Method for diagnosing sticking in cylinder deactivation apparatus

Abstract

The present invention relates to a method for diagnosing sticking in a cylinder deactivation apparatus, the method comprising: an intake valve sticking determining step of determining whether the intake valve is stuck closed or stuck open by detecting the amount of variation of intake pressure in each intake manifold cylinders in an operation-off mode of the cylinder deactivation apparatus and comparing the amount of variation with a predetermined value; and an exhaust valve sticking determining step of determining whether the exhaust valve is stuck closed or stuck open by detecting the state of the air-fuel ratio in exhaust gas if it is determined whether the intake valve is stuck closed or stuck open in the intake valve sticking determining step, thereby sensing the stuck closed or the stuck open state of the intake valve and the exhaust valve so as to diagnose failure of the cylinder deactivation apparatus.

Claims

1. A method for diagnosing sticking in a cylinder deactivation apparatus sensing a stuck closed state or a stuck open state of an intake valve and an exhaust valve due to a failure of a cylinder deactivation apparatus, the method comprising: determining that the intake valve is stuck closed or stuck open by detecting an amount of variation of intake pressure in each intake manifold cylinder in an operation-off mode of the cylinder deactivation apparatus and comparing the amount of variation with a predetermined range of values, the determining that the intake valve is stuck closed or stuck open comprising: based on the detected variation of the intake pressure being larger than the predetermined range of values, determining that the intake valve is stuck closed, and based on the detected variation of the intake pressure being smaller than the predetermined range of values, determining that the intake valve is stuck open; and determining whether the exhaust valve is stuck closed or stuck open by detecting a state of the air-fuel ratio in exhaust gas based on determining that the intake valve is stuck closed or stuck open.

2. The method of claim 1, wherein the cylinder deactivation apparatus is in a vehicle, the method further comprising, while the vehicle is driven, informing a driver of a reduction in drivability due to the failure of the cylinder deactivation apparatus based on the determined stuck open or stuck closed intake valve or exhaust valve.

3. The method of claim 1, wherein the predetermined range of values, which is a comparison object of the amount of variation of the intake pressure, has an upper bound threshold value and a lower bound threshold value, and wherein the method comprises: based on the amount of variation of the intake pressure being larger than the upper bound threshold value, determining the intake valve to be stuck closed, and based on the amount of variation of the intake pressure being smaller than the lower bound threshold value, determining the intake valve to be stuck open.

4. The method of claim 1, wherein the determining whether the exhaust valve is stuck closed or stuck open comprises, based on the air-fuel ratio in the detected exhaust gas being lean, determining that the exhaust valve is stuck open.

5. The method of claim 1, wherein the determining whether the exhaust valve is stuck closed or stuck open comprises, based on the detected air-fuel ratio in the exhaust gas being normal, sensing a misfire of a cylinder; and based on sensing a misfire in a single cylinder, determining that the exhaust valve is stuck closed.

6. The method of claim 5, wherein in the determining whether the exhaust valve is stuck closed, the misfire of the cylinder is sensed based on an angular acceleration of a crank sensor.

7. An apparatus for diagnosing sticking in a cylinder deactivation apparatus in an operation-off mode, comprising: an intake pressure detector configured to measure an intake pressure of an intake manifold; an oxygen sensor configured to measure an air quantity in exhaust gas; and a controller configured to detect the amount of variation of intake pressure in each intake manifold cylinder from the intake pressure detector and compare the detected amount of variation with a predetermined range of values to determine whether the intake valve is stuck closed or stuck open, and to calculate a state of an air-fuel ratio in the exhaust gas from the oxygen sensor to determine whether an exhaust valve is stuck open or stuck closed, wherein the controller senses a misfire of a cylinder depending on a state of air-fuel ratio to determine whether the exhaust valve is stuck closed.

8. The apparatus of claim 7, wherein a driver of a vehicle is informed, while the vehicle is driven, of a reduction in drivability due to the failure of the cylinder deactivation apparatus based on the determined stuck open or stuck closed intake valve or exhaust valve.

Description

DESCRIPTION OF DRAWINGS

(1) The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a schematic system diagram of a multi cylinder engine for describing a method for diagnosing sticking in a cylinder deactivation apparatus according to an exemplary embodiment of the present invention;

(3) FIG. 2 is a flow chart illustrating the method for diagnosing sticking in a cylinder deactivation apparatus according to the exemplary embodiment of the present invention; and

(4) FIG. 3 is a graph illustrating an intake pressure difference for explaining an intake valve sticking determining step illustrated in FIG. 2.

BEST MODE

(5) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(6) Referring to FIG. 1, an apparatus for diagnosing in a cylinder deactivation apparatus according to an exemplary embodiment of the present invention includes an intake pressure detector 30 configured to measure an intake pressure of an intake manifold 10, an oxygen sensor 40 configured to measure an air quantity in exhaust gas, and a controller 50 configured to detect the amount of variation of intake pressure in each cylinder of the intake manifold 10 from the intake pressure detector 30 and compare the detected amount of variation with a predetermined value and calculate a state of an air-fuel ratio in the exhaust gas from the oxygen sensor 40 to determine whether the exhaust valve is stuck open and stuck closed.

(7) FIG. 1 illustrates 4 cylinders that is one bank of an 8 cylinder engine. Each of the cylinders is provided with intake valves 15 and exhaust valves 25, in which each of the intake valves 15 communicates with each other by the intake manifold 10 to suck air for combustion and each of the exhaust valves 25 communicates with each other by the exhaust manifold 20 to discharge the exhaust gas.

(8) The intake manifold 10 is provided with an intake pressure detector 30 for measuring an intake pressure and the exhaust manifold 20 is provided with an oxygen sensor 40 for measuring an oxygen quantity in the exhaust gas to detect a lean condition or an enriched condition of the air-fuel ratio.

(9) The intake pressure detector 30 may measure the intake pressures for each cylinder and a difference between the intake pressures and calculate an average value thereof to detect the whole intake pressure.

(10) When the cylinder deactivation apparatus is in an operation-off mode, the controller 50 detects the amount of variation of the intake pressure in each cylinder of the intake manifold 10 from the intake pressure detector 30 and compares the detected amount of variation with the predetermined value. When the detected amount of variation of the intake pressure is larger than the predetermined value, it is determined that the intake valve is stuck closed and when the detected amount of variation is smaller than the predetermined value, it is determined that the intake valve is stuck open.

(11) If the intake valve is closed, the intake pressure within the intake manifold 10 rises, and therefore if it is confirmed whether the intake pressure rises by measuring the intake pressure of the intake manifold 10, it may be appreciated that the intake valve is in the closed state.

(12) Here, the controller 50 may calculate the overall intake pressure in which the average value of the intake pressures for each cylinder within the intake manifold 10 is summed to compare the calculated intake pressure with the predetermined value. Further, the predetermined value that is an object to be compared may be a specific experiment value and an atmospheric pressure. That is, the control unit 50 may compare the detected amount of variation of the intake pressure in each cylinder of the intake manifold 10 or the whole intake pressure with an atmospheric pressure or a specific threshold value obtained by the experiment.

(13) The controller 50 determines whether the air-fuel ratio is lean or enriched based on the information on the air quantity measured by the oxygen sensor 40.

(14) Air-fuel ratio=air quantity/fuel amount

(15) Theoretical air quantity ratio is a ratio of air quantity:fuel (14.7:1)

(16) =air quantity used in actual combustion/air quantity on theoretical air-fuel ratio.

(17) If =1 is a normal state, when <1, the air quantity used in the actual combustion is smaller than the air quantity on the theoretical air-fuel ratio, and therefore the air-fuel ratio may be in an enriched state and when >1, the air quantity used in the actual combustion is larger than the air quantity on the theoretical air-fuel ratio, and therefore the air-fuel ratio may be in a lean state. Here, is a smaller value than 1, and therefore, when is 1, a value in an allowable range as many as is considered to be a normal state.

(18) Meanwhile, the lambda value is detected by the oxygen sensor 40, in which the oxygen sensor 40 does not measure the amount of fuel but measures a partial pressure of oxygen, and therefore, when normal ignition is not made, the air-fuel ratio of the exhaust gas discharged to the exhaust side is recognized as the lean state.

(19) The control unit 50 determines whether the exhaust valve is stuck open or stuck closed depending on the state of the air-fuel ratio in the exhaust gas from the oxygen sensor 40.

(20) The case in which >1, that is, the case in which the air-fuel ratio is lean means that the air quantity used in the actual combustion is smaller than the air quantity on the theoretical air-fuel ratio. The reason is that the exhaust valve is open and thus non-combustion exhaust gas of the cylinder chamber is introduced into the exhaust manifold 20. Therefore, it may be determined that the exhaust valve is in the stuck open state.

(21) When =1, that is, when the air-fuel ratio is a normal state, the controller 50 uses an angular acceleration of a crank sensor to sense a misfire of a cylinder and when a misfire has occurred in a single cylinder, it is determined that the exhaust valve is in the struck closed state.

(22) Hereinafter, a process of diagnosing stuck open or stuck closed of an intake valve and an exhaust valve will be described in detail with reference to FIGS. 1 to 3.

(23) This is based on the fact that the amount of variation of the intake pressure in each intake manifold cylinder is measured in the operation-off mode of the cylinder deactivation apparatus and the state of the air-fuel ratio in the exhaust gas is determined. Since the engine is in a normal driving mode in the operation off mode, fuel is normally injected even to the stuck cylinder.

(24) Further, a gasoline direct injection (GDI) engine directly injecting fuel into the combustion chamber is premised. In the case of the gasoline direct injection, fuel is directly injected into the combustion chamber, and therefore when the exhaust valve is open even in the state in which the intake valve is closed, the injected fuel is discharged to the exhaust manifold as it is to affect the air-fuel ratio.

(25) First, it is checked that a CDA mode is in an off state or an on state (S10). In the case of the off state, a difference P.sub.i in the intake pressure in each cylinder of the intake manifold is detected to compare with a predetermined value P.sub.max or P.sub.min. When the difference in the intake pressure measured in each 1 segment occurs, it may be predicted that abnormality occurs in the intake valve, which compares with the predetermined value P.sub.max or P.sub.min obtained by the experiment. As illustrated in FIG. 3, the P.sub.max is an upper bound threshold value and the P.sub.min is a lower bound threshold value. In the normal state, the intake valve is open only in an intake stroke of each cylinder. FIG. 3 illustrates that in the case of the multi cylinder, some of the plurality of intake valves are open in the intake stroke and then the intake pressure is vibrated depending on the opening and closing of the intake valve while an operation of closing all the intake valves is repeatedly performed when the intake stroke ends. Therefore, when the difference P.sub.i of the intake pressure in each cylinder is in a range between the upper bound threshold value P.sub.max and the lower bound threshold value P.sub.min, the cylinder deactivation apparatus is in a normal state and when the difference P.sub.i is out of the range therebetween, the cylinder deactivation apparatus may be determined to be failure.

(26) That is, when the difference P.sub.i of the intake pressure in each cylinder is larger than the upper bound threshold value P.sub.max (A of FIG. 3), it is determined that the intake valve is stuck closed (S30). In the step S30, if it is determined that the intake valve is stuck closed, the state of the air-fuel ratio in the exhaust gas is detected (S31 and S32) and if it is determined that the air-fuel ratio is lean, it is determined that the exhaust valve is stuck open (S40).

(27) If the exhaust valve is stuck open, the normal ignition is not made and when the air and fuel that are not normally ignited are discharged to the exhaust side, the air-fuel ratio is in the lean state.

(28) When the air-fuel ratio is normal, the misfire of the cylinder is sensed (S33) and when the misfire has occurred in the single cylinder, it is determined that the exhaust valve is stuck closed (S34).

(29) When the exhaust valve is stuck closed, the non-combusted gas is generated. In this case, the exhaust valve is in a closed state, and therefore is not discharged to the exhaust side. For example, when one valve is stuck closed, a 4 cylinder engine is operated as a 3 cylinder engine. In this case, the air-fuel ratio detected by the oxygen sensor is normal. As a result, it may not be determined whether the exhaust valve is stuck closed based on only the air-fuel ratio, and therefore it is determined whether the exhaust valve is stuck closed by additionally sensing whether a misfire has occurred in a specific cylinder. If the ignition is made when the exhaust valve is closed, since the incomplete combustion, that is, the misfire occurs, it may be determined whether the exhaust valve is stuck closed.

(30) When the difference P.sub.i of the intake pressure in each cylinder is smaller than the upper bound threshold value P.sub.max (B of FIG. 3), the difference P.sub.i again compares with the lower bound threshold value P.sub.min (S50). As a result, when the difference P.sub.i of the intake pressure in each cylinder is smaller than the lower bound threshold value P.sub.min, it is determined that the intake valve is stuck open (S51).

(31) If it is determined that the intake valve is stuck open since the difference P.sub.i of the intake pressure in each cylinder is smaller than the lower bound threshold value P.sub.min, the state of the air-fuel ratio in the exhaust gas is detected (S52 and S53).

(32) As a result, when the air-fuel ratio is lean, it is determined that the exhaust valve is stuck open (S60) and when the air-fuel ratio is normal, similar to the step S33, the misfire of the cylinder is sensed (S54). When the misfire has occurred in the single cylinder, it is determined that the exhaust valve is stuck closed (S55). This is the same reason as the step S34.

(33) Meanwhile, when the CDA mode in an on state, it is confirmed whether the misfire occurs (S15) to detect the stuck state of the intake valve and the exhaust valve. When the CDA mode is in an on state, it is normal that the set intake valve and exhaust valve are closed and the fuel injection stops. However, when both of the intake valve and the exhaust valve are stuck open due to the failure of the CDA apparatus, the misfire occurs. Therefore, it is checked whether the misfire occurs (S15). Here, when the misfire occurs, it is determined that both of the intake valve and the exhaust valve are stuck open (S16).

(34) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, they are for specifically explaining the present invention. Therefore, the exemplary embodiments of the present invention is not limited thereto, but those skilled in the art will appreciate that various modifications and alteration are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

(35) Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.