JP2023059675A - Control device and control method for engine - Google Patents

Abstract

To take a prompt measure against deposit while reducing an effect on emission performance or fuel consumption performance.SOLUTION: When compression leakage that is a phenomenon of leakage of air from a combustion chamber through an intake port or an exhaust port is detected in a compression stroke, first control (S7) for operating a glow plug to heat the combustion chamber is executed. After the first control, when a fact that engine speed is a predetermined threshold value or lower is confirmed, second control accompanied by at least one of reduction of an opening of an EGR valve (S11) and increase in fuel injection amount from a fuel injection valve (S12) is executed.SELECTED DRAWING: Figure 5

Description

Applied for application of Article 30, Paragraph 2 of the Patent Act September 28, 2021 Started sales at dealers handling Mazda vehicles in Europe

The present invention relates to technology for controlling an engine having intake and exhaust valves.

Deposits may adhere (bite) between the intake valve and the valve seat or between the exhaust valve and the valve seat. Deposit build-up results in compression leaks, where compressed air leaks from the combustion chamber through the intake or exhaust ports. Compression leaks cause poor ignition where the air-fuel mixture in the combustion chamber does not burn properly (or misfires).

As an engine in which countermeasures against deposit adhesion are taken, the one disclosed in Patent Document 1 below is known. In the engine of Patent Document 1, it is determined whether or not deposits are present during deceleration fuel cut, and if deposits are determined, control such as increasing the opening of the intake shutter valve is executed. Increasing the opening of the intake shutter valve has the effect of increasing the pressure in the combustion chamber, increasing the possibility of crushing (removing) the deposits.

Japanese Patent No. 6531780

As described above, in Patent Document 1, deposit adhesion determination and countermeasure control are performed only during deceleration fuel cut. In other words, during combustion operation of the engine, that is, during operation accompanied by combustion of air-fuel mixture in the combustion chamber, even if deposits adhere, no particular countermeasures are taken. For this reason, there is concern that countermeasures against deposits will be delayed. In other words, even if deposits adhere during combustion operation of the engine, countermeasures are not taken until the operation mode shifts to deceleration fuel cut, so there is a possibility that compression leakage and ignition failure due to deposits will continue for a while. There is In particular, if deposits accumulate when the engine is in an idle state or a low-speed state close to it, the engine may stall (engine stall) due to compression leakage and poor ignition when the engine's rotational inertia is low. have a nature.

Therefore, it is proposed to take some measures against deposits even during combustion operation of the engine. However, depending on the content of the countermeasures, the emission performance or fuel consumption performance of the engine may be affected, so it is desirable to take appropriate countermeasures in consideration of these influences.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an engine control apparatus capable of quickly taking countermeasures against deposits while reducing the influence on emission performance or fuel efficiency. and

In order to solve the above-described problems, an engine control device according to one aspect of the present invention includes a combustion chamber, an intake passage connected to the combustion chamber via an intake port, and the combustion chamber via an exhaust port. A device for controlling an engine comprising an exhaust passage connected to a chamber, an intake valve and an exhaust valve for opening and closing the intake port and the exhaust port, and an EGR passage connecting the intake passage and the exhaust passage. a fuel injection valve that injects fuel into the combustion chamber; a glow plug that heats the combustion chamber; an EGR valve that is openable and closable in the EGR passage; A rotation detection unit that detects the number of revolutions, a compression leakage detection unit that detects compression leakage, which is a phenomenon in which air leaks from the combustion chamber through the intake port or the exhaust port during a compression stroke, the fuel injection valve, and the glow. a plug and a controller for controlling the EGR valve, wherein the controller operates the glow plug to heat the combustion chamber when the compression leak detection unit detects compression leak; After the first control, when it is confirmed that the engine speed detected by the rotation detection unit is equal to or less than a predetermined threshold value, the opening degree of the EGR valve is reduced and the fuel injection is performed. A second control is executed that accompanies at least one of increasing the amount of fuel injected from the valve.

The detection of compression leakage means that there is a high possibility that deposits are attached to the valve seat portion of the intake valve or the exhaust valve. In the present invention, in such a case, the glow plug is activated first, so that the activated glow plug can quickly heat the combustion chamber and improve the ignitability of the air-fuel mixture. As a result, it is possible to suppress the ignition failure of the air-fuel mixture caused by deposit adhesion (compression leakage), and reduce the possibility of the engine stalling (engine stall) triggered by the ignition failure.

However, depending on the degree of compression leakage, there is a possibility that the ignition failure cannot be avoided even if the glow plug is operated. In particular, if such a situation occurs in a situation in which the engine speed is relatively low (in other words, a situation in which rotational inertia is low), the possibility of engine stalling increases. In contrast, in the present invention, when the engine speed after the glow plug is activated is equal to or less than a predetermined threshold value, the control for reducing the opening of the EGR valve or the control for increasing the fuel injection amount is executed. It is possible to suppress the occurrence of engine stall due to such circumstances. That is, when the degree of opening of the EGR valve is reduced, the proportion of EGR gas, which is an inert gas, decreases in the combustion chamber, resulting in improved ignitability of the air-fuel mixture. Moreover, even when the fuel injection amount is increased, the ignitability of the air-fuel mixture is also improved. As a result, it is possible to reduce the possibility of poor ignition occurring in a situation where the engine speed is low, and to effectively suppress the occurrence of an engine stall.

Moreover, in the present invention, the above-described control for changing the opening degree of the EGR valve or the fuel injection amount is not executed unless the engine speed is equal to or lower than the threshold value, so the possibility that the emission performance or the fuel efficiency performance is affected is reduced. can do. That is, a reduction in the degree of opening of the EGR valve raises the combustion temperature in the combustion chamber and has the effect of increasing the amount of NOx produced. Also, an increase in the fuel injection amount has the effect of deteriorating fuel efficiency. In contrast, in the present invention, even if compression leakage is confirmed, these measures are not taken until the engine speed falls below the threshold value, so there is a possibility that the amount of NOx generated will increase or the fuel efficiency performance will decrease. can be reduced. In particular, if a compression leak is confirmed in a situation where the engine speed exceeds the threshold and the glow plug is activated in response to this, the deposits are removed by combustion pressure etc. before the engine speed falls below the threshold. There is a possibility that In such a case, it is not necessary to change the opening of the EGR valve or the amount of fuel injection to deal with deposits, so the impact on emission performance or fuel efficiency can be minimized. Thus, in the present invention, it is possible to suppress the occurrence of engine stall due to deposit adhesion while reducing the influence on the emission performance or fuel efficiency of the engine.

Preferably, the compression leak detection unit is included in a compression stroke or included in a first time required for passage of a first crank angle range straddling compression top dead center, and in an expansion stroke immediately after the compression stroke. Compression leakage is detected based on a second time required for passing through a second crank angle range on the retard side of the first crank angle range.

According to this configuration, it is possible to accurately detect compression leakage by utilizing the fact that the relationship between the first time and the second time changes depending on the presence or absence of compression leakage. That is, when compression leakage occurs, the compression reaction force acting on the piston during the compression stroke becomes smaller, so the amount of change in the moving speed of the piston before and after passing the compression top dead center becomes smaller. A change occurs in the relationship with the second time. According to the above configuration, it is possible to accurately detect compression leakage by utilizing this fact.

The engine may be an in-vehicle engine connected to wheels via an automatic transmission capable of automatically changing the reduction ratio. In this case, after the first control, the controller maintains the engine speed high when it is confirmed that the compression leak has occurred while the engine speed is greater than the threshold value. It is preferable to execute a third control for controlling the automatic transmission as described above.

According to this configuration, it is possible to maintain a high engine speed while the vehicle is running by controlling the automatic transmission, thereby reducing the possibility of the engine stalling.

The automatic transmission may include a lockup clutch that directly connects an output shaft of the engine and the wheels. In this case, the third control includes control for expanding the lockup region, which is the range of the engine speed in which the lockup clutch is engaged, to the low speed side, and downshifting for increasing the speed reduction ratio. It is preferable to include at least one of control for changing the shift pattern so as to increase the engine speed (shift-down speed).

When the shift pattern is changed to increase the downshift rotation speed, for example, when the vehicle is decelerating, the downshift is performed earlier than usual. As a result, the speed reduction ratio can be increased before the engine speed is sufficiently decreased, and the engine speed can be increased by the speed reduction ratio after the increase. In addition, when the lockup region is expanded to the low rotation side, for example, when the vehicle decelerates, the lockup state (the state in which the engine output shaft and the wheels are directly connected) is maintained until the engine speed is lower than normal. . As a result, the output shaft of the engine can be kept rotating in synchronism with the wheels, and the rotational energy of the wheels can be used to suppress a decrease in the engine speed. In either case, the engine speed is maintained relatively high, so the possibility of engine stall can be reduced.

An engine control method according to another aspect of the present invention includes a combustion chamber, an intake passage connected to the combustion chamber via an intake port, an exhaust passage connected to the combustion chamber via an exhaust port, an intake valve and an exhaust valve that open and close the intake port and the exhaust port; an EGR passage that connects the intake passage and the exhaust passage; a fuel injection valve that injects fuel into the combustion chamber; and an EGR valve provided in the EGR passage so as to be openable and closable, wherein air leaks from the combustion chamber through the intake port or the exhaust port during a compression stroke. a first step of detecting a compression leak, a second step of operating the glow plug to heat the combustion chamber when the compression leak is detected in the first step, and the second step of a third step of detecting an engine speed, which is the speed of the output shaft of the engine; and a fourth step of at least one of reducing the degree of opening of the EGR valve and increasing the amount of fuel injected from the fuel injection valve.

This invention of the control method can also provide the same effects as the invention of the control device described above.

As described above, according to the engine control device and control method of the present invention, it is possible to quickly take countermeasures against deposits while reducing the influence on emission performance or fuel efficiency performance.

1 is a system diagram showing the overall configuration of an engine to which a control device according to an embodiment of the invention is applied; FIG. It is a cross-sectional view showing the details of the intake and exhaust valves and their valve mechanism. FIG. 2 is a plan view schematically showing the structure of a power transmission system between an engine and wheels; FIG. 2 is a functional block diagram showing control systems for an engine and an automatic transmission; 4 is a flow chart showing an example of countermeasure control against deposits adhering to a valve seat portion; FIG. 4 is a diagram for explaining a method of calculating a compression state index value; FIG.

[Overall structure of the engine]
FIG. 1 is a system diagram showing the overall configuration of an engine to which a control device according to one embodiment of the invention is applied. An engine 1 shown in this figure is a four-cycle diesel engine mounted on a vehicle as a power source for running. The engine 1 includes an engine body 2, an intake passage 30 through which intake air introduced into the engine body 2 flows, an exhaust passage 40 through which exhaust gas discharged from the engine body 2 flows, and an exhaust gas flowing through the exhaust passage 40. and a supercharger 60 for supercharging the intake air flowing through the intake passage 30 .

The engine body 2 is, for example, of a multi-cylinder type having a plurality of cylinders 2a arranged in a direction orthogonal to the plane of FIG. 1 (see also FIG. 3 described later). The engine body 2 includes a cylinder block 3 , a cylinder head 4 and a plurality of pistons 5 . A cylinder 2 a is formed by a cylinder block 3 and a cylinder head 4 . That is, a plurality of cylindrical spaces corresponding to the plurality of cylinders 2a are formed inside the cylinder block 3, and the cylinder head 4 is attached to the upper surface of the cylinder block 3 so as to block the cylindrical spaces from above. The piston 5 is accommodated in each cylinder 2a so as to be reciprocally slidable. In the present embodiment, the side facing the cylinder head 4 from the cylinder block 3 is treated as the top, and the reverse is treated as the bottom. do not have.

A combustion chamber C is formed above the piston 5 of each cylinder 2a. Each combustion chamber C is a space defined by the lower surface of the cylinder head 4 , the side peripheral surface (cylinder liner) of the cylinder 2 a, and the upper surface (crown surface) of the piston 5 . The combustion chamber C is supplied with fuel injected from a fuel injection valve 9, which will be described later. The piston 5 receives the combustion energy of the fuel supplied to the combustion chamber C and reciprocates vertically. Since the engine 1 of this embodiment is a diesel engine, fuel containing light oil is used as the fuel supplied to the combustion chamber C. As shown in FIG.

A crankshaft 7 that is an output shaft of the engine body 2 is provided in a lower portion of the cylinder block 3 (below the piston 5). The crankshaft 7 is connected to the piston 5 of each cylinder 2a via a connecting rod 8, and rotates around the central axis according to the reciprocating motion (vertical motion) of the piston 5. As shown in FIG.

A crank angle sensor SN1 and a water temperature sensor SN2 are attached to the cylinder block 3 . The crank angle sensor SN1 is a sensor that detects the crank angle, which is the rotation angle of the crankshaft 7, and the engine speed, which is the rotation speed of the crankshaft 7. FIG. The water temperature sensor SN2 is a sensor that detects the temperature of cooling water flowing through the inside of the cylinder block 3 and the cylinder head 4, that is, the engine water temperature. Incidentally, the crank angle sensor SN1 corresponds to the "rotation detector" in the present invention.

A fuel injection valve 9 and a glow plug 10 are attached to the cylinder head 4 . The fuel injection valve 9 is an injection valve that injects fuel into the combustion chamber C of each cylinder 2a. The glow plug 10 is a plug that heats the combustion chamber C of each cylinder 2a. One fuel injection valve 9 and one glow plug 10 are provided for each cylinder 2a.

The fuel injection valve 9 is attached to the cylinder head 4 so that its tip portion is exposed to the combustion chamber C. As shown in FIG. A plurality of injection holes (not shown) serving as fuel outlets are formed at the tip of the fuel injection valve 9 . The fuel injected from each injection hole burns by self-ignition in the combustion chamber C, which is heated to a high temperature and a high pressure due to the compression action of the piston 5 .

The glow plug 10 is attached to the cylinder head 4 so that its tip is exposed to the combustion chamber C. As shown in FIG. A tip portion of the glow plug 10 is provided with a heating element (not shown) that generates heat when energized. When energized, the heating element heats up in a short period of time and heats the combustion chamber C. As shown in FIG.

The glow plug 10 operates to heat the combustion chamber C when the engine 1 is cold. Specifically, the glow plug 10 operates when the engine water temperature at start-up, that is, the temperature detected by the water temperature sensor SN2 at start-up of the engine 1, is equal to or lower than a predetermined first temperature. Further, after the completion of starting the engine 1, the operation of the glow plug 10 (heating of the combustion chamber C) is continued until the engine water temperature reaches a second temperature higher than the first temperature.

An intake port 11 and an exhaust port 12 are formed in the cylinder head 4 . The intake port 11 is a port that communicates the combustion chamber C of each cylinder 2 a with the intake passage 30 . The exhaust port 12 is a port that communicates the combustion chamber C of each cylinder 2 a and the exhaust passage 40 . An intake valve 13 is provided in the intake port 11 of each cylinder 2a, and an exhaust valve 14 is provided in the exhaust port 12 of each cylinder 2a.

The cylinder head 4 is equipped with an intake valve mechanism 15 and an exhaust valve mechanism 16 . The intake valve mechanism 15 is a mechanism that opens and closes the intake valve 13 of each cylinder 2 a in conjunction with the rotation of the crankshaft 7 . The exhaust valve mechanism 16 is a mechanism that opens and closes the exhaust valve 14 of each cylinder 2a in conjunction with the rotation of the crankshaft 7. As shown in FIG. The intake valve 13 periodically opens and closes the opening of the intake port 11 on the side of the combustion chamber C according to the driving of the intake valve mechanism 15 . The exhaust valve 13 periodically opens and closes the opening of the exhaust port 12 on the side of the combustion chamber C in accordance with the driving of the exhaust valve mechanism 16 .

The intake passage 30 is a tubular member for introducing intake air into the combustion chamber C of each cylinder 2a. The intake passage 30 has an intake manifold 30a and a surge tank 30b at a downstream portion near the engine body 2 . The surge tank 30b is a tank that provides an enlarged space for equalizing the amount of intake air introduced into each cylinder 2a. The intake manifold 30a includes a plurality of branch pipes connecting the surge tank 30b and the intake port 11 of each cylinder 2a. A portion of the intake passage 30 on the upstream side of the surge tank 30b is formed in a single tubular shape.

An air cleaner 31, an intercooler 32, and an intake shutter valve 33 are provided in a portion of the intake passage 30 upstream of the surge tank 30b. The air cleaner 31 is a filter that removes foreign matter from intake air. The intercooler 32 is a heat exchanger that cools intake air compressed by the supercharger 60 . The intake shutter valve 33 is an electric butterfly valve provided in the intake passage 30 so as to be able to open and close in order to throttle the flow rate of intake air. The air cleaner 31 , intercooler 32 , and intake shutter valve 33 are arranged in this order from the upstream side farther from the engine body 2 .

An airflow sensor SN3 and an intake pressure sensor SN4 are attached to the intake passage 30 . The airflow sensor SN3 is a sensor that detects the flow rate of intake air introduced into the engine body 2, and is arranged in a portion of the intake passage 30 downstream of the air cleaner 31. As shown in FIG. The intake pressure sensor SN4 is a sensor that detects the pressure of intake air introduced into the engine body 2, and is arranged in the surge tank 30b.

The exhaust passage 40 is a tubular member for discharging the exhaust gas discharged from the combustion chamber C of each cylinder 2a to the outside. The exhaust passage 40 has an exhaust manifold 40a in an upstream portion close to the engine body 2 . Although not shown in detail, the exhaust manifold 40a includes a plurality of branch pipes communicating with the exhaust ports 12 of the cylinders 2a, and an exhaust collecting portion where the branch pipes gather. A portion of the exhaust passage 40 downstream of the exhaust manifold 40a (exhaust collecting portion) is formed in a single pipe shape.

A catalyst device 41 is provided in a portion of the exhaust passage 40 downstream of the exhaust manifold 40a. The catalyst device 41 incorporates an oxidation catalyst 41a that oxidizes CO and HC in the exhaust gas to render them harmless, and a DPF (diesel particulate filter) 41b that collects particulate matter contained in the exhaust gas. are doing.

The supercharger 60 is a so-called two-stage supercharger, and includes a first supercharger 61 and a second supercharger 62 arranged in series.

The first supercharger 61 is a turbocharger including a first compressor 61a arranged in the intake passage 30 and a first turbine 61b coaxially connected to the first compressor 61a and arranged in the exhaust passage 40. be. The first compressor 61 a is arranged in the intake passage 30 between the air cleaner 31 and the intercooler 32 . The first turbine 61b is arranged upstream of the catalyst device 41 in the exhaust passage 40 .

Similarly, the second supercharger 62 is a turbocharger including a second compressor 62a arranged in the intake passage 30 and a second turbine 62b coaxially connected to the second compressor 62a and arranged in the exhaust passage 40. It is a feeder. The second compressor 62 a is arranged in a portion downstream of the first compressor 61 a in the intake passage 30 , that is, in a portion between the first compressor 61 a and the intercooler 32 . The second turbine 62b is arranged upstream of the first turbine 61b in the exhaust passage 40 .

The first supercharger 61 is a turbocharger larger than the second supercharger 62 . That is, the first compressor 61a and the first turbine 61b are formed to be larger in size than the second compressor 62a and the second turbine 62b.

An intake bypass passage 63 is connected to the intake passage 30 . The intake bypass passage 63 is a passage for bypassing the second compressor 62a. An electric bypass valve 63a is provided in the intake bypass passage 63 so as to be able to be opened and closed.

A first exhaust bypass passage 64 and a second exhaust bypass passage 65 are connected to the exhaust passage 40 . The first exhaust bypass passage 64 is a passage for bypassing the first turbine 61b, and the second exhaust bypass passage 65 is a passage for bypassing the second turbine 62b. An electric waste gate valve 64a is provided in the first exhaust bypass passage 64 so as to be able to be opened and closed. An electric regulation valve 65a is provided in the second exhaust bypass passage 65 so as to be able to open and close.

When supercharging by the first supercharger 61 is performed, the wastegate valve 64a is closed. As a result, the exhaust gas discharged from the engine body 2 is introduced into the first turbine 61b, and the first turbine 61b is rotationally driven by the exhaust gas. The first compressor 61a rotates in conjunction with the first turbine 61b to force-feed the intake air downstream. That is, the first supercharger 61 achieves supercharging of the intake air in the intake passage 30 while compressing it and sending it to the engine body 2 .

When supercharging by the second supercharger 62 is performed, the regulation valve 65a and the bypass valve 63a are closed. As a result, the exhaust gas discharged from the engine body 2 is introduced into the second turbine 62b, and the second turbine 62b is rotationally driven by the exhaust gas. The second compressor 62a rotates in conjunction with the second turbine 62b to force-feed the intake air downstream. In other words, the second supercharger 62 achieves supercharging of the intake air in the intake passage 30 while compressing it and sending it out to the engine body 2 .

The EGR device 50 includes an EGR passage 51 , an EGR cooler 52 and an EGR valve 53 . The EGR passage 51 is a passage for recirculating exhaust gas from the exhaust passage 40 to the intake passage 30, and connects the exhaust passage 40 and the intake passage 30 to each other. Specifically, the EGR passage 51 connects a portion of the exhaust passage 40 upstream of the second turbine 62b and a portion of the intake passage 30 between the intake shutter valve 33 and the surge tank 30b. The EGR cooler 52 is a heat exchanger that cools the exhaust gas recirculated to the intake passage 30 through the EGR passage 51, that is, the EGR gas. The EGR valve 53 is an electrically operated valve provided in the EGR passage 51 for adjusting the recirculated amount of exhaust gas, that is, the EGR amount. The EGR valve 53 is arranged downstream (closer to the intake passage 30 ) than the EGR cooler 52 in the EGR passage 51 .

[Details of intake and exhaust valves]
FIG. 2 is a sectional view showing the details of the intake and exhaust valves 13, 14 of the engine body 2 and the valve trains 15, 16 thereof. As shown in this figure, the intake valve 13 has a stem portion 13a and a head portion 13b. The stem portion 13a is a columnar member elongated in the vertical direction, and is supported by the cylinder head 4 so as to be slidable in the axial direction (vertical direction). The head portion 13b is a disc-shaped member capable of closing the opening of the intake port 11 on the side of the combustion chamber C, and is formed so as to increase in diameter from the lower end of the stem portion 13a.

Similarly, the exhaust valve 14 has a stem portion 14a and an umbrella portion 14b. The stem portion 14a is a columnar member elongated in the vertical direction, and is supported by the cylinder head 4 so as to be slidable in the axial direction (vertical direction). The umbrella portion 14b is a disk-shaped member capable of closing the opening of the exhaust port 12 on the side of the combustion chamber C, and is formed so as to increase in diameter from the lower end of the stem portion 14a.

Valve seats 11 a and 12 a are attached to the cylinder head 4 . The valve seat 11a is a ring-shaped member attached to the opening of the intake port 11 on the side of the combustion chamber C, and when the intake valve 13 is closed, the valve seat 11a is in close contact with the peripheral edge of the head portion 13b. The valve seat 12a is a ring-shaped member attached to the opening of the exhaust port 12 on the side of the combustion chamber C, and is brought into close contact with the peripheral edge of the head portion 14b when the exhaust valve 14 is closed.

The intake valve mechanism 15 includes a camshaft 21 , a swing arm 23 and a valve spring 25 . The camshaft 21 is a rotatable shaft linked to the crankshaft 7 via a transmission member such as a timing chain. Specifically, the camshaft 21 is provided with a shaft portion 21a extending in the direction in which the cylinders 2a are arranged (a direction perpendicular to the paper surface of FIG. 2), and at a position corresponding to the intake valve 13 of each cylinder 2a on the shaft portion 21a. and a plurality of cam portions 21b. The swing arm 23 is swingably supported below the cam portion 21b of each cylinder 2a. The valve spring 25 is attached to the cylinder head 4 so as to bias the intake valve 13 in the closing direction (upward). The intake valve 13 periodically opens by receiving a downward pressing force transmitted from the cam portion 21b through the swing arm 23 as the camshaft 21 rotates. On the other hand, when the pressing force is not applied, the intake valve 13 is maintained in the closed state in which the head portion 13b is in close contact with the valve seat 11a due to the upward biasing force of the valve spring 25 .

Similarly, the exhaust valve train 16 includes a camshaft 22 , a swing arm 24 and a valve spring 26 . The camshaft 22 is a rotatable shaft linked with the crankshaft 7 via the transmission member. Specifically, the camshaft 22 is provided with a shaft portion 22a extending in the direction in which the cylinders 2a are arranged (a direction perpendicular to the paper surface of FIG. 2), and at a position corresponding to the exhaust valve 14 of each cylinder 2a on the shaft portion 22a. and a plurality of cam portions 22b. The swing arm 24 is swingably supported below the cam portion 22b of each cylinder 2a. The valve spring 26 is attached to the cylinder head 4 so as to bias the exhaust valve 14 in the closing direction (upward). As the camshaft 22 rotates, the exhaust valve 14 receives a downward pressing force transmitted from the cam portion 22b through the swing arm 24 and periodically opens. On the other hand, when the pressing force is not applied, the exhaust valve 14 is maintained in the closed state in which the head portion 14b is in close contact with the valve seat 12a due to the upward urging force of the valve spring 26 .

[Power system]
FIG. 3 is a plan view schematically showing the structure of a power transmission system for transmitting the output of the engine 1 to the wheels W1 of the vehicle. The vehicle here is a front-engine, rear-drive (FR) vehicle. Therefore, in FIG. 3, the wheels W1 are the rear wheels, and the engine body 2 is arranged in the engine room in the front part of the vehicle. Although FIG. 3 illustrates an in-line four-cylinder engine body 2 having four cylinders 2a arranged in a row, the number and arrangement of the cylinders 2a can be changed as appropriate.

As shown in FIG. 3, the power transmission system of the vehicle in this embodiment includes an automatic transmission 101 connected to the engine body 2, a propeller shaft 102 extending rearward from the automatic transmission 101, and a rear end of the propeller shaft 102. and a pair of drive shafts 104 extending left and right from the differential 103 . Wheels W1 are attached to the ends of the drive shafts 104 in the vehicle width direction. The output rotation of the engine body 2 is input to the differential gear 103 via the propeller shaft 102 after being shifted by the automatic transmission 101 . The rotation input to the differential gear 103 is transmitted to each wheel W1 via the left and right drive shafts 104 .

Automatic transmission 101 includes torque converter 110 and transmission body 120 . Torque converter 110 is a fluid clutch that transmits output rotation of engine body 2, that is, rotation of crankshaft 7, to transmission body 120 via a working fluid (ATF). The transmission body 120 is a device that transmits the rotation input from the torque converter 110 to the wheels W1 while changing the speed.

The torque converter 110 includes a pump impeller 111 that rotates integrally with the crankshaft 7 of the engine body 2 , a turbine runner 112 that faces the pump impeller 111 , and a stator 113 that is arranged between the pump impeller 111 and the turbine runner 112 . and built-in. Rotation of pump impeller 111 is transmitted to turbine runner 112 via working fluid in torque converter 110 . The rotation of turbine runner 112 is input to transmission body 120 via turbine shaft 114 .

A lockup clutch 115 is provided inside the torque converter 110 . The lockup clutch 115 is a clutch that connects and disconnects the crankshaft 7 of the engine body 2 and the turbine runner 112 . When the crankshaft 7 and the turbine runner 112 are connected by engagement of the lockup clutch 115, the crankshaft 7 and the turbine shaft 114 (the input shaft of the transmission main body 120) are mechanically connected without fluid. A condition is obtained in which the rotation of the crankshaft 7 is directly transmitted to the wheels W1. In other words, the lockup clutch 115 is a clutch that directly connects the output shaft (crankshaft 7) of the engine 1 and the wheels W1.

Engagement of the lockup clutch 115 leads to improvement in power transmission efficiency. However, if the lockup clutch 115 is engaged when the engine speed or vehicle speed is low, vibrations of the engine 1 are likely to be transmitted to the vehicle. Therefore, the lockup clutch 115 is engaged under predetermined conditions except when the engine speed or vehicle speed is low, and is disengaged (disengaged) when the engine speed or vehicle speed is low.

The transmission main body 120 incorporates a multistage transmission mechanism 121 capable of achieving a plurality of gear stages with different reduction ratios. The transmission mechanism 121 includes a gear mechanism 122 in which a plurality of planetary gear sets are combined, and a plurality of frictional engagement elements (not shown) including clutches and brakes that are engaged or disengaged in order to switch the power transmission path of the gear mechanism 122. , and a hydraulic control valve 123 (FIG. 4) consisting of a solenoid valve or the like for controlling the hydraulic pressure supplied to each friction engagement element and switching engagement/release. Hydraulic control valve 123 engages/disengages appropriate frictional engagement elements to achieve a desired gear stage in transmission mechanism 121 according to the speed of the vehicle and the like. The output rotation of the torque converter 110, that is, the rotation of the turbine shaft 114, is transmitted to the propeller shaft 102 (and thus the wheels W1) after being shifted at a speed reduction ratio corresponding to the gear stage of the transmission mechanism 121.

[Control system]
FIG. 4 is a functional block diagram showing a control system for the engine 1 and the automatic transmission 101 described above. The PCM 70 shown in this figure is a microprocessor for centrally controlling the engine 1 and the automatic transmission 101, and is composed of a well-known CPU, ROM, RAM and the like. The PCM 70 corresponds to the "controller" in the present invention.

Information detected by various sensors is input to the PCM 70 . For example, the PCM 70 is electrically connected to the above-described crank angle sensor SN1, water temperature sensor SN2, airflow sensor SN3, and intake pressure sensor SN4. The PCM 70 is sequentially input with information detected by the respective sensors (that is, information such as crank angle, engine speed, engine water temperature, intake flow rate, intake pressure, etc.).

The vehicle is also provided with an accelerator sensor SN5 and a vehicle speed sensor SN6. The accelerator sensor SN5 is a sensor that detects the opening of an accelerator pedal operated by the driver of the vehicle, that is, the accelerator opening. The vehicle speed sensor SN6 is a sensor that detects the traveling speed of the vehicle, that is, the vehicle speed. Information detected by these accelerator sensor SN5 and vehicle speed sensor SN6 is also input to the PCM 70 in sequence.

The PCM 70 controls each part of the engine 1 and the automatic transmission 101 based on input information from the sensors SN1 to SN6. That is, the PCM 70 is electrically connected to the fuel injection valve 9, the glow plug 10, the intake shutter valve 33, the EGR valve 53, the bypass valve 63a, the wastegate valve 64a, and the regulating valve 65a, and is also connected to the automatic transmission. It is electrically connected to the lockup clutch 115 of the machine 101 and the hydraulic control valve 123 . The PCM 70 outputs control signals generated based on input information from the sensors SN1 to SN6 to these devices.

[Measures against sticking of deposits]
Here, deposits (foreign matter) may adhere to the valve seat portion of the intake valve 13 or the exhaust valve 14 . For example, deposits adhering to the inner wall of the intake passage 30 may come off for some reason, flow downstream, and become caught between the head portion 13b of the intake valve 13 and the valve seat 11a. Alternatively, deposits that have flowed into the combustion chamber C may get caught between the umbrella portion 14b of the exhaust valve 14 and the valve seat 12a. Such deposition (biting) of deposits on the valve seat portion leads to compression leakage, which is a phenomenon in which compressed air leaks from the combustion chamber C through the intake port 11 or the exhaust port 12 during the compression stroke. When compression leakage occurs, ignition failure, in which the mixture of fuel and air injected into the combustion chamber C is not properly combusted (or misfires), is likely to occur. Therefore, in the present embodiment, the PCM 70 executes control as shown in FIG. 5 as a countermeasure against deposits adhering to the valve seat. The details of this control will be described below.

FIG. 5 is a flow chart showing the details of control executed by the PCM 70 during operation of the engine 1 with the crankshaft 7 rotating. When the control starts, the PCM 70 reads information output from the sensors SN1 to SN6 (step S1).

Next, the PCM 70 calculates a compression state index value V, which is an index value representing the compression state of the cylinder 2a (step S2). Specifically, the PCM 70 calculates the ratio (T1/T2) between the first time T1 and the second time T2 shown in FIG. The first time T1 is the time required to pass through the first crank angle range ΔC1 spanning from the compression stroke to the expansion stroke, and the second time T2 is the second crank angle range ΔC2 included in the expansion stroke immediately after the compression stroke. is the time required to pass through The PCM 70 calculates a compression state index value V (=T1/T2), which is a value obtained by dividing the former by the latter, for each combustion cycle of each cylinder 2a. The compression state index value V can be calculated based on input information from the crank angle sensor SN1.

More specifically, the first crank angle range ΔC1 is set to a predetermined angle range sandwiching the compression top dead center (TDC), which is the boundary between the compression stroke and the expansion stroke, and the second crank angle range ΔC2 is set to the second crank angle range. It is set to a predetermined angle range which is away from the one crank angle range ΔC1 to the retard side and which is included in the expansion stroke. Also, the first crank angle range ΔC1 and the second crank angle range ΔC2 are set to have the same width (for example, a width of 30° CA) in FIG. Here, the moving speed of the piston 5 passing through the second crank angle range ΔC2 is faster than the moving speed of the piston 5 passing through the first crank angle range ΔC1. This is because the compression reaction force acting on the piston 5 is maximized at the compression top dead center, and the expansion force acts to accelerate the piston 5 during the expansion stroke. As described above, the passing speed of the second crank angle range ΔC2 is faster than the passing speed of the first crank angle range ΔC1 because the second time T2, which is the passing time of the second crank angle range ΔC2, is faster than the first crank angle range ΔC1. This means that it is shorter than the first time T1, which is the time through which the crank angle range ΔC1 passes. Therefore, the compressed state index value V calculated as T1/T2 as described above is normally calculated as a value significantly larger than one.

However, if compressed air is leaking from the combustion chamber C through the intake port 11 or the exhaust port 12 during the compression stroke, that is, if compression leakage occurs, the compression reaction force acting on the piston 5 during the compression stroke will increase. Since it becomes smaller, the difference between the first time T1 and the second time T2 is reduced. This means that the compression state index value V (=T1/T2), which is the ratio of the two, approaches one. In other words, the compression state index value V is a parameter that varies depending on the presence or absence of compression leakage. The PCM 70 estimates the compression state (presence or absence of compression leakage) of each cylinder 2a by calculating the compression state index value V having such properties for each combustion cycle of each cylinder 2a.

Thus, in this embodiment, the compression state index value V, which is a parameter for detecting compression leakage, is calculated by the PCM 70 based on the input information from the crank angle sensor SN1. Therefore, the combination of the crank angle sensor SN1 and the PCM 70 corresponds to the "compression leak detector" in the present invention.

After calculating the compression state index value V in step S2, the PCM 70 determines whether deposits are attached to the valve seat portion based on the calculated compression state index value V (step S3). Specifically, the PCM 70 compares the compression state index value V with a predetermined threshold value Vx for each combustion cycle of each cylinder 2a to determine whether the former is lower than the latter, that is, whether V<Vx is established. judge. Then, when a state in which V<Vx is established, that is, a state in which the compression state index value V is less than the threshold value Vx occurs continuously for a predetermined number of cycles n1 for the same cylinder 2a, the valve seat portion ( Deposits are determined to be attached between the intake valve 13 and the valve seat 11a or between the exhaust valve 14 and the valve seat 12a. Note that the number of consecutive cycles n1 here can be set to, for example, "2".

The threshold value Vx used in the determination in step S3 is determined from the average value of the compression state index values V of all the cylinders 2a calculated one cycle before. When the compression state index value V of the specific cylinder 2a is smaller than the threshold value Vx, there is a high possibility that compression leakage has occurred in the specific cylinder 2a, that is, the valve seat of the specific cylinder 2a This means that there is a high possibility that compressed air is leaking from the combustion chamber C due to deposits adhering to the parts. Therefore, the PCM 70 determines that deposits are attached to the cylinder 2a when the above-described state of V<Vx occurs consecutively for n1 cycles in the same cylinder 2a.

When it is determined as NO in step S3, that is, when it is confirmed that no deposit is attached to the valve seat portion of any cylinder 2a, the PCM 70 executes normal engine control (step S13). It should be noted that since measures against deposits are unnecessary here, control corresponding to steps S8, S9, S11, and S12, which will be described later, is not executed.

On the other hand, when it is determined as YES in the step S3 and it is confirmed that the deposit adheres to the valve seat portion of one of the cylinders 2a, that is, when the intake valve 13 (or the exhaust valve 14) of the cylinder 2a and the valve When it is confirmed that the deposit is caught between the seat 11a (or 12a), the PCM 70 determines whether or not the engine 1 is in the deceleration fuel cut (step S4). The deceleration fuel cut is an operation mode in which fuel injection from the fuel injection valve 9 is stopped during deceleration of the vehicle, in other words, an operation mode in which rotation of the crankshaft 7 is maintained using rotation of the wheels W1. Such a deceleration fuel cut is performed, for example, under the condition that the accelerator opening is zero (the accelerator pedal is not depressed), the vehicle speed is higher than a predetermined reference speed, and the engine speed is a predetermined reference speed. It is permitted when both the condition that it is higher than the number of revolutions and the condition are satisfied. The PCM 70 determines whether or not such conditions for permitting deceleration fuel cut are satisfied based on input information from the crank angle sensor SN1, the accelerator sensor SN5, and the vehicle speed sensor SN6. perform a cut.

If the determination in step S4 is YES and it is confirmed that the deceleration fuel cut is being executed, the PCM 70 changes the opening of the intake shutter valve 33 to a value larger than normal (step S5). That is, during the deceleration fuel cut, the opening of the intake shutter valve 33 is normally set to a relatively small value for the purpose of applying engine braking. On the other hand, in step S5, the intake shutter valve 33 is controlled so that the opening of the intake shutter valve 33 increases to a value larger than the normal opening during the deceleration fuel cut. This is to increase the in-cylinder pressure, which is the internal pressure of the cylinder 2a (combustion chamber C), to increase the possibility of crushing deposits adhering to the valve seat portion.

On the other hand, if it is determined NO in step S4 that the deceleration fuel cut is not being executed, that is, if it is confirmed that the operation accompanied by the combustion of the air-fuel mixture (combustion operation) is being performed, The PCM 70 determines whether or not the glow plug 10 is inactive (step S6). That is, the PCM 70 confirms the state of energization of the heat generating element of the glow plug 10, and determines that the glow plug 10 is inoperative when energization is not performed.

If the determination in step S6 is YES and it is confirmed that the glow plug 10 is inactive, the PCM 70 activates the glow plug 10 (step S7). That is, the PCM 70 energizes the heating element of the glow plug 10 to raise the temperature of the heating element. This heats the combustion chamber C and improves the ignitability of the air-fuel mixture. The glow plug 10 to be operated in step S7 is at least the glow plug 10 of the cylinder 2a for which deposits have been confirmed in step S3. However, depending on the engine, on/off switching of the glow plug 10 for each cylinder 2a may not be possible due to the control configuration. In such a case, the PCM 70 activates the glow plugs 10 of all cylinders 2a in step S7. Note that the operation of the glow plug 10 in step S7 is skipped when the determination in step S6 is NO (that is, when the glow plug 10 has already been activated).

Next, the PCM 70 prohibits idling stop of the engine 1 (step S8). The idling stop is control for automatically stopping the engine 1 when predetermined idling stop conditions such as the vehicle speed being zero and the accelerator opening being zero are satisfied. In step S8, the PCM 70 turns on the idle stop prohibition flag so that the engine 1 is not automatically stopped even if the idle stop condition is satisfied. This is to prevent failure in restarting the engine 1 due to deposits.

Next, the PCM 70 changes the idling speed of the engine 1 to a value higher than normal (step S9). Such an increase in the idling speed leads to an increase in rotational inertia of the engine 1 during idling. This makes it difficult for the engine to stall even if the vehicle shifts to idling while deposits remain.

Next, the PCM 70 determines whether or not the engine speed is equal to or less than a predetermined threshold value Nx based on the input information from the crank angle sensor SN1 (step S10). The threshold value Nx is set to an appropriate value higher than the idling speed after the increase in step S9. For example, the threshold Nx may be set at around 1200 rpm.

If the determination in step S10 is YES and it is confirmed that the engine speed is equal to or lower than the threshold value Nx, the PCM 70 changes the opening of the EGR valve 53 to a smaller value than normal (step S11). That is, during the combustion operation of the engine 1, an appropriate amount of EGR gas according to the operating conditions is normally introduced into the combustion chamber C of each cylinder 2a for the purpose of reducing the amount of NOx generated by combustion. , the opening of the EGR valve 53 is controlled. On the other hand, in step S11, the EGR valve 53 is controlled so that the opening of the EGR valve 53 is reduced to a value smaller than the normal opening determined according to the operating conditions. The degree of opening of the EGR valve 53 after the reduction may be set to an appropriate value within a range in which the recirculated amount of EGR gas is smaller than usual. It is also possible to reduce the opening of the EGR valve 53 to the opening corresponding to the fully closed state at which the recirculation of EGR gas is substantially stopped.

Next, the PCM 70 changes the amount of fuel injected by the fuel injection valve 9 to a value larger than normal (step S12). That is, during the combustion operation of the engine 1, each cylinder is controlled so that an appropriate amount of fuel corresponding to the required torque of the engine 1, which is normally determined by the accelerator opening, the vehicle speed, etc., is supplied to the combustion chamber C of each cylinder 2a. The fuel injection valve 9 of 2a is controlled. On the other hand, in the step S12, the fuel injection valve 9 is controlled so as to inject more fuel than the normal injection amount determined according to the required torque. It should be noted that the control for increasing the injection increase in this manner may be performed at least for the fuel injection valves 9 of the cylinders 2a in which deposits have been confirmed in the determination in step S3, but the fuel injection valves 9 of all the cylinders 2a It is also possible to increase the injection amount.

Next, the control when the determination in step S10 is NO, that is, when the engine speed is greater than the threshold value Nx will be described. In this case, the PCM 70 determines whether or not the deposit continues to adhere (step S14). Specifically, the PCM 70 keeps the state (V<Vx) in which the compression state index value V is less than the threshold value Vx for the predetermined number of cycles n2 for the cylinder 2a for which deposits have been determined in step S3. Determine whether or not it has occurred. If the state of V<Vx continues for n2 cycles after the deposit is determined, it means that the same cylinder 2a has compression leakage for n1+n2 cycles, and the deposit is still not removed. means likely. Note that the number n2 of continuous cycles here is preferably larger than the number n1 of continuous cycles used for the determination (determining whether or not a deposit is attached) in step S3. For example, the number n2 of consecutive cycles can be set to "5".

If the determination in step S14 is NO and it is confirmed that the deposit has not continued, the PCM 70 performs normal shift control for the automatic transmission 101 (step S17). It should be noted that since measures against deposits are unnecessary here, control corresponding to steps S15 and S16, which will be described later, is not executed.

On the other hand, if the determination in step S14 is YES and the continuous deposit is confirmed, the PCM 70 reduces the gear position of the automatic transmission 101 (that is, increases the reduction ratio) so that the downshift is performed earlier. to change the shift pattern of the automatic transmission 101 (step S15). That is, the PCM 70 changes the shift pattern so that the downshift rotation speed, which is the engine rotation speed at which downshifting is performed during deceleration, is higher than normal. As a result, downshifting due to deceleration is performed at an earlier timing than usual.

Next, the PCM 70 changes the lockup release rotation speed so that the lockup region, which is the engine rotation speed range in which the lockup clutch 115 is engaged, expands to the low rotation speed side (step S16). That is, the PCM 70 changes the lockup release rotation speed, which is the engine rotation speed at which the engagement of the lockup clutch 115 is released during deceleration, to a value lower than normal. As a result, the lockup region is expanded to the low rotation speed side, and the lockup state is maintained until the engine rotation speed is lower than normal.

In the flowchart of FIG. 5 described above, the control in step S7 corresponds to the "first control" in the present invention, the control in steps S11 and S12 corresponds to the "second control" in the present invention, and step The control of S15 and S16 corresponds to the "third control" in the present invention. Alternatively, the determination of step S3 corresponds to the "first step" of the present invention, the control of step S7 corresponds to the "second step" of the present invention, and the determination of step S10 corresponds to the "third step" of the present invention. Correspondingly, the control of steps S11 and S12 corresponds to the "fourth step" in the present invention.

[Effect]
As described above, in the present embodiment, it is determined whether deposits are attached to the valve seat portion based on the presence or absence of compression leakage estimated from the compression state index value V, and deposits are confirmed. In this case, the control (S7) is executed to heat the combustion chamber C by activating the glow plug 10 . Further, after the operation of the glow plug 10, when it is confirmed that the engine speed is equal to or lower than the threshold value Nx, the control (S11) for reducing the opening degree of the EGR valve 53 is executed, and the fuel injection valve 9 A control (S12) is executed to increase the fuel injection amount from . According to such a configuration, there is an advantage that deposit adhesion can be quickly dealt with while reducing the influence on emission performance or fuel consumption performance.

That is, in the present embodiment, since the glow plug 10 is activated first when deposits are deposited, the activated glow plug 10 quickly heats the combustion chamber C to improve the ignitability of the air-fuel mixture. As a result, it is possible to suppress the ignition failure of the air-fuel mixture caused by the adhesion of deposits (compression leakage), and reduce the possibility of the engine 1 stalling (engine stalling) triggered by the ignition failure.

However, depending on the degree of compression leakage, there is a possibility that the ignition failure cannot be avoided even if the glow plug 10 is operated. In particular, if such a situation occurs in a situation in which the engine speed is relatively low (in other words, a situation in which rotational inertia is low), the possibility of engine stalling increases. In contrast, in this embodiment, when the engine speed after the glow plug 10 is activated is equal to or less than the threshold value Nx, the control for reducing the opening degree of the EGR valve 53 and the control for increasing the fuel injection amount are executed. , it is possible to suppress the occurrence of the engine stall due to the above circumstances. That is, by reducing the opening degree of the EGR valve 53, the ratio of the EGR gas, which is an inert gas, decreases in the combustion chamber C, so that the ignitability of the air-fuel mixture can be improved. Also, the ignitability of the air-fuel mixture can be improved by increasing the fuel injection amount. By combining these effects, it is possible to sufficiently reduce the possibility of poor ignition occurring in a situation where the engine speed is low, and to effectively suppress the occurrence of engine stall.

Moreover, in the present embodiment, the above-described control for changing the opening degree of the EGR valve 53 and the fuel injection amount is not executed unless the engine speed becomes equal to or lower than the threshold value Nx, so the emission performance and the fuel efficiency performance may be affected. can be reduced. That is, the reduction in the opening degree of the EGR valve 53 raises the combustion temperature in the combustion chamber C and has the effect of increasing the amount of NOx produced. Also, an increase in the fuel injection amount has the effect of deteriorating fuel efficiency. On the other hand, in the present embodiment, even if adhesion of deposits (compression leakage) is confirmed, the opening of the EGR valve 53 is not reduced until the engine speed becomes equal to or lower than the threshold value Nx. It is possible to reduce the possibility of an increase in the amount of NOx produced. Similarly, even if deposits are confirmed, the fuel injection amount is not increased until the engine speed becomes equal to or lower than the threshold value Nx. . In particular, in the case where deposits are confirmed in a situation where the engine speed exceeds the threshold value Nx and the glow plug 10 is activated in response to this, the combustion pressure or the like will cause the engine speed to decrease to the threshold value Nx or less. Deposit may be removed. In such a case, it is not necessary to change the opening degree of the EGR valve 53 and the fuel injection amount for countermeasures against deposits, so the influence on the emission performance and the fuel consumption performance can be minimized. Thus, in this embodiment, it is possible to suppress the occurrence of engine stall due to deposits while reducing the influence on the emission performance and fuel consumption performance of the engine 1 .

Further, in the present embodiment, as the compression state index value V described above, the first time T1 required for passage through the first crank angle range ΔC1 straddling the compression top dead center and the second crank angle range ΔC2 included in the expansion stroke. Since the ratio (T1/T2) to the second time T2 required for passage is calculated, by comparing the compression state index value V with the threshold value Vx, the occurrence of compression leakage and, in turn, adhesion of deposits to the valve seat portion can be determined. can be estimated with high accuracy. That is, when compression leakage occurs, the compression reaction force acting on the piston 5 during the compression stroke becomes smaller, so the amount of change in the moving speed of the piston 5 before and after passing the compression top dead center becomes smaller. This means that the difference between the first time T1 and the second time T2 is reduced, in other words, the ratio (T1/T2) between the first time T1 and the second time T2 is reduced. Therefore, according to the present embodiment in which the ratio between the first time T1 and the second time T2 is calculated as the compression state index value V, the compression leakage (and thus the amount of the deposit) can be accurately calculated based on the magnitude of the compression state index value V. adhesion) can be estimated.

Further, in the present embodiment, when it is confirmed that deposits continue to adhere (continuation of compression leakage) while the engine speed is greater than the threshold value Nx after the glow plug 10 is activated, deceleration is performed. The shift pattern is changed so that the engine speed (shift-down speed) at which the downshift to increase the ratio is performed is higher than usual (S15), and the engine speed range in which the lockup clutch 115 is engaged. (lockup region) is expanded to the low rotation speed side (S16). According to such a configuration, it is possible to maintain a high engine speed while the vehicle is running, and reduce the possibility of the engine stalling.

That is, in the present embodiment, the shift pattern is changed so as to increase the downshift rotation speed, so that the downshift is performed earlier than usual when the vehicle decelerates, for example. As a result, the speed reduction ratio can be increased before the engine speed is sufficiently decreased, and the engine speed can be increased by the speed reduction ratio after the increase. In addition, since the lockup region is expanded to the low speed side, the lockup state (the state in which the crankshaft 7 and the wheels W1 are directly connected) is maintained until the engine speed is lower than normal, for example, when decelerating the vehicle. As a result, the crankshaft 7 can be kept rotating in synchronism with the wheels W1, and the rotational energy of the wheels W1 can be used to suppress a decrease in the engine speed. Thus, in this embodiment, the automatic transmission 101 is controlled so that the engine speed is kept relatively high, so that the possibility of engine stalling can be further reduced.

Further, maintaining the engine speed high as described above means that the situation in which the engine speed drops below the threshold value Nx is less likely to occur. This reduces the possibility that the above-described control for changing the opening degree of the EGR valve 53 and the fuel injection amount is required, so that the effects on the emission performance and fuel consumption performance of the engine 1 can be further reduced.

[Modification]
In the above embodiment, as the compression state index value V representing the compression state of the cylinder 2a, the first time T1 required for passing through the first crank angle range ΔC1 straddling the compression top dead center and the second crank angle included in the expansion stroke Although the ratio (T1/T2) to the second time T2 required to pass through the range ΔC2 was calculated, the compression state index value V may be a value that varies depending on the presence or absence of compression leakage, and as long as it is a value that varies, various Change is possible. For example, the difference between the first time T1 and the second time T2 may be used as the compressed state index value V. Alternatively, the first time T1 may be the time required for passing through a predetermined crank angle range included in the compression stroke that is on the advance side of ΔC1 in FIG. It may be the time required to pass through a predetermined crank angle range included in the expansion stroke, which is on the advanced or retarded side of the expansion stroke. Furthermore, in each of the compression stroke and the expansion stroke, the average moving speed of the piston 5 may be calculated from the time required to pass through a specific crank angle range, and the speed ratio between the two may be used as the compression state index value V. good.

In the above embodiment, compression leakage is detected based on the compression state index value V calculated by the PCM 70 from the input information of the crank angle sensor SN1, but means for detecting compression leakage is not limited to this. For example, an in-cylinder pressure sensor that detects the in-cylinder pressure, which is the internal pressure of the cylinder 2a (combustion chamber C), may be provided, and compression leakage may be detected based on the detected value of the in-cylinder pressure sensor. In this case, the in-cylinder pressure sensor corresponds to the "compression leak detector" in the present invention.

In the above-described embodiment, when the engine speed after deposit adhesion (compression leakage) is confirmed is equal to or lower than the threshold value Nx, control (S11) to reduce the opening of the EGR valve 53, and However, it is not necessary to execute both of these two controls, and only one of them may be executed. Even in this case, ignitability can be improved and engine stalling can be suppressed.

In the above embodiment, even if the engine speed is greater than the threshold value Nx, if it is confirmed that deposits continue to adhere (compression leakage is still occurring), the downshift speed is set to normal. Control (S15) to change the shift pattern so that it becomes higher than normal and control (S16) to lower the lockup release rotation speed than usual are executed respectively, but both of these two controls are executed. either control may be performed. Even in this case, engine stalling can be suppressed by maintaining the engine speed high.

In the above-described embodiment, when deposit adhesion (compression leakage) is confirmed during deceleration fuel cut, the opening of the intake shutter valve 33 is changed to a value larger than normal (step S5). In addition to the control, or instead of the control, a control (similar to steps S15 and S16 described above) for changing the control pattern of the automatic transmission 101 so as to keep the engine speed high may be executed. good.

In the above embodiment, an example in which the present invention is applied to a diesel engine that burns fuel containing light oil by self-ignition was described, but if it has a heating means corresponding to the glow plug 10, an engine other than a diesel engine The present invention can also be applied to

1: Engine C: Combustion chamber 7: Crankshaft (output shaft)
9: Fuel injection valve 10: Glow plug 11: Intake port 12: Exhaust port 13: Intake valve 14: Exhaust valve 30: Intake passage 40: Exhaust passage 50: EGR passage 53: EGR valve 70: PCM (controller, compression leak detection part)
SN1: Crank angle sensor (rotation detector, compression leak detector)
101: Automatic transmission 115: Lockup clutch

Claims (5)

a combustion chamber, an intake passage connected to the combustion chamber via an intake port, an exhaust passage connected to the combustion chamber via an exhaust port, an intake valve for opening and closing the intake port and the exhaust port, and an exhaust A device for controlling an engine comprising a valve and an EGR passage connecting the intake passage and the exhaust passage,
a fuel injection valve that injects fuel into the combustion chamber;
a glow plug that heats the combustion chamber;
an EGR valve provided in the EGR passage so as to be openable and closable;
a rotation detection unit that detects an engine rotation speed, which is the rotation speed of the output shaft of the engine;
a compression leak detector that detects compression leak, which is a phenomenon in which air leaks from the combustion chamber through the intake port or the exhaust port during a compression stroke;
A controller that controls the fuel injection valve, the glow plug, and the EGR valve,
The controller is
performing a first control for operating the glow plug to heat the combustion chamber when the compression leak detection unit detects a compression leak;
After the first control, when it is confirmed that the engine speed detected by the rotation detection unit is equal to or less than a predetermined threshold value, the opening degree of the EGR valve is reduced and the fuel from the fuel injection valve is reduced. A control device for an engine that executes second control involving at least one of increasing the injection amount. In the engine control device according to claim 1,
The compression leakage detection unit includes a first time required for passing through a first crank angle range that is included in a compression stroke or straddles compression top dead center, and is included in an expansion stroke immediately after the compression stroke and is included in the first crank angle. and a second time required for passing through a second crank angle range on the retard side of the crank angle range to detect the compression leakage. In the engine control device according to claim 1 or 2,
The engine is an in-vehicle engine connected to wheels via an automatic transmission capable of automatically changing the reduction ratio,
After the first control, when it is confirmed that the compression leak has occurred while the engine speed is greater than the threshold value, the controller maintains the engine speed high. An engine control device that executes third control for controlling an automatic transmission. In the engine control device according to claim 3,
The automatic transmission includes a lockup clutch that directly connects the output shaft of the engine and the wheels,
The third control includes a control for expanding a lockup region, which is a range of engine speeds in which the lockup clutch is engaged, to a low speed side, and an engine speed at which downshifting to increase the reduction ratio is performed. a control device for an engine, including at least one of controls for changing the shift pattern so that the a combustion chamber, an intake passage connected to the combustion chamber via an intake port, an exhaust passage connected to the combustion chamber via an exhaust port, an intake valve for opening and closing the intake port and the exhaust port, and an exhaust an EGR passage that connects the intake passage and the exhaust passage; a fuel injection valve that injects fuel into the combustion chamber; a glow plug that heats the combustion chamber; A method of controlling an engine comprising an EGR valve comprising:
a first step of detecting compression leakage, which is a phenomenon in which air leaks from the combustion chamber through the intake port or the exhaust port during a compression stroke;
a second step of operating the glow plug to heat the combustion chamber when the compression leak is detected in the first step;
After the second step, a third step of detecting the engine speed, which is the speed of the output shaft of the engine;
At least one of reducing the opening degree of the EGR valve and increasing the fuel injection amount from the fuel injection valve when it is confirmed that the engine speed detected in the third step is equal to or less than a predetermined threshold value. and a fourth step of performing

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