Engine System

Abstract

To highly accurately determine misfire of an engine.SOLUTION: An engine system includes: an engine having a crank shaft; a crank angle sensor that detects a rotating angle of the crank shaft; a dual mass flywheel connected to the crank shaft; and a calculation section that calculates hysteresis torque of the dual mass flywheel on the basis of a grease temperature that is a temperature of grease filled in the dual mass flywheel and calculates crank angle speed on the basis of the rotating angle of the crank shaft and the hysteresis torque changing according to the grease temperature.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an engine system. [Background technology]

[0002] A flywheel is attached to the engine crankshaft to absorb torque fluctuations that occur during the engine's operating stroke. Some flywheels are called dual mass flywheels (hereinafter referred to as DMF), which have a spring between the first and second flywheels to absorb torque fluctuations from the engine and transmission.

[0003] Patent Document 1 discloses a misfire detection control device for an engine equipped with a DMF. Patent Document 1 discloses that when the engine speed is within the resonant frequency band of the DMF and the number of misfires is equal to or less than a first threshold and exceeds a second threshold, the engine speed is changed so as to deviate from the resonant frequency band. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 62-23512 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the resonance characteristics of the DMF change depending on the temperature of the grease sealed inside the DMF. The misfire detection control device described in Patent Document 1 does not take into account the temperature of the grease sealed inside the DMF, and therefore cannot accurately detect misfires in engines equipped with a DMF.

[0006] In view of the above circumstances, an object of the present invention is to make a highly accurate determination of engine misfire. [Means for solving the problem]

[0007] In order to solve the above problem, an engine system according to one embodiment of the present invention comprises: an engine having a crankshaft; a crank angle sensor that detects a rotation angle of the crankshaft; a dual mass flywheel connected to the crankshaft; a calculation unit that calculates a hysteresis torque of the dual mass flywheel based on a grease temperature, which is the temperature of the grease sealed in the dual mass flywheel, and calculates a crank angular velocity based on the hysteresis torque that varies depending on the rotational angle of the crankshaft and the grease temperature; Equipped with. [Effects of the Invention]

[0008] According to the present invention, it is possible to determine engine misfire with high accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an engine system according to this embodiment. [Figure 2] FIG. 2 is a block diagram showing the functions of the control device. [Figure 3] FIG. 3 is a flowchart of the misfire determination process executed by the control device. [Figure 4] FIG. 4 is a flowchart of the grease temperature estimation process. [Figure 5] FIG. 5 is a flowchart of the hysteresis torque calculation process. [Figure 6] FIG. 6 is a flowchart of the torsion angle calculation process. [Figure 7] FIG. 7 is a graph showing an example of the relationship between each engine speed, each hysteresis torque, and each torsion angle. [Figure 8] FIG. 8 is a flowchart of the torsion influence coefficient calculation process. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0011] [1. Overall configuration of engine system 100] Fig. 1 is a schematic diagram showing an engine system 100 according to this embodiment. As shown in Fig. 1, the engine system 100 includes an engine 200, a crank angle detection device 300, a DMF 400, a clutch 500, a transmission 600, and a control device 700. The engine system 100 according to this embodiment is mounted on a vehicle 1, for example.

[0012] [2. Engine 200 Configuration] Engine 200 includes cylinder 201, piston 202, connecting rod 203, crankshaft 204, combustion chamber 205, intake valve 206, intake camshaft 207, intake cam 208, exhaust valve 209, exhaust camshaft 210, exhaust cam 211, timing belt 212, and injector 213. In this embodiment, engine 200 is a horizontally opposed engine. However, engine 200 is not limited to this, and may be an in-line engine or a V-type engine.

[0013] The cylinders 201 are formed in a cylindrical shape. In this embodiment, four cylinders 201 are provided in the engine 200. However, the number of cylinders 201 is not limited to this and may be, for example, one (single), two, three, or five or more. The cylinders 201 are arranged opposite each other in the horizontal direction across the crankshaft 204. For example, two cylinders 201 are arranged on the left side of the crankshaft 204 in FIG. 1 and two cylinders 201 are arranged on the right side of the crankshaft 204 in FIG. 1.

[0014] Piston 202 is disposed in cylinder 201 and configured to be slidable along the central axis of cylinder 201. Piston 202 moves back and forth within cylinder 201 as fuel is combusted in combustion chamber 205.

[0015] The connecting rod 203 connects the piston 202 to the crankshaft 204. When the piston 202 reciprocates within the cylinder 201, the connecting rod 203 reciprocates together with the piston 202.

[0016] The crankshaft 204 is connected to the piston 202 via a connecting rod 203. The crankshaft 204 converts the reciprocating motion of the piston 202 into rotational force.

[0017] Combustion chamber 205 is formed by the crown surface of piston 202 and the inner surface of cylinder 201. An injection hole of injector 213 and an ignition portion of a spark plug (not shown) are arranged inside combustion chamber 205. When fuel is injected from injector 213 and the spark plug is ignited, the fuel burns inside combustion chamber 205, increasing the combustion pressure inside combustion chamber 205. In response to the combustion pressure inside combustion chamber 205, piston 202 reciprocates inside cylinder 201.

[0018] Intake valve 206 is disposed in an intake port (not shown) that communicates with combustion chamber 205. An umbrella portion of intake valve 206 is disposed between the intake port and combustion chamber 205. Intake valve 206 moves in the direction of the central axis to open and close the intake port.

[0019] Intake camshaft 207 is formed in a substantially cylindrical shape. Intake camshaft 207 extends in the direction of the central axis of crankshaft 204. Intake camshaft 207 is configured to be rotatable around the central axis. A pair of intake camshafts 207 is provided, one on the left side and one on the right side of crankshaft 204 in FIG. 1. Intake camshaft 207 is connected to intake valve 206 via intake cam 208.

[0020] Intake cam 208 is formed in a teardrop shape. Intake cam 208 is attached to intake camshaft 207. Intake cam 208 is formed integrally with intake camshaft 207. Therefore, when intake camshaft 207 rotates, intake cam 208 rotates integrally with intake camshaft 207. Intake cam 208 is provided so as to always abut against intake valve 206. When intake cam 208 rotates, intake valve 206 moves in the direction of the central axis according to the external shape of intake cam 208, opening and closing the intake port.

[0021] Exhaust valve 209 is disposed in an exhaust port (not shown) that communicates with combustion chamber 205. The head portion of exhaust valve 209 is disposed between the exhaust port and combustion chamber 205. Exhaust valve 209 moves in the direction of the central axis to open and close the exhaust port.

[0022] The exhaust camshaft 210 is formed in a substantially cylindrical shape. The exhaust camshaft 210 extends in the direction of the central axis of the crankshaft 204. The exhaust camshaft 210 is configured to be rotatable around the central axis. A pair of exhaust camshafts 210 are provided, one on the left side and one on the right side of the crankshaft 204 in FIG. 1. The exhaust camshafts 210 are connected to the exhaust valves 209 via exhaust cams 211.

[0023] The exhaust cam 211 is formed in a teardrop shape. The exhaust cam 211 is attached to the exhaust camshaft 210. The exhaust cam 211 is formed integrally with the exhaust camshaft 210. Therefore, when the exhaust camshaft 210 rotates, the exhaust cam 211 rotates integrally with the exhaust camshaft 210. The exhaust cam 211 is provided so as to be in constant contact with the exhaust valve 209. When the exhaust cam 211 rotates, the exhaust valve 209 moves in the direction of the central axis in accordance with the outer shape of the exhaust cam 211, opening and closing the exhaust port.

[0024] Timing belt 212 is wound around crankshaft 204, intake camshaft 207, and exhaust camshaft 210. Timing belt 212 transmits the rotation of crankshaft 204 to intake camshaft 207 and exhaust camshaft 210. Intake camshaft 207 and exhaust camshaft 210 rotate in conjunction with the rotation of crankshaft 204.

[0025] The injector 213 has an injection hole for injecting fuel, and injects the fuel into the combustion chamber 205 at a predetermined timing.

[0026] Engine 200 is filled with engine oil, which serves as a coolant for cooling various parts of engine 200 and as a lubricant for lubricating piston 202, crankshaft 204, etc. The engine oil is stored in an oil pan (not shown) provided at the bottom of engine 200.

[0027] An oil temperature sensor 214 that detects the temperature of engine oil (hereinafter referred to as engine oil temperature) is provided in engine 200. Oil temperature sensor 214 outputs an oil temperature signal that indicates the engine oil temperature.

[0028] 3. Configuration of crank angle detection device 300 Crank angle detection device 300 includes disc plate 301 and crank angle sensor 302. Disc plate 301 is attached to crankshaft 204 and rotates integrally with crankshaft 204. Disc plate 301 is made of a magnetic material.

[0029] Disc plate 301 has a plurality of teeth on the outer periphery of its disk-shaped body, and crank angle sensor 302 is provided radially outward of the plurality of teeth. Crank angle sensor 302 includes a coil and a magnet. Crank angle sensor 302 outputs a crank angle detection signal based on a change in magnetic field caused by contact and separation of the plurality of teeth as disc plate 301 rotates. Crank angle sensor 302 can detect the rotation angle of crankshaft 204 based on the contact and separation of the plurality of teeth of disc plate 301.

[0030] [4.DMF400 Configuration] The DMF 400 includes a first flywheel 401, a second flywheel 402, and a shock absorber 403. The first flywheel 401 is connected to the crankshaft 204.

[0031] The second flywheel 402 is provided at a distance from the first flywheel 401 in the central axial direction of the crankshaft 204. The shock absorber 403 is provided between the first flywheel 401 and the second flywheel 402. The first flywheel 401 and the second flywheel 402 are connected via the shock absorber 403. A plurality of shock absorbers 403 are provided in the circumferential direction of the first flywheel 401 and the second flywheel 402.

[0032] The shock absorber 403 includes a spring, which is an elastic member, and a chamber that houses the spring. The spring is arranged so that it can be compressed in the rotational direction of the crankshaft 204. The chamber is filled with grease, which is a viscous medium.

[0033] One end of the shock absorber 403 is connected to the first flywheel 401, and the other end of the shock absorber 403 is connected to the second flywheel 402. By interposing the shock absorber 403 between the first flywheel 401 and the second flywheel 402, torsional vibrations caused by combustion fluctuations in the engine 200 can be damped.

[0034] [5. Clutch 500 Configuration] Clutch 500 includes a clutch disc 501 that is movable in the direction of the central axis of crankshaft 204 relative to second flywheel 402. When clutch disc 501 approaches second flywheel 402 and is pressed against second flywheel 402, the power of engine 200 is transmitted to transmission 600 via clutch disc 501. When clutch disc 501 moves away from second flywheel 402, the transmission of power from engine 200 to transmission 600 is interrupted.

[0035] [6. Transmission 600 Configuration] Transmission 600 includes a plurality of gears 601, a plurality of shafts 602, an oil temperature sensor 603, and a transmission rotation speed sensor 604. Transmission 600 is connected to DMF 400 via clutch disc 501 of clutch 500. Transmission 600 changes the torque, rotation speed, and rotation direction of the power of engine 200 and transmits it to wheels (not shown) in the downstream stage.

[0036] Further, transmission 600 is filled with mission oil as a lubricant for lubricating multiple gears 601. The mission oil is stored in an oil pan (not shown) provided below transmission 600.

[0037] An oil temperature sensor 603 that detects the temperature of the mission oil (hereinafter referred to as the mission oil temperature) is provided in the transmission 600. The oil temperature sensor 603 outputs an oil temperature signal that indicates the mission oil temperature.

[0038] The transmission 600 is also provided with a transmission rotation speed sensor 604 that detects the rotation speed of a shaft 602 connected to the clutch disc 501. The transmission rotation speed sensor 604 outputs a rotation speed signal that indicates the rotation speed of the shaft 602 connected to the clutch disc 501.

[0039] 7. Configuration of Control Device 700 The control device 700 includes one or more processors 700a and one or more memories 700b connected to the processors 700a. The processors 700a include, for example, a CPU (Central Processing Unit).

[0040] The memory 700b includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM is a storage element that stores programs and calculation parameters used by the CPU. The RAM is a storage element that temporarily stores data such as variables and parameters used in processing executed by the CPU.

[0041] The various processes performed by the control device 700 can be executed by the processor 700a. In particular, the various processes are performed by the processor 700a executing a program stored in the memory 700b.

[0042] The functions of the control device 700 according to this embodiment may be divided among multiple control devices, or multiple functions may be realized by one control device. When the functions of the control device 700 are divided among multiple control devices, the multiple control devices may be connected to each other via a communication bus such as a CAN.

[0043] 2 is a block diagram showing the functions of the control device 700. A processor 700a of the control device 700 works in cooperation with a memory 700b to function as a calculation unit 701 and a determination unit 702. The control device 700 acquires various signals output from the oil temperature sensor 214, the crank angle sensor 302, the oil temperature sensor 603, and the transmission rotation speed sensor 604.

[0044] Calculation unit 701 calculates the rotation angle of crankshaft 204, i.e., the crank angle, based on the crank angle detection signal output from crank angle sensor 302. If a misfire occurs in engine 200, the rotation angular velocity of disc plate 301 decreases. If the angular acceleration of disc plate 301 decreases, the pulse interval of the crank angle detection signal output from crank angle sensor 302 increases.

[0045] The determination unit 702 determines that the engine is misfiring when, for example, the pulse interval of the crank angle detection signal becomes larger than a misfire determination threshold value that is predetermined according to the rotation speed of the engine 200 (hereinafter referred to as the engine rotation speed). In this way, the determination unit 702 can determine the misfire state of the engine 200 according to the pulse interval of the crank angle detection signal. In other words, the determination unit 702 can determine the misfire state of the engine 200 according to the rotational angular velocity of the crankshaft 204.

[0046] Furthermore, calculation unit 701 calculates engine oil temperature and transmission oil temperature based on the oil temperature signal. Furthermore, calculation unit 701 calculates the rotation speed of shaft 602 of transmission 600 connected to clutch disc 501 based on the rotation speed signal. Furthermore, calculation unit 701 calculates the rotation angle, rotation angular velocity, engine rotation speed, etc. of crankshaft 204 based on the crank angle detection signal.

[0047] [8. Misfire detection process flow] Fig. 3 is a flowchart of the misfire detection process executed by the control device 700. As shown in Fig. 3, first, the control device 700 acquires the oil temperature signal output from the oil temperature sensors 214, 603, the crank angle detection signal output from the crank angle sensor 302, and the rotation speed signal output from the transmission rotation speed sensor 604 (S100). After acquiring the various signals, the calculation unit 701 executes the grease temperature estimation process (S200).

[0048] 4 is a flowchart of the grease temperature estimation process. As shown in Fig. 4, calculation unit 701 calculates the engine oil temperature at engine start-up based on the oil temperature signal output from oil temperature sensor 214 (S210). Similarly, calculation unit 701 calculates the transmission oil temperature at engine start-up based on the oil temperature signal output from oil temperature sensor 603 (S210).

[0049] The calculation unit 701 estimates the grease temperature at engine start based on the engine oil temperature and the transmission oil temperature at engine start (S220). Here, the memory 700b stores map information of grease temperatures associated with each engine oil temperature and each transmission oil temperature. The map information of grease temperatures is, for example, values ​​obtained in advance by experiments or the like. The calculation unit 701 references the map information of grease temperatures and estimates the grease temperature at engine start corresponding to the engine oil temperature and the transmission oil temperature at engine start.

[0050] The calculation unit 701 calculates the engine rotation speed based on the crank angle detection signal, and calculates the transmission rotation speed based on the rotation speed signal (S230). The calculation unit 701 calculates the amount of heat input to the grease in the DMF 400 based on the engine rotation speed. The calculation unit 701 also calculates the amount of heat input to the grease in the DMF 400 based on the transmission rotation speed. Here, the memory 700b stores map information of the amount of heat input to the grease in the DMF 400 associated with each engine rotation speed, and the amount of heat input to the grease in the DMF 400 associated with each transmission rotation speed. The map information of the amount of heat input is, for example, a value obtained in advance by experiment or the like.

[0051] The calculation unit 701 refers to map information of the amount of heat input and calculates the amount of heat input to the grease in the DMF 400 that corresponds to the current engine rotation speed and transmission rotation speed.The calculation unit 701 then estimates the grease temperature after the amount of heat input is added to the grease temperature at engine start as the current grease temperature (S240).In this way, the calculation unit 701 calculates the current grease temperature based on the engine rotation speed and the transmission rotation speed.

[0052] Here, the grease temperature affects the shear torque of the grease between the first flywheel 401 and the second flywheel 402 in the DMF 400. Therefore, the calculation unit 701 calculates a temperature coefficient for correcting the shear torque of the grease in the DMF 400 based on the current grease temperature (S250). Here, the memory 700b stores map information of the temperature coefficient associated with the grease temperature. The map information of the temperature coefficient is, for example, a value obtained in advance by an experiment or the like.

[0053] The calculation unit 701 refers to the map information of the temperature coefficient, calculates the temperature coefficient corresponding to the current grease temperature, and ends the grease temperature estimation process. Returning to Fig. 3, after the grease temperature estimation process, the calculation unit 701 executes a hysteresis torque calculation process (S300).

[0054] 5 is a flowchart of the hysteresis torque calculation process. As shown in FIG. 5, the calculation unit 701 calculates a reference hysteresis torque resulting from the internal configuration of the DMF 400 (S310). The reference hysteresis torque includes, for example, a shear torque of the grease that occurs when the first flywheel 401 and the second flywheel 402 rotate relative to each other, and a viscous resistance that occurs when the grease is compressed. The reference hysteresis torque also includes, for example, a constant hysteresis torque that occurs due to sliding between the components when the first flywheel 401 and the second flywheel 402 rotate relative to each other, and a torque that occurs due to the reaction force of a spring.

[0055] Here, the hysteresis torque fluctuates under the influence of the grease temperature. Therefore, the calculation unit 701 performs a process of correcting the reference hysteresis torque using the temperature coefficient calculated in S250. Specifically, the calculation unit 701 calculates the hysteresis torque according to the grease temperature by multiplying the reference hysteresis torque by the temperature coefficient (S320). Here, the temperature coefficient is used to calculate the hysteresis torque of the DMF 400 taking the grease temperature into consideration. This makes it possible to calculate the hysteresis torque of the DMF 400 with high accuracy according to the current grease temperature. After calculating the hysteresis torque in S320, the calculation unit 701 ends the hysteresis torque calculation process.

[0056] Returning to FIG. 3, after the hysteresis torque calculation process, the calculation unit 701 executes the torsion angle calculation process (S400).

[0057] FIG. 6 is a flowchart of the torsion angle calculation process. As shown in FIG. 6, calculation unit 701 acquires the engine speed calculated in S230 and the hysteresis torque calculated in S320 (S410). Here, memory 700b stores map information in which the torsion angle of DMF 400 corresponding to each engine speed and each hysteresis torque is associated. The map information is a value obtained by, for example, pre-modeling the hysteresis torque of DMF 400 and the torsion angle corresponding to the engine speed. Calculation unit 701 refers to the map information and calculates the current torsion angle of DMF 400 based on the current engine speed and the current hysteresis torque (S420).

[0058] 7 is a graph showing an example of the relationship between each engine speed, each hysteresis torque, and each torsion angle. In Fig. 7, the horizontal axis represents the torsion angle, which is the relative rotation angle between the first flywheel 401 and the second flywheel 402, and the vertical axis represents the hysteresis torque of the DMF 400.

[0059] In addition, in Figure 7, the relationship between torsion angle and hysteresis torque at first engine speed R1 is shown by a solid line, and the relationship between torsion angle and hysteresis torque at second engine speed R2 is shown by a dashed line. In addition, in Figure 7, the relationship between torsion angle and hysteresis torque at third engine speed R3 is shown by a dashed line, and the relationship between torsion angle and hysteresis torque at fourth engine speed R4 is shown by a two-dot chain line. The magnitude relationship among the first engine speed R1, second engine speed R2, third engine speed R3, and fourth engine speed R4 is R1>R2>R3>R4.

[0060] As shown in FIG. 7, the torsion angle changes depending on the hysteresis torque and engine speed. Furthermore, the higher the engine speed, the greater the hysteresis torque. Note that the lower the grease temperature, the greater the viscosity, so the lower the grease temperature, the greater the hysteresis torque. As can be seen from FIG. 7, once the current engine speed and current hysteresis torque have been calculated, the current torsion angle can be calculated. After calculating the torsion angle in S420, the calculation unit 701 ends the torsion angle calculation process.

[0061] Returning to FIG. 3, after the torsion angle calculation process, the calculation unit 701 executes the torsion influence coefficient calculation process (S500).

[0062] FIG. 8 is a flowchart of the torsion influence coefficient calculation process. As shown in FIG. 8, calculation unit 701 acquires the engine speed calculated in S230 and the torsion angle calculated in S420 (S510). In this embodiment, the amount of change in the difference in crank angular velocity during the combustion stroke of each cylinder of engine 200, which changes depending on the torsion angle of DMF 400, is acquired in advance through experiments. A coefficient reflecting the influence on the difference in crank angular velocity depending on the torsion angle is defined as the torsion influence coefficient. Memory 700b stores map information in which each engine speed, each torsion angle, and each torsion influence coefficient are associated with each other.

[0063] The calculation unit 701 refers to the map information and calculates the current torsion influence coefficient based on the current engine speed and the current torsion angle (S520). After calculating the torsion influence coefficient in S520, the calculation unit 701 ends the torsion influence coefficient calculation process.

[0064] Returning to Fig. 3, after the torsion influence coefficient calculation process, calculation unit 701 calculates a determination difference based on the torsion influence coefficient and the difference in crank angular velocity during the combustion stroke of each cylinder of engine 200 (S600). The determination difference is calculated by multiplying the torsion influence coefficient by the torsion influence coefficient, which is the crank angular velocity difference during the combustion stroke of each cylinder of engine 200. The determination difference is obtained by correcting the crank angular velocity difference using the torsion influence coefficient.

[0065] Then, determination unit 702 determines whether or not the determination difference is greater than a threshold value (S700). If the determination difference is greater than the threshold value (YES in S700), determination unit 702 determines that engine 200 is in a misfire state, and if the determination difference is equal to or less than the threshold value (NO in S700), determination unit 702 determines that engine 200 is in a normal state, and ends the misfire determination process.

[0066] As described above, according to this embodiment, the hysteresis torque of DMF 400 is calculated based on the grease temperature of the grease sealed in DMF 400, and the crank angular velocity is calculated based on the hysteresis torque that changes with the grease temperature. Therefore, for example, when determining whether or not a misfire has occurred in engine 200 equipped with DMF 400, the influence of the grease temperature inside DMF 400 can be taken into account, and the misfire determination for engine 200 can be performed with high accuracy.

[0067] Furthermore, by calculating a torsion influence coefficient based on the hysteresis torque that changes depending on the grease temperature and correcting the crank angular velocity using the torsion influence coefficient, it is possible to remove the influence of resonance of the DMF 400 from the crank angular velocity. Furthermore, by estimating the grease temperature based on the engine oil temperature and the transmission oil temperature, it is possible to accurately estimate the grease temperature in the DMF 400.

[0068] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0069] 100 Engine System 200 Engine 302 Crank angle sensor 400 Dual Mass Flywheel (DMF) 600 Transmission 701 Arithmetic unit 702 Judgment section

Claims

1. an engine having a crankshaft; a crank angle sensor that detects a rotation angle of the crankshaft; a dual mass flywheel connected to the crankshaft; a calculation unit that calculates a hysteresis torque of the dual mass flywheel based on a grease temperature, which is the temperature of the grease sealed in the dual mass flywheel, and calculates a crank angular velocity based on the hysteresis torque that varies depending on the rotational angle of the crankshaft and the grease temperature; An engine system comprising:

2. The calculation unit a hysteresis torque of the dual mass flywheel is calculated based on a grease temperature, which is the temperature of the grease sealed in the dual mass flywheel; a coefficient reflecting an influence on the crank angular velocity according to a torsion angle of the dual mass flywheel is calculated based on the hysteresis torque that varies depending on the grease temperature; and the crank angular velocity is corrected using the rotation angle of the crankshaft and the coefficient. The engine system of claim 1 .

3. a transmission connected to the dual mass flywheel; the calculation unit estimates the grease temperature based on an oil temperature of the engine and an oil temperature of the transmission; 3. The engine system according to claim 1 or 2.

4. The calculation unit calculating a torsion angle of the dual mass flywheel based on the engine speed and the hysteresis torque; calculating a coefficient that reflects an effect on the crank angular velocity according to the torsion angle of the dual mass flywheel, based on the rotation speed of the engine and the torsion angle; The engine system according to any one of claims 1 to 3.

5. a determination unit that determines whether the engine has misfired based on the crank angular velocity in a combustion stroke of each cylinder of the engine, The engine system according to any one of claims 1 to 4.

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