JP2009299503A - Failure determination device for variable valve mechanism and control device for internal combustion engine equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably determine the degree of a failure occurring in a variable valve mechanism, by a simple and inexpensive method, in a failure determination device for the variable valve mechanism and a control device for an internal combustion engine equipped with the same. <P>SOLUTION: The failure determination device is provided with the variable valve mechanism 10 mechanically changing valve opening characteristics (lift amount, operating angle, and opening/closing timing) of a valve 12 with respect to rotation of a camshaft 13. The variable valve mechanism 10 is provided with: a control shaft 16 driven by a motor 56; and a variable mechanism 20 interposed between a drive cam 14 and the valve 12, and changing the valve opening characteristics of the valve 12 according to a control position of the control shaft 16. The failure determination device determines the degree of failure occurring in the variable valve mechanism 10, based on combination of drive current variation of the motor 56 with rotational fluctuation of a crankshaft. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a failure determination device for a variable valve mechanism and a control device for an internal combustion engine including the same.

  Conventionally, for example, Patent Document 1 discloses a failure diagnosis device for a variable valve mechanism. This conventional variable valve mechanism is a mechanism that allows the valve opening characteristics of a valve to be changed by controlling a control shaft in the axial direction by an actuator. In the above conventional failure diagnosis apparatus, when the control amount of the actuator is out of the normal range, it is determined that the variable valve mechanism is in failure.

JP 2006-63846 A Japanese Utility Model Publication No. 63-31212 JP 10-31802 A Japanese Patent Laid-Open No. 11-311589 JP 2004-48875 A

  According to the conventional failure diagnosis apparatus, it is possible to determine whether or not a failure has occurred in the variable valve mechanism. However, the degree of the failure cannot be determined.

  The present invention has been made in order to solve the above-described problems, and includes a variable valve mechanism failure determination device that can satisfactorily determine the degree of failure that has occurred in a variable valve mechanism by an inexpensive and simple method, and An object of the present invention is to provide a control device for an internal combustion engine including the same.

A first invention is a failure determination device for a variable valve mechanism,
A failure determination device for a variable valve mechanism capable of mechanically changing a valve opening characteristic with respect to rotation of a camshaft,
A control shaft driven by a motor;
A variable mechanism that is interposed between the drive cam and the valve and changes a valve opening characteristic of the valve according to a control position of the control shaft;
Current change acquisition means for acquiring a drive current change of the motor;
Rotation fluctuation acquisition means for acquiring crankshaft rotation fluctuation;
A failure degree determination means for determining a degree of failure that has occurred in the variable valve mechanism based on a combination of a change in the driving current of the motor and a rotation fluctuation of the crankshaft;
It is characterized by providing.

The second invention is the first invention, wherein
The failure degree determining means determines that the degree of failure is severe when a change in at least one of a change in driving current of the motor and a change in rotation of the crankshaft is large.

A third aspect of the invention is a control device for an internal combustion engine comprising the variable valve mechanism failure determination device according to the first or second aspect of the invention.
When the degree of failure is determined to be minor by the failure degree determination means, the internal combustion engine is less changed with respect to normal control than when the degree of failure is determined to be severe. It is further characterized by further comprising a evacuation operation executing means at the time of a minor failure for executing the evacuation operation.

A fourth aspect of the invention is a control device for an internal combustion engine including the variable valve mechanism failure determination apparatus according to the first or second aspect of the invention,
When the degree of failure is determined to be severe by the failure degree determination means, the internal combustion engine is more greatly changed than normal when compared to a case where the degree of failure is determined to be mild. Evacuation operation execution means at the time of a serious failure to execute
Warning execution means for warning the failure when the failure degree is determined to be severe by the failure degree determination means;
Is further provided.

  According to the first aspect of the present invention, the degree of failure occurring in the variable valve mechanism is utilized by means (current change acquisition means and rotation fluctuation acquisition means) that are generally provided in a system having a variable valve mechanism. Good determination can be made by an inexpensive and simple method.

  As the degree of failure (damage) of the variable valve mechanism increases, the motor drive current increases and the rotational fluctuation of the crankshaft also increases. For this reason, according to the second invention, it is possible to accurately determine whether or not a serious failure has occurred in the variable valve mechanism.

  According to the third or fourth aspect of the invention, the evacuation operation is performed in a manner in which the magnitude of change with respect to normal control differs depending on the degree of failure occurring in the variable valve mechanism. Thereby, it is possible to prevent the subsequent travel as much as possible, and a retreat operation (retreat travel) with less deterioration in fuel consumption is possible.

  According to the fourth aspect of the present invention, when a serious failure has occurred in the variable valve mechanism, it is possible to notify the vehicle driver of the situation and prompt repair of the failure location.

Embodiment 1 FIG.
[Configuration of variable valve mechanism]
FIG. 1 is a sectional side view showing a variable valve mechanism 10 according to Embodiment 1 of the present invention. Hereinafter, the variable valve mechanism 10 shown in FIG. 1 will be described as driving the intake valve 12 of the internal combustion engine, but the present invention is also applicable to a variable valve mechanism that drives the exhaust valve.

  The variable valve mechanism 10 includes a drive cam 14 provided on a camshaft 13 that is rotationally driven by a crankshaft of an internal combustion engine. Further, the variable valve mechanism 10 includes a control shaft 16 arranged in parallel with the cam shaft 13 and a control shaft driving device 18 (see FIG. 2) capable of rotating the control shaft 16 within a predetermined angle range. (To be described later).

  Further, the variable valve mechanism 10 includes a variable mechanism 20 that changes the valve opening characteristics (lift amount, operating angle, opening / closing timing, etc.) of the valve 12 in accordance with the rotational position of the control shaft 16. As will be described below, the variable mechanism 20 includes a swing arm (swing member) 22, a slider roller 26, an intermediate arm 28, a cam roller 30, and a control member (control arm) 32 as main components. Yes.

  The swing arm 22 is installed so as to be swingable about the control shaft 16. A slider surface 24 is formed on the swing arm 22 on the side facing the drive cam 14. A slider roller 26 is disposed between the swing arm 22 and the drive cam 14.

  The slider roller 26 is rotatably supported at the tip of the intermediate arm 28. A cam roller 30 that contacts the drive cam 14 is disposed at the tip of the intermediate arm 28. The cam roller 30 is disposed coaxially with the slider roller 26.

  The base end portion of the intermediate arm 28 is connected to the control member 32 by a connecting shaft 34 so as to be rotatable. The control member 32 is a member that rotates integrally with the control shaft 16. Therefore, when the control shaft 16 is rotated, the displacement is transmitted through the control member 32 and the intermediate arm 28, and the slider roller 26 moves.

  Specifically, when the control shaft 16 is rotated clockwise from the state shown in FIG. 1, the slider roller 26 and the cam roller 30 are moved away from the swing center of the swing arm 22 (that is, the center of the control shaft 16). It moves to the tip side of the moving arm 22. Then, when the control shaft 16 is rotated counterclockwise from the state where the slider roller 26 and the cam roller 30 are on the distal end side of the swing arm 22, the slider roller 26 and the cam roller 30 are pulled by the intermediate arm 28 and controlled. It approaches the center of the axis 16. FIG. 1 shows a state where the positions of the slider roller 26 and the cam roller 30 are close to the center of the control shaft 16.

  The slider surface 24 has a curved surface (for example, an arc surface) in which the distance from the center of the cam shaft 13 gradually increases as it goes to the tip end side of the swing arm 22. A swing cam surface 36 is formed on the side of the swing arm 22 opposite to the slider surface 24.

  The swing arm 22 is urged clockwise in FIG. 1 by a lost motion spring (not shown). The oscillating arm 22 is pressed against the slider roller 26 and the cam roller 30 is pressed against the drive cam 14 by the biasing force of the lost motion spring.

  The variable valve mechanism 10 further includes a rocker arm 38 for pressing the valve shaft of the intake valve 12 in the lift direction. The rocker arm 38 is disposed below the swing arm 22 in FIG. A rocker roller 40 is rotatably attached to an intermediate portion of the rocker arm 38. The rocker roller 40 is in contact with the swing cam surface 36. One end of the rocker arm 38 is in contact with the valve shaft end of the intake valve 12, and the other end of the rocker arm 38 is supported by a hydraulic lash adjuster 42.

  The intake valve 12 is urged in a closing direction, that is, a direction in which the rocker arm 38 is pushed up by a valve spring (not shown). The rocker roller 40 is pressed against the swing cam surface 36 of the swing arm 22 by this urging force and the hydraulic lash adjuster 42.

  Further, the variable mechanism 20 includes a working angle adjusting mechanism 44 that can adjust the working angle of the intake valve 12 for each cylinder so that the variation in the working angle of the intake valve 12 between the cylinders can be corrected. More specifically, as shown in FIG. 1, the working angle adjustment mechanism 44 includes a control pin 46, an adjustment pin 48, an adjustment shim 50, a bolt 52, and a nut 54. The control pin 46 is fixed to the control shaft 16, and the adjustment pin 48 is rotatably held by the control member 32. The adjustment shim 50 is a member that is sandwiched between the control pin 46 and the adjustment pin 48.

  In such a working angle adjusting mechanism 44, the mounting angle of the control member 32 with respect to the control shaft 16 can be finely adjusted by exchanging the adjustment shim 50 with a different thickness. Can be adjusted.

  In the variable valve mechanism 10 configured as described above, when the drive cam 14 rotates, the cam lift of the drive cam 14 is transmitted to the swing arm 22 via the cam roller 30 and the slider roller 26, so that the swing arm 22. Swings.

  In the state shown in FIG. 1, that is, in the state where the slider roller 26 is close to the center of the control shaft 16, the cam lift of the drive cam 14 is transmitted to the swing arm 22 at a position close to the swing center of the swing arm 22. Will be. For this reason, the swing range (swing width) of the swing arm 22 is increased. As a result, the operating angle (and lift amount) of the intake valve 12 increases.

  Conversely, when the slider roller 26 is at a position far from the center of the control shaft 16, the cam lift of the drive cam 14 is transmitted to the swing arm 22 at a position far from the swing center of the swing arm 22. . For this reason, the swing range (swing width) of the swing arm 22 is reduced. As a result, the operating angle (and lift amount) of the intake valve 12 is reduced.

  Thus, in the variable valve mechanism 10, the operating angle of the intake valve 12 can be continuously changed by rotating the control shaft 16 and moving the slider roller 26. That is, as the rotational position of the control shaft 16 is displaced clockwise in FIG. 1, the operating angle of the intake valve 12 can be reduced. Conversely, the rotational position of the control shaft 16 is counterclockwise in FIG. The greater the displacement is, the larger the operating angle of the intake valve 12 can be.

[Configuration of control axis drive unit]
FIG. 2 is a diagram for explaining the configuration of the control shaft drive device 18 according to the first embodiment of the present invention. More specifically, FIG. 2 (A) is a view of the variable valve mechanism 10 as viewed from the axial direction of the control shaft 16, and FIG. 2 (B) is a diagram of the variable valve mechanism 10 shown in FIG. 2 (A). It is the figure seen from the A arrow direction shown in the inside.

  Here, the variable valve mechanism 10 according to the present embodiment is combined with an in-line four-cylinder internal combustion engine, and has four variable mechanisms 20 provided corresponding to individual cylinders. . Further, the control shaft 16 described above is arranged so as to penetrate the four cylinders through all the variable mechanisms 20, and is held by a cylinder head of the internal combustion engine by a bearing (not shown).

  The configuration of the control shaft driving device 18 for driving the control shaft 16 is not particularly limited. For example, as shown in FIG. 2, the motor 56 is provided as a drive source, and the torque of the motor 56 is rotated by the control shaft 16. This can be realized by providing a worm gear mechanism that converts force.

  More specifically, as shown in FIG. 2, a worm gear 58 is fixed to the output shaft of the motor 56. A worm wheel 60 is engaged with the worm gear 58. A reduction gear 62 is fixed to the rotation shaft of the worm wheel 60. The reduction gear 62 is engaged with a reduction gear 64 fixed to one end side of the control shaft 16. With such a configuration, the rotation of the motor 56 is transmitted to the control shaft 16 after being decelerated at a predetermined reduction ratio.

  A position sensor 66 such as a potentiometer for detecting the rotational position of the motor 56 (the rotational position of the control shaft 16) is attached to one end of the control shaft 16. Further, the system shown in FIG. 2 includes an ECU (Electronic Control Unit) 68. The ECU 68 is connected to various sensors such as a crank angle sensor 70 for acquiring the rotational fluctuation of the crankshaft of the internal combustion engine, and various actuators such as a motor 56. Further, the ECU 68 is configured to be able to acquire the drive current of the motor 56.

  According to the control shaft drive device 18 configured as described above, the rotational position and the rotation amount of the motor 56 are controlled in response to the drive signal from the ECU 68, thereby controlling the rotational position of the control shaft 16. Can do.

[Failure judgment method for variable valve mechanism]
As described above, in the variable valve mechanism 10, the operating angle and lift amount of the valve 12 are changed by changing the rotational position of the control shaft 16 by the control shaft driving device 18. Each component of the variable valve mechanism 10 (specifically, the variable mechanism 20 (the swing arm 22, the slider roller 26, the intermediate arm 28, the cam roller 30, the control member 32, and the working angle adjusting mechanism 44). When wear or deformation with time progresses at each contact site and rattling occurs between the components, the operating angle of the valve 12 with respect to the adjustment of the control shaft 16 is distorted.

  More specifically, when rattling occurs between the above components, the cam roller 30 is pulled away from the control shaft 16 by the reaction force from the valve spring during the valve lift, and as a result, The working angle and lift amount of the valve 12 are reduced.

  Further, if rattling occurs between the above components, the force acting on the cam roller 30 when the valve 12 is lifted fluctuates, so that the control shaft 16 receives a fluctuating load, and the working angle and lift amount of the valve 12 are reduced. Will fluctuate. Further, the fluctuation of the torque applied to the control shaft 16 becomes large. As a result, the drive current of the motor 56 for driving the control shaft 16 increases. Further, the higher the degree of damage to the variable valve mechanism 10, the greater the driving current of the motor 56.

  On the other hand, when an abnormality due to damage to the variable valve mechanism 10 occurs only in a certain cylinder, the intake air amount decreases in the abnormality occurrence cylinder, and torque fluctuation of the internal combustion engine and crankshaft rotation fluctuation occur. To do. In this case, the higher the degree of damage to the variable valve mechanism 10, the greater the crank shaft rotation fluctuation.

  Therefore, in this embodiment, when determining the degree of failure that has occurred in the variable valve mechanism 10, first, the failure point in the variable valve mechanism 10 is not the control shaft drive device 18, but a mechanism portion (variable mechanism 20). This is specified by the following method. In addition, the degree of failure (damage) occurring in the variable valve mechanism 10 is determined based on the magnitude of the drive current change of the control shaft 16 by the motor 56 and the magnitude of the crank shaft rotation fluctuation.

  Further, in the present embodiment, for the retreat travel in which the vehicle on which the variable valve mechanism 10 is mounted is moved to a safe place in a manner corresponding to the degree of failure of the variable valve mechanism 10 determined by the above method. The internal combustion engine is evacuated. Further, when it is determined that the degree of failure is serious, an appropriate evacuation operation is performed according to the degree of failure at the time of the determination, and the presence of the failure is warned.

FIG. 3 is a flowchart of a routine executed by the ECU 68 in the first embodiment to realize the above function. Note that this routine is periodically executed at predetermined time intervals.
In the routine shown in FIG. 3, first, it is determined whether or not a failure has occurred in the control shaft driving device 18 (step 100).

  FIG. 4 is a diagram showing how the control shaft 16 responds when the control shaft driving device 18 is driven based on a command from the ECU 68. More specifically, FIG. 4A shows the waveform of the command value of the ECU 68 to the control shaft driving device 18, and FIG. 4B shows the waveform of the position sensor 66 when the command from the ECU 68 is received. Respectively.

  As shown in FIG. 4A, when a drive command is issued from the ECU 68 to the motor 56 of the control shaft drive device 18, the driving force of the motor 56 causes the worm gear 58, the worm wheel 60, the reduction gear 62, and the reduction gear 64 to move. To the control shaft 16 and the control shaft 16 starts to rotate.

  In this step 100, the command value of the ECU 68 to the control shaft driving device 18 is compared with the output signal of the position sensor 66 attached to the control shaft 16. More specifically, it is determined whether or not the response time of the control shaft 16 with respect to the command value is longer than the normal response time.

  In the case where there is damage such as rattling between the gear and the shaft in the control shaft driving device 18, the response time of the control shaft 16 to the command value of the ECU 68 becomes longer than normal. Therefore, according to the determination in step 100, it is possible to confirm whether or not damage (failure) such as rattling has occurred in the control shaft driving device 18.

  If it is determined in step 100 that no failure has occurred in the control shaft drive device 18, then the current drive current of the motor 56 is compared with the normal drive current (step 102). Then, it is determined whether or not the current drive current is higher than the normal drive current (step 104).

  As a result, if it is determined that the current drive current of the motor 56 is greater than the normal drive current, then the current rotational fluctuation of the crankshaft is compared with the normal rotational fluctuation. (Step 106). Then, it is determined whether or not the current rotational fluctuation is greater than the normal rotational fluctuation (step 108).

  As a result, if it is determined that the current rotational fluctuation of the crankshaft is larger than the normal rotational fluctuation, then the amount of increase in the drive current of the motor 56 and the amount of increase in the rotational fluctuation of the crankshaft Are compared with a predetermined threshold value (step 110). In order to determine the degree of damage (failure) of the variable valve mechanism 10, the ECU 68 determines two threshold values (first threshold value and first threshold value) for each of the drive current change of the motor 56 and the change of the crank shaft rotation fluctuation. 2 threshold) is stored.

  The first threshold value is a threshold value for determining whether or not a failure has occurred in the variable valve mechanism 10. Further, the second threshold value is set to a value larger than the first threshold value, and when the variable valve mechanism 10 has a failure, the degree of the failure is minor, or It is a threshold value for determining whether or not the damage may lead to a serious failure. These threshold values are obtained in advance based on the test results in the respective damaged states.

  Next, the damage level (degree of failure) of the variable valve mechanism 10 is determined (step 112). Specifically, based on the first threshold value and the second threshold value, when both the change in driving current of the motor 56 and the change in rotation fluctuation of the crankshaft have not reached the first threshold value, the variable valve mechanism 10 is determined to be normal.

  On the other hand, if at least one of the change in the driving current of the motor 56 and the change in the rotation fluctuation of the crankshaft exceeds the first threshold but does not reach the second threshold, the variable valve mechanism 10 Is determined to have minor damage (for example, an increase in clearance due to wear of the pin or pin receiving portion of the swinging part), that is, the degree of failure occurring in the variable valve mechanism 10 is determined to be minor. Is done.

Further, when at least one of the change in the driving current of the motor 56 and the change in the rotation fluctuation of the crankshaft exceeds the second threshold value, there is a possibility that the variable valve mechanism 10 may lead to a serious failure. Damage (for example, a situation where the adjustment shim 50 is loose, or the slider roller 26 and the cam roller 30 are coaxially arranged so as to be rotationally supported by the intermediate arm 28, or the backlash is increased, or It is determined that there is damage that causes a situation in which friction is increased due to the seizure of the cam roller 30 or the slider roller 26, that is, the degree of failure that has occurred in the variable valve mechanism 10 is determined to be severe.
Here, the serious failure refers to a failure that causes a situation in which the driving of the valve 12 becomes impossible, such as dropping of the pin, detaching of the intermediate arm 28, or dropping of the slider roller 26 or the cam roller 30.

  In the routine shown in FIG. 3, next, correction of the control of the valve opening characteristic of the valve 12 when performing the evacuation operation of the internal combustion engine is performed in accordance with the degree of failure determined in step 112 (step 114). ).

  Specifically, when it is determined that the degree of failure is minor, the operating angle and lift amount of the valve 12 are set to the normal target until the crankshaft rotational fluctuation falls within a predetermined allowable range. Enlarged than the value. In this case, the adjustment of the intake air amount is assisted by the throttle valve only in a necessary operation region. As a result, the difference in the intake air amount between the cylinders is reduced, so that the rotational fluctuation of the crankshaft can be reduced satisfactorily.

  When it is determined that the degree of failure is severe, the operating angle and lift amount of the valve 12 are fixed at the maximum operating angle and maximum lift amount, and the intake air amount is controlled entirely by the throttle valve. Done in That is, when it is determined that the degree of failure is severe, the evacuation operation is performed in a manner in which the change in the valve control during normal operation is larger than in the above case where the degree of failure is determined to be mild. Will come to be.

  Next, it is determined whether or not the degree of failure determined in step 112 is severe (step 116). If it is determined that the degree of failure is severe, the current failure is further determined. Is stored in the ECU 68 and a warning lamp is turned on (step 118). This prompts the driver to repair the failed part.

  According to the routine shown in FIG. 3 described above, the failure of the variable valve mechanism 10 based on the combination of the change in the driving current of the motor 56 with respect to the normal time and the change in the rotation fluctuation of the crankshaft with respect to the normal time. The degree can be specified well.

  More specifically, a position sensor (in this embodiment, a position sensor provided in a motor, a control shaft, or a shaft interposed between them (in this embodiment, a shaft to which the worm wheel 60 is fixed) corresponds. 66), the degree of damage to the variable valve mechanism that cannot be detected only by monitoring the position of the control shaft drive system can be determined by an inexpensive and simple method.

  Further, according to the above routine, it is possible to detect the failure of the variable valve mechanism 10 used for suppressing exhaust emission such as suppression of THC emission during cold start including the extent thereof, and to the extent of the failure. Since appropriate evacuation can be performed, it is possible to compensate for exhaust emissions.

  Further, according to the above routine, it can be seen that it is not a failure of the control shaft drive device 18, so that it is not necessary to check the control shaft drive device 18 at the time of repair. Moreover, the serious damage of the variable valve mechanism 10 can be prevented.

  In addition, when fail mode control is performed uniformly regardless of the degree of failure, there is a concern that the degree of failure is mild and fuel consumption may deteriorate in situations where the vehicle can be driven normally. The On the other hand, in the above routine, the retreat operation is performed in a manner in which the magnitude of the change with respect to the normal control differs depending on the degree of the failure that has occurred in the variable valve mechanism 10. Thereby, it is possible to prevent the subsequent travel as much as possible, and a retreat operation (retreat travel) with less deterioration in fuel consumption is possible.

  By the way, in Embodiment 1 mentioned above, the variable valve mechanism 10 which has the variable mechanism 20 which changes the valve opening characteristic of the valve 12 according to the rotational position of the control shaft 16 rotationally driven by the motor 56 is taken as an example. I gave an explanation. However, in the present invention, the variable valve mechanism having a variable mechanism that changes the valve opening characteristic according to the control position of the control shaft is not limited to such a configuration. That is, for example, the control shaft may be driven in the axial direction by a motor.

In the first embodiment described above, the ECU 68 executes the processes in steps 102 and 104, so that the “current change acquisition means” in the first invention executes the processes in steps 106 and 108. As a result, the “rotation fluctuation acquisition means” in the first invention realizes the “failure degree determination means” in the first invention by executing the processing of steps 110 and 112 described above.
Further, the ECU 68 executes the processing of step 114, thereby realizing the “slight operation failure evacuation operation execution means” according to the third aspect of the present invention.
Further, when the ECU 68 executes the process of step 114, the “severe failure evacuation operation execution means” in the fourth invention executes the processes of steps 116 and 118, so that the ECU 68 performs the process of the fourth invention. “Alarm execution means” are realized.

It is a cross-sectional side view which shows the variable valve mechanism of Embodiment 1 of this invention. It is a figure for demonstrating the structure of the control-axis drive device in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure showing the mode of the response of a control axis at the time of driving a control axis drive based on the command from ECU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Variable valve mechanism 12 Valve 13 Cam shaft 14 Drive cam 16 Control shaft 18 Control shaft drive device 20 Variable mechanism 22 Swing arm 24 Slider surface 26 Slider roller 28 Intermediate arm 30 Cam roller 32 Control member 36 Swing cam surface 38 Rocker arm 40 Rocker roller 42 Hydraulic lash adjuster 44 Working angle adjustment mechanism 46 Control pin 48 Adjustment pin 50 Adjustment shim 56 Motor 58 Worm gear 60 Worm wheel 62, 64 Reduction gear 66 Position sensor 68 ECU (Electronic Control Unit)
70 Crank angle sensor

Claims (4)

A failure determination device for a variable valve mechanism capable of mechanically changing a valve opening characteristic with respect to rotation of a camshaft,
A control shaft driven by a motor;
A variable mechanism that is interposed between the drive cam and the valve and changes a valve opening characteristic of the valve according to a control position of the control shaft;
Current change acquisition means for acquiring a drive current change of the motor;
Rotation fluctuation acquisition means for acquiring crankshaft rotation fluctuation;
A failure degree determination means for determining a degree of failure that has occurred in the variable valve mechanism based on a combination of a change in the driving current of the motor and a rotation fluctuation of the crankshaft;
A failure determination device for a variable valve mechanism, comprising:   The failure degree determination means determines that the degree of failure is severe when at least one of a change in driving current of the motor and a change in rotation of the crankshaft is large. The failure determination device for a variable valve mechanism according to claim 1.   When the degree of failure is determined to be minor by the failure degree determination means, the internal combustion engine is less changed with respect to normal control than when the degree of failure is determined to be severe. 3. The control device for an internal combustion engine comprising the variable valve mechanism failure determination device according to claim 1 or 2, further comprising a minor failure time evacuation operation execution means for executing the evacuation operation. When the degree of failure is determined to be severe by the failure degree determination means, the internal combustion engine is more greatly changed than normal when compared to a case where the degree of failure is determined to be mild. Evacuation operation execution means at the time of a serious failure to execute
Warning execution means for warning the failure when the failure degree is determined to be severe by the failure degree determination means;
The control device for an internal combustion engine comprising the variable valve mechanism failure determination device according to claim 1, further comprising:

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