Internal combustion engine system and misfire determining method for internal combustion engine

An influence component N30m of every 30 degrees in a 30 degree rotation speed N30 base as time required for 30 degree rotation of a crankshaft is calculated by using a frequency characteristic of an influence given to a rotation fluctuation of a crankshaft by output torque output from a motor, which is calculated by using a mechanical model and an amplitude P and a phase q at a time of vibration control by the motor, a determination duration T30j is calculated by subtracting an influence component T30m as an inverse number of this from 30 degree duration T30, and misfire of an engine is determined by comparing the calculated determination duration T30j with a threshold value Tref. Thereby, misfire of the engine outputting power to a post-stage via a damper can be determined more reliably and accurately.

TECHNICAL FIELD

The present invention relates to an internal combustion engine system, a misfire determining method for an internal combustion engine, and a vehicle equipped with the internal combustion engine system, and more particularly relates to an internal combustion engine system having a multi-cylinder internal combustion engine capable of outputting power to a drive shaft via a torsional element, a misfire determining method for the multi-cylinder internal combustion engine capable of outputting power to the drive shaft via the torsional element, and a vehicle equipped with the internal combustion system.

BACKGROUND ART

Conventionally, as an internal combustion engine system of this kind, there is proposed the one that determines misfire of an engine based on a torque correction amount of a motor at the time of vibration control for canceling off a torque fluctuation of the engine by the motor in a vehicle mounted with the motor that is capable of generating electric power and connected to the crankshaft of the engine (for example, see Patent Document 1). In this system, a misfire is determined based on the rotation fluctuation at a crank angle position when vibration control by the motor is not carried out, and when the engine is operated at high rotation with high torque even though the vibration control by the motor is carried out, and misfire of the engine is determined based on the torque correction amount of the motor at the time of vibration control when the engine is operated at low rotation or operated with low torque while the vibration control by the motor is carried out.

DISCLOSURE OF THE INVENTION

When the vibration control by the motor is conducted, determination of misfire becomes difficult with the conventional misfire determining method as in the above describe system, but the factor which makes determination of misfire difficult is not limited to such vibration control. For example, when an engine is connected to a transmission or the like via a torsional element such as a damper which is used for the purpose of suppressing torque fluctuation of the engine, the entire transmission including the damper resonates depending on the operation point of the engine, and determination of misfire becomes difficult.

It is an object of the present invention to provide an internal combustion system, a misfire determining method for the internal combustion engine and a vehicle that ensure reliable determination of the misfire of the multi-cylinder internal combustion engine capable of outputting power to the drive shaft via a torsional element such as a damper. Further, it is an object of the present invention to provide the internal combustion system, the misfire determining method for the internal combustion engine and the vehicle that ensure accurate determination of the misfire of the multi-cylinder internal combustion engine capable of outputting power to the drive shaft via a torsional element such as a damper.

In order to attain at least part of the above described objects, the internal combustion system, the misfire determining method for the internal combustion engine and the vehicle of the present invention adopts the following measures.

The present invention according to one aspect is an internal combustion engine system having a multi-cylinder internal combustion engine capable of outputting power to a drive shaft via a torsional element, said internal combustion engine system comprising: a rotation regulating module connected to an output shaft of said internal combustion engine via said torsional element and connected to said drive shaft to be capable of regulating a rotation speed and rotation fluctuation of the internal combustion engine; a rotational position detecting module detecting a rotational position of the output shaft of said internal combustion engine; a rotation fluctuation calculating module calculating the rotation fluctuation of said internal combustion engine based on said detected rotational position; an influence component calculating module calculating an influence component given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and the rotation fluctuation of said internal combustion engine by said rotation regulating module; and a misfire determining module determining whether or not any of cylinders of said internal combustion engine misfires based on said calculated rotation fluctuation of the internal combustion engine and said calculated influence component.

In the internal combustion engine system of the present invention, the rotation fluctuation of the internal combustion engine is calculated based on a rotational position of the output shaft of the internal combustion engine, an influence component, which is given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and rotation fluctuation of the internal combustion engine by the rotation regulating module, is calculated, and based on the calculated rotation fluctuation of the internal combustion engine and the calculated influence component, it is determined whether or not any of cylinders of the internal combustion engine misfires. Specifically, misfire is determined by considering the influence component given to the rotation fluctuation of the internal combustion engine by the rotation regulating module. Thereby, misfire of the internal combustion engine outputting power to the drive shaft via the torsional element can be determined more reliably and accurately.

In such an internal combustion engine of the present invention, the influence component calculating module may be a module calculating the influence component based on a transfer function in an influence given to the rotation fluctuation of the internal combustion engine with respect to torque output of the rotation regulating module, which is obtained by solving an equation of motion for a mechanical model including the internal combustion engine, the torsional element and the rotation regulating module, and an amplitude and a phase of the torque output of the rotation regulating module.

Further, in the internal combustion engine system of the present invention, the misfire determining module may be a module which determines misfire based on an influence-removed rotation fluctuation which is a rotation fluctuation obtained by subtracting the calculated influence component from the calculated rotation fluctuation of the internal combustion engine. In this case, the misfire determining module may be a module which determines that misfire is occurring when an inverse number of the influence-removed rotation fluctuation is not less than a threshold value.

Further, in the internal combustion engine system of the present invention, the rotation regulating module may be a module capable of inputting and outputting power from and to the output shaft and the drive shaft with input and output of electric power and power. In this case, the rotation regulating module may be a module which includes a three shaft-type power input and output module which is connected to three shafts that are the output shaft of the internal combustion engine, the drive shaft and a rotating shaft, and based on power inputted to and outputted from any two shafts of the three shafts, inputs and outputs power to and from the remaining shaft, and a motor capable of inputting and outputting power to and from the rotating shaft.

The present invention according to another aspect is a misfire determining method for an internal combustion engine for determining misfire of said internal combustion engine in an internal combustion engine system including a multi-cylinder internal combustion engine, and a rotation regulating module connected to an output shaft of said internal combustion engine via a torsional element and connected to a drive shaft to be capable of regulating a rotation speed and rotation fluctuation of the internal combustion engine, wherein the rotation fluctuation of said internal combustion engine is calculated based on a rotational position of the output shaft of said internal combustion engine, an influence component, which is given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and rotation fluctuation of said internal combustion engine by said rotation regulating module, is calculated, and based on a rotation fluctuation obtained by subtracting said calculated influence component from said calculated rotation fluctuation of the internal combustion engine, it is determined whether or not any of cylinders of said internal combustion engine misfires.

In a misfire determining method of an internal combustion engine of the present invention, the rotation fluctuation of the internal combustion engine is calculated based on a rotational position of the output shaft of the internal combustion engine, an influence component, which is given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and rotation fluctuation of the internal combustion engine by the rotation regulating module, is calculated, and based on the calculated rotation fluctuation of the internal combustion engine and the calculated influence component, it is determined whether or not any of cylinders of the internal combustion engine misfires. Specifically, misfire is determined by considering the influence component given to the rotation fluctuation of the internal combustion engine by the rotation regulating module. Thereby, misfire of the internal combustion engine outputting power to the drive shaft via the torsional element can be determined more reliably and accurately.

In the misfire determining method of the present invention, the influence component may be calculated based on a transfer function in an influence given to the rotation fluctuation of said internal combustion engine with respect to torque output of said rotation regulating module, which is obtained by solving an equation of motion for a mechanical model including said internal combustion engine, said torsional element and said rotation regulating module, and an amplitude and a phase of the torque output of said rotation regulating module.

In the misfire determining method of the present invention, misfire may be determined based on influence-removed rotation fluctuation which is rotation fluctuation obtained by subtracting said calculated influence component from said calculated rotation fluctuation of the internal combustion engine.

The present invention according to another aspect is a vehicle comprising: a multi-cylinder internal combustion engine capable of outputting power to a drive shaft connected to an axle via a torsional element; a rotation regulating module connected to an output shaft of said internal combustion engine via said torsional element and connected to said drive shaft to be capable of regulating a rotation speed and rotation fluctuation of the internal combustion engine; a rotational position detecting module detecting a rotational position of the output shaft of said internal combustion engine; a rotation fluctuation calculating module calculating the rotation fluctuation of said internal combustion engine based on said detected rotational position; an influence component calculating module calculating an influence component given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and rotation fluctuation of said internal combustion engine by said rotation regulating module; and a misfire determining module determining whether or not any of cylinders of said internal combustion engine misfires based on said calculated rotation fluctuation of the internal combustion engine and said calculated influence component.

In a vehicle of the present invention, the rotation fluctuation of the internal combustion engine is calculated based on a rotational position of the output shaft of the internal combustion engine, an influence component, which is given to the rotation fluctuation of the internal combustion engine by regulation of the rotation speed and rotation fluctuation of the internal combustion engine by the rotation regulating module, is calculated, and based on the calculated rotation fluctuation of the internal combustion engine and the calculated influence component, it is determined whether or not any of cylinders of the internal combustion engine misfires. Specifically, misfire is determined by considering the influence component given to the rotation fluctuation of the internal combustion engine by the rotation regulating module. Thereby, misfire of the internal combustion engine outputting power to the drive shaft via the torsional element can be determined more reliably and accurately.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the best mode for carrying out the present invention will be described by using an embodiment.FIG. 1is a configuration diagram showing the outline of the configuration of a hybrid automobile20equipped with an internal combustion engine system which is one embodiment of the present invention. The hybrid automobile20of the embodiment includes an engine22, a three-axis power distribution and integration mechanism30which is connected to a crankshaft26as an output shaft of the engine22via a damper28as a torsional element, a motor MG1which is connected to the power distribution and integration mechanism30and capable of generating electric power, a reduction gear35mounted to a ring gear shaft32aas a drive shaft connected to the power distribution and integration mechanism30, a motor MG2connected to the reduction gear35, and a hybrid electronic control unit70which controls the entire vehicle. Here, the engine22, the power distribution and integration mechanism30connected to the engine22via the damper28, the motor MG1, and an engine electronic control unit24mainly correspond to the internal combustion engine system of the embodiment.

The engine22is a six-cylinder internal combustion engine that consumes a hydrocarbon fuel, such as gasoline or light oil, to output power. As shown inFIG. 2, the air cleaned by an air cleaner122and taken in via a throttle valve124is mixed with the atomized gasoline injected by a fuel injection valve126to the air-fuel mixture. The air-fuel mixture is introduced into a combustion chamber via an intake valve128. The introduced air-fuel mixture is ignited with spark made by a spark plug130to be explosively combusted. The reciprocating motions of a piston132by the combustion energy are converted into rotational motions of a crankshaft26. The exhaust from the engine22goes through a catalytic conversion unit134(filled with three-way catalyst) to convert toxic components included in the exhaust, that is, carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), into harmless components, and is discharged to the outside air.

The engine22is under control of an engine electronic control unit24(hereafter referred to as engine ECU24). The engine ECU24is constructed as a microprocessor including a CPU24a, a ROM24bthat stores processing programs, a RAM24cthat temporarily stores data, input and output ports (not shown), and a communication port (not shown). The engine ECU24receives, via its input port, signals from various sensors that measure and detect the conditions of the engine22. The signals input into the engine ECU24include a crank position from a crank position sensor140detected as the rotational position of the crankshaft23, a cooling water temperature from a water temperature sensor142measured as the temperature of cooling water in the engine22, a cam position from a cam position sensor144detected as the rotational position of a camshaft driven to open and close the intake valve128and an exhaust valve for gas intake and exhaust into and from the combustion chamber, a throttle valve position from a throttle valve position sensor146detected as the opening or position of the throttle valve124, an air flow meter signal AF from an air flow meter148attached to an air intake conduit, an intake air temperature from a temperature sensor149attached to the air intake conduit, an air-fuel ratio AF from an air-fuel ratio sensor135a, and an oxygen signal from an oxygen sensor135b. The engine ECU24outputs, via its output port, diverse control signals and driving signals to drive and control the engine22, for example, driving signals to the fuel injection valve126, driving signals to a throttle valve motor136for regulating the position of the throttle valve124, control signals to an ignition coil138integrated with an igniter, and control signals to a variable valve timing mechanism150to vary the open and close timings of the intake valve128. The engine ECU24communicates with the hybrid electronic control unit70. The engine ECU24receives control signals from the hybrid electronic control unit70to drive and control the engine22, while outputting data regarding the driving conditions of the engine22to the hybrid electronic control unit70according to the requirements.

The power distribution and integration mechanism30has a sun gear31that is an external gear, a ring gear32that is an internal gear and is arranged concentrically with the sun gear31, multiple pinion gears33that engage with the sun gear31and with the ring gear32, and a carrier34that holds the multiple pinion gears33in such a manner as to allow free revolution thereof and free rotation thereof on the respective axes. Namely the power distribution and integration mechanism30is constructed as a planetary gear mechanism that allows for differential motions of the sun gear31, the ring gear32, and the carrier34as rotational elements. The carrier34, the sun gear31, and the ring gear32in the power distribution and integration mechanism30are respectively coupled with the crankshaft26of the engine22, the motor MG1, and the reduction gear35via ring gear shaft32a. While the motor MG1functions as a generator, the power output from the engine22and input through the carrier34is distributed into the sun gear31and the ring gear32according to the gear ratio. While the motor MG1functions as a motor, on the other hand, the power output from the engine22and input through the carrier34is combined with the power output from the motor MG1and input through the sun gear31and the composite power is output to the ring gear32. The power output to the ring gear32is thus finally transmitted to the driving wheels63aand63bvia the gear mechanism60, and the differential gear62from ring gear shaft32a.

Both the motors MG1and MG2are known synchronous motor generators that are driven as a generator and as a motor. The motors MG1and MG2transmit electric power to and from a battery50via inverters41and42. Power lines54that connect the inverters41and42with the battery50are constructed as a positive electrode bus line and a negative electrode bus line shared by the inverters41and42. This arrangement enables the electric power generated by one of the motors MG1and MG2to be consumed by the other motor. The battery50is charged with a surplus of the electric power generated by the motor MG1or MG2and is discharged to supplement an insufficiency of the electric power. When the power balance is attained between the motors MG1and MG2, the battery50is neither charged nor discharged. Operations of both the motors MG1and MG2are controlled by a motor electronic control unit (hereafter referred to as motor ECU)40. The motor ECU40receives diverse signals required for controlling the operations of the motors MG1and MG2, for example, signals from rotational position detection sensors43and44that detect the rotational positions of rotors in the motors MG1and MG2and phase currents applied to the motors MG1and MG2and measured by current sensors (not shown). The motor ECU40outputs switching control signals to the inverters41and42. The motor ECU40communicates with the hybrid electronic control unit70to control operations of the motors MG1and MG2in response to control signals transmitted from the hybrid electronic control unit70while outputting data relating to the operating conditions of the motors MG1and MG2to the hybrid electronic control unit70according to the requirements.

The battery50is under control of a battery electronic control unit (hereafter referred to as battery ECU)52. The battery ECU52receives diverse signals required for control of the battery50, for example, an inter-terminal voltage measured by a voltage sensor (not shown) disposed between terminals of the battery50, a charge-discharge current measured by a current sensor (not shown) attached to the power line54connected with the output terminal of the battery50, and a battery temperature Tb measured by a temperature sensor51attached to the battery50. The battery ECU52outputs data relating to the state of the battery50to the hybrid electronic control unit70via communication according to the requirements. The battery ECU52calculates a state of charge (SOC) of the battery50, based on the accumulated charge-discharge current measured by the current sensor, for control of the battery50.

The hybrid electronic control unit70is constructed as a microprocessor including a CPU72, a ROM74that stores processing programs, a RAM76that temporarily stores data, and a non-illustrated input-output port, and a non-illustrated communication port. The hybrid electronic control unit70receives various inputs via the input port: an ignition signal from an ignition switch80, a gearshift position SP from a gearshift position sensor82that detects the current position of a gearshift lever81, an accelerator opening Acc from an accelerator pedal position sensor84that measures a step-on amount of an accelerator pedal83, a brake pedal position BP from a brake pedal position sensor86that measures a step-on amount of a brake pedal85, and a vehicle speed V from a vehicle speed sensor88. The hybrid electronic control unit70communicates with the engine ECU24, the motor ECU40, and the battery ECU52via the communication port to transmit diverse control signals and data to and from the engine ECU24, the motor ECU40, and the battery ECU52, as mentioned previously.

The hybrid vehicle20of the embodiment thus constructed calculates a torque demand to be output to the ring gear shaft32afunctioning as the drive shaft, based on observed values of a vehicle speed V and an accelerator opening Acc, which corresponds to a driver's step-on amount of an accelerator pedal83. The engine22and the motors MG1and MG2are subjected to operation control to output a required level of power corresponding to the calculated torque demand to the ring gear shaft32a. The operation control of the engine22and the motors MG1and MG2selectively effectuates one of a torque conversion drive mode, a charge-discharge drive mode, and a motor drive mode. The torque conversion drive mode controls the operations of the engine22to output a quantity of power equivalent to the required level of power, while driving and controlling the motors MG1and MG2to cause all the power output from the engine22to be subjected to torque conversion by means of the power distribution integration mechanism30and the motors MG1and MG2and output to the ring gear shaft32a. The charge-discharge drive mode controls the operations of the engine22to output a quantity of power equivalent to the sum of the required level of power and a quantity of electric power consumed by charging the battery50or supplied by discharging the battery50, while driving and controlling the motors MG1and MG2to cause all or part of the power output from the engine22equivalent to the required level of power to be subjected to torque conversion by means of the power distribution integration mechanism30and the motors MG1and MG2and output to the ring gear shaft32a, simultaneously with charge or discharge of the battery50. The motor drive mode stops the operations of the engine22and drives and controls the motor MG2to output a quantity of power equivalent to the required level of power to the ring gear shaft32a.

Next, the operation at the time of determining whether any cylinder of the engine22, which is mounted on the hybrid automobile20of the embodiment thus configured, misfires or not will be described.FIG. 3is a flowchart showing an example of a misfire determination process routine which is executed by the engine ECU24. The routine is repeatedly executed every predetermined time.

When the misfire determination process is executed, the CPU24aof the engine ECU24executes the process of inputting data required for misfire determination such as an amplitude P and a phase θ of torque pulsation in the vibration control for suppressing rotation fluctuation of a post-stage side from the damper28by the motor MG1, a crank angle CA from the crank position sensor140, a 30 degree duration T30which is the time required for rotation of 30 degrees of the crank angle CA which is calculated by a T30calculation process shown as an example inFIG. 4(step S100). The motor ECU40controls the motor MG1to output the torque as the sum of the torque for regulating the rotation speed Ne of the engine22and the torque for canceling off rotation fluctuation, which is in the inverse phase with respect to the rotation fluctuation of the post-stage from the damper28for suppressing the rotation fluctuation of the post-stage side of the damper28, and therefore, the amplitude P and the phase θ of the torque pulsation in the vibration control by the motor MG1can be obtained from fluctuation of a torque command Tm1* for the motor MG1by the motor ECU40. The 30 degree duration T30can be obtained from the T30calculation process shown as an example inFIG. 4which is executed by the engine ECU24, that is, by inputting the crank angle CA at every 30 degrees from the reference crank angle (step S200), calculating a 30 degree rotation speed N30by dividing the crank angle CA at every 30 degrees by the time required for rotating the crankshaft26by 30 degrees (step S210), and by taking the inverse number of the calculated 30 degree rotation speed N30(step S220).

After the data is thus input, an influence component N30mof the 30 degree rotation speed N30base of the rotation fluctuation is calculated by using the frequency characteristic of the influence given to the rotation fluctuation of the crankshaft26by the output torque of the motor MG1, and the amplitude P and the phase θ of the torque pulsation in the vibration control by the motor MG1that are input (step S110). An example of the Bode diagram of the frequency characteristic of the influence which is given to the rotation fluctuation of the crankshaft26by the output torque of the motor MG1in the hybrid automobile20of the embodiment is shown inFIG. 5. In the embodiment, the frequency characteristic is calculated by using a mechanical model shown inFIG. 6ignoring the influence of the post-stage from the motor MG1. InFIG. 6, “Ie” represents inertia of the engine22, “Kdamp” represents a spring constant of the damper28, “Cdamp” represents a damping coefficient of the damper28, “Iinp” represents inertia of the input shaft (shaft between the damper28and the power distribution and integration mechanism30) of the power distribution and integration mechanism30, and “Img1” represents inertia of the motor MG1. When the equations of motion are established for the two inertia systems by using this, the following equations (1) and (2) are obtained. In equations (1) and (2), “ωe” represents a rotation angular velocity of the crankshaft26, “ωinp” represents a rotation angular velocity of the input shaft of the power distribution and integration mechanism30, “θe” represents a torsion angle per unit length of the crankshaft26, “θinp” represents a torsion angle per unit length of the input shaft of the power distribution and integration mechanism30, “Te” represents engine torque, “Tmg1” represents output torque of the motor MG1, and dots on the tops of “ωe” and “ωinp” show that “ωe” and “ωinp” are differentiated by one time. Now that the influence on the crankshaft26with respect to the torque of the motor MG1is considered, if the value of the engine torque Te is set as zero, equation (3) is obtained. Here, when the matrix at the left of the left side of equation (3) is set as “P”, the matrix at the left of the first term of the right side is set as “A”, the matrix at the left of the second term of the right side is set as “B”, the matrix at the right of the first term of the right side is set as “x”, and the output torque Tmg1of the motor MG1is set as “u”, equation (3) is expressed as equation (4). The rotation angular velocity ωe of the crankshaft26becomes the left half of equation (5) when expressed by using “x”, and when the matrix at the left of the right side of the left half of equation (5) is set as “C”, the rightmost side of equation (5) is obtained. By solving equation (4) by using the relationship, equation (6) can be derived as a transfer function G (s) of the influence which the output torque Tmg1of the motor MG1exerts on the rotation angular speed (ωe) of the crankshaft26. In the embodiment, the transfer function G(s) is obtained by such calculation, and the frequency characteristic is obtained from this. From this frequency characteristic and the amplitude P and the phase θ of the torque pulsation in the vibration control by the motor MG1, the influence component which the output torque Tmg1of the motor MG1exerts on the rotation angular speed (ωe) of the crankshaft26is obtained as the rotation fluctuation at every 30 degrees (influence component N30m).

Subsequently, the inverse number of the obtained influence component N30mis taken, and an influence component T30mof the degree duration T30base is calculated (step S120), and a determination duration T30jis calculated by subtracting the influence component T30mfrom the input 30 degree duration T30(step S130). The determination duration T30jis the duration from which the influence of the vibration control by the motor MG1is removed, namely, the duration from which the influence of resonance by the damper28is removed when resonance is caused by the damper28. Subsequently, it is determined whether or not the determination duration T30jis larger than a threshold value Tref (step S140), when the determination duration T30jis larger than the threshold value Tref, it is determined that misfire occurs, and the cylinder which misfires is identified based on the input crank angle CA (step S150), and the misfire determination process is finished. In this case, the threshold value Tref is set at the value larger than the determination duration T30jwhen the cylinder which is in the combustion stroke at the crank angle CA as the reference of the determination duration T30jdoes not misfire, and smaller than the determination duration T30jwhen the cylinder misfires, and can be obtained by the experiment or the like. The cylinder which misfires can be identified as the cylinder which is in the combustion stroke at the crank angle CA that is the reference of the determination duration T30jexceeding the threshold value Tref.

According to the internal combustion engine system mounted on the hybrid automobile20of the embodiment described above, misfire is determined by using the determination duration T30jfrom which the influence of vibration control by the motor MG1is removed, and therefore, misfire of the engine22which outputs power to the post-stage through the damper28as the torsional element can be determined more reliably and accurately. Accordingly, even when resonance by the damper28occurs, misfire of the engine22can be determined more reliably and accurately.

In the internal combustion engine system mounted on the hybrid automobile20of the embodiment, the frequency characteristic of the influence which the output torque of the motor MG1gives to the rotation fluctuation of the crankshaft26is calculated by using the mechanical model ignoring the influence of the post-stage from the motor MG1, but the frequency characteristic may be calculated by using the mechanical model also considering the influence of the post-stage from the motor MG1.

In the internal combustion engine system mounted on the hybrid automobile20of the embodiment, misfire of the engine22is determined by using the 30 degree duration T30as the time required for 30 degree rotation of the crankshaft26at every 30 degrees, but misfire of the engine22may be determined by using various durations such as five degree duration time T5as the time required for five degree rotation of the crankshaft26at every five degrees, and 10 degree duration T10as the time required for 10 degree rotation of the crankshaft26at every 10 degrees.

In the internal combustion engine system mounted on the hybrid automobile20of the embodiment, the determination duration T30jis calculated by subtracting the influence component T30mof the 30 degree duration T30base calculated by using the mechanical model from the 30 degree duration T30, and misfire of the engine22is determined from the calculated determination duration T30j. However, the determination duration may be calculated by subtracting the influence component of a 30 degree duration T30base which is obtained without using the mechanical model from the 30 degree duration T30, and misfire of the engine22may be determined from the calculated determination duration. As one example of the method for obtaining the influence component of the 30 degree duration T30base without using the mechanical model, the influence of the 30 degree duration T30base which is given to the rotation fluctuation of the crankshaft26with respect to the amplitude P and the phase θ of the torque pulsation in the vibration control by the motor MG1is obtained in advance by an experiment or the like, and is stored in the ROM24bas a map, and when the amplitude P and the phase θ are given, a corresponding influence component of the 30 degree duration T30base is derived according to the map.

In the hybrid automobile20of the embodiment, misfire of the engine22in the system including the power distribution and integration mechanism30which is connected to the crankshaft26of the engine22via the damper28as the torsional element, and is connected to the ring gear shaft32aas the rotating shaft and the drive shaft of the motor MG1, and the motor MG2which is connected to the ring gear shaft32avia the reduction gear35, but the present invention may be applied to any engine system in which the crankshaft of the engine is connected to the motor or the like capable of regulating the rotation speed of the engine via the damper as the torsional element. Therefore, misfire of the engine22may be determined in the system in which the power of the motor MG2is connected to an axle (axle connected to wheels64aand64binFIG. 7) different from the axle (axle to which the drive wheels63aand63bare connected) to which the ring gear shaft32ais connected as shown as an example in a hybrid automobile120of a modified example ofFIG. 7, or misfire of the engine22may be determined in the system including a pair rotor motor230which has an inner rotor232connected to the crankshaft26of the engine22via the damper28and an outer rotor234connected to the drive shaft outputting the power to the drive wheels63aand63b, transmits part of the power of the engine22to the drive shaft, and converts the residual power into electric power.

Further, the internal combustion engine system is not limited to the internal combustion engine system mounted on such a hybrid automobile, but may be the internal combustion engine system having an internal combustion engine mounted on a movable body other than an automobile, or an internal combustion engine incorporated in immobile equipment such as construction equipment. Further, the present invention may be in the mode of the misfire determining method for an internal combustion engine.

The embodiment discussed above is to be considered in all aspects as illustrative and not restrictive. There may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention. The scope and spirit of the present invention are indicated by the appended claims, rather than by the foregoing description.

INDUSTRIAL APPLICABILITY

The present invention is applicable to the manufacturing industry of the internal combustion engine systems having internal combustion engines and automobiles equipped with them.