JP2004100486A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device with a cylinder resting mechanism for detecting operational abnormality of the cylinder resting mechanism by using an exhaust gas sensor arranged in an exhaust passage. <P>SOLUTION: This engine control device stops fuel injection to a cylinder being a resting object at cylinder resting time, and closes an intake valve and a vent valve of the cylinder. The exhaust gas sensor arranged in the exhaust passage of an engine outputs a normal output value when the cylinder is normally stopped by the cylinder resting mechanism. While, when abnormality is caused in at least one operation of the intake valve or the vent valve in switching to a resting state and an operation state, abnormality appears in exhaust gas, and the output value of the exhaust gas sensor changes. Thus, abnormality of valve operation in switching of the resting state and the operation state of the engine can be detected on the basis of the output value of the exhaust gas sensor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an engine having a cylinder deactivation mechanism, and more particularly to a method for detecting an abnormality in a deactivation operation of a cylinder and a return operation from a deactivated state.
[0002]
[Prior art]
From the viewpoint of improving fuel efficiency, among engines having a relatively large number of cylinders, there is known an engine having a cylinder deactivation mechanism for deactivating some of the cylinders. The state in which some of the cylinders are stopped is hereinafter also referred to as “reduced cylinder state”. In general, cylinder deactivation is performed in response to a cylinder deactivation instruction from an ECU (Engine Control Unit), in which at least one of an exhaust valve and an intake valve of a specified cylinder is closed and fuel is supplied to the cylinder. This is done by stopping.
[0003]
However, after the cylinder stop instruction is issued, the exhaust valve or the intake valve may not perform the stop operation correctly for some reason. For example, in a variable valve mechanism of a type in which a valve is opened and closed by a hydraulic circuit, there is a mechanism in which a lock pin or the like is inserted by hydraulic pressure into a mechanism for opening and closing the valve to switch the movable state / rest state of the valve. In such a case, there may be a case where the valve cannot be properly set to the stop state immediately after the cylinder stop instruction due to a fluctuation in the hydraulic pressure, a shift in the lock pin insertion timing, or the like. Such switching failure of the valve state may occur not only in the variable valve mechanism using the hydraulic circuit. A similar problem may occur when returning the cylinder, which has been temporarily stopped, to the operating state. That is, the valve may not immediately start operating even though the return instruction is issued.
[0004]
In the reduced-cylinder state, an amount of air corresponding to the number of operating cylinders is supplied to the other cylinders on the assumption that no intake and exhaust are performed in the cylinders at rest because the valves are closed. Therefore, if an abnormality in the stop operation or the return operation occurs, such as when the cylinder to be stopped is operating or the valve to be returned remains in a stopped state, combustion is not performed properly and an emission abnormality may occur. Further, inconveniences such as drivability may be reduced due to misfire or a step in torque, or catalyst may be deteriorated due to an abnormal mixture ratio may occur.
[0005]
From such a viewpoint, there has been proposed a method of providing a pressure sensor in an intake pipe of an engine and detecting an abnormal operation of a cylinder deactivation mechanism according to the detected pressure value in the intake pipe (for example, Patent Document 1).
[0006]
As a document indicating the state of the art, there is Patent Document 2 which discloses a method of confirming return from reduced cylinder operation based on intake pipe pressure.
[0007]
[Patent Document 1]
JP-A-2002-79773.
[0008]
[Patent Document 2]
JP-A-6-146937
[Problems to be solved by the invention]
However, even if a pressure sensor is not provided in the intake pipe, it is desirable that abnormal operation of the cylinder deactivation mechanism can be detected.
[0010]
The present invention has been made in view of the above points, and provides an engine control device with a cylinder deactivation mechanism that can detect an abnormal operation of a cylinder deactivation mechanism using an exhaust gas sensor provided in an exhaust passage. The task is to
[0011]
[Means for Solving the Problems]
In one aspect of the present invention, a control device for an engine having a cylinder deactivation mechanism includes a cylinder deactivation mechanism for stopping fuel injection and closing an intake valve and an exhaust valve when the cylinder is deactivated, and an exhaust gas sensor provided in an exhaust passage. Abnormality detecting means for detecting an abnormality in switching between the operating state and the rest state of the intake valve and the exhaust valve based on the output value of the exhaust gas sensor.
[0012]
When the cylinder is deactivated, the engine control device stops fuel injection to the cylinder to be deactivated and closes the intake valve and the exhaust valve of the cylinder. When the cylinder is normally stopped by the cylinder deactivation mechanism, the exhaust gas sensor provided in the exhaust passage of the engine outputs a normal output value. On the other hand, when an operation of at least one of the intake valve and the exhaust valve has an abnormality in switching between the rest state and the operating state, the abnormality of the exhaust gas appears and the output value of the exhaust gas sensor changes. Therefore, it is possible to detect an abnormality of the valve operation in switching between the rest state and the operation state of the engine based on the output value of the exhaust gas sensor.
[0013]
In one aspect of the above-described engine control device, the output value of the exhaust gas sensor is an A / F value, and the abnormality detection unit determines the A / F value and a predetermined rich-side threshold and lean-side threshold. By comparing the above, the abnormality can be detected. If an abnormality occurs in the valve operation when the cylinder is switched between the resting state and the operating state, the effect appears on the A / F value in the exhaust gas. Therefore, the A / F value output from the exhaust gas sensor is compared with a predetermined threshold value. Thus, the abnormality can be easily detected.
[0014]
According to another aspect of the above-described engine control device, a means for giving a halt instruction to the cylinder halt mechanism, and when the abnormality detection means detects an abnormality immediately after the halt instruction, cancels the halt state of the cylinder. Means, and the abnormality detecting means can further detect the abnormality after the suspension of the cylinder is released. The effects of abnormalities during cylinder deactivation or return on the output of exhaust gas include those that appear immediately after deactivation or return, and those that appear after that. An abnormal state can be determined.
[0015]
In another aspect of the engine control device described above, when the abnormality detection unit detects the abnormality, the engine control unit may include a unit that prohibits the cylinder from stopping for a predetermined period for safety.
[0016]
Another aspect of the above-described engine control device further includes means for giving an instruction to return from the deactivated state to the cylinder deactivation mechanism, wherein the abnormality detection means detects the engine immediately after the return instruction and from the return instruction. Abnormality detection can be performed after a predetermined number of cycles. Even if an abnormality occurs when the cylinder is stopped or returned, the abnormality may be resolved for a while after that. Therefore, by performing follow-up observation for a predetermined period, appropriate measures can be taken.
[0017]
Another aspect of the engine control device described above may include a unit that prohibits the cylinder from returning from the idle state for a predetermined period for safety when the abnormality detection unit detects an abnormality.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0019]
The present invention is characterized in that, in an engine having a cylinder deactivation mechanism, an operation abnormality at the time of deactivation of a part of cylinders and at the time of return from a deactivated state is determined based on an output of an exhaust sensor provided in an exhaust passage.
[0020]
[Engine configuration]
First, an engine provided with a cylinder deactivation mechanism to which the present invention is applied will be described. FIG. 1 shows a schematic configuration of an engine 50 having a cylinder deactivation mechanism. In FIG. 1, elements that are not directly related to the control of the present invention are omitted.
[0021]
As shown, the engine 50 includes a plurality of cylinders. In the example of FIG. 1, the engine 50 has eight cylinders (# 1 to # 8), and the cylinders # 1 and # 7, the cylinders # 2 and # 8, the cylinders # 3 and # 5, and the cylinders # 4 and # 6. Operate in pairs. That is, even in the reduced cylinder state, at least one cylinder of each set operates. The ignition order of the eight cylinders is in the order of cylinder # 1 → # 8 → # 4 → # 3 → # 6 → # 5 → # 7 → # 2. The left four cylinders (# 1, # 3, # 5, # 7) in FIG. 1 are called a first bank, and the right four cylinders (# 2, # 4, # 6, # 8) are called a second bank.
[0022]
Exhaust gas from each cylinder is discharged to the exhaust passage 54 and sent in the direction of arrow 80. An A / F sensor 56 is provided in each exhaust passage 54, and detects an A / F value of the exhaust gas and sends it to the ECU 60. A catalyst 58 for purifying the emission is provided downstream of the A / F sensor 56 in the exhaust passage 54.
[0023]
The ECU 60 controls the overall operation of the engine 50 based on outputs from various sensors (not shown). Further, the ECU 60 supplies the control signal 72 to the variable valve mechanism of each cylinder to control the opening and closing of the intake valve and the exhaust valve of each cylinder. Further, the ECU 60 detects an operation abnormality of the cylinder deactivation mechanism based on the detected A / F value supplied from the A / F sensor 56, and performs an appropriate measure according to the abnormal state, as described later in detail. .
[0024]
The cylinder is stopped by the ECU 60 closing the intake valve and the exhaust valve of the target cylinder and stopping the fuel injection into the intake passage of the cylinder. More specifically, the ECU 60 first controls the variable valve mechanism to close the exhaust valve, then stops fuel injection, and then controls the variable valve mechanism to close the intake valve. Thus, the exhaust gas normally remains in the combustion chamber while the cylinder is stopped. On the other hand, when returning from the cylinder deactivated state, the ECU 60 first opens the exhaust valve, then starts fuel injection, and then opens the intake valve.
[0025]
[Variable valve gear]
Next, a variable valve operating device that controls opening and closing of an intake valve and an exhaust valve of each cylinder will be described. 2 and 3 show a structure of a variable valve apparatus controlled by a hydraulic circuit. FIG. 2 is a perspective view of the variable valve operating device, and FIG. 3 is a side sectional view thereof.
[0026]
As shown in FIG. 3, the variable valve device includes a camshaft 10 provided with a cam 11. Below the cam 11, a rocker arm 21 rotatably supported by a rocker shaft 20 is provided. An arm 22 is formed on the tip side of the rocker arm 21 so as to protrude forward. The tip of the arm 22 is in contact with the upper ends of the pair of engine valves 13, and is pressed to the side where the valves 13 are closed by the urging force of the valve spring. The engine valve 13 is driven to open and close based on the pressing of the arm 22 which is swung with the rotation of the rocker arm 21 about the rocker shaft 20.
[0027]
As shown in FIGS. 2 and 3, a movable cam follower 23 corresponding to the cam 11 is provided on the upper surface of the rocker arm 21. The movable cam follower 23 is slidably disposed in a slide hole 35 (FIG. 3) formed along the up-down direction of the rocker arm 21. The movable cam followers 23 are constantly urged toward the cam 11 by the urging force of a coil spring (not shown). Therefore, the movable cam follower 23 receives the pressing while making sliding contact with the cam 11.
[0028]
A cylinder hole 36 is formed below the rocker arm 21 so as to intersect with the slide hole 35 in which the movable cam follower 23 is fitted. In the cylinder hole 36, a lock pin 31 for selectively fastening / unfastening the rocker arm 21 and the movable cam follower 23 is slidably disposed.
[0029]
Next, a cam switching mechanism configured around the lock pin 31 will be described in detail with reference to FIGS. 4 (a) and 4 (b). 4 (a) and 4 (b) 3 are cross-sectional views showing a side cross-sectional structure in the vicinity of the lock pin 31. FIG. 4 (a) shows a state when the fastening is released, and FIG. Time modes are shown respectively.
[0030]
As described above, the movable cam follower 23 is slidably fitted into the sliding hole 35 penetrating the rocker arm 21 vertically. Further, a cylinder hole 36 intersecting with the sliding hole 35 is formed below the rocker arm 21, and the lock pin 31 is slidably fitted in the cylinder hole 36. The lock pin 31 is constantly urged by the coil spring 33 toward the base end side of the rocker arm 21, that is, in the direction away from the movable cam follower 23.
[0031]
A groove 32 is formed in the lock pin 31 from the center to the tip. The lower end of the movable cam follower 23 can be fitted into the groove 32. Further, the bottom of the groove 32 is notched to allow the movable cam follower 23 to slide vertically. On the other hand, the bottom surface of the central portion (base end) of the groove 32 is left so as to be able to contact the lower end of the movable cam follower 23.
[0032]
The space 34 on the base end side of the rocker arm 21 defined by the lock pin 31 in the cylinder hole 36 is a hydraulic chamber into which hydraulic oil for operating the lock pin 31 is introduced. The hydraulic chamber 34 is connected to an oil passage 49 formed in the rocker arm 21. Further, the oil passage 49 is connected to an oil passage 43 formed in the rocker shaft 20, and the hydraulic pressure in the hydraulic chamber 34 is adjusted by the supply and discharge of the working oil through the oil passages 43 and 49. You. Then, the lock pin 31 moves in the cylinder hole 36 in accordance with the balance between the force based on the oil pressure in the hydraulic chamber 34 and the urging force of the coil spring 33, and the position shown in FIG. It slides back and forth between the positions shown in b).
[0033]
When releasing the connection between the rocker arm 21 and the movable cam follower 23, the hydraulic oil is discharged from the hydraulic chamber 34 to lower the hydraulic pressure in the same chamber 34. As a result, the lock pin 31 moves toward the base end of the rocker arm 21 by the urging force of the coil spring 33, and comes to the position shown in FIG. At this time, since the lower end of the movable cam follower 23 is located at a portion where the bottom surface of the groove 32 of the lock pin 31 is cut out, vertical sliding thereof is allowed.
[0034]
On the other hand, when the rocker arm 21 and the movable cam follower 23 are fastened, hydraulic oil is supplied to the hydraulic chamber 34 to increase the hydraulic pressure in the hydraulic chamber 34. As a result, the lock pin 31 moves toward the distal end of the rocker arm 21 against the urging force of the coil spring 33, and comes to the position shown in FIG. At this time, the lower end of the movable cam follower 23 is located at a portion where the bottom surface of the groove 32 of the lock pin 31 is left. At this time, when the movable cam follower 23 is pushed down, the lower end surface thereof comes into contact with the bottom surface of the groove 32.
[0035]
The pressing of the cam 11 at this time is directly transmitted to the rocker arm 21 through the contact between the movable cam follower 23 and the lock pin 31. That is, the movable cam follower 23 and the rocker arm 21 at this time are connected to each other, and rotate integrally. In this case, the rocker arm 21 is rotated by the cam 11, and the engine valve 13 is also opened and closed by the cam 11.
[0036]
Therefore, the ECU 60 controls the operation and stop of the engine valve 13 by controlling the supply of hydraulic oil to the hydraulic chamber 34 by controlling an electromagnetic valve and the like provided in the hydraulic circuit of the variable valve operating device. Can be.
[0037]
[Relation between abnormalities of pause / return operation and A / F]
Next, the relationship between the abnormal operation of the cylinder deactivation mechanism and the A / F value output from the A / F sensor 56 will be described. FIG. 5 shows the relationship between the abnormal operation state during the cylinder deactivation operation and the influence on the state in the cylinder and the A / F in each state. Since the suspension operation is being performed, the ECU 60 controls the variable valve operating device so that both the exhaust valve and the intake valve are closed. Therefore, the exhaust valve and the intake valve are normal if they are closed and inactive, and abnormal if they are operating. In this case, it is assumed that the fuel injection has been stopped in response to the cylinder deactivation instruction from the ECU 60.
[0038]
Referring to FIG. 5, a state 1-1 is a state in which the exhaust valve is correctly closed, but the intake valve is operating (that is, opening and closing operation). Therefore, the combustion gas to be confined in the combustion chamber of the cylinder to be deactivated (hereinafter, also referred to as “deactivated cylinder”) flows backward to the intake side and flows into the other cylinder, so that a large amount of EGR (Exhausted) is generated in the other cylinder. Gas recirculation occurs, and the A / F enters a rich state.
[0039]
In state 1-2, fresh air is not sucked into the combustion chamber because the intake valve is closed, and exhaust gas is exhausted to the exhaust side because the exhaust valve is open. When the exhaust gas is exhausted, a negative pressure is generated in the combustion chamber. However, since the intake valve is closed, exhaust gas does not reach other cylinders, and the idle cylinder does not suck in fresh air for other cylinders, so there is a particularly bad effect on both idle cylinders and other cylinders Absent.
[0040]
In the case of the state 1-3, since both the intake valve and the exhaust valve are operating, it is the same as the normal operation state, and the exhaust and the intake are repeated. In this case, since the deactivated cylinder to be deactivated inhales fresh air for another cylinder, the intake air amount of the other cylinder decreases, and as a result, the A / F becomes rich. Immediately after the suspension state is released, fresh air in the combustion chamber of the suspension cylinder is discharged to the exhaust side as it is, and thus temporarily enters the lean state.
[0041]
As described above, the operation abnormality determination method at the time of suspension by the A / F may detect the condition in the column of the A / F influence in FIG. That is, the A / F after the cylinder deactivation instruction is monitored, and if it is a rich state, it corresponds to the state 1-1 or the state 1-3. In each case, it can be seen that the intake valve which should be temporarily stopped has been activated. Further, if the A / F temporarily becomes the lean state after the suspension is released, it corresponds to the state 1-3, and it can be seen that both the exhaust valve and the intake valve are erroneously operated.
[0042]
Next, a description will be given of an abnormal operation at the time of return of the cylinder that has been stopped. FIG. 6 shows a relationship between an abnormal operation state during the returning operation of the cylinder that has been stopped and an influence on the state in the cylinder and the A / F in each state. At the time of return, the ECU 60 controls the variable valve operating device so that both the exhaust valve and the intake valve are operated. Therefore, if the exhaust valve and the intake valve operate and open and close, it is normal, and if they stop in the closed state, it is abnormal. In this case, it is assumed that fuel injection and ignition are performed in response to an instruction to return the cylinder from the rest state.
[0043]
In state 2-1, the exhaust valve has begun to operate correctly, but the intake valve is still at rest. Since the intake valve is closed, fresh air corresponding to the cylinder at rest flows to other cylinders, so that the A / F is in a lean state. In addition, fuel accumulation occurs in the intake passage (port) due to the execution of the fuel injection. Therefore, after that, when the intake valve starts operating properly, the A / F is temporarily in a rich state due to the influence of the excess fuel accumulated in the intake passage (port).
[0044]
For state 2-2, the exhaust valve is still at rest and the intake valve is operating properly. Fuel injection and ignition are performed to generate combustion gas in the combustion chamber. However, since the exhaust valve is kept closed, no exhaust is performed and the combustion gas flows back to the intake side. Since the back-flowed combustion gas flows into another cylinder, a large amount of EGR occurs, and the intake air amount of the other cylinder becomes insufficient, and the A / F becomes rich.
[0045]
In the state 2-3, both the exhaust valve and the intake valve are still closed. Therefore, as in the case of the state 2-1, since the intake valve is closed, fresh air corresponding to the deactivated cylinder flows to the other cylinders, and the A / F enters a lean state. In addition, fuel accumulation occurs in the intake passage (port) due to the execution of the fuel injection. Therefore, after that, when the intake valve starts operating properly, the A / F is temporarily in a rich state due to the influence of the excess fuel accumulated in the intake passage (port).
[0046]
As described above, the operation abnormality determination method at the time of return by the A / F may detect the condition in the A / F influence column of FIG. That is, if the A / F is in a rich state immediately after the return instruction of the stopped cylinder, it corresponds to the state 2-2, and it is understood that the exhaust valve which should be started to operate has not been operated. Further, if the A / F is in the lean state immediately after the return instruction, it corresponds to the state 2-1 or 2-3, and it can be understood that the intake valve is still in the stopped state. If the A / F is neither in the rich state nor in the lean state immediately after the return instruction, it can be determined that the A / F is normal.
[0047]
[Operation abnormality judgment processing]
Next, an operation abnormality determination process using the relationship between the various abnormal states and the A / F will be described. First, the suspension operation abnormality determination processing will be described. FIG. 7 shows a flowchart of the pause operation abnormality determination processing. The following processing is basically performed by the ECU 60 comparing the A / F value output from the A / F sensor 56 with a predetermined rich side threshold value TR and a predetermined lean side threshold value TL.
[0048]
In FIG. 7, first, the ECU 60 determines whether a predetermined cylinder deactivation condition is satisfied based on inputs from various sensors and the like (step S1). When the cylinder deactivation condition is satisfied, the ECU 60 controls the above-described variable valve mechanism to stop the operation of the exhaust valve and the intake valve (step S2), stop the fuel injection (step S3), and stop the A / F sensor. An output of 56 is obtained (step S4). Then, the output A / F value of the A / F sensor 56 is compared with the rich threshold TR (step S5). When the output A / F value is smaller than the rich side threshold value TR, the ECU 60 determines that the A / F is in a rich state, and an abnormality in the state 1-1 or the state 1-3 shown in FIG. Is determined to have been made (step S6). Then, the ECU 60 sets to prohibit the cylinder reduction during the current trip because the operation abnormality occurs when the cylinder is to be deactivated (step S7). The term “trip” refers to a period from when the engine is started to when the engine is stopped. Then, the ECU 60 issues a return instruction to cancel the deactivation of the cylinder, controls the variable valve operating device so that the intake valve and the exhaust valve are operated, and starts fuel injection and ignition (step S8).
[0049]
Further, the ECU 60 monitors the output A / F value from the A / F sensor 56 after the cylinder return instruction in step S8, and determines whether the output A / F value is larger than the lean side threshold value TL, that is, whether or not a lean state is established (step S8). S9). If the lean state occurs after the cylinder is deactivated (Step S9; Yes), it corresponds to the state 1-3 shown in FIG. 5, and it is understood that both the intake valve and the exhaust valve are abnormal (Step S10). Then, a setting is made such that the cylinder reduction is prohibited during the current trip (step S7).
[0050]
On the other hand, if it is determined that the output A / F value is smaller than the lean threshold TL, that is, it is determined that the vehicle is not in the lean state (step S9; No), the process ends. In this case, it is understood that the state was the abnormal state shown in State 1-1.
[0051]
If it is determined in step S5 that the output A / F value is larger than the rich-side threshold, that is, it is not in the rich state, the process ends as there is no abnormality or there is no influence even if there is an abnormality. As described above, in the case of the abnormality in the state 1-2 shown in FIG. 5, it is difficult to detect since the A / F has no particularly clear influence, but since there is no particularly bad influence, the reduction of cylinders is prohibited. No treatment is performed, and the reduced cylinder state is continued as in the normal state.
[0052]
To summarize the detection of the abnormal state, first, when it is determined in step S5 that the A / F is in the rich state, the ECU 60 generates an abnormal state of either the state 1-1 or the state 1-3. You can see that it is. In any case, since an abnormality is recognized in the intake valve, the cylinder deactivation is canceled and the cylinder reduction is prohibited. Then, the ECU 60 further determines whether or not the A / F is in a lean state after the return (step S9). If the A / F is in a lean state, it is known that an abnormality in the state 1-3 has occurred. As described above, by detecting the rich state or the lean state using the A / F value after the cylinder deactivation instruction, it is possible to detect the abnormal states of the state 1-1 and the state 1-3.
[0053]
Next, the return operation abnormality determination processing will be described. FIG. 7 shows a flowchart of the return operation abnormality determination processing. The following processing is also executed by the ECU 60 comparing the A / F value output from the A / F sensor 56 with a predetermined rich threshold value TR and a predetermined lean threshold value TL.
[0054]
In FIG. 8, first, the ECU 60 determines whether a predetermined cylinder deactivation condition is satisfied based on inputs from various sensors and the like (step S21). If the cylinder deactivation condition is satisfied, the ECU 60 controls the above-described variable valve mechanism to start the operation of the exhaust valve and the intake valve (step S22), starts fuel injection (step S23), and starts the A / F sensor. 56 are obtained (step S24). Then, the output A / F value of the A / F sensor 56 is compared with the rich threshold TR (step S25). When the output A / F value is smaller than the rich side threshold value TR, the ECU 60 determines that the A / F is in the rich state, and determines that the abnormality of the state 2-2 shown in FIG. 6, that is, the abnormality of the exhaust valve has occurred. (Step S26). Then, the ECU 60 sets to prohibit the return during the current trip because the operation abnormality occurs when the return from the cylinder deactivated state is attempted. Then, the ECU 60 continues the operation of the engine in the reduced cylinder state (step S27).
[0055]
On the other hand, if it is determined in step S25 that the output A / F value is larger than the rich side threshold value TR (step S25; No), the ECU 60 determines whether the output A / F value is larger than the lean side threshold value TL, that is, whether the vehicle is in the lean state. Is determined (step S28). When the vehicle is in the lean state, the ECU 60 determines that an abnormality in the state 2-1 or the state 2-3 has occurred (step S29). Then, the ECU 60 acquires the A / F value again in the next cycle and compares it with the lean side threshold value TL (step S30). As a result, if the A / F is in a rich state, as shown in states 2-1 and 2-3 in FIG. 6, the abnormality of the intake valve has been recovered, that is, the state has been stopped immediately after the return instruction. It is determined that the intake valve that has been operated correctly is now operating (step S31). Then, the ECU 60 sets the prohibition of the reduced cylinder during the current trip (step S32). This is because although the abnormal recovery of the intake valve has been confirmed in step S31, since the abnormality has occurred once, the safety is prohibited and the subsequent cylinder reduction is prohibited.
[0056]
If the A / F is not in the rich state in step S30, which indicates that the intake valve is still not operating properly, the process proceeds to step S27, in which the return is prohibited, and thereafter the number of cylinders is reduced. The operation is continued (step S27). If the determination in step S28 is No, the A / F is neither in the rich state nor in the lean state, so the ECU 60 determines that the intake valve and the exhaust valve have returned to normal.
[0057]
Note that, despite the fact that the abnormality of the state 2-1 or the state 2-3 is detected in step S29, the reason for not immediately setting the prohibition of the return to the step S27 is that the abnormality of the state 2-1 or the state 2-3 is abnormal. Is considered to be lighter in severity than the abnormality in state 2-2. That is, as shown in FIG. 6, the abnormality in the state 2-1 and the state 2-3 does not particularly affect other cylinders, whereas the abnormality in the state 2-2 affects other cylinders. is there. Therefore, when the state 2-2 is detected (Step S25; Yes), the return prohibition is immediately set (Step S27). On the other hand, in the case of the state 2-1 or 2-3, since the influence is somewhat slight, the state of the cylinder is to be resumed if possible, after watching the state for a while until the intake valve starts to operate. . In the case of a variable valve operating device using the above-described hydraulic circuit, the valve may not be actuated / stopped immediately for various reasons such as the number of rotations and the response speed of the hydraulic circuit. However, in some cycles, such an anomaly may disappear. Therefore, the process is monitored for a while until the abnormality is inherited.
[0058]
It should be noted that the treatment after the detection of the operation abnormality in the above example is an example, and the present invention is not limited to this. That is, whether to set the cylinder reduction prohibition or the return prohibition and, if so, how to determine the period (in the above example, the current trip is being performed) are determined in consideration of various other factors. Can be determined. Also, the A / F threshold value may be set to an appropriate value according to the actual seriousness of the trouble caused by the abnormality.
[0059]
【The invention's effect】
According to the present invention, it is possible to detect abnormal operation of the intake valve and the exhaust valve at the time of cylinder deactivation or cylinder return based on the value of A / F.
[Brief description of the drawings]
FIG. 1 shows a schematic configuration of an engine according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a schematic configuration of a variable valve operating device.
FIG. 3 is a diagram showing a side sectional structure of the variable valve apparatus shown in FIG. 2;
FIG. 4 is a side sectional view of a cam switching mechanism of the variable valve operating device shown in FIG. 2;
FIG. 5 is a table showing a relationship between an A / F and an abnormal state of an intake valve and an exhaust valve during a stop.
FIG. 6 is a table showing a relationship between an abnormal state of an intake valve and an exhaust valve and A / F when returning from a rest state.
FIG. 7 is a flowchart of a pause operation abnormality determination process.
FIG. 8 is a flowchart of a return operation abnormality determination process.
[Explanation of symbols]
13 engine valve 21 rocker arm 23 movable cam follower 31 lock pin 50 engine 53 exhaust passage 56 A / F sensor 60 ECU

Claims (6)

In an engine control device having a cylinder deactivation mechanism,
A cylinder deactivation mechanism that stops fuel injection and closes an intake valve and an exhaust valve when the cylinder is deactivated;
An exhaust gas sensor provided in the exhaust passage;
An engine control device comprising: abnormality detection means for detecting an abnormality in switching between an operating state and a resting state of the intake valve and the exhaust valve based on an output value of the exhaust gas sensor. The output value of the exhaust gas sensor is an A / F value, and the abnormality detecting means detects the abnormality by comparing the A / F value with a predetermined rich side threshold and lean side threshold. The engine control device according to claim 1, wherein: Means for giving a stop instruction to the cylinder stop mechanism,
When the abnormality detection unit detects an abnormality immediately after the halt instruction, a unit that cancels the halt state of the cylinder,
The engine control device according to claim 1, wherein the abnormality detection unit further detects the abnormality after the suspension of the cylinder is released. 4. The engine control device according to claim 1, further comprising: a unit that prohibits a stop of the cylinder for a predetermined period when the abnormality detection unit detects the abnormality. 5. The cylinder deactivation mechanism further includes means for giving an instruction to return from a deactivated state, wherein the abnormality detection means detects abnormality immediately after the return instruction and after a predetermined number of cycles of the engine from the return instruction. The engine control device according to claim 1 or 2, wherein: The engine control device according to claim 5, further comprising a unit that prohibits the cylinder from returning from a deactivated state for a predetermined period when the abnormality detection unit detects an abnormality.

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