JPH07233742A - Diagnosing device of valve drive control device for engine - Google Patents

Abstract

PURPOSE:To accurately diagnose that a switching of cam is normally performed or not. CONSTITUTION:A rise ratio dP/dthetaR of an in-cylinder pressure sensor 106 in a specified block is detected. On the other hand, on the basis of the high-speed/ low-speed cam switching command condition and the operation condition of an engine 101, a rise ratio dP/dthetath estimated to be obtained in the case where switching of cam is normally performed is set. A learning correction coefficient alphaof the estimated rise ratio dP/dthetath is set. A value obtained by multiplying an absolute value of a deviation between the ineasured pressure rise ratio dP/dthetaR and the estimated rise ratio dP/dthetath by the learning correction coefficient alphais used as a deviation S of the pressure rise ratio. At this stage, in the case where the deviation S exceeds a predetermined value, a judgement that a switching to a cam corresponding to the switching signal from the control unit 103 is not performed is made to judge a fault of a variable valve drive mechanism 102.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for a valve drive control device of an engine, and more specifically, in an engine in which the valve opening characteristic is switched according to operating conditions, the valve opening characteristic is actually switched in response to a switching command. The present invention relates to a device for diagnosing whether or not it is installed.

[0002]

2. Description of the Related Art Conventionally, the lift characteristic (opening characteristic) of an intake valve or an exhaust valve is changed to, for example, a high-speed cam for the purpose of achieving both high torque characteristics at low and medium speed operation and improved output at high speed operation. It is known that the low-speed cam and the low-speed cam are used differently depending on operating conditions, and thereby the intake / exhaust timing or the intake / exhaust amount is controlled (Japanese Patent Laid-Open Nos. 63-167016 and 63/63). -5780
5 and JP-A-5-171909).

[0003]

By the way, in the above valve drive control device, when the valve opening characteristic (cam) is not actually switched in response to the switching request, the desired output characteristic is obtained. Therefore, it is required to diagnose whether or not the switching of the valve opening characteristic is normally performed.

As a method of detecting the switching operation of the valve opening characteristic (cam), a hydraulic sensor for detecting the operating hydraulic pressure which is the operation source of the cam switching is conventionally provided, and the desired result is detected based on the detection result of the hydraulic sensor. There is a method of detecting whether or not the switching operation is performed (Japanese Patent Publication No. 37573).
No. 0 publication). However, in the configuration in which the cam switching operation is detected based on the working oil pressure as described above, this is diagnosed when a failure occurs in which the working oil pressure is proper but the cam is not actually switched. However, there was a problem that the reliability of diagnosis could not be secured.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a diagnostic device capable of surely diagnosing whether or not the switching of valve opening characteristics is normally performed.

[0006]

Therefore, the diagnostic device in the engine valve drive control device according to the invention of claim 1 is constructed as shown in FIG. In FIG. 1, the valve opening characteristic switching means is a means for switching the valve opening characteristic of the engine to a plurality of preset values, and the switching command output means is a valve opening characteristic switching means for the valve opening characteristic switching means according to operating conditions. Outputs the open characteristic switching command.

On the other hand, the in-cylinder pressure detecting means detects the in-cylinder pressure of the engine, and the predictive characteristic value setting means sets the predictive characteristic value of the in-cylinder pressure in the valve opening characteristic corresponding to the switching command. Then, the switching control diagnosis means compares the predicted characteristic value set by the predicted characteristic value setting means with the detection result of the in-cylinder pressure by the in-cylinder pressure detection means, and switches the valve opening characteristic by the valve opening characteristic switching means. Diagnose whether it is performed normally.

In the diagnostic device according to the second aspect of the present invention, the predictive characteristic value setting means sets the change rate of the in-cylinder pressure in a specific section as a predictive characteristic value for each valve opening characteristic, and the switching control is performed. When the diagnosing means has a deviation between the predicted in-cylinder pressure change rate and the in-cylinder pressure change rate in the specific section detected by the in-cylinder pressure detecting means that is greater than or equal to a predetermined value, a failure of the valve opening characteristic switching means is detected. It is configured to judge.

Further, in the diagnostic device according to the third aspect of the present invention, the predictive characteristic value setting means sets the integral value of the in-cylinder pressure in the specific section as a predictive characteristic value for each valve opening characteristic, and the switching control diagnostic means. When the deviation between the predicted integrated value of the in-cylinder pressure and the value of the in-cylinder pressure detected by the in-cylinder pressure detecting means integrated within the specific section is equal to or more than a predetermined value, the valve opening characteristic switching means It is configured to determine a failure.

Further, in the diagnosing device according to the invention of claim 4, the predictive characteristic value setting means sets the in-cylinder pressure at a specific crank angle position as a predictive characteristic value for each valve opening characteristic, and the switching control diagnosing means. When the deviation between the predicted in-cylinder pressure at the specific crank angle position and the in-cylinder pressure detected at the specific crank angle position by the in-cylinder pressure detecting means is a predetermined value or more, the valve opening characteristic switching means It is configured to determine the failure of.

Further, in the diagnostic device according to the invention of claim 5, the in-cylinder pressure characteristic value detected by the in-cylinder pressure detecting means when the switching control diagnosing means makes a normal determination of the valve opening characteristic switching means. Based on the above, the predictive characteristic value learning means for learning and correcting the predictive characteristic value set by the predictive characteristic value setting means is provided.

[0012]

In the diagnostic device according to the first aspect of the present invention, the characteristic of the in-cylinder pressure predicted to be obtained by the valve opening characteristic corresponding to the switching command is compared with the actually detected in-cylinder pressure. Then, when the actual in-cylinder pressure does not match the predicted characteristic, it is determined that the characteristic of the in-cylinder pressure deviates from the prediction because the valve opening characteristic corresponding to the switching command is not obtained.

That is, when the valve opening characteristic is switched,
In general, the suction efficiency changes, which affects the in-cylinder pressure, so that different in-cylinder pressure characteristics are exhibited for each valve opening characteristic. Therefore, the in-cylinder pressure characteristics are obtained in advance for each valve characteristic, and the predicted valve-open characteristic corresponding to the switching command is compared with the actually detected in-cylinder pressure to obtain the desired valve-open characteristic. It is possible to diagnose whether or not.

In the diagnostic device according to the second aspect of the present invention, the rate of change of the in-cylinder pressure in a specific section is used as the predictive characteristic value of the in-cylinder pressure, and each of the values varies depending on the difference in suction efficiency due to the valve opening characteristic. The in-cylinder pressure change rate for each valve opening characteristic is obtained in advance, and the switching of the valve opening characteristic is normally performed depending on whether the actually detected pressure change rate corresponds to the desired valve opening characteristic. Diagnose whether it is done.

In the diagnostic device according to the third aspect of the present invention, as the predicted characteristic value of the in-cylinder pressure, the integrated value of the in-cylinder pressure in the specific section is used, and each valve is determined according to the difference in the suction efficiency due to the valve opening characteristic. The in-cylinder pressure integrated value for each opening characteristic is obtained in advance, and switching of the valve opening characteristic is normal depending on whether the actually detected in-cylinder pressure integrated value corresponds to the desired valve opening characteristic. It is diagnosed whether or not it is performed.

According to the fourth aspect of the present invention, the in-cylinder pressure at the specific crank angle position is used as the predictive characteristic value of the in-cylinder pressure, and the valve opening characteristics corresponding to the difference in the intake efficiency depending on the valve opening characteristics are used. The in-cylinder pressure at the specific position for each characteristic is obtained in advance, and the valve opening characteristic is switched depending on whether or not the in-cylinder pressure actually detected at the specific position corresponds to the desired valve opening characteristic. It is diagnosed whether is performed normally.

In the diagnostic device according to the fifth aspect of the present invention, the prediction characteristic value is learned to improve the diagnostic accuracy.
That is, when it is determined by the diagnosis based on the in-cylinder pressure characteristic value that the switching of the valve opening characteristic is normally performed, the in-cylinder pressure detection value which is the basis of the determination is the valve opening characteristic corresponding to the switching command. It is the value actually obtained in. On the other hand, in the diagnosis using the fixed predictive characteristic value, if there is deterioration over time in the cylinder pressure or variation among engines, the accuracy of diagnosis will decrease. By learning correction of the prediction characteristic value using
The predicted characteristic value is modified to a value that matches the actual engine condition.

[0018]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a diagram showing an outline of the system configuration of this embodiment. This Figure 2
In the engine 101, a variable valve drive mechanism 102 (valve opening characteristic switching means) for changing the opening characteristic (lift amount and opening period) of the intake valve by switching between the high speed cam and the low speed cam is provided. ing.

The variable valve drive mechanism 102 switches the cam for driving the intake valve to one of the high speed cam and the low speed cam in response to a switching command from a control unit 103 having a built-in microcomputer. To do. Therefore, in this embodiment, the function as the switching command output means is the control unit 103.
Is equipped with.

The control unit 103 includes an intake air flow rate signal Qa from an air flow meter 104, a crank angle signal from a crank angle sensor 105, and a cylinder pressure sensor 10.
The in-cylinder pressure signal P from 6 (in-cylinder pressure detection means) is input. In the present embodiment, the in-cylinder pressure sensor 106 is a spark plug as disclosed in Japanese Utility Model Laid-Open No. 63-17432.
I used the type that was installed as a washer for 107. That is, the in-cylinder pressure sensor 106 is a sensor including a piezoelectric element and an electrode formed in a ring shape, and is sandwiched between the spark plug 107 and the cylinder head, and the spark plug is displaced by receiving the combustion pressure. The output is changed by.

The in-cylinder pressure sensor is not limited to the above-mentioned washer type sensor.
It may be of a type in which the sensor unit disclosed in Japanese Patent No. 557 is directly exposed to the combustion chamber to detect the in-cylinder pressure as an absolute pressure. Here, FIGS. 3 to 6 show specific examples of the variable valve drive mechanism 102. Explaining this, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves V. The base end of the rocker arm 1 is a hollow main rocker shaft 3 common to each cylinder.
The rocker arm 1 is swingably supported by the cylinder head through the respective ends of the bifurcated rocker arm 1 and abuts on the stem top of the intake valve V.

The rocker arm 1 is formed into a substantially bifurcated shape in a plan view, and the rocker arm 1 is provided with a single free cam follower 2 approximately above the center thereof. And FIG.
At both sides of the free cam follower 2, low speed cam 2
Rollers 11, 11 with which 1, 21 abut are provided. The base end of the free cam follower 2 is swingably (relatively rotatable) supported by the rocker arm 1 via a sub-rocker shaft 16. The free cam follower 2 does not have a portion that comes into contact with the intake valve V, and a cam follower portion 2A that slidably contacts the high speed cam 22 is formed at the tip of the free cam follower 2 so as to project in an arc shape.

A recess 27 into which a spring retainer 29 is slidably fitted is formed on the lower side of the free cam follower 2, and the base end of the spring retainer 29 is supported on the bottom surface of the recess 27. The elastic biasing force of the coil spring 26 makes contact with the rocker shaft 3. Further, in the free cam follower 2 described above, below the cam follower portion 2A, a step portion 2B with which a later-described lever member 7 engages and an inclined portion 2C continuous with this are formed. Further, below the rocker arm 1, there is provided a lever member 7 which is swingably supported by a pin 6 on the side of the rocker shaft 3.

A protrusion 7 is provided on the upper side of the lever member 7.
A is integrally formed and is urged by a return spring 9 and a spring retainer 10 housed in a recess 8 formed in the rocker arm 1 in a direction in which the engagement with the free cam follower 2 is released. On the other hand, at the lower end of the lever member 7, an operating plunger 31 driven by the supply of operating hydraulic pressure to the hydraulic chamber 34 provided in the rocker arm 1.
Are in contact.

The oil passage for guiding the working hydraulic pressure to the hydraulic chamber 34 is
It is provided through the inside of the rocker arm 1 and the main rocker shaft 3. The rocker arm 1 is formed with a through hole 41 having one end opened to the hydraulic chamber 34 and the other end penetrating the bearing surface for the main rocker shaft 3. Also,
An oil gallery 42 is axially formed inside the main rocker shaft 3, and the oil gallery 42 communicates with a through hole 41 of the rocker arm 1 through a through hole 43.

In the oil gallery 42, an oil pump (engine driven by an engine via a switching valve 51 whose operation is controlled in response to a switching command signal (energization control signal) output from the control unit 103 The discharge hydraulic pressure (not shown) is selectively guided. Low speed cam 2
1, 21 and the high speed cam 22 between them are integrally formed on a common cam shaft 20, and satisfy the valve lift characteristics (open characteristics) required at low engine speed and high engine speed. Are formed in different shapes.
That is, the high speed cam 22 has a cam profile that makes at least one of the valve lift amount and the valve open period larger than the low speed cam 21. In this embodiment, the valve lift amount and the opening period are both increased, and the valve opening characteristic can be switched between two types by properly using the high speed cam 22 and the low speed cam 21. There is.

According to the variable valve drive mechanism 102 having the above structure, the rocker arm 1 swings according to the cam profile of the low speed cam 21 to open / close each intake valve V when the hydraulic pressure is not supplied to the hydraulic chamber 34. . At this time,
Although the free cam follower 2 is swung by the high speed cam 22, the lever member 7 is in the position shown by the solid line in FIG. 5 due to the biasing force of the spring 9. Therefore, even if there is an input from the free cam follower 2, only the spring 26 bends and the movement of the rocker arm 1 is not affected.

On the other hand, when the working hydraulic pressure is supplied to the hydraulic chamber 34, the working plunger 31 swings the lever member 7 against the return spring 9 and returns it to the position shown by the broken line in FIG. . In this state, the end portion of the lever member 7 engages with the step portion 2B of the free cam follower 2 so that the rocker arm 1 and the cam follower 2 are connected and integrated, and swing about the main rocker shaft 3. become.

Since the high-speed cam 22 is formed so that both the valve opening angle and the valve lift amount are larger than the low-speed cam 21, the free cam follower 2 is integrated with the rocker arm 1. Rocker arm 1 when rocking
Roller 11 floats up from low speed cam 21, and each intake valve V is driven to open and close according to the profile of high speed cam 22, so that both the opening angle and the lift amount increase.

On the other hand, switching from the high speed cam 22 to the low speed cam 21 lowers the hydraulic pressure introduced to the hydraulic chamber 34 by the control of the switching valve 51, and the elastic restoring force of the return spring 9 causes the lever member 7 and the actuating plunger. This is performed by moving 31 to the original position (the position indicated by the solid line in FIG. 5) and releasing the lock of the rocker arm 1. As described above, by selectively supplying the working oil pressure to the hydraulic chamber 34 by the switching valve 51, the valve opening characteristic adapted to the low speed range according to the profile of the low speed cam 22 and the low speed according to the profile of the high speed cam 21 are provided. It is possible to switch and select either the valve opening characteristic that is suitable for a high speed range in which the opening angle and the lift amount are larger than those of the use cam 22.

In this embodiment, the valve opening characteristic switching means is constituted by the rocker arm 1, the free cam follower 2, the lever member 7, the plunger 31, the hydraulic chamber 34, the switching valve 51 and the like. In the present embodiment, switching between the high speed cam 21 and the low speed cam 22 is performed by rocking the lever member 7 as described above.
Although it is configured to be performed depending on whether or not to connect,
The cam switching mechanism is not limited to the above configuration.

For example, as disclosed in JP-A-63-167016 and JP-A-63-57805, a high speed rocker arm and a low speed rocker arm are fitted in a direction parallel to the rocker shaft. A configuration may be adopted in which the high speed cam and the low speed cam are switched by selectively connecting and disconnecting the hole and the plunger.

Further, instead of using a plurality of cams separately, it is possible to mount a cam sprocket for controlling the cam phase while maintaining a constant operating angle on the cam shaft and switch the intake valve opening / closing timing to an appropriate timing for each speed range. Variable valve timing controller ("New model vehicle manual (FGY32-
1) ”, pages B-44 to B-45, edited and published by Nissan Motor Co., Ltd., published in August 1991, etc.), and the configuration of the variable valve drive mechanism 102 is limited to the cam switching structure. Not a thing.

Further, in this embodiment, two types of cams, one for high speed and the other for low speed, are provided and these are switched and used. However, even if three or more types of cams are selectively used according to operating conditions. good. Here, the control unit 103 as the switching command output means determines which of the high-speed cam 22 and the low-speed cam 21 to be used according to the engine operating conditions such as the engine load state and the engine rotation speed, and according to the determination. A switching command is output to the switching valve 51 to control the intake valve to be driven by the cam corresponding to the determination.

However, even if a switching command is output to the switching valve 51 in order to achieve the desired cam state, there is a possibility that the switching of the cam will not be executed normally and the control unit 103 will be affected. It has the function of diagnosing the occurrence of failures as shown below. The flow chart of FIG. 7 shows the first embodiment of the diagnostic control by the control unit 103. In this embodiment, the control unit 103 has the functions of the predictive characteristic value setting means, the switching control diagnosing means, and the predictive characteristic value learning means, as software, as shown in the flowchart of FIG.

In the flowchart of FIG. 7, first, step 1 (denoted as S1 in the figure. The same applies hereinafter).
Then, the engine speed Ne and the basic fuel injection amount Tp representing the engine load are read. The basic fuel injection amount Tp is calculated by another program (not shown), and is calculated based on the intake air flow rate Qa detected by the air flow meter 104 and the detection signal from the crank angle sensor 105. It is calculated based on the rotation speed Ne.

In the next step 2, it is determined whether or not the diagnosis is possible based on the engine speed Ne and the engine load (basic fuel injection amount Tp). Here, in the case where the respective cam use operation regions are set based on the engine load Tp and the rotation speed Ne as shown in FIG. 10, for example, the diagnosable region is a cam shown by diagonal lines in FIG. It is preferable to set the operating region before and after the switching operating condition. This is because when the diagnosis is performed under operating conditions close to the switching operating conditions, due to the operation delay of the switching mechanism,
This is to prevent the diagnosis from being performed in a state where the cam is operating normally but not switched to the cam corresponding to the switching command. Therefore, the condition that can be diagnosed may be that the predetermined time has elapsed after the switching command.

When it is determined in step 2 that the area is the diagnosable area, the process proceeds to step 3 and the cylinder pressure sensor 10 is operated.
The output of 6 is sampled, and in step 4, the average value of the pressure increase rate in a specific section (for example, 40 ° after bottom dead center to 40 ° before top dead center) during the compression stroke based on the sampled cylinder pressure P. Calculate dP / dθ _R. For example, the cylinder pressure P
When the specific section for which the increase change rate is calculated is 40 ° after bottom dead center to 40 ° before top dead center, the cylinder pressure P ₁ detected at 40 ° before top dead center and the bottom dead center before that The deviation from the in-cylinder pressure P ₂ detected at 40 ° afterward is set to 100 at the sampling interval θ.
The value obtained by dividing by the pressure increase rate average value dP / dθ _R (←
(P ₁ −P ₂ ) / θ). That is, dP / dθ _R is
It is data showing an increase rate when it is assumed that the in-cylinder pressure changes at a constant rate within the specific section.

In the next step 5, the current operating condition is that the high speed cam 22 is used, and the control unit
It is determined by 103 whether or not the switching command for the high speed cam 22 is output to the switching valve 51.
If it is determined in step 5 that the command to switch to the high speed cam 22 is output, the process proceeds to step 6, and if the high speed cam 22 is actually used, the specific section A prediction in which the pressure increase rate average value dP / dθ _th (prediction characteristic value) predicted to be obtained is stored in advance as the prediction value dP / dθ _th for each operating region divided by the engine load and the engine rotation speed Ne. Set by referring to the characteristic map.

Further, in the next step 7, for each operation region that is divided by the engine load and the engine rotational speed Ne, the predicted value dP / d [theta] _th diagnostic control using the (predicted value dP / dθ _th) correction The learning correction map for storing the learning correction coefficient α is referred to, and the correction coefficient α corresponding to the current driving condition is obtained. Similarly, when it is determined in step 5 that the switching command to the low speed cam 21 is being output, the process proceeds to step 8 and the low speed cam 21 is executed.
The predicted value (expected value) dP / dθ _th of the average value of the pressure increase rate in the state where is used is calculated by referring to the prediction characteristic map for the low speed cam, and in step 9, the learning correction coefficient α is set. See the map for the request.

Predicted value (expected value) of the average value of the pressure increase rate
2 for high-speed cam and low-speed cam storing dP / dθ _th
One predictive characteristic map is provided for each low speed cam in advance.
21 is a map in which the rate of increase calculated based on the in-cylinder pressure P actually detected when the valve is driven by the high-speed cam 22 is stored. Further, the learning correction coefficient α stored in the map for each cam is a correction coefficient for dealing with the change in the pressure increase rate dP / dθ due to the time-dependent change or dispersion of the engine, and is updated and set as described later. It

When the predicted value dP / dθ _{th of the} average pressure increase rate and the learning correction coefficient α are obtained as described above, the process proceeds to step 10 and is actually calculated based on the detected value of the in-cylinder pressure sensor 106. The learning correction coefficient α is set to the absolute value of the deviation between the pressure increase rate dP / dθ _R and the predicted increase rate dP / dθ _th predicted to be obtained if the cam corresponding to the switching command is actually used. The value obtained by multiplying by is set as data S indicating the deviation between the actual pressure increase rate and the predicted increase rate.

Then, in the next step 11, the deviation S
Is compared with a predetermined value. Here, when the deviation S exceeds the predetermined value, the cam is not switched in response to the switching command, and the valve is driven by the cam that does not correspond to the command. It is considered that a deviation of a predetermined value or more has occurred between the predicted value and the actual value of the pressure increase rate on the assumption that switching is being performed, and the step
Going to 12, the failure judgment of the variable valve drive mechanism 102 is performed.

That is, there is a difference in suction efficiency between the case where the valve is driven by using the high speed cam 22 and the case where the valve is driven by using the low speed cam 21, and the difference in the suction efficiency is caused by the pressure increase rate. It will be detected as a difference of dP / dθ. Therefore, the pressure increase rate is calculated in advance as a predicted value (expected value) for each of the case of driving by the high speed cam 22 and the case of driving by the low speed cam 21, and the actually detected pressure increase rate is When there is a large difference from the predicted value in the cam state corresponding to the switching command at this time, the cam corresponding to the switching command is not actually switched, and the difference in suction efficiency due to the difference in cam causes the deviation It is presumed that it was detected as S, and the occurrence of failure is determined.

On the other hand, when it is determined in step 11 that the deviation S is less than or equal to the predetermined value, it means that the actual pressure increase rate is sufficiently close to the predicted value. It is determined that the variable valve drive mechanism 102 is normally operated, and the process proceeds to step 13 to determine that the variable valve drive mechanism 102 is operating normally. After the normality is determined, the process proceeds to step 14 and the learning correction coefficient α is updated and set. When it is determined in step 11 that the deviation S is less than or equal to the predetermined value, a normal determination is made. However, if the setting accuracy of the predicted value dP / dθ _th is good, originally,
dP / dθ _R −dP / dθ _th should be approximately 0,
The deviation S at the time of normality determination indicates the deviation of the predicted value.

Therefore, in step 14, the predicted value dP / d
The learning correction coefficient α is updated and calculated so that θ _th approaches the measured value dP / dθ _R , and in step 15, the learning correction coefficient α calculated in step 14 is mapped as data corresponding to the corresponding area of the corresponding map. Rewrite data. The update calculation of the learning correction coefficient α is performed by, for example, α ← 1.
/ (Dp / dθ _th ) ・ dP / dθ _R × 1/100 +99/10
It is preferable that the correction is performed as 0 × α to avoid a sudden change in the learning correction coefficient α. In the above-described embodiment, the deviation S is corrected and set by the learning correction coefficient α, but this is substantially for learning correction of the error of the predicted value dP / dθ _th , and therefore the learning correction coefficient α is Instead of correcting the deviation S, the predicted value dP / dθ _th may be set as a value for directly correcting.

According to the above embodiment, the cam switching operation is normally performed depending on whether the pressure increase rate of the in-cylinder pressure matches the value expected to be obtained by the cam corresponding to the switching command. Since it is diagnosed whether or not the failure factor is not limited, it is possible to finally diagnose that the cam corresponding to the switching command is not switched.
It is possible to provide a highly reliable diagnostic result.

Further, in the above embodiment, the learning correction coefficient α can absorb the fluctuation of the pressure increase rate due to the time-dependent change or variation of the engine, so that the diagnostic performance based on the pressure increase rate can be stably maintained. Is. Also,
With the configuration in which the diagnosis is performed based on the pressure increase rate as described above, the diagnosis can be performed without being affected by the offset of the output of the in-cylinder pressure sensor.

In the first embodiment, the difference in the suction efficiency due to the cam is detected through the pressure increase rate during the compression stroke. However, instead of the pressure increase rate, the in-cylinder pressure integrated value is used to determine the suction efficiency. A second embodiment in which the difference may be detected and the cam switching operation is diagnosed by using the in-cylinder pressure integrated value is shown in the flowchart of FIG.

Each step in the flow chart of FIG. 8 basically replaces the pressure increase rate dP / dθ in the flow chart of FIG. 7 described above with the in-cylinder pressure integrated value IMEP, and will be described briefly below. First, it is confirmed based on the rotation speed Ne and the engine load Tp that it is in the diagnostic range (steps 21 and 22), and the cylinder pressure P detected by the cylinder pressure sensor 106 during a predetermined crank angle period (specific section).
Is integrated to calculate an in-cylinder pressure integrated value IMEP _R (steps 23 and 24).

The predetermined crank angle range may be a predetermined angle range before compression top dead center, or may be an angle range including the compression stroke to the explosion stroke. Any angular range is acceptable as long as the change is reflected in the integrated value. When the in-cylinder pressure integrated value IMEP _R is obtained, the predicted value IMEP _th for determining whether or not the integrated value IMEP _R is a value corresponding to the case where the cam corresponding to the switching command is used, is calculated for each cam. Obtained by referring to the provided map (steps 26 and 28), and further, the predicted value IM
A learning correction coefficient α for adapting the EP _th to the engine state (change with time, variation) is obtained by referring to a map (steps 27 and 29).

Then, a value obtained by multiplying the learning correction coefficient α by the absolute value of the deviation between the actually measured integrated value IMEP _R and the predicted value IMEP _th is finally set as the deviation S of the integrated value (step 3
0) If the deviation S exceeds a predetermined value, the actually measured integral value IMEP _R is significantly different from the integral value IMEP _th expected to be obtained in the desired cam state. This indicates that the cam corresponding to the switching command has not been switched, and therefore the failure of the variable valve drive mechanism 102 is determined (step 31 → step 32).

On the other hand, when the deviation S is equal to or less than the predetermined value, the actually measured integral value IMEP _R is sufficiently close to the integral value IMEP _th predicted to be obtained in the desired cam state. , This suggests that the cam corresponding to the switching command is actually switched,
Whether the variable valve drive mechanism 102 is normal is determined (step 31).
→ Step 33).

Further, when the normal determination is made, the learning correction coefficient α is updated and set in order to reduce the deviation of the predicted value IMEP _{th from} the actually measured integrated value IMEP _R (step
34), the map data is rewritten based on the updated learning correction coefficient α (step 35). With the configuration that integrates the in-cylinder pressure as in the second example, it is less likely to be affected by noise on the detection signal of the in-cylinder pressure sensor 106, and the pressure increase rate is used as a parameter from the first example. Also enables diagnosis with high noise resistance. That is, since the pressure increase rate of the first embodiment is obtained by sampling the in-cylinder pressure only at two points to obtain the pressure increase rate, if noise is present at the sampling timing, an erroneous diagnosis result will be obtained based on the noise data. Although there is a possibility of providing it, if the configuration in which the in-cylinder pressure is integrated within a predetermined angle range can reduce the influence of the noise component on the final integrated value, it is possible to suppress the occurrence of erroneous diagnosis due to noise generation. It is a thing.

As described above, in order to eliminate the influence of noise, it is preferable to make a diagnosis by using the integrated value of the in-cylinder pressure. However, when simple control is desired, the diagnosis using the pressure increase rate is performed. May be appropriate, and to make the diagnosis simple, it is possible to make the diagnosis based on the in-cylinder pressure level sampled at a specific crank angle position.

The flowchart of FIG. 9 shows a third embodiment in which the diagnosis is carried out using the detected value of the in-cylinder pressure at the specific crank angle position. Also in the third embodiment shown in the flowchart of FIG. 9, the basic diagnostic control flow is the first.
Since this embodiment is common to the embodiment, it will be briefly described below. First,
It is confirmed based on the rotation speed Ne and the engine load Tp (steps 41 and 42) that the in-cylinder pressure P _R detected by the in-cylinder pressure sensor 106 is sampled at a specific crank angle position during the compression stroke ( Steps 43 and 44).

Subsequently, a prediction value P _th for determining whether or not the sampling pressure P _R is a value corresponding to the case where a cam corresponding to the switching command is used is provided for each cam. Obtained by referring to the map (steps 46 and 4)
8) Further, a learning correction coefficient α for adapting the predicted value P _th to the engine state (change with time, variation) is obtained by referring to a map (steps 47, 49).

Then, a value obtained by multiplying the learning correction coefficient α by the absolute value of the deviation between the in-cylinder pressure P _R actually measured at the specific crank angle position and the predicted value P _th is taken as the in-cylinder pressure deviation at the specific crank angle position. S (step 50), and when the deviation S exceeds a predetermined value, the actually measured in-cylinder pressure P _R is against the in-cylinder pressure P _th predicted to be obtained in the desired cam state. Will be very different,
This indicates that the cam corresponding to the switching command has not been switched, and therefore, the failure of the variable valve drive mechanism 102 is determined (step 51 → step 52).

On the other hand, when the deviation S is less than or equal to the predetermined value, the in-cylinder pressure P _R actually measured at the specific crank angle position is
In-cylinder pressure P predicted to be obtained in the desired cam state
_This is sufficiently close to _th , which suggests that the cam corresponding to the switching command is actually switched, and therefore the variable valve drive mechanism 102 is judged to be normal (step 51 → step 53).

Further, when the normal determination is made, the learning correction coefficient α is updated and set so as to reduce the deviation of the predicted value P _{th from} the in-cylinder pressure P _R measured at the specific crank angle position (step 54), and the update is performed. The map data is rewritten based on the set learning correction coefficient α (step 55).
In each of the first, second, and third embodiments described above, the learning correction coefficient α is used to make a diagnosis corresponding to the change and variation of the engine over time.
The correction control may be omitted to simplify the diagnostic control.

When a failure is determined, the driver is warned by a lamp or the like, and when the engine control value such as the ignition timing is switched according to the switching command, the switching of the engine control value is prohibited. However, it is preferable to execute the fail-safe control for fixing the engine control value corresponding to the current cam that cannot be switched.

[0062]

As described above, according to the diagnostic device for the engine valve drive control device according to the invention of claim 1, it is possible to utilize the fact that the change in the intake efficiency due to the switching of the valve opening characteristic can be detected through the in-cylinder pressure. Then, whether or not the cam corresponding to the switching command is actually switched is diagnosed based on whether or not the predicted in-cylinder pressure characteristic corresponding to the switching command is exhibited, so that the working hydraulic pressure is normally supplied. Nevertheless, even if the valve opening characteristic is not switched, it is possible to make a failure determination and provide a highly reliable diagnostic signal. Further, in the diagnostic device according to the second aspect of the present invention, since the characteristic of the in-cylinder pressure is diagnosed as the pressure change rate in the specific section, even if there is an error in the absolute level of the in-cylinder pressure detection value (the Even if there is an offset in the output of the internal pressure sensor), this does not affect the diagnostic accuracy, and the diagnostic accuracy can be maintained.

Further, in the diagnostic device according to the third aspect of the present invention, the characteristic of the in-cylinder pressure is diagnosed as the integrated value of the in-cylinder pressure in the specific section. Therefore, even if noise is added to the in-cylinder pressure detection signal. As a result, there is an effect that it is possible to avoid a great deterioration in diagnostic accuracy. Further, in the diagnostic device according to the invention of claim 4, since the characteristic of the in-cylinder pressure is diagnosed as the in-cylinder pressure at the specific crank angle position, the in-cylinder pressure data required for the diagnosis is minimized. This has the effect of simplifying the control.

In the diagnostic device according to the fifth aspect of the present invention, the predicted characteristic value is learned and corrected based on the detected value of the in-cylinder pressure when the normal determination is made, so that it is possible to cope with the change and variation of the engine over time. Therefore, the diagnostic accuracy can be maintained.

[Brief description of drawings]

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

FIG. 2 is a system configuration diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a variable valve mechanism of the embodiment.

FIG. 4 is a view showing a variable valve mechanism of the embodiment (IV- in FIG. 3;
IV cross section).

FIG. 5 is a view showing a variable valve mechanism of the embodiment (V- in FIG.
V sectional view).

FIG. 6 is a view showing a variable valve mechanism of the embodiment (VI- in FIG. 4;
VI cross section).

FIG. 7 is a flowchart showing diagnostic control of the first embodiment.

FIG. 8 is a flowchart showing diagnosis control of the second embodiment.

FIG. 9 is a flowchart showing diagnostic control of the third embodiment.

FIG. 10 is a diagram showing a diagnosable region in the embodiment.

[Explanation of symbols]

 1 rocker arm 2 free cam follower 3 main rocker shaft 7 lever member 9 return spring 10 spring retainer 21 low speed cam 22 high speed cam 31 actuating plunger 34 hydraulic chamber 51 switching valve 101 engine 102 variable valve drive mechanism 103 control unit 104 air flow meter 105 crank Corner sensor 106 In-cylinder pressure sensor

Claims (5)

[Claims] 1. A valve opening characteristic switching means for switching a valve opening characteristic of an engine to a plurality of preset types, and a switching for outputting a valve opening characteristic switching command to the valve opening characteristic switching means according to an operating condition. An engine valve drive control device comprising: command output means; and an in-cylinder pressure detection means for detecting an in-cylinder pressure of the engine, and a prediction for setting a predicted characteristic value of the in-cylinder pressure in a valve opening characteristic corresponding to the switching command. Comparing the characteristic value setting means, the predicted characteristic value set by the predicted characteristic value setting means, and the detection result of the in-cylinder pressure by the in-cylinder pressure detection means,
A diagnosis in a valve drive control device of an engine, comprising: a switching control diagnosis means for diagnosing whether or not the switching of the valve opening characteristic by the valve opening characteristic switching means is normally performed. apparatus. 2. The predictive characteristic value setting means sets the rate of change of the in-cylinder pressure in a specific section as a predictive characteristic value for each valve opening characteristic, and the switching control diagnosing means sets the predicted in-cylinder pressure change. The failure of the valve opening characteristic switching means is determined when the deviation between the rate and the in-cylinder pressure change rate in the specific section detected by the in-cylinder pressure detection means is more than a predetermined value. Device in the valve drive control device of the engine. 3. The predictive characteristic value setting means sets an integrated value of the in-cylinder pressure in a specific section as a predictive characteristic value for each valve opening characteristic, and the switching control diagnosing means sets the predicted in-cylinder pressure integrated value. And a deviation of the in-cylinder pressure detected by the in-cylinder pressure detecting means from a value integrated in the specific section is a predetermined value or more, a failure of the valve opening characteristic switching means is determined. Item 2. A diagnostic device in an engine valve drive controller according to Item 1. 4. The predictive characteristic value setting means sets an in-cylinder pressure at a specific crank angle position as a predictive characteristic value for each valve opening characteristic, and the switching control diagnosing means sets the predicted specific crank angle position. When the deviation between the in-cylinder pressure and the in-cylinder pressure detected by the in-cylinder pressure detecting means at the specific crank angle position is equal to or more than a predetermined value, the failure of the valve opening characteristic switching means is determined. Item 2. A diagnostic device in an engine valve drive controller according to Item 1. 5. The predicted characteristic value setting means sets based on the in-cylinder pressure characteristic value detected by the in-cylinder pressure detection means when the switching control diagnosis means makes a normal determination of the valve opening characteristic switching means. 5. A diagnostic device for a valve drive control device for an engine according to claim 1, further comprising a predictive characteristic value learning means for learning and correcting the predicted characteristic value.