JP2018028267A - Abnormality diagnosis device for variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose abnormality of a variable compression ratio mechanism with good accuracy, in an abnormality diagnosis device for diagnosing abnormality of the variable compression ratio mechanism which can switch a mechanical compression ratio of an internal combustion engine at least into two stages.SOLUTION: In a state where an internal combustion engine is operated in a high expansion ratio, while an intake pressure is kept constant, compression ratio switching processing is executed for controlling a variable compression ratio mechanism and an adjusting device in order to switch a mechanical compression ratio. In the case where an intake amount difference Δmc which is a difference of the intake air amount before and after the execution of the compression ratio switching processing is equal to or greater than an intake amount difference threshold value Δmcthre, the variable compression ratio mechanism is diagnosed to be normal, and in the case where the intake amount difference Δmc is below the intake amount difference threshold value Δmcthre, the variable compression ratio mechanism is diagnosed as abnormal.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an abnormality diagnosis device applied to a variable compression ratio mechanism for changing a mechanical compression ratio of an internal combustion engine.

  In a variable compression ratio mechanism capable of switching a mechanical compression ratio of an internal combustion engine between a first compression ratio and a second compression ratio lower than the first compression ratio, the mechanical compression ratio of the internal combustion engine is variable so as to be the first compression ratio. The intake air amount during idle operation when the compression ratio mechanism is controlled, and the intake air during idle operation when the variable compression ratio mechanism is controlled so that the mechanical compression ratio of the internal combustion engine becomes the second compression ratio. A technique for diagnosing abnormality of the variable compression ratio mechanism using a difference from the air amount (hereinafter referred to as “air amount difference”) as a parameter has been proposed (see, for example, Patent Document 1).

JP 2003-161175 A JP 2014-224494 A JP 2010-024859 A Japanese Patent Laid-Open No. 2006-118181

  By the way, in the conventional technology described above, the difference between the air amount difference when the variable compression ratio mechanism is normal and the air amount when the variable compression ratio mechanism is abnormal may be small. It may be difficult to accurately diagnose an abnormality in the compression ratio mechanism.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an abnormality diagnosis device for diagnosing an abnormality in a variable compression ratio mechanism that can switch the mechanical compression ratio of an internal combustion engine in at least two stages. It is to accurately diagnose abnormality of the variable compression ratio mechanism.

The present invention employs the following means in order to solve the above-described problems. That is, the first invention in the present application is an abnormality diagnosis device applied to a variable compression ratio mechanism capable of switching the mechanical compression ratio of an internal combustion engine in at least two stages. The internal combustion engine includes a variable valve mechanism that can change a closing timing of the intake valve, an intake pressure sensor that detects an intake pressure in the intake manifold, an intake air amount sensor that detects an intake air amount of the internal combustion engine, And an adjusting device for adjusting the amount of intake air supplied to the intake manifold. In the abnormality diagnosis device, the intake pressure of the intake manifold is larger than when the expansion ratio of the internal combustion engine is larger than the effective compression ratio and the expansion ratio of the internal combustion engine is equal to the effective compression ratio. Further, by controlling the variable valve mechanism and the adjusting device, an expansion ratio control means for operating the internal combustion engine at a high expansion ratio, and when the internal combustion engine is operated at a high expansion ratio, the internal combustion engine In order to switch the mechanical compression ratio, the measured value of the intake pressure sensor after the compression ratio control means for controlling the variable compression ratio mechanism and the mechanical compression ratio switching control by the compression ratio control means is executed. Intake air for controlling the adjusting device so as to be equal to the measured value of the intake air pressure sensor before the mechanical compression ratio switching control by the compression ratio control means is executed. The measured value of the intake pressure sensor after the force control means and the mechanical compression ratio switching control by the compression ratio control means are executed is the measured value before the mechanical compression ratio switching control by the compression ratio control means is executed. The measured value of the intake air amount sensor when it is equal to the measured value of the intake air pressure sensor, the measured value of the intake air amount sensor before the mechanical compression ratio switching control by the compression ratio control means is executed, If the difference is less than a predetermined intake amount difference threshold, the variable compression ratio mechanism is diagnosed as abnormal, and if the difference is greater than or equal to the predetermined intake amount difference threshold, the variable compression ratio mechanism Diagnostic means for diagnosing that is normal.

Next, a second invention in the present application is an abnormality diagnosis device applied to a variable compression ratio mechanism capable of switching a mechanical compression ratio of an internal combustion engine in at least two stages. The internal combustion engine includes a variable valve mechanism that can change a closing timing of the intake valve, an intake pressure sensor that detects an intake pressure in the intake manifold, an intake air amount sensor that detects an intake air amount of the internal combustion engine, An adjustment device for adjusting the intake air amount supplied to the intake manifold;
Is provided. In the abnormality diagnosis device, the intake pressure of the intake manifold is larger than when the expansion ratio of the internal combustion engine is larger than the effective compression ratio and the expansion ratio of the internal combustion engine is equal to the effective compression ratio. Further, by controlling the variable valve mechanism and the adjusting device, an expansion ratio control means for operating the internal combustion engine at a high expansion ratio, and when the internal combustion engine is operated at a high expansion ratio, the internal combustion engine In order to switch the mechanical compression ratio, the measured value of the intake air amount sensor after the compression ratio control means for controlling the variable compression ratio mechanism and the switching control of the mechanical compression ratio by the compression ratio control means is executed. An intake air amount control for controlling the adjusting device so as to be equal to the measured value of the intake air amount sensor before the mechanical compression ratio switching control by the compression ratio control means is executed. And a measured value of the intake air amount sensor after the mechanical compression ratio switching control by the compression ratio control unit is executed is the intake air amount before the mechanical compression ratio switching control by the compression ratio control unit is executed. The difference between the measured value of the intake pressure sensor when it is equal to the measured value of the sensor and the measured value of the intake pressure sensor before the mechanical compression ratio switching control by the compression ratio control means is executed Is less than a predetermined intake pressure difference threshold, it is diagnosed that the variable compression ratio mechanism is abnormal, and if the difference is greater than or equal to the predetermined intake pressure difference threshold, the variable compression ratio mechanism is normal. Diagnosing means for diagnosing that.

  The “mechanical compression ratio” in the present application is the ratio between the volume in the cylinder when the piston is located at the top dead center (combustion chamber volume) and the volume within the cylinder when the piston is located at the bottom dead center. Indicates. The “effective compression ratio” indicates a ratio between the combustion chamber volume and the volume in the cylinder at the closing timing of the intake valve. Further, the “expansion ratio” indicates a ratio between the combustion chamber volume and the volume in the cylinder when the piston is located at the bottom dead center.

  According to the present invention, it is possible to accurately diagnose abnormality of the variable compression ratio mechanism.

It is a figure which shows schematic structure of the internal combustion engine in this embodiment. It is sectional drawing which shows the structure of a variable-length connecting rod. It is a figure which shows the structure of a switching mechanism typically. It is a figure which shows the switching mechanism when it exists in a 2nd state. It is a 1st figure which shows the correlation with intake manifold pressure (Pm) and intake air amount (mc). It is a flowchart which shows the process routine which ECU performs when abnormality diagnosis of a variable compression ratio mechanism is performed in 1st Embodiment. It is a 2nd figure which shows the correlation with intake manifold pressure (Pm) and intake air amount (mc). It is a flowchart which shows the process routine which ECU performs when performing abnormality diagnosis of a variable compression ratio mechanism in 2nd Embodiment.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Embodiment 1>
First, the 1st Embodiment of this invention is described based on FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a 4-stroke cycle spark ignition internal combustion engine having a plurality of cylinders. In FIG. 1, only one cylinder is shown among the plurality of cylinders.

  The internal combustion engine 1 includes a crankcase 2, a cylinder block 3, and a cylinder head 4. A crankshaft 200 is rotatably accommodated in the crankcase 2. A cylindrical cylinder 300 is formed in the cylinder block 3. The piston 5 is slidably accommodated in the cylinder 300. The piston 5 and the crankshaft 200 are connected by a variable length connecting rod 6 described later.

  An intake port 11 and an exhaust port 14 are formed in the cylinder head 4. The intake port 11 is connected to the intake pipe 401 via the intake manifold 400. The cylinder head 4 also includes an intake valve 9 for opening and closing the opening end of the intake port 11 in the combustion chamber 7 and an intake camshaft 10 for opening and closing the intake valve 9. The intake camshaft 10 is provided with a variable valve mechanism 10a for changing the rotation phase of the intake camshaft 10. Further, the cylinder head 4 includes an exhaust valve 12 for opening and closing the opening end of the exhaust port 14 in the combustion chamber 7 and an exhaust camshaft 13 for opening and closing the exhaust valve 12. Further, the cylinder head 4 includes a spark plug 8 for igniting the air-fuel mixture in the combustion chamber 7.

  A fuel injection valve 103 for injecting fuel toward the intake port 11 is attached to the intake manifold 400. The intake pipe 401 is provided with a throttle valve 402 for adjusting the amount of air taken into the cylinder 300 of the internal combustion engine 1 by changing the passage cross-sectional area in the intake pipe 401. The throttle valve 402 corresponds to an “adjusting device” according to the present invention.

  Here, the variable length connecting rod 6 is connected to the piston 5 by the piston pin 21 at the small end portion thereof, and is connected to the crank pin 22 of the crankshaft 200 at the large end portion thereof. The variable length connecting rod 6 is configured to be able to change the distance from the axial center of the piston pin 21 to the axial center of the crank pin 22, that is, the effective length. When the effective length of the variable length connecting rod 6 is extended, the length from the axis of the crank pin 22 to the axis of the piston pin 21 becomes longer, so that the piston 5 has a top dead center as shown by the solid line in FIG. The volume of the combustion chamber 7 when it is at is reduced. On the other hand, when the effective length of the variable-length connecting rod 6 is shortened, the length from the axial center of the crank pin 22 to the axial center of the piston pin 21 is shortened, so that the piston 5 moves upward as shown by the broken line in FIG. The volume of the combustion chamber 7 when it is at the dead center is increased. As described above, even if the effective length of the variable-length connecting rod 6 changes, the stroke of the piston 5 does not change. Therefore, the in-cylinder volume (combustion chamber volume) and the piston 5 when the piston 5 is located at the top dead center. The mechanical compression ratio, which is the ratio to the in-cylinder volume at the bottom dead center, changes.

(Configuration of variable length connecting rod 6)
Here, the structure of the variable-length connecting rod 6 in this embodiment is demonstrated based on FIG. The variable length connecting rod 6 includes a connecting rod body 31, an eccentric member 32 rotatably attached to the connecting rod body 31, a first piston mechanism 33 provided in the connecting rod body 31, and a second provided in the connecting rod body 31. Piston mechanism 34 and both piston mechanisms 33
, 34, and a switching mechanism 35 for switching the flow of the hydraulic oil to the hydraulic fluid.

  The connecting rod body 31 has a crank receiving opening 41 for receiving the crank pin 22 of the crankshaft at one end thereof, and a sleeve receiving opening 42 for receiving a sleeve of an eccentric member 32 described later at the other end. Since the crank receiving opening 41 is larger than the sleeve receiving opening 42, the end of the connecting rod body 31 on the side where the crank receiving opening 41 is provided is referred to as the large end 31a, and the side on which the sleeve receiving opening 42 is provided. The end of the connecting rod body 31 is referred to as a small end 31b.

  In the present specification, the axis of the crank receiving opening 41 (ie, the axis of the crank pin 22 received in the crank receiving opening 41) and the axis of the sleeve receiving opening 42 (ie, received in the sleeve receiving opening 42). The imaginary straight line X passing through the axis of the sleeve to be connected is referred to as the axis of the variable length connecting rod 6. The length of the variable length connecting rod 6 in the direction perpendicular to the axis X of the variable length connecting rod 6 and perpendicular to the axis of the crank receiving opening 41 is referred to as the width of the variable length connecting rod 6. In addition, the length of the variable length connecting rod 6 in the direction parallel to the axis of the crank receiving opening 41 is referred to as the thickness of the variable length connecting rod 6.

  Next, the eccentric member 32 includes a cylindrical sleeve 32a received in a sleeve receiving opening 42 formed in the connecting rod body 31, and a first arm 32b extending from the sleeve 32a in one direction in the width direction of the connecting rod body 31. And a second arm 32c extending from the sleeve 32a in the other direction (generally opposite to the one direction) in the width direction of the connecting rod body 31. Since the sleeve 32 a is rotatable in the sleeve receiving opening 42, the eccentric member 32 is attached to the connecting rod body 31 so as to be rotatable in the circumferential direction of the small end portion 31 b at the small end portion 31 b of the connecting rod body 31. become.

  The sleeve 32 a of the eccentric member 32 has a piston pin receiving opening 32 d for receiving the piston pin 21. The piston pin receiving opening 32d is formed in a cylindrical shape. The piston pin receiving opening 32d is formed such that its axis is eccentric with respect to the axis of the sleeve receiving opening 42 (the axis of the sleeve 32a).

  As described above, since the axis of the piston pin receiving opening 32d of the sleeve 32a is eccentric from the axis of the sleeve 32a, the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 changes when the eccentric member 32 rotates. To do. When the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 is on the large end portion 31a side, the effective length of the variable length connecting rod 6 is shortened. Conversely, when the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 is on the side opposite to the large end portion 31a side, the effective length of the variable length connecting rod 6 becomes long. Therefore, according to the present embodiment, the effective length of the variable length connecting rod 6 can be changed by rotating the eccentric member 32.

  Next, the 1st piston mechanism 33 has the 1st cylinder 33a formed in the connecting rod main body 31, and the 1st piston 33b which slides in the 1st cylinder 33a. Most or all of the first cylinders 33 a are arranged on the first arm 32 b side with respect to the axis X of the variable length connecting rod 6. In addition, the first cylinder 33a is disposed so as to be inclined at a certain angle with respect to the axis X so as to protrude in the width direction of the connecting rod body 31 as it approaches the small end portion 31b. Further, the first cylinder 33 a communicates with the switching mechanism 35 via the first piston communication oil passage 51.

The first piston 33 b is connected to the first arm 32 b of the eccentric member 32 by the first connecting member 45. The first piston 33b is rotatably connected to the first connecting member 45 by a pin. The first arm 32b is rotatably connected to the first connecting member 45 by a pin at the end opposite to the side connected to the sleeve 32a.

  On the other hand, the 2nd piston mechanism 34 has the 2nd cylinder 34a formed in the connecting rod main body 31, and the 2nd piston 34b which slides in the 2nd cylinder 34a. Most or all of the second cylinder 34 a is disposed on the second arm 32 c side with respect to the axis X of the variable length connecting rod 6. Further, the second cylinder 34a is disposed so as to be inclined at a certain angle with respect to the axis X so as to protrude in the width direction of the connecting rod body 31 as it approaches the small end portion 31b. The second cylinder 34 a communicates with the switching mechanism 35 via the second piston communication oil passage 52.

  The second piston 34 b is connected to the second arm 32 c of the eccentric member 32 by the second connecting member 46. The second piston 34b is rotatably connected to the second connecting member 46 by a pin. The second arm 32c is rotatably connected to the second connecting member 46 by a pin at the end opposite to the side connected to the sleeve 32a.

  Next, as will be described later, the switching mechanism 35 blocks the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and allows the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. And a second state in which the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a is allowed and the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a is blocked. It is a switching mechanism.

  Here, when the switching mechanism 35 is in the first state, the hydraulic oil is supplied into the first cylinder 33a, and the hydraulic oil is discharged from the second cylinder 34a. For this reason, the 1st piston 33b rises and the 1st arm 32b of eccentric member 32 connected to the 1st piston 33b also rises in connection with it. On the other hand, the second piston 34b is lowered, and accordingly, the second arm 32c connected to the second piston 34b is also lowered. As a result, the eccentric member 32 rotates clockwise in FIG. 2, so that the position of the piston pin receiving opening 32 d is separated from the position of the crank pin 22. That is, the effective length of the variable length connecting rod 6 is increased. When the second piston 34b comes into contact with the bottom surface of the second cylinder 34a, the rotation of the eccentric member 32 is restricted, and the rotation position of the eccentric member 32 is the position (hereinafter referred to as “high compression ratio position”). Held). Hereinafter, the mechanical compression ratio when the switching mechanism 35 is in the first state (when the eccentric member 32 is in the high compression ratio position) is referred to as a first compression ratio.

  When the switching mechanism 35 is in the first state, basically, the first piston 33b and the second piston 34b are in the positions described above (the second piston 34b is in the second cylinder 34a without supplying hydraulic fluid from the outside. Move to the position where it touches the bottom surface). This is because when the piston 5 reciprocates in the cylinder 300 of the internal combustion engine 1 and an upward inertia force acts on the piston 5, the second piston 34b is pushed in, so that the hydraulic oil in the second cylinder 34a is This is to move to one cylinder 33a. On the other hand, when the piston 5 reciprocates in the cylinder 300 of the internal combustion engine 1 and a downward inertia force acts on the piston 5, or combustion of the air-fuel mixture occurs in the combustion chamber 7 and a downward force acts on the piston 5. When this occurs, the force that pushes in the first piston 33b works, but since the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a is blocked by the switching mechanism 35, the hydraulic oil in the first cylinder 33a flows out. do not do. Therefore, the first piston 33b is not pushed in.

Next, when the switching mechanism 35 is in the second state, the hydraulic oil is supplied into the second cylinder 34a, and the hydraulic oil is discharged from the first cylinder 33a. For this reason, the 2nd piston 34b raises and the 2nd arm 32c of the eccentric member 32 connected with the 2nd piston 34b also rises in connection with it. On the other hand, the first piston 33b is lowered, and the first arm 32b connected to the first piston 33b is also lowered. As a result, the eccentric member 32 rotates counterclockwise in FIG. 2, so that the position of the piston pin receiving opening 32 d approaches the position of the crank pin 22. That is, the effective length of the variable length connecting rod 6 is shortened. When the first piston 33b comes into contact with the bottom surface of the first cylinder 33a, the rotation of the eccentric member 32 is restricted, and the rotation position of the eccentric member 32 is the position (hereinafter referred to as “low compression ratio position”). Held). Therefore, the mechanical compression ratio of the internal combustion engine 1 is lower when the switching mechanism 35 is in the second state than when it is in the first state. Hereinafter, the mechanical compression ratio when the switching mechanism 35 is in the second state (when the eccentric member 32 is in the low compression ratio position) is referred to as a second compression ratio. The second compression ratio is a mechanical compression ratio lower than the first compression ratio as described above.

  Even when the switching mechanism 35 is in the second state, the first piston 33b and the second piston 34b basically do not supply hydraulic fluid from the outside, and the positions of the first piston 33b and the second piston 34b described above (the first piston 33b is the first cylinder). To a position where it abuts the bottom surface of 33a. This is because when the piston 5 reciprocates in the cylinder 300 of the internal combustion engine 1 and a downward inertial force acts on the piston 5 or when the air-fuel mixture burns in the combustion chamber 7 and the downward force is exerted on the piston 5. This is because when the first piston 33b is actuated, the hydraulic oil in the first cylinder 33a moves to the second cylinder 34a. On the other hand, when the piston 5 reciprocates in the cylinder 300 of the internal combustion engine 1 and an upward inertial force is applied to the piston 5, a force for pushing the second piston 34b is applied, but the switching mechanism 35 causes the second cylinder 34a to move from the second cylinder 34a. Since the flow of hydraulic oil to the first cylinder 33a is blocked, the hydraulic oil in the second cylinder 34a does not flow out. Therefore, the second piston 34b is not pushed in.

(Configuration of switching mechanism 35)
Next, an embodiment of the switching mechanism 35 will be described with reference to FIGS. FIG. 3 shows the switching mechanism 35 when in the first state, and FIG. 4 shows the switching mechanism 35 when in the second state. The switching mechanism 35 includes two switching pins 61 and 62 and one check valve 63. The two switching pins 61 and 62 are slidably accommodated in cylindrical pin accommodating spaces 64 and 65, respectively. 3 and 4, arrows indicate the flow of hydraulic oil in each state.

  Of the two switching pins 61 and 62 described above, one switching pin 61 (first switching pin 61) has two circumferential grooves 61a and 61b extending in the circumferential direction. These circumferential grooves 61 a and 61 b communicate with each other through a communication path 61 c formed in the first switching pin 61. Further, in the first pin housing space 64 for housing the first switching pin 61, the first switching pin 61 is moved from one end portion to the other end portion (the lower portion in FIG. 3) in the first pin housing space 64. The first urging spring 67 for urging from the side end to the upper end) is accommodated.

  Of the two switching pins 61 and 62 described above, the other switching pin 62 (second switching pin 62) also has two circumferential grooves 62a and 62b extending in the circumferential direction thereof. These circumferential grooves 62 a and 62 b communicate with each other by a communication path 62 c formed in the second switching pin 62. Further, in the second pin housing space 65 for housing the second switching pin 62, the second switching pin 62 is moved from one end to the other end (the upper side in FIG. 3) in the second pin housing space 65. The second urging spring 68 for urging from the end of the second end toward the lower end is accommodated.

  The check valve 63 is accommodated in a cylindrical check valve accommodation space 66. The check valve 63 is configured to allow the flow from the primary side (upper side in FIG. 3) to the secondary side (lower side in FIG. 3) and to block the flow from the secondary side to the primary side. Is done.

The first pin accommodating space 64 that accommodates the first switching pin 61 is communicated with the first cylinder 33 a via the first piston communication oil passage 51. The first pin housing space 64 is communicated with the check valve housing space 66 via the two space communication oil passages 53 and 54. One of the first space communication oil passages 53 communicates the first pin housing space 64 and the secondary side of the check valve housing space 66. The other second space communication oil passage 54 allows the first pin accommodation space 64 and the primary side of the check valve accommodation space 66 to communicate with each other.

  The second pin accommodating space 65 that accommodates the second switching pin 62 is communicated with the second cylinder 34 a via the second piston communication oil passage 52. The second pin housing space 65 is communicated with the check valve housing space 66 via the two space communication oil passages 55 and 56. One of the third space communication oil passages 55 communicates the second pin accommodation space 65 with the secondary side of the check valve accommodation space 66. The other fourth space communication oil passage 56 allows the second pin accommodation space 65 and the primary side of the check valve accommodation space 66 to communicate with each other.

  The first pin accommodating space 64 communicates with a first control oil passage 57 formed in the connecting rod body 31. At that time, the first control oil passage 57 has an end (an upper end in FIG. 3) opposite to an end (the lower end in FIG. 3) where the first biasing spring 67 is provided. Part) is communicated with the first pin housing space 64. Further, the second pin housing space 65 communicates with a second control oil passage 58 formed in the connecting rod body 31. At that time, the second control oil passage 58 has an end (the lower end in FIG. 3) opposite to the end (the upper end in FIG. 3) where the second urging spring 68 is provided. Part) is communicated with the second pin housing space 65. The first control oil passage 57 and the second control oil passage 58 are formed so as to communicate with the crank receiving opening 41 and through an oil passage (not shown) formed in the crank pin 22. To an external oil switching valve (OSV) 75. The OSV 75 referred to here is, for example, a valve mechanism that switches between conduction and interruption between two control oil passages 57 and 58 and an oil pump (not shown).

  The primary side of the check valve accommodating space 66 is communicated with a hydraulic oil supply source 76 such as an oil pump through a supplementary oil passage 59 formed in the connecting rod body 31. The replenishing oil passage 59 is an oil passage for replenishing hydraulic oil leaking from each part of the switching mechanism 35 to the outside.

(Operation of switching mechanism 35)
In the switching mechanism 35 configured as described above, when the OSV 75 connects the control oil passages 57 and 58 and the oil pump, the hydraulic pressure acting on the switching pins 61 and 62 as shown in FIG. Accordingly, the urging springs 67 and 68 are contracted, so that the switching pins 61 and 62 cause the first piston communication oil path 51 and the first space communication oil path 53 to communicate with each other via the communication path 61 c of the first switching pin 61. The second piston communication oil passage 52 and the fourth space communication oil passage 56 are moved and held at a position where the second piston communication oil passage 52 and the fourth space communication oil passage 56 are communicated with each other via the communication passage 62 c of the second switching pin 62. In this case, the first cylinder 33a is connected to the secondary side of the check valve 63, and the second cylinder 34a is connected to the primary side of the check valve 63. Therefore, the hydraulic oil in the second cylinder 34 a passes through the first cylinder communication oil passage 52, the fourth space communication oil passage 56, the first space communication oil passage 53, and the first piston communication oil passage 51. It becomes possible to move to 33a. On the other hand, the hydraulic oil in the first cylinder 33a cannot move to the second cylinder 34a. Therefore, when the OSV 75 connects the control oil passages 57, 58 and the oil pump, the switching mechanism 35 blocks the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a, and the second It will be in the state (1st state) which permits the flow of the hydraulic oil from the cylinder 34a to the 1st cylinder 33a.

On the other hand, when the OSV 75 shuts off the control oil passages 57, 58 and the oil pump, only the urging force of the urging springs 67, 68 acts on the switching pins 61, 62, and therefore, as shown in FIG. Further, the switching pins 61 and 62 are connected to the first piston communication oil passage 51 and the second space communication oil passage 54 via the communication passage 61 c of the first switching pin 61, and the second switching pin 62 is connected. The second piston communication oil passage 52 and the third space communication oil passage 55 are moved and held at a position where they can communicate with each other via the passage 62c. In that case, the first cylinder 33 a is connected to the primary side of the check valve 63, and the second cylinder 34 a is connected to the secondary side of the check valve 63. Therefore, the hydraulic oil in the first cylinder 33 a passes through the first cylinder communication oil passage 51, the second space communication oil passage 54, the third space communication oil passage 55, and the second piston communication oil passage 52 through the second cylinder. It becomes possible to move to 34a. On the other hand, the hydraulic oil in the second cylinder 34a cannot move to the first cylinder 33a. Therefore, when the OSV 75 shuts off the control oil passages 57 and 58 and the oil pump, the switching mechanism 35 allows the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a, and the second It will be in the state (2nd state) which interrupts | blocks the flow of the hydraulic fluid from the cylinder 34a to the 1st cylinder 33a.

  As described above, when the OSV 75 switches between supplying and shutting off the hydraulic oil to the first pin housing space 64 and the second pin housing space 65, the switching mechanism 35 can be switched between the first state and the second state. Accordingly, the mechanical compression ratio of the internal combustion engine 1 can be switched to either the first compression ratio or the second compression ratio. The OSV 75 may be provided for each switching mechanism 35 of each cylinder 300, or only one OSV 75 may be provided for the switching mechanisms 35 of all the cylinders 300.

  Here, referring back to FIG. 1, the internal combustion engine 1 configured as described above is provided with an ECU 100. The ECU 100 is an electronic control unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ECU 100 is electrically connected to various sensors such as an air flow meter 101, an accelerator position sensor 102, a crank position sensor 201, and an intake pressure sensor 403, and can input output signals of these various sensors. The air flow meter 101 is a sensor that is attached to an intake passage (not shown) of the internal combustion engine 1 and outputs an electrical signal correlated with the intake air amount, and corresponds to an “intake amount sensor” according to the present invention. The accelerator position sensor 102 is a sensor that outputs an electrical signal correlated with an operation amount (accelerator opening) of an accelerator pedal (not shown). The crank position sensor 201 is a sensor that outputs an electrical signal correlated with the rotational position of the crankshaft 200. The intake pressure sensor 403 is a sensor that is attached to the intake manifold 400 and outputs an electrical signal correlated with the intake pressure in the intake manifold 400 (hereinafter referred to as “intake manifold pressure”).

  The ECU 100 is electrically connected to various devices such as the ignition plug 8, the fuel injection valve 103, the OSV 75, the variable valve mechanism 10a, and the throttle valve 402 in addition to the various sensors described above. The ECU 100 controls the various devices described above based on the output signals of the various sensors described above. For example, the ECU 100 calculates the engine speed calculated from the output signal of the crank position sensor 201 and the output signal (intake air amount) of the air flow meter 101 (with respect to the intake air amount at full load). Based on the actual intake air amount ratio), the target fuel injection amount of the fuel injection valve 103 and the target ignition timing of the spark plug 8 are calculated, and the fuel injection valve 103 and the ignition are calculated according to the target fuel injection amount and the target ignition timing. The plug 8 is controlled.

  Further, the ECU 100 controls the OSV 75 according to the engine load factor. Specifically, the ECU 100 sets the mechanical compression ratio of the internal combustion engine 1 to the above-described first compression ratio (the switching mechanism 35 is in the first state) when the engine load factor is less than a predetermined threshold. OSV75 is controlled. That is, ECU 100 controls OSV 75 so that control oil passages 57 and 58 and the oil pump are connected. On the other hand, when the engine load factor is equal to or greater than the predetermined threshold, the ECU 100 sets the mechanical compression ratio of the internal combustion engine 1 to a second compression ratio lower than the first compression ratio (the switching mechanism 35 enters the second state). Thus, the OSV 75 is controlled. That is, the ECU 100 controls the OSV 75 so that the control oil passages 57 and 58 and the oil pump are shut off.

By the way, if an abnormality occurs in the hydraulic path of the variable compression ratio mechanism, the mechanical compression ratio cannot be switched, which may cause various problems. In particular, when an abnormality occurs in which the eccentric member 32 of the variable-length connecting rod 6 is fixed at the high compression ratio position or the switching mechanism 35 is fixed in the first state, the engine load factor becomes equal to or greater than the predetermined threshold value. In addition, since the mechanical compression ratio cannot be switched from the first compression ratio to the second compression ratio, abnormal combustion of the air-fuel mixture may occur.

(Abnormal diagnosis of variable compression ratio mechanism)
As a method of diagnosing an abnormality in the variable compression ratio mechanism, based on the amount of change in the intake air amount before and after execution of processing in which the ECU 100 controls the OSV 75 to switch the mechanical compression ratio (hereinafter referred to as “compression ratio switching processing”). A method for diagnosing abnormality of the variable compression ratio mechanism can be considered. Specifically, the throttle valve 402 is controlled so that the intake manifold pressure after execution of the compression ratio switching process is equal to the intake manifold pressure before execution of the compression ratio switching process, and the intake manifold pressure after execution of the compression ratio switching process is controlled. Is the same as the intake manifold pressure before the compression ratio switching process (hereinafter referred to as “the intake air amount after switching”), and the air flow meter 101 before the compression ratio switching process. A method of diagnosing abnormality of the variable compression ratio mechanism based on the difference between the measured value (hereinafter referred to as “pre-switching intake air amount”) and the difference (intake air amount difference) is conceivable.

  Here, as shown in FIGS. 1 to 4 described above, when the variable compression ratio mechanism is a mechanism that changes the mechanical compression ratio of the internal combustion engine 1, combustion when the mechanical compression ratio is the first compression ratio is performed. The chamber volume is smaller than the combustion chamber volume when the mechanical compression ratio is the second compression ratio. Therefore, if the intake manifold pressure when the mechanical compression ratio is the first compression ratio is equal to the intake manifold pressure when the mechanical compression ratio is the second compression ratio, the mechanical compression ratio is the first compression ratio. The intake air amount is estimated to be smaller than the intake air amount when the mechanical compression ratio is the second compression ratio. On the other hand, when the mechanical compression ratio cannot be switched normally due to an abnormality in the variable compression ratio mechanism, it is estimated that the intake air amount before and after the execution of the compression ratio switching process is substantially the same.

  By the way, when the combustion chamber volume at the first compression ratio is smaller than the combustion chamber volume at the second compression ratio, burned gas (hereinafter, referred to as “remaining burned gas” remaining in the cylinder 300 when the exhaust valve 12 is closed). The amount of “residual gas”) may be greater at the second compression ratio than at the first compression ratio. If the residual gas amount is different in this way, the difference in intake air amount becomes small even if the variable compression ratio mechanism is normal. As a result, there is a possibility that there is no difference between the intake amount difference when the variable compression ratio mechanism is normal and the intake amount difference when the variable compression ratio mechanism is abnormal so that a highly accurate diagnosis can be made. There is.

  Therefore, in the present embodiment, the internal combustion engine 1 is operated at a high expansion ratio when executing the compression ratio switching process described above. The high expansion ratio operation here is an operation in which the expansion ratio of the internal combustion engine 1 becomes larger than the effective compression ratio (the ratio of the volume in the cylinder 300 at the closing timing of the intake valve 9 to the combustion chamber volume). As a method of realizing such a high expansion ratio operation, the intake valve 9 is closed as compared with a case where an operation in which the expansion ratio is substantially equal to the effective compression ratio (hereinafter referred to as “normal operation”) is performed. A method can be used in which the effective compression ratio is made smaller than the expansion ratio by controlling the variable valve mechanism 10a so that the valve timing is advanced (or delayed).

As described above, when the closing timing of the intake valve 9 is made earlier (or later) than during normal operation, the amount of intake air per cylinder 300 is reduced and the output of the internal combustion engine 1 is reduced. Therefore, when realizing a high expansion ratio operation, in addition to the control of the variable valve mechanism 10a as described above, a control for increasing the opening of the throttle valve 402 so that the intake manifold pressure becomes higher than that during normal operation is used in combination. By doing so, the reduction of the intake air amount accompanying the change of the effective compression ratio is suppressed. As described above, when the high expansion ratio operation is realized by the method of controlling the variable valve mechanism 10a and the throttle valve 402, the intake manifold pressure becomes higher than that in the normal operation, so that the compressibility of the residual gas becomes high. As a result, the difference in intake air amount when the variable compression ratio mechanism is normal is greater during high expansion ratio operation than during normal operation.

  Here, the correlation between the intake manifold pressure (Pm) and the intake air amount (mc) per cylinder 300 when the variable compression ratio mechanism is normal is shown in FIG. A solid line A in FIG. 5 shows a case where the operation is at a high expansion ratio and the mechanical compression ratio is the first compression ratio. An alternate long and short dash line B in FIG. 5 shows a case where the high compression ratio operation is performed and the mechanical compression ratio is the second compression ratio. A solid line A ′ in FIG. 5 indicates a case where the normal operation is performed and the mechanical compression ratio is the first compression ratio. An alternate long and short dash line B ′ in FIG. 5 shows a case where the normal operation is performed and the mechanical compression ratio is the second compression ratio. Mc0 and Pm0 in FIG. 5 indicate the intake air amount and the intake manifold pressure respectively during normal operation and when the mechanical compression ratio is the first compression ratio. Further, Pm1 in FIG. 5 is during high expansion ratio operation, and when the mechanical compression ratio is the first compression ratio, during normal operation, and the mechanical compression ratio is the first compression ratio. The intake manifold pressure for realizing the intake air amount equivalent to the time is shown.

  As shown in FIG. 5, when the internal combustion engine 1 is operating at a high expansion ratio, the mechanical compression ratio is normally switched from the first compression ratio to the second compression ratio while maintaining the intake manifold pressure Pm at Pm1. The intake air amount difference Δmc in the intake air when the mechanical compression ratio is normally switched from the first compression ratio to the second compression ratio while maintaining the intake manifold pressure Pm at Pm0 in a state where the internal combustion engine 1 is normally operated. It becomes larger than the quantity difference Δmc ′. Therefore, when the compression ratio switching process described above is executed while the internal combustion engine 1 is operating at a high expansion ratio, the difference in intake air amount when the variable compression ratio mechanism is normal and the variable compression ratio mechanism are abnormal. In this case, there is a difference that allows a highly accurate diagnosis. As a result, the abnormality diagnosis of the variable compression ratio mechanism can be performed with high accuracy.

  Hereinafter, the execution procedure of the abnormality diagnosis of the variable compression ratio mechanism in the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a processing routine executed by the ECU 100 when performing an abnormality diagnosis of the variable compression ratio mechanism. This processing routine is stored in advance in the ROM of the ECU 100 or the like.

  In the processing routine of FIG. 6, the ECU 100 first determines whether or not a diagnostic condition is satisfied in the processing of S101. The diagnostic conditions here are, for example, that the internal combustion engine 1 is in a warm-up completion state, and the internal combustion engine 1 is in a steady operation state such as an idle operation state (an operation state in which the engine load factor and the engine rotation speed are substantially constant). The condition such as being in is satisfied. If a negative determination is made in the processing of S101, the ECU 100 ends the execution of this processing routine. On the other hand, when an affirmative determination is made in the process of S101, the ECU 100 proceeds to the process of S102.

  In the process of S102, the ECU 100 starts the high expansion ratio operation of the internal combustion engine 1. Specifically, as described above, the ECU 100 controls the variable valve mechanism 10a so that the closing timing of the intake valve 9 is earlier (or slower) than during normal operation, and the intake manifold pressure is higher than during normal operation. The throttle valve 402 is controlled so that the intake air amount becomes the same as that during normal operation. As described above, the ECU 100 executes the processing of S102, thereby realizing the “expansion ratio control means” according to the present invention.

  In the process of S103, the ECU 100 reads the measured value (intake amount before switching) mc0 of the air flow meter 101 and the measured value (intake manifold pressure) Pm1 of the intake pressure sensor 403. Then, the ECU 100 stores the pre-switching intake air amount mc0 and the intake manifold pressure Pm1 in a RAM or the like.

  In the process of S104, the ECU 100 executes a compression ratio switching process. Specifically, the ECU 100 controls the OSV 75 so that the switching mechanism 35 is switched from one of the first state and the second state to the other state. As described above, the ECU 100 executes the processing of S104, thereby realizing the “compression ratio control means” according to the present invention.

  In the process of S105, the ECU 100 increases the opening of the throttle valve 402 so that the measured value (intake manifold pressure) of the intake pressure sensor 403 is equal to the intake manifold pressure Pm1 read in the process of S103.

  In the process of S106, the ECU 100 determines whether the measured value (intake manifold pressure) of the intake pressure sensor 403 is equal to the intake manifold pressure Pm1 read in the process of S103. If a negative determination is made in the process of S106, the ECU 100 returns to the process of S105. On the other hand, when an affirmative determination is made in the process of S106, the ECU 100 proceeds to the process of S107. The ECU 100 executes the process of 105 and the process of S106, thereby realizing the “intake pressure control means” according to the present invention.

  In the process of S107, the ECU 100 reads the measured value (the intake air amount after switching) mc1 of the air flow meter 101. Subsequently, the ECU 100 proceeds to the processing of S108, and calculates the absolute value of the difference between the pre-switching intake air amount mc0 read in the processing of S103 and the post-switching intake air amount mc1 read in the processing of S107. Thus, the intake air amount difference Δmc is obtained.

  In the process of S109, the ECU 100 determines whether or not the intake air amount difference Δmc calculated in the process of S108 is greater than or equal to the intake air amount difference threshold value Δmcthr. The intake air amount difference threshold Δmcthr here is a value obtained by subtracting a margin in consideration of variations of various sensors from the intake air amount difference when the variable compression ratio mechanism is normal or the intake air amount difference. If an affirmative determination is made in S109, the ECU 100 proceeds to the process of S110 and diagnoses that the variable compression ratio mechanism is normal. On the other hand, when a negative determination is made in the process of S109, the ECU 100 proceeds to the process of S111 and diagnoses that the variable compression ratio mechanism is abnormal. The ECU 100 executes the processing of S108 to S111, thereby realizing the “diagnosis means” according to the present invention.

  When the ECU 100 completes the process of S110 or S111, the ECU 100 proceeds to the process of S112 to return the mechanical compression ratio of the internal combustion engine 1 to the mechanical compression ratio before the compression ratio switching process. OSV75 is controlled. Further, the ECU 100 ends the high expansion ratio operation in the process of S113.

  When abnormality diagnosis of the variable compression ratio mechanism is performed according to the procedure described above, between the intake amount difference when the variable compression ratio mechanism is normal and the intake amount difference when the variable compression ratio mechanism is abnormal, Since a difference to the extent that high-accuracy diagnosis can be performed occurs, abnormality diagnosis of the variable compression ratio mechanism can be performed with high accuracy.

  In this embodiment, the example in which the difference in intake air amount (intake amount difference) before and after the execution of the compression ratio switching process is used as a parameter has been described. However, the rate of change of the intake air amount before and after the execution of the compression ratio switching process ( ((Intake air amount after switching) − (intake air amount before switching)) / (intake air amount before switching)) may be used as a parameter. If the intake manifold pressure at the time of executing the compression ratio switching process is relatively high, an abnormality diagnosis of the variable compression ratio mechanism is performed using the intake air amount difference as a parameter, and the intake manifold pressure at the time of executing the compression ratio switching process is relatively low. In this case, abnormality diagnosis of the variable compression ratio mechanism may be performed using the rate of change of the intake air amount as a parameter.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from the above-described first embodiment will be described, and description of the same configuration will be omitted. The difference between the first embodiment described above and the present embodiment is that an abnormality of the variable compression ratio mechanism is determined based on the change in intake manifold pressure when the compression ratio switching process is executed while keeping the intake air amount constant. The point is to diagnose.

  Here, as shown in FIG. 7, in a state where the internal combustion engine 1 is operating at a high expansion ratio, the mechanical compression ratio is changed from the first compression ratio to the second compression ratio while keeping the intake air amount at a constant amount (mc0). The difference between intake manifold pressures before and after switching (intake pressure difference) ΔPm when the engine is normally switched to is that the mechanical compression ratio is the first while the intake air amount is kept at mc0 when the internal combustion engine 1 is normally operated. It becomes larger than the intake pressure difference ΔPm ′ when normally switched from the compression ratio to the second compression ratio. Therefore, when the compression ratio switching process described above is executed while the internal combustion engine 1 is operating at a high expansion ratio, the intake pressure difference when the variable compression ratio mechanism is normal and the variable compression ratio mechanism are abnormal. In this case, a difference to the extent that high-accuracy diagnosis can be performed is generated between the difference and the intake pressure difference. As a result, the abnormality diagnosis of the variable compression ratio mechanism can be performed with high accuracy as in the first embodiment described above.

  Hereinafter, an execution procedure of abnormality diagnosis of the variable compression ratio mechanism in the present embodiment will be described with reference to FIG. FIG. 8 is a processing routine executed by the ECU 100 when performing an abnormality diagnosis of the variable compression ratio mechanism. In the processing routine of FIG. 8, the same reference numerals are given to the same processing as the processing routine of FIG. The difference between the processing routine of FIG. 6 and the processing routine of FIG. 8 is that the processing of S201 to S205 is executed instead of the processing of S105 to S109.

  Specifically, after executing the compression ratio switching process in the process of S104, the ECU 100 proceeds to the process of S201, and the measured value (intake air quantity) of the air flow meter 101 is read in the process of S103. So that the opening degree of the throttle valve 402 is increased.

  In the process of S202, the ECU 100 determines whether the measured value (intake air amount) of the air flow meter 101 is equal to the intake air amount mc0 read in the process of S103. If a negative determination is made in the process of S202, the ECU 100 returns to the process of S201. On the other hand, if a positive determination is made in the process of S202, the ECU 100 proceeds to the process of S203. The ECU 100 executes the process of S201 and the process of S202, thereby realizing the “intake amount control means” according to the present invention.

  In the process of S203, the ECU 100 reads the measured value (switched intake pressure) Pm2 of the intake pressure sensor 403. Subsequently, the ECU 100 proceeds to the process of S204, and the measured value (pre-switching intake pressure) Pm1 of the intake pressure sensor 403 read in the process of S103 and the post-switching intake pressure Pm2 read in the process of S203. , The intake pressure difference ΔPm is obtained.

  In the process of S205, the ECU 100 determines whether or not the intake pressure difference ΔPm calculated in the process of S204 is greater than or equal to the intake pressure difference threshold value ΔPmthre. The intake pressure difference threshold value ΔPmthre referred to here is an intake pressure difference when the variable compression ratio mechanism is normal, or a value obtained by subtracting a margin considering variations of various sensors from the intake pressure difference. If an affirmative determination is made in S205, the ECU 100 proceeds to the process of S110 and diagnoses that the variable compression ratio mechanism is normal. On the other hand, if a negative determination is made in step S205, the ECU 100 proceeds to step S111 and diagnoses that the variable compression ratio mechanism is abnormal.

  When the abnormality diagnosis of the variable compression ratio mechanism is executed according to the procedure described above, the difference between the intake pressure difference when the variable compression ratio mechanism is normal and the intake pressure difference when the variable compression ratio mechanism is abnormal. In addition, since a difference to the extent that a highly accurate diagnosis can be made occurs, an abnormality diagnosis of the variable compression ratio mechanism can be performed with high accuracy. Further, according to the above-described procedure, the intake air amount before and after the execution of the compression ratio switching process is equalized, so that it is possible to suppress the occurrence of torque fluctuation accompanying the execution of the compression ratio switching process.

  In this embodiment, the example in which the difference in intake pressure before and after the execution of the compression ratio switching process (intake pressure difference) is used as a parameter has been described. However, the rate of change of the intake pressure before and after the execution of the compression ratio switching process ((( (Intake pressure after switching) − (Intake pressure before switching) / (Intake pressure before switching)) may be used as a parameter. If the intake manifold pressure at the time of executing the compression ratio switching process is relatively high, an abnormality diagnosis of the variable compression ratio mechanism is performed using the intake pressure difference as a parameter, and the intake manifold pressure at the time of executing the compression ratio switching process is relatively low. In this case, the abnormality diagnosis of the variable compression ratio mechanism may be performed using the change rate of the intake pressure as a parameter.

<Other embodiments>
In the first and second embodiments described above, an example in which the throttle valve 402 is used as the “regulator” according to the present invention has been described. However, in an internal combustion engine equipped with an exhaust turbine supercharger (turbocharger), a turbine is used. The waste gate valve provided in the door may be used as an “adjusting device” according to the present invention.

  In the first and second embodiments described above, the variable compression ratio mechanism capable of switching the compression ratio to two stages of the first compression ratio and the second compression ratio is exemplified, but the compression ratio is increased to three or more stages. The abnormality diagnosis of the present invention can also be applied to a switchable variable compression ratio mechanism.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Variable length connecting rod 8 Spark plug 10a Variable valve mechanism 31 Connecting rod main body 31a Large end 31b Small end 32 Eccentric member 32a Sleeve 35 Switching mechanism 41 Crank receiving opening 42 Sleeve receiving opening 75 OSV
100 ECU
101 Air Flow Meter 400 Intake Manifold 403 Intake Pressure Sensor

Claims (2)

An abnormality diagnosis device applied to a variable compression ratio mechanism capable of switching a mechanical compression ratio of an internal combustion engine to at least two stages,
The internal combustion engine
A variable valve mechanism that can change the closing timing of the intake valve;
An intake pressure sensor for detecting the intake pressure in the intake manifold;
An intake air amount sensor for detecting an intake air amount of the internal combustion engine;
An adjusting device for adjusting the amount of intake air supplied to the intake manifold;
With
The abnormality diagnosis device includes:
The variable valve mechanism so that the intake pressure of the intake manifold is larger than when the expansion ratio of the internal combustion engine is larger than the effective compression ratio and the expansion ratio of the internal combustion engine is equal to the effective compression ratio. Expansion ratio control means for operating the internal combustion engine at a high expansion ratio by controlling the adjusting device;
Compression ratio control means for controlling the variable compression ratio mechanism to switch the mechanical compression ratio of the internal combustion engine when the internal combustion engine is operating at a high expansion ratio;
The measured value of the intake pressure sensor after the mechanical compression ratio switching control by the compression ratio control means is executed is the measured value of the intake pressure sensor before the mechanical compression ratio switching control by the compression ratio control means is executed. An intake pressure control means for controlling the adjusting device so as to be equivalent to a measured value;
The measured value of the intake pressure sensor after the mechanical compression ratio switching control by the compression ratio control means is executed is measured by the intake pressure sensor before the mechanical compression ratio switching control by the compression ratio control means is executed. The difference between the measured value of the intake air amount sensor when it is equal to the value and the measured value of the intake air amount sensor before execution of the mechanical compression ratio switching control by the compression ratio control means is a predetermined value. If it is less than the intake air amount difference threshold, it is diagnosed that the variable compression ratio mechanism is abnormal, and if the difference is greater than or equal to the predetermined intake air amount difference threshold, the variable compression ratio mechanism is normal. Diagnostic means to diagnose;
An abnormality diagnosis device for a variable compression ratio mechanism, comprising: An abnormality diagnosis device applied to a variable compression ratio mechanism capable of switching a mechanical compression ratio of an internal combustion engine to at least two stages,
The internal combustion engine
A variable valve mechanism that can change the closing timing of the intake valve;
An intake pressure sensor for detecting the intake pressure in the intake manifold;
An intake air amount sensor for detecting an intake air amount of the internal combustion engine;
An adjusting device for adjusting the amount of intake air supplied to the intake manifold;
With
The abnormality diagnosis device includes:
The variable valve mechanism so that the intake pressure of the intake manifold is larger than when the expansion ratio of the internal combustion engine is larger than the effective compression ratio and the expansion ratio of the internal combustion engine is equal to the effective compression ratio. Expansion ratio control means for operating the internal combustion engine at a high expansion ratio by controlling the adjusting device;
Compression ratio control means for controlling the variable compression ratio mechanism to switch the mechanical compression ratio of the internal combustion engine when the internal combustion engine is operating at a high expansion ratio;
The measured value of the intake air amount sensor after the mechanical compression ratio switching control by the compression ratio control unit is executed is the measured value of the intake air amount sensor before the mechanical compression ratio switching control by the compression ratio control unit is executed. An intake air amount control means for controlling the adjusting device so as to be equivalent to a measured value;
The measured value of the intake air amount sensor after the mechanical compression ratio switching control by the compression ratio control unit is executed is measured by the intake air amount sensor before the mechanical compression ratio switching control by the compression ratio control unit is executed. The difference between the measured value of the intake pressure sensor when the value is equal to the measured value and the measured value of the intake pressure sensor before the mechanical compression ratio switching control by the compression ratio control means is executed is a predetermined value. If the difference is less than the intake pressure difference threshold, the variable compression ratio mechanism is diagnosed as abnormal, and if the difference is greater than or equal to the predetermined intake pressure difference threshold, the variable compression ratio mechanism is normal. Diagnostic means to diagnose;
An abnormality diagnosis device for a variable compression ratio mechanism, comprising:

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