JP6206653B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device that performs cylinder deactivation control for deactivating combustion in some cylinders of the engine.

One of the controls for reducing fuel consumption of an internal combustion engine having a plurality of cylinders is cylinder deactivation in which some cylinders are deactivated by prohibiting fuel injection to some cylinders when the engine is under low load. There is an engine control device that performs control. In an engine control apparatus that performs such cylinder deactivation control, some cylinders of all cylinders are deactivation cylinders, and other cylinders are combustion cylinders that are supplied with fuel and continue to burn even during cylinder deactivation control. .
In this case, the engine is provided with a deactivated cylinder catalyst for purifying the exhaust gas of the deactivated cylinder and a combustion cylinder catalyst for purifying the exhaust gas of the combustion cylinder, and for the deactivated cylinder on the upstream side and the downstream side of each catalyst, respectively. An upstream / downstream exhaust sensor and an upstream / downstream exhaust sensor for a combustion cylinder (for example, an air-fuel ratio sensor (A / F sensor), an oxygen sensor (O2 sensor), etc.) are arranged. The engine control device controls the fuel injection amount based on the detection results of these exhaust sensors, and purifies the exhaust gas flowing through each catalyst.
As a conventional technique related to an engine control device, Japanese Patent Laid-Open No. 2012-102615 (Patent Document 1) discloses a technique for appropriately performing air-fuel ratio control during reduced-cylinder operation in which operation of some cylinders of the engine is stopped. Has been. In Patent Document 1, a catalyst is individually provided on each downstream side of the normally operating cylinder and the inactive cylinder, and the upstream side and the downstream side of the normally operating cylinder catalyst, and on the upstream side and the downstream side of the inactive cylinder catalyst. A configuration is disclosed in which an air-fuel ratio sensor is provided, and the fuel injection amount is corrected based on detection values of these air-fuel ratio sensors.

JP 2012-102615 A

  However, in Patent Document 1, exhaust sensors are provided on the upstream side and the downstream side for each catalyst. Therefore, as the number of catalysts mounted on the engine increases, the number of exhaust sensors to be installed increases and the cost increases. There is a problem.

  The present invention provides an engine control apparatus capable of preventing deterioration of exhaust gas purification performance while simplifying the configuration of an engine control apparatus that performs control for stopping combustion of some cylinders. For the purpose.

The present invention includes a fuel injection prohibiting unit that prohibits fuel injection into a part of cylinders of the engine, a pause cylinder that stops combustion due to the fuel injection prohibiting by the fuel injection prohibiting unit, and the fuel injection Lean exhaust in which the lean side detection region of the detection region centered on the stoichiometric air-fuel ratio of the exhaust gas is expanded, including a combustion cylinder that continues combustion while the fuel injection is prohibited by the prohibiting means In a vehicle engine control apparatus comprising: a sensor, a deactivated cylinder catalyst that purifies exhaust gas of the deactivated cylinder; and an exhaust gas that is disposed upstream of the deactivated cylinder catalyst and exhausted from the deactivated cylinder Disposed cylinder exhaust sensor for detecting a specific component concentration, a combustion cylinder catalyst for purifying exhaust gas of the combustion cylinder, and an upstream side of the combustion cylinder catalyst, the combustion A combustion cylinder exhaust sensor for detecting a specific component concentration of exhaust gas discharged from the cylinder, and downstream of a portion where the exhaust gas discharged from the idle cylinder catalyst and the combustion cylinder catalyst merges When the lean exhaust sensor is disposed and the idle cylinder is in a state where combustion is suspended due to the prohibition of fuel injection by the fuel injection prohibiting means, the specific component concentration of the exhaust gas is rich or lean based on the detection result of the lean exhaust sensor. It is characterized in that the determination threshold value for determining whether or not is the lean side .

  The present invention can share a lean exhaust sensor arranged downstream of a deactivated cylinder catalyst and a combustion cylinder catalyst to perform feedback control of the fuel injection amount and reduce the number of exhaust sensors to be installed. It is possible to prevent the exhaust gas purification performance from deteriorating.

FIG. 1 is a schematic configuration diagram of an engine control device. Example 1 FIG. 2 is a diagram illustrating a determination threshold value of the lean exhaust sensor. Example 1 FIG. 3 is a control flowchart during cylinder deactivation. Example 1 FIG. 4 shows the cylinder deactivation execution flag (a), the output value (b) of the deactivated cylinder catalyst and the combustion cylinder catalyst arranged on the upstream side of the catalyst, and the output of the conventional exhaust sensor arranged on the downstream side of the junction. Value (c), output value (d) of a lean exhaust sensor (oxygen sensor) arranged downstream from the junction, and output value (e) of a lean exhaust sensor (air-fuel ratio sensor) arranged downstream from the junction ). Example 1 FIG. 5 is a schematic configuration diagram of an engine control device. (Example 2) FIG. 6 is a control flowchart for switching the cylinder when the cylinder is deactivated. (Example 2)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show Embodiment 1 of the present invention. In FIG. 1, an engine 1 mounted on a vehicle has a plurality of first cylinders # 1 to # 4.
The engine 1 includes an air cleaner 2, an intake pipe 3, a throttle body 4, a surge tank 5, and an intake manifold 6 as an intake system. The throttle body 4 has a throttle valve 7. The intake manifold 6 includes a first intake branch pipe 8 to a fourth intake branch pipe 11. The first intake branch pipe 8 to the fourth intake branch pipe 11 supply the intake air taken from the air cleaner 2 to the first cylinder # 1 to the fourth cylinder # 4, respectively.
The engine 1 has a first fuel injection valve 12 to a fourth fuel injection valve 15 that inject fuel for each of the first cylinder # 1 to the fourth cylinder # 4 as a fuel system, and a first intake branch pipe 8 to a fourth intake air. The branch pipe 11 is provided. The engine 1 performs fuel injection by the first fuel injection valve 12 and the fourth fuel injection valve 15 in the first cylinder # 1 and the fourth cylinder # 4 among the plurality of first cylinders # 1 to # 4. The cylinders are set to be deactivated cylinders in which combustion is prohibited and stopped, and the second cylinder # 2 and the third cylinder # 3 are used as combustion cylinders in which fuel injection is continued by the second fuel injection valve 13 and the third fuel injection valve 14 to perform combustion. Yes.
The engine 1 includes an exhaust manifold 16 as an exhaust system. The exhaust manifold 16 includes a first exhaust branch pipe 17 to a fourth exhaust branch pipe 20. Exhaust gases discharged from the first cylinder # 1 to the fourth cylinder # 4 flow through the first exhaust branch pipe 17 to the fourth exhaust branch pipe 20, respectively.
The first exhaust branch pipe 17 and the fourth exhaust branch pipe 20 through which the exhaust gas discharged from the first cylinder # 1 and the fourth cylinder # 4 of the idle cylinder flows joins the downstream side to collect the exhaust cylinder for the idle cylinder. 21 is connected. The second exhaust branch pipe 18 and the third exhaust branch pipe 19 through which the exhaust gas discharged from the second cylinder # 2 and the third cylinder # 3 of the combustion cylinder flows are gathered downstream to collect the exhaust pipe for the combustion cylinder. 22 is connected. The collective exhaust pipe 21 for idle cylinders and the collective exhaust pipe 22 for combustion cylinders join downstream and are connected to the rear exhaust pipe 23. A deactivated cylinder catalyst 24 is disposed in the middle of the deactivated cylinder collective exhaust pipe 21. A combustion cylinder catalyst 25 is disposed in the middle of the combustion cylinder collecting exhaust pipe 22. The downstream side of the rear exhaust pipe 23 is open to the outside air via a muffler 26.
Exhaust gas discharged from the first cylinder # 1 and the fourth cylinder # 4 is collected in the idle cylinder collective exhaust pipe 21 by the first exhaust branch pipe 17 and the fourth exhaust branch pipe 20, and the idle cylinder catalyst 24 is collected. It is purified by the flow to the rear exhaust pipe 23. Further, the exhaust gas discharged from the second cylinder # 2 and the third cylinder # 3 is collected by the second exhaust branch pipe 18 and the third exhaust branch pipe 19 into the combustion cylinder collective exhaust pipe 22 to be used for the combustion cylinder. It is purified by the catalyst 25 and flows to the rear exhaust pipe 23. The exhaust gases of the first cylinder # 1 to the fourth cylinder # 4 collected in the rear exhaust pipe 23 are silenced by the muffler 26 and discharged to the outside.

The first fuel injection valve 12 to the fourth fuel injection valve 15 are connected to a control device 27 of the engine 1. The control device 27 detects the intake air amount sensor 28 for detecting the intake air amount, the crank angle sensor 29 for detecting the crankshaft angle of the engine 1, and the camshaft angle as means for inputting control information. A cam angle sensor 30, a water temperature sensor 31 for detecting the coolant temperature of the engine 1, a deactivated cylinder exhaust sensor 32 for detecting a specific component concentration in the exhaust gas upstream of the deactivated cylinder catalyst 24, and a combustion cylinder catalyst The exhaust sensor 33 for detecting the concentration of a specific component in the exhaust gas upstream of the exhaust gas 25 and the exhaust gas downstream of the portion where the exhaust gas discharged from the deactivated cylinder catalyst 24 and the combustion cylinder catalyst 25 merges. A lean exhaust sensor 34 for detecting a specific component concentration in the gas is connected.
The idle cylinder exhaust sensor 32 and the combustion cylinder exhaust sensor 33 include, for example, an air-fuel ratio sensor (A / F sensor), an oxygen sensor (O2 sensor), and the like. The lean exhaust sensor 34 is capable of expanding the lean side detection region of the air-fuel ratio of the exhaust gas and detecting the air-fuel ratio on the lean side of the normal exhaust sensor.

The control device 27 of the engine 1 considers the information of the other sensors 28 to 31 based on the detection results of the exhaust cylinder sensor 32, the combustion cylinder exhaust sensor 33, and the lean exhaust sensor 34, and the exhaust gas. The intake air amount and the fuel supply amount are adjusted so that the air-fuel ratio of the fuel becomes the stoichiometric air-fuel ratio.
The control device 27 of the engine 1 includes fuel injection prohibiting means 35. The fuel injection prohibiting means 35 prohibits fuel injection into some cylinders of the first fuel injection valve 12 to the fourth fuel injection valve 15 when a cylinder deactivation condition (such as when the engine 1 is under a low load) is established. Thus, the fuel injection amount is controlled.
In the engine 1 of this embodiment, the cylinders that are deactivated by stopping the fuel injection by the fuel injection prohibiting means 35 are the first cylinder # 1 and the fourth cylinder # 4, and the fuel injection prohibiting means 35 prohibits the fuel injection. The combustion cylinders that continue the fuel injection and perform combustion during the execution are the second cylinder # 2 and the third cylinder # 3. As a result, the fuel injection prohibiting means 35 controls the first fuel injection valve 12 and the fourth fuel injection valve 15 so as to prohibit fuel injection into the first cylinder # 1 and the fourth cylinder # 4 when the cylinder deactivation condition is satisfied. Control the fuel injection amount.
The engine 1 is prohibited from injecting fuel into the first cylinder # 1 and the fourth cylinder # 4 of the deactivated cylinder at the time of cylinder deactivation control by the fuel injection prohibiting means 35. The ignition system operation of the spark plug is not different from that during normal combustion control, and the opening / closing operation of these valves and the spark plug operation are continued.
Therefore, during the cylinder deactivation control, the engine 1 flows only air from the first cylinder # 1 and the fourth cylinder # 4 of the deactivated cylinder into the deactivated cylinder collecting exhaust pipe 21, and the second cylinder # 2 and the second cylinder of the combustion cylinder. Exhaust gas flows from the third cylinder # 3 to the collective exhaust pipe 22 for combustion cylinders. The air from the first cylinder # 1 and the fourth cylinder # 4 and the exhaust gas from the second cylinder # 2 and the third cylinder # 3 are merged in the rear exhaust pipe 23 to detect the air-fuel ratio of the exhaust gas. Since leaning is performed beyond the possible range, it becomes difficult to detect the air-fuel ratio with a normal exhaust sensor.

The control device 27 of the engine 1 detects the lean side of the air-fuel ratio of the exhaust gas in the rear exhaust pipe 23 downstream of the portion where the exhaust gas discharged from the deactivated cylinder catalyst 24 and the combustion cylinder catalyst 25 merges. A lean exhaust sensor 34 having an enlarged area is arranged. The lean exhaust sensor 34 expands the lean side detection region, so that even if the air-fuel ratio of the exhaust gas flowing through the rear exhaust pipe 23 during cylinder deactivation exceeds the region detectable by a normal exhaust sensor, The air-fuel ratio can be detected.
The control device 27 of the engine 1 detects the detection result of the lean exhaust sensor 34 when the first cylinder # 1 and the fourth cylinder # 4 of the idle cylinders are in a state where combustion is suspended due to the prohibition of fuel injection by the fuel injection prohibiting means 35. The determination threshold value for determining whether the specific component concentration of the exhaust gas is rich or lean is changed to the lean side.
As shown by the solid line in FIG. 2, the determination threshold value at the time of cylinder deactivation when the first cylinder # 1 and the fourth cylinder # 4 are deactivated is combustion for all of the first cylinder # 1 to the fourth cylinder # 4. It is set to be leaner than the determination threshold (indicated by a broken line) during normal combustion.
When the normal combustion in which all of the first cylinder # 1 to the fourth cylinder # 4 are performing combustion, the control device 27 detects that the value detected by the lean exhaust sensor 34 is richer than the determination threshold value (dashed line) for normal combustion. If so, it is determined to be rich, and if the detected value of the lean exhaust sensor 34 is leaner than the determination threshold value (dashed line) during normal combustion, it is determined to be lean.
Further, the control device 27 determines that the value detected by the lean exhaust sensor 34 is richer than the determination threshold value (solid line) at the time of cylinder deactivation when the cylinders # 1 and # 4 # 4 are deactivated. Is determined to be rich, and if the detected value of the lean exhaust sensor 34 is leaner than the determination threshold value (solid line) at cylinder deactivation, it is determined to be lean.

Next, the operation will be described.
As shown in FIG. 3, when the control program is started (100), the control device 27 of the engine 1 is in a state where all of the first cylinder # 1 to the fourth cylinder # 4 are combusting, and the lean exhaust sensor 34. Is determined to be active (101). The determination that the lean exhaust sensor 34 is in the active state is made when the temperature of the lean exhaust sensor 34 is equal to or higher than the activation temperature.
If this determination (101) is NO, this determination (101) is repeated. When the determination (101) is YES, the determination threshold value (dashed line in FIG. 2) at the time of normal combustion in which all of the first cylinder # 1 to the fourth cylinder # 4 are burning is used as the determination threshold value of the lean exhaust sensor 34. Referring to (102), it is determined whether the detection value of the lean exhaust sensor 34 is rich or lean using a determination threshold value at the time of normal combustion, and a cylinder deactivation condition for deactivating combustion of some cylinders of the engine 1 Is determined (103).
If this determination (103) is NO, this determination (103) is repeated. If this determination (103) is YES, the fuel injection prohibiting means 35 prohibits the fuel injection to the first cylinder # 1 and the fourth cylinder # 4, and the lean exhaust sensor 34 is used as a determination threshold when the cylinder is stopped. With reference to the determination threshold value (104), it is determined whether the detection value of the lean exhaust sensor 34 is rich or lean using the determination threshold value at cylinder deactivation, and it is determined whether the cylinder deactivation condition is satisfied (105). ).
If the determination (105) is YES, the process returns to the determination threshold reference (104). When this determination (105) is NO, the determination threshold value during normal combustion is referred to as the determination threshold value for the lean exhaust sensor 34 (106), and the detection value of the lean exhaust sensor 34 is rich using the determination threshold value during normal combustion. It is determined whether the program is lean or lean, and the program is ended (107).

As shown in FIG. 4, the control device 27 of the engine 1 operates when the cylinder deactivation execution flag is OFF during normal combustion in which all of the first cylinder # 1 to the fourth cylinder # 4 are burning (FIG. 4). (See (a)), the intake air so that the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio based on the detected value of the exhaust sensor 32 for the idle cylinder and the exhaust sensor 33 for the combustion cylinder and the detected value of the lean exhaust sensor 34. Adjust volume and fuel supply.
When the cylinder deactivation condition is satisfied and the cylinder deactivation execution flag is turned ON at t1 in FIG. 4, the control device 27 of the engine 1 performs the exhaust gases of the second cylinder # 2 and the third cylinder # 3 that are performing combustion. Since the air-fuel ratio of the engine is within the detectable region, it is possible to detect the air-fuel ratio based on the output value of the combustion cylinder exhaust sensor 33, and the exhaust gases of the first cylinder # 1 and the fourth cylinder # 4 that have stopped combustion. Since the air-fuel ratio of the engine is far beyond the detectable range by air alone, detection based on the output value of the idle cylinder exhaust sensor 32 becomes impossible (see FIG. 4B).
The air from the first cylinder # 1 and the fourth cylinder # 4 of the deactivated cylinder and the exhaust gas from the second cylinder # 2 and the third cylinder # 3 of the combustion cylinder are combined in the rear exhaust pipe 23 to be exhaust gas. Since the air-fuel ratio of the exhaust gas becomes leaner beyond the detectable region, it is difficult to detect the air-fuel ratio of the exhaust gas flowing through the rear exhaust pipe 23 with the conventional exhaust sensor (see FIG. 4C). .
The control device 27 of the engine 1 detects the lean side of the air-fuel ratio of the exhaust gas in the rear exhaust pipe 23 downstream of the portion where the exhaust gas discharged from the deactivated cylinder catalyst 24 and the combustion cylinder catalyst 25 merges. Since the lean exhaust sensor 34 composed of an oxygen sensor or an air-fuel ratio sensor with an expanded area is arranged, it is possible to detect the air-fuel ratio of the exhaust gas flowing through the rear exhaust pipe 23 when the cylinder is deactivated, and the output of the lean exhaust sensor 34 The air-fuel ratio control can be performed using the values (see (d) and (e) of FIG. 4). Further, when the cylinder is deactivated, the determination threshold value of the lean exhaust sensor 34 is changed to the lean side, so that the air-fuel ratio of the lean exhaust gas can be reliably detected.

As described above, the control device 27 of the engine 1 shares the lean exhaust sensor 34 disposed in the rear exhaust pipe 23 that is exchanged on the downstream side of the deactivated cylinder catalyst 24 and the combustion cylinder catalyst 25 to feedback the fuel injection amount. Control can be performed, and the number of exhaust sensors to be installed can be reduced to simplify the configuration, and deterioration of exhaust gas purification performance can be prevented.
Further, the control device 27 of the engine 1 determines the concentration of the specific component of the exhaust gas during operation of the engine 1 when there are idle cylinders and during operation of the engine 1 when all cylinders are burning. Therefore, the lean exhaust sensor 34 arranged on the downstream side of the deactivated cylinder catalyst 24 and the combustion cylinder catalyst 25 can be shared, and even if the number of combustion cylinders changes due to cylinder deactivation, the lean threshold value of the lean exhaust sensor 34 is changed. Deterioration of exhaust performance can be prevented.

5 and 6 show a second embodiment of the present invention. The control device 27 of the engine 1 according to the second embodiment includes an integrating unit 36 and a time measuring unit 37 shown in FIG. 5 in addition to the fuel injection prohibiting unit 35 shown in FIG. The integrating means 36 calculates the amount of heat input to the second cylinder # 2 and the third cylinder # 3, which are combustion cylinders, or the first cylinder # 1 and the fourth cylinder # 4, which are deactivated cylinders, are deactivated. It is calculated by integrating the time since the transition to the state. The amount of heat input to the combustion cylinder is integrated based on the intake air amount detected by the intake air amount sensor 28. The integration of the time after shifting to the hibernation state is performed using the time measuring means 37 that counts the time.
The control device 27 of the engine 1 has an integrated amount of heat input to the second cylinder # 2 and the third cylinder # 3, which are combustion cylinders, calculated by the integrating means 36 or more than a predetermined integrated amount, or a first cylinder that is a deactivated cylinder. When the accumulated time after the transition of the first cylinder # 1 and the fourth cylinder # 4 to the rest state becomes a predetermined time or longer, the fuel injection prohibiting unit 35 causes the second cylinder # 2 and the third cylinder # that are combustion cylinders. The combustion is stopped by prohibiting the fuel from being exposed to 3 and the fuel is injected into the first cylinder # 1 and the fourth cylinder # 4, which are the idle cylinders, and the combustion is performed.

As shown in FIG. 6, when the control program starts (200), the control device 27 of the engine 1 determines whether a cylinder deactivation condition for suspending combustion of some cylinders of the engine 1 is established based on the traveling state of the vehicle. Judgment is made (201).
If this determination (201) is NO, this determination (201) is repeated. If this determination (201) is YES, the fuel injection prohibiting means 35 prohibits the fuel injection to the first cylinder # 1 and the fourth cylinder # 4, and the integrating means 36 causes the second cylinder, which is a combustion cylinder. Start integration of heat input to # 2 and third cylinder # 3, or start integration of time since first cylinder # 1 and fourth cylinder # 4, which are inactive cylinders, enter the inactive state (202) It is determined whether the calculated integrated amount of input heat is equal to or greater than a predetermined integrated amount, or whether the calculated integrated time is equal to or greater than a predetermined time (203).
If this determination (203) is NO, this determination (203) is repeated. If this determination (203) is YES, the combustion in the second cylinder # 2 and the third cylinder # 3 of the combustion cylinder is stopped and the fuel in the first cylinder # 1 and the fourth cylinder # 4 of the stopped cylinder is started. (204), the combustion state and the resting state of the combustion cylinder and the resting cylinder are switched. Thereafter, the integrated amount of the input heat amount of the second cylinder # 2 and the third cylinder # 3 is reset, or the integrated amount of the elapsed time of the first cylinder # 1 and the fourth cylinder # 4 is reset (205). It is determined whether the cylinder deactivation condition is satisfied from the travel state (206).
If the determination (206) is YES, the process returns to the determination (201), and the integration of the input heat amount into the first cylinder # 1 and the fourth cylinder # 4, which are the combustion cylinders, is started, or Accumulation of the time from when the second cylinder # 2 and third cylinder # 3 are changed to the resting state is started (202), and then the first cylinder # 1 and the fourth cylinder # 4 are set as the combustion cylinders. The above steps (203) to (206) are executed by using the second cylinder # 2 and the third cylinder # 3 as the idle cylinder.
On the other hand, if this determination (206) is NO, the program is ended (207).

  As described above, the control device 27 of the engine 1 determines whether the combustion state of the combustion cylinder and the idle cylinder is based on the integrated amount of the heat input to the combustion cylinder or the integrated time after shifting to the idle state of the idle cylinder. By switching the resting state, it is possible to equalize the states of the thermal degradation and the oxygen storage amount of each of the resting cylinder catalyst 24 and the combustion cylinder catalyst 25, and the resting cylinder catalyst 24 and the combustion cylinder catalyst. The difference in the exhaust gas purification performance of 25 can be eliminated.

  The present invention shares the lean exhaust sensor disposed downstream of the catalyst for the idle cylinder and the catalyst for the combustion cylinder, reduces the number of exhaust sensors to be installed, and simplifies the configuration while deteriorating the exhaust gas purification performance. Therefore, the present invention can be applied not only to a four-wheeled vehicle equipped with an engine that performs cylinder deactivation control but also to a two-wheeled vehicle.

DESCRIPTION OF SYMBOLS 1 Engine 6 Intake manifold 8-11 1st intake branch pipe-4th intake branch pipe 12-15 1st fuel injection valve-4th fuel injection valve 16 Exhaust manifold 17-20 1st exhaust branch pipe-4th exhaust branch pipe 21 Collective exhaust pipe for idle cylinder 22 Collective exhaust pipe for combustion cylinder 23 Rear exhaust pipe 24 Catalyst for idle cylinder 25 Catalyst for combustion cylinder 27 Controller 28 Intake air amount sensor 28 Crank angle sensor 30 Cam angle sensor 31 Water temperature sensor 32 Inactive cylinder Exhaust sensor 33 Combustion cylinder exhaust sensor 34 Lean exhaust sensor 35 Fuel injection prohibiting means 36 Accumulating means 37 Timing means

Claims (2)

Fuel injection prohibiting means for prohibiting fuel injection into some cylinders of the engine;
The engine includes a pause cylinder that stops combustion by prohibiting fuel injection by the fuel injection prohibiting means, and a combustion cylinder that continues combustion while performing fuel injection prohibition by the fuel injection prohibiting means and performs combustion. Prepared,
In a control device for a vehicle engine comprising: a lean exhaust sensor that expands a lean side detection region of a detection region centered on a stoichiometric air fuel ratio of an exhaust gas,
A deactivated cylinder catalyst for purifying exhaust gas of the deactivated cylinder;
A deactivated cylinder exhaust sensor that is disposed upstream of the deactivated cylinder catalyst and detects a specific component concentration of exhaust gas discharged from the deactivated cylinder;
A combustion cylinder catalyst for purifying exhaust gas of the combustion cylinder;
An exhaust sensor for a combustion cylinder that is disposed upstream of the catalyst for the combustion cylinder and detects a specific component concentration of exhaust gas discharged from the combustion cylinder;
The lean exhaust sensor is disposed downstream of a portion where exhaust gas discharged from the idle cylinder catalyst and the combustion cylinder catalyst merges ,
For determining whether the specific component concentration of the exhaust gas is rich or lean based on the detection result of the lean exhaust sensor when the idle cylinder is in a state where combustion is suspended due to the prohibition of fuel injection by the fuel injection prohibiting means. A control apparatus for an engine, wherein the determination threshold value is changed to a lean side . When the accumulated amount of heat input to the combustion cylinder is equal to or greater than a predetermined accumulated amount, or when the accumulated time after the deactivated cylinder shifts to the deactivated state is equal to or greater than a predetermined time, the fuel injection prohibiting means moves the combustion cylinder to the combustion cylinder. 2. The engine control device according to claim 1 , wherein the fuel injection is inhibited to stop the combustion, and the fuel injection to the inactive cylinder is started to perform the combustion.

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