Engine control device and control method

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

Technical Field

[0001] The present invention relates to a technique for controlling an engine provided with an intake valve and an exhaust valve.

Background Art

[0002] Deposits may adhere (bite in) between the intake valve and the valve seat, or between the exhaust valve and the valve seat. The adhesion of deposits causes compression leakage in which compressed air leaks from the combustion chamber through the intake port or the exhaust port. The compression leakage causes misfiring in which the air-fuel mixture in the combustion chamber does not burn properly (or misfires).

[0003] As an engine with measures against the above-described deposit adhesion, the one disclosed in Patent Document 1 below is known. In the engine of Patent Document 1, the presence or absence of deposit adhesion is determined during deceleration fuel cut, and when deposit adhesion is determined, control such as increasing the opening degree of the intake shutter valve is executed. Increasing the opening degree of the intake shutter valve has the effect of increasing the pressure in the combustion chamber and increasing the possibility that the deposits are crushed (removed).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, in Patent Document 1, deposit adhesion determination and its countermeasure control are performed only during deceleration fuel cut. In other words, during the combustion operation of the engine, that is, during the operation accompanied by the combustion of the air-fuel mixture in the combustion chamber, even if deposit adhesion occurs, no particular countermeasures are taken. For this reason, there is a concern that the deposit countermeasures may be delayed. That is, even if deposits adhere during the combustion operation of the engine, no countermeasures are taken until the operation mode subsequently shifts to deceleration fuel cut, so there is a possibility that compression leakage and misfiring caused by the deposits may continue for some time. In particular, when deposits adhere while the engine is in an idle state or a low rotation state close to it, compression leakage and misfiring may occur in a state where the engine's rotational inertia is low, which may cause the engine to stall (engine stall).

[0006] Therefore, it is proposed to take some deposit countermeasures even during the combustion operation of the engine. However, depending on the content of the countermeasures, they may affect the emission performance or fuel consumption performance of the engine, so it is desirable to take appropriate countermeasures considering these effects.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine control device capable of quickly taking deposit countermeasures while reducing the impact on emission performance or fuel consumption performance.

Means for Solving the Problems

[0008] As a solution to the above problems, an engine control device according to an 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, and an EGR passage that connects the intake passage and the exhaust passage. The device controls an engine, and includes 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 detection unit that detects a 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, and a controller that controls the fuel injection valve, the glow plug, and the EGR valve. When the compression leak detection unit detects a compression leak, the controller executes a first control of operating the glow plug to heat the combustion chamber. After the first control, when it is confirmed that the engine rotation speed detected by the rotation detection unit is equal to or lower than a predetermined threshold value, the controller executes a second control involving at least one of reducing the opening degree of the EGR valve and increasing the fuel injection amount from the fuel injection valve.

[0009] The fact that a compression leak is detected highly likely means 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, first, the glow plug is operated, so that the operated glow plug can quickly heat the combustion chamber to improve the ignitability of the air-fuel mixture. Thereby, it is possible to suppress a misfire of the air-fuel mixture caused by the attachment of deposits (compression leak), and it is possible to reduce the possibility that the engine stalls (engine stall occurs) due to the misfire.

[0010] However, depending on the degree of compression leakage, there is a possibility that misfire cannot be avoided even if the glow plug is operated. In particular, when such a situation occurs in a situation where the engine speed is relatively low (in other words, the rotational inertia is low), the likelihood of engine stall increases. On the other hand, in the present invention, when the engine speed after glow plug operation is below a predetermined threshold value, control to reduce the opening degree of the EGR valve or control to increase the fuel injection amount is executed, so that the occurrence of engine stall due to the above circumstances can be suppressed. That is, when the opening degree of the EGR valve is reduced, as a result, the proportion of EGR gas, which is an inert gas, decreases in the combustion chamber, and the ignitability of the air-fuel mixture is improved. Also, when the fuel injection amount is increased, the ignitability of the air-fuel mixture is also improved. Thereby, the possibility of misfire occurring in a situation where the engine speed is low can be reduced, and the occurrence of engine stall can be effectively suppressed.

[0011] 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 becomes below the threshold value, so the possibility of affecting emission performance or fuel consumption performance can be reduced. That is, reducing the opening degree of the EGR valve has the effect of increasing the combustion temperature in the combustion chamber and increasing the amount of NOx generated. Also, increasing the fuel injection amount has the effect of degrading the fuel consumption performance. On the other hand, in the present invention, even if compression leakage is confirmed, these measures are not taken until the engine speed becomes below the threshold value, so the possibility of an increase in the amount of NOx generated or a decrease in fuel consumption performance can be reduced. In particular, when compression leakage is confirmed in a situation where the engine speed exceeds the threshold value and the glow plug operates in response to this, there is a possibility that deposits are removed by combustion pressure or the like before the engine speed becomes below the threshold value. In such a case, it is not necessary to change the opening degree of the EGR valve or the fuel injection amount for deposit countermeasures in the first place, so the influence on emission performance or fuel consumption performance 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 consumption performance of the engine.

[0012] Preferably, the compression leakage detection unit detects the compression leakage based on a first time required for passing through a first crank angle range included in a compression stroke or straddling a top dead center of compression, and a second time required for passing through a second crank angle range included in an expansion stroke immediately following the compression stroke and on a retarded angle side of the first crank angle range.

[0013] According to this configuration, 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, it is possible to accurately detect compression leakage. That is, when compression leakage occurs, the compression reaction force acting on the piston during the compression stroke becomes small, so the amount of change in the moving speed of the piston before and after passing through the top dead center of compression becomes small, and a change occurs in the relationship between the first time and the second time. According to the above configuration, it is possible to accurately detect compression leakage by utilizing this fact.

[0014] The engine can be an in-vehicle engine connected to wheels via an automatic transmission capable of automatically changing the reduction ratio. In this case, when it is confirmed that the compression leakage has occurred while the engine speed is greater than the threshold value after the first control, the controller preferably executes a third control for controlling the automatic transmission so that the engine speed is maintained high.

[0015] According to this configuration, it is possible to maintain a high engine speed during vehicle travel by controlling the automatic transmission, and it is possible to reduce the possibility of engine stall.

[0016] The automatic transmission may include a lock-up clutch that directly connects the output shaft of the engine and the wheels. In this case, the third control preferably includes at least one of a control for expanding the lock-up region, which is a range of engine speeds at which the lock-up clutch is engaged, to the low rotation side, and a control for changing the shift pattern so that the engine speed (shift-down engine speed) at which a downshift for increasing the reduction ratio is performed becomes higher.

[0017] When the shift pattern is changed so that the shift-down rotation speed increases, for example, when the vehicle decelerates, the shift-down is performed at an earlier timing than usual. As a result, the reduction ratio can be increased before the engine rotation speed sufficiently decreases, and the engine rotation speed can be increased by the increased reduction ratio. Also, when the lock-up region is expanded to the low rotation side, for example, when the vehicle decelerates, the lock-up state (a state where the output shaft of the engine and the wheels are directly connected) is maintained up to a lower engine rotation speed than usual. Thereby, a state where the output shaft of the engine rotates in synchronization with the wheels can be maintained, and the decrease in the engine rotation speed can be suppressed by using the rotational energy of the wheels. In any case, since the engine rotation speed is relatively maintained high, the possibility of engine stalling can be reduced.

[0018] A method for controlling an engine according to another aspect of the present invention is a method for controlling an engine including 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 for opening and closing the intake port and the exhaust port, an EGR passage connecting the intake passage and the exhaust passage, a fuel injection valve for injecting fuel into the combustion chamber, a glow plug for heating the combustion chamber, and an EGR valve provided in the EGR passage so as to be openable and closable, the method including: a first step of detecting a 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 second step of operating the glow plug to heat the combustion chamber when the compression leak is detected in the first step; a third step of detecting an engine rotation speed, which is the rotation speed of the output shaft of the engine, after the second step; and a fourth step of performing 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 rotation speed detected in the third step is equal to or lower than a predetermined threshold value.

[0019] Also, by the invention of this control method, the same effects as those of the invention of the above-described control device can be obtained.

Advantages of the Invention

[0020] As described above, according to the engine control device and control method of the present invention, it is possible to quickly take measures against deposits while reducing the influence on emission performance or fuel consumption performance.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0022] [Overall Configuration of Engine] FIG. 1 is a system diagram showing the overall configuration of an engine to which a control device according to an embodiment of the present invention is applied. The 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, an EGR device 50 that recirculates a part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30, and a supercharger 60 that supercharges the intake air flowing through the intake passage 30.

[0023] The engine body 2 is 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. The cylinders 2a are formed by the cylinder block 3 and the 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 close the cylindrical space from above. The piston 5 is reciprocally slidably accommodated in each cylinder 2a. In the present embodiment, the side from the cylinder block 3 toward the cylinder head 4 is regarded as the upper side and the reverse side is regarded as the lower side for convenience of explanation, but this is for convenience of explanation and does not limit the installation posture of the engine body 2.

[0024] Above the piston 5 of each cylinder 2a, a combustion chamber C is formed. 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 2a, and the upper surface (crown surface) of the piston 5. The combustion chamber C receives the supply of fuel injected from a fuel injection valve 9 described later. The piston 5 reciprocates in the vertical direction by receiving the combustion energy of the fuel supplied to the combustion chamber C. Since the engine 1 of the present embodiment is a diesel engine, a fuel containing light oil is used as the fuel supplied to the combustion chamber C.

[0025] A crankshaft 7, which is an output shaft of the engine body 2, is provided below 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 in accordance with the reciprocating motion (vertical motion) of the piston 5.

[0026] The cylinder block 3 is equipped with a crank angle sensor SN1 and a water temperature sensor SN2. 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 number of rotations of the crankshaft 7. The water temperature sensor SN2 is a sensor that detects the temperature of the cooling water flowing inside the cylinder block 3 and the cylinder head 4, that is, the engine water temperature. Note that the crank angle sensor SN1 corresponds to the "rotation detection unit" in the present invention.

[0027] The cylinder head 4 is equipped with a fuel injection valve 9 and a glow plug 10. 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.

[0028] The fuel injection valve 9 is attached to the cylinder head 4 such that its tip portion is exposed to the combustion chamber C. A plurality of injection holes (not shown), which are outlets for fuel, are formed at the tip portion of the fuel injection valve 9. The fuel injected from each injection hole burns by auto-ignition in the combustion chamber C that has been heated to high temperature and high pressure by the compression action of the piston 5.

[0029] The glow plug 10 is attached to the cylinder head 4 such that its tip portion is exposed to the combustion chamber C. The tip portion of the glow plug 10 is provided with a heating element (not shown) that generates heat when energized. The heating element is heated to a high temperature in a short time when energized and heats the combustion chamber C.

[0030] 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 startup, that is, the temperature detected by the water temperature sensor SN2 at startup of the engine 1, is equal to or lower than a predetermined first temperature. Also, after the engine 1 has completed startup, the operation of the glow plug 10 (heating of the combustion chamber C) continues until the engine water temperature reaches a second temperature higher than the first temperature.

[0031] The cylinder head 4 is formed with an intake port 11 and an exhaust port 12. The intake port 11 is a port that communicates the combustion chamber C of each cylinder 2a with the intake passage 30. The exhaust port 12 is a port that communicates the combustion chamber C of each cylinder 2a with the exhaust passage 40. An intake valve 13 is provided at the intake port 11 of each cylinder 2a, and an exhaust valve 14 is provided at the exhaust port 12 of each cylinder 2a.

[0032] The cylinder head 4 is equipped with an intake valve actuating mechanism 15 and an exhaust valve actuating mechanism 16. The intake valve actuating mechanism 15 is a mechanism that opens and closes the intake valve 13 of each cylinder 2a in conjunction with the rotation of the crankshaft 7. The exhaust valve actuating 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. The intake valve 13 periodically opens and closes the opening on the combustion chamber C side of the intake port 11 in response to the drive of the intake valve actuating mechanism 15. The exhaust valve 13 periodically opens and closes the opening on the combustion chamber C side of the exhaust port 12 in response to the drive of the exhaust valve actuating mechanism 16.

[0033] 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 in a downstream portion close to the engine body 2. The surge tank 30b is a tank that provides an enlarged space for equalizing the intake air introduction amount to each cylinder 2a. The intake manifold 30a includes a plurality of branch pipes that connect the surge tank 30b and the intake port 11 of each cylinder 2a. Note that the portion of the intake passage 30 upstream of the surge tank 30b is formed in a single tubular shape.

[0034] In the portion of the intake passage 30 upstream of the surge tank 30b, an air cleaner 31, an intercooler 32, and an intake shutter valve 33 are provided. The air cleaner 31 is a filter that removes foreign matter in the intake air. The intercooler 32 is a heat exchanger that cools the intake air compressed by the supercharger 60. The intake shutter valve 33 is an electric butterfly valve that is openably and closably provided in the intake passage 30 to throttle the intake air flow rate. The air cleaner 31, the intercooler 32, and the intake shutter valve 33 are arranged in this order from the far upstream side of the engine body 2.

[0035] An air flow sensor SN3 and an intake pressure sensor SN4 are attached to the intake passage 30. The air flow sensor SN3 is a sensor that detects the flow rate of the 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. The intake pressure sensor SN4 is a sensor that detects the pressure of the intake air introduced into the engine body 2, and is arranged in the surge tank 30b.

[0036] 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 the upstream portion close to the engine body 2. Although detailed illustration is omitted, the exhaust manifold 40a includes a plurality of branch pipes communicating with the exhaust ports 12 of each cylinder 2a and an exhaust collecting portion where the branch pipes converge. Note that the portion of the exhaust passage 40 downstream of the exhaust manifold 40a (exhaust collecting portion) is formed in a single tubular shape.

[0037] A catalyst device 41 is provided in the portion of the exhaust passage 40 downstream of the exhaust manifold 40a. The catalyst device 41 incorporates an oxidation catalyst 41a that oxidizes and detoxifies CO and HC in the exhaust gas, and a DPF (Diesel Particulate Filter) 41b that collects particulate matter contained in the exhaust gas.

[0038] The supercharger 60 is a so-called two-stage supercharger, and includes a first supercharger 61 and a second supercharger 62 arranged in series.

[0039] The first supercharger 61 is a turbo supercharger 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. The first compressor 61a is arranged in a portion between the air cleaner 31 and the intercooler 32 in the intake passage 30. The first turbine 61b is arranged in a portion upstream of the catalytic device 41 in the exhaust passage 40.

[0040] Similarly, the second supercharger 62 is a turbo supercharger 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. The second compressor 62a is arranged in a portion downstream of the first compressor 61a in the intake passage 30, that is, in a portion between the first compressor 61a and the intercooler 32. The second turbine 62b is arranged in a portion upstream of the first turbine 61b in the exhaust passage 40.

[0041] The first supercharger 61 is a turbo supercharger larger than the second supercharger 62. That is, the first compressor 61a and the first turbine 61b are formed in a larger size than the second compressor 62a and the second turbine 62b.

[0042] 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 openable and closable.

[0043] The exhaust passage 40 is connected to a first exhaust bypass passage 64 and a second exhaust bypass passage 65. 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 wastegate valve 64a is provided in the first exhaust bypass passage 64 so as to be openable and closable. An electric regulating valve 65a is provided in the second exhaust bypass passage 65 so as to be openable and closable.

[0044] When supercharging is performed by the first supercharger 61, the wastegate valve 64a is closed. Thereby, 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 pump the intake air to the downstream side. That is, supercharging that compresses the intake air in the intake passage 30 and sends it out to the engine body 2 is realized by the first supercharger 61.

[0045] When supercharging is performed by the second supercharger 62, the regulating valve 65a and the bypass valve 63a are closed. Thereby, 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 pump the intake air to the downstream side. That is, supercharging that compresses the intake air in the intake passage 30 and sends it out to the engine body 2 is realized by the second supercharger 62.

[0046] 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 upstream of the second turbine 62b in the exhaust passage 40 and a portion between the intake shutter valve 33 and the surge tank 30b in the intake passage 30 to each other. 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 electric valve provided in the EGR passage 51 to adjust the recirculation amount of exhaust gas, that is, the EGR amount. The EGR valve 53 is disposed downstream of the EGR cooler 52 in the EGR passage 51 (the side closer to the intake passage 30).

[0047] [Details of Intake and Exhaust Valves] FIG. 2 is a cross-sectional view showing details of the intake and exhaust valves 13, 14 of the engine body 2 and their valve operating mechanisms 15, 16. As shown in this figure, the intake valve 13 has a stem portion 13a and an umbrella 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 umbrella portion 13b is a disk-shaped member capable of closing the opening on the combustion chamber C side of the intake port 11 and is formed so as to have an enlarged diameter from the lower end of the stem portion 13a.

[0048] 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 on the combustion chamber C side of the exhaust port 12 and is formed so as to have an enlarged diameter from the lower end of the stem portion 14a.

[0049] The cylinder head 4 is attached with valve seats 11a and 12a. The valve seat 11a is a ring-shaped member attached to the opening on the combustion chamber C side of the intake port 11, and is in close contact with the periphery of the umbrella portion 13b when the intake valve 13 is closed. The valve seat 12a is a ring-shaped member attached to the opening on the combustion chamber C side of the exhaust port 12, and is in close contact with the periphery of the umbrella portion 14b when the exhaust valve 14 is closed.

[0050] The intake valve operating 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 includes a shaft portion 21a extending in the direction of the arrangement of the cylinders 2a (the direction perpendicular to the plane of FIG. 2), and a plurality of cam portions 21b provided at positions corresponding to the intake valves 13 of the respective cylinders 2a on the shaft portion 21a. 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 in a state of biasing the intake valve 13 in the closing direction (upward). The intake valve 13 periodically opens under the downward pressing force transmitted from the cam portion 21b via the swing arm 23 as the camshaft 21 rotates. On the other hand, when the pressing force is not acting, the intake valve 13 is maintained in a closed state where the umbrella portion 13b is in close contact with the valve seat 11a by the upward biasing force of the valve spring 25.

[0051] Similarly, the exhaust valve mechanism 16 includes a camshaft 22, a swing arm 24, and a valve spring 26. The camshaft 22 is a rotatable shaft linked to the crankshaft 7 via the transmission member. Specifically, the camshaft 22 includes a shaft portion 22a extending in the arrangement direction of the cylinders 2a (the direction orthogonal to the plane of FIG. 2), and a plurality of cam portions 22b provided at positions corresponding to the exhaust valves 14 of the respective cylinders 2a on the shaft portion 22a. The swing arm 24 is swingably supported below the cam portions 22b of the respective cylinders 2a. The valve spring 26 is attached to the cylinder head 4 in a state of biasing the exhaust valve 14 in the closing direction (upward). The exhaust valve 14 periodically opens upon receiving a downward pressing force transmitted from the cam portion 22b via the swing arm 24 as the camshaft 22 rotates. On the other hand, when the pressing force is not acting, the exhaust valve 14 is maintained in a closed state where the umbrella portion 14b is in close contact with the valve seat 12a by the upward biasing force of the valve spring 26.

[0052] [Power system] FIG. 3 is a plan view schematically showing the structure of a power transmission system that transmits the output of the engine 1 described above to the vehicle wheel W1. The vehicle is a front-engine, rear-wheel-drive (FR type) vehicle here. Therefore, in FIG. 3, the wheel W1 is a rear wheel, and the engine body 2 is arranged in an engine room at the front of the vehicle. Although FIG. 3 illustrates an in-line four-cylinder type engine body 2 having four cylinders 2a arranged in a row, the number and arrangement of the cylinders 2a can be changed as appropriate.

[0053] 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, a differential device 103 connected to the rear end of the propeller shaft 102, and a pair of drive shafts 104 extending left and right from the differential device 103. Wheels W1 are respectively attached to the ends in the vehicle width direction of each drive shaft 104. The output rotation of the engine body 2 is transmitted to the differential device 103 via the propeller shaft 102 after being shifted by the automatic transmission 101. The rotation input to the differential device 103 is transmitted to each wheel W1 via the left and right drive shafts 104.

[0054] The automatic transmission 101 includes a torque converter 110 and a transmission main body 120. The torque converter 110 is a fluid clutch that transmits the output rotation of the engine body 2, that is, the rotation of the crankshaft 7, to the transmission main body 120 via a working fluid (ATF). The transmission main body 120 is a device that transmits the rotation input from the torque converter 110 to the wheels W1 while shifting the rotation.

[0055] The torque converter 110 incorporates a pump impeller 111 that rotates integrally with the crankshaft 7 of the engine body 2, a turbine runner 112 disposed opposite to the pump impeller 111, and a stator 113 disposed between the pump impeller 111 and the turbine runner 112. The rotation of the pump impeller 111 is transmitted to the turbine runner 112 via the working fluid in the torque converter 110. The rotation of the turbine runner 112 is input to the transmission main body 120 via the turbine shaft 114.

[0056] Inside the torque converter 110, a lock-up clutch 115 is provided. The lock-up 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 engaging the lock-up clutch 115, a state is obtained in which the crankshaft 7 and the turbine shaft 114 (the input shaft of the transmission body 120) are mechanically connected without passing through a fluid, and the rotation of the crankshaft 7 is directly transmitted to the wheels W1. In other words, the lock-up clutch 115 is a clutch that directly connects the output shaft (crankshaft 7) of the engine 1 and the wheels W1.

[0057] Engaging the lock-up clutch 115 leads to an improvement in power transmission efficiency. However, when the lock-up clutch 115 is engaged when the engine speed or vehicle speed is low, the vibration of the engine 1 is likely to be transmitted to the vehicle. For this reason, the lock-up clutch 115 is engaged under predetermined conditions except when the engine speed or vehicle speed is low, and is released (disengaged) when the engine speed or vehicle speed is low.

[0058] The transmission body 120 incorporates a multi-stage transmission mechanism 121 capable of achieving a plurality of gear stages with different reduction ratios. The transmission mechanism 121 includes a gear mechanism 122 formed by combining a plurality of planetary gear sets, a plurality of friction engagement elements (not shown) including clutches and brakes that are engaged or released to switch the power transmission path by the gear mechanism 122, and a hydraulic control valve 123 (FIG. 4) including a solenoid valve that controls the hydraulic pressure supplied to each friction engagement element to switch its engagement / disengagement. By appropriately engaging and releasing the friction engagement elements by the hydraulic control valve 123, a desired gear stage corresponding to the speed of the vehicle and the like is achieved in the transmission mechanism 121. 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 to the wheels W1) after being shifted at a reduction ratio corresponding to the gear stage of the transmission mechanism 121.

[0059] [Control System] Figure 4 is a functional block diagram showing the control systems of the engine 1 and the automatic transmission 101 described above. The PCM 70 shown in this figure is a microprocessor for comprehensively controlling the engine 1 and the automatic transmission 101, and is composed of a well-known CPU, ROM, RAM, etc. The PCM 70 corresponds to the "controller" in the present invention.

[0060] Detection information from various sensors is input to the PCM 70. For example, the PCM 70 is electrically connected to the crank angle sensor SN1, the water temperature sensor SN2, the air flow sensor SN3, and the intake pressure sensor SN4 described above. Information detected by each of these sensors (that is, information such as crank angle, engine speed, engine water temperature, intake air flow, and intake pressure) is sequentially input to the PCM 70.

[0061] In addition, an accelerator sensor SN5 and a vehicle speed sensor SN6 are provided in the vehicle. The accelerator sensor SN5 is a sensor that detects the opening of the accelerator pedal, that is, the accelerator opening, which is operated by the driver driving the vehicle. The vehicle speed sensor SN6 is a sensor that detects the traveling speed of the vehicle, that is, the vehicle speed. Detection information from these accelerator sensor SN5 and vehicle speed sensor SN6 is also sequentially input to the PCM 70.

[0062] The PCM 70 controls each part of the engine 1 and the automatic transmission 101 based on the input information from the respective 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 waste gate valve 64a, and the regulator valve 65a described above, and is also electrically connected to the lock-up clutch 115 and the hydraulic control valve 123 of the automatic transmission 101. The PCM 70 outputs a control signal generated based on the input information from the respective sensors SN1 to SN6 to these devices.

[0063] [Measures against Deposit Adhesion] Here, deposits (foreign substances) 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 peel off at some point and flow downstream, and may get caught between the umbrella portion 13b of the intake valve 13 and the valve seat 11a. Alternatively, deposits that have flowed into the combustion chamber C may also get caught between the umbrella portion 14b of the exhaust valve 14 and the valve seat 12a. Such adhesion (entrapment) of deposits to 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, it becomes easy for misfiring to occur, in which the air-fuel mixture injected into the combustion chamber C does not burn properly (or misfires). Therefore, in the present embodiment, as a countermeasure against deposit adhesion to the valve seat portion, control as shown in FIG. 5 is executed by the PCM 70. Hereinafter, the details of this control will be described.

[0064] FIG. 5 is a flowchart showing the details of the control executed by the PCM 70 during the operation of the engine 1 in which the crankshaft 7 rotates. When the control starts, the PCM 70 reads the information output from the respective sensors SN1 to SN6 (step S1).

[0065] 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) of the first time T1 and the second time T2 shown in FIG. 6 as the compression state index value V. The first time T1 is the time required for passing through the first crank angle range ΔC1 spanning from the compression stroke to the expansion stroke, and the second time T2 is the time required for passing through the second crank angle range ΔC2 included in the expansion stroke immediately following the compression stroke. The PCM 70 calculates the compression state index value V (= T1 / T2), which is the value obtained by dividing the former by the latter, for each combustion cycle of each cylinder 2a. Note that the compression state index value V can be calculated based on the input information from the crank angle sensor SN1.

[0066] More specifically, the first crank angle range ΔC1 is set to a predetermined angular range sandwiching the 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 a predetermined angular range that is separated from the first crank angle range ΔC1 toward the retarded angle side and 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) on FIG. 6. Here, the moving speed of the piston 5 passing through the second crank angle range ΔC2 becomes 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 maximizes at the compression top dead center, and the expansion force that accelerates the piston 5 acts during the expansion stroke. And the fact that the passing speed of the second crank angle range ΔC2 is faster than the passing speed of the first crank angle range ΔC1 as described above means that the second time T2 which is the passing time of the second crank angle range ΔC2 becomes shorter than the first time T1 which is the passing time of the first crank angle range ΔC1. Therefore, the compression state index value V calculated as T1 / T2 as described above is usually calculated as a value significantly larger than 1.

[0067] However, when compressed air leaks from the combustion chamber C through the intake port 11 or the exhaust port 12 during the compression stroke, that is, when compression leakage occurs, the compression reaction force acting on the piston 5 during the compression stroke becomes smaller, so the difference between the first time T1 and the second time T2 shrinks. This means that the compression state index value V (=T1 / T2), which is the ratio of the two, approaches 1. 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 (the presence or absence of compression leakage) of each cylinder 2a by calculating the compression state index value V having such a property for each combustion cycle of each cylinder 2a.

[0068] Thus, in the present 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. From this, the combination of the crank angle sensor SN1 and the PCM 70 corresponds to the "compression leakage detection unit" in the present invention.

[0069] After calculating the compression state index value V in the step S2, the PCM 70 determines whether or not a deposit is 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, and determines whether the former is less than the latter, that is, whether V<Vx is established. And when the state where V<Vx is established, that is, the state where 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, it is determined that a deposit is attached to the valve seat portion (between the intake valve 13 and the valve seat 11a or between the exhaust valve 14 and the valve seat 12a) of the cylinder 2a. Note that the continuous cycle number n1 here can be set to, for example, "2".

[0070] The threshold value Vx used in the determination of the step S3 is determined from the average value of the compression state index values V of all the cylinders 2a calculated one cycle before. That the compression state index value V of a specific cylinder 2a is small with respect to such a threshold value Vx means that there is a high possibility that compression leakage has occurred in the specific cylinder 2a, that is, there is a high possibility that compressed air leaks from the combustion chamber C due to the deposit attached to the valve seat portion of the specific cylinder 2a. Therefore, the PCM 70 determines that a deposit is attached to the cylinder 2a when the above-described state of V<Vx occurs continuously for n1 cycles for the same cylinder 2a.

[0071] When it is determined as NO in the step S3, that is, when it is confirmed that no deposit is attached to the valve seat portion of any of the cylinders 2a, the PCM 70 executes normal engine control (step S13). Note that since deposit countermeasures are not required here, the controls corresponding to steps S8, S9, S11, and S12 described later are not executed.

[0072] On the one hand, if it is confirmed in step S3 that deposits are attached to the valve seat portion of any of the cylinders 2a, that is, if it is confirmed that deposits are caught between the intake valve 13 (or exhaust valve 14) and the valve seat 11a (or 12a) of the cylinder 2a, the PCM 70 determines whether the engine 1 is in deceleration fuel cut (step S4). 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 the rotation of the crankshaft 7 is maintained by utilizing the rotation of the wheel W1. Such deceleration fuel cut is permitted, for example, when all of the conditions 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 higher than a predetermined reference speed are satisfied. The PCM 70 determines based on the input information from the crank angle sensor SN1, the accelerator sensor SN5, and the vehicle speed sensor SN6 whether such deceleration fuel cut permission conditions are satisfied, and executes deceleration fuel cut when the conditions are satisfied.

[0073] If it is determined in step S4 that YES and it is confirmed that deceleration fuel cut is being executed, the PCM 70 changes the opening degree of the intake shutter valve 33 to a value larger than normal (step S5). That is, during deceleration fuel cut, usually, for the purpose of utilizing engine braking, etc., the opening degree of the intake shutter valve 33 is set to a relatively small value. In contrast, in step S5, the intake shutter valve 33 is controlled so that the opening degree of the intake shutter valve 33 increases to a value larger than the normal opening degree during deceleration fuel cut. This is to increase the in-cylinder pressure, which is the internal pressure of the cylinder 2a (combustion chamber C), and enhance the possibility that the deposits attached to the valve seat portion are crushed.

[0074] On the one hand, when it is determined as NO in step S4 and it is confirmed that deceleration fuel cut is not being executed, that is, when it is confirmed that an operation involving combustion of the air-fuel mixture (combustion operation) is being performed, the PCM 70 determines whether the glow plug 10 is inoperative (step S6). That is, the PCM 70 checks the energization state of the heating element of the glow plug 10 and determines that the glow plug 10 is inoperative when energization is not being performed.

[0075] When it is determined as YES in step S6 and it is confirmed that the glow plug 10 is inoperative, 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 increase the temperature of the heating element. Thereby, the combustion chamber C is heated and the ignitability of the air-fuel mixture is improved. Note that the glow plug 10 to be activated in step S7 is at least the glow plug 10 of the cylinder 2a where deposit adhesion was confirmed in the determination of step S3. However, depending on the engine, due to the control configuration, it may not be possible to switch the on / off of the glow plug 10 for each cylinder 2a. In such a case, the PCM 70 activates the glow plugs 10 of all the cylinders 2a in step S7. Note that the activation 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 is already activated).

[0076] Next, the PCM 70 prohibits the idling stop of the engine 1 (step S8). Idling stop is control to automatically stop 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 idling stop prohibition flag so that the engine 1 is not automatically stopped even when the idling stop conditions are satisfied. This is to prevent the engine 1 from failing to restart due to deposit adhesion.

[0077] Next, the PCM 70 changes the idle speed of the engine 1 to a value higher than normal (step S9). Such an increase in the idle speed leads to an increase in the rotational inertia of the engine 1 during idle operation. As a result, it becomes less likely for the engine to stall even when shifting to idle operation with deposits attached.

[0078] Next, the PCM 70 determines whether or not the engine speed is equal to or lower 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 idle speed after the increase in step S9. For example, the threshold value Nx can be set to about 1200 rpm.

[0079] When it is determined as YES in step S10 and it is confirmed that the engine speed is equal to or lower than the threshold value Nx, the PCM 70 changes the opening degree of the EGR valve 53 to a value smaller than normal (step S11). That is, during the combustion operation of the engine 1, usually, for the purpose of reducing the amount of NOx generated by combustion, etc., the opening degree of the EGR valve 53 is controlled so that an appropriate amount of EGR gas according to the operating conditions is introduced into the combustion chamber C of each cylinder 2a. In contrast, in step S11, the EGR valve 53 is controlled so that the opening degree of the EGR valve 53 decreases to a value smaller than the normal opening degree determined according to the operating conditions. The opening degree of the EGR valve 53 after the decrease may be set to an appropriate value within the range where the recirculation amount of the EGR gas decreases more than normal. It is also possible to decrease the opening degree of the EGR valve 53 to an opening degree equivalent to fully closed where the recirculation of the EGR gas is substantially stopped.

[0080] Next, the PCM 70 changes the fuel injection amount by the fuel injection valve 9 to a value larger than normal (step S12). That is, during the combustion operation of the engine 1, usually, the fuel injection valves 9 of the respective cylinders 2a are controlled so that an appropriate amount of fuel corresponding to the required torque of the engine 1 determined from the accelerator opening degree, vehicle speed, etc. is supplied to the combustion chamber C of each cylinder 2a. On the other hand, in step S12, the fuel injection valve 9 is controlled so that more fuel is injected than the normal injection amount determined according to the required torque. Note that the control for increasing the injection amount in this way may be performed on the fuel injection valve 9 of at least the cylinder 2a in which deposit adhesion was confirmed in the determination of step S3, but it is also possible to increase the injection amounts of the fuel injection valves 9 of all the cylinders 2a.

[0081] Next, the control when it is determined as NO in step S10, that is, when the engine speed is greater than the threshold value Nx, will be described. In this case, the PCM 70 determines whether deposit adhesion continues (step S14). Specifically, the PCM 70 determines whether a state where the compression state index value V is less than the threshold value Vx (V < Vx) has occurred continuously for a further predetermined number of cycles n2 for the cylinder 2a in which deposit adhesion was determined in step S3. After the deposit adhesion determination, the fact that the state of V < Vx has occurred continuously for a further n2 cycles means that compression leakage has occurred continuously for n1 + n2 cycles for the same cylinder 2a, which means that there is a high possibility that the deposit has not been removed yet. Note that the continuous cycle number n2 here is preferably larger than the continuous cycle number n1 used in the determination (determination of the presence or absence of deposit adhesion) in step S3. For example, the continuous cycle number n2 can be set to "5".

[0082] When it is determined as NO in step S14 and it is confirmed that deposit adhesion does not continue, the PCM 70 performs normal shift control on the automatic transmission 101 (step S17). Note that since deposit countermeasures are not required here, the controls corresponding to steps S15 and S16 described later are not executed.

[0083] On the one hand, when it is determined as YES in step S14 and the continuous adhesion of the deposit is confirmed, the PCM 70 changes the shift pattern of the automatic transmission 101 so that a downshift (i.e., increasing the reduction ratio) for reducing the gear stage of the automatic transmission 101 is performed earlier (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 the downshift is performed during deceleration, becomes higher than normal. As a result, the downshift accompanying deceleration is performed at a timing earlier than normal.

[0084] Next, the PCM 70 changes the lock-up release rotation speed so that the lock-up region, which is the range of the engine rotation speed at which the lock-up clutch 115 is engaged, expands to the lower rotation side (step S16). That is, the PCM 70 changes the lock-up release rotation speed, which is the engine rotation speed at which the engagement of the lock-up clutch 115 is released during deceleration, to a value lower than normal. As a result, the lock-up region expands to the lower rotation side, and the lock-up state is maintained up to an engine rotation speed lower than normal.

[0085] 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 the control in steps S15 and S16 corresponds to the "third control" in the present invention. Alternatively, the determination in step S3 corresponds to the "first step" in the present invention, the control in step S7 corresponds to the "second step" in the present invention, the determination in step S10 corresponds to the "third step" in the present invention, and the control in steps S11 and S12 corresponds to the "fourth step" in the present invention.

[0086] [Function and Effect] As described above, in the present embodiment, based on the presence or absence of compression leakage estimated from the compression state index value V, it is determined whether or not a deposit is attached to the valve seat portion. When the attachment of the deposit is confirmed, control (S7) is executed to operate the glow plug 10 and heat the combustion chamber C. 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, control (S11) is executed to reduce the opening degree of the EGR valve 53, and control (S12) is executed to increase the fuel injection amount from the fuel injection valve 9. According to such a configuration, there is an advantage that it is possible to quickly cope with the adhesion of deposits while reducing the influence on emission performance or fuel consumption performance.

[0087] That is, in the present embodiment, since the glow plug 10 is first operated when the deposit adheres, the operated glow plug 10 can quickly heat the combustion chamber C and improve the ignitability of the air-fuel mixture. Thereby, it is possible to suppress a misfire of the air-fuel mixture caused by the adhesion (compression leakage) of the deposit, and it is possible to reduce the possibility that the engine 1 stalls (engine stall) due to the misfire.

[0088] However, depending on the degree of compression leakage, there is a possibility that misfire cannot be avoided even if the glow plug 10 is operated. In particular, when such a situation occurs in a situation where the engine speed is relatively low (in other words, the rotational inertia is low), the possibility of engine stall increases. On the other hand, in the present embodiment, when the engine speed after the operation of the glow plug 10 is equal to or lower than the threshold value Nx, control to reduce the opening degree of the EGR valve 53 and control to increase the fuel injection amount are executed, so that the occurrence of engine stall due to the above circumstances can be suppressed. 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. Further, by increasing the fuel injection amount, the ignitability of the air-fuel mixture can also be improved. And, by the combination of these effects, it is possible to sufficiently reduce the possibility that misfire occurs in a situation where the engine speed is low, and it is possible to effectively suppress the occurrence of engine stall.

[0089] 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. Therefore, it is possible to reduce the possibility of affecting the emission performance and the fuel consumption performance. That is, a reduction in the opening degree of the EGR valve 53 causes an increase in the combustion temperature in the combustion chamber C and an increase in the amount of NOx generated. In addition, an increase in the fuel injection amount causes a decrease in the fuel consumption performance. On the other hand, in the present embodiment, even if the adhesion of deposits (compression leakage) is confirmed, the opening degree of the EGR valve 53 is not reduced until the engine speed becomes equal to or lower than the threshold value Nx. Therefore, it is possible to reduce the possibility of an increase in the amount of NOx generated due to the reduction in the opening degree. Similarly, even if the adhesion of deposits is confirmed, the fuel injection amount is not increased until the engine speed becomes equal to or lower than the threshold value Nx. Therefore, it is possible to reduce the possibility of a decrease in the fuel consumption performance due to the increase in the injection amount. In particular, when the adhesion of deposits is confirmed in a situation where the engine speed exceeds the threshold value Nx and the glow plug 10 operates in response to this, the deposits may be removed by the combustion pressure or the like before the engine speed becomes equal to or lower than the threshold value Nx. In such a case, it is not necessary to change the opening degree of the EGR valve 53 and the fuel injection amount for the purpose of countermeasures against deposits in the first place. Therefore, the influence on the emission performance and the fuel consumption performance can be minimized. Thus, in the present embodiment, it is possible to suppress the occurrence of engine stalls due to deposit adhesion while reducing the influence on the emission performance and the fuel consumption performance of the engine 1.

[0090] Also, in the present embodiment, as the compression state index value V described above, the ratio (T1 / T2) of the first time T1 required for passing through the first crank angle range ΔC1 straddling the compression top dead center and the second time T2 required for passing through the second crank angle range ΔC2 included in the expansion stroke is calculated. Therefore, by comparing the compression state index value V with the threshold value Vx, it is possible to accurately estimate the occurrence of compression leakage and, consequently, the adhesion of deposits to the valve seat portion. 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 through the compression top dead center becomes smaller. This means that the difference between the first time T1 and the second time T2 decreases, in other words, the ratio (T1 / T2) of the first time T1 and the second time T2 becomes smaller. Therefore, according to the present embodiment in which the ratio of the first time T1 and the second time T2 is calculated as the compression state index value V, it is possible to accurately estimate compression leakage (and consequently the adhesion of deposits) based on the magnitude of the compression state index value V.

[0091] Further, in the present embodiment, when it is confirmed that deposits continue to adhere (continuous compression leakage) in a state where the engine speed is higher than the threshold value Nx after the glow plug 10 operates, the shift pattern is changed so that the engine speed (downshift speed) at which downshift for increasing the reduction ratio is performed becomes higher than normal (S15), and the range of the engine speed (lock-up region) at which the lock-up clutch 115 is engaged is expanded to the low rotation side (S16). According to such a configuration, it is possible to maintain a high engine speed during vehicle running and reduce the possibility of engine stall.

[0092] That is, in this embodiment, since the shift pattern is changed so that the shift-down rotation speed increases, for example, when the vehicle decelerates, shift-down is performed at a timing earlier than normal. As a result, the reduction ratio can be increased before the engine rotation speed sufficiently decreases, and the engine rotation speed can be increased by the increased reduction ratio. Also, since the lock-up region is expanded to the low-rotation side, for example, when the vehicle decelerates, the lock-up state (the state where the crankshaft 7 and the wheel W1 are directly connected) is maintained until the engine rotation speed becomes lower than normal. Thereby, the state where the crankshaft 7 rotates in synchronization with the wheel W1 can be maintained, and the decrease in the engine rotation speed can be suppressed by using the rotational energy of the wheel W1. Thus, in this embodiment, since the automatic transmission 101 is controlled so that the engine rotation speed is relatively maintained high, the possibility of engine stall can be further reduced.

[0093] Also, maintaining the engine rotation speed high as described above means that it becomes difficult for a situation to occur where the engine rotation speed decreases to a threshold value Nx or less. As a result, the possibility of the above-described control for changing the opening degree of the EGR valve 53 and the fuel injection amount is reduced, so that the influence on the emission performance and fuel consumption performance of the engine 1 can be further reduced.

[0094] [Modification Example] In the above embodiment, as the compression state index value V representing the compression state of the cylinder 2a, the ratio (T1 / T2) of the first time T1 required for passing through the first crank angle range ΔC1 straddling the compression top dead center and the second time T2 required for passing through the second crank angle range ΔC2 included in the expansion stroke was calculated. However, the compression state index value V may be any value that varies according to the presence or absence of compression leakage, and various modifications are possible within that limit. For example, the difference between the first time T1 and the second time T2 may be adopted as the compression state index value V. Also, the first time T1 may be the time required for passing through a predetermined crank angle range that is on the advanced angle side of ΔC1 in FIG. 6 and included in the compression stroke, and the second time T2 may be the time required for passing through a predetermined crank angle range that is on the advanced angle or retarded angle side of ΔC2 in FIG. 6 and included in 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 for passing through a specific crank angle range, and the speed ratio of the two may be adopted as the compression state index value V.

[0095] In the above embodiment, the compression leakage was detected based on the compression state index value V calculated by the PCM70 from the input information of the crank angle sensor SN1. However, the means for detecting the compression leakage is not limited to this. For example, an in-cylinder pressure sensor for detecting the in-cylinder pressure, which is the internal pressure of the cylinder 2a (combustion chamber C), may be provided, and the compression leakage may be detected based on the detection value of the in-cylinder pressure sensor. In this case, the in-cylinder pressure sensor corresponds to the "compression leakage detection unit" in the present invention.

[0096] In the above embodiment, when the engine speed after the deposit adhesion (compression leakage) is confirmed is equal to or lower than the threshold value Nx, the control (S11) for reducing the opening degree of the EGR valve 53 and the control (S12) for increasing the fuel injection amount from the fuel injection valve 9 are respectively executed. However, it is not necessary to execute both of these two controls, and only one of the controls may be executed. Even in this case, the ignition performance can be improved and the engine stall can be suppressed.

[0097] In the above embodiment, when it is confirmed that deposits continue to adhere (compression leakage still occurs) even when the engine speed is higher than the threshold value Nx, control to change the shift pattern so that the downshift speed is higher than normal (S15) and control to make the lock-up release speed lower than normal (S16) are each executed. However, it is not necessary to execute both of these two controls, and only one of the controls may be executed. Even in this case, engine stall can be suppressed by maintaining a high engine speed.

[0098] In the above embodiment, when deposits adhesion (compression leakage) is confirmed during deceleration fuel cut, the opening degree of the intake shutter valve 33 is changed to a value larger than normal (step S5). However, in addition to or instead of this control, control to change the control pattern of the automatic transmission 101 so that the engine speed is maintained high (the same control as steps S15 and S16 described above) may be executed.

[0099] 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 has been described. However, if it has a heating means corresponding to the glow plug 10, the present invention can also be applied to engines other than diesel engines.

Explanation of Signs

[0100] 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 leakage detection unit) SN1: Crank Angle Sensor (Rotation Detection Unit, Compression Leak Detection Unit) 101: Automatic Transmission 115: Lock-up Clutch

Claims

1. An apparatus for controlling an engine including 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 for opening and closing the intake port and the exhaust port, and an EGR passage connecting the intake passage and the exhaust passage, comprising: A fuel injection valve for injecting fuel into the combustion chamber; A glow plug for heating the combustion chamber; An EGR valve provided in the EGR passage so as to be openable and closable; A rotation detection unit for detecting an engine speed which is the number of revolutions of the output shaft of the engine; A compression leakage detection unit for detecting a compression leakage which is a phenomenon in which air leaks from the combustion chamber through the intake port or the exhaust port during the compression stroke; A controller for controlling the fuel injection valve, the glow plug, and the EGR valve, The controller: When compression leakage is detected by the compression leakage detection unit, executes a first control of operating the glow plug to heat the combustion chamber; 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, executes a second control involving at least one of reducing the opening degree of the EGR valve and increasing the fuel injection amount from the fuel injection valve. An engine control apparatus.

2. In the engine control apparatus according to claim 1, The compression leakage detection unit detects the compression leakage based on a first time required for passing through a first crank angle range included in the compression stroke or straddling the compression top dead center, and a second time required for passing through a second crank angle range included in the expansion stroke immediately following the compression stroke and on the retard side of the first crank angle range. An engine control apparatus.

3. In the engine control apparatus 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 leakage has occurred while the engine speed is higher than the threshold value, the controller executes a third control for controlling the automatic transmission so that the engine speed is maintained high. The controller is a control device for an engine.

4. In the control device for an engine according to claim 3, The automatic transmission includes a lock-up clutch that directly connects the output shaft of the engine and the wheels. The third control includes at least one of a control for expanding the lock-up region, which is a range of engine speeds at which the lock-up clutch is engaged, to the low-speed side, and a control for changing the shift pattern so that the engine speed at which a downshift for increasing the reduction ratio is performed becomes higher. The controller is a control device for an engine.

5. A method for controlling an engine including 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 for opening and closing the intake port and the exhaust port, an EGR passage connecting the intake passage and the exhaust passage, a fuel injection valve for injecting fuel into the combustion chamber, a glow plug for heating the combustion chamber, and an EGR valve provided in the EGR passage so as to be openable and closable, the method 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 the compression stroke; A second step of operating the glow plug to heat the combustion chamber when the compression leakage is detected in the first step; A third step of detecting an engine speed, which is the rotational speed of the output shaft of the engine, after the second step; A method for controlling an engine, comprising: a fourth step of performing 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 lower than a predetermined threshold value.

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