve includes a shut-off position for shutting off the EGR passage upstream of the EGR cooler and the bypass passage, a cooler position for passing EGR gas through the EGR cooler, and a bypass position for passing EGR gas through the bypass passage. 3. The control device for an internal combustion engine according to claim 2, further comprising a valve body that is displaced between The internal combustion engine has a plurality of exhaust valves in at least one cylinder, and independent exhaust passages are formed from the cylinder head to the exhaust manifold for each of the exhaust valves.
An independent exhaust passage shutoff valve capable of shutting off the other independent exhaust passage in the vicinity of the downstream end of at least one of the plurality of independent exhaust passages of the same cylinder;
2. The control apparatus for an internal combustion engine according to claim 1, wherein the exhaust system volume reducing means reduces the exhaust system volume by closing the independent exhaust passage shut-off valve. An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
The provided with a valve overlap period during which an exhaust valve open period overlap and the intake valve open period of the internal combustion engine, to match the timing of the pulsation of the exhaust manifold pressure is a valley to the valve overlap period, the valve overlap and viable charging efficiency enhancement means charging efficiency enhancement control you lower than the exhaust manifold pressure intake manifold pressure in the period,
An EGR passage for recirculating exhaust gas of the internal combustion engine to an intake passage;
An EGR cooler for cooling EGR gas passing through the EGR passage;
A bypass passage for allowing EGR gas to flow downstream of the EGR passage without passing through the EGR cooler;
A valve body that is displaced into a blocking position for blocking the EGR passage upstream of the EGR cooler and the bypass passage, a cooler position for passing EGR gas through the EGR cooler, and a bypass position for passing EGR gas through the bypass passage. An EGR passage shut-off valve having
When the filling efficiency improvement control is executed and the engine load exceeds a predetermined high load judgment value, the valve body of the EGR passage shut-off valve is moved to the shut-off position, thereby the inside of the exhaust manifold and the exhaust manifold. An exhaust system volume reducing means for reducing an exhaust system volume which is a volume of a communicating space;
A control device for an internal combustion engine, comprising: The EGR cooler has a cooler inlet, a cooler outlet adjacent to the cooler inlet, and an EGR gas outflow direction is opposite to an EGR gas inflow direction to the cooler inlet;
The EGR passage shut-off valve is
An inlet through which EGR gas flows,
An outlet through which EGR gas flows out;
An upstream chamber communicating with both the inlet and the cooler inlet;
A downstream chamber communicating with both the outlet and the cooler outlet;
A bypass opening for communicating the upstream chamber and the downstream chamber;
Have
The valve body is configured by a swing valve that can swing around a rotating shaft located on the opposite side of the EGR cooler through the bypass opening,
The swing valve includes a blocking position for blocking the inlet, a cooler position for introducing the EGR gas in the upstream chamber into the cooler inlet by blocking the bypass opening, and the inlet from the inlet through the bypass opening. 6. The control device for an internal combustion engine according to claim 3 or 5, wherein the control device is displaceable to a bypass position allowing flow to the outlet.   The control apparatus for an internal combustion engine according to claim 3, 5 or 6, wherein the shut-off position is between the cooler position and the bypass position.   7. The control device for an internal combustion engine according to claim 3, wherein the shut-off position is outside the cooler position and the bypass position. An internal combustion engine having a plurality of exhaust valves in at least one cylinder, and an independent independent exhaust passage extending from the cylinder head to the exhaust manifold for each of the exhaust valves;
The provided with a valve overlap period during which an exhaust valve open period overlap and the intake valve open period of the internal combustion engine, to match the timing of the pulsation of the exhaust manifold pressure is a valley to the valve overlap period, the valve overlap and viable charging efficiency enhancement means charging efficiency enhancement control you lower than the exhaust manifold pressure intake manifold pressure in the period,
An independent exhaust passage shut-off valve capable of shutting off the other independent exhaust passage in the vicinity of the downstream end of at least one of the plurality of independent exhaust passages of the same cylinder;
When the charging efficiency improvement control is executed and the engine load exceeds a predetermined high load determination value, the volume of the space in the exhaust manifold and the space communicating therewith is closed by closing the independent exhaust passage shut-off valve An exhaust system volume reducing means for reducing the exhaust system volume;
A control device for an internal combustion engine, comprising: An EGR passage for recirculating exhaust gas of the internal combustion engine to the intake passage;
The control apparatus for an internal combustion engine according to claim 4 or 9, wherein an upstream end of the EGR passage is connected to the independent exhaust passage provided with the independent exhaust passage cutoff valve. An independent exhaust passage shut-off valve group of a first system including the independent exhaust passage shut-off valve;
A second independent exhaust passage including a second independent exhaust passage cutoff valve capable of shutting off other independent exhaust passages while leaving the independent exhaust passage in a cylinder having an independent exhaust passage to which the upstream end of the EGR passage is connected. A shutoff valve group;
When the engine representative temperature is lower than a predetermined cold determination temperature and / or when the engine load is light load smaller than a predetermined light load determination value, the exhaust system is closed by closing the independent exhaust passage shut-off valve group of the second system. An exhaust temperature reduction suppressing means for reducing the surface area;
The control apparatus for an internal combustion engine according to claim 10, further comprising: The independent exhaust passage cutoff valve of the cylinder having the independent exhaust passage to which the upstream end of the EGR passage is connected and the independent exhaust passage cutoff valve of other cylinders can be opened and closed independently.
A cylinder having an independent exhaust passage to which the upstream end of the EGR passage is connected when the engine representative temperature is lower than a predetermined cold determination temperature and / or when the engine load is lower than a predetermined light load determination value. 11. The control of an internal combustion engine according to claim 10, further comprising exhaust temperature lowering suppression means for reducing the surface area of the exhaust system by closing the independent exhaust passage cutoff valve of another cylinder while the independent exhaust passage cutoff valve is open. apparatus. An exhaust manifold for collecting exhaust gases of a plurality of cylinders of the internal combustion engine;
The provided with a valve overlap period during which an exhaust valve open period overlap and the intake valve open period of the internal combustion engine, to match the timing of the pulsation of the exhaust manifold pressure is a valley to the valve overlap period, the valve overlap and viable charging efficiency enhancement means charging efficiency enhancement control you lower than the exhaust manifold pressure intake manifold pressure in the period,
A valve body that is displaceable to a normal position and an exhaust system volume reduction position that reduces an exhaust system volume that is a volume of a space in the exhaust manifold and communicating with the exhaust manifold;
Valve body pressing means for pressing the valve body from the normal position to the exhaust system volume reduction position by the exhaust pressure of the internal combustion engine;
Biasing means for biasing the valve body in a direction to return the exhaust system volume reduction position to the normal position;
With
When entering the operating region where the charging efficiency improvement control is executed , the valve body is pressed by the exhaust pressure and moved from the normal position to the exhaust system volume reduction position, thereby reducing the exhaust system volume. A control device for an internal combustion engine. An EGR passage for recirculating exhaust gas of the internal combustion engine to the intake passage;
The control device for an internal combustion engine according to claim 13, wherein when the valve body moves to the exhaust system volume reduction position, the valve body blocks the EGR passage in the vicinity of an upstream end of the EGR passage.

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