JP2018009524A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve abnormality detection accuracy of a variable compression ratio mechanism.SOLUTION: A control device for controlling an internal combustion engine equipped with a variable compression ratio mechanism which can vary a compression ratio for each cylinder of the internal combustion engine having a plurality of cylinders includes an in-cylinder pressure sensor provided for each of the cylinders so as to detect a pressure in the cylinder, an ignition delay calculating section for calculating physical quantity having a correlation with an ignition delay of each of the cylinders based on the pressure in the cylinder detected by the in-cylinder pressure sensor, and a detecting section for detecting abnormality of the variable compression ratio mechanism based on the physical quantity calculated by the ignition delay calculating section.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a control device for an internal combustion engine.

  An in-cylinder pressure sensor that detects the pressure in the cylinder of the internal combustion engine, and compares the average value of all the cylinder pressures at a predetermined crank angle with the in-cylinder pressure of each cylinder at a predetermined crank angle. There is known a technique for detecting the variation in (see, for example, Patent Document 1).

JP-A-01-106958 Japanese Patent Laying-Open No. 2015-094339 Japanese Patent Laid-Open No. 2006-118181

  Here, the sensitivity of the in-cylinder pressure sensor changes due to secular change or deposit adhesion. That is, the in-cylinder pressure detected by the in-cylinder pressure sensor is affected by the sensitivity change. Therefore, when the detection value of the in-cylinder pressure sensor varies, it may be difficult to distinguish whether it is due to variations in the compression ratio or due to a change in sensitivity of the in-cylinder pressure sensor.

  The present invention has been made in view of the above-described problems, and an object thereof is to improve the accuracy of abnormality detection of the variable compression ratio mechanism.

  In order to solve the above problems, in a control device for controlling an internal combustion engine having a variable compression ratio mechanism capable of changing the compression ratio for each cylinder of the internal combustion engine having a plurality of cylinders, the pressure in each cylinder is provided in each cylinder. An in-cylinder pressure sensor for detecting the in-cylinder pressure, an ignition delay calculating unit for calculating a physical quantity correlated with the ignition delay of each cylinder based on the pressure in the cylinder detected by the in-cylinder pressure sensor, and the ignition delay calculating unit A detection unit that detects an abnormality of the variable compression ratio mechanism based on the calculated physical quantity.

  According to the present invention, it is possible to improve the accuracy of abnormality detection of the variable compression ratio mechanism.

It is a figure which shows schematic structure of the internal combustion engine which concerns on an Example, and its intake / exhaust system. It is a figure which shows the cross-sectional schematic diagram of the internal combustion engine which concerns on an Example. It is a figure shown about the structure of the variable-length connecting rod which concerns on an Example. It is a figure which shows the switching mechanism of the 1st state which concerns on an Example. It is a figure which shows the switching mechanism of the 2nd state which concerns on an Example. It is the figure which showed the relationship between a crank angle and a cylinder pressure. It is the figure which showed the relationship between ignition delay and internal EGR gas amount. It is the figure which showed the relationship between internal EGR gas amount and compression ratio. 3 is a flowchart illustrating a flow for detecting an abnormality of the variable-length connecting rod according to the first embodiment. It is a time chart which showed transition of compression ratio. It is the flowchart which showed the flow for detecting abnormality of a variable-length connecting rod, implementing the combustion control which concerns on Example 2. FIG. 6 is a flowchart illustrating a flow of abnormality detection of a variable compression ratio mechanism according to a second embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

<Example 1>
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a spark ignition type internal combustion engine (gasoline engine) having four cylinders 2. Each cylinder 2 of the internal combustion engine 1 is provided with a fuel injection valve 3 for directly injecting fuel into each cylinder 2 and an ignition plug 4 for igniting an air-fuel mixture. Each cylinder 2 of the internal combustion engine 1 is provided with an in-cylinder pressure sensor 102 that detects the pressure in each cylinder 2. Note that the in-cylinder pressure sensor 102 can be omitted in the present embodiment and in Embodiment 2 described later. Here, in the internal combustion engine 1, in one operating cycle (crank angle 720 °), combustion in the cylinder 2 is performed in the order of # 1 cylinder, # 3 cylinder, # 4 cylinder, and # 2 cylinder.

  An intake passage 400 and an exhaust passage 500 are connected to the internal combustion engine 1. An air flow meter 401 and a throttle 402 are provided in the intake passage 400. The air flow meter 401 outputs an electrical signal corresponding to the amount (mass) of intake air (air) flowing through the intake passage 400. The throttle 402 is disposed downstream of the air flow meter 401 in the intake passage 400. The throttle 402 adjusts the intake air amount of the internal combustion engine 1 by changing the passage cross-sectional area in the intake passage 400. The exhaust passage 500 is opened to the atmosphere via a catalyst and a silencer (not shown).

  Furthermore, the cross-sectional schematic diagram of the internal combustion engine 1 is shown in FIG. FIG. 2 is a schematic cross-sectional view of the internal combustion engine 1 taken along the line SS of FIG. As shown in FIG. 2, the internal combustion engine 1 includes a cylinder block 7 and a cylinder head 8. A crankshaft 200 is rotatably accommodated in the cylinder block 7. A cylindrical cylinder 2 is formed in the cylinder block 7. A piston 5 is slidably accommodated in the cylinder 2. 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 8. The cylinder head 8 includes an intake valve 9 for opening and closing the opening end of the intake port 11 in the combustion chamber 300 and an intake camshaft 10 for opening and closing the intake valve 9. In addition, the cylinder head 8 includes an exhaust valve 12 for opening and closing the opening end of the exhaust port 14 in the combustion chamber 300, and an exhaust camshaft 13 for opening and closing the exhaust valve 12. Further, the cylinder head 8 includes a fuel injection valve 3 that directly injects fuel into the combustion chamber 300 and an ignition plug 4 for igniting the air-fuel mixture in the combustion chamber 300.

  Here, the variable length connecting rod 6 is connected to the piston 5 by a piston pin 21 at a small end portion thereof, and is connected to the crank pin 22 of the crankshaft 200 at a large end portion thereof. The variable length connecting rod 6 can 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 increased, the length from the axis of the crank pin 22 to the axis of the piston pin 21 is increased, so that the piston 5 is at the top dead center as shown by the solid line in FIG. When the volume of the combustion chamber 300 becomes small. 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 is at the top dead center as shown by the broken line in FIG. The volume of the combustion chamber 300 when it is at 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 ratio (mechanical compression ratio) with the in-cylinder volume at the time when is located at the bottom dead center changes.

(Configuration of variable length connecting rod 6)
Here, the structure of the variable-length connecting rod 6 in a present Example 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 on the connecting rod body 31, and a second provided on the connecting rod body 31. A piston mechanism 34 and a switching mechanism 35 that switches the flow of hydraulic oil to the piston mechanisms 33 and 34 are provided.

  The connecting rod body 31 has a crank receiving opening 41 for receiving the crankpin 22 of the crankshaft 200 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). An imaginary straight line extending between the axial center of the variable-length connecting rod 6 and the axis of the sleeve is referred to as an axis X 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 cylindrical piston pin receiving opening 32d is formed such that its axis is eccentric with respect to the axis of the sleeve 32a.

Thus, in this embodiment, since the axis of the piston pin receiving opening 32d of the sleeve 32a is eccentric from the axis of the sleeve 32a, when the eccentric member 32 rotates, the piston pin receiving opening in the sleeve receiving opening 42 is rotated. The position of 32d changes. When the position of the piston pin receiving opening 32d is on the large end portion 31a side in the sleeve receiving opening 42, the effective length of the connecting rod is shortened. Conversely, when the position of the piston pin receiving opening 32d is in the sleeve receiving opening 42 on the side opposite to the large end portion 31a side, the effective length of the connecting rod is increased.
Therefore, according to this embodiment, the effective length of the connecting rod can be changed by rotating the eccentric member 32.

  Next, the first piston mechanism 33 includes a first cylinder 33a formed on the connecting rod body 31 and a first piston 33b that slides within the first cylinder 33a. Most or all of the first cylinder 33a is arranged on the first arm 32b side with respect to the axis X of the connecting rod. In addition, the first cylinder 33a is arranged 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 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 second piston mechanism 34 has a second cylinder 34a formed in the connecting rod body 31 and a second piston 34b that slides in the second cylinder 34a. Most or all of the second cylinder 34a is disposed on the second arm 32c side with respect to the axis X of the connecting rod. In addition, 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 hydraulic oil to flow from the second cylinder 34a to the first cylinder 33a. The first state to be switched and the second state that allows the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and blocks the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. 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 raises and the 1st arm 32b of the eccentric member 32 connected with 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 held at that position.

When the switching mechanism 35 is in the first state, basically, the first piston 33b and the second piston 34b move to the positions described above without supplying hydraulic oil from the outside. This is because when the piston 5 reciprocates in the cylinder 2 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 2 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 300 and a downward force acts on the piston 5. In this case, a force for pushing the first piston 33b is applied, but the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a is blocked by the switching mechanism 35, so that the hydraulic oil in the first cylinder 33a flows out. 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 rises 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. 3, 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 held at that position. 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 first state is referred to as a first compression ratio, and the mechanical compression ratio when the switching mechanism 35 is in the second state is referred to as a second compression ratio. The first compression ratio is greater than the second compression ratio.

  Even when the switching mechanism 35 is in the second state, basically, the first piston 33b and the second piston 34b move to the positions described above without supplying hydraulic oil from the outside. This is because when the piston 5 reciprocates in the cylinder 2 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 300 and the downward force is exerted on the piston 5. This is because the first piston 33b is pushed in when acted, and 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 2 of the internal combustion engine 1 and an upward inertial force is applied to the piston 5, a force that pushes the second piston 34b works. Since the flow of hydraulic oil to the one cylinder 33a is blocked, the hydraulic oil in the second cylinder 34a does not flow out, and therefore the second piston 34b is not pushed in.

(Configuration of switching mechanism 35)
Next, one embodiment of the switching mechanism 35 will be described with reference to FIGS. 4 shows the switching mechanism 35 in the first state, and FIG. 5 shows the switching mechanism 35 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.

  One switching pin 61 (first switching pin 61) of the two switching pins 61, 62 described above has two circumferential grooves 61a, 61b extending in the circumferential direction thereof. 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. A first biasing spring 67 for biasing the first switching pin 61 is housed in the first pin housing space 64 that houses the first switching pin 61.

  The other switching pin 62 (second switching pin 62) of the two switching pins 61 and 62 described above 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 through a communication path 62 c formed in the second switching pin 62. A second biasing spring 68 for biasing the second switching pin 62 is also housed in the second pin housing space 65 that houses the second switching pin 62.

  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. 4) to the secondary side (lower side in FIG. 4) 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 accommodation space 64 and the secondary side of the check valve accommodation 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 accommodation 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. Among these, one third space communication oil passage 55 communicates the second pin accommodation space 65 and 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.

  Further, the first pin housing space 64 communicates with a first control oil passage 57 formed in the connecting rod body 31. At this time, the first control oil passage 57 is communicated with the first pin housing space 64 at the end opposite to the end where the first biasing spring 67 is provided. The second pin housing space 65 communicates with a second control oil passage 58 formed in the connecting rod body 31. At this time, the second control oil passage 58 is communicated with the second pin housing space 65 at the end opposite to the end provided with the second urging spring 68. 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. And communicated with an external switching valve (OSV) 75. The switching valve 75 here is, for example, a valve mechanism that switches between conduction and cutoff 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 switching valve 75 connects the control oil passages 57, 58 and the hydraulic oil supply source 76, as shown in FIG. Since the urging springs 67 and 68 are contracted by the hydraulic pressure acting on 62, the switching pins 61 and 62 are connected to the first piston communication oil passage 51 and the first space communication oil passage via the communication passage 61c of the first switching pin 61. 53, and the second piston communication oil passage 52 and the fourth space communication oil passage 56 are moved and held at a position where they can communicate with each other via the communication passage 62c of the second switching pin 62. In that case, the first cylinder 33 a is connected to the secondary side of the check valve 63, and the second cylinder 34 a is connected to the primary side of the check valve 63. Therefore, the hydraulic oil in the second cylinder 34 a passes through the second 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. Although it becomes possible to move to 33a, the hydraulic oil in the first cylinder 33a cannot move to the second cylinder 34a. Therefore, when the switching valve 75 connects the control oil passages 57 and 58 and the hydraulic oil supply source 76, the switching mechanism 35 blocks the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a. And it will be in the state (first state) which permits the flow of hydraulic oil from the 2nd cylinder 34a to the 1st cylinder 33a.

On the other hand, when the switching valve 75 blocks the control oil passages 57, 58 and the hydraulic oil supply source 76, the biasing springs 67, 68 extend as shown in FIG. , 62 is 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 via the communication passage 62 c of the second switching pin 62. 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. 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. Although it becomes possible to move to 34a, the hydraulic oil in the second cylinder 34a cannot move to the first cylinder 33a. Therefore, when the switching valve 75 blocks the control oil passages 57, 58 and the hydraulic oil supply source 76, the switching mechanism 35 allows the hydraulic oil to flow from the first cylinder 33a to the second cylinder 34a. And it will be in the state (2nd state) which interrupts | blocks the flow of the hydraulic fluid from the 2nd cylinder 34a to the 1st cylinder 33a.

  As described above, when the switching of the hydraulic pressure to the first pin accommodating space 64 and the second pin accommodating space 65 is switched by the switching valve 75, 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 (high compression ratio) or the second compression ratio (low compression ratio).

  Here, referring back to FIG. 1, an electronic control unit (ECU) 100 is additionally provided in the internal combustion engine 1 configured as described above. The ECU 100 is a unit that controls the operating state and the like of the internal combustion engine 1. In addition to the air flow meter 401 and the in-cylinder pressure sensor 102, the ECU 100 is electrically connected to various sensors such as an accelerator position sensor 201 and a crank position sensor 202. The accelerator position sensor 201 is a sensor that outputs an electrical signal correlated with the amount of operation of the accelerator pedal (accelerator opening). The crank position sensor 202 is a sensor that outputs an electrical signal correlated with the rotational position of the engine output shaft (crankshaft) of the internal combustion engine 1. Then, the output signals of these sensors are input to the ECU 100. ECU 100 derives the engine load of internal combustion engine 1 based on the output signal of accelerator position sensor 201. Further, the ECU 100 derives the engine speed of the internal combustion engine 1 based on the output signal of the crank position sensor 202.

  Various devices such as the fuel injection valve 3, the spark plug 4, the throttle 402, and the switching valve 75 are electrically connected to the ECU 100. These various devices are controlled by the ECU 100. For example, the ECU 100 controls the switching valve 75 according to the engine load. Specifically, when the engine load is less than a predetermined threshold, the ECU 100 sets the mechanical compression ratio of the internal combustion engine 1 to the first compression ratio (the switching mechanism 35 is in the first state, that is, the high compression ratio state). The switching valve 75 is controlled as follows. On the other hand, when the engine load is equal to or greater than the predetermined threshold, the ECU 100 sets the mechanical compression ratio of the internal combustion engine 1 to the second compression ratio (the switching mechanism 35 is in the second state, that is, the low compression ratio state is The switching valve 75 is controlled as follows. In the internal combustion engine 1 according to this embodiment in which the top dead center position of the piston 5 accommodated in each cylinder 2 is changed by the change in the effective length of the variable length connecting rod 6, the variable length connecting rod 6 of each cylinder 2 is changed. By providing the switching valve 75 for each, the mechanical compression ratio can be changed for each of the cylinders 2. In this embodiment, the variable length connecting rod 6 corresponds to the variable compression ratio mechanism in the present invention.

Further, the ECU 100 detects an abnormality of the variable length connecting rod 6 based on the detection value of the in-cylinder pressure sensor 102. In order to detect an abnormality in the variable-length connecting rod 6, the ECU 100 calculates a physical quantity that is correlated with the ignition delay in each cylinder 2 based on the detection value of the in-cylinder pressure sensor 102. Here, FIG. 6 is a diagram showing the relationship between the crank angle and the in-cylinder pressure. In FIG. 6, SA indicates the ignition timing by the spark plug 4, and PMAX indicates the timing when the in-cylinder pressure becomes maximum. In this embodiment, in each cylinder 2, the crank angle from the ignition timing by the spark plug 4 to the timing when the in-cylinder pressure becomes maximum is calculated as a physical quantity correlated with the ignition delay. In this embodiment, the crank angle from the ignition timing by the spark plug 4 to the timing at which the in-cylinder pressure becomes maximum is simply referred to as ignition delay. That is, the ECU 100 calculates the ignition delay DI by the following formula.
DI = PMAX-SA
In this embodiment, the ECU 100 functions as an ignition delay calculation unit according to the present invention by calculating the ignition delay. Hereinafter, the ignition delay of the #i cylinder is DI (#i). #I is any cylinder 2 from # 1 cylinder to # 4 cylinder. The ignition timing by the spark plug 4 is set by the ECU 100 according to, for example, the engine speed and the engine load. It can be said that the ignition delay DI is a value that is not affected by a change in sensitivity of the in-cylinder pressure sensor 102. That is, even when the maximum pressure detected by the sensitivity of the in-cylinder pressure sensor 102 changes, the timing at which the maximum pressure is detected does not change, and therefore, from the ignition timing by the spark plug 4 to the timing at which the in-cylinder pressure becomes maximum. The crank angle does not change.

  The ignition delay calculated in this way is correlated with the compression ratio. Here, FIG. 7 is a diagram showing the relationship between the ignition delay and the internal EGR gas amount. Thus, there is a correlation between the ignition delay and the internal EGR gas amount, and it can be said that the larger the ignition delay, the larger the internal EGR gas amount. FIG. 8 is a diagram showing the relationship between the internal EGR gas amount and the compression ratio. There is a correlation system between the internal EGR gas amount and the compression ratio, and it can be said that the compression ratio decreases as the internal EGR gas amount increases. That is, as the compression ratio decreases, the volume of the combustion chamber 300 when the piston 5 is located at TDC increases. Depending on the volume of the combustion chamber 300, the amount of internal EGR gas also increases. From this relationship, it can be said that the greater the ignition delay, the lower the compression ratio.

  From the above, the ECU 100 according to the present embodiment calculates the ignition delay DI (#i) of each cylinder 2, and further calculates the average ignition delay DI_AVE that is the average value of the ignition delays of all the cylinders 2. The ignition delay DI (#i) and the average ignition delay DI_AVE are compared to detect an abnormality in the compression ratio. That is, by comparing the ignition delay DI (#i) of each cylinder 2 correlated with the compression ratio of each cylinder 2 with the average ignition delay DI_AVE, the cylinder 2 in which the ignition delay greatly deviates from the other cylinders 2 is obtained. The cylinder 2 is detected as having an abnormality in the variable compression ratio mechanism.

  FIG. 9 is a flowchart showing a flow for detecting an abnormality of the variable-length connecting rod 6 according to the present embodiment. This flowchart is executed by the ECU 100, for example, every 720 degrees in crank angle. That is, it is executed every time in-cylinder pressure data is obtained in all cylinders 2.

  In step S101, in-cylinder pressure data of each cylinder 2 is read. The ECU 100 stores the detection value of the in-cylinder pressure sensor 102 for each cylinder 2 in association with the crank angle for each cycle. In step S101, the data is read.

  In step S102, the ignition timing SA of each cylinder 2 is read. The ECU 100 stores the ignition timing SA of each cylinder 2 in association with the crank angle for each cycle. In step S101, the data is read.

  In step S103, the ignition delay DI (#i) of each cylinder 2 is calculated. The ECU 100 calculates the ignition delay DI (#i) of each cylinder 2 by subtracting the ignition timing SA read in step S102 from the maximum value of the in-cylinder pressure data read in step S101 for each cylinder 2. To do. In the present embodiment, the ECU 100 calculates the ignition delay DI (#i), thereby functioning as an ignition delay calculation unit in the present invention.

In step S104, an average ignition delay DI_AVE is calculated. The ECU 100 calculates the average value of the ignition delay DI (#i) of each cylinder 2 calculated in step S104. Thereafter, in step S105, 1 is assigned to #i.

  In step S106, it is determined whether or not a value (DI (#i) -DI_AVE) obtained by subtracting the average ignition delay DI_AVE from the ignition delay DI (#i) is equal to or greater than the threshold value A1. The threshold value A1 is (DI (#i) -DI_AVE) when the compression ratio is shifted to a lower side than a normal range. In step S106, it can be said that it is determined whether or not the compression ratio of the #i cylinder is shifted to a lower side than the normal range. The threshold A1 is obtained in advance by experiments or simulations. If an affirmative determination is made in step S106, the process proceeds to step S107. On the other hand, if a negative determination is made, the process proceeds to step S109.

  In step S107, it is determined that the internal EGR gas amount of the #i cylinder is larger than the normal range. In step S108, it is determined that the compression ratio of the #i cylinder is shifted to a lower side than a normal range.

  On the other hand, in step S109, it is determined whether or not a value (DI (#i) −DI_AVE) obtained by subtracting the average ignition delay DI_AVE from the ignition delay DI (#i) is equal to or less than the threshold value B1. The threshold value B1 is a negative value (DI (#i) −DI_AVE) when the compression ratio is shifted to a higher side than a normal range. In this step S109, it can be said that it is determined whether or not the compression ratio of the #i cylinder is shifted to a higher side than the normal range. The threshold value B1 is obtained in advance by experiments or simulations. If an affirmative determination is made in step S109, the process proceeds to step S110. On the other hand, if a negative determination is made, the process proceeds to step S112. If a negative determination is made in step S109, there is no abnormality in the variable compression ratio mechanism.

  In step S110, it is determined that the internal EGR gas amount of the #i cylinder is less than the normal range. In step S111, it is determined that the compression ratio of the #i cylinder is shifted to a higher side than the normal range.

  In step S112, a value obtained by adding 1 to #i is set as a new #i. In step S113, it is determined whether or not #i is larger than the number of cylinders 2 of the internal combustion engine 1. In step S113, it is determined whether or not the comparison with the average ignition delay DI_AVE has been completed for all the cylinders. In this embodiment, the ECU 100 functions as a detection unit in the present invention by processing steps S105 to S113.

  As described above, according to this embodiment, an abnormality in the compression ratio of each cylinder 2 can be detected based on the ignition delay of each cylinder 2 that is not affected by the change in sensitivity of the in-cylinder pressure sensor 102. For this reason, the accuracy of abnormality detection of the variable compression ratio mechanism can be improved.

  In the present embodiment, the ignition delay DI (#i) is compared with the average ignition delay DI_AVE, but instead, the ignition delay DI (#i) may be compared with a normal value. This normal value is obtained in advance through experiments or simulations and stored in the ECU 100 via a map. In the present embodiment, the time PMAX when the in-cylinder pressure becomes maximum is used when obtaining the ignition delay DI (#i), but other time can be used instead. This time may be obtained by experiment or simulation as a time correlated with the ignition delay. In the present embodiment, the variable compression ratio mechanism having the structure shown in FIGS. 2 to 5 has been described. Instead, the variable compression ratio mechanism having another structure capable of changing the compression ratio for each cylinder. Is also applicable.

<Example 2>
In this embodiment, combustion control using the in-cylinder pressure sensor 102 is performed when the compression ratio is changed, and abnormality detection of the variable compression ratio mechanism is performed when a predetermined period has elapsed after completion of the change of the compression ratio. Since other devices are the same as those in the first embodiment, the description thereof is omitted.

  Here, since the volume of the combustion chamber 300 changes during the change of the compression ratio, the internal EGR gas amount changes. When each cylinder 2 is provided with a variable compression ratio mechanism that can change the compression ratio, the change speed of the compression ratio may differ for each cylinder 2 depending on the hydraulic pressure supplied to the variable length connecting rod 6 and the secular change. . As a result, the internal EGR gas amount may be different for each cylinder 2 during the change of the compression ratio. As a result, there is a possibility that torque fluctuations increase due to variations in the combustion state. In this case, since the in-cylinder pressure varies for each cylinder 2, the ignition delay calculated based on the in-cylinder pressure also varies. When abnormality detection of the variable compression ratio mechanism is performed based on such ignition delay, there is a risk of erroneous determination.

  Therefore, in this embodiment, the fuel injection amount feedback control is performed based on the detected value of the in-cylinder pressure sensor 102 from the start of the change of the compression ratio until a predetermined period after the change is completed, thereby combusting between the cylinders 2. Reduce variation. It should be noted that the compression ratio change speed varies from cylinder 2 to cylinder 2 and it is difficult to actually detect the compression ratio change speed, so there is a margin as to the period until the compression ratio is completed in all cylinders 2. A predetermined period is set.

  FIG. 10 is a time chart showing the transition of the compression ratio. TA is the start of changing the compression ratio, and TB is the time when a predetermined period has elapsed since the change of the compression ratio was completed. TB is a point in time at which it is considered that the change of the compression ratio has been completed even if the change speed of the compression ratio has decreased. The solid line shows the case when the compression ratio is normal and the compression ratio change rate is standard, and the broken line shows the case when the compression ratio is normal and the compression ratio change speed is faster than the standard case. The alternate long and short dash line indicates a case where an abnormality that is lower than that in the case where the compression ratio is normal occurs and the change rate of the compression ratio is lower than that in the standard case. In the present embodiment, during the period from TA to TB, the fuel injection amount feedback control (hereinafter also referred to as combustion control) is performed based on the detection value of the in-cylinder pressure sensor 102.

  By implementing such combustion control, an increase in torque fluctuation is suppressed. Here, the ignition delay DI (#i) of each cylinder 2 has a correlation with the internal EGR gas amount and has a correlation with the compression ratio. For example, when the compression ratio becomes low, the amount of internal EGR gas increases, so that the ignition delay DI (#i) becomes large. For this reason, the ignition delay DI (#i) of each cylinder 2 can be used as an indicator of the combustion state in each cylinder 2. Therefore, in this embodiment, the fuel injection amount is feedback-controlled so that the ignition delay DI (#i) of each cylinder 2 approaches the target ignition delay DI_TR, thereby suppressing variation in the combustion state and increasing torque fluctuation. Suppress. For example, when the ignition delay DI is larger than the target ignition delay DI_TR, it is considered that the ignition delay DI is increased due to an increase in the internal EGR gas amount. In this case, the ignition delay DI is reduced by increasing the fuel injection amount. On the other hand, when the ignition delay DI is smaller than the target ignition delay DI_TR, it is considered that the ignition delay is reduced due to a decrease in the internal EGR gas amount. In this case, the ignition delay DI is increased by reducing the fuel injection amount.

  Further, the difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR when the combustion control is performed is the actual internal EGR gas amount and normal internal EGR gas amount of each cylinder 2. Is correlated with the difference between the actual compression ratio of each cylinder 2 and the compression ratio at the normal time. Therefore, the abnormality of the variable compression ratio mechanism in each cylinder 2 can be detected according to the difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR.

FIG. 11 is a flowchart showing a flow for detecting abnormality of the variable length connecting rod 6 while performing the combustion control according to the present embodiment. This flowchart is executed by the ECU 100 every 720 degrees, for example, at a crank angle after the start of changing the compression ratio. Steps in which the same processing as in the flowchart shown in FIG. 9 is performed are denoted by the same reference numerals and description thereof is omitted.

  In step S201, it is determined whether or not a predetermined period has elapsed since the completion of changing the compression ratio. If an affirmative determination is made in step S201, the process proceeds to step S205, whereas if a negative determination is made, the process proceeds to step S202. If a negative determination is made in step S201, the combustion control is performed within the period from TA to TB in FIG.

  In step S202, a target ignition delay DI_TR is calculated. The target ignition delay DI_TR is obtained in advance through experiments or simulations, mapped, and stored in the ECU 100. When step S202 is completed, steps S101 to S103 are processed, and then the process proceeds to step S203.

  In step S203, the difference (RI (#i) = DI (#i) −DI_TR) between the ignition delay DI (#i) and the target ignition delay DI_TR is calculated.

  In step S204, the fuel injection amount is corrected based on the difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR. In step S204, the correction amount of the fuel injection amount is determined so that the difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR is eliminated. For example, the fuel injection amount may be corrected by PI control.

  On the other hand, in step S205, abnormality detection of the variable compression ratio mechanism is performed. Here, FIG. 12 is a flowchart showing a flow of abnormality detection of the variable compression ratio mechanism according to the present embodiment. The flowchart shown in FIG. 12 is executed by the ECU 100 in step S205. In addition, about the step in which the same process as the flowchart shown in FIG. 9 is made, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the flowchart shown in FIG. 12, when the process of step S105 is completed, the process proceeds to step S301. In step S301, it is determined whether or not the difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR is greater than or equal to the threshold value C1. The threshold value C1 is a difference RI (#i) when the compression ratio is shifted to a lower side than a range where it can be said that the compression ratio is normal. In this step S301, it can be said that it is determined whether or not the compression ratio of the #i cylinder is shifted to a lower side than the normal range. The threshold value C1 is obtained in advance by experiments or simulations. If an affirmative determination is made in step S301, the process proceeds to step S107. On the other hand, if a negative determination is made, the process proceeds to step S302.

  In step S302, it is determined whether or not a difference RI (#i) between the ignition delay DI (#i) and the target ignition delay DI_TR is equal to or less than a threshold value D1. The threshold value D1 is a negative value and is a difference RI (#i) when the compression ratio is shifted to a higher side than a normal range. In step S302, it can be said that it is determined whether or not the compression ratio of the #i cylinder is shifted to a higher side than the normal range. The threshold value D1 is obtained in advance by experiments or simulations. If an affirmative determination is made in step S302, the process proceeds to step S110. On the other hand, if a negative determination is made, the process proceeds to step S112.

  If an affirmative determination is made in step S113, the process returns to the flowchart of FIG. 11 and proceeds to step S206. In step S206, the correction of the fuel injection amount according to this embodiment, that is, the combustion control is terminated. After step S206 is processed, the ECU 100 ends the repeated execution of the flowchart, and the flowchart is not executed until the next change of the compression ratio.

  As described above, according to this embodiment, the combustion control using the in-cylinder pressure sensor 102 can be performed when the compression ratio is changed to suppress the variation between the cylinders in the combustion state. Then, when a predetermined period has elapsed after completion of the change of the compression ratio, an abnormality in the compression ratio of each cylinder 2 can be detected based on the ignition delay of each cylinder 2 that is not affected by the change in sensitivity of the in-cylinder pressure sensor 102. For this reason, the accuracy of abnormality detection of the variable compression ratio mechanism can be improved. In the present embodiment, the combustion control is performed only during the period from TA to TB in FIG. 10, but instead of this, the combustion control may be performed constantly.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Fuel injection valve 4 Spark plug 5 Piston 6 Variable length connecting rod 7 Cylinder block 8 Cylinder head 21 Piston pin 22 Crank pin 31 Connecting rod main body 32 Eccentric member 35 Switching mechanism 75 Switching valve 76 Hydraulic oil supply source 100 ECU
102 In-cylinder pressure sensor 200 Crankshaft 201 Accelerator position sensor 202 Crank position sensor 300 Combustion chamber 400 Intake passage 401 Air flow meter 402 Throttle

Claims (1)

In a control device for controlling an internal combustion engine having a variable compression ratio mechanism capable of changing a compression ratio for each cylinder of an internal combustion engine having a plurality of cylinders,
An in-cylinder pressure sensor provided in each cylinder for detecting the pressure in the cylinder;
An ignition delay calculating unit that calculates a physical quantity correlated with the ignition delay of each cylinder based on the pressure in the cylinder detected by the in-cylinder pressure sensor;
A detection unit that detects an abnormality of the variable compression ratio mechanism based on the physical quantity calculated by the ignition delay calculation unit;
A control device for an internal combustion engine.

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