JP2000337183A - Control device of cylinder rest engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the control device of a cylinder rest engine which can improve a fuel consumption by controlling an air-fuel ratio properly without increasing the fuel amount, at the shifting time from a whole cylinder operation to a partial cylinder operation at a cruise operation time. SOLUTION: This device has an air-fuel ratio detection means 22 for detecting the air-fuel ratio LAF of a mixture gas, a feedback control means 2 for feedback controlling a fuel supply amount TOUT so that the air-fuel ratio LAF is made to a target air-fuel ratio KLAF following to the detection air-fuel ratio LAF and a shifting time control means 2 for discontinuing the feedback control at the shifting time from the whole cylinder operation to the partial cylinder operation at the cruise operation time and also correcting the phase CAIN of a suction cam to such direction that the suction air amount to the cylinder 4 is reduced following to the detection air-fuel ratio LAF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder deactivated engine capable of switching between a full cylinder operation in which all of a plurality of cylinders are operated and a partial cylinder operation in which the operation of some of the cylinders is stopped.
The present invention relates to a control device for a cylinder deactivated engine that can appropriately perform air-fuel ratio control when shifting from full cylinder operation to partial cylinder operation during cruise operation.

[0002]

2. Description of the Related Art A cylinder deactivated engine obtains a required and stable output by performing all-cylinder operation during acceleration, high-speed running, and the like, while the engine speed and vehicle speed are almost constant and within a predetermined range. For example, during cruise operation, the fuel efficiency is improved by switching to partial cylinder operation to increase the filling efficiency of the working cylinder.
-45767. In addition, during the cruise operation described above, in order to improve the exhaust gas characteristics and the fuel efficiency, the feedback control that controls the fuel supply amount so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio in accordance with the output of the oxygen concentration sensor. Control is generally performed.

[0003]

However, in the conventional control system for a cylinder-inactive engine described above, when the operation mode shifts from the full-cylinder operation to the partial-cylinder operation during the cruise operation, immediately after that, the intake air during the full-cylinder operation is operated. Flows into the working cylinder due to the intake inertia, the intake air amount temporarily increases, and the air-fuel ratio becomes lean. In this case, when the feedback control of the air-fuel ratio is being performed, in order to compensate for this lean state and obtain the target air-fuel ratio,
The fuel supply amount is increased and corrected, and excess fuel is supplied, which may lead to deterioration of fuel efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and appropriately controls the air-fuel ratio without increasing the amount of fuel when shifting from full cylinder operation to partial cylinder operation during cruise operation. Accordingly, it is an object of the present invention to provide a cylinder deactivated engine control device capable of improving fuel efficiency.

[0005]

In order to achieve this object, the present invention is capable of switching between a full cylinder operation in which all the plurality of cylinders are operated and a partial cylinder operation in which the operation of some of the cylinders is stopped. And an intake cam 7 for opening and closing the intake valve 5
Is a control device of a cylinder deactivated engine that can change the phase CAIN of the air-fuel ratio supplied to the cylinder 4 with respect to the crankshaft 11, and detects the air-fuel ratio LAF of the air-fuel mixture supplied to the cylinder 4. According to the oxygen concentration sensor 24) and the detected air-fuel ratio LAF detected by the air-fuel ratio detecting means, the air-fuel ratio of the mixture supplied to the cylinder 4 is set to the target air-fuel ratio KLAF. Feedback control means (ECU2, step 3 in FIG. 2) for performing feedback control of the fuel supply amount (fuel injection time TOUT) of the engine, and feedback control by the feedback control means when shifting from full cylinder operation to partial cylinder operation during cruise operation Is stopped, and the phase CAIN of the intake cam 7 is reduced, and the amount of intake air to the cylinder 4 is reduced in accordance with the detected air-fuel ratio LAF. Transitional control means (ECU 2, step 6-8) for correcting the that direction is characterized by comprising a, a.

As described above, immediately after the cylinder deactivated engine shifts from the full cylinder operation to the partial cylinder operation during the cruise operation, the intake air amount temporarily increases due to the intake inertia, and the air-fuel ratio becomes lean. . According to the control device of the present invention, at the time of the transition from the full cylinder operation to the partial cylinder operation, the transition control means stops the feedback control of the fuel supply amount by the feedback control means and sets the intake cam phase to the cylinder. To the direction in which the amount of intake air to the intake decreases. Therefore, immediately after shifting to the partial cylinder operation, the air-fuel ratio can be appropriately controlled without increasing the amount of fuel, thereby improving the fuel efficiency.
Further, since the intake cam phase is corrected in accordance with the detected air-fuel ratio detected by the air-fuel ratio detecting means, the intake air amount can be appropriately reduced according to the actual lean degree of the air-fuel ratio. Can be appropriately converged to the target air-fuel ratio.

In this case, when the detected air-fuel ratio LAF indicates a rich state, the transition end control means (ECU) stops the correction of the intake cam phase CAIN by the transition control means.
It is preferable that the method further includes (2) step 11).

In this configuration, when the lean state of the air-fuel ratio is eliminated by the above-described correction of the intake cam phase, the control means at the end of the transition is controlled by the transition end control means in accordance with the detected air-fuel ratio indicating a rich state. The correction of the intake cam phase by the control means is stopped. Therefore, after the transition state immediately after the transition to the partial cylinder operation ends, the intake cam phase can be controlled to a value suitable for the operation state at that time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control system for a cylinder deactivated engine according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a control device 1 to which the present invention is applied. As shown in FIG. 1, the control device 1 includes an ECU (feedback control means, transition control means, transition end control means) 2.
U2 executes fuel supply control and intake cam phase control as described below, according to the operating state of the cylinder deactivated engine 3.

[0010] Cylinder deactivated engine 3 (hereinafter "engine 3")
Are three cylinders 4 in the left bank shown in the upper part of FIG.
This is a V-type 6-cylinder DOHC engine including (only one is shown) and three cylinders 4 (only one is shown) in the right bank shown below. As will be described later, the engine 3 has a normal full-cylinder operation in which all the six cylinders 4 in the left and right banks are operated, and a three-cylinder 4 in the right bank, according to the operation state.
To the three cylinders 4
The operation is switched to the partial cylinder operation in which the intake valve 5 and the exhaust valve 6 are kept closed.

Each bank includes an intake camshaft 9 integrally having a plurality of intake cams 7 (only one is shown) for opening and closing the intake valve 5 and a plurality of exhaust cams 8 for opening and closing the exhaust valve 6. An exhaust camshaft 10 having only one (only one is shown) is provided. The intake camshaft 9 and the exhaust camshaft 10 are connected to a crankshaft 11 via a timing belt (not shown), and rotate according to the rotation.

A variable cam phase mechanism 12 is provided at one end of each intake camshaft 9. The variable cam phase mechanism 8 is driven by hydraulic pressure, and the phase of the intake camshaft 9 with respect to the crankshaft 11, that is, the phase CAIN of the intake cam 7 (hereinafter, “intake cam phase CAIN”).
) Is continuously advanced or retarded,
The opening / closing timing of the intake valve 5 is advanced or retarded.

The variable cam phase mechanism 12 includes an electromagnetic control valve 1.
3 are connected. The electromagnetic control valve 13 is connected to the ECU 2
, And supplies a hydraulic pressure from a hydraulic pump (not shown) of the lubrication system of the engine 3 to the cam phase variable mechanism 12 in accordance with the duty ratio. As described above, the ECU 2 controls the variable cam phase mechanism 12 via the electromagnetic control valve 13 to advance or retard the intake cam phase CAIN.

A cam phase sensor 20 is provided at an end of each intake camshaft 9 opposite to the cam phase variable mechanism 12. This cam phase sensor 20
For example, it is configured by a magnet rotor and an MRE pickup, detects the intake cam phase CAIN, and outputs a detection signal to the ECU 2. Also, the cam phase sensor 2
0 outputs a TDC signal which is a pulse signal. This T
The DC signal is a signal indicating that the piston of the engine 3 is near the top dead center at the start of the intake stroke in each cylinder, and is a predetermined angle (for example, 120 degrees) of the intake camshaft 9.
One pulse is output every time.

Further, in addition to the configuration common to each bank described above, the right bank has intake and exhaust valves 5,
6 is provided with an intake / exhaust valve pause mechanism. This intake / exhaust valve pause mechanism stops the supply of hydraulic pressure,
By releasing the operative connection between the intake valve 5 and the intake cam 7 and between the exhaust valve 6 and the exhaust cam 8, the cylinder 4 in the right bank is deactivated.
This can be achieved by applying the valve driving device disclosed in Japanese Patent No. 77137. Of course, the structure is not limited to the above as long as the intake and exhaust valves 5 and 6 can be switched between the rest state and the movable state.

An injector 16 and an intake pressure sensor 21 composed of a semiconductor pressure sensor and the like are attached to the intake pipe 14 of the engine 3 downstream of the throttle valve 15. The injector 16 is provided so as to face an intake port (not shown) of each of the cylinders 4. The fuel injection time TOUT (fuel supply amount) is controlled by a drive signal from the ECU 2, so that fuel is supplied into the intake pipe 14. Inject and supply to Further, during the partial cylinder operation, the fuel injection of the injector 16 in the right bank is stopped. The intake pressure sensor 21 detects the absolute pressure PBA in the intake pipe 14,
The detection signal is sent to the ECU 2.

In the middle of an exhaust pipe 17 of the engine 3, a three-way catalyst 1 for purifying HC, CO, NOx and the like in exhaust gas is provided.
8 are arranged. An oxygen concentration sensor 24 (hereinafter, referred to as an “LAF sensor 24”) as an air-fuel ratio detecting means, which is made of zirconia and platinum electrodes, is provided upstream of the three-way catalyst 18 in the exhaust pipe 17. The LAF sensor 24 linearly detects the oxygen concentration in the exhaust gas (the air-fuel ratio LAF of the air-fuel mixture) and outputs the detection signal to the EC.
Send to U2.

Further, a water temperature sensor 22 composed of a thermistor or the like is attached to the main body of the engine 3. The water temperature sensor 22 detects an engine water temperature TW, which is a temperature of cooling water circulating in the cylinder block of the engine 3, and sends a detection signal to the ECU 2. ECU2
Is electrically connected to a vehicle speed sensor 26 for detecting a traveling speed V of a vehicle on which the engine 3 is mounted, and a detection signal thereof is transmitted.

The engine 3 is provided with a crank angle sensor 23. The crank angle sensor 23 is a combination of a magnet rotor and an MRE pickup, and outputs a CRK signal, which is a pulse signal, to the ECU 2 at every predetermined crank angle (for example, 1 °) as the crankshaft 11 rotates. The ECU 2 calculates the C
The engine speed Ne of the engine 3 is determined based on the RK signal.

The ECU 2 includes an I / O interface 2
a, a CPU 2b, a RAM 2c, a ROM 2d, and the like.
The M2c uses a backup power supply to hold the stored data even when the engine 3 is stopped. The detection signals from the various sensors described above are subjected to A / D conversion and shaping by the I / O interface 2a, respectively.
It is input to the CPU 2b.

The CPU 2b determines an operating state of the engine 3 such as a cruise operating state in accordance with a control program or the like stored in the ROM 2d in accordance with the detection signals from the various sensors described above. It is determined whether to operate in the cylinder operation or the partial cylinder operation, and the operation of the engine 3 is controlled according to the result. Further, the CPU 2b determines the fuel injection time TOUT of the injector 16 and the target intake cam phase CAINCM.
DU, and a driving signal TOU based on the result of the calculation.
T and DOUT are connected to the injector 16 and the electromagnetic control valve 13.
To control the fuel supply amount and the intake cam phase.

FIG. 2 shows LAF during cruise operation.
Feedback control of the fuel injection time TOUT according to the detected air-fuel ratio LAF detected by the sensor 24 (hereinafter referred to as “air-fuel ratio LAF”) (hereinafter “LAF feedback control”)
FIG. 9 is a flowchart for determining execution / suspension of the right bank and calculating a target intake cam phase CAINCMD of the right bank.

In this process, first, step 1 (“S1”)
It is illustrated. The same applies to the following), it is determined whether or not the engine 3 is in cruise operation. This determination is performed based on, for example, the intake pipe absolute pressure PBA, the engine speed Ne, and the traveling speed V, and these detected values indicate substantially constant values within respective predetermined ranges for a predetermined time continuously. Is determined to be cruise driving. If it is determined that the vehicle is not cruising, the program ends.

When it is determined in step 1 that cruise operation is in progress, it is determined whether or not the engine 3 is in partial cylinder operation (step 2). This determination is made, for example, by referring to a flag that is set when the execution of the partial cylinder operation is determined. If the answer is NO, that is, if the engine 3 is operating in all cylinders, the LAF feedback control is executed (step 3), and this program ends. Thus, the execution of the LAF feedback control during the all-cylinder operation during the cruise operation is ensured.

On the other hand, when it is determined in step 2 that partial cylinder operation is being performed, it is determined whether or not the current loop is the first loop after shifting to partial cylinder operation (step 4). If the answer is YES, that is, immediately after the shift to the partial cylinder operation, the flag FAP is set to "1" to indicate that (step 5).
The LAF feedback control is stopped (step 6).

Next, the air-fuel ratio LAF detected by the LAF sensor 24 and the target air-fuel ratio KLAF (for example, the stoichiometric air-fuel ratio)
ΔA / F (= LAF−KLAF) from the target intake cam phase CAINCM according to the deviation ΔA / F.
The retardation correction amount △ CAINAF of D is calculated (step 7). This calculation is performed by searching a table (not shown) stored in the ROM 2d. In this table, the retardation correction amount 補正 CAINAF increases as the deviation △ A / F increases, that is, as the lean degree of the air-fuel ratio increases. ,
It is set linearly to be a larger value. Next, the retardation correction amount △ CAINAF obtained in step 7 is subtracted from the previous target intake cam phase CAINCMDn−1, and the current target intake cam phase CAINCMDn (= CA
By setting INCMDn−1−ΔCAINAF (step 8), the intake cam phase CAIN is set to the retard correction amount ΔCA
The phase is retarded by INAF and the program ends.

As described above, when shifting to partial cylinder operation,
The reason why the intake cam phase CAIN is retarded is as follows. That is, at the time of transition to the partial cylinder operation, the amount of intake air to the cylinder 4 in the right bank increases for the above-described reason, and the air-fuel ratio LAF temporarily becomes lean. On the other hand, assuming that the engine speed Ne is constant, when the intake cam phase CAIN is advanced, the closing timing of the intake valve 5 approaches the vicinity of the bottom dead center of the piston of the engine 3 to increase the intake charge efficiency. And the generated torque also increases. Conversely, if the intake cam phase CAIN is retarded, the intake charge efficiency is reduced, so that the state becomes richer at the same fuel injection time TOUT. The retard correction of the intake cam phase CAIN utilizes this characteristic. Further, depending on the operating state, when the intake cam phase CAIN is retarded, the closing timing of the intake valve 5 becomes closer to the vicinity of the bottom dead center of the piston, and conversely, the advance angle decreases the intake charging efficiency. In some cases, a similar effect can be achieved, and in such an operating state, advance correction of the intake cam phase CAIN is performed.

If the answer to step 4 is NO, that is, if the engine 3 is in partial cylinder operation and not immediately after the transition, it is determined whether or not the flag FAP is "1" (step 9). When FAP = 1, it is determined that the current loop is the second or subsequent loop following the transition to the partial cylinder operation, and it is determined whether or not the air-fuel ratio LAF indicates a lean state (step 10). When the air-fuel ratio LAF indicates a lean state, the steps 6 to 8 are performed.
And the LAF feedback control is continuously stopped, and the retardation correction amount △ CAI according to the deviation △ A / F
The retard correction control of the intake cam phase CAIN by the NAF is continuously executed, and the program ends.

On the other hand, if the answer to step 10 is NO, that is, if the air-fuel ratio LAF indicates a rich state, it is determined that the transient state immediately after the transition to the partial cylinder operation has ended, and the flag FAP is reset to "0" ( Step 1
1), the retard control for the intake cam phase CAIN is stopped,
The intake cam phase CAIN for partial cylinder operation is set as the target intake cam phase CAINCMD according to the operating state at that time.
By calculating the AP (CAINCMD = CAINAP) and executing the step 3, the LAF feedback control is restarted, and this program ends.

If the answer to step 9 is NO, that is, if the flag FAP has been reset to "0" and the current loop is in partial cylinder operation and the transitional state immediately after the transition has ended, If it is a loop, the steps 12 and 3 are executed to set the target intake cam phase CAI.
Intake cam phase CAIN for partial cylinder operation as NCMD
The program is terminated by setting the AP and continuing the LAF feedback control. As described above, after the transition state immediately after the transition to the partial cylinder operation is completed, the intake cam phase CAINAP suitable for the partial cylinder operation state at that time is calculated as the target intake cam phase CAINCMD, and the actual intake cam phase is calculated. By executing the control for matching the phase CAIN with the target intake cam phase CAINCMD, the intake cam phase CAIN suitable for each operation state is achieved.

FIG. 3 shows an example of the transition of the execution / stop of the LAF feedback control, the intake cam phase CAIN, the air-fuel ratio LAF, etc. obtained by the above-described control when the operation shifts from the full cylinder operation to the partial cylinder operation during the cruise operation. Is shown. In FIG. 3, since the all-cylinder operation is executed before time t1, the LAF feedback control is executed in steps 2 and 3 in FIG. 2 so that the air-fuel ratio LAF becomes equal to the target air-fuel ratio KLAF.
Is maintained at a value close to. Also, the intake cam phase CAIN
Is the intake cam phase C for all-cylinder operation according to the operating state.
AIN0 is set.

From this state, when the engine 3 shifts from the full cylinder operation to the partial cylinder operation at the time t1, immediately after that, the amount of intake air flowing into the cylinder 4 in the right bank increases due to the intake inertia, and the air-fuel ratio LAF Temporarily becomes lean. On the other hand, at the time of the transition to the partial cylinder operation, the execution of steps 4 to 6 in FIG. 2 stops the LAF feedback control, thereby prohibiting the correction of the fuel injection time TOUT according to the air-fuel ratio LAF, and By executing steps 7 and 8, the intake cam phase CA of the right bank
The retard correction control of IN is started.

By the retard of the intake cam phase CAIN,
As the intake charging efficiency decreases, the amount of intake air to the cylinder decreases, and the air-fuel ratio LAF changes to the rich side by the decrease. The suspension of the LAF feedback control and the retard correction control of the intake cam phase CAIN are performed by the air-fuel ratio LA.
As long as F indicates a lean state (step 10: YES),
It is executed continuously (steps 6 to 8). Air-fuel ratio LAF
Lines A and B between t1 and t2 show the transition of the air-fuel ratio LAF when the retard correction control is performed and when it is not performed, respectively. In a state where TOUT is maintained, the target air-fuel ratio KLAF is controlled while suppressing the air-fuel ratio LAF from shifting toward the lean side.
Can be converged. When the air-fuel ratio LAF changes to a rich state at time t2 (step 10: N
O), at step 12, the retard correction control of the intake cam phase CAIN is stopped, and the target intake cam phase CAINCM
D is set to the intake cam phase CAINAP for the partial cylinder operation according to the operation state, and the LAF feedback control is restarted in step S3. Thereafter, as long as the partial cylinder operation is continued, the target intake cam phase CAI
By setting NCMD as described above, an intake cam phase CAIN suitable for each operating state is achieved.

As described above, according to the present embodiment, when the transition from the full-cylinder operation to the partial-cylinder operation is performed during the cruise operation, the LAF feedback control is stopped, and the right-angle control for the intake cam phase CAIN is performed by the retard correction control. The amount of air taken into the cylinder 4 of the bank is gradually reduced until the air-fuel ratio LAF reaches the target air-fuel ratio KLAF. Therefore, immediately after the transition to the partial cylinder operation, the air-fuel ratio LAF can be appropriately controlled without increasing the amount of fuel, thereby improving fuel efficiency. Further, the retardation correction amount △ CAINAF of the intake cam phase CAIN is calculated by using the air-fuel ratio LA.
Since the larger the difference ΔA / F between F and the target air-fuel ratio KLAF is, the larger the value is set, the intake air amount can be appropriately reduced according to the actual lean degree of the air-fuel ratio LAF, and the air-fuel ratio can be reduced. LAF can be appropriately converged to the target air-fuel ratio KLAF.

Further, when the lean state of the air-fuel ratio LAF is eliminated, the retard correction control of the intake cam phase CAIN is stopped, the target intake cam phase CAINCMD is set to the intake cam phase for the partial cylinder operation, and the LAF is set. Restart feedback control. Therefore, after the transitional state immediately after the transition to the partial cylinder operation ends, the fuel injection time TO is maintained while maintaining the intake cam phase CAIN at the value CAINAP suitable for the current partial cylinder operation state.
UT feedback control can be performed.

In the described embodiment, the intake cam phase CA
The characteristics of the above-described intake charging efficiency with respect to IN, that is,
When the intake cam phase CAIN is advanced, the intake valve 5
When the closing timing of the piston approaches the vicinity of the bottom dead center of the piston of the engine 3, the intake charging efficiency increases, and the generated torque also increases. Conversely, when the intake cam phase CAIN is retarded, the intake charging efficiency decreases. Therefore, at the same fuel injection time TOUT, the retarding correction control of the intake cam phase CAIN is executed by utilizing the characteristic that the state becomes richer. As described above, depending on the operation state, the intake cam phase CA
If IN is retarded, the closing timing of the intake valve 5 becomes close to the vicinity of the bottom dead center of the piston, and conversely, the same effect can be achieved by reducing the intake charging efficiency by advancement. , In such an operating state, the intake cam phase C
AIN advance angle correction control is executed.

[0037]

As described above, the control apparatus of the cylinder deactivated engine of the present invention appropriately controls the air-fuel ratio without increasing the amount of fuel when shifting from full cylinder operation to partial cylinder operation during cruise operation. This has effects such as improvement in fuel efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a control device for a cylinder deactivated engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control process by the control device of FIG. 1;

FIG. 3 is a time chart illustrating an operation example according to the flowchart of FIG. 2;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 control device 2 ECU (feedback control means, transition control means, transition end control means) 3 cylinder deactivated engine 4 cylinder 5 intake valve 7 intake cam 11 crankshaft 12 cam phase variable mechanism 24 oxygen concentration sensor (air-fuel ratio detection means) ) CAIN intake cam phase KLAF target air-fuel ratio LAF detected air-fuel ratio TOUT Fuel injection time (fuel supply amount)

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3G084 AA03 BA09 BA13 BA23 CA05 DA02 DA12 EB16 FA05 FA11 FA20 FA26 FA29 FA33 FA38 3G092 AA05 AA11 AA14 AA15 BA04 BB01 BB10 CA08 CB02 DA01 DA02 DA09 DD03 DG05 EA05 EA04 EA04 EA22 EC03 EC07 FA06 FA24 GA14 GB04 HA05Z HA13X HA13Z HB01X HD05X HD05Z HE01Z HE03Z HE08Z HF21Z

Claims (2)

[Claims] The present invention is capable of switching between an all-cylinder operation in which all of a plurality of cylinders are operated and a partial-cylinder operation in which operation of some of the cylinders is stopped, and the phase of an intake cam for opening and closing an intake valve is shifted with respect to a crankshaft. A control device for a cylinder deactivated engine that can be changed by an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to the cylinder, and an air-fuel ratio detected by the air-fuel ratio detecting means. Feedback control means for feedback-controlling the fuel supply amount to the cylinder so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder becomes the target air-fuel ratio; and when shifting from the full-cylinder operation to the partial-cylinder operation during cruise operation In addition, the feedback control by the feedback control means is stopped, and the phase of the intake cam is changed according to the detected air-fuel ratio. A control device for a cylinder deactivated engine, comprising: a transition control unit that corrects in a decreasing direction. 2. A control device according to claim 1, further comprising a transition end control unit for stopping the correction of said intake cam phase by said transition control unit when said detected air-fuel ratio indicates a rich state. A control device for a cylinder deactivated engine according to claim 1.