JP2897447B2 - Failure determination device for cam operation mode switching mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a internal combustion engine having a mechanism for switching the selective valve operating mode depending on the operating conditions Bas
The present invention relates to a failure determination device for a lube operation mode switching mechanism.

[0002]

2. Description of the Related Art A valve operating device for driving an intake / exhaust valve of an internal combustion engine is set so as to obtain an optimal valve timing in accordance with an output characteristic required by the engine.

However, the required valve timing varies depending on the operating conditions of the engine. For example, in a low load region, the valve lift and the valve opening period are both small, whereas in a high load region, a large valve lift and the valve opening period are required. Is done. In an engine having a wide range of operating conditions, such as an internal combustion engine for an automobile, it is difficult to set the valve timing to a target operating region, and in any case, it is not possible to achieve optimum matching under all operating conditions.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 63-167016, a plurality of cams having different cam characteristics (cam profiles) are provided, and the cams are selectively switched according to operating conditions. There has been proposed a variable valve operating device capable of operating at an optimal valve timing.

This is achieved by switching between a low-speed high-output cam having a high torque characteristic in a low rotation range and a high-speed high-output cam having a high torque characteristic in a high rotation range according to operating conditions. To achieve high output from high to high speed range. In addition to this, it is equipped with a low output cam (fuel efficiency cam) which has excellent fuel efficiency characteristics in low and medium rotation, partial load range, and fuel efficiency in partial load range Improvements have also been proposed.

[0006]

However, if an error occurs in the cam switching mechanism in some cylinders and it becomes impossible to switch from a certain cam, the failed cylinder and other normal cylinders will not be switched. However, the amount of air actually sucked (filled) into the cylinder greatly differs. The amount of fuel supplied to each cylinder is calculated based on the amount of intake air measured by an airflow sensor or the like installed upstream of the intake passage, and is determined equally. If there is a difference in the amount, a deviation in the air-fuel ratio naturally occurs between the cylinders.

[0007] The high-power cam has a higher cylinder charging efficiency than the low-power cam. Nevertheless, if the same amount of fuel is supplied, the air-fuel ratio of the cylinder operated by the high-power cam is increased. The air-fuel ratio of a cylinder operated with a low-power cam tends to be richer.

Therefore, if the cam cannot be switched for some reason and only the cylinder is fixed to the specific cam, the air-fuel ratio greatly deviates from the original target value, and combustion in the cylinder becomes impossible. It becomes stable, and the exhaust composition also deteriorates.

[0009] Such a problem is caused only by switching the cam.
Not all valves of a specific cylinder
Operation can be selectively stopped or cylinder operation can be stopped.
It also occurs in such things as stopping. Therefore, the present invention solves such a problem by using a valve actuation
When an abnormality occurs in like switching mechanism, which bar of which cylinder
It is an object of the present invention to be able to immediately determine whether an abnormality has occurred in the lube operation mode .

[0010]

The present invention SUMMARY OF], as shown in FIG. 1, different at least three valve operating mode 1 of each output characteristics is disposed for each cylinder, actuating the valves
A means for calculating a fuel supply amount based on an intake air amount of the engine in an internal combustion engine having a mechanism for switching an aspect according to an operating condition; and a distribution and supply of the calculated fuel amount to each cylinder evenly. Means 4, a means 5 for determining the exhaust air-fuel ratio of each cylinder, and a valve actuation in which the output characteristic is located in the middle.
Means 6 for determining whether or not the difference between the air-fuel ratio of each cylinder with respect to the average air-fuel ratio of all cylinders exceeds a reference value in the operating range using the aspect; and Switching is not possible due to the magnitude of the gradient of the fuel ratio difference.
Means 7 for determining a valve operation mode .

Further, in the above invention, when a valve operating mode in which switching is disabled is specified, only means for correcting the fuel supply amount corresponding to the valve operating mode for that cylinder is provided.

[0012]

If an abnormality occurs in the valve operation mode switching mechanism of a certain cylinder and switching cannot be performed while being fixed to a specific valve operation mode , the intake charging efficiency differs between that cylinder and another cylinder. The air-fuel ratio of the cylinder greatly differs from the average air-fuel ratio of the 仝 cylinder.

[0013] intake according to the valve operation mode charging efficiency also varies with the amount of intake air (rpm), an intermediate output characteristics
The valve operation mode with higher intake air charging efficiency or the valve operation mode with lower
The change rate of the air-fuel ratio in the lube operation mode , that is, the gradient of the difference in the air-fuel ratio when the intake air amount changes, is different from each other, and the valve operation mode cannot be switched from this gradient. Can be determined.

Further, for a failed cylinder in which an abnormality has occurred,
When the valve operation mode that cannot be switched is specified,
By correcting the fuel supply amount in accordance with the valve operation mode , fluctuations in the air-fuel ratio can be prevented and combustion can be stabilized.
For this reason, even before repairing the malfunction,
It is possible to prevent misfiring and combustion instability in the cylinder.

[0015]

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

First, FIGS. 2 and 3 show the basic structure of a variable valve mechanism.
No.-117261, two high-output cams that emphasize power in the low-speed range and high-speed range respectively, and low-power (fuel efficiency) that emphasizes fuel efficiency in the partial load range and the like. The three cams including the cams are switched according to the driving situation.

A first cam (low-output cam) 21 is set to a fuel profile that emphasizes fuel economy, has a small cam lift, and has a small lift section in which the lift start is slow and the lift end is short, and 22 is a high torque in a low rotation range. A second cam (a low-speed high-output cam, which corresponds to an intermediate cam in this embodiment) which is set to a cam profile to be generated and has a cam lift relatively larger than the first cam 21, and 23 is a high-rotation region Set to the cam profile that generates high torque, the second
A third cam (a high-speed high-output cam) having a cam lift and a lift section larger than the cam 22, which are provided in parallel on the same cam shaft.

24 is an intake / exhaust valve (intake valve or exhaust valve),
Reference numeral 25 denotes a main rocker arm which is constantly in contact with the first cam 21 via a roller 26, and swings around a rocker shaft 27 to open and close the intake / exhaust valve 24.

The main rocker arm 25 has a shaft 3
Two sub rocker arms 2 that swing about 0
8 and 29 are supported in parallel with the roller 26, and one sub rocker arm 28 contacts the second cam 22 and the other sub rocker arm 29 contacts the third cam 23.

When the sub rocker arms 28 and 29 are not engaged with the main rocker arm 25, they are urged by the lost motion spring 31 so as to always contact the second and third cams 22 and 23. It moves (oscillates) independently of the arm 25.

In order to selectively engage the sub rocker arms 28 and 29 with the main rocker arm 25, first, a cylindrical pin 32 is mounted on the swinging portion of one of the sub rocker arms 28, and the main rocker arm 24 is rotated. Also, a pin 34 is disposed coaxially with the pin 32 so as to be freely slidable in the direction of the camshaft, and these pins 32 and 34 are normally urged by a return spring 36 to be held in the state shown in FIG. , Is disengaged from the main rocker arm 25, but the passage 4 is inserted into the hydraulic chamber 38 in which the pin 34 is accommodated.
When the pressure oil is guided through 0, the pins 32 and 34 are pushed out by a predetermined amount, and the sub rocker arm 28 engages with the main rocker arm 25.

The sub rocker arm 28 is integrated with the main rocker arm 25 when it is in the base circle of the first cam 21 and the second cam 22. After the integration, the second rocker has a larger lift than the first cam 21. The timing is switched to the valve timing according to the cam 22. In other words, the characteristic of the first cam 21 focusing on fuel consumption is switched to the characteristic of the second cam 22 focusing on output in a low rotation range.

The other sub rocker arm 29 has the same configuration. When pressure oil is guided to the hydraulic chamber 39 through the passage 41, the pins 35 and 33 are pushed out against the return spring 37, Sub rocker arm 2
9 engages with the main rocker arm 25,
The valve timing is switched so as to depend on the third cam 23 having both a larger lift amount and a larger lift section than the first cam 21 in the same manner as described above, so that output-oriented characteristics in a high rotation range can be obtained.

FIG. 4 shows the first cam 21 to the third cam 2.
3 shows valve lift characteristics up to 3. The full-open output characteristics when each cam is used are as shown in FIG. 5. According to the first cam 21, although the generated torque is low, the fuel efficiency is good,
In the second cam 22, the maximum torque in the low rotation range is the highest,
The third cam 23 generates the torque in the low rotational speed range.
However, the maximum torque in the high rotation range is the largest.

By the way, the first cam 21 is switched to the second and third cams 22 and 23, and conversely, the second and third cams 2 and 23 are switched.
A control unit 51 as shown in FIG. 6 is provided to control switching from 2, 23 to the first cam 21,
The optimum cam is selected according to the operating condition.

The selection of this cam in the control unit 51 is based on the characteristics shown in FIG. 5, and when the required torque and rotation speed are in the area of the first cam 21 which is a low output fuel economy cam, this fuel economy cam is used. From this state, when the accelerator opening increases and the required torque moves out of the area of the fuel consumption cam and moves to, for example, the area of the second cam 22, which is a low-speed output cam, the fuel-saving cam is switched to the low-speed output cam, and When the rotation speed rises from a low rotation range to a high rotation range,
This is switched to the third cam 23 which is a high-speed output cam.

For this reason, the control unit 51 includes, as parameters representative of the operating state, a crank angle sensor 52 for detecting an engine speed and a crank angle position, and an accelerator operation amount sensor for detecting an operation amount (stepping amount) of an accelerator pedal. When the respective signals from 53 are input and the switching timing of the cam is determined based on these signals as described above, the solenoid valves 45 and 4 for switching the hydraulic pressure to the two hydraulic chambers 38 and 39 are used.
6 is controlled.

That is, when one of the solenoid valves 45 is opened, pressure oil from an oil pump is guided to the hydraulic chamber 38 to operate the second cam 22, and the third cam is opened by opening the other solenoid valve 46. The pressurized oil is guided to the hydraulic chamber 39 in order to make the 23 work.

By the way, if the throttle opening remains the same at the time of cam switching, the control unit 51 causes a large torque step due to the output characteristics of the cam, and the drive performance is deteriorated due to the discontinuous output fluctuation, and the body vibration is reduced. To prevent this, the opening of the throttle valve 57 provided in the intake passage is corrected and controlled in accordance with the cam switching so as to prevent this.

The opening of the throttle valve 57 is increased or decreased independently of an accelerator pedal (not shown) via a servo drive circuit 55 that receives a signal from the control unit 51 and a servo motor 56 that operates based on the drive signal. At the same time, the actual opening of the throttle valve 57 is fed back to the control unit 51 via the throttle opening sensor 54. It should be noted that the throttle valve 57 can be provided in an intake passage independent for each cylinder.

The control unit 51 basically determines the required torque from the signal of the accelerator operation amount sensor 53, calculates the throttle opening position required to generate the required torque from the cam position at that time, and calculates the servo position. Motor 56
, The opening of the throttle valve 57 is determined.

Then, the cam switching is determined, and for example, the first
The second or third cam 2 having a large output torque from the cam 21
At the time of switching to 2, 23, the opening degree of the throttle valve 57 is reduced and corrected via the servo drive circuit 55 and the servo motor 56 in accordance with the torque step with the switching target cam so as to absorb the increased torque. When switching from the second or third cams 22 and 23 to the first cam 21 having a small output torque, on the contrary, the output correction control is performed so as to increase the opening of the throttle valve 57 and absorb the torque step. I do.

Although not shown, it is also possible to further suppress the output fluctuation at the time of switching by simultaneously controlling the ignition timing of the ignition device.

Next, in the present invention, if the cam switching mechanism described above breaks down and it becomes impossible to switch the cam of a certain cylinder, the control unit 51 immediately discriminates the change and determines the fuel for that cylinder. The supply amount is corrected in accordance with the type of the cam which is not switched and is fixed.

If the cam cannot be switched and a different cam from the other cylinder is used for that cylinder, the intake charging efficiency of the cylinder greatly differs depending on the cam. Injecting this fuel causes the air-fuel ratio of that cylinder to fluctuate significantly as compared to the other cylinders, making combustion unstable.

A failure of the cam switching mechanism is when the pins 34, 35 for engaging the sub rocker arms 28, 29 with the main rocker arm 25 cause malfunction, and the pins 34, 35 do not move even when hydraulic pressure is applied. In some cases, the sub rocker arms 28 and 29 may not be engaged, or the pins 34 and 35 may not come off and the sub rocker arms 28 and 29 may remain engaged with the main rocker arm 25.

The sub rocker arm 28 or 29
Are not engaged, the second cam 22 or the third cam 23
The main rocker arm 25 is in the first position
The sub rocker arm 2 is driven by a cam 21.
When 8 or 29 remains engaged, the cam stays on, is driven by the second cam 22 or the third cam 23, and cannot be switched to another cam.

In any case, in the event of a failure, the cam is not switched to the selected one, and deterioration of combustion in the failed cylinder is inevitable.

Therefore, in the present invention, the air-fuel ratio of the exhaust gas discharged from each cylinder is detected, and an abnormality is determined based on the detected air-fuel ratio. Therefore, the controller 51 receives a signal from the exhaust sensor 60 that measures the oxygen concentration in the exhaust gas, and determines the exhaust air-fuel ratio of each cylinder based on the signal. The exhaust sensor 60 is installed at an independent exhaust passage portion of each cylinder, or the exhaust sensor 60 is installed at the junction of the exhaust passages, and the output of the exhaust sensor 60 is synchronized with the combustion order of each cylinder. Even if it is read, the exhaust air-fuel ratio of each cylinder can be measured.

FIG. 7A shows the relationship between the amount of intake air by the first cam 21 and the third cam 23 based on the amount of intake air of the cylinder when the operation is performed by the second cam 22 whose output characteristic is intermediate. 3 shows a change characteristic.

As can be seen from the relationship of the generated shaft torque in FIG. 5, the intake air amount of the third cam 23 is lower than that of the second cam 22 in the low rotation range, but increases as the engine speed increases. On the way, the intake air amount of the second cam 22 is exceeded. Further, in the case of the first cam 21, the second cam 2
2, the intake air amount further decreases as the rotational speed increases.

Therefore, the second cam 22 which is an intermediate cam
If the same amount of fuel was supplied as in the case of
In the case of 3, the air-fuel ratio gradually decreases as the rotational speed increases, and in the case of the first cam 21, the air-fuel ratio increases.

However, even when the cam switching mechanism is operating normally, the exhaust air-fuel ratio also fluctuates due to, for example, a malfunction of the fuel injection valve. FIG. 8 shows this state. If there is contamination or the like of the movable part of the fuel injection valve, the valve closes poorly, and the fuel injection amount relatively increases. If a deposit is attached to the fuel cell, the opening area is reduced and the fuel injection amount is reduced.

In order to distinguish these from the failure of the cam switching mechanism, the detected fluctuation range of the air-fuel ratio is shown in FIG.
If it does not exceed the allowable range of ± a, it is determined that it is not a failure.

At the time of failure of the cam switching mechanism, for example, as described above, when the second cam 22 which is an intermediate cam is used as a reference, the air-fuel ratio changes with a change in the number of revolutions (in other words, a change in the amount of intake air). Since the fluctuation range of the cam switching mechanism changes, it is possible to determine the failure of the cam switching mechanism by determining this inclination. When the fuel injection valve is abnormal, the variation width of the air-fuel ratio is almost the same regardless of the intake air amount, and is very small even if the inclination is present.

By the way, the fluctuation characteristics of the air-fuel ratio differ depending on the cam used as the reference for the failure judgment. FIGS. 7B and 7C show the fluctuation characteristics of the air-fuel ratio (cylinder intake air amount) based on the first cam 21 and the third cam 23, respectively. That is, when the first cam 21 is used as a reference, the air-fuel ratios of the second cam 22 and the third cam 23 are both reduced with an increase in the rotation speed, and when the third cam 23 is used as the reference, The air / fuel ratio of the first cam 21 is increased as it is, and the air / fuel ratio of the second cam 22 is increased as the rotation speed increases from a low air / fuel ratio.

Therefore, the reference cams are determined, and the characteristics of the change in the air-fuel ratio with respect to the intake air amount at that time are determined to determine which cam of the cam switching mechanism of which cylinder cannot be switched. Can be determined.

However, as shown in the failure pattern of FIG. 9, the occurrence of an abnormality is limited to the second cam 22 or the third cam 23. For example, if a pin is inserted into the second cam 22 or the third cam 23, If the first cam 21 is used as a reference, the air-fuel ratio fluctuates only when the second cam 22 or the third cam 23 is operated. From now on, the second cam 2
It can be seen that the pin does not come off the second or third cam 23.

In the same manner, when the judgment is made based on the second cam 22, the case where the operation is performed by the first cam 21 or the third cam 23 is an abnormal state. This is the time when the third cam 23 is left. Further, based on the third cam 23, the first cam 2
When the operation is performed by the first or second cam 22, the third cam 2
This is the case where no pin is required for No. 3 or the pin remains in the second cam 22.

As described above, when the cam switching abnormality is determined from the fluctuation characteristics of the air-fuel ratio on the basis of each cam, six types of abnormalities can be determined. However, since four types of abnormalities actually occur, all of them are executed. Then, they are determined redundantly.

Therefore, it is possible to determine an abnormality without actually determining the variation characteristics of the air-fuel ratio with respect to the intake air amount on the basis of all the cams.

For example, first, if it is determined from the air-fuel ratio fluctuation characteristic that the second cam is an intermediate cam as a reference (abnormality does not enter the second cam 22 or escape from the third cam 23),
Next, assuming that the first cam 21 is used as a reference, one of the abnormality occurrence patterns at this time is to keep entering the third cam 23, which is already known when the second cam 22 is used as a reference. By simply determining whether or not the deviation amount of the air-fuel ratio has exceeded the reference value, it is possible to determine a new abnormality that the second cam 22 does not come off. In the same manner, since it has already been determined from the deviation amount of the air-fuel ratio with respect to the third cam 23 that the second cam 22 has not escaped, another abnormal state, that is, the third cam 23 You can see that it does not enter

By the way, when it is confirmed that the cam switching is disabled in this way, the driver is immediately notified of the occurrence of an abnormality, but at the same time, in order to prevent the combustion in the failed cylinder from deteriorating, the failure of the cylinder is prevented. The fuel supply amount injected from the fuel injection valve 61 is corrected so as to correspond to the cam that cannot be switched, so that the air-fuel ratio of the cylinder does not greatly deviate from the target value (generally, the stoichiometric air-fuel ratio). To

Next, such control executed by the control unit 51 will be described with reference to the flowcharts of FIGS.

First, in step 1, the throttle opening is compared with a preset reference value, and when it is determined that the quasi-steady operation is equal to or less than the reference value, in step 2, the intake air amount Qa ₀
Is read, and it is determined whether or not it is in the use area of the second cam 22, which is the reference intermediate cam (step 3).

When the second cam 22 is in the use range, a failure is determined from the air-fuel ratio of each cylinder, but no failure determination is performed in other cam ranges.

In steps 4 and 5, the air-fuel ratio (A / F value) of each cylinder is read, and the average air-fuel ratio AF of the entire cylinder is obtained from the air-fuel ratios AF ₁ , AF ₂ , AF ₃ and AF _{4 of} each cylinder. Is calculated, and a deviation ΔAFi of the air-fuel ratio AFi of each cylinder with respect to the average air-fuel ratio AF is calculated.

In step 6, the absolute value of ΔAFi is compared with a predetermined reference value a (see FIG. 7 (A)). The difference between the air-fuel ratios is determined for the first cam 21 and the third cam 23, respectively.

When the deviation ΔAFi of the air-fuel ratio is equal to or greater than the reference value, the flow waits for a certain period of time in Steps 7 to 9 to take place. The quantity Qa ₁ is read. Then, when the change value (Qa ₁ -Qa ₀ ) of the intake air amount reaches a predetermined value or more, it is determined again whether the reference cam (second cam) is in use or not. In steps 12 and 13 again, the air-fuel ratios BF ₁ , BF ₂ and B
After reading F ₃ and BF ₄ , the average air-fuel ratio BF of all cylinders is calculated, and the deviation ΔBFi of the air-fuel ratio of each cylinder is calculated.

Then, in steps 14 and 15, the absolute value of the deviation ΔBFi is compared with the above-mentioned predetermined reference value a, and when the deviation is large, the intake air amount changes from Qa ₀ to Qa.
definitive when changes to a _1, the air-fuel ratio of the amount of deviation of the variation range, i.e. the difference of ΔAFiΔ and BFi, calculates the slope C of inclination of the air-fuel ratio fluctuation range.

After calculating the gradients C of the respective gradients in this manner, the values are compared with a specified value d (for example, a certain positive value, see FIG. 7A) in step 16, and when the value is larger than the specified value, (The gradient is positive), and the third cam 22 is designated as the cam of the cylinder (i-cylinder) despite the command.
Since the cam is used, it is determined that the pin 35 is still engaged with the sub rocker arm 29 (step 18).

On the other hand, when the value is smaller than the specified value (the gradient is negative), the first cam 21 is set even though the second cam 22 is commanded as the cam of the cylinder. It is determined that the pin 34 of the sub rocker arm 28 of the second cam 22 does not enter (step 17).

As described above, when the deviation amount of the air-fuel ratio exceeds the range of the predetermined reference value and the gradient of the fluctuation width of the air-fuel ratio before and after the change in the intake air amount exceeds a certain value. This is not due to the error of the fuel injection valve, etc., but the case where the cam switching mechanism of the cylinder has failed and the used cam is operated with a different cam from the selected reference cam, and the air-fuel ratio fluctuation Failure can be determined from the width gradient.

These failure states are output to an abnormality display device or the like in step 19 to inform the driver.

On the other hand, if the deviation amount of the air-fuel ratio is smaller than the reference value a in step 6, the process proceeds to step 20 to determine whether or not the first cam 21 is in use. The determination of the air-fuel ratio is performed using 21 as a reference cam. That is, when the reference cam is the second cam 22, even if there is an abnormality that the reference cam remains fixed to the second cam 22 or does not enter the third cam 23 (but enters the second cam 22), Because the air-fuel ratio does not deviate,
These decisions cannot be made.

Then, the deviation amount ΔCFi of the air-fuel ratio when the first cam 21 is used as the reference cam is calculated in the same manner as in steps 3 to 5 and compared with the reference value (steps 21 and 22). .

When the deviation amount ΔCFi of the air-fuel ratio is equal to or larger than the reference value, the used cam is the second cam 22 or the third cam 23. However, when the air-fuel ratio is fixed to the third cam 23, the air-fuel ratio deviation Δ
Since AFi does not fall below the reference value, in this case the second
It can be determined that it is fixed to the cam 22 (step 23).

On the other hand, if ΔCFi is equal to or smaller than the reference value, the process goes to step 24 to determine whether or not the third cam 23 is in use. Then, the deviation amount ΔDFi of the air-fuel ratio is calculated (step 25). Then, the deviation amount ΔDFi of the air-fuel ratio at this cam is compared with the reference value, and when it is larger than the reference value, the second cam 22 or the first cam 22 is in spite of the instruction to the third cam 23. Since the first cam 21 is used, it can be determined that the third cam 23 does not enter in this case (steps 26 and 27).

The abnormal pattern of the cam switching mechanism is as follows.
As described above, there are cases where the second cam or the third cam does not enter, and cases where the second cam or the third cam does not come off.
8, 23, 27, all can be determined.

And, if none of these,
In step 28, it is determined that everything is normal.

If an abnormality has occurred in the cam switching, the fuel supply amount of the cylinder is corrected in step 29. In this case, steps 18 and 23
When the second cam 22 or the third cam 23 is not kept, the fuel supply amount is always corrected in accordance with the intake air amount (cylinder filling air amount) by each cam.

In step 17, the second cam 22
If it is determined that the second cam 22 is not commanded, the fuel supply amount is corrected to the first cam 21 only when the second cam 22 is commanded. When the fuel supply amount is the same, and it is determined in step 27 that the fuel does not enter the third cam 23, the fuel supply amount is corrected to the fuel supply amount corresponding to the first cam 21 only when the third cam 23 is commanded. No correction is made for a cam.

As described above, when an abnormality occurs in the cam switching mechanism, the fuel supply amount is corrected so that the air-fuel ratio of the abnormal cylinder does not significantly deviate. It is possible to prevent deterioration of sex.

In this embodiment, the second cam 22, which is an intermediate cam, is selected as a reference cam, and an abnormality is determined from the gradient of the fluctuation width of the air-fuel ratio at this time. Although the abnormality is determined from the deviation amount of the air-fuel ratio by the cam 23, even when more cams are provided, the intermediate output characteristic (intake charging efficiency) is used as a reference.
It will be readily appreciated that similar decisions can be made.

As described above, according to the present invention, an intermediate
Means for determining a difference in air-fuel ratio of each cylinder with respect to an average air-fuel ratio of all cylinders based on a valve operation mode having output characteristics; and a gradient of an air-fuel ratio difference for cylinders in which the difference in air-fuel ratio exceeds a reference value. because having a means for determining the magnitude valve operation mode changeover switching is not capacity from of became changeover impossible from the gradient magnitude of the difference between the air-fuel ratio when the intake air amount has changed field
Can be accurately determined Lube operating mode, and since determination in this manner based on the exhaust air-fuel ratio measured abnormality of the valve operation mode changeover mechanism, for abnormality determination to the switching mechanism portion of the valve operation mode There is no need to install a detecting means, so that the structure can be simplified and the cost can be reduced. In addition, when the valve operation mode in which the cylinder in which the abnormality has occurred cannot be switched is specified, the change in the air-fuel ratio is prevented by correcting the fuel supply amount only for the cylinder corresponding to the valve operation mode. Can be repaired,
Anyway, it is possible to avoid misfiring and unstable combustion in the cylinder.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a plan view of the variable valve mechanism according to the embodiment of the present invention.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is an explanatory diagram showing lift characteristics of each cam.

FIG. 5 is an explanatory diagram showing output characteristics of each cam based on torque and rotation speed.

FIG. 6 is a block diagram of a control unit.

FIGS. 7A, 7B, and 7C show a second cam and a first cam, respectively.
FIG. 9 is an explanatory diagram showing a change characteristic of an intake air amount based on a cam and a third cam.

FIG. 8 is an explanatory diagram illustrating a relationship between an injection pulse and an injection amount of a fuel injection valve.

FIG. 9 is an explanatory diagram showing an occurrence pattern of a cam abnormality.

FIG. 10 is a part of a flowchart showing a control operation executed in the control unit.

FIG. 11 is a flowchart showing a control operation executed in the control unit, which is the remaining part of FIG. 10;

[Explanation of symbols]

 21 First cam 22 Second cam 23 Third cam 24 Intake / exhaust valve 25 Main rocker arm 28 Sub rocker arm 29 Sub rocker arm 34 Pin 35 Pin 51 Control unit 52 Crank angle sensor 53 Accelerator operation amount sensor 60 Exhaust sensor 61 Fuel injection valve

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI F02D 43/00 301 F02D 43/00 301Z (56) References JP-A-1-110817 (JP, A) JP-A-2-42152 (JP, A) JP-A-4-14842 (JP, A) JP-A-4-159426 (JP, A) JP-A-4-269353 (JP, A) JP-A-1-110817 (JP, A) JP-A-2-42152 (JP, A) JP-A-63-167016 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 13/02 F01L 13/00 F02D 41/22 F02D 41/36 F02D 43/00

Claims (2)

(57) [Claims] 1. A at least three valve operation mode different respective output characteristics is disposed for each cylinder, these bars
A means for calculating a fuel supply amount based on an intake air amount of an engine in an internal combustion engine having a mechanism for switching a lube operation mode according to operating conditions, and distributing and supplying the calculated fuel amount to each cylinder evenly , Means for determining the exhaust air-fuel ratio of each cylinder, and operation of the valve whose output characteristic is located in the middle.
Means for determining whether a difference between the air-fuel ratio of each cylinder with respect to the average air-fuel ratio of all cylinders exceeds a reference value in an operating range using the aspect, and the air-fuel ratio with respect to the intake air amount for the cylinders exceeding the reference value. bar of the switching switching is not capacity from the size of the gradient of the difference
Means for determining a lube operation mode . A failure judgment apparatus for a valve operation mode switching mechanism. Wherein at least three valve operation mode different respective output characteristics is disposed for each cylinder, these bars
A means for calculating a fuel supply amount based on an intake air amount of an engine in an internal combustion engine having a mechanism for switching a lube operation mode according to operating conditions, and distributing and supplying the calculated fuel amount to each cylinder evenly , Means for determining the exhaust air-fuel ratio of each cylinder, and operation of the valve whose output characteristic is located in the middle.
Means for determining whether a difference between the air-fuel ratio of each cylinder with respect to the average air-fuel ratio of all cylinders exceeds a reference value in an operating range using the aspect, and the air-fuel ratio with respect to the intake air amount for the cylinders exceeding the reference value. bar of the switching switching is not capacity from the size of the gradient of the difference
Means for determining Lube operating mode, Bal became changeover impossible
Only the cam operation that cylinder when the blanking operation mode is identified
Means for correcting the fuel supply amount corresponding to the operating mode of the dynamic valve .