JP7694328B2 - Engine control device and control method - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies. September 28, 2021: Sales begin at dealerships that handle Mazda vehicles in Europe.

The present invention relates to a technology for controlling an engine equipped with an intake valve and an exhaust valve.

Deposits can form (become stuck) between the intake valve and the valve seat, or between the exhaust valve and the valve seat. These deposits can cause a compression leak, where compressed air leaks out of the combustion chamber through the intake or exhaust port. A compression leak can cause the mixture in the combustion chamber to not burn properly (or to misfire).

The engine described in Patent Document 1 below is known as an engine that implements measures against the above-mentioned deposit buildup. In this engine, the presence or absence of deposits is determined during deceleration fuel cut, and if deposit buildup is 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 raising the pressure in the combustion chamber, increasing the possibility that the deposits will be crushed (removed).

Patent No. 6531780

As mentioned above, in Patent Document 1, the determination of deposit formation and countermeasure control are performed only during deceleration fuel cut. In other words, during engine combustion operation, that is, during operation involving the combustion of the mixture in the combustion chamber, no particular countermeasure is taken even if deposit formation occurs. For this reason, there is a concern that countermeasures against deposits will be delayed. In other words, even if deposits form during engine combustion operation, no countermeasure is taken until the operation mode subsequently shifts to deceleration fuel cut, so compression leakage and ignition failure caused by deposits may continue for a while. In particular, if deposits form when the engine is in an idling state or a low rotation state close to this, compression leakage and ignition failure may occur when the rotational inertia of the engine is low, which may cause the engine to stall (stalling).

It has therefore been proposed to take some sort of deposit control measure even while the engine is in combustion operation. However, since some of the measures taken may affect the engine's emissions performance or fuel economy, it is desirable to take appropriate measures that take these effects into account.

The present invention was made in consideration of the above circumstances, and aims to provide an engine control device that can quickly take measures against deposits while reducing the impact on emissions performance or fuel economy.

In order to solve the above problem, an engine control device according to one aspect of the present invention is a device for controlling an engine having 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, and the device includes 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 able to open and close, a rotation detection unit for detecting an engine speed, which is the rotation speed of an output shaft of the engine, and a rotation detection unit for detecting the rotation speed of the engine output shaft during a compression stroke. The engine includes a compression leak detection unit that detects compression leak, which is a phenomenon in which air leaks from a combustion chamber through the intake port or the exhaust port, and a controller that controls the fuel injection valve, the glow plug, and the EGR valve. When a compression leak is detected by the compression leak detection unit, the controller executes a first control that activates the glow plug to heat the combustion chamber, and when it is confirmed that the engine speed detected by the rotation detection unit is equal to or lower than a predetermined threshold after the first control, the controller executes a second control that involves at least one of reducing the opening of the EGR valve and increasing the amount of fuel injected from the fuel injection valve.

When compression leakage is detected, it is highly likely that deposits have formed on the valve seats of the intake valves or exhaust valves. In this invention, in such cases, the glow plug is first activated, and the activated glow plug quickly heats the combustion chamber, improving the ignition of the mixture. This makes it possible to suppress poor ignition of the mixture caused by deposits (compression leakage), and reduces the possibility of the engine stalling due to poor ignition.

However, depending on the degree of compression leakage, there is a risk that poor ignition cannot be avoided even if the glow plug is activated. In particular, if such a situation occurs when the engine speed is relatively low (in other words, when the rotational inertia is low), the possibility of the engine stalling increases. In contrast, in the present invention, when the engine speed after the glow plug is activated is below a predetermined threshold, control is executed to reduce the opening of the EGR valve or to increase the fuel injection amount, so that the occurrence of the stall due to the above-mentioned circumstances can be suppressed. In other words, when the opening of the EGR valve is reduced, the proportion of EGR gas, which is an inert gas, in the combustion chamber decreases, and the ignition of the mixture is improved. In addition, when the fuel injection amount is increased, the ignition of the mixture is also improved. This reduces the possibility of poor ignition occurring when the engine speed is low, and the occurrence of the stall can be effectively suppressed.

Moreover, in the present invention, the above-mentioned control of 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 that the possibility of affecting the emission performance or fuel economy can be reduced. That is, reducing the opening degree of the EGR valve increases the combustion temperature in the combustion chamber, which has the effect of increasing the amount of NOx generated. In addition, increasing the amount of fuel injection has the effect of reducing the fuel economy. In contrast, in the present invention, even if a compression leak is confirmed, these measures are not taken until the engine speed is equal to or lower than the threshold value, so that the possibility of increasing the amount of NOx generated or reducing the fuel economy can be reduced. In particular, in a case where a compression leak is confirmed when the engine speed exceeds the threshold value and the glow plug is activated in response to this, the deposits may be removed by the combustion pressure or the like before the engine speed falls 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 in the first place to deal with the deposits, so that the impact on the emission performance or fuel economy can be minimized. In this way, the present invention can suppress the occurrence of stalls due to deposit adhesion while reducing the impact on the emission performance or fuel economy of the engine.

Preferably, the compression leakage detection unit detects the compression leakage based on a first time required to pass through a first crank angle range that is included in the compression stroke or crosses the compression top dead center, and a second time required to pass through a second crank angle range that is included in the expansion stroke immediately after the compression stroke and is more retarded than the first crank angle range.

According to this configuration, the relationship between the first time and the second time changes depending on the presence or absence of compression leakage, making it possible to accurately detect compression leakage. In other words, when compression leakage occurs, the compression reaction force acting on the piston during the compression stroke decreases, so the amount of change in the movement speed of the piston before and after passing the compression top dead center decreases, causing a change in the relationship between the first time and the second time. According to the above configuration, this can be utilized to accurately detect compression leakage.

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

With this configuration, the automatic transmission can be controlled to keep the engine speed high while the vehicle is running, reducing the possibility of the engine stalling.

The automatic transmission may include a lock-up clutch that directly connects the output shaft of the engine to the wheels. In this case, it is preferable that the third control includes at least one of control to expand a lock-up region, which is the range of engine speeds at which the lock-up clutch is engaged, to the low rotation side, and control to change the shift pattern so that the engine speed at which a downshift that increases the reduction ratio (downshift speed) is performed is increased.

When the shift pattern is changed so that the downshift speed is higher, downshifts occur earlier than normal, for example when the vehicle is decelerating. This allows the reduction ratio to be increased before the engine speed drops sufficiently, and the increased reduction ratio can be used to raise the engine speed. Also, when the lockup region is expanded to the low rotation side, the lockup state (the state in which the engine output shaft is directly connected to the wheels) is maintained up to a lower engine speed than normal, for example when the vehicle is decelerating. This allows the engine output shaft to maintain a state in which it rotates in sync with the wheels, and the rotational energy of the wheels can be used to suppress a drop in engine speed. In either case, the engine speed is maintained relatively high, reducing the possibility of the engine stalling.

A method for controlling an engine according to another aspect of the present invention is a method for controlling an engine having 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 capable of opening and closing, the method comprising the steps of: It includes a first step of detecting compression leakage, which is a phenomenon in which air leaks through a port; a second step of activating the glow plug to heat the combustion chamber if the compression leakage is detected in the first step; a third step of detecting the engine speed, which is the rotation speed of the output shaft of the engine, after the second step; and a fourth step of reducing the opening of the EGR valve and/or increasing the amount of fuel injected from the fuel injection valve if it is confirmed that the engine speed detected in the third step is equal to or lower than a predetermined threshold value.

This control method invention can achieve the same effects as the control device invention described above.

As described above, the engine control device and control method of the present invention enable rapid deposit countermeasures to be implemented while reducing the impact on emissions performance or fuel economy.

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; FIG. 2 is a cross-sectional view showing details of an intake and exhaust valve and its valve mechanism. FIG. 2 is a plan view showing a schematic structure of a power transmission system between an engine and wheels. FIG. 2 is a functional block diagram showing a control system for an engine and an automatic transmission. 5 is a flowchart showing an example of countermeasure control against adhesion of deposits to a valve seat portion. 10A and 10B are diagrams for explaining a method of calculating a compression state index value.

[Overall engine configuration]
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 diagram is a four-stroke 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 portion 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.

The engine body 2 is, for example, a multi-cylinder type having multiple cylinders 2a arranged in a direction perpendicular to the paper surface of FIG. 1 (see also FIG. 3 described later). The engine body 2 includes a cylinder block 3, a cylinder head 4, and multiple pistons 5. The cylinders 2a are formed by the cylinder block 3 and the cylinder head 4. That is, multiple cylindrical spaces corresponding to the multiple 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 spaces from above. The pistons 5 are accommodated in each cylinder 2a so as to be able to slide back and forth. In this embodiment, the side from the cylinder block 3 toward the cylinder head 4 is treated as the top and the opposite is treated as the bottom, but this is for convenience of explanation and is not intended to limit the installation posture of the engine body 2.

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 surface (cylinder liner) of the cylinder 2a, 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 in the vertical direction. Note that, since the engine 1 of this embodiment is a diesel engine, fuel containing diesel is used as the fuel supplied to the combustion chamber C.

A crankshaft 7, which is the output shaft of the engine body 2, is provided at the bottom of the cylinder block 3 (below the pistons 5). The crankshaft 7 is connected to the pistons 5 of each cylinder 2a via connecting rods 8, and rotates around a central axis in response to the reciprocating motion (up and down movement) of the pistons 5.

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. 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, i.e., the engine water temperature. The crank angle sensor SN1 corresponds to the "rotation detection unit" in this 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 is exposed to the combustion chamber C. The tip of this fuel injection valve 9 is formed with multiple nozzle holes (not shown) that serve as fuel outlets. The fuel injected from each nozzle hole is burned by self-ignition in the combustion chamber C, which is heated and pressurized by 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. The tip of the glow plug 10 is equipped with a heating element (not shown) that generates heat when electricity is passed through it. The heating element heats up to a high temperature in a short time when electricity is passed through it, heating the combustion chamber C.

The glow plug 10 operates when the engine 1 is cold and heats the combustion chamber C. Specifically, the glow plug 10 operates when the engine water temperature at start-up, i.e., the temperature detected by the water temperature sensor SN2 when the engine 1 is started, is equal to or lower than a predetermined first temperature. In addition, after the engine 1 has been started, the operation of the glow plug 10 (heating of the combustion chamber C) continues until the engine water temperature reaches a second temperature that is higher than the first temperature.

The cylinder head 4 is formed with an intake port 11 and an exhaust port 12. The intake port 11 is a port that connects the combustion chamber C of each cylinder 2a to the intake passage 30. The exhaust port 12 is a port that connects the combustion chamber C of each cylinder 2a to 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 drives the intake valve 13 of each cylinder 2a to open and close in conjunction with the rotation of the crankshaft 7. The exhaust valve mechanism 16 is a mechanism that drives the exhaust valve 14 of each cylinder 2a to open and close in conjunction with the rotation of the crankshaft 7. The intake valve 13 periodically opens and closes the opening of the intake port 11 on the combustion chamber C side in response to the drive of the intake valve mechanism 15. The exhaust valve 13 periodically opens and closes the opening of the exhaust port 12 on the combustion chamber C side in response to the drive 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 in the downstream portion close to the engine body 2. The surge tank 30b is a tank that provides an expanded space for equalizing the amount of intake air introduced into each cylinder 2a. The intake manifold 30a includes multiple branch pipes that connect the surge tank 30b to the intake port 11 of each cylinder 2a. The portion of the intake passage 30 upstream of the surge tank 30b is formed in a single pipe shape.

An air cleaner 31, an intercooler 32, and an intake shutter valve 33 are provided in the intake passage 30 upstream of the surge tank 30b. The air cleaner 31 is a filter that removes foreign matter from 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 electrically operated butterfly valve that is provided in the intake passage 30 and can be opened and closed to throttle the flow rate of the intake air. The air cleaner 31, the intercooler 32, and the intake shutter valve 33 are arranged in this order from the upstream side furthest 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 located downstream of the air cleaner 31 in the intake passage 30. The intake pressure sensor SN4 is a sensor that detects the pressure of the intake air introduced into the engine body 2, and is located in the surge tank 30b.

The exhaust passage 40 is a tubular member for discharging 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 that communicate with the exhaust ports 12 of each cylinder 2a, and an exhaust collection section where the branch pipes are collected. The portion of the exhaust passage 40 downstream of the exhaust manifold 40a (exhaust collection section) is formed in a single pipe shape.

A catalytic converter 41 is provided downstream of the exhaust manifold 40a in the exhaust passage 40. The catalytic converter 41 incorporates an oxidation catalyst 41a that oxidizes and detoxifies the CO and HC in the exhaust gas, and a diesel particulate filter (DPF) 41b that collects particulate matter contained in the exhaust gas.

The turbocharger 60 is a so-called two-stage turbocharger, and is equipped with a first turbocharger 61 and a second turbocharger 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. The first compressor 61a is arranged in a portion of the intake passage 30 between the air cleaner 31 and the intercooler 32. The first turbine 61b is arranged in a portion of the exhaust passage 40 upstream of the catalytic device 41.

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

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.

The 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 electrically operated bypass valve 63a is provided in the intake bypass passage 63 so as to be capable of opening and closing.

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 electrically operated wastegate valve 64a is provided in the first exhaust bypass passage 64 so as to be able to open and close. An electrically operated regulator valve 65a is provided in the second exhaust bypass passage 65 so as to be able to open and close.

When supercharging is performed by the first supercharger 61, the wastegate valve 64a is closed. This allows exhaust gas discharged from the engine body 2 to be introduced into the first turbine 61b, which is rotated and driven by the exhaust gas. The first compressor 61a rotates in conjunction with the first turbine 61b to compress the intake air downstream. In other words, the first supercharger 61 achieves supercharging by compressing the intake air in the intake passage 30 and sending it to the engine body 2.

When supercharging is performed by the second supercharger 62, the regulator valve 65a and the bypass valve 63a are closed. As a result, exhaust gas discharged from the engine body 2 is introduced into the second turbine 62b, which is rotated and driven by the exhaust gas. The second compressor 62a rotates in conjunction with the second turbine 62b to compress the intake air downstream. In other words, the second supercharger 62 achieves supercharging by compressing the intake air in the intake passage 30 and sending it 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 to 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, i.e., EGR gas, recirculated to the intake passage 30 through the EGR passage 51. The EGR valve 53 is an electric valve provided in the EGR passage 51 to adjust the amount of exhaust gas recirculated, i.e., the EGR amount. The EGR valve 53 is located downstream of the EGR cooler 52 in the EGR passage 51 (closer to the intake passage 30).

[Details of intake and exhaust valves]
2 is a cross-sectional view showing the details of the intake and exhaust valves 13, 14 and their valve operating mechanisms 15, 16 of the engine body 2. 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 vertically long cylindrical member 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 blocking the opening of the intake port 11 on the combustion chamber C side and is formed so as to expand 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 long cylindrical member in the vertical direction, and is supported by the cylinder head 4 so that it can slide in the axial direction (vertical direction). The umbrella portion 14b is a disk-shaped member that can close the opening of the exhaust port 12 on the combustion chamber C side, and is formed so that its diameter expands from the lower end of the stem portion 14a.

Valve seats 11a and 12a 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 combustion chamber C side, and is in close contact with the periphery of the umbrella portion 13b of the intake valve 13 when the intake valve 13 is closed. The valve seat 12a is a ring-shaped member attached to the opening of the exhaust port 12 on the combustion chamber C side, and is in close contact with the periphery of the umbrella portion 14b of the exhaust valve 14 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 connected 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 in which the cylinders 2a are arranged (perpendicular to the plane of the paper in FIG. 2), and a plurality of cam portions 21b provided on the shaft portion 21a at positions corresponding to the intake valves 13 of each cylinder 2a. The swing arm 23 is supported so as to be able to swing below the cam portions 21b of each cylinder 2a. The valve spring 25 is attached to the cylinder head 4 in a state in which it biases the intake valves 13 in a closing direction (upward). The intake valves 13 periodically open when they receive a 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 applied, the intake valve 13 is maintained in a closed state with the head portion 13b in close contact with the valve seat 11a by the upward biasing force of the valve spring 25.

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 connected to the crankshaft 7 via the transmission member. Specifically, the camshaft 22 includes a shaft portion 22a extending in the direction in which the cylinders 2a are arranged (perpendicular to the plane of the paper in FIG. 2), and a plurality of cam portions 22b provided on the shaft portion 22a at positions corresponding to the exhaust valves 14 of each cylinder 2a. The swing arm 24 is supported so as to be able to swing below the cam portion 22b of each cylinder 2a. The valve spring 26 is attached to the cylinder head 4 in a state in which it biases the exhaust valve 14 in a closing direction (upward). The exhaust valve 14 periodically opens when it receives 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 applied, the exhaust valve 14 is maintained in a closed state in which the head portion 14b is in close contact with the valve seat 12a due to the upward biasing force of the valve spring 26.

[Power system]
Fig. 3 is a plan view showing a schematic structure of a power transmission system that transmits the output of the engine 1 to wheels W1 of a vehicle. The vehicle shown here is a front-engine, rear-wheel-drive (FR) vehicle. Therefore, in Fig. 3, the wheels W1 are the rear wheels, and the engine body 2 is disposed in an engine room at the front of the vehicle. Note that Fig. 3 shows an in-line four-cylinder engine body 2 having four cylinders 2a arranged in a row, but 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, a differential gear 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 gear 103. Wheels W1 are attached to the ends of each drive shaft 104 in the vehicle width direction. The output rotation of the engine body 2 is changed in speed by the automatic transmission 101 and then input to the differential gear 103 via the propeller shaft 102. The rotation input to the differential gear 103 is transmitted to each wheel W1 via the left and right drive shafts 104.

The automatic transmission 101 includes a torque converter 110 and a transmission body 120. The torque converter 110 is a fluid clutch that transmits the output rotation of the engine body 2, i.e., the rotation of the crankshaft 7, to the transmission body 120 via an actuating 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 incorporates 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 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 body 120 via the turbine shaft 114.

A lock-up clutch 115 is provided inside the torque converter 110. 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 lock-up clutch 115 is engaged to connect the crankshaft 7 and the turbine runner 112, the crankshaft 7 and the turbine shaft 114 (the input shaft of the transmission body 120) are mechanically connected without the use of 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.

Engaging the lock-up clutch 115 leads to improved power transmission efficiency. However, if the lock-up clutch 115 is engaged when the engine speed or vehicle speed is low, vibrations from the engine 1 are more likely to be transmitted to the vehicle. For this reason, the lock-up clutch 115 is engaged under specified conditions except when the engine speed or vehicle speed is low, and is released (disengaged) when the engine speed or vehicle speed is low.

The transmission body 120 incorporates a multi-stage transmission mechanism 121 capable of achieving multiple gear stages with different reduction ratios. The transmission mechanism 121 includes a gear mechanism 122 in which multiple planetary gear sets are combined, multiple frictional fastening 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) consisting of a solenoid valve or the like that controls the hydraulic pressure supplied to each frictional fastening element to switch its engagement/release. The hydraulic control valve 123 engages/disengages the appropriate frictional fastening elements, thereby achieving a desired gear stage in the transmission mechanism 121 according to the vehicle speed, etc. The output rotation of the torque converter 110, i.e., the rotation of the turbine shaft 114, is changed in speed at a reduction ratio corresponding to the gear stage of the transmission mechanism 121 and then transmitted to the propeller shaft 102 (and thus the wheels W1).

[Control system]
4 is a functional block diagram showing a control system for the engine 1 and the automatic transmission 101. The PCM 70 shown in the 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.

Detection information from various sensors is input to the PCM70. For example, the PCM70 is electrically connected to the crank angle sensor SN1, water temperature sensor SN2, air flow sensor SN3, and intake pressure sensor SN4 described above. Information detected by each of these sensors (i.e., crank angle, engine speed, engine water temperature, intake flow rate, intake pressure, etc.) is sequentially input to the PCM70.

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 the accelerator pedal operated by the driver who drives the vehicle, i.e., the accelerator opening. The vehicle speed sensor SN6 is a sensor that detects the traveling speed of the vehicle, i.e., the vehicle speed. The detection information from these accelerator sensor SN5 and vehicle speed sensor SN6 is also input sequentially to the PCM 70.

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

[Countermeasures against deposit adhesion]
Here, a deposit (foreign matter) may adhere to the valve seat portion of the intake valve 13 or the exhaust valve 14. For example, a deposit adhered to the inner wall of the intake passage 30 may be accidentally peeled off and flow downstream, and may become caught between the umbrella portion 13b of the intake valve 13 and the valve seat 11a. Alternatively, a deposit flowing into the combustion chamber C may become caught between the umbrella portion 14b of the exhaust valve 14 and the valve seat 12a. Such adhesion (biting) of a deposit to the valve seat portion leads to a compression leak, 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 a compression leak occurs, the mixture of fuel and air injected into the combustion chamber C does not burn properly (or misfires), and poor ignition is likely to occur. Therefore, in this embodiment, as a measure against the adhesion of deposits to the valve seat portion, a control as shown in FIG. 5 is executed by the PCM 70. Details of this control will be described below.

Figure 5 is a flow chart showing the details of the control executed by the PCM 70 while the engine 1 is operating and the crankshaft 7 is rotating. When the control starts, the PCM 70 reads the information output from each of 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) 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 to pass through the first crank angle range ΔC1 that spans from the compression stroke to the expansion stroke, and the second time T2 is the time required to pass through the second crank angle range ΔC2 that is included in the expansion stroke immediately after 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. 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 including 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 a predetermined angle range that is away from the first crank angle range ΔC1 to the retard side and is included in the expansion stroke. In addition, 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 movement speed of the piston 5 passing through the second crank angle range ΔC2 is faster than the movement 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 that accelerates the piston 5 acts during the expansion stroke. And, as described above, the fact that the speed at which the second crank angle range ΔC2 passes is faster than the speed at which the first crank angle range ΔC1 passes means that the second time T2, which is the time it takes to pass through the second crank angle range ΔC2, is shorter than the first time T1, which is the time it takes to pass through the first crank angle range ΔC1. Therefore, the compression state index value V, which is calculated as T1/T2 as described above, is usually calculated as a value significantly greater than 1.

However, if compressed air is leaking from the combustion chamber C through the intake port 11 or exhaust port 12 during the compression stroke, that is, if a compression leak is occurring, the compression reaction force acting on the piston 5 during the compression stroke is reduced, and 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 between 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 a compression leak. The PCM 70 estimates the compression state (the presence or absence of a compression leak) of each cylinder 2a by calculating the compression state index value V having such properties for each combustion cycle of each cylinder 2a.

In this manner, 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 leakage detection unit" in the present invention.

After calculating the compression state index value V in step S2, the PCM 70 judges whether or not a deposit is present on 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 judge whether the former is lower than the latter, that is, whether V<Vx is satisfied. Then, when a state where V<Vx is satisfied, that is, a state where the compression state index value V is lower than the threshold value Vx, occurs for a predetermined number of consecutive cycles n1 for the same cylinder 2a, it is judged that a deposit is present on 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. The number of consecutive cycles n1 here may be set to, for example, "2".

The threshold value Vx used in the judgment of step S3 is determined from the average value of the compression state index values V of all cylinders 2a calculated one cycle before. If the compression state index value V of a specific cylinder 2a is small compared to such threshold value Vx, it means that there is a high possibility that compression leakage is occurring in that specific cylinder 2a, that is, there is a high possibility that compressed air is leaking from the combustion chamber C due to deposits on the valve seat portion of that specific cylinder 2a. Therefore, when the above-mentioned state of V<Vx occurs for the same cylinder 2a for n1 consecutive cycles, the PCM 70 judges that deposits have adhered to that cylinder 2a.

If the answer to step S3 is NO, that is, if it is confirmed that there are no deposits on the valve seats of any of the cylinders 2a, the PCM 70 executes normal engine control (step S13). Note that since no countermeasures against deposits are required in this case, the controls corresponding to steps S8, S9, S11, and S12 described below are not executed.

On the other hand, if the result of step S3 is YES and it is confirmed that a deposit is present on the valve seat of any of the cylinders 2a, that is, if it is confirmed that a deposit is present between the intake valve 13 (or exhaust valve 14) and the valve seat 11a (or 12a) of the cylinder 2a, the PCM 70 judges whether the engine 1 is in 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 the rotation of the wheel W1 is used to maintain the rotation of the crankshaft 7. Such deceleration fuel cut is permitted, for example, when the following conditions are met: 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. The PCM 70 determines whether the conditions for permitting deceleration fuel cut are met based on input information from the crank angle sensor SN1, the accelerator sensor SN5, and the vehicle speed sensor SN6, and executes deceleration fuel cut if the conditions are met.

If step S4 returns YES and it is confirmed that deceleration fuel cut is being performed, the PCM 70 changes the opening of the intake shutter valve 33 to a value larger than normal (step S5). That is, during deceleration fuel cut, the opening of the intake shutter valve 33 is usually set to a relatively small value for the purpose of applying engine brakes. In contrast, 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 deceleration fuel cut. This is to increase the cylinder pressure, which is the internal pressure of the cylinder 2a (combustion chamber C), and increase the possibility that deposits attached to the valve seat portion will be crushed.

On the other hand, if the result of step S4 is NO and it is confirmed that deceleration fuel cut is not being performed, that is, if it is confirmed that operation involving combustion of the air-fuel mixture (combustion operation) is being performed, the PCM 70 judges whether the glow plug 10 is not in operation (step S6). That is, the PCM 70 checks the current flow state of the heating element of the glow plug 10, and if current is not flowing, it judges that the glow plug 10 is not in operation.

When the result of the determination in step S6 is YES and it is confirmed that the glow plug 10 is not in operation, 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. This heats the combustion chamber C and improves the ignition of the mixture. The glow plug 10 to be activated in step S7 is at least the glow plug 10 of the cylinder 2a in which the deposition of deposits was confirmed in the determination in step S3. However, depending on the engine, the control configuration may not allow the glow plug 10 of each cylinder 2a to be switched on/off. In such a case, the PCM 70 activates the glow plugs 10 of all cylinders 2a in step S7. The activation of the glow plugs 10 in step S7 is skipped if the determination in step S6 is NO (i.e., if the glow plugs 10 are already in operation).

Next, the PCM 70 prohibits engine 1 from idling (step S8). Idle stop is a control that automatically stops engine 1 when certain idle stop conditions are met, such as when the vehicle speed is zero and the accelerator opening is zero. In step S8, the PCM 70 turns on the idle stop prohibition flag so that engine 1 is not automatically stopped even if the idle stop conditions are met. This is to prevent engine 1 from failing to restart due to deposits.

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. This makes it less likely for the engine to stall even if the engine is switched to idle operation with deposits still attached.

Next, the PCM 70 determines whether 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.

When the result of 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 value smaller than normal (step S11). That is, during combustion operation of the engine 1, the opening of the EGR valve 53 is usually 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 for the purpose of reducing the amount of NOx generated by combustion. In contrast, 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 opening of the EGR valve 53 after the reduction may be set to an appropriate value within a range in which the amount of EGR gas recirculated is reduced more than normal. It is also possible to reduce the opening of the EGR valve 53 to an opening equivalent to a fully closed position 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 combustion operation of the engine 1, the fuel injection valve 9 of each cylinder 2a is controlled so that an appropriate amount of fuel corresponding to the required torque of the engine 1 determined from the accelerator opening, vehicle speed, etc. is supplied to the combustion chamber C of each cylinder 2a. In contrast, 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 this control to increase the injection amount may be performed at least for the fuel injection valve 9 of the cylinder 2a where the adhesion of deposits was confirmed in the judgment of step S3, but it is also possible to increase the injection amount of the fuel injection valve 9 of all cylinders 2a.

Next, the control when the result of 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 the deposits are still present (step S14). Specifically, the PCM 70 determines whether the compression state index value V is less than the threshold value Vx (V<Vx) for the cylinder 2a for which the deposits were determined to be present in step S3 continues for a predetermined number of cycles n2. The fact that the V<Vx state continues for n2 cycles after the deposits are determined to be present means that compression leakage has occurred for n1+n2 cycles for the same cylinder 2a, and it is highly likely that the deposits have not yet been removed. Note that the number of consecutive cycles n2 here is preferably greater than the number of consecutive cycles n1 used in the determination in step S3 (determination of the presence or absence of deposits). For example, the number of consecutive cycles n2 can be set to "5".

If the result of step S14 is NO and it is confirmed that deposits are not continuing, the PCM 70 executes normal shift control for the automatic transmission 101 (step S17). Note that since no measures against deposits are required in this case, the controls corresponding to steps S15 and S16 described below are not executed.

On the other hand, if step S14 returns YES, confirming that deposits are still present, the PCM 70 changes the shift pattern of the automatic transmission 101 so that the automatic transmission 101 downshifts to a lower gear (i.e., increases the reduction ratio) earlier (step S15). In other words, the PCM 70 changes the shift pattern so that the downshift speed, which is the engine speed at which downshifts are made during deceleration, is higher than normal. This causes downshifts associated with deceleration to be made earlier than normal.

Next, the PCM 70 changes the lockup release speed so that the lockup region, which is the range of engine speeds at which the lockup clutch 115 is engaged, expands to the lower speed side (step S16). That is, the PCM 70 changes the lockup release speed, which is the engine speed at which the lockup clutch 115 is released during deceleration, to a value lower than normal. This expands the lockup region to the lower speed side, and the lockup state is maintained up to engine speeds lower than normal.

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

[Action and Effect]
As described above, in this embodiment, it is determined whether or not a deposit has formed on the valve seat portion based on the presence or absence of compression leakage estimated from the compression state index value V, and if the formation of a deposit is confirmed, a control (S7) is executed to operate the glow plug 10 to heat the combustion chamber C. Furthermore, if it is confirmed that the engine speed is equal to or lower than the threshold value Nx after the operation of the glow plug 10, a control (S11) is executed to reduce the opening of the EGR valve 53, and a control (S12) is executed to increase the amount of fuel injected from the fuel injection valve 9. This configuration has the advantage of being able to quickly address the formation of deposits while reducing the impact on emission performance or fuel economy.

That is, in this embodiment, the glow plug 10 is first activated when deposits form, and the activated glow plug 10 quickly heats the combustion chamber C, improving the ignition of the mixture. This makes it possible to suppress poor ignition of the mixture caused by deposits (compression leakage), and reduces the possibility of the engine 1 stalling due to poor ignition.

However, depending on the degree of compression leakage, there is a risk that poor ignition cannot be avoided even if the glow plug 10 is operated. In particular, if such a situation occurs when the engine speed is relatively low (in other words, when the rotational inertia is low), the possibility of the engine stalling increases. In contrast, in this embodiment, when the engine speed after the glow plug 10 is operated is equal to or lower than the threshold value Nx, control is executed to reduce the opening of the EGR valve 53 and control is executed to increase the fuel injection amount, so that the occurrence of the stall due to the above-mentioned circumstances can be suppressed. That is, by reducing the opening of the EGR valve 53, the proportion of EGR gas, which is an inert gas, is reduced in the combustion chamber C, so that the ignition property of the mixture can be improved. In addition, by increasing the fuel injection amount, the ignition property of the mixture can also be improved. And, by combining these effects, the possibility of poor ignition occurring when the engine speed is low can be sufficiently reduced, and the occurrence of the stall can be effectively suppressed.

Moreover, in this embodiment, the above-mentioned control for changing the opening degree of the EGR valve 53 and the fuel injection amount is not executed unless the engine speed is equal to or lower than the threshold value Nx, so that the possibility of affecting the emission performance and fuel efficiency can be reduced. That is, reducing the opening degree of the EGR valve 53 increases the combustion temperature in the combustion chamber C and increases the amount of NOx generated. In addition, increasing the amount of fuel injection reduces the fuel efficiency. In contrast, in this embodiment, even if the deposition of a deposit (compression leakage) is confirmed, the opening degree of the EGR valve 53 is not reduced until the engine speed is equal to or lower than the threshold value Nx, so that the possibility of the amount of NOx generated increasing due to the reduction of the opening degree can be reduced. Similarly, even if the deposition of a deposit is confirmed, the fuel injection amount is not increased until the engine speed is equal to or lower than the threshold value Nx, so that the possibility of the fuel efficiency decreasing due to the increase of the injection amount can be reduced. In particular, when the deposition of a deposit is confirmed when the engine speed exceeds the threshold value Nx and the glow plug 10 is operated in response to this, the deposit 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 of the EGR valve 53 or the amount of fuel injection to deal with deposits in the first place, so the impact on emissions performance and fuel economy can be minimized. In this way, in this embodiment, it is possible to suppress the occurrence of engine stalls due to deposit adhesion while reducing the impact on the emissions performance and fuel economy of the engine 1.

In addition, in this embodiment, the above-mentioned compression state index value V is calculated as the ratio (T1/T2) between the first time T1 required to pass through the first crank angle range ΔC1 that spans the compression top dead center and the second time T2 required to pass through the second crank angle range ΔC2 included in the expansion stroke. By comparing the compression state index value V with the threshold value Vx, the occurrence of compression leakage and, in turn, the adhesion of deposits to the valve seat portion can be accurately estimated. In other words, when compression leakage occurs, the compression reaction force acting on the piston 5 during the compression stroke becomes smaller, so that the amount of change in the movement 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 this embodiment, in which the ratio between the first time T1 and the second time T2 is calculated as the compression state index value V, it is possible to accurately estimate the compression leakage (and thus the formation of deposits) based on the magnitude of the compression state index value V.

In addition, in this embodiment, if it is confirmed that deposits continue to adhere when the engine speed is greater than the threshold value Nx after the glow plug 10 is activated (continuation of compression leakage), the shift pattern is changed so that the engine speed at which a downshift to increase the reduction ratio is performed (downshift speed) is higher than normal (S15), and the range of engine speeds at which the lockup clutch 115 is engaged (lockup region) is expanded to the lower speed side (S16). With this configuration, the engine speed can be maintained high while the vehicle is running, reducing the possibility of the engine stalling.

That is, in this embodiment, the shift pattern is changed so that the downshift speed is higher, so that, for example, when the vehicle is decelerating, the downshift is performed at an earlier timing than usual. This allows the reduction ratio to be increased before the engine speed drops sufficiently, and the engine speed can be increased by the increased reduction ratio. In addition, since the lockup region is expanded to the low rotation side, the lockup state (the state in which the crankshaft 7 and the wheel W1 are directly connected) is maintained up to an engine speed lower than normal, for example, when the vehicle is decelerating. This allows the crankshaft 7 to maintain a state in which it rotates in synchronization with the wheel W1, and the rotational energy of the wheel W1 can be used to suppress a drop in the engine speed. In this way, in this embodiment, the automatic transmission 101 is controlled so that the engine speed is maintained relatively high, so the possibility of the engine stalling can be further reduced.

In addition, maintaining the engine speed high as described above means that the engine speed is less likely to drop below the threshold value Nx. This reduces the likelihood that the above-mentioned control for changing the opening of the EGR valve 53 and the fuel injection amount will be required, further reducing the impact on the emissions performance and fuel economy of the engine 1.

[Modification]
In the above embodiment, the ratio (T1/T2) between the first time T1 required to pass through the first crank angle range ΔC1 across the compression top dead center and the second time T2 required to pass through the second crank angle range ΔC2 included in the expansion stroke is calculated as the compression state index value V representing the compression state of the cylinder 2a, but the compression state index value V may be any value that varies depending on the presence or absence of compression leakage, and various modifications are possible to that extent. For example, the difference between the first time T1 and the second time T2 may be adopted as the compression state index value V. In addition, the first time T1 may be a time required to pass through a predetermined crank angle range that is more advanced than ΔC1 in FIG. 6 and is included in the compression stroke, and the second time T2 may be a time required to pass through a predetermined crank angle range that is more advanced or retarded than ΔC2 in FIG. 6 and is included in the expansion stroke. Furthermore, the average moving speed of the piston 5 may be calculated from the time required for the piston 5 to pass through a specific crank angle range in each of the compression stroke and the expansion stroke, and the speed ratio between the two may be used as the compression state index value V.

In the above embodiment, compression leakage is detected based on the above-mentioned compression state index value V calculated by the PCM70 from the input information of the crank angle sensor SN1, but the means for detecting compression leakage is not limited to this. For example, a cylinder pressure sensor that detects the 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 detection value of the cylinder pressure sensor. In this case, the cylinder pressure sensor corresponds to the "compression leakage detection unit" in the present invention.

In the above embodiment, when the engine speed after deposit adhesion (compression leakage) is confirmed is equal to or lower than the threshold value Nx, control to reduce the opening of the EGR valve 53 (S11) and control to increase the amount of fuel injected from the fuel injection valve 9 (S12) are executed, but it is not necessary to execute both of these two controls, and only one of the controls may be executed. Even in this case, ignition performance can be improved and 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), control is executed to change the shift pattern so that the downshift speed is higher than normal (S15), and control is executed to set the lockup release speed lower than normal (S16). 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 engine speed can be maintained high to suppress stalling.

In the above embodiment, if 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). However, in addition to or instead of this control, control may be executed to change the control pattern of the automatic transmission 101 so that the engine speed is maintained high (similar to control in steps S15 and S16 described above).

In the above embodiment, an example of applying the present invention to a diesel engine that burns fuel containing diesel through self-ignition has been described, but the present invention can also be applied to engines other than diesel engines as long as they have a heating means equivalent to the glow plug 10.

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 section, compression leakage detection section)
101: Automatic transmission 115: Lock-up clutch

Claims (5)

A device for controlling an engine having 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 which open and close the intake port and the exhaust port, and an EGR passage which connects the intake passage and the exhaust passage,
a fuel injection valve that injects 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 capable of opening and closing;
A rotation detection unit that detects an engine speed, which is the rotation speed of an output shaft of the engine;
a compression leakage detection unit that detects a 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 controller for controlling the fuel injection valve, the glow plug, and the EGR valve,
The controller:
When the compression leakage detection unit detects a compression leakage, a first control is executed to activate the glow plug to heat the combustion chamber;
an engine control device that, when it is confirmed that the engine speed detected by the rotation detection unit is equal to or lower than a predetermined threshold after the first control, executes a second control involving at least one of reducing the opening degree of the EGR valve and increasing the amount of fuel injected from the fuel injection valve. 2. The engine control device according to claim 1,
The compression leakage detection unit detects the compression leakage based on a first time required for the engine to pass through a first crank angle range that is included in the compression stroke or that crosses the compression top dead center, and a second time required for the engine to pass through a second crank angle range that is included in the expansion stroke immediately after the compression stroke and is more retarded than the first crank angle range. 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 a reduction ratio,
An engine control device, wherein the controller executes a third control to control the automatic transmission so as to maintain the engine speed high when it is confirmed after the first control that the compression leakage has occurred while the engine speed is greater than the threshold value. 4. The engine control device according to claim 3,
the automatic transmission includes a lock-up clutch that directly connects an output shaft of the engine to the wheels,
The third control includes at least one of control to expand a lock-up region, which is the range of engine speeds at which the lock-up clutch is engaged, to the lower engine speed side, and control to change a shift pattern so that the engine speed at which a downshift to increase the reduction ratio is performed is increased. 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 in an openable and closable manner,
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 activating 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 a rotation speed of an output shaft of the engine, after the second step;
and a fourth step of at least one of reducing an opening degree of the EGR valve and increasing an amount of fuel injected 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.