JP2018197505A - Misfire detection device for engine - Google Patents

Abstract

To provide a misfire detection device for an engine, capable of avoiding erroneous misfire detection for the engine during reduced cylinder operation while reducing the torsional vibration of a driving system due to a torque fluctuation of the engine.SOLUTION: The misfire detection device includes a valve stop mechanism control part 12 for changing over from all cylinder operation to reduced cylinder operation to rest the operation of part of cylinders when conditions for executing the reduced cylinder operation are established, a centrifugal damper mechanism D capable of suppressing the occurrence of vibration due to an engine 1, a misfire determination part 13 capable of determining misfire on the basis of an angular speed fluctuation Δω of the engine 1, and an additional load control part 14 for controlling additional loads 42, 43 on the engine 1. When the operation region of the engine 1 is a resonance region A3 where misfire equivalent vibration equivalent to misfire vibration occurs due to the vibration characteristics of the centrifugal damper mechanism D, the additional load control part 14 adds the additional loads 42, 43.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine misfire detection device, and more particularly to an engine misfire detection device including a cylinder number control means and a centrifugal damper means.

Conventionally, a plurality of cylinders and a deactivated cylinder (for example, first to first cylinders) are set from a plurality of cylinders when a condition for executing a reduced-cylinder operation that deactivates some of the plurality of cylinders is established. 2. Description of the Related Art There is known an engine control device that includes a valve stop mechanism that closes intake and exhaust valves of first and fourth cylinders of four cylinders, and a control unit that controls the valve stop mechanism.
During the reduced-cylinder operation, the throttle valve opening is increased and the pumping loss is reduced by increasing the intake air amount of the operating cylinder, so that a fuel efficiency improvement effect can be expected.

By the way, if any of the operating cylinders misfires during the reduced-cylinder operation, the number of operating cylinders contributing to the output of the engine decreases, and as a result, the engine speed may drop significantly and the engine may stop. In addition, the reduced-cylinder operation is prohibited and the entire cylinder operation is restored.
The engine control apparatus disclosed in Patent Document 1 includes a cylinder number control unit that switches from all-cylinder operation to reduced-cylinder operation that stops the operation of some cylinders when an execution condition for reduced-cylinder operation is satisfied, and misfire determination that can determine engine misfire. If the engine speed decreases more than the set value during reduced-cylinder operation, immediately start the operation of the cylinders that are in the inactive state when the ignition timing is reached. doing.

In addition, in a fluid transmission mechanism such as an automatic transmission mechanism or a continuously variable transmission mechanism mounted on a vehicle, a centrifugal damper is used as a dynamic vibration absorber that attenuates vibration in order to reduce torsional vibration of a drive system due to engine torque fluctuation. The mechanism is in use.
As shown in FIG. 7 (a), centrifugal damper mechanisms that reduce the vibration caused by the drive source by bending in the rotational direction when the lockup clutch is engaged are arranged at equal intervals in the circumferential direction on the outer peripheral side of the lockup clutch. A plurality of damper springs 51 are provided.
These damper springs 51 are supported at their circumferential ends by a receiving portion 52a of a spring receiving member 52 extending radially outward from the clutch drum, are connected to the turbine hub, and hold the outer periphery of the damper spring. The other end in the circumferential direction is supported in contact with the receiving portion 53a of the spring holding plate 53.
Thereby, when torque is transmitted from the engine, the damper spring 51 is bent by the centrifugal force, and the spring receiving member 52 is rotated in the rotation direction (see FIG. 7B).

JP 2006-132385 A

However, the number-of-cylinders control unit that switches from the all-cylinder operation to the reduced-cylinder operation that stops the operation of some cylinders when the execution condition of the reduced-cylinder operation is established, and the centrifugal damper unit that can suppress the occurrence of vibration caused by the engine, An engine misfire detection device including misfire determination means capable of determining the possibility of misfire based on engine angular velocity fluctuations may cause erroneous detection of engine misfire.
Normally, misfire of the engine is detected based on fluctuations in the angular velocity of the engine (crankshaft) corresponding to the combustion stroke of each cylinder. Specifically, the number of occurrences of engine angular velocity fluctuations larger than a preset value is counted, and when the count value exceeds a predetermined threshold, engine misfire is detected.

As a result of examination by the present inventor, since the output torque transmitted from the engine is small in the low load region where the reduced cylinder operation is executed, the bending speed of the damper spring 51 held by the spring holding plate 53 is determined by the rotation of the clutch drum. A so-called periodic movement phenomenon occurs in which the circumferential end of the damper spring 51 and the receiving portion 52a of the spring receiving member 52 collide after being separated once (see FIG. 7 (c)). It has been found that the components around the damper spring 51 resonate due to this periodic movement phenomenon.
The resonance caused by the periodic movement phenomenon by the damper spring 51 and the spring receiving member 52 generates a 0.5th order vibration by the crankshaft corresponding to (similar to) the angular speed fluctuation of the engine at the time of actual misfire. That is, the engine angular velocity fluctuation larger than the set value is detected by the 0.5th order vibration caused by the crankshaft corresponding to the misfire, so that the engine does not actually misfire. Regardless, engine misfire is falsely detected.

  An object of the present invention is to provide an engine misfire detection device and the like that can avoid erroneous misfire detection of an engine during reduced-cylinder operation.

  The engine misfire detection device according to claim 1 is a cylinder number control means for switching from all-cylinder operation to reduced-cylinder operation in which operation of some cylinders is stopped when execution conditions for reduced-cylinder operation are satisfied, and generation of vibration caused by the engine. In a misfire detection device for an engine comprising a centrifugal damper means capable of suppressing the misfire, a misfire judgment means capable of judging misfire based on an angular velocity fluctuation of the engine, and an additional load control means for controlling an additional load on the engine And the additional load control means adds an additional load when the engine operating area is a resonance area where a misfire-equivalent vibration corresponding to a misfire vibration occurs due to a vibration characteristic of the centrifugal damper means. It is characterized by that.

Since this engine misfire detection device has misfire determination means capable of determining the possibility of misfire based on fluctuations in the angular velocity of the engine, engine misfire can be detected using the rotational behavior of the crankshaft as a parameter.
Further, when the engine operating region is a resonance region where a misfire-equivalent vibration corresponding to a misfire vibration occurs due to the vibration characteristics of the centrifugal damper unit, the additional load control unit adds an additional load. Therefore, it is possible to prevent the detection of 0.5th order vibrations by the crankshaft induced by the periodic movement phenomenon by deviating the engine operation range from the resonance region without affecting the driving of the engine. Detection can be avoided.

The invention of claim 2 is characterized in that, in the invention of claim 1, the resonance region is set to a low load region in the reduced-cylinder operation region.
According to this configuration, the resonance region can be set accurately.

The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the resonance region is set to a region limited by an upper limit rotation speed and a lower limit rotation speed in the reduced cylinder operation region.
According to this configuration, the resonance region can be set more accurately.

The invention according to claim 4 is capable of suppressing the occurrence of vibration caused by the engine and the cylinder number control means for switching from the all-cylinder operation to the reduced-cylinder operation that stops the operation of some cylinders when the execution condition of the reduced-cylinder operation is satisfied. An engine misfire detection apparatus comprising a centrifugal damper means, comprising: a misfire determination means capable of making a misfire determination based on engine angular velocity fluctuations; and an additional load control means for controlling an additional load on the engine. The additional load control means adds an additional load when the misfire determination means determines a temporary misfire state during the cylinder operation.
According to this configuration, it is possible to prevent the detection of 0.5th-order vibration by the crankshaft induced by the periodic movement phenomenon while avoiding the misdetection of the engine while ensuring the fuel efficiency improvement effect. .

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the misfire determination means determines that a temporary misfire state is present when the number of engine angular speed fluctuations greater than a set value exceeds a first threshold value. The engine is characterized in that it is configured to determine engine misfire when a second threshold value set larger than one threshold value is exceeded.
According to this configuration, it is possible to determine a temporary misfire state that may cause a misfire at a stage before the misfire determination.

A sixth aspect of the invention is characterized in that, in the invention of any one of the first to fifth aspects, the additional load control means controls a load level of an auxiliary machine driven by the engine.
According to this configuration, the output of the engine can be increased without affecting the traveling drive.

  According to the engine misfire detection apparatus of the present invention, it is possible to avoid misdetection of the engine misfire during the reduced-cylinder operation while reducing torsional vibration of the drive system due to engine torque fluctuation.

1 is a partial cross-sectional view illustrating an overall configuration of a powertrain according to a first embodiment. It is a perspective view of a centrifugal damper mechanism. It is the map which set the all cylinder operation area | region and the reduced cylinder operation area | region. It is a flowchart which shows the processing content of cylinder number control. It is a flowchart which shows the processing content of misfire determination. 10 is a flowchart showing the processing contents of cylinder number control according to the second embodiment. It is the principal part enlarged view of a centrifugal damper mechanism, (a) is an initial state, (b) is an operation state at the time of normal, (c) has shown the operation state at the time of a periodic movement phenomenon generation | occurrence | production. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The following description exemplifies a case where the present invention is applied to a vehicle power train, and does not limit the present invention, its application, or its use.

  Embodiment 1 of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the power train P according to the present embodiment includes an engine 1 that is an internal combustion engine, a torque converter 2 that is a fluid transmission mechanism (automatic transmission mechanism), control of the engine 1, and misfire determination of the engine 1. ECU (Electric Control Unit) 10 for performing this.
The engine 1 includes first to fourth cylinders arranged in series, an operation in which two of the four cylinders are deactivated and the remaining cylinders are operated, a so-called reduced cylinder operation, and four cylinders. This is a cylinder deactivation engine capable of appropriately switching between the operation of operating all, that is, the so-called all-cylinder operation.

First, the engine 1 will be described.
The engine 1 includes, in each cylinder, an intake valve (not shown) for supplying intake air into a combustion chamber (not shown), a fuel injection valve (not shown) for injecting fuel toward the combustion chamber, air, A spark plug (not shown) that ignites the fuel mixture, a piston (not shown) that reciprocates, a crankshaft 3 that rotates by the reciprocating motion of the piston, and a crankcase (not shown) that houses the crankshaft 3 And an exhaust valve (not shown) for exhausting exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber to an exhaust passage (not shown), etc., are provided respectively. First cylinder → 3rd cylinder → 4th cylinder → Ignition is performed in the order of the second cylinder.

The engine 1 includes an opening sensor 4 that detects the throttle valve opening of the engine 1, a rotation speed sensor 5 that detects the rotation speed of the engine 1, a torque sensor 6 that detects the output torque of the engine 1, and a crankshaft 3. An angular velocity sensor 7 for detecting the rotational angular velocity is provided, and the measured values of the sensors 4 to 7 are output to the ECU 10, respectively.
The ECU 10 is electrically connected to a warning lamp 41, a generator alternator 42, an air conditioner 43, and the like disposed on an instrument panel (not shown).

The warning lamp 41 is configured to be turned on when the misfire determination is confirmed (actual misfire determination).
The alternator 42 is driven by the engine 1 (crankshaft 3) via a drive belt or the like. The alternator 42 is configured to be switchable between an operating state and a non-operating state. Similarly, the air conditioner 43 (compressor) is driven by the engine 1 via a drive belt or the like. The alternator 42 and the air conditioner 43 are auxiliary machines driven by the engine 1 and correspond to an additional load for controlling the load on the engine 1 without affecting the running state.

Next, the torque converter 2 will be described.
As shown in FIG. 1, the entire torque converter 2 is connected to a crankshaft 3 via a crank bolt and is configured to be driven by the engine 1.
The torque converter 2 includes a pump 21, a turbine 22, a stator 23, a one-way clutch 24, a lock-up clutch 25, damper springs 26 and 27, a case 28 containing these components, and a centrifugal damper mechanism. D (centrifugal damper means) and the like, and the case 28 is filled with oil as a power transmission fluid.

The damper springs 26 and 27 are configured to be able to reduce vibration caused by the engine 1 (crankshaft 3) by bending in the rotational direction when the lockup clutch 25 is engaged.
As shown in FIG. 2, a plurality of damper springs 26 and 27 are arranged at equal intervals in the circumferential direction, and each is provided so as to overlap in the axial direction.
As shown in FIG. 1, the damper spring 26 is formed integrally with the clutch drum 29 so that one end in the circumferential direction is in contact with a receiving portion 30 a provided on a spring receiving member 30 extending radially outward from the clutch drum 29. The other end in the circumferential direction is supported in contact with a receiving portion 31 a provided on a spring holding plate 31 that is supported and covers the outer periphery of the damper spring 26.

The inner peripheral end of the spring holding plate 31 is connected to the turbine hub 32 via a rivet, and is elastically connected in the rotational direction via the spring receiving member 30 and the damper spring 26 therebetween. Accordingly, when the lockup clutch 25 is engaged, the rotation of the crankshaft 3 is input to the spring receiving member 30 via the lockup clutch 25 and transmitted to the spring holding plate 31 (turbine hub 32) via the damper spring 26. The
The damper spring 27 is provided in the radial middle step of the spring holding plate 31 and has a torsion spring rigidity higher than that of the damper spring 26. As a result, the torsional operating angle can be widened, and the vibration of the drive system caused by the torque fluctuation of the engine 1 is attenuated.
Therefore, the damper springs 26 and 27, the spring receiving member 30, the spring holding plate 31, and the like correspond to the centrifugal damper mechanism D.

Next, the ECU 10 will be described.
The ECU 10 performs all-cylinder operation by the first to fourth cylinders when the execution condition for all-cylinder operation is satisfied, and stops the operation by the first and fourth cylinders when the execution condition for reduced-cylinder operation is satisfied. Thus, the reduced cylinder operation by the second and third cylinders is executed.
Further, the ECU 10 determines the possibility of misfire of each cylinder based on the angular speed fluctuation of the crankshaft 3 and performs all-cylinder operation when the misfire of the engine 1 is determined.
The ECU 10 includes a CPU (Central Processing Unit), a ROM, a RAM, an in-side interface, an out-side interface, and the like.

  As shown in FIG. 1, the ECU 10 includes an operation condition determination unit 11 that can determine the operation state of the engine 1, a valve stop mechanism control unit 12 (cylinder number control means) that can control the operating cylinder, and a misfire determination unit 13. (Misfire determination means) and an additional load control unit 14 (additional load control means) capable of controlling an additional load.

As shown in FIG. 3, the operation condition determination unit 11 includes an all-cylinder operation region A1, a reduced-cylinder operation region A2 that occupies a low-torque region of the all-cylinder operation region A1, and a low-torque region of the reduced-cylinder operation region A2. A map in which the resonance region A3 occupying is set is stored in advance. The operation condition determination unit 11 determines which operation execution condition is satisfied based on the map and the measured values of the sensors 5 and 6.
The all-cylinder operation region A1 is set by an upper limit torque line L1 corresponding to the throttle valve being fully opened. The reduced-cylinder operation region A2 is set in the region from low to high rotation, and the upper limit torque line L2 that rises rearward and tilts the maximum torque during loss-cylinder operation, loss region branching torque, intake pulsation restriction, etc. It is set based on.

The resonance region A3 is included in the reduced-cylinder operation region A2, and is set to a low torque region (for example, −5 to +5 Nm) that is limited by an upper limit rotational speed (for example, 3500 rpm) and a lower limit rotational speed (for example, 1500 rpm). ing.
Specifically, this corresponds to a driving state such as downhill footrest deceleration.
In the low torque region of the reduced-cylinder operation, there may be a periodic movement phenomenon in which one end portion in the circumferential direction of the damper spring 26 and the receiving portion 30a of the spring receiving member 30 collide after being separated once. The accompanying resonance generates a 0.5th order vibration caused by the crankshaft 3 in the same manner as the misfire vibration associated with the angular velocity fluctuation Δω that occurs during the actual misfire of the engine 1, so that the engine 1 is not misfired. Misfire may be falsely detected.
Therefore, the operating condition determination unit 11 determines a resonance region A3 in which 0.5th order vibration is generated by the crankshaft 3 which is vibration corresponding to misfire based on a periodic movement phenomenon.

The valve stop mechanism control unit 12 switches between execution of all-cylinder operation and reduced-cylinder operation based on the determination result of the operation condition determination unit 11. Specifically, the hydraulic pressure supplied to the HLA (not shown) of the first and fourth cylinders during the reduced-cylinder operation while allowing the intake and exhaust valves of the first to fourth cylinders to open and close during all-cylinder operation. Is maintained at the closed state holding hydraulic pressure, and the intake and exhaust valves of the deactivated cylinder are maintained in the closed state.
The valve stop mechanism control unit 12 corrects the opening of the throttle valve so that the total torque (requested torque) output from the engine 1 during the reduced-cylinder operation becomes substantially constant, and corrects the first and fourth cylinders. The operation of the fuel injection valve is prohibited.

The misfire determination unit 13 determines the number of times that the negative angular velocity fluctuation Δω becomes larger than a preset set value α in a predetermined measurement time based on the measurement value of the angular velocity sensor 7 that detects the rotational angular velocity of the crankshaft 3. Misfire count count C.
When the measured number of times C exceeds the first threshold value N1, it is determined as a temporary misfire state, and when the number of times C exceeds the second threshold value N2 (N1 <N2), an actual misfire (determined misfire) is determined. ing.
When the provisional misfire state is determined, the provisional misfire determination flag F1 is set to 1. When the misfire confirmation is determined, the failure determination flag F2 is set to 1. When normal, both the flags F1 and F2 are set to 0. Has been. When the flag F2 is 1, the misfire determination unit 13 lights the warning lamp 42.
The values of the flags F1 and F2 are continuously stored as the latest history information, and the latest history of these flags F1 and F2 is used for maintenance and repair.

The additional load control unit 14 is configured to add an additional load in the resonance region A3 based on the determination result of the operating condition determination unit 11. In order to suppress the periodic movement phenomenon of the centrifugal damper mechanism D, the additional load control unit 14 controls the amount of air supplied to the engine 1 so as to correspond to the increase amount of the additional load due to the addition of the additional load. Increase control.
That is, the additional load control unit 14 has an additional load increasing function and an air amount increasing function.
As a result, the operating region of the engine 1 can be removed from the resonance region A3 without affecting the traveling drive, and as a result, the detection of the 0.5th order vibration by the crankshaft 3 induced by the periodic movement phenomenon. And misdetection of misfire of the engine 1 is avoided.

  Further, the additional load control unit 14 controls the load level so that the load due to the additional load increases as the torque of the engine 1 decreases. Specifically, when the output torque of the engine 1 is less than the torque T1, the operation of the alternator 43 is started. When the output torque of the engine 1 is less than the torque T2 (T1 <T2), the operation of the air conditioner 44 is performed in addition to the operation of the alternator 43. Start.

Next, the contents of the cylinder number control process will be described based on the flowchart of FIG.
Si (i = 1, 2,...) Indicates steps for each process.

As shown in the flowchart of FIG. 4, first, in S1, the outputs, maps, and various information of the sensors 4 to 7 are read, and the process proceeds to S2.
In S2, it is determined whether or not the operation state is the reduced cylinder operation region A2.
As a result of the determination in S2, when the operation state is the reduced cylinder operation region A2, the process proceeds to S3.
As a result of the determination in S2, if the operating state is not the reduced cylinder operation area A2, since it is the all cylinder operation area A1, the all cylinder operation is executed (S7), and the process returns.

In S3, it is determined whether or not the failure determination flag F2 is zero.
As a result of the determination in S3, if the failure determination flag F2 is 0, none of the operating cylinders have misfired, so the process proceeds to S4. If the failure determination flag F2 is not 0 as a result of the determination in S3, one of the operating cylinders has misfired, and the process proceeds to S7.
As a result, it is possible to avoid the stop of the engine 1 due to a significant decrease in the rotational speed of the engine 1.

In S4, it is determined whether or not the resonance region A3.
If the result of determination in S4 is the resonance region A3, there is a possibility that 0.5th order vibration will be generated by the crankshaft 3, so additional load control is executed (S5), and the routine proceeds to S6.
If the result of determination in S4 is that the region is not the resonance region A3, there is no possibility that 0.5th order vibration will be generated by the crankshaft 3, and therefore the process proceeds to S6.
In S6, the reduced-cylinder operation is executed and the process returns.

Next, the misfire determination processing content will be described based on the flowchart of FIG.
The misfire determination process is repeatedly executed at a predetermined cycle by the misfire determination unit 13 and is executed in parallel with the cylinder number control process shown in FIG. That is, while the cylinder number control process is being performed, the temporary misfire determination flag F1 and the failure determination flag F2 are determined at any time.

As shown in the flowchart of FIG. 5, first, in S11, the outputs of the sensors 4 to 7 and various information are read.
Next, in S12, the misfire count number C is reset to 0, and the process proceeds to S13.
In S13, it is determined whether or not the angular velocity fluctuation Δω is larger than the set value α.
If the angular velocity fluctuation Δω is larger than the set value α as a result of the determination in S13, the number of times C is set to C + 1 (S14), and the process proceeds to S16. In this case, the number C is maintained (S15), and the process proceeds to S16.

In S16, it is determined whether or not the measurement time has ended.
If the measurement time ends as a result of the determination in S16, the process proceeds to S17. If the measurement time has not ended as a result of the determination in S16, the measurement is continued until the measurement time ends.
In S17, it is determined whether or not the number of times C has exceeded the first threshold value N1.
As a result of the determination in S17, when the number of times C exceeds the first threshold value N1, the process proceeds to S18.
In S18, it is determined whether or not the number of times C has exceeded the second threshold value N2.
If the number of times C exceeds the second threshold value N2 as a result of the determination in S18, the failure determination flag F2 is set to 1 (S19), and the process proceeds to S22. If the number of times C is equal to or smaller than the second threshold N2 as a result of the determination in S18, the temporary misfire determination flag F1 is set to 1 (S20), and the process returns.
In S22, after the warning lamp 42 is turned on, the process returns.

As a result of the determination in S17, when the number of times C is equal to or less than the first threshold value N1, the process proceeds to S23.
In S23, it is determined whether or not the failure determination flag F2 is 1.
As a result of the determination in S23, when the failure determination flag F2 is 1, the actual misfire determination is performed in the previous misfire determination, but the misfire has been resolved in the current misfire determination, so the failure determination flag F2 is set to 0 (S24). After the warning light 41 is turned off (S25), the process proceeds to S21.
As a result of the determination in S23, when the failure determination flag F2 is not 1, since the actual misfire determination has not been performed in the previous misfire determination, the process proceeds to S21.
In S21, the temporary misfire determination flag F1 is set to 0, and the process returns.

Next, the operation and effect of the engine misfire detection apparatus will be described.
According to the present misfire detection device, the misfire determination unit 13 that can determine the possibility of misfire based on the angular velocity fluctuation Δω of the engine 1 is provided, and therefore misfire of the engine 1 is detected using the rotational behavior of the crankshaft 3 as a parameter. can do.
Further, when the operation region of the engine 1 is a resonance region in which a misfire-equivalent vibration corresponding to a misfire vibration occurs due to the vibration characteristics of the centrifugal damper mechanism D, the additional load control unit 14 performs an additional load (alternator 42). In order to add the air conditioner 43), the 0.5th-order vibration by the crankshaft 3 induced by the periodic movement phenomenon is caused by deviating the operation region of the engine 1 from the resonance region A3 without affecting the traveling drive. Detection can be prevented, and misfire detection of the engine 1 can be avoided.

Since the resonance region A3 is set in the low load region in the reduced-cylinder operation region A2, the resonance region A3 can be set accurately.
Since the resonance region A3 is set to a region limited by the upper limit rotation speed and the lower limit rotation speed in the reduced cylinder operation region A2, the resonance region A3 can be set more accurately.

  Since the additional load control unit 14 controls the load level of the auxiliary machine driven by the engine 1, the output of the engine 1 can be increased without affecting the traveling drive.

Next, cylinder number control according to the second embodiment will be described based on the flowchart of FIG.
In the first embodiment, in the resonance region A3, the additional load control unit 14 executes the additional load control regardless of the presence or absence of the misfire equivalent vibration. In the second embodiment, after the occurrence of the misfire equivalent vibration, The additional load control unit 14 performs additional load control.

As shown in the flowchart of FIG. 6, first, in S31, the outputs, maps, and various information of the sensors 4 to 7 are read, and the process proceeds to S32.
In S32, it is determined whether or not the operation state is the reduced cylinder operation region A2.
As a result of the determination in S32, when the operation state is the reduced cylinder operation region A2, the process proceeds to S3.
If the result of determination in S32 is that the operating state is not the reduced-cylinder operation region A2, since it is the all-cylinder operation region A1, all-cylinder operation is executed (S38) and the process returns.

In S33, it is determined whether or not the failure determination flag F2 is 0.
As a result of the determination in S33, if the failure determination flag F2 is 0, it is not an actual misfire, so the process proceeds to S34. As a result of the determination in S33, if the failure determination flag F2 is not 0, it is determined that the actual misfire has been determined, and thus the process proceeds to S38.
In S34, it is determined whether or not the temporary misfire determination flag F1 is zero.
As a result of the determination in S34, when the temporary misfire determination flag F1 is 0, it is not a temporary misfire state, so the process proceeds to S36.

In S36, it is determined whether or not a predetermined time has elapsed since the temporary misfire determination flag F1 is changed from 1 to 0.
As a result of the determination in S36, when the predetermined misfire determination flag F1 is changed from 1 to 0 and a predetermined time has elapsed, the switching of the valve operating mechanism is surely completed. To do.
If the result of determination in S34 is that the temporary misfire determination flag F1 is not 0, and if the result of determination in S36 is that the temporary misfire determination flag F1 has changed from 1 to 0 and the predetermined time has not elapsed, then additional load control is performed. Is executed (S35), and the process proceeds to S37.

According to this configuration, it is possible to prevent the detection of 0.5th-order vibration by the crankshaft 3 induced by the periodic movement phenomenon while avoiding misdetection of misfire of the engine 1 while ensuring the fuel efficiency improvement effect. Can do.
The misfire determination unit 13 determines that the misfire state is in a temporary misfire state when the number C of angular velocity fluctuations Δω of the engine 1 that is larger than the set value α exceeds the first threshold value N1, and is set to be greater than the first threshold value N1. Since it has been configured to determine misfire of the engine 1 when the threshold value N2 is exceeded, it is possible to determine a temporary misfire state that may cause misfire in a stage before the misfire determination.

Next, a modified example in which the embodiment is partially changed will be described.
1) In the above embodiment, an example of an in-line four-cylinder gasoline engine has been described. However, the present invention can be applied without being limited to an engine type such as a six-cylinder engine or a V-type engine. It is not limited to cylinder gasoline engines.
Further, the example of the engine that performs the reduced cylinder operation in which half of the four cylinders are deactivated has been described, but the number of deactivated cylinders may be arbitrarily set.

2) In the above embodiment, an example of the centrifugal damper mechanism constituted by the damper spring, the spring receiving member, and the spring holding plate has been described. However, the resonance caused by the periodic movement phenomenon causes fluctuations in the angular velocity of the engine during actual misfire. As long as it has a weight, a material, and a structure that generate a 0.5th-order vibration by the crankshaft as well as the accompanying vibration, it is not limited to the configuration of this embodiment.

3] In the above-described embodiment, an example in which the possibility of misfire of four cylinders is measured using a single angular velocity sensor provided on the crankshaft has been described. However, an angular velocity sensor may be provided for each cylinder.
Moreover, it is also possible to use the differential value of the measured value of the rotation angle sensor instead of the angular velocity sensor.

4] In the embodiment, as an additional load, an auxiliary machine driven by the engine increases the auxiliary machine load by an alternator or an air conditioner that controls the load on the engine without directly affecting the running state. However, it is sufficient if at least the output torque (load) of the engine can be increased, and the pumping loss of the engine such as the opening / closing timing of the intake / exhaust valve and the stroke of the piston may be increased. Accordingly, the additional load includes the pumping loss of the engine in addition to the auxiliary load.

5] In addition, those skilled in the art can implement the present invention in a form in which various modifications are added to the above-described embodiment or in a form in which each embodiment is combined without departing from the spirit of the present invention. Various modifications are also included.

DESCRIPTION OF SYMBOLS 1 Engine 12 Valve stop mechanism control part 13 Misfire determination part 14 Additional load control parts 26 and 27 Damper spring 30 Spring receiving member 31 Spring holding plate 42 Alternator 43 Air conditioner D Centrifugal damper mechanism

Claims (6)

Cylinder number control means for switching from all-cylinder operation to reduced-cylinder operation that stops the operation of some cylinders when a condition for executing reduced-cylinder operation is established, and a centrifugal damper means that can suppress the occurrence of vibration caused by the engine Engine misfire detection device,
Misfire determination means capable of determining misfire based on engine angular speed fluctuation,
An additional load control means for controlling an additional load on the engine,
When the engine operating region is a resonance region in which a misfire-equivalent vibration corresponding to a misfire vibration occurs due to a vibration characteristic of the centrifugal damper unit, the additional load control unit adds an additional load. Engine misfire detection device.   The engine misfire detection apparatus according to claim 1, wherein the resonance region is set to a low load region in the reduced-cylinder operation region.   3. The engine misfire detection device according to claim 1, wherein the resonance region is set in a region limited by an upper limit rotational speed and a lower limit rotational speed in the reduced-cylinder operation region. Cylinder number control means for switching from all-cylinder operation to reduced-cylinder operation that stops the operation of some cylinders when a condition for executing reduced-cylinder operation is established, and a centrifugal damper means that can suppress the occurrence of vibration caused by the engine Engine misfire detection device,
Misfire determination means capable of determining misfire based on engine angular speed fluctuation,
An additional load control means for controlling an additional load on the engine,
The engine misfire detection apparatus, wherein the additional load control means adds an additional load when the misfire determination means determines a temporary misfire state during the reduced-cylinder operation. The misfire determination means determines that a temporary misfire state has occurred when the number of engine angular speed fluctuations greater than a set value exceeds a first threshold, and exceeds a second threshold set greater than the first threshold. When configured to determine engine misfire,
5. The engine misfire detection apparatus according to claim 4, wherein the additional load control unit adds an additional load when the misfire determination unit determines that the misfire determination unit is in a temporary misfire state. 6.   The engine misfire detection device according to any one of claims 1 to 5, wherein the additional load control means controls a load level of an auxiliary machine driven by the engine.