WO2012077230A1

WO2012077230A1 - Abnormality determination device for internal combustion engine

Info

Publication number: WO2012077230A1
Application number: PCT/JP2010/072244
Authority: WO
Inventors: 貴志錦織; 中川　徳久
Original assignee: トヨタ自動車株式会社
Priority date: 2010-12-10
Filing date: 2010-12-10
Publication date: 2012-06-14

Abstract

Provided is an abnormality determination device for an internal combustion engine, which is capable of determining the abnormality of the operation of a variable valve lift mechanism by a simple configuration. An abnormality determination device is provided with a variable valve lift mechanism (32) which comprises a first lift cam (56) and a second lift cam (64) by which the exhaust valve closing timing (EVC) is more advanced toward BTDC than by the first lift cam (56), and can variably set the lift characteristics of an exhaust valve (30) by switching between the lift cams, and a pressure sensor (44) which acquires intake pipe pressure, and when the switching from the first lift cam (56) to the second lift cam (64) is performed by driving the variable valve lift mechanism (32), determines the abnormality of the operation of the variable valve lift mechanism (32) on the basis of the change of the intake pipe pressure when an intake valve (28) is opened (IVO) immediately after the operation of the switching. More preferably, the abnormality of the operation of the variable valve lift mechanism (32) is determined during fuel cut.

Description

Abnormality determination device for internal combustion engine

The present invention relates to an abnormality determination device for an internal combustion engine, and more particularly to an abnormality determination device for an internal combustion engine that determines the presence or absence of an abnormality in a variable valve mechanism of an exhaust valve.

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-1000048, there is known an apparatus that detects an abnormal operation of a variable valve lift mechanism using a lift sensor that detects lift amounts of intake valves and exhaust valves. ing. Specifically, in this apparatus, abnormal operation of the intake valve and the exhaust valve in an engine with a cylinder deactivation mechanism is directly detected by a lift sensor, and an appropriate process is executed after determining which abnormal state it is. I am going to do that.

Japanese Unexamined Patent Publication No. 2004-1000048 Japanese Unexamined Patent Publication No. 2005-172593 Japanese Unexamined Patent Publication No. 2004-1000048

However, in the configuration in which the abnormal operation of the variable valve lift mechanism is detected by the lift sensor as in the conventional technique described above, it is necessary to determine the failure of the lift sensor itself. For this reason, it has been desired to construct a system that uses an existing configuration to determine an abnormal operation of the variable valve lift mechanism.

The present invention has been made to solve the above-described problems, and an object thereof is to provide an abnormality determination device for an internal combustion engine that can determine an operation abnormality of a variable valve lift mechanism with a simple configuration. .

In order to achieve the above object, a first invention is an abnormality determination device for an internal combustion engine,
A variable valve lift mechanism capable of variably setting the lift characteristic of the exhaust valve of the internal combustion engine;
Intake pipe pressure acquisition means for acquiring the intake pipe pressure of the internal combustion engine;
When the variable valve lift mechanism is driven to advance the closing timing of the exhaust valve in the BTDC direction, the variable valve lift is based on the change in the intake pipe pressure when the intake valve is opened immediately after the operation. An abnormality determining means for determining an abnormal operation of the mechanism;
It is characterized by having.

According to a second invention, in the first invention,
The variable valve lift mechanism is
A first lift cam;
A second lift cam at which the closing timing of the exhaust valve is advanced in the BTDC direction relative to the first lift cam;
A switching mechanism for switching a lift cam for operating the exhaust valve between the first lift cam and the second lift cam;
The abnormality determining means determines an abnormality related to a switching operation from the first lift cam to the second lift cam by the switching mechanism.

According to a third invention, in the second invention,
The opening timing of the intake valve is in the vicinity of the intake TDC,
The closing timing of the exhaust valve by the second lift cam is a timing advanced from the intake TDC in the BTDC direction.

4th invention is 2nd or 3rd invention,
A lift amount of the exhaust valve by the second lift cam is smaller than that of the first lift cam.

According to a fifth invention, in any one of the first to fourth inventions,
An intake valve phase variable mechanism capable of variably setting the phase of the intake valve;
Valve control means for driving the intake valve phase variable mechanism to vary the opening timing of the intake valve to the vicinity of the intake TDC when the abnormality determining means determines an abnormal operation of the variable valve lift mechanism;
Is further provided.

A sixth invention is any one of the first to fifth inventions,
An exhaust valve phase variable mechanism capable of variably setting the phase of the exhaust valve;
A second valve control means for driving the exhaust valve phase variable mechanism to advance the closing timing of the exhaust valve in the BTDC direction when the abnormality determination means determines an operation abnormality of the variable valve lift mechanism;
Is further provided.

A seventh invention is the invention according to any one of the first to sixth inventions,
The abnormality determining means is characterized by determining an operation abnormality of the variable valve lift mechanism during fuel cut of the internal combustion engine.

According to the first invention, an abnormal operation of the variable valve lift mechanism provided in the exhaust valve is determined based on a change in the intake pipe pressure when the intake valve is opened (IVO). When the variable valve lift mechanism is driven to advance the exhaust valve closing timing (EVC) in the BTDC direction, the exhaust blowback to the intake system at IVO increases. The influence of the blowback is superimposed on the intake pipe pressure at the IVO. For this reason, according to the present invention, based on the intake pipe pressure in the IVO immediately after the operation of the variable valve lift mechanism, the operation abnormality of the variable valve lift mechanism can be determined with high accuracy.

According to the second invention, when the switching operation from the first lift cam to the second lift cam by the switching mechanism is normally performed, the EVC is advanced in the BTDC direction, so that the intake system at the IVO is moved to the intake system. Exhaust blowback increases. Therefore, according to the present invention, an abnormality related to the switching operation of the variable valve lift mechanism can be determined with high accuracy based on the intake pipe pressure at the IVO immediately after the switching operation of the lift cam.

According to the third invention, when the lift cam of the exhaust valve is switched from the first lift cam to the second lift cam, a negative valve overlap occurs. For this reason, according to the present invention, the exhaust blow-back to the intake system can be increased in the IVO immediately after the switching operation by the variable valve lift mechanism, so that the accuracy of the abnormality determination can be effectively increased.

According to the fourth invention, the lift amount of the exhaust valve by the second lift cam is configured to be smaller than that of the first lift cam. Therefore, according to the present invention, when the variable valve lift mechanism is driven to switch from the first lift cam to the second lift cam, the exhaust gas blowback to the intake system at the IVO immediately thereafter can be increased. Therefore, the accuracy of abnormality determination can be increased effectively.

According to the fifth aspect of the invention, when determining whether or not the variable valve lift mechanism is operating abnormally, the intake valve phase variable mechanism is driven to vary the IVO in the vicinity of the intake TDC. For this reason, according to the present invention, it is possible to effectively suppress a situation in which an overlap with the exhaust valve occurs during abnormality determination.

According to the sixth aspect of the invention, when determining whether or not there is an abnormal operation of the variable valve lift mechanism, the exhaust valve phase variable mechanism is driven to advance the EVC in the BTDC direction. For this reason, according to the present invention, it is possible to effectively suppress the occurrence of an overlap with the intake valve at the time of abnormality determination, and to effectively suppress the decrease in torque and the generation of abnormal noise from the intake manifold. it can.

According to the seventh aspect, during the fuel cut of the internal combustion engine, it is determined whether there is an abnormal operation of the variable valve lift mechanism. Therefore, according to the present invention, it is possible to determine whether or not there is an abnormal operation of the variable valve lift mechanism without affecting the torque request of the driver.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. 4 is a cross-sectional view of a first rocker arm 46 and

second rocker arms

48R and 48L provided in the variable valve lift mechanism 32. FIG. 4 is a side view of the first rocker arm 46. FIG. It is a side view of the 2nd rocker arm 48R. It is a side view of the 2nd rocker arm 48L. 4 is a cross-sectional view of a first rocker arm 46 and

second rocker arms

48R and 48L provided in the variable valve lift mechanism 32. FIG. FIG. 5 is a PV diagram showing a change in in-cylinder pressure P with respect to a stroke volume V in the cylinder. It is a figure which compares the lift profile of the 1st lift cam 56 and the 2nd lift cam 64. FIG. It is a figure which shows the change of the intake pipe pressure at the time of implementing switching operation by a variable valve lift mechanism. It is a figure for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a figure which shows an example of the control which varies the valve timing phase of an intake valve. It is a figure which shows an example of the control which varies the valve timing phase of an exhaust valve.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. A piston 12 is provided in each cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in each cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

Near the inlet of the intake passage 16, an air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided. A throttle valve 22 is provided downstream of the air flow meter 20. Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 24 for injecting fuel into the intake port and an ignition plug 26 for igniting the air-fuel mixture in the combustion chamber 14.

Each cylinder of the internal combustion engine 10 is provided with two intake valves 28 and two exhaust valves 30. The internal combustion engine 10 also includes a variable valve lift mechanism 32 that variably controls the lift characteristics of the exhaust valve 30. The configuration and function of the variable valve lift mechanism 32 will be described later in detail.

Further, a crank angle sensor 38 for detecting the rotation angle (crank angle) of the crankshaft 36 and the engine speed is disposed in the vicinity of the crankshaft 36 of the internal combustion engine 10. Further, a surge tank 42 provided in the middle of the intake passage 16 is provided with a pressure sensor 44 for detecting the intake pipe pressure.

The system of the present embodiment includes an ECU (Electronic Control Unit) 40. Various sensors for controlling the internal combustion engine 10 such as the crank angle sensor 38 and the pressure sensor 44 described above are electrically connected to the ECU 40. The ECU 40 is electrically connected to various actuators such as the fuel injection valve 24 described above. The ECU 40 controls the operating state of the internal combustion engine 10 based on those sensor outputs.

[Configuration of Variable Valve Operating Apparatus of Embodiment 1]
Next, with reference to FIG. 2 thru | or FIG. 6, the structure and operation | movement of the variable valve lift mechanism 32 of this embodiment are demonstrated. FIG. 2 is a cross-sectional view of the first rocker arm 46 and the

second rocker arms

48R and 48L provided in the variable valve lift mechanism 32. As shown in FIG. 2, the variable valve lift mechanism 32 includes a first rocker arm 46 and a pair of

second rocker arms

48R and 48L disposed on both sides thereof. These rocker arms 46, 48 R, 48 L can swing around a common rocker shaft 50. The rocker shaft 50 is supported by the cylinder head of the internal combustion engine 10 via a pair of hydraulic lash adjusters 52.

FIG. 3 is a side view of the first rocker arm 46. As shown in FIG. 3, the variable valve lift mechanism 32 has a camshaft 54. The camshaft 54 is connected to the crankshaft 36 via a timing chain or the like, and rotates at a half speed of the crankshaft 36. The cam shaft 54 includes a first lift cam 56 for opening and closing one exhaust valve 30 (front). On the other hand, the first rocker arm 46 is provided with a first roller 58. The first rocker arm 46 is biased counterclockwise in FIG. 3 by a torsion coil spring 60. The first roller 58 is pressed against the first lift cam 56 by this urging force. With such a configuration, the first rocker arm 46 swings as the first lift cam 56 rotates.

FIG. 4 is a side view of the second rocker arm 48R. As shown in FIG. 4, the movable end of the second rocker arm 48R is in contact with the end of the valve stem of one exhaust valve 30 (front). The exhaust valve 30 (front) is biased in the valve closing direction by a valve spring 62. The cam shaft 54 includes a second lift cam 64 at a position corresponding to the second rocker arm 48R. The second lift cam 64 is a cam that opens and closes the exhaust valve 30 (front) via the second rocker arm 48R. The profile of the second lift cam 64 is such that the closing timing of the exhaust valve 30 (rear) advances from the intake TDC toward BTDC as compared with the closing timing and lift amount of the exhaust valve 30 (front) driven by the first lift cam 56. It is set so as to have a small lift amount on the corner side. A second roller 66R is provided on the second rocker arm 48R. The outer diameter of the roller 66 R is equal to the outer diameter of the first roller 58 provided on the first rocker arm 46. The distance between the center of the rocker shaft 50 and the center of the second roller 66 R is equal to the distance between the center of the rocker shaft 50 and the center of the first roller 58. When the exhaust valve 30 (front) is closed, the second roller 66R is in contact with the second lift cam 64.

FIG. 5 is a side view of the second rocker arm 48L. As shown in FIG. 5, the movable end of the second rocker arm 48L is in contact with the end of the valve stem of one exhaust valve 30 (rear). The exhaust valve 30 (rear) is urged in the valve closing direction by a valve spring 62. The cam shaft 54 includes a third lift cam 68 at a position corresponding to the second rocker arm 48L. The third lift cam 68 is a cam that opens and closes the exhaust valve 30 (rear) via the second rocker arm 48L. The profile of the third lift cam 68 is set similarly to that of the first lift cam 56. The configuration of the second roller 66L is the same as the configuration of the second roller 66R.

The variable valve lift mechanism 32 includes a switching mechanism 70 that switches between a state where the first rocker arm 46 and the second rocker arm 48R are connected and a state where they are separated. The switching mechanism 70 is configured such that the switching force causes the acting force of the first lift cam 56 to be transmitted to the second rocker arm 48R via the first rocker arm 46 and the acting force to the second rocker arm 48R. The operation state of the exhaust valve 30 (front) can be switched between the valve operation state by the first lift cam 56 and the valve operation state by the second lift cam 64 by switching the state where it is not transmitted.

As shown in FIG. 2, the first rocker arm 46 has a first support shaft 72 installed concentrically with the first roller 58, and the second rocker arms 48 R and 48 L have second rollers 66 R, The

second support shafts

74R and 74L are provided concentrically with 66L.

In the state shown in FIG. 2, a part of the first pin 76 that is mostly inserted into the first rocker arm 46 is inserted into the second support shaft 74R of the second rocker arm 48R. Thus, the first rocker arm 46 and the second rocker arm 48R are connected via the first pin 76. Accordingly, when the first rocker arm 46 swings with the rotation of the first lift cam 56, the second rocker arm 48R also swings with this, so that the exhaust valve 30 (front) follows the profile of the first lift cam 56. Open and close.

One end of the second pin 78 inserted into the second support shaft 74R protrudes beyond the side surface of the second rocker arm 48R. One end of the protruding second pin 78 is in contact with the displacement member 82 of the driving means 80. The driving unit 80 is configured to be able to displace the displacement member 82 in the left-right direction in FIG. 2 in accordance with a command from the ECU 40.

One end of the first support shaft 72 of the first rocker arm 46 is closed, and a return spring 84 is installed therein. The return spring 84 presses the first pin 76 rightward in FIG. Thus, the first pin 76 and the second pin 78 are urged to the right in FIG.

In the connected state shown in FIG. 2, when the driving member 80 displaces the displacement member 82 in the left direction in FIG. 2 with a force that overcomes the urging force of the return spring 84, the second pin 78 and the first pin 76 are shown in FIG. To the left, and the state shown in FIG. 6 is obtained. FIG. 6 is a cross-sectional view of the first rocker arm 46 and the

second rocker arms

48R and 48L provided in the variable valve lift mechanism 32. In this state, the first pin 76 and the second pin 78 are in contact with each other in the gap between the first rocker arm 46 and the second rocker arm 48R. For this reason, even if the first rocker arm 46 swings as the first lift cam 56 rotates, the swing is not transmitted to the second rocker arm 48R. The second roller 66R of the second rocker arm 48R is in contact with the second lift cam 64. For this reason, when the second rocker arm 48R swings with the rotation of the second lift cam 64, the exhaust valve 30 (front) opens and closes according to the profile of the second lift cam 64.

Further, in the state shown in FIG. 6, that is, in the state where the first rocker arm 46 and the second rocker arm 48R are separated, the first roller 58 of the first rocker arm 46 is moved to the first lift cam 56 as shown in FIG. When touching the base circle, the centers of the two

pins

76 and 78 coincide. At this time, it is possible to switch to the connected state shown in FIG. 2 by operating the driving means 80 and moving these

pins

76 and 78 in the right direction in FIG.

As described above, according to the variable valve lift mechanism 32, the exhaust valve 30 (rear) is always opened and closed using the third lift cam 68, and the first rocker arm 46 and the second rocker arm 48R By switching between the connected state and the separated state, the operating state of the exhaust valve 30 (front) can be switched between the valve operating state by the first lift cam 56 and the valve operating state by the second lift cam 64.

[Characteristic operation of the first embodiment]
Next, characteristic operations of the system according to the first embodiment will be described with reference to FIGS. The system according to the first embodiment is characterized by an operation for determining an abnormal operation of the variable valve lift mechanism 32. That is, when an operation abnormality occurs in the variable valve lift mechanism 32 and a situation in which the lift cam used for valve operation cannot be switched occurs, there is a concern that fuel consumption and emission may be deteriorated. For this reason, it is desirable that an abnormal operation occurring in the variable valve lift mechanism 32 is detected early and with high accuracy. In this regard, for example, it is conceivable to provide a lift sensor for each of the exhaust valves 30 to detect an abnormal operation. However, in an internal combustion engine having a multi-valve structure in recent years, it is not realistic to provide a lift sensor for each valve because it is structurally limited and it is necessary to determine the failure of these sensors.

Here, the return of exhaust gas to the intake system at the timing of opening the intake valve 28 (IVO) varies depending on the valve overlap amount with the exhaust valve 30. FIG. 7 is a PV diagram showing the change of the in-cylinder pressure P with respect to the in-cylinder stroke volume V. As shown in this figure, the in-cylinder pressure at the intake TDC when the negative valve overlap is set ((a) in the figure) is the same as when the positive valve overlap is set ((b in the figure) ) And (c)). As can be seen from this, for example, when IVO is set in the vicinity of the intake TDC, the negative overlap amount is increased as the closing timing (EVC) of the exhaust valve 30 is advanced from the intake TDC toward BTDC. As a result, the amount of exhaust gas blown back increases.

Accordingly, in the system of the present embodiment, focusing on the fact that the EVC can be changed by the lift cam switching operation by the variable valve lift mechanism 32, the exhaust in the IVO immediately after the switch operation command to the variable valve lift mechanism 32 is taken into account. The presence or absence of abnormal operation of the variable valve lift mechanism 32 is determined based on the gas blowback.

In particular, in the variable valve lift mechanism 32 of the present embodiment, in order to increase the accuracy of the abnormality determination, switching from the first lift cam 56 to the second lift cam 64 increases the exhaust gas blowback in the IVO. The lift profile of the lift cam is set. FIG. 8 is a diagram comparing the lift profiles of the first lift cam 56 and the second lift cam 64. As shown in this figure, the lift profile of the first lift cam 56 of the variable valve lift mechanism 32 of the present embodiment is defined so that EVC is substantially the intake TDC. The lift profile of the second lift cam 64 is set so that the EVC is advanced in the BTDC direction than that of the first lift cam 56 and the lift amount is low.

According to the first lift cam 56 and the second lift cam 64 having such a lift profile, when the switching operation from the first lift cam 56 to the second lift cam 64 is normally performed, the EVC of the exhaust valve 30 (front) is inhaled. The angle is advanced from TDC to BTDC. As a result, the negative valve overlap increases, and the amount of exhaust gas blown back into the intake system immediately after the IVO increases. Further, when the switching operation from the first lift cam 56 to the second lift cam 64 is normally performed, the valve lift amount of the exhaust valve 30 (front) is reduced. As a result, the in-cylinder pressure at the EVC increases, and the amount of exhaust gas blown back into the intake system in the IVO immediately after that increases.

The exhaust gas blowback in the IVO can be detected as the intake pipe pressure. FIG. 9 is a diagram illustrating a change in the intake pipe pressure when the switching operation by the variable valve lift mechanism is performed. As shown in this figure, when an abnormality occurs in the switching operation by the variable valve lift mechanism 32, the intake pipe pressure (absolute pressure) is larger than when switching is normally performed. Therefore, the abnormal operation of the variable valve lift mechanism 32 can be accurately detected by detecting the intake pipe pressure at this time (absolute pressure, pulsation between cycles, variation thereof) using the pressure sensor 44. It becomes possible.

By the way, in Embodiment 1 mentioned above, the blowback of the exhaust gas in IVO is detected using the pressure sensor 44 arrange | positioned in the surge tank 42, and this determines the presence or absence of abnormality of the variable valve lift mechanism 32. It is said. However, the method for detecting the exhaust gas blowback at the IVO is not limited to this. For example, in an internal combustion engine including an in-cylinder pressure sensor, the in-cylinder pressure detection value at the IVO may be used. This can also be applied to the system of the second embodiment described later.

In the first embodiment described above, the variable valve lift mechanism 32 capable of selecting the lift cam of one of the two exhaust valves 30 (front) from two is used. The configuration of the applicable variable valve lift mechanism is not limited to this. That is, if the EVC of at least one exhaust valve can be changed from the vicinity of the intake TDC toward the BTDC toward the advance side, for example, a variable valve in which both lift cams of the two exhaust valves can be selected from a plurality of types. A lift mechanism may be used. Also, an exhaust valve is provided for transmitting the rotational motion of the camshaft to the exhaust valve as a lift motion, and the exhaust valve is changed by changing the swing position of the swing member. A working angle variable mechanism capable of expanding or reducing the working angle while keeping the valve opening timing substantially constant may be used. This can also be applied to the system of the second embodiment described later.

Further, in the above-described first embodiment, no mention is made of the operating state when determining whether or not the variable valve lift mechanism 32 is abnormal, but it is preferable to execute it during the fuel cut. As a result, it is possible to determine whether or not the variable valve lift mechanism 32 is abnormal without affecting the torque request of the driver.

In the first embodiment described above, the pressure sensor 44 corresponds to the “intake pipe pressure acquisition means” in the first invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 10 and FIG. FIG. 10 is a diagram for explaining a system configuration according to the second embodiment of the present invention. The system of the second embodiment is configured in the same manner as the system of the first embodiment shown in FIG. 1 described above except that the configuration of the variable valve device that drives the intake and

exhaust valves

28 and 30 is different. Yes.

As shown in FIG. 10, the system of the second embodiment includes a variable valve timing mechanism (VVT) 33 as a variable valve operating device for the intake valve 28. In addition to the variable valve lift mechanism 32 described above, the system according to the second embodiment includes a VVT 34 as a variable valve operating device for the exhaust valve 30. The

VVTs

33 and 34 are configured such that the camshaft phase angle with respect to the crankshaft 36 can be advanced or retarded by hydraulic pressure. Since the configuration and functions of the

VVTs

33 and 34 are known techniques, detailed description thereof is omitted.

In the system of the first embodiment described above, in the system in which the IVO is set in the vicinity of the intake TDC, it is determined whether or not the variable valve lift mechanism 32 is abnormal. In this regard, in the system of the second embodiment, when determining whether or not the variable valve lift mechanism 32 is abnormal, the VVT 33 is driven to vary the IVO to the vicinity of the intake TDC. FIG. 11 is a diagram illustrating an example of control for varying the valve timing phase of the intake valve. In the example shown in this figure, the valve timing phase is varied so that the IVO of the intake valve 28 is close to the intake TDC. According to such an operation of the VVT 33, the valve timing according to the engine request is controlled normally, and when the abnormality of the variable valve lift mechanism 32 is determined, the IVO is varied in the vicinity of the intake TDC and the exhaust valve 30 is connected. It is possible to eliminate valve overlap.

In the system according to the second embodiment, when determining whether or not the variable valve lift mechanism 32 is abnormal, the VVT 34 can be driven to make the EVC more variable to the BTDC side. FIG. 12 is a diagram illustrating an example of control for varying the valve timing phase of the exhaust valve. In the example shown in this figure, the valve timing phase is varied so that the EVC of the exhaust valve 30 becomes closer to the BTDC side. According to such an operation of the VVT 34, the negative valve overlap with the intake valve 28 is further expanded when the abnormality is determined in the variable valve lift mechanism 32 while controlling the valve timing according to the engine demand in normal times. Therefore, it is possible to suppress the torque reduction and the generation of abnormal noise from the intake manifold.

By the way, in Embodiment 2 mentioned above, although there is no mention about the operation state at the time of determining the presence or absence of abnormality of the variable valve lift mechanism 32, it is preferable to execute during the fuel cut. As a result, it is possible to determine whether or not the variable valve lift mechanism 32 is abnormal without affecting the torque request of the driver. If the

VVTs

33 and 34 are varied at the time of abnormality determination of the variable valve lift mechanism 32, it is desirable to return to the original VVT position after returning from the fuel cut after completion of the abnormality determination. Thereby, the deterioration of the emission when returning from the fuel cut can be effectively suppressed.

In the second embodiment described above, the pressure sensor 44 corresponds to the “intake pipe pressure acquisition means” in the first invention.

In the second embodiment, the VVT 33 corresponds to the “intake valve phase variable mechanism” in the fifth invention, and the VVT 34 corresponds to the “exhaust valve phase variable mechanism” in the sixth invention. .

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 16 Intake passage 18 Exhaust passage 24 Fuel injection valve 26 Spark plug 28 Intake valve 30 Exhaust valve 32 Variable

valve lift mechanism

33, 34 Variable valve timing mechanism 36 Crankshaft 38 Crank angle sensor 40 ECU (Electronic Control Unit)
42 Surge tank 44 Pressure sensor 46

First rocker arm

48L, 48R Second rocker arm 54 Camshaft 56 First lift cam 64 Second lift cam 68 Third lift cam 70 Switching mechanism 76 First pin 78 Second pin 80 Driving means 82 Displacement member 84 Return spring

Claims

A variable valve lift mechanism capable of variably setting the lift characteristic of the exhaust valve of the internal combustion engine;
Intake pipe pressure acquisition means for acquiring the intake pipe pressure of the internal combustion engine;
When the variable valve lift mechanism is driven to advance the closing timing of the exhaust valve in the BTDC direction, the variable valve lift is based on the change in the intake pipe pressure when the intake valve is opened immediately after the operation. An abnormality determining means for determining an abnormal operation of the mechanism;
An abnormality determination device for an internal combustion engine, comprising:
The variable valve lift mechanism is
A first lift cam;
A second lift cam at which the closing timing of the exhaust valve is advanced in the BTDC direction relative to the first lift cam;
A switching mechanism for switching a lift cam for operating the exhaust valve between the first lift cam and the second lift cam;
2. The abnormality determination device for an internal combustion engine according to claim 1, wherein the abnormality determination unit determines an abnormality related to a switching operation from the first lift cam to the second lift cam by the switching mechanism.
The opening timing of the intake valve is in the vicinity of the intake TDC,
The abnormality determination device for an internal combustion engine according to claim 2, wherein the closing timing of the exhaust valve by the second lift cam is a timing advanced from the intake TDC in the BTDC direction.
The internal combustion engine abnormality determination device according to claim 2 or 3, wherein a lift amount of the exhaust valve by the second lift cam is smaller than that of the first lift cam.
An intake valve phase variable mechanism capable of variably setting the phase of the intake valve;
Valve control means for driving the intake valve phase variable mechanism to vary the opening timing of the intake valve to the vicinity of the intake TDC when the abnormality determining means determines an abnormal operation of the variable valve lift mechanism;
The abnormality determination device for an internal combustion engine according to claim 1, further comprising:
An exhaust valve phase variable mechanism capable of variably setting the phase of the exhaust valve;
A second valve control means for driving the exhaust valve phase variable mechanism to advance the closing timing of the exhaust valve in the BTDC direction when the abnormality determination means determines an operation abnormality of the variable valve lift mechanism;
The abnormality determination device for an internal combustion engine according to any one of claims 1 to 5, further comprising:
The abnormality determination device for an internal combustion engine according to any one of claims 1 to 6, wherein the abnormality determination means determines an operation abnormality of the variable valve lift mechanism during fuel cut of the internal combustion engine.