JP7779281B2 - Combustion torque calculation device - Google Patents

Description

This invention relates to a combustion torque calculation device.

The vehicle disclosed in Patent Document 1 has an internal combustion engine. The crankshaft of the internal combustion engine is connected to downstream components in the drivetrain via a damper. In this configuration, when the torque of the crankshaft fluctuates, torsional vibration occurs in the damper. As a result, torque caused by the torsional vibration is input to the downstream components. At this time, a reaction force from the damper is input to the crankshaft. This reaction force also includes a resonance component of the downstream components induced by the torsional vibration.

The control device of the vehicle determines whether the internal combustion engine has misfired based on the progression of the engine's rotational fluctuations. In doing so, the control device takes into account the influence of the reaction force contained in the engine's rotational fluctuations. Specifically, the control device calculates the reaction force component contained in the engine's rotational fluctuations based on the product of the damper's torsion angle and the damper's spring constant. The control device then determines whether the internal combustion engine has misfired after eliminating the influence of this reaction force component.

Japanese Patent Application Laid-Open No. 2008-248877

As in Patent Document 1, a specified value determined from the specifications of the damper is sometimes set as the damper spring constant used to calculate the reaction force component. However, the actual spring constant of a damper installed in a vehicle varies within the damper's tolerance range. Furthermore, over time, the damper's characteristics gradually change, causing the spring constant to change. For these reasons, when using the method in Patent Document 1, variation can occur in the reaction force component calculated from the damper's spring constant. As a result, there is a risk that the combustion torque, which is the internal combustion engine's true torque associated with the combustion of the air-fuel mixture, cannot be accurately calculated.

The combustion torque calculation device for solving the above problem is intended for a vehicle having a multi-cylinder internal combustion engine with a crankshaft, a rotating body located on a torque transmission path from the crankshaft to the drive wheels, a damper connected to the crankshaft on the torque transmission path and absorbing torque fluctuations of the crankshaft, a torque tube located between the damper and the rotating body and having a smaller spring constant than the damper, a first sensor that detects the angular position of the crankshaft, a second sensor that detects the angular position of the connection point of the torque tube relative to the damper, and a third sensor that detects the angular position of the rotating body. When the amount of change in angular position per unit time is the rotational speed, the system executes the following steps: a first process calculates the inertia torque of the crankshaft based on the value obtained by time-differentiating the rotational speed of the crankshaft; a second process calculates the product of the difference between the angular position of the connecting portion and the angular position of the rotating body and the spring constant of the torque tube; a third process calculates the reaction torque, which is the torque acting on the crankshaft from the damper, based on the product and the value obtained by time-differentiating the rotational speed of the connecting portion; and a fourth process calculates the combustion torque, which is the torque of the crankshaft excluding the influence of the reaction torque, based on the reaction torque and the inertia torque of the crankshaft.

In the above configuration, the spring constant of the torque tube is smaller than the spring constant of the damper. Therefore, even if there is a similar percentage variation in the spring constants of the torque tube and the damper, the variation in the spring constant in absolute value may be smaller for the torque tube than for the damper. Therefore, in the above configuration, which calculates the combustion torque using the spring constant of the torque tube, the reaction torque, and therefore the combustion torque, can be calculated more accurately.

FIG. 1 is a schematic configuration diagram of a vehicle. FIG. 10 is a block diagram showing the processing content of a first calculation process. FIG. 10 is a block diagram showing the processing content of a second calculation process. FIG. 10 is a block diagram showing the processing content of a third calculation process. 10A and 10B are diagrams illustrating engine rotation speed ranges in which each calculation process is used. FIG. 4 is a diagram showing an example of a transition of combustion torque.

<Overall vehicle configuration>
An embodiment of a combustion torque calculation device will be described below with reference to the drawings. As shown in FIG. 1 , a vehicle 10 has an internal combustion engine 20. The internal combustion engine 20 is a drive source for the vehicle 10. The internal combustion engine 20 is located in an engine compartment defined in a forward portion of the vehicle 10. The internal combustion engine 20 is a multi-cylinder internal combustion engine having four cylinders 22. A mixture of fuel injected from a fuel injection valve 25 for each cylinder 22 and intake air is introduced into each cylinder 22. The mixture is then ignited in each cylinder 22 by a spark plug 26 for each cylinder 22, causing combustion. Although not shown, each cylinder 22 houses a piston. The piston reciprocates within the cylinder 22 in response to combustion of the mixture. A crankshaft 21, which is the output shaft of the internal combustion engine 20, rotates in response to the movement of the piston. The internal combustion engine 20 is a four-stroke engine with one cycle. That is, one cycle of the internal combustion engine 20 corresponds to a period in which the crankshaft 21 rotates 720 degrees. In this one cycle, each cylinder 22 goes through an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke.

The vehicle 10 has a torsional damper (hereinafter simply referred to as the damper) 60. The damper 60 is connected to the crankshaft 21. The damper 60 absorbs torque fluctuations of the crankshaft 21.

The vehicle 10 has a torque tube 30 and a connecting part 35. The torque tube 30 is a highly rigid cylindrical part made of materials such as metal or carbon. The spring constant Kt of the torque tube 30 is smaller than the spring constant Kd of the damper 60. In other words, the torque tube 30 is softer than the damper 60. The torque tube 30 extends from the front to the rear of the vehicle 10. With respect to the front and rear of the vehicle 10, the torque tube 30 extends, for example, from near the front wheels to near the rear wheels. The front end of the torque tube 30 is connected to the damper 60 via the connecting part 35. The front end of the torque tube 30 rotates integrally with the connecting part 35.

The vehicle 10 has a motor generator 40. The motor generator 40 is the driving source of the vehicle 10. The motor rotating shaft 41, which is the output shaft of the motor generator 40, rotates integrally with the rotor 42. The rotor 42 is rotatable relative to the stator 43. The motor rotating shaft 41 is connected to the rear end of the torque tube 30. The motor rotating shaft 41 rotates integrally with the rear end of the torque tube 30. The motor rotating shaft 41 constitutes a rotating body.

The vehicle 10 has a torque converter 80 and an automatic transmission 50. The torque converter 80 and automatic transmission 50 are located near the rear of the vehicle 10, along with the motor generator 40. The torque converter 80 is equipped with a lock-up clutch 81. The input shaft 51 of the automatic transmission 50 is connected to the motor rotating shaft 41 via the torque converter 80. The lock-up clutch 81 basically always directly connects the motor rotating shaft 41 and the input shaft 51 of the automatic transmission 50 while the internal combustion engine 20 is operating.

The automatic transmission 50 is a stepped transmission that can change the gear ratio in multiple stages by changing gears. That is, the automatic transmission 50 has multiple shiftable gears. Each gear has a different gear ratio. The higher the gear, the smaller the gear ratio. The automatic transmission 50 shifts the rotation of the input shaft 51 according to the currently selected gear and outputs it from the output shaft 52. The gear ratio is a ratio that indicates the number of times the input shaft 51 rotates for each rotation of the output shaft 52. Therefore, the higher the gear ratio, the faster the input shaft 51 rotates relative to the output shaft 52.

The vehicle 10 has a drive shaft 70. The spring constant Ks of the drive shaft 70 is smaller than the spring constant Kt of the torque tube 30. The drive shaft 70 is connected to the output shaft 52 of the automatic transmission 50 via a differential or the like. The drive shaft 70 is also connected to the rear wheels, which are drive wheels 72.

As described above, the torque transmission path from the internal combustion engine 20 to the drive wheels 72 includes the damper 60, torque tube 30, motor rotating shaft 41, automatic transmission 50, and drive shaft 70, arranged in this order. Of these, the damper 60, torque tube 30, and drive shaft 70 constitute torsional elements that cause twisting on the path.

Various sensors are attached to the vehicle 10. For example, the vehicle 10 is equipped with an accelerator sensor 94 that detects the accelerator pedal depression amount ACC and a vehicle speed sensor 95 that detects the vehicle's traveling speed SP. The vehicle 10 is also equipped with a first sensor 91, a second sensor 92, and a third sensor 93. The first sensor 91 detects the angular position Vcr of the crankshaft 21. The second sensor 92 detects the angular position Vn of the connecting part 35. The third sensor 93 detects the angular position Vmg of the motor rotary shaft 41. Each of the above sensors detects the angular position of each component within a range from zero degrees to 360 degrees, with the same reference position being zero degrees. The reference position is, for example, the 12 o'clock position on an imaginary circle centered on the central axis of the component being detected when each sensor is attached to the vehicle 10. For example, if the central axis of each component is horizontal, the reference position defined above would be directly above the central axis of each component. The angular position Vn of the connecting part 35 coincides with the angular position of the front end of the torque tube 30, i.e., the angular position of the connecting portion of the torque tube 30 relative to the damper 60. In other words, the second sensor 92 essentially detects the angular position of the connecting portion of the torque tube 30 relative to the damper 60. The second sensor 92 may also detect the angular position of the front end of the torque tube 30.

<General configuration of the control device>
The vehicle 10 has a control device 1. The control device 1 includes a CPU 2, which is a central processing unit, and a memory 3 that stores control programs and data. The control device 1 realizes various processes by having the CPU 2 execute the programs stored in the memory 3.

The control device 1 repeatedly receives detection signals from the various sensors described above. For example, the control device 1 repeatedly receives the angular position Vcr of the crankshaft 21 detected by the first sensor 91. The control device 1 repeatedly calculates the rotational speed ωe of the crankshaft 21 at specified angles based on the progression of the angular position Vcr of the crankshaft 21. The rotational speed ωe of the crankshaft 21 is the amount of change in the angular position Vcr of the crankshaft 21 per unit time. The specified angle is an angle smaller than the interval between occurrences of top dead center of compression stroke, such as 30 degrees. For example, the control device 1 may measure the time required for the crankshaft 21 to rotate a specified angle and calculate the rotational speed ωe based on the reciprocal of that time. The control device 1 repeatedly calculates the engine rotational speed Ne based on the rotational speed ωe of the crankshaft 21. The engine rotational speed Ne is the average value of the rotational speed ωe of the crankshaft 21 over one or more rotations of the crankshaft 21. For example, the control device 1 calculates the engine rotation speed Ne for each specified cycle of the internal combustion engine 20. An example of the specified cycle is two cycles. Similar to the rotation speed ωe of the crankshaft 21, the control device 1 calculates the rotation speed ωn of the connecting part 35 based on the change in the angular position Vn of the connecting part 35 detected by the second sensor 92. The rotation speed ωn of the connecting part 35 is the amount of change in the angular position Vn of the connecting part 35 per unit time. The control device 1 repeatedly calculates the rotation speed ωn of the connecting part 35 at the same timing as calculating the rotation speed ωe of the crankshaft 21.

The control device 1 controls various parts of the vehicle 10. For example, the control device 1 controls the internal combustion engine 20. The control device 1 operates the fuel injection valves 25 and spark plugs 26 to sequentially combust the air-fuel mixture in each cylinder 22. The control device 1 also controls the automatic transmission 50. The control device 1 switches the gear position of the automatic transmission 50 based on the vehicle 10's traveling speed SP and the accelerator pedal operation amount ACC.

The control device 1 also functions as a calculation device for the combustion torque TY of the crankshaft 21. Here, while the internal combustion engine 20 is operating, the torque of the crankshaft 21 is input to the damper 60. At this time, if the torque of the crankshaft 21 fluctuates, torsional vibration occurs in the damper 60, and the torque caused by this torsional vibration can be input to the torque tube 30 and further to various components on the drive wheel 72 side. At that time, a reaction force from the damper 60 acts on the crankshaft 21. The combustion torque TY is the torque of the crankshaft 21 that theoretically eliminates the influence of this reaction force from the damper 60. In other words, the combustion torque TY is the original torque of the crankshaft 21 that occurs when the air-fuel mixture is burned.

The control device 1 can execute three processes to calculate the combustion torque TY: a first calculation process, a second calculation process, and a third calculation process. The content of each of these processes will be described in detail below. While a detailed explanation will be omitted, when executing each process, the control device 1 references the trends in each rotational speed, which it calculates at any time, and the latest angular positions received from the various sensors 91, 92, and 93.

<First Calculation Process>
2, in each execution of the first calculation process, the control device 1 performs four processes, namely, a first process M1, a second process M2, a third process M3, and a fourth process M4, once each, and calculates one combustion torque TY through these four processes.

In the first process M1, the control device 1 calculates the inertia torque TIe of the crankshaft 21. As shown in the following (Equation 1), the control device 1 calculates the inertia torque TIe of the crankshaft 21 by multiplying the pre-stored moment of inertia Ie of the crankshaft 21 by the time-differentiated value of the rotational speed ωe of the crankshaft 21. The moment of inertia Ie of the crankshaft 21 is a value corresponding to the mass of the crankshaft 21, etc.
(Equation 1) T Ie = Ie · (dωe / dt)
In second process M2, the control device 1 calculates the torsional torque TWt, which is the torque caused by the torsion of the torque tube 30. As shown in the following (Equation 2), the control device 1 calculates the torsional torque TWt by multiplying the spring constant Kt of the torque tube 30, which is stored in advance, by the torsional angle of the torque tube 30. The torsional angle of the torque tube 30 is the value obtained by subtracting the angular position Vmg of the motor rotary shaft 41 from the angular position Vn of the connecting part 35.
(Formula 2) TWt=Kt・(Vn-Vmg)
In the third process M3, the control device 1 calculates the specific torque TX. Specifically, the control device 1 calculates the specific torque TX as the sum of the inertia torque of the connecting part 35 and the torsional torque TWt of the torque tube 30 calculated in the second process M2, as shown in the following (Equation 3). The inertia torque of the connecting part 35 is the product of the time-differentiated value of the rotational speed ωn of the connecting part 35 and the moment of inertia In of the connecting part 35. The moment of inertia In of the connecting part 35 is a value corresponding to the mass of the connecting part 35. The control device 1 stores the moment of inertia In of the connecting part 35 in advance.
(Formula 3) TX=In・(dωn/dt)+TWt
The specific torque TX represents the reaction torque acting on the crankshaft 21 from the damper 60 .

In the fourth process M4, the control device 1 calculates the combustion torque TY. Specifically, the control device 1 calculates the combustion torque TY as the sum of the inertia torque TIe of the crankshaft 21 calculated in the first process M1 and the specific torque TX calculated in the fourth process M4, as shown in the following (Equation 4).
(Formula 4) TY=TIe+TX
Here, the inertia torque TIe of the crankshaft 21 is a value that includes the influence of the reaction torque. By adding the specific torque TX to the inertia torque TIe of the crankshaft 21 in consideration of the direction of the force, it is theoretically possible to obtain the torque of the crankshaft 21 from which the influence of the reaction torque acting on the crankshaft 21 from the damper 60 is eliminated.

<Second Calculation Process>
In the second calculation process, the control device 1 performs a fifth process M5 and a sixth process M6 instead of the second process M2, the third process M3, and the fourth process M4 performed in the first calculation process. That is, as shown in Fig. 3, in one execution of the second calculation process, the control device 1 performs each of the three processes, the first process M1, the fifth process M5, and the sixth process M6, once. The control device 1 calculates one combustion torque TY through these three processes.

In the first process M1, the control device 1 calculates the inertia torque TIe of the crankshaft 21 in the same manner as described in the first calculation process.
In fifth process M5, the control device 1 calculates torsional torque TWd, which is torque caused by torsion of the damper 60. As shown in (Equation 5), the control device 1 calculates the torsional torque TWd as the product of the spring constant Kd of the damper 60, which is stored in advance, and the torsional angle of the damper 60. The torsional angle of the damper 60 is a value obtained by subtracting the angular position Vn of the connecting part 35 from the angular position Vcr of the crankshaft 21.
(Formula 5) TWd=Kd・(Vcr−Vn)
The above-mentioned torsional torque TWd represents the reaction torque acting on the crankshaft 21 from the damper 60 .

In the sixth process M6, the control device 1 calculates the combustion torque TY. Specifically, the control device 1 calculates the combustion torque TY as the sum of the inertia torque TIe of the crankshaft 21 calculated in the first process M1 and the torsional torque TWd calculated in the fifth process M5, as shown in the following (Equation 6).
(Formula 6) TY=TIe+TWd
<Third Calculation Process>
In the third calculation process, the control device 1 performs a seventh process M7 instead of the second process M2, the third process M3, and the fourth process M4 performed in the first calculation process. That is, as shown in FIG. 4 , in the third calculation process, the control device 1 performs the first process M1 and the seventh process M7. Unlike the first calculation process and the second calculation process, the control device 1 performs the first process M1 multiple times in one execution of the third calculation process. The control device 1 repeats the first process M1 for a predetermined fixed period, for example, every specified angle. Then, after the fixed period has elapsed, i.e., after multiple executions of the first process M1, the control device 1 performs the seventh process M7 once. The fixed period is a period of one or more cycles of the internal combustion engine 20, for example, the specified cycle of the internal combustion engine 20.

In the first process M1, the control device 1 calculates the inertia torque TIe of the crankshaft 21 in the same manner as described in the first calculation process.
In the seventh process M7, the control device 1 performs filtering using a band-stop filter on the time series of the inertia torque TIe of the crankshaft 21 calculated multiple times in the first process M1. This filtering reduces the intensity of the cycle first frequency component of the internal combustion engine 20 from the time series of the inertia torque TIe of the crankshaft 21. The cycle first frequency component of the internal combustion engine 20 is a fluctuation component with one period corresponding to one cycle of the internal combustion engine 20, and is a 0.5-order frequency component when converted to a frequency component with one period corresponding to one rotation of the crankshaft 21. By performing this filtering on the time series of the inertia torque TIe of the crankshaft 21, the control device 1 calculates a time series of the combustion torque TY in which the influence of the reaction torque is eliminated from the inertia torque TIe of the crankshaft 21.

<Switching calculation process>
As shown in FIG. 5 , the control device 1 switches the calculation process used to calculate the combustion torque TY depending on the range of the engine rotation speed Ne. For this switching, the control device 1 pre-stores a first range R1, which is the range of the engine rotation speed Ne for which the first calculation process is used, a second range R2, which is the range for which the second calculation process is used, and a third range R3, which is the range for which the third calculation process is used. In this embodiment, these three ranges are separate ranges that do not overlap with each other. Furthermore, these three ranges of the engine rotation speed Ne are determined taking into account the resonance frequencies of the three torsion elements. Note that the resonance frequencies of the three torsion elements are different from each other.

The first range R1 is predetermined as the range of engine speeds Ne within which fluctuations occur in the frequency band surrounding the resonant frequency of the torque tube 30. The second range R2 is predetermined as the range of engine speeds Ne within which fluctuations occur in the frequency band surrounding the resonant frequency of the damper 60. The third range R3 is predetermined as the range of engine speeds Ne within which fluctuations occur in the frequency band surrounding the resonant frequency of the drive shaft 70. Note that the resonant frequencies of each torsion element are determined assuming that the lock-up clutch 81 is in a directly coupled state.

Here, the larger the spring constant of a torsion element, the higher the engine rotation speed Ne at which that torsion element resonates. That is, the engine rotation speed Ne at which these elements resonate increases in the order of drive shaft 70, torque tube 30, and damper 60. Taking this into consideration, as shown in Figure 5, the engine rotation speed Ne increases in the third range R3, first range R1, and second range R2. Specifically, the third range R3, which takes into account the resonance frequency of the drive shaft 70, is the range where the engine rotation speed Ne is greater than 0 and equal to or less than a first threshold value. The first range R1, which takes into account the resonance frequency of the torque tube 30, is the range where the engine rotation speed Ne is greater than the first threshold value and equal to or less than a second threshold value. The second range R2, which takes into account the resonance frequency of the damper 60, is the range where the engine rotation speed Ne is greater than the second threshold value and equal to or less than an upper threshold value. Note that the second threshold value is a specific value.

The resonance frequency of each torsional element varies depending on the gear position of the automatic transmission 50. The engine rotation speed Ne at which a particular torsional element resonates increases as the gear position increases. Therefore, as shown in FIG. 5, the control device 1 variably sets the first range R1, second range R2, and third range R3 depending on the gear position selected in the automatic transmission 50. In this embodiment, the control device 1 changes each range in two stages based on a predetermined specific gear position A. The specific gear position A is, for example, the middle value among the multiple gear positions in the automatic transmission 50. Hereinafter, among the multiple gear positions, gear positions equal to or higher than the specific gear position A are referred to as high gear positions, and gear positions below the specific gear position A are referred to as low gear positions. When the automatic transmission 50 is in a high gear position, the control device 1 sets the first threshold to a larger value than when the automatic transmission 50 is in a low gear position. Furthermore, the control device 1 sets the second threshold to a larger value for a high gear than for a low gear. Furthermore, the control device 1 sets the upper limit threshold to a larger value for a high gear than for a low gear. As a result, the third range R3 expands and the first range R1 and the second range R2 shift toward a higher engine speed Ne for a high gear compared to a low gear. Note that, for both a high gear and a low gear, the first threshold set by the control device 1 is determined in advance through experiments or the like as a value that distinguishes between the range of engine speed Ne at which the drive shaft 70 resonates and the range of engine speed Ne at which the torque tube 30 resonates. Similarly, for both a high gear and a low gear, the second threshold is determined in advance through experiments or the like as a value that distinguishes between the range of engine speed Ne at which the torque tube 30 resonates and the range of engine speed Ne at which the damper 60 resonates. Furthermore, for both the high and low gear stages, the upper threshold value is determined in advance through experiments, etc. as the maximum value of the engine rotation speed Ne at which it is assumed that no resonance of the damper 60 occurs.

When the current engine speed Ne is a value within the first range R1 corresponding to the currently selected gear, the control device 1 repeats the first calculation process, for example, at every specified angle. When the current engine speed Ne is a value within the second range R2 corresponding to the currently selected gear, the control device 1 repeats the second calculation process, for example, at every specified angle. When the current engine speed Ne is a value within the third range R3 corresponding to the currently selected gear, the control device 1 repeats the third calculation process, for example, at every specified cycle of the internal combustion engine 20. By repeating each calculation process, the combustion torque TY is calculated over time.

<Missfire judgment>
The control device 1 determines whether or not a misfire has occurred in the internal combustion engine 20 based on the change in the combustion torque TY calculated over time as described above during operation of the internal combustion engine 20. Here, as shown in the first period H1 of FIG. 6 , when the combustion of the air-fuel mixture in each cylinder 22 is stable, the combustion torque TY repeatedly increases and decreases in accordance with the combustion of the air-fuel mixture in each cylinder 22. That is, the combustion torque TY increases once as the air-fuel mixture in one cylinder 22 burns, and then decreases when the combustion of the air-fuel mixture ends. The combustion torque TY repeats this cycle of increase and decrease. On the other hand, when a misfire occurs in a certain cylinder 22, the combustion torque TY exhibits a sudden drop, as shown in the second period H2 of FIG. 6 . The control device 1 pre-stores, as a determination value TY1, the maximum value of the combustion torque TY at which a drop in the combustion torque TY due to a misfire is deemed to have occurred. The control device 1 determines whether or not a misfire has occurred in the internal combustion engine 20 based on this determination value TY1. That is, the control device 1 determines that a misfire has occurred when the combustion torque TY is equal to or less than the determination value TY1, and determines that a misfire has not occurred otherwise.

<Effects of the embodiment>
(1) As a premise, when a certain torsional element resonates, the torsional torque of that torsional element in turn becomes the above-mentioned reaction torque. Therefore, in order to accurately calculate the reaction torque, it is preferable to consider the torsional torque of the torsional element that causes resonance, i.e., the torsional angle of the target torsional element. Here, the component that is the main source of resonance, and therefore the reaction torque, differs depending on the engine rotation speed Ne. Based on this and the above premise, in order to accurately calculate the combustion torque TY within a certain range of engine rotation speed Ne, it is preferable to calculate the reaction torque taking into account the torsional angle of the component that resonates within that range.

Therefore, in this embodiment, the method for calculating reaction torque, and therefore combustion torque TY, is changed depending on the engine rotation speed Ne. In the first range R1, where the torque tube 30 resonates, combustion torque TY is calculated based on the torsional angle of the torque tube 30. In the second range R2, where the damper 60 resonates, combustion torque TY is calculated based on the torsional angle of the damper 60. The vehicle 10 of this embodiment does not have a device for detecting the torsional angle of the drive shaft 70. Calculating the reaction torque associated with resonance of the drive shaft 70 based on the torsional angle of the torque tube 30 or damper 60 could result in a decrease in calculation accuracy. Therefore, in this embodiment, filtering is used to eliminate the influence of reaction torque in the third range R3, where resonance of the drive shaft 70 occurs. While filtering does not provide the same level of accuracy as calculating combustion torque TY using the torsional angle of the drive shaft 70, it can still ensure a reasonable level of accuracy.

In this way, by using a method appropriate for each range of engine speed Ne from the perspective of eliminating the influence of reaction torque, it is possible to accurately calculate combustion torque TY for each range of engine speed Ne. Then, by determining the presence or absence of misfire based on this combustion torque TY, the determination can be made more accurately.

(2) Furthermore, this embodiment takes into consideration the fact that the range of engine rotation speed Ne at which each torsional element resonates changes depending on the gear position of the automatic transmission 50. The first range R1, second range R2, and third range R3 are variably set depending on the gear position selected in the automatic transmission 50. This allows the combustion torque TY to be calculated using the optimal method depending on the gear position selected in the automatic transmission 50.

<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be implemented in combination with each other within the scope of technical compatibility.

The manner of misfire determination is not limited to the example of the above embodiment. As long as misfire determination can be performed appropriately, any manner of misfire determination can be used.
The combustion torque TY may be used for purposes other than misfire detection. For example, the combustion torque TY may be used to diagnose variations in the air-fuel ratio among the four cylinders 22.

- The method for determining the range of engine rotation speed Ne according to the gear position is not limited to the example in the above embodiment. For example, a first range R1, a second range R2, and a third range R3 may be defined for each of multiple gear positions. The first threshold value and the second threshold value may be set to be larger as the gear position increases. When the gear ratio selected by the automatic transmission 50 is a certain first value, the second threshold value, which is a specific value, may be set to a larger value than when the gear ratio is a second value greater than the first value.

It is not essential that the first range R1, the second range R2, and the third range R3 be set variably depending on the gear position. That is, the same ranges may be set for all gear positions.
The engine operating state for which each calculation process is used may be defined by a parameter other than the engine speed Ne. Such a parameter may be the engine load factor, which indicates the amount of intake air filling the cylinder 22. For example, the first calculation process may be used only when the engine load factor is within a specific range of the first range R1.

- The method for determining the range of engine speed Ne using each calculation process is not limited to the example in the above embodiment. The three ranges R1, R2, and R3 do not necessarily have to be completely separate ranges. For example, the first range R1 and the second range R2 may partially overlap. In the overlapping range, the average value of the combustion torque TY obtained from both the first calculation process and the second calculation process may be used as the final combustion torque, or the combustion torque TY obtained from either one of the processes may be used as the final combustion torque. The first range R1 and the second range R2 may also be determined regardless of the resonant frequency. It is sufficient that the first range R1 exists, which is the range in which the combustion torque TY is calculated using the first process M1.

When calculating the combustion torque TY, the inertia torque TIe or the torsional torque of the crankshaft 21 may be multiplied by a correction coefficient.
The third range R3 may be omitted. In other words, the use of the third calculation process is not essential. Furthermore, the second range R2 may be omitted. The use of the second calculation process is also not essential.

The number of cylinders 22 may be changed. It is sufficient that a plurality of cylinders 22 is provided.
The internal combustion engine 20 may have two strokes as one cycle.
The overall configuration of the vehicle 10 is not limited to the example of the above embodiment. The motor generator 40 may be eliminated from the vehicle 10. The input shaft 51 of the automatic transmission 50 may constitute the rotating body. The automatic transmission 50 may be a continuously variable transmission. The automatic transmission 50 may be eliminated.

1...Control device 10...Vehicle 20...Internal combustion engine 21...Crankshaft 41...Motor rotating shaft 60...Damper 30...Torque tube 91...First sensor 92...Second sensor 93...Third sensor

Claims (5)

The present invention is directed to a vehicle having a multi-cylinder internal combustion engine with a crankshaft, a rotating body located on a torque transmission path from the crankshaft to drive wheels, a damper connected to the crankshaft on the torque transmission path and absorbing torque fluctuations of the crankshaft, a torque tube located between the damper and the rotating body and having a spring constant smaller than that of the damper, a first sensor that detects the angular position of the crankshaft, a second sensor that detects the angular position of a connection portion of the torque tube with respect to the damper, and a third sensor that detects the angular position of the rotating body,
When the amount of change in angular position per unit time is the rotation speed,
a first process of calculating an inertia torque of the crankshaft based on a value obtained by time-differentiating a rotation speed of the crankshaft;
a second process of calculating the product of a difference between an angular position of the coupling portion and an angular position of the rotor and a spring constant of the torque tube;
a third process of calculating a reaction torque acting on the crankshaft from the damper based on the product and a value obtained by differentiating the rotational speed of the connecting portion with respect to time;
and a fourth process of calculating a combustion torque, which is the torque of the crankshaft excluding the influence of the reaction torque, based on the reaction torque and the inertia torque of the crankshaft. When the average value of the rotation speed of the crankshaft while the crankshaft rotates one or more times is defined as the engine rotation speed,
when the engine rotation speed is within a predetermined first range that includes a resonance frequency band of the torque tube, calculating the combustion torque by executing the first process, the second process, the third process, and the fourth process;
2. The combustion torque calculation device according to claim 1, wherein, when the engine rotation speed is within a second range that is predetermined as a range that includes a resonance frequency band of the damper, the following are executed instead of the second process, the third process, and the fourth process: a fifth process for calculating the reaction torque based on a product of a difference between an angular position of the crankshaft and an angular position of the connecting portion and a spring constant of the damper; and a sixth process for calculating the combustion torque based on the reaction torque calculated in the fifth process and an inertia torque of the crankshaft calculated in the first process. 3. The combustion torque calculation device according to claim 2, wherein, when the range of the engine rotation speed is a third range that is predetermined as a range different from the first range and the second range, instead of the second process, the third process, and the fourth process, a seventh process is executed to calculate the time series of the combustion torque by performing filtering on the time series of the inertia torque of the crankshaft calculated in the first process to reduce intensity of a cycle primary frequency component of the multi-cylinder internal combustion engine. the vehicle has an automatic transmission located between the torque tube and the drive wheels;
the first range is a range in which the engine rotation speed is equal to or less than a predetermined specific value,
the second range is a range in which the engine rotation speed is greater than the specific value,
3. The combustion torque calculation device according to claim 2, wherein when the gear ratio selected in the automatic transmission is a first value, the specific value is set to a larger value than when the gear ratio is a second value larger than the first value. The combustion torque calculation device according to claim 1 , further comprising: determining whether or not a misfire has occurred in the multi-cylinder internal combustion engine based on the combustion torque.