JP4136202B2 - Abnormality detection device for variable valve gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detecting device for a variable valve operating device that detects the presence or absence of an abnormality in a variable valve operating device that varies at least one valve characteristic of an intake / exhaust system in accordance with an operating state of an internal combustion engine.
[0002]
[Prior art]
In order to maintain the engine characteristics to the maximum even under different operating conditions of the internal combustion engine, variable operation that makes the valve characteristics variable such as the valve timing and valve lift amount of the engine valve according to the operating state of the engine Valve devices are conventionally known.
[0003]
For example, in the variable valve operating apparatus described in Japanese Patent Laid-Open No. 8-177434, two types of cams of low speed type and high speed type having different profiles are provided, and these cams are selectively selected according to the operating state of the engine. Thus, the lift amount of the engine valve that is driven to open and close based on these cams is made variable.
[0004]
Further, in the variable valve operating apparatus described in the publication, even if the same cam is used, the relative rotational phase of the camshaft with respect to the engine output shaft (crankshaft) depends on the operating state of the engine. By appropriately changing, the opening / closing timing of the engine valve is also variable at the same time.
[0005]
On the other hand, the device described in the above publication is a variable valve operating device, particularly a device that makes the lift amount of the engine valve variable. For example, the cam switching mechanism is fixed as a high-speed cam. In this case, a means for detecting this as a failure (failure detection means) is also described. Incidentally, in the variable valve system provided on the intake valve side, when the cam switching mechanism is fixed in this manner as a high speed cam, the valve overlap of the engine, particularly in the low load operation region, is abnormally large. It becomes difficult to maintain the engine performance, for example, the intake air blows back.
[0006]
Therefore, in the apparatus described in the publication, paying attention to the fact that the switching mechanism is hydraulically controlled, a hydraulic sensor for detecting the hydraulic pressure supplied to the switching mechanism is provided, or the lift amount of the engine valve is set. The occurrence of such an abnormality (failure) is detected by providing a sensor (lift sensor) for direct detection.
[0007]
[Problems to be solved by the invention]
As described above, even if the cam switching mechanism is in an abnormal state where the cam for the high speed is stuck, the fact can be surely detected by using the hydraulic pressure sensor or the lift sensor.
[0008]
However, it is not desirable for an internal combustion engine such as an in-vehicle engine that is required to be separately mounted or to reduce its size, although it is necessary to separately provide the hydraulic pressure sensor and the lift sensor for the purpose of detecting the abnormality. Not only is it economically disadvantageous.
[0009]
Further, as described in the above publication, when these sensors are separately required, it is also necessary to execute a new diagnosis process for diagnosing the presence or absence of failure of the sensors themselves.
[0010]
The publication also states that the abnormality of the variable valve operating device may be detected based on the intake air flow rate. For example, the abnormality of the device in a certain cylinder may cause such intake air flow rate. Alternatively, the influence on the intake negative pressure is generally small, and the problem in terms of detection accuracy cannot be ignored.
[0011]
The present invention has been made in view of such circumstances, and its object is to detect an abnormality of the variable valve operating device described above in a simpler and more accurate manner. Is to provide.
[0012]
[Means for Solving the Problems]
  In the following, means for achieving the above object and its effects are described.
  First, in the first aspect of the invention, the suction of the internal combustion engine according to the operating state of the internal combustion engine.Air system andexhaustSystematicValve characteristicsRespectivelyVariableIntake systemVariable valve gearAnd exhaust system variable valve gearaboutThemIn the abnormality detection device for a variable valve device that detects the presence or absence of an abnormality in the engine, misfire detection means for detecting the occurrence of misfire in the engine, and the occurrence frequency of misfire detected by the misfire detection meansIs monitored separately for each operation region of the engine, and the misfire occurrence frequency for each operation region to be monitoredAbnormality detecting means for detecting the presence or absence of abnormality of the variable valve operating apparatus based onAndPreparationEach of the variable valve gears switches between a valve characteristic corresponding to the high speed operation of the engine and a valve characteristic corresponding to the low speed operation according to the operating state of the engine, and the abnormality detection means is the monitoring unit. Based on the misfire occurrence frequency for each operating region to be operated, on the condition that the misfire occurrence frequency is high only in the low speed and low load operation region, the variable valve device of the exhaust system has the low speed from the valve characteristics corresponding to the high speed operation. A variable valve operating device for the intake system is detected on the condition that the occurrence of switching abnormality to the valve characteristic corresponding to the operation is detected and the misfire occurrence frequency is high in the low speed low load operation region and the medium speed medium load operation region. In this case, it is detected that there is an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation.This is the gist.
[0013]
  MachineWhen the cam switching mechanism is stuck in the high-speed cam in a variable valve system that makes the lift amount of the Seki valve variable, that is, the valve corresponding to the low-speed operation from the valve characteristic corresponding to the high-speed operation. If the engine is operated at a low load when there is an abnormality in switching to the characteristic, the valve overlap becomes abnormally large as described above, and the intake air blows back. Further, when the valve overlap becomes large in this way, the amount of EGR (exhaust gas recirculation) in the engine combustion chamber increases, and the probability of occurrence of misfire increases. Such a phenomenon occurs substantially in the same manner even in a variable valve system that makes the opening / closing timing of the engine valve variable and this is fixed at the opening / closing timing corresponding to, for example, high-speed operation.
[0014]
Therefore, as in the first aspect of the present invention, if the occurrence of misfire in the engine is detected and the occurrence frequency of the detected misfire is monitored, it may be related to only one cylinder. Thus, it is possible to detect the presence or absence of abnormality of such a variable valve operating apparatus with high accuracy. In an internal combustion engine such as an in-vehicle engine, such misfire detection is often performed as a normal process. Therefore, according to the configuration, abnormality detection of the variable valve operating apparatus can be performed without providing any special sensor. Will be able to do. Further, in the first aspect of the present invention, the misfire detection means may be configured arbitrarily, and even if this requires a separate sensor or the like, the occurrence frequency of the detected misfire is monitored. According to this configuration, it is possible to detect with high accuracy whether there is an abnormality in the variable valve apparatus.
[0016]
  Also,As described above, the occurrence frequency of misfire caused by the abnormality of the variable valve operating device is usually different for each operation region of the engine. In other words, if the occurrence frequency of misfire is monitored separately for each operation region of the engine, an abnormality to be detected in the variable valve operating device, that is, a valve corresponding to the low speed operation from the valve characteristic corresponding to the high speed operation described above. Presence or absence of abnormal switching to characteristics can be detected more accurately..
[0018]
  here,If there is an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation, and this abnormality occurs in the variable valve gear of the intake system, Therefore, the frequency of misfires increases in a relatively wide operating range from the low load operating range to the medium load operating range of the engine. On the other hand, when the abnormality occurs in the variable valve system of the exhaust system, the amount of EGR in the engine combustion chamber is relatively small, and the frequency of misfires is increased only in the low load operation region of the engine. become.
[0020]
  Therefore, according to the invention of claim 1,For variable valve gears that switch between the valve characteristics corresponding to high-speed operation of the engine and the valve characteristics corresponding to low-speed operation according to the operating state of the engine, one of the same devices of the intake system or the exhaust system is compatible with high-speed operation. Even if there is an abnormality in switching from valve characteristics to valve characteristics corresponding to low speed operationThisThis can be accurately identified and detected.
[0021]
  ContractClaim2In the described invention,Variable operation for detecting the presence or absence of abnormality in an intake system variable valve device and an exhaust system variable valve device that respectively change the valve characteristics of the intake system and the exhaust system of the engine according to the operating state of the internal combustion engine In the abnormality detection device for the valve device, misfire detection means for detecting the occurrence of misfire in the engine, and the occurrence frequency of misfire detected by the misfire detection means are monitored separately for each operation region of the engine, and the operation to be monitored An abnormality detecting means for detecting the presence or absence of abnormality of the variable valve operating device based on the misfire occurrence frequency for each region,Each of the variable valve gears switches a valve characteristic corresponding to the high speed operation of the engine and a valve characteristic corresponding to the low speed operation according to the operating state of the engine, and the abnormality detection means monitors the Based on the misfire occurrence frequency for each operation region, the misfire occurrence frequency only in the low speed and low load operation region is higher than a predetermined first value and lower than a second value larger than the first value. In the variable valve operating apparatus for one cylinder of the exhaust system, it is detected that an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation occurs, and the low speed and low load Compatible with the low speed operation from the valve characteristics corresponding to the high speed operation in the variable valve operating system of the plurality of cylinders of the exhaust system on condition that the misfire occurrence frequency only in the operation region is higher than the second value To the valve characteristics It is detected that a changeover abnormality has occurred, and the misfire occurrence frequency in the low speed low load operation region and the medium speed medium load operation region is higher than the first value and lower than the second value. In the variable valve operating device for one cylinder of the intake system, it is detected that a switching abnormality from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation has occurred, and the low speed and low load operation region On the condition that the misfire occurrence frequency is higher than the second value and the misfire occurrence frequency in the medium-speed medium load operation region is higher than the first value and lower than the second value. In a variable valve operating device for each cylinder of an intake system and an exhaust system, it is detected that a switching abnormality from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation has occurred, and the low speed low The misfire occurrence frequency in the load operation region is the first And a valve corresponding to the high-speed operation in the variable valve device for a plurality of cylinders of the intake system on the condition that the misfire occurrence frequency in the medium-speed and medium-load operation region is higher than the second value. The gist of the present invention is to detect that a switching abnormality from the characteristic to the valve characteristic corresponding to the low speed operation has occurred.
[0022]
  Also,When the occurrence frequency of the misfire increases more than a predetermined value, there is a possibility that misfire has occurred in a plurality of cylinders such as two cylinders due to an abnormality of the variable valve operating apparatus. That is, when the misfire occurrence frequency becomes a threshold value for determining the misfire occurrence due to the abnormality of the variable valve operating device in one cylinder having the first value as to the misfire occurrence frequency, The second value larger than the first value by a predetermined value can be determined as a threshold value for determining the occurrence of misfire due to an abnormality of the variable valve device in a plurality of cylinders. And in this case, FurtherThe following can be said.
[0023]
(A) When the misfire occurrence frequency only in the low speed and low load operation region is higher than the first value and lower than the second value, the variable valve device of one cylinder of the exhaust system operates at high speed. There is a possibility that an abnormality has occurred in switching from the valve characteristic corresponding to the valve characteristic to the valve characteristic corresponding to the low speed operation.
[0024]
(B) When the misfire occurrence frequency only in the low-speed and low-load operation region is higher than the second value, the variable valve device for a plurality of cylinders in the exhaust system switches to low-speed operation from the valve characteristics corresponding to high-speed operation. An abnormal switching to the corresponding valve characteristic may have occurred.
[0025]
(C) When the misfire occurrence frequency in the low-speed low-load operation region and the medium-speed medium-load operation region is higher than the first value and lower than the second value, the variable valve of one cylinder of the intake system There is a possibility that an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation has occurred in the apparatus.
[0026]
(D) Misfire occurrence frequency in the low speed and low load operation region is higher than the second value, and misfire occurrence frequency in the medium and medium load operation region is higher than the first value and the second value. Lower than that, there is a possibility that there is a switching abnormality from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation in the variable valve operating device of each cylinder of the intake system and the exhaust system. .
[0027]
(E) When the misfire occurrence frequency in the low speed and low load operation region is higher than the first value and the misfire occurrence frequency in the medium speed medium load operation region is higher than the second value, a plurality of intake systems There is a possibility that an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation occurs in the variable valve operating device of the cylinder.
[0028]
  Therefore, the claim which performs detection about these (a)-(b) together2According to the above-described configuration of the described invention, it is possible to more accurately identify and detect the presence / absence of the switching abnormality and the content of the abnormality in the variable valve gear disposed in both the intake system and the exhaust system of the internal combustion engine. become able to.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment that embodies an abnormality detection device for a variable valve device according to the present invention will be described below. The variable valve operating apparatus according to the present embodiment has a cam switching type variable valve operating mechanism, and is configured as an apparatus that mainly changes the lift amount of the engine valve in accordance with the cam switching by the mechanism. .
[0032]
First, a schematic configuration of an internal combustion engine provided with a variable valve gear according to the present embodiment will be described with reference to FIG. The internal combustion engine 1 is a DOHC internal combustion engine in which gasoline is used as fuel and the cylinder head 3 is provided with two camshafts. The internal combustion engine 1 is an in-line four-cylinder type in which four cylinders are arranged in series, and each cylinder has a four-valve type in which two intake valves and two exhaust valves are provided. In FIG. 1, for convenience, members that are provided symmetrically in the intake system and the exhaust system of the internal combustion engine 1 and have basically the same functions are denoted by the same reference numerals. Is distinguished by attaching “i” at the end and “e” at the end of exhaust system members. Further, in the following description, when the identifiers i and e at the end of the reference numerals of these members are omitted, both the intake system and exhaust system members are indicated unless otherwise specified.
[0033]
The internal combustion engine 1 includes a cylinder block 2, a cylinder head 3 provided on the cylinder block 2, and a piston 5 that reciprocates in a cylinder bore 4 formed in the cylinder block 2. The piston 5 is connected to the crankshaft 7 via a connecting rod 6. The crankshaft 7 is rotated as the piston 5 reciprocates.
[0034]
A crank pulley 23 is connected to the crankshaft 7 so as to be integrally rotatable. Further, a rotor 8 having a disk shape is attached to the shaft 7 so as to be integrally rotatable. A predetermined number of convex portions are formed on the outer peripheral portion of the rotor 8. A crank angle sensor 9 is provided in the vicinity of the rotor 8. The crank angle sensor 9 detects the convex portion of the rotor 8 by an electromagnetic pickup and outputs a pulse signal. Based on a signal output from the crank angle sensor 9, an electronic control unit (hereinafter referred to as “ECU”) 10, which will be described later, determines the rotational speed of the crankshaft 7, that is, the engine rotational speed NE and the rotational phase of the shaft 7, The misfire detection rate is calculated.
[0035]
A combustion chamber 11 for combusting the air-fuel mixture is defined by the inner walls of the cylinder head 3 and the cylinder bore 4 and the upper end surface of the piston 5. An ignition plug 35 for igniting the air-fuel mixture in the chamber 11 is provided at the upper center of the combustion chamber 11. Further, an intake port 12 i for supplying an air-fuel mixture to the chamber 11 and an exhaust port 12 e for discharging combustion gas from the chamber 11 are connected to the combustion chamber 11. An intake valve 13i and an exhaust valve 13e are arranged in the combustion chamber 11 and connected to the intake / exhaust ports 12i and 12e, respectively. The intake valve 13i and the exhaust valve 13e are slidably supported by the cylinder head 3. Further, as the valves 13i and 13e slide, the ports 12i and 12e and the combustion chamber 11 are communicated or blocked.
[0036]
On the other hand, an intake pipe 14i and an exhaust pipe 14e are connected to the intake port 12i and the exhaust port 12e, respectively. The intake pipe 14 i is provided with an injector 15 for injecting and supplying fuel to the combustion chamber 11 in the vicinity of the connection portion between the intake port 12 i and the combustion chamber 11. A throttle valve 16 for adjusting the amount of intake air introduced into the combustion chamber 11 is provided on the upstream side of the injector 15 in the intake pipe 14i. The throttle valve 16 is driven to open and close based on depression of the accelerator pedal 17.
[0037]
Further, the tip of the intake pipe 14i is connected to an air cleaner 18 that cleans the air introduced into the pipe 14i. An air flow meter 19 for detecting the amount of air flowing through the intake pipe 14i, that is, the intake air amount, is provided downstream of the air cleaner 18. Note that it is possible to grasp the load state of the internal combustion engine 1 based on the intake air amount. In the present embodiment, this intake air amount is detected as an amount GN (g / rev) per engine revolution.
[0038]
Next, in the internal combustion engine 1, the configuration of the valve operating system that opens and closes the intake valve 13i and the exhaust valve 13e will be described with reference to FIG.
An intake camshaft 20i and an exhaust camshaft 20e are rotatably supported above the intake / exhaust valves 13i and 13e above the cylinder head 3, respectively. These camshafts 20i and 20e are connected to an intake side cam pulley 21i and an exhaust side cam pulley 21e, respectively, so as to be integrally rotatable. These cam pulleys 21 are drivingly connected to the crank pulley 23 through a timing belt 22 at a reduction ratio of 1/2. As a result, each camshaft 20 is rotated once every time the crankshaft 7 rotates twice.
[0039]
Two cams for each cylinder, that is, a low speed cam 29 and a high speed cam 31 are mounted on the camshaft 20 so as to be integrally rotatable. The cam profile of the high-speed cam 31 is set so that at least one of the lift amount and the valve-opening period of the engine valve 13 that is driven to open and close thereby increases. In the present embodiment, the cam profile of the high-speed cam 31 is set so that both the lift amount and the valve opening timing are increased.
[0040]
An intake side rocker shaft 24i and an exhaust side rocker shaft 24e are provided below the camshafts 20i and 20e, respectively. Each of these rocker shafts 24i, 24e is rotatably mounted with a cam switching type variable valve mechanism 50 that is configured around the rocker arm 25 for each cylinder. The rocker arm 25 is in contact with the heads of the pair of engine valves 13. The rocker arms 25 are urged toward the cams 29 and 31 provided on the camshaft 20 by the urging force of the valve springs 28 provided on the engine valves 13. As the camshaft 20 rotates, the rocker arm 25 is pressed by the cam lift and swings about the rocker shaft 24. As the rocker arm 25 swings, each valve 13 is driven to open and close. In the following description, the side of the rocker arm 25 that is supported by the rocker shaft 24 is referred to as the proximal end side, and the side that contacts the head of the valve 13 is referred to as the distal end side.
[0041]
Next, the structure of the cam-switching variable valve mechanism 50 configured around the rocker arm 25 will be described in detail with reference to FIGS.
2 shows a planar structure of the cam switching type variable valve mechanism 50, and FIGS. 3 and 4 show a cross-sectional structure of a hydraulic lock mechanism provided in the mechanism 50. FIG.
[0042]
As shown in FIG. 2, the rocker arm 25 is formed in a substantially planar rectangular shape, and the base end side thereof is supported by the rocker shaft 24 as described above. From the distal end side of the rocker arm 25, two arms 51 are formed to extend obliquely forward, and the distal ends thereof can come into contact with the head of the valve 13 (FIG. 1).
[0043]
A roller follower 52 is rotatably supported on the upper surface of the rocker arm 25. The roller follower 52 is capable of rolling contact with the low speed cam 29. Further, a guide hole 53 having a circular cross section is formed vertically downward on the upper surface of the rocker arm 25 and on the side of the roller follower 52 (right side in FIG. 2). As shown in FIGS. 3 and 4, a movable cam follower 54 having a substantially cylindrical shape is slidably inserted into the guide hole 53. The movable cam follower 54 includes a slipper 55 having a rectangular cross section provided at the head and a leg portion 56 having a cylindrical shape so as to be inserted into the guide hole 53. The upper end surface of the slipper 55 is an arc surface in the manner shown in FIGS. 3 and 4, and is capable of sliding contact with the high-speed cam 31. A lost motion spring 57 is disposed between the lower end surface of the slipper 55 and the upper surface of the rocker arm 25. The movable cam follower 54 is biased toward the high speed cam 31 (FIGS. 1 and 2) by the lost motion spring 57. The spring force of the lost motion spring 57 is set to be sufficiently smaller than the spring force of the valve spring 28 (FIG. 1).
[0044]
On the other hand, as shown in FIGS. 3 and 4, a cylinder hole 58 having a circular cross section perpendicular to the guide hole 53 is formed below the rocker arm 25 from the distal end side of the rocker arm 25. A hydraulic piston 59 having a substantially cylindrical shape is inserted into the cylinder hole 58, and can slide between the position shown in FIG. 3 and the position shown in FIG.
[0045]
A perspective structure of the hydraulic piston 59 is shown in FIG. An engagement groove 60 having a rectangular cross section is formed from the tip of the hydraulic piston 59 to the center, and a pair of side edges 61 are provided with the groove 60 interposed therebetween. The inner bottom portion of the engagement groove 60 is a flat surface, and serves as a support portion 62 capable of abutting and supporting the bottom surface of the leg portion 56 (FIGS. 3 and 4) of the movable cam follower 54. On the other hand, the inner bottom portion of the front end side 63 of the groove 60 is cut out, and only the side 61 is projected. 3B and 4B, the leg portion 56 of the movable cam follower 54 is shown in plan view on the surface facing the side wall of the engagement groove 60. The leg portion 56 can be inserted into the groove 60 through the flat surface portion.
[0046]
That is, when the hydraulic piston 59 is positioned at the position shown in FIGS. 3A and 3B, the leg portion 56 of the movable cam follower 54 is positioned at the notch portion of the engagement groove 60, and the cam follower 54 is guided by the guide. The inside of the hole 53 can be freely slid. On the other hand, when the hydraulic piston 59 is positioned at the position shown in FIGS. 4A and 4B, the bottom surface of the leg portion 56 of the movable cam follower 54 is abutted and supported by the support portion 62 of the engagement groove 60. The sliding of the movable cam follower 54 is limited.
[0047]
Further, a spring receiving member 64 is disposed in the engagement groove 60, and a coil spring 65 is provided between the spring receiving member 64 and the hydraulic piston 59 in the manner shown in FIGS. It is arranged. The coil spring 65 urges the spring receiving member 64 toward the movable cam follower 54 and urges the hydraulic piston 59 toward the inner bottom surface of the cylinder hole 58, that is, the base end side of the rocker arm 25.
[0048]
Here, a space formed between the inner bottom surface of the cylinder hole 58 and the base end side end surface of the hydraulic piston 59 is a hydraulic chamber 66. The hydraulic chamber 66 communicates with an oil passage 67 formed in the rocker arm 25. The oil passage 67 communicates with a rocker shaft oil passage 68 (FIG. 2) formed in the rocker shaft 24 along the axis.
[0049]
That is, in the cam switching type variable valve mechanism 50 configured as described above, when the pressure of the lubricating oil supplied into the hydraulic chamber 66 becomes higher than a certain level, the hydraulic piston 59 resists the biasing force of the coil spring 65. 3 is moved from the position shown in FIG. 3 to the position shown in FIG. 4 to limit the sliding of the movable cam follower 54 in the rocker arm 25. The movable cam follower 54 whose sliding is thus restricted swings integrally with the rocker arm 25 based on the rotation and pressing of the high speed cam 31 (FIGS. 1 and 2).
[0050]
On the other hand, when the pressure of the lubricating oil supplied into the hydraulic chamber 66 decreases, the hydraulic piston 59 moves from the position shown in FIG. 4 to the position shown in FIG. 3 by the urging force of the coil spring 65, and the movable cam follower 54 moves to the rocker arm 25. It can slide freely within. At this time, the movable cam follower 54 is separated from the rocker arm 25, so that the movable cam follower 54 is swung freely, and the rocker arm 25 is swung based on the rotation and pressing of the low speed cam 29 (FIGS. 1 and 2).
[0051]
In this embodiment, the hydraulic piston 59, the coil spring 65, and the hydraulic chamber 66 provided in the cylinder hole 58 are used to restrict or release the sliding movement of the movable cam follower 54 in the guide hole 53. A type locking mechanism (hereinafter simply referred to as “locking mechanism”) is configured.
[0052]
Next, the control mode of the variable valve operating apparatus configured as described above will be described.
During low-speed operation, the ECU 10 operates an appropriate hydraulic pressure switching valve (not shown) to remove oil from the hydraulic chamber 66, and lowers the hydraulic pressure in the hydraulic chamber 66.
[0053]
When the hydraulic pressure in the hydraulic chamber 66 decreases in this way, the hydraulic piston 59 is pressed against the base side of the rocker arm 25 by the urging force of the coil spring 65 and is positioned at the position shown in FIG. Since the lower end portion of the movable cam follower 54 at this time is located at a portion where the bottom surface of the engagement groove 60 of the hydraulic piston 59 is cut out, sliding in the vertical direction is allowed.
[0054]
The urging force of the lost motion spring 57 that urges the above-described movable cam follower 54 toward the high-speed cam 31 is set sufficiently smaller than the urging force of the coil spring 65 of the engine valve 13. Therefore, the high-speed cam 31 at this time merely slides the movable cam follower 54, and the pressure is hardly transmitted to the rocker arm 25. Accordingly, the rocker arm 25 at this time is swung based on the pressing of the low speed cam 29 transmitted through the roller follower 52, and the engine valve 13 is also driven to open and close by the low speed cam 29.
[0055]
On the other hand, during high-speed operation, the ECU 10 operates the hydraulic pressure switching valve to supply oil to the hydraulic chamber 66 so as to increase the hydraulic pressure in the hydraulic chamber 66.
When the hydraulic pressure in the hydraulic chamber 66 increases in this way, the hydraulic piston 59 moves to the tip side of the rocker arm 25 against the urging force of the coil spring 65. When the hydraulic piston 59 moves to the position shown in FIG. 4, the lower end portion of the movable cam follower 54 comes to be positioned on the support portion 62 of the engagement groove 60 of the hydraulic piston 59. At this time, when the movable cam follower 54 is pushed down, the lower end surface thereof comes into contact with the support portion 62 of the engagement groove 60.
[0056]
Then, the pressing of the high-speed cam 31 at this time is directly transmitted to the rocker arm 25 through the contact between the movable cam follower 54 and the hydraulic piston 59. That is, the movable cam follower 54 and the rocker arm 25 at this time are in a fastened state and rotate together. In this case, the rocker arm 25 is rotated by the high speed cam 31, and the engine valve 13 is also driven to open and close by the high speed cam 31.
[0057]
FIG. 6 is a graph showing the lift characteristics of the engine valve 13 when the high speed cam 31 and the low speed cam 29 are used. 6A shows the lift characteristics when the low-speed cam 29 is used for both the intake and exhaust systems, and FIG. 6B shows the lift characteristics when the high-speed cam 31 is used for both the intake and exhaust systems. Each is shown. In this graph, the horizontal axis represents the crank angle, and the vertical axis represents the lift amount. Since the lift amount by the high-speed cam 31 is larger than the lift amount by the low-speed cam 29, the intake air amount represented by the area surrounded by the curve and the horizontal axis is also large.
[0058]
By the way, even if a command for switching to the high speed cam 31 or the low speed cam 29 is sent from the ECU 10 for some reason, the hydraulic piston 59 cannot freely move in the cylinder hole 58 and the command is not executed. is there. In particular, as in this embodiment, the engine is provided with a plurality of cam followers that respectively open and close the engine valve 13 by receiving the press of a plurality of cams having different cam characteristics, and by engaging these cam followers together, the engine In a variable valve operating system that switches the valve characteristic of the valve 13 to a valve characteristic corresponding to high-speed operation of the internal combustion engine, and switches to the valve characteristic corresponding to low-speed operation by separating each engaged cam follower, Due to the sticking of the hydraulic piston 59 or the like, there is a possibility that a switching failure from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation may occur.
[0059]
FIG. 7 is a graph showing the lift characteristics of the engine valve 13 when the above-described cam switching failure occurs. FIG. 7 shows the valve lift characteristic when the low-speed cam shown in FIG. 7A is used. In particular, FIG. 7B shows a state where the high-speed cam 31i of the intake system is locked. ) Shows the characteristics when the high speed cam 31e of the exhaust system is locked. As apparent from comparison of these graphs, the intake / exhaust mode in the combustion chamber 11 of the internal combustion engine 1 depends on whether the lock state of the high-speed cam 31 is generated in the intake system or the exhaust system. It will be different. That is, when the intake high-speed cam 31i is locked, the overlap VO occurs at an earlier timing than when the exhaust high-speed cam 31e is locked. Therefore, the combustion gas flows into the intake system as well as the exhaust system. When such blowback to the intake side occurs, a lot of combustion gas is included in the gas introduced into the combustion chamber in the intake stroke, and the flow rate of the residual gas increases. That is, the internal EGR amount increases. Therefore, when the high-speed cam 31i of the intake system is locked, more residual gas is present in the cylinder than in the exhaust system, and not only during low-speed and low-load operation but also during medium-speed and medium-load operation. However, the frequency of misfire increases. On the other hand, when the high speed cam e of the exhaust system is locked, the frequency of misfire increases only during low speed and low load operation.
[0060]
In consideration of this point, pay attention to the manner in which the misfire detection rate defined in the actual number of misfire detections with respect to the number of misfire detections allowed (possible) by using misfire detection during operation of the internal combustion engine in a specific operation region The detection principle of this embodiment for detecting that at least one high-speed cam 31 is locked in the intake system or the exhaust system will be described with reference to FIGS.
[0061]
As illustrated in FIG. 8, in this embodiment, the engine operation area is classified into three areas. That is, the low-speed and low-load region where the rotational speed NE is smaller than 1500 (rpm) and the intake air amount GN is smaller than 0.2 (g / rev) is classified as the region 1, and 3000 when the rotational speed NE is 1500 (rpm) or more. The medium speed / medium load region smaller than (rpm) and the intake air amount GN being 0.2 (g / rev) or more and smaller than 0.4 (g / rev) is classified as region 2, and the other region is classified as region 3. Classify as
[0062]
On the other hand, for the reasons described above, the misfire detection rate differs as shown in FIG. 9 depending on whether the intake high-speed cam 31i is locked or the exhaust high-speed cam 31e is locked. That is, when the exhaust-system high-speed cam 31e is locked (EX cam Hi-lock), the misfire detection rate increases only in the region 1, while the intake-system high-speed cam i is locked. In the case (IN cam Hi lock), the misfire detection rate increases in region 1 and region 2.
[0063]
Hereinafter, a specific detection operation of the abnormality detection device of the present embodiment that detects a cam switching failure in consideration of this property will be described.
FIGS. 10 to 12 are flowcharts showing a processing procedure of an abnormality detection process executed by the ECU 10 when an abnormality is detected in the variable valve apparatus in the present embodiment. During operation of the internal combustion engine, the ECU 10 periodically repeats this routine for every predetermined crank angle.
[0064]
When this routine is executed, it is first determined in step S100 whether a misfire detection condition is satisfied. As this misfire detection condition, there is a case where fuel cut is not being performed. If it is determined that the same condition is not satisfied, the routine is temporarily terminated.
[0065]
On the other hand, when it is determined that the misfire detection condition is satisfied, “1” is added (incremented) to the count number of the misfire detection permission counter prepared in advance. At the start of this routine, the same count is set to “0”, and when the same count reaches “1001”, it is reset to “1”.
[0066]
Based on the rotation speed NE detected through the crank angle sensor 9 and the intake air amount GN detected through the air flow meter 19 through the series of steps S102 to S109, it is determined to which of the above-mentioned regions the operating region of the engine 1 belongs. It discriminate | determines, based on the discrimination | determination result, memorize | stores these operation area | regions, and increments the misfire detection permission counter prepared beforehand according to these operation area | regions separately. That is, the operation region is determined in steps S102 and S105, and the determined operation region is stored in step S103, S106, or S108. If the operation region is determined to be “region 1”, the region 1 misfire detection permission counter is incremented in step S104. If it is determined to be “region 2”, region 2 is determined in step S107. If the misfire detection permission counter is incremented and it is determined that “area 3”, the area 3 misfire detection permission counter is incremented in step S109. It should be noted that the count numbers of the misfire detection permission counters in these areas 1, 2, and 3 are also set to “0” at the time of start-up, and the count number of the misfire detection permission counter is set to “1001” in step S101. It is set to be reset to “0” when it reaches.
[0067]
In the subsequent step S110 (FIG. 11), misfire determination is performed based on the fluctuation of the rotational speed NE detected through the crank angle sensor 9. In the present embodiment, when the difference ΔNE between the crank angular velocity in the explosion stroke that is the subject of misfire determination and the crank angular velocity measured at a predetermined time before a certain period exceeds a predetermined misfire threshold level value. It is determined that a misfire has occurred.
[0068]
If it is determined by the misfire determination that no misfire has occurred, the process proceeds to step S117. On the other hand, when a misfire is detected, the count number of the misfire counter prepared in advance is incremented by 1 in the count of the number of misfires in step S111. The count is also set to “0” at start-up, and is set to be reset to “0” when the count of the misfire detection permission counter reaches “1001” in step S101. ing.
[0069]
After the misfire counter is incremented in step S111, refer to the region stored in steps S103, S106, and S108 to determine in which operation region the misfire is detected in steps S112 to S116. And a misfire counter prepared in advance for each operation region is individually incremented based on the determination result. That is, when it is determined that “area 1”, the area 1 misfire counter is incremented in step S113, and when it is determined that “area 2”, the area 2 misfire counter is incremented in step S115. If it is determined that “area 3”, the area 3 misfire counter is incremented in step S116. Note that the count numbers of the misfire counters of “area 1”, “area 2”, and “area 3” are also set to “0” at the start, and the count number of the misfire detection permission counter is set in step S101. It is set to be reset to “0” when it reaches “1001”.
[0070]
Next, in step S117, it is determined whether the count number of the misfire permission counter has reached “1000”. If not, the routine is temporarily terminated. On the other hand, if the count number has reached “1000”, the process proceeds to step S118, and it is determined whether or not the number of misfires (count number of the misfire counter) exceeds “60”. If the number of misfires is “60” or less, the process proceeds to step S120 (FIG. 12). If it exceeds “60”, it is determined in step S119 that the misfire is abnormal, and then the process proceeds to step S120. .
[0071]
In step S120, it is determined whether or not the misfire detection permission counter of each region has a sufficient number of counts for determining an abnormality of the variable valve operating apparatus based on the above-described abnormality detection principle of the present embodiment. In the present embodiment, it is determined whether or not the count number exceeds “200” in each area. If there is at least one counter having a count number of “200” or less, this routine is terminated once.
[0072]
Here, the reason why a sufficient value is required for the count number of “region 3” to which the principle of the present embodiment is not directly applied is to determine a misfire abnormality specific to “region 1” and “region 2”. This is because it is necessary to consider the difference in misfire detection rate from other regions.
[0073]
If it is determined in step S120 that sufficient conditions for applying the above principle of the present embodiment are satisfied, the misfire detection rate of “region 3” is determined to be “5%” in step S121. If the condition is satisfied, it is determined in step S122 whether the misfire detection rate of “region 1” is greater than “15%”. Each of these steps S121 and S122 is a condition for determining a misfire abnormality caused by locking of the high-speed cam 31 to which the principle of the present embodiment is applied, and the condition is satisfied in either step. If not, this routine is temporarily terminated.
[0074]
If it is determined that the condition of step S122 is satisfied, it is further determined in step S123 whether or not the misfire detection rate of “region 2” is greater than “15%”. If it is determined that the misfire detection rate of “region 2” is greater than “15%”, the misfire detection rate increases in “region 1” and “region 2”. It is determined that the high-speed cam 31i of the system is locked (IN cam Hi lock abnormality) (step S124). On the other hand, when the misfire detection rate in “region 2” is “15%” or less, the misfire detection rate is increased only in “region 1”. It is determined that it is locked (EX cam Hi lock abnormality) (step S125). When the determination in step S124 or S125 is finished, this routine is once ended.
[0075]
According to the present embodiment in which the abnormality of the variable valve apparatus is detected in the manner described above, the following effects can be obtained.
(1) By monitoring the occurrence frequency (misfire detection rate) of misfires to be detected, it is possible to detect the presence or absence of abnormality of the variable valve system with high accuracy, even with respect to only one cylinder. it can.
[0076]
(2) By monitoring the occurrence frequency of misfires (misfire detection rate) separately for each operation region of the engine, it is possible to further improve the accuracy of detecting the abnormality of the variable valve gear.
[0077]
(3) Further, even when the variable valve systems are provided in the intake system and the exhaust system of these engines, the presence or absence of abnormality of these variable valve systems can be suitably identified and detected. .
[0078]
(4) Since the misfire detection is often performed as a normal process, it is possible to detect an abnormality of the variable valve operating apparatus without providing any special sensor or the like. (Second Embodiment)
Next, a difference between the second embodiment that embodies the present invention and the first embodiment will be described.
[0079]
When the misfire occurrence frequency (misfire detection rate) increases more than a predetermined value, there is a possibility that misfire due to locking of the high-speed cam 31 may occur in a plurality of cylinders such as two cylinders. . That is, when the misfire detection rate becomes a threshold value for determining the occurrence of misfire caused by the locking of the high-speed cam 31 in one cylinder having a value such as “15%”, the misfire detection rate The inventors have confirmed that a value such as “25%” can be determined as a threshold value for determining the occurrence of misfire due to the locking of the high-speed cam 31 in a plurality of cylinders. In this case, the following can be said based on the above-described abnormality detection principle as shown in FIG.
[0080]
(A) When the misfire detection rate in only “region 1” is greater than “15%” and less than or equal to “25%”, the high-speed cam 31e is provided in the variable valve device of one cylinder of the exhaust system. There is a possibility that a switching abnormality from the low speed cam 29e to the low speed cam 29e (one cylinder EX cam Hi lock abnormality) has occurred.
[0081]
(B) When the misfire detection rate only in the “region 1” is larger than the “25%”, the variable valve operating device for a plurality of cylinders in the exhaust system can change from the high speed cam 31e to the low speed cam 29e. Switching abnormality (2-cylinder EX cam Hi lock abnormality) may have occurred.
[0082]
(C) When the misfire detection rate in the “region 1” and “region 2” is larger than the “15%” and less than or equal to the “25%”, the variable valve device for one cylinder of the intake system Therefore, there is a possibility that a switching abnormality from the high speed cam 31i to the low speed cam 29i (one cylinder IN cam Hi lock abnormality) has occurred.
[0083]
(D) The misfire detection rate in “region 1” is greater than “25%”, and the misfire detection rate in “region 2” is greater than “15%” and less than or equal to “25%”. Occasionally, there is an abnormality in switching from the high-speed cam 31 to the low-speed cam 29 (IN cam 1-cylinder EX cam 1-cylinder Hi-lock abnormality) in the variable valve operating device for each cylinder of the intake and exhaust systems. there is a possibility.
[0084]
(E) When the misfire detection rate in the “region 1” is greater than “15%” and the misfire detection rate in the “region 2” is greater than “25%”, a plurality of cylinders in the intake system There is a possibility that a switching abnormality from the high speed cam 31i to the low speed cam 29i (2-cylinder IN cam Hi lock abnormality) has occurred.
[0085]
FIG. 14 is a flowchart showing an abnormality detection processing procedure of the present embodiment for detecting an abnormality of the variable valve apparatus based on such an extension principle. However, in FIG. 14, the processes from step S100 to step S123 (FIGS. 10 to 12) are the same as the processes in the first embodiment, and therefore, the overlapping processes are not shown. In this abnormality detection process, if it is determined in step S123 (FIG. 12) that the misfire detection rate of “region 2” is “15%” or less, the intake-system high-speed cam 31i is Since there is no possibility of being locked, it is determined in step S135 whether the misfire detection rate of “region 1” is greater than “25%”. If the misfire detection rate in “region 1” is greater than “25%”, it is determined that the high-speed cam 31e of the exhaust system of two or more cylinders is locked (EX cam 2-cylinder Hi lock abnormality) ( In step S136), when the misfire detection rate of “region 1” is “25%” or less, it is determined that the high-speed cam 31e of the exhaust system of one cylinder is locked (EX cam one-cylinder Hi lock abnormality). (Step 137).
[0086]
On the other hand, if it is determined in step S123 that the misfire detection rate of “region 2” is greater than “15%”, whether or not the misfire detection rate of “region 2” is greater than “25%” in step S130. If it is larger, it is determined that the intake cam 31i for two or more cylinders is locked (IN cam 2-cylinder Hi lock abnormality) (step S131).
[0087]
If it is determined in step S130 that the misfire detection rate of “region 2” is equal to or lower than “25%”, is the misfire detection rate of “region 1” greater than “25%” in step S132? If it is larger, it is determined that the intake-system high-speed cam 31i and the exhaust-system high-speed cam 31e are locked (IN cam / EX cam one-cylinder Hi lock abnormality) (step S133). ). On the other hand, when the misfire detection rate of “region 1” is “25%” or less, it is determined that the high-speed cam 31i of the intake system of one cylinder is locked (IN cam 1-cylinder Hi lock abnormality). (Step S134).
[0088]
Then, after the end of the steps S131, S133, S134, S136, and S137, this routine is temporarily ended.
According to the present embodiment in which abnormality detection of the variable valve operating apparatus is performed in the above-described manner, the following effects are further obtained in addition to the effects (1) to (4) according to the first embodiment. Be able to.
[0089]
(5) With respect to the variable valve gears arranged in both the intake system and the exhaust system of the internal combustion engine 1, the presence or absence of the switching abnormality and the content of the abnormality can be more accurately identified.
[0090]
The above-described abnormality detecting device for a variable valve device for an internal combustion engine according to the present embodiment may be modified as follows.
In each of the above embodiments, the air flow meter 19 is used as the intake air amount measuring means. However, any method and means such as obtaining the engine load using the intake pressure sensor can be used.
-About the driving | operation area | region set by said each embodiment, and the misfire detection rate used as the reference | standard in those driving | operation area | regions, it can set to arbitrary values according to the kind of engine, the condition where it is installed, etc.
In each of the above embodiments, misfire detection is performed by setting a region that takes advantage of the characteristics of the high-speed cam and the low-speed cam, and abnormality detection of the variable valve operating device is performed based on the occurrence frequency (misfire detection rate). Went. In addition, for example, a variable valve apparatus having a three-stage cam switching characteristic can also be detected by detecting a misfire by setting a region that takes advantage of these characteristics.
In each of the above-described embodiments, it is determined whether the variable valve operating apparatus in which an abnormality related to the cam switching failure has occurred is based on the operation region of the internal combustion engine in which the occurrence frequency of misfire has increased, is on the intake side or on the exhaust side However, the determination on the intake side / exhaust side is not necessarily performed. Similarly, a variable valve gear provided only in one of the intake system and the exhaust system can also be a target for abnormality detection.
In each of the above embodiments, the abnormality of the variable valve gear is detected based on an increase in misfire occurrence frequency (misfire detection) in a specific operation region of the internal combustion engine. Even if the occurrence frequency of misfire is monitored, the presence or absence of abnormality of the variable valve gear can be detected to some extent.
In each of the above embodiments, the misfire occurrence frequency (misfire detection rate) is simply monitored. However, by utilizing the fact that the timing of explosion differs for each cylinder, the misfire occurrence frequency is detected for each cylinder. Also good. As a result, it is possible to know in which cylinder the variable valve operating apparatus has an abnormality.
In each of the above embodiments, misfire detection is performed based on the rotation fluctuation of the crankshaft 7, but means for performing the misfire detection is arbitrary. In addition, for example, misfire detection may be performed based on ion current or the like, and in such a case, by monitoring the occurrence frequency of the detected misfire, the presence or absence of abnormality of the variable valve operating device can be determined. It can be detected with high accuracy.
The variable valve device that is the target of abnormality detection is not limited to the above-described device that makes the lift amount of the engine valve variable. In addition, the present invention can be similarly applied to a device that makes the opening / closing timing of the engine valve variable.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the overall structure of a first embodiment of an abnormality detecting device for a variable valve operating apparatus according to the present invention.
FIG. 2 is a plan view showing a planar structure of a cam switching type variable valve mechanism.
FIG. 3 is a cross-sectional view showing a structure of a lock mechanism of the same mechanism.
FIG. 4 is a cross-sectional view showing the structure of the lock mechanism.
FIG. 5 is a perspective view showing the shape of a hydraulic piston.
FIG. 6 is a graph showing valve lift characteristics of a low speed cam and a high speed cam.
FIG. 7 is a graph showing valve lift characteristics when cam switching failure occurs.
FIG. 8 is a graph showing a division mode of an engine operation region referred to in the first embodiment.
FIG. 9 is a graph showing an abnormality determination mode according to the first embodiment.
FIG. 10 is a flowchart showing an abnormality detection processing procedure according to the first embodiment;
FIG. 11 is a flowchart showing an abnormality detection processing procedure according to the first embodiment;
FIG. 12 is a flowchart showing an abnormality detection processing procedure according to the first embodiment;
FIG. 13 is a graph showing an abnormality determination aspect of the second embodiment of the variable valve operating apparatus of the present invention.
FIG. 14 is a flowchart showing a part of an abnormality detection processing procedure according to the second embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder block, 3 ... Cylinder head, 4 ... Cylinder bore, 5 ... Piston, 6 ... Connecting rod, 7 ... Crankshaft, 8 ... Rotor, 9 ... Crank angle sensor, 10 ... Electronic control unit (ECU) 11) Combustion chamber, 12i ... Intake port, 12e ... Exhaust port, 13 ... Engine valve, 14i ... Intake pipe, 14e ... Exhaust pipe, 15 ... Injector, 16 ... Throttle valve, 17 ... Accelerator pedal, 18 ... Air cleaner, DESCRIPTION OF SYMBOLS 19 ... Air flow meter, 20 ... Cam shaft, 21 ... Cam pulley, 22 ... Timing belt, 23 ... Crank pulley, 24 ... Rocker shaft, 25 ... Rocker arm, 28 ... Valve spring, 29 ... Low speed cam, 31 ... High speed cam, 35 ... spark plug, 50 ... cam changeable variable valve mechanism.

Claims (2)

Yes for detecting the presence or absence of any abnormality on the intake system of the variable valve device and the exhaust system of the variable valve apparatus respectively to vary a valve characteristic of the intake air system and exhaust system of the engine according to the operating state of the internal combustion engine In the abnormality detecting device of the variable valve device,
Misfire detection means for detecting the occurrence of misfire in the engine, the occurrence frequency of misfire detected by the misfire detection means is monitored separately for each operation region of the engine, and based on the misfire occurrence frequency for each operation region to be monitored and a failure detecting means for detecting the presence or absence of abnormality of the variable valve apparatus Te,
Each of the variable valve gears switches a valve characteristic corresponding to the high speed operation of the engine and a valve characteristic corresponding to the low speed operation according to the operation state of the engine,
The abnormality detection means is provided in the variable valve apparatus of the exhaust system on the condition that the misfire occurrence frequency is high only in the low speed and low load operation region based on the misfire occurrence frequency for each operation region to be monitored. It is detected that an abnormality in switching from the valve characteristic corresponding to the low-speed operation to the valve characteristic corresponding to the low-speed operation has occurred, and the misfire occurrence frequency is high in the low-speed low-load operation region and the medium-speed medium-load operation region. In the variable valve device of the intake system, it is detected that a switching abnormality from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation has occurred.
An abnormality detection device for a variable valve operating device. Variable operation for detecting the presence or absence of abnormality in an intake system variable valve device and an exhaust system variable valve device that respectively change the valve characteristics of the intake system and the exhaust system of the engine according to the operating state of the internal combustion engine In the valve device abnormality detection device,
Misfire detection means for detecting the occurrence of misfire in the engine, the occurrence frequency of misfire detected by the misfire detection means is monitored separately for each operation region of the engine, and based on the misfire occurrence frequency for each operation region to be monitored An abnormality detecting means for detecting whether or not the variable valve device is abnormal,
Each of the variable valve gears switches a valve characteristic corresponding to the high speed operation of the engine and a valve characteristic corresponding to the low speed operation according to the operation state of the engine,
The abnormality detection means has a first misfire occurrence frequency higher than a predetermined first value and higher than the first value based on the misfire occurrence frequency for each operation region to be monitored. In the variable valve operating device for one cylinder of the exhaust system on condition that the value is lower than 2, a switching abnormality from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation occurs. The variable valve device for a plurality of cylinders in the exhaust system is compatible with the high speed operation on the condition that the misfire occurrence frequency only in the low speed and low load operation region is higher than the second value. It is detected that a switching abnormality from the valve characteristic to the valve characteristic corresponding to the low speed operation has occurred, and the misfire occurrence frequency in the low speed low load operation region and the medium speed medium load operation region is higher than the first value. Higher and lower than the second value. In the variable valve operating device for one cylinder of the intake system on the condition of the above, it is detected that there is an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation. The misfire occurrence frequency in the load operation region is higher than the second value, and the misfire occurrence frequency in the medium-speed medium load operation region is higher than the first value and lower than the second value. Detecting that there is an abnormality in switching from the valve characteristic corresponding to the high speed operation to the valve characteristic corresponding to the low speed operation in the variable valve operating device of each cylinder of the intake system and the exhaust system as a condition A plurality of the intake systems are provided on the condition that the misfire occurrence frequency in the low speed and low load operation region is higher than the first value and the misfire occurrence frequency in the medium and medium load operation region is higher than the second value. In the variable valve operating device of the cylinder And it detects the fact that the switching abnormality occurs to the valve characteristics corresponding to the low speed operation from the valve characteristic corresponding to
An abnormality detection device for a variable valve operating device.

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