JP2018028292A - Abnormality diagnostic device for variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose an abnormality of a variable compression ratio mechanism by using a knock sensor in an abnormality diagnostic device for diagnosing an abnormality of the variable compression ratio mechanism that can switch a compression ratio of an internal combustion engine at least between two stages.SOLUTION: In an abnormality diagnostic device for a variable compression ratio mechanism that can switch a compression ratio of an internal combustion engine at least between a first compression ratio and a second compression ratio lower than the first compression ratio, when a predetermined period of time elapses after control of the variable compression ratio mechanism is started to switch the compression ratio from the first compression ratio to the second compression ratio, ignition timing of an ignition plug is changed to ignition timing for the second compression ratio, and based on knock strength at this time, an abnormality diagnosis of the variable compression ratio mechanism is made.SELECTED DRAWING: Figure 6

Description

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

  As a variable compression ratio mechanism of an internal combustion engine, a variable compression ratio mechanism that changes the mechanical compression ratio of the internal combustion engine by changing the effective length of the connecting rod and the height of the piston is known. In an internal combustion engine having such a variable compression ratio mechanism, a method for detecting an abnormality of the variable compression ratio mechanism by attaching a sensor for detecting a mechanical compression ratio has been proposed (see, for example, Patent Document 1). ).

Japanese Patent Laying-Open No. 2015-021433 Japanese Patent Laying-Open No. 2015-117852 JP 2006-161583 A Japanese Patent Laid-Open No. 2006-118181

  An object of the present invention is to provide a technique capable of diagnosing abnormality of a variable compression ratio mechanism using a knock sensor in a variable compression ratio mechanism for changing a mechanical compression ratio of an internal combustion engine.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides a variable compression ratio mechanism capable of switching a compression ratio of an internal combustion engine to at least a first compression ratio and a second compression ratio lower than the first compression ratio, and a knock sensor attached to the internal combustion engine. An ignition plug attached to each cylinder of the internal combustion engine, and a compression ratio control means for controlling the variable compression ratio mechanism so that the compression ratio of the internal combustion engine becomes a compression ratio according to the operating state of the internal combustion engine; , A variable compression ratio mechanism abnormality diagnosis device applied to an internal combustion engine. The abnormality diagnosis device is configured to control the compression ratio control when the compression ratio control unit controls the variable compression ratio mechanism to switch the compression ratio of the internal combustion engine from the first compression ratio to the second compression ratio. From the start of the control of the variable compression ratio mechanism by means until the predetermined period elapses, the ignition timing of the spark plug is set to the ignition timing for the second compression ratio which is an ignition timing suitable for the second compression ratio. Is set to the ignition timing for switching, which is the retarded ignition timing, and when the predetermined period has elapsed, the ignition timing of the spark plug is changed from the switching ignition timing to the second compression ratio ignition timing. The ignition timing control means to be changed, and when the ignition timing of the spark plug is changed from the switching ignition timing to the second compression ratio ignition timing by the ignition timing control means, based on the measured value of the knock sensor. There calculates the knock intensity, if the knock intensity is greater than a predetermined threshold value, the variable compression ratio mechanism is characterized in that it comprises a diagnostic means for diagnosing the abnormality.

Here, the “predetermined period” refers to a period required for the variable compression ratio mechanism to switch the compression ratio of the internal combustion engine from the first compression ratio to the second compression ratio, and other devices that affect the combustion state of the internal combustion engine ( For example, EGR device, variable valve mechanism, etc.) is an estimated value for the longest period of time required for switching from a state suitable for the first compression ratio to a state suitable for the second compression ratio. It shall be determined based on the results of experiments and simulations. Further, the “predetermined threshold value” here is that if the knock strength is larger than the predetermined threshold value, the cause of knocking is an abnormality of the variable compression ratio mechanism (for example, an abnormality in which the compression ratio is fixed to the first compression ratio). It is a value that can be determined as being in the combustion chamber, and a value that is larger than the knock intensity when a knock occurs due to deposit accumulation in the combustion chamber of the internal combustion engine or a change over time in the injection characteristics of the fuel injection valve. . This predetermined threshold value is determined in advance based on the results of experiments and simulations.

  The ignition timing control means may be configured such that the engine load factor of the internal combustion engine when the predetermined period has elapsed after the control of the variable compression ratio mechanism by the compression ratio control means is less than a predetermined load factor. Instead of changing the ignition timing of the spark plug from the switching ignition timing to the second compression ratio ignition timing, the switching ignition timing is more advanced than the second compression ratio ignition timing. You may make it change to the knock induction | guidance | derivation ignition timing which is an ignition timing. The diagnostic means calculates the knock intensity based on the measured value of the knock sensor when the ignition timing of the ignition plug is changed from the switching ignition timing to the knock induction ignition timing by the ignition timing control means. If the knock intensity is calculated and greater than the predetermined threshold value, the variable compression ratio mechanism may be diagnosed as abnormal.

  The “predetermined load factor” here means that if the engine load factor is less than the predetermined load factor, even if the variable compression ratio mechanism is abnormal, the knock strength may be less than the predetermined threshold value. This is an expected value, and is determined in advance based on the results of experiments and simulations.

  According to the present invention, abnormality of the variable compression ratio mechanism can be diagnosed using a knock sensor.

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. 6 is a timing chart showing changes over time in the engine load factor, compression ratio, ignition timing, and knock intensity when an abnormality in which the compression ratio cannot be switched from the first compression ratio to the second compression ratio occurs. 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 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, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a 4-stroke cycle spark ignition internal combustion engine having a plurality of cylinders 300. In FIG. 1, only one of the plurality of cylinders 300 is shown.

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 cylinder head 4 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. 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 an ignition plug 8 for igniting the air-fuel mixture in the combustion chamber 7 and a fuel injection valve 103 for injecting fuel toward the intake port 11.

  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 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. The volume of the combustion chamber 7 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 is at the top dead center as shown by the broken line in FIG. The volume of the combustion chamber 7 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 mechanical compression ratio (hereinafter simply referred to as “compression ratio”), which is the ratio to the in-cylinder volume when is positioned 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. 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 crank pin 22 of the crankshaft 200 at one end thereof, and a sleeve receiving opening 42 for receiving a sleeve 32a of an eccentric member 32 described later at the other end. Have. 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 axial center of the sleeve 32a 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 cylindrical piston pin receiving opening 32d is formed such that its axis is eccentric with respect to 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, when the eccentric member 32 rotates, the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 is positioned. Change. 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 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 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 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. Note that the second compression ratio is a 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 that pushes the second piston 34b works. 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 of the first state and the second 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. 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 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. 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 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 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, the combination of the variable length connecting rod 6 and the OSV 75 of each cylinder 300 corresponds to the “variable compression ratio mechanism” according to the present invention.

  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, a knock sensor 102, and a crank position sensor 201, and can input output signals from 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 amount of intake air. The knock sensor 102 is a sensor that is attached to the cylinder block 3 of the internal combustion engine 1 and outputs a detection signal (for example, voltage) that changes according to the magnitude of vibration generated by the internal combustion engine 1. The crank position sensor 201 is a sensor that outputs an electrical signal correlated with the rotational position of the crankshaft 200.

  The ECU 100 is electrically connected to various devices such as the spark plug 8, the fuel injection valve 103, and the OSV 75 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). The target air-fuel ratio of the air-fuel mixture is determined based on the actual intake air amount ratio). The ECU 100 calculates the target fuel injection amount of the fuel injection valve 103 based on the target air-fuel ratio and the output signal (intake air amount) of the air flow meter 101, and controls the fuel injection valve 103 according to the target fuel injection amount. Control.

  Further, the ECU 100 controls the OSV 75 according to the engine load factor. Specifically, the ECU 100 sets the 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 switching determination value. , OSV75 is controlled. On the other hand, when the engine load factor is equal to or greater than the predetermined switching determination value, the ECU 100 sets the compression ratio of the internal combustion engine 1 to a second compression ratio that is lower than the first compression ratio (the switching mechanism 35 enters the second state). As described above, the OSV 75 is controlled. As described above, the ECU 100 controls the OSV 75 to realize the “compression ratio control means” according to the present invention.

  By the way, if an abnormality occurs in the hydraulic path of the variable compression ratio mechanism, the 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 switching determination value. When this happens, the compression ratio cannot be switched from the first compression ratio to the second compression ratio, which may lead to abnormal combustion of the air-fuel mixture.

  As a method of diagnosing abnormality of the variable compression ratio mechanism, a method of diagnosing abnormality of the variable compression ratio mechanism by attaching a compression ratio sensor for detecting the actual compression ratio to the internal combustion engine 1 can be considered. However, there is a problem in that the number of parts increases and the manufacturing cost increases. Furthermore, there is a problem that it is impossible to distinguish between an abnormality in the compression ratio sensor and an abnormality in the variable compression ratio mechanism.

(Abnormal diagnosis of variable compression ratio mechanism)
Therefore, in this embodiment, an abnormality of the compression ratio changing mechanism of each cylinder 300 is diagnosed using the existing knock sensor 102. That is, when the variable compression ratio mechanism is controlled to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio, an abnormality of the variable compression ratio mechanism is diagnosed based on the measured value of the knock sensor 102. I tried to do it.

Here, the abnormality diagnosis method of the variable compression ratio mechanism will be described with reference to FIG. FIG. 5 shows an engine load factor and a compression ratio when an abnormality that cannot switch the compression ratio from the first compression ratio to the second compression ratio (an abnormality in which the compression ratio is fixed to the first compression ratio) occurs. 6 is a timing chart showing changes over time in ignition timing and knock intensity.

  In FIG. 5, when the engine load factor shifts from a state below a predetermined switching determination value to a state above a predetermined switching determination value, the ECU 100 switches the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio. The OSV 75 is controlled so as to change (t1 in FIG. 5). At this time, if the variable compression ratio mechanism is normal, as described above, when a downward inertia force acts on the piston 5 of the internal combustion engine 1 and combustion of the air-fuel mixture occurs in the combustion chamber 7, When a downward force is applied, the effective length of the variable length connecting rod 6 gradually decreases, so that the compression ratio of the internal combustion engine 1 gradually decreases from the first compression ratio toward the second compression ratio ( (Refer to the one-dot chain line in the second stage timing chart in FIG. 5). That is, after the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio, the variable compression ratio is increased from the time when the compression ratio of the internal combustion engine 1 becomes the second compression ratio. A mechanism response delay (period t1 to t2 in FIG. 5) occurs. In such a response delay period, since the compression ratio of the internal combustion engine 1 is higher than the second compression ratio, the ignition timing of the spark plug 8 is an ignition timing (second compression ratio ignition timing) suitable for the second compression ratio. ), The compression end temperature becomes excessively high and knocking may occur. Therefore, in this embodiment, when the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio, the ignition timing of the spark plug 8 is suitable for the first compression ratio. The ignition timing (first compression ratio ignition timing) is switched to the switching ignition timing. The ignition timing for switching is an ignition timing that is retarded from the ignition timing for the second compression ratio, and when there is an abnormality in which the compression ratio is fixed to the first compression ratio in the variable compression ratio mechanism. Even if there is, it is an ignition timing at which knock does not occur. Such switching ignition timing is determined in advance based on the results of experiments and simulations.

  Next, the ECU 100 switches the ignition timing of the spark plug 8 to the ignition timing for switching when a predetermined period elapses after the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio. To the second compression ratio ignition timing (t2 in FIG. 5). The predetermined period here is an estimated value of the response delay period when the variable compression ratio mechanism is normal, and is determined in advance based on results of experiments and simulations. The response delay period tends to become shorter as the engine load factor becomes higher, and becomes shorter as the engine speed increases. Therefore, the predetermined period may be calculated using the engine load factor and the engine speed as parameters.

  As described above, when the ignition timing of the spark plug 8 is switched from the switching ignition timing to the second compression ratio ignition timing, the compression ratio is fixed to the first compression ratio due to the abnormality of the variable compression ratio mechanism. Then, the compression end temperature becomes excessively high and knocking occurs. By the way, the knock of the internal combustion engine 1 may occur due to deposit accumulation in the combustion chamber 7 or a change over time in the injection characteristics of the fuel injection valve 103. However, when knocking due to an abnormality in the variable compression ratio mechanism occurs, the knock strength is greater than when knocking occurs due to deposit accumulation in the combustion chamber 7 or changes in the injection characteristics of the fuel injection valve 103 over time. Becomes larger. Therefore, if the knock magnitude when the ignition timing of the spark plug 8 is changed from the switching ignition timing to the second compression ratio ignition timing is greater than a predetermined threshold, the variable compression ratio mechanism is abnormal (the compression ratio is It can be diagnosed that a state in which the first compression ratio does not switch to the second compression ratio) has occurred.

As the “knock strength” here, an integrated value of the vibration strength detected by the knock sensor 102 in a predetermined knock determination period (for example, a period from ATDC 0 ° CA to ATDC 90 ° CA) is used. As the knock strength, the maximum vibration strength among the vibration strengths detected by the knock sensor 102 during the knock determination period may be used. Also,
The “predetermined threshold value” here is a value that can be determined that the cause of knocking is an abnormality of the variable compression ratio mechanism if the knock intensity is greater than the predetermined threshold value, and in the combustion chamber 7. This is a value larger than the knock intensity in the case where a knock due to deposit accumulation or a change with time in the injection characteristic of the fuel injection valve 103 occurs.

  In the example shown in FIG. 5, the ignition timing of the spark plug 8 is retarded from the second compression ratio ignition timing after the occurrence of knocking due to the abnormality of the variable compression ratio mechanism. This is because the ignition timing is retarded to a timing at which knock does not occur by the action of a KCS (Knock Control System) mounted on the ECU 100.

  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. In this processing routine, the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio, in other words, from the state where the engine load factor is less than the predetermined load factor. This is a processing routine that is executed with a transition to a state equal to or higher than the load factor as a trigger.

  In the processing routine of FIG. 6, the ECU 100 first activates a counter in the processing of S101. The counter here is a counter that measures an elapsed time from the time when the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio.

  In the process of S102, the ECU 100 sets the ignition timing of the spark plug 8 to the switching ignition timing. As described above, the switching ignition timing is an ignition timing that is retarded from the second compression ratio ignition timing, and an abnormality occurs in which the compression ratio is fixed to the first compression ratio in the variable compression ratio mechanism. Even in the case of ignition, the ignition timing does not cause knock.

  In the process of S103, it is determined whether or not the measurement time C of the counter is equal to or longer than a predetermined period C0. During the predetermined period C0, as described above, when the variable compression ratio mechanism is normal, the control of the OSV 75 is started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio. This is an estimated value of the response delay period required until the compression ratio of the engine 1 becomes the second compression ratio, and is calculated based on the engine load factor and the engine speed. When a negative determination is made in the process of S103, the ECU 100 repeatedly executes the process of S103. On the other hand, if an affirmative determination is made in the process of S103, the ECU 100 proceeds to the process of S104, and changes the ignition timing of the spark plug 8 from the switching ignition timing to the second compression ratio ignition timing. Here, when the ECU 100 executes the processing of S102 to S104, the “ignition timing control means” according to the present invention is realized.

  In the process of S105, the ECU 100 calculates the knock intensity based on the measured value of the knock sensor 102. Subsequently, the ECU 100 proceeds to the process of S106, and determines whether or not the knock intensity calculated in the process of S105 is equal to or greater than a predetermined threshold value. As described above, the predetermined threshold here is a value that can be determined that the cause of knocking is an abnormality of the variable compression ratio mechanism if the knock intensity is larger than the predetermined threshold, and combustion. This is a value larger than the knock strength when knocking occurs due to deposit accumulation in the chamber 7 or change over time in the injection characteristics of the fuel injection valve 103.

If a negative determination is made in the process of S106, the ECU 100 proceeds to the process of S107, and determines that the variable compression ratio mechanism is normal. On the other hand, if an affirmative determination is made in the process of S106, the ECU 100 proceeds to the process of S108 and determines that the variable compression ratio mechanism is abnormal. Here, when the ECU 100 executes the processes of S105 to S108, the “diagnostic means” according to the present invention is realized.

  When the ECU 100 finishes executing the process of S107 or the process of S108, the ECU 100 resets the measurement time C of the counter to 0 in the process of S109, and ends the execution of this process routine.

  According to the embodiment described above, it is possible to diagnose abnormality of the variable compression ratio mechanism using the existing knock sensor 102.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIG. 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 and the present embodiment described above is that when a predetermined period has elapsed since the control of the OSV 75 was started to switch the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio. If the engine load factor is equal to or greater than the predetermined load factor, the ignition timing of the spark plug 8 is changed from the switching ignition timing to the second compression ratio ignition timing, and if the engine load factor is less than the predetermined load factor, The ignition timing of the spark plug 8 is changed from the switching ignition timing to the knock induced ignition timing. The “predetermined load factor” here means that if the engine load factor is less than the predetermined load factor, even if the variable compression ratio mechanism is abnormal (the abnormality in which the compression ratio is fixed to the first compression ratio), The intensity is expected to be less than the predetermined threshold value, and is determined in advance based on the results of experiments and simulations. Further, the “knock-induced ignition timing” is an ignition timing at which the knock intensity is equal to or higher than the predetermined threshold even if the engine load factor is less than the predetermined load factor if the variable compression ratio mechanism is abnormal. Further, the ignition timing is on the advance side of the second compression ratio ignition timing.

  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. 7 is a flowchart showing a processing routine executed by the ECU 100 when performing abnormality diagnosis of the variable compression ratio mechanism. In the processing routine of FIG. 7, the same reference numerals are given to the same processing as the processing routine of FIG. 6 described above.

  The difference between the processing routine of FIG. 6 and the processing routine of FIG. 7 described above is that, when an affirmative determination is made in the process of S103, the determination process of S201 is executed, and a negative determination is made in the determination process of S201. The point is that the process of S202 is executed.

  In the process of S201, the ECU 100 determines whether or not the engine load factor is equal to or greater than a predetermined load factor. As described above, when the engine load factor is less than the predetermined load factor, the predetermined load factor may cause the knock strength to be less than the predetermined threshold even if the variable compression ratio mechanism is abnormal. Expected value. When an affirmative determination is made in the process of S201, the ECU 100 executes the processes after S104, as in the first embodiment described above. On the other hand, if a negative determination is made in the process of S201, the ECU 100 proceeds to the process of S202, and changes the ignition timing of the spark plug 8 from the switching ignition timing to the knock-induced ignition timing. As described above, the knock-induced ignition timing here is an ignition in which the knock intensity is equal to or greater than the predetermined threshold even if the engine load factor is less than the predetermined load factor if the variable compression ratio mechanism is abnormal. It's time. The period for setting the ignition timing of the spark plug 8 to the knock induced ignition timing is, for example, a period in which a margin is added to the period required for calculating the knock intensity.

  According to the above-described embodiment, even when the engine load factor when the predetermined period has elapsed is less than the predetermined load factor, the knock sensor 102 is used to perform abnormality diagnosis of the variable compression ratio mechanism. It becomes possible.

  In the case where the internal combustion engine 1 includes a variable valve mechanism that can change the opening / closing timing of the intake valve 9, the ignition is performed when the engine load factor is less than the predetermined load factor when the predetermined period has elapsed. Instead of setting the ignition timing of the plug 8 to the knock-induced ignition timing, a state in which knocking is likely to occur may be formed using a variable valve mechanism. For example, the compression end temperature may be increased by changing the opening / closing timing of the intake valve 9 to an opening / closing timing that increases the charging efficiency of the intake air.

<Other embodiments>
In the first and second embodiments described above, an example in which the abnormality diagnosis of the variable compression ratio mechanism is performed based on the knock strength has been described. However, based on the amount of change per unit time of the KCS learning value used for KCS. Thus, abnormality diagnosis of the variable compression ratio mechanism may be performed. The amount of change per unit time of the KCS learning value tends to increase as the knock intensity at the time of knock occurrence increases. That is, the KCS learning value can be used as a value that correlates with the knock intensity at the time of knock occurrence.

  In the first and second embodiments described above, the example in which the ignition timing of the spark plug 8 in the predetermined period is fixed to the switching ignition timing has been described. However, from the switching ignition timing to the second compression ratio ignition. You may change gradually toward the time. In that case, if the variable compression ratio mechanism is abnormal, knocking may occur during a predetermined period. Therefore, when the ignition timing of the spark plug 8 during the predetermined period is gradually changed, the knock strength of the knock generated during the predetermined period is integrated, and if the integrated value is equal to or greater than a predetermined threshold, the variable compression ratio mechanism May be diagnosed as abnormal.

  In the first and second embodiments described above, the response delay time required for switching the compression ratio of the internal combustion engine 1 from the first compression ratio to the second compression ratio when the variable compression ratio mechanism is normal is estimated. Although an example in which the value is set to a predetermined period has been described, when a device that affects the combustion state of the internal combustion engine, such as an EGR device or a variable valve mechanism, is provided, the response delay period of the variable compression ratio mechanism It is desirable to set the estimated value of the longest period among the period required for the above-described device to switch from the state suitable for the first compression ratio to the state suitable for the second compression ratio as the predetermined period.

1 Internal combustion engine 6 Variable length connecting rod 8 Spark plug 32 Eccentric member 35 Switching mechanism 75 OSV
100 ECU
102 Knock sensor

Claims (2)

A variable compression ratio mechanism capable of switching the compression ratio of the internal combustion engine to at least a first compression ratio and a second compression ratio lower than the first compression ratio;
A knock sensor attached to the internal combustion engine;
A spark plug attached to each cylinder of the internal combustion engine;
Compression ratio control means for controlling the variable compression ratio mechanism so that the compression ratio of the internal combustion engine becomes a compression ratio according to the operating state of the internal combustion engine;
An abnormality diagnosis device for a variable compression ratio mechanism applied to an internal combustion engine comprising:
The abnormality diagnosis device includes:
When the compression ratio control means controls the variable compression ratio mechanism to switch the compression ratio of the internal combustion engine from the first compression ratio to the second compression ratio, the compression ratio control means uses the variable compression ratio mechanism. The ignition timing of the spark plug is set to an ignition timing retarded from the ignition timing for the second compression ratio, which is an ignition timing suitable for the second compression ratio, until a predetermined period elapses after the control is started. Ignition timing control means for setting the ignition timing of the ignition plug to the ignition timing for the second compression ratio from the ignition timing for switching when the predetermined period has elapsed and the ignition timing of the ignition plug is changed from the ignition timing for switching
When the ignition timing of the ignition plug is changed from the ignition timing for switching to the ignition timing for the second compression ratio by the ignition timing control means, the knock intensity is calculated based on the measured value of the knock sensor, A diagnostic means for diagnosing that the variable compression ratio mechanism is abnormal if the knock intensity is greater than a predetermined threshold;
An abnormality diagnosis device for a variable compression ratio mechanism, comprising: The ignition timing control means, when the engine load factor of the internal combustion engine when the predetermined period has elapsed after the control of the variable compression ratio mechanism by the compression ratio control means is less than a predetermined load factor, Instead of changing the ignition timing of the spark plug from the switching ignition timing to the second compression ratio ignition timing, the ignition timing is advanced from the switching ignition timing to the second compression ratio ignition timing. Change to the knock-induced ignition timing
The diagnostic means calculates a knock intensity based on a measured value of the knock sensor when the ignition timing of the ignition plug is changed from the switching ignition timing to the knock induction ignition timing by the ignition timing control means. 2. The variable compression ratio mechanism abnormality diagnosis apparatus according to claim 1, wherein if the knock intensity is greater than the predetermined threshold value, the variable compression ratio mechanism is diagnosed as abnormal.

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