Engine misfire detection device

Abstract

To improve determination accuracy of a misfire state with a simple structure in a misfire detection device for an engine.SOLUTION: A misfire detection device 10 for an engine 1 includes a calculation section 11 and a determination section 12. The calculation section 11 calculates a first deviation ΔNeA representing the change tendency of a crank angle speed Ne in a former half of a combustion stroke of the engine 1 and a second deviation ΔNeB representing the change tendency of the crank angle speed Ne in a latter half of the combustion stroke. The determination section 12 determines the possibility of a misfire of the engine 1 on the basis of the first deviation ΔNeA, and determines whether the misfire of the engine 1 is an actual misfire or a half misfire on the basis of the second deviation ΔNeB.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a misfire detection device for determining the misfire state of an engine. [Background technology]

[0002] Conventionally, there are techniques for determining misfire conditions such as misfire and semi-misfire based on changes in the engine crank angular velocity (engine rotation speed). For example, a technique is known in which the amount of fluctuation between the crank angular velocity before combustion and the crank angular velocity after combustion in the combustion cycle of each cylinder of the engine is calculated, and the amount of fluctuation is compared with a predetermined misfire determination value to determine whether or not a misfire has occurred (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4490721 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology described above, when the crank angular velocity suddenly changes, the amount of fluctuation between the crank angular velocity before combustion and the crank angular velocity after combustion increases. This can lead to a false determination that a misfire has occurred even when a misfire has not actually occurred, resulting in a problem of being unable to accurately identify poor combustion. Therefore, conventional misfire determinations have had to be performed in operating conditions where the engine rotation speed fluctuates little (relatively stable operating conditions).

[0005] One of the objects of the present invention, which was devised in light of the above-mentioned problems, is to provide an engine misfire detection device that can improve the accuracy of determining poor combustion with a simple configuration. However, in addition to this object, another object of the present invention is to achieve effects derived from the respective configurations shown in the "Description of Embodiments" below, which are effects that cannot be obtained with conventional techniques. [Means for solving the problem]

[0006] The disclosed engine misfire detection device can be realized as the following disclosed aspects or application examples, and solves at least some of the above problems. The disclosed engine misfire detection device includes a calculation unit that calculates a first deviation that represents the change trend of the crank angular velocity in the first half of the engine's combustion stroke and a second deviation that represents the change trend of the crank angular velocity in the second half of the combustion stroke, and a judgment unit that determines the possibility of misfire in the engine based on the first deviation and determines whether the engine misfire is a real misfire or a semi-misfire based on the second deviation. [Effects of the Invention]

[0007] According to the disclosed engine misfire detection device, the possibility of engine misfire is determined based on the first deviation, and whether the engine misfire is a real misfire or a semi-misfire is determined based on the second deviation, thereby improving the accuracy of determining poor combustion with a simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a block diagram illustrating the configuration of an engine and a misfire detection device. [Figure 2] 10 is a graph illustrating a first deviation ΔNeA and a second deviation ΔNeB calculated by the misfire detection device, showing a change in crank angular velocity Ne with respect to a crank angle θ. [Figure 3] 10A is a diagram showing the relationship between the first deviation ΔNeA and the possibility of misfire, and FIG. 10B is a diagram showing the relationship between the second deviation ΔNeB and the type of misfire. [Figure 4] 10 is a graph for explaining a determination taking into consideration the degree of deceleration. [Figure 5] FIG. 4 is a diagram showing an example of a misfire map. DETAILED DESCRIPTION OF THE INVENTION

[0009] The disclosed engine misfire detection device can be applied to various engines, such as automobile engines, marine engines, industrial engines, and general-purpose engines. In the following embodiment, a misfire detection device applied to an engine mounted on a vehicle is exemplified. Furthermore, types of engines to which the misfire detection device can be applied include gasoline engines and diesel engines, and there are no restrictions on the number of cylinders or the cylinder arrangement. [Example]

[0010] [1. Configuration] A misfire detection device 10 according to the embodiment is applied to an on-vehicle engine 1 shown in FIG. 1. The engine 1 is a four-cylinder, four-stroke gasoline engine. FIG. 1 shows one of the four cylinders provided in the engine 1. A crank angle sensor 2 for detecting a crank angle θ is provided near the crankshaft. The crank angle sensor 2 calculates the crank angular velocity (the amount of change in the crank angle θ per unit time) based on the time it takes for the crankshaft to rotate a predetermined angle (e.g., 10°). The crank angular velocity corresponds to the engine rotation speed Ne [rpm] (the number of engine revolutions per unit time (one minute)). Therefore, in this embodiment, the crank angular velocity is denoted by the symbol Ne. In this embodiment, the crank angular velocity is calculated for every 10° of crank angle.

[0011] An accelerator pedal position sensor 3 that detects the amount of depression of the accelerator pedal (accelerator pedal position) and a vehicle speed sensor 4 that detects a parameter corresponding to the vehicle speed (vehicle running speed) are provided at any position on the vehicle on which the engine 1 is mounted. The accelerator pedal position is a parameter that corresponds to the driver's request for acceleration / deceleration, intention to start, intention to brake, etc. The vehicle speed sensor 4 detects, for example, wheel speed, angular velocity of the wheel axle, or engine rotation speed. The vehicle speed is calculated based on these values.

[0012] This vehicle is provided with a misfire detection device 10, which is an electronic control unit (ECU). The misfire detection device 10 incorporates a processor (central processing unit), memory (main memory), storage device, interface device, etc., all of which are not shown. The contents of the control executed by the misfire detection device 10 are recorded and saved in the memory or storage device as firmware or an application program. When the program is executed, the contents of the program are expanded and arithmetic processing is performed by the processor.

[0013] The misfire detection device 10 has the function of determining whether the engine 1 is in a misfire state. The misfire detection device 10 first determines whether the combustion state in the cylinder is normal or whether it is in an abnormal state of poor combustion (misfire state). In the latter case, the device distinguishes between "full misfire" and "semi-misfire," both of which are included in the misfire state, and determines which state it is. A full misfire means that the mixture in the cylinder did not burn (there was no combustion reaction, a complete misfire). A semi-misfire means that only a portion of the mixture in the cylinder burned, that the mixture burned incompletely due to slow combustion, or that the combustion reaction stopped midway.

[0014] A crank angle sensor 2, an accelerator opening sensor 3, and a vehicle speed sensor 4 are connected to the misfire detection device 10. In this embodiment, the misfire detection device 10 determines whether the engine 1 is in a misfire state based on at least the crank angle θ detected by the crank angle sensor 2 and the crank angular velocity Ne, which is its time derivative. Information related to the vehicle's running state (accelerator opening, vehicle speed, etc.) may be taken into consideration when determining whether the engine 1 is in a misfire state, but is not required to be taken into consideration. The determination result is reflected in the notification device 5.

[0015] The notification device 5 is an output device, such as a warning light or a display device, for notifying a passenger of the misfire state determined by the misfire detection device 10. For example, if it is determined that the engine 1 is in a misfire state, an indicator or telltale mark indicating the misfire state is lit on the notification device 5. If it is determined that the combustion state of the engine 1 is normal, the indicator or telltale mark indicating the misfire state is turned off. The notification device 5 may be capable of distinguishing between a full misfire and a partial misfire, or may be capable of notifying the occurrence of poor combustion without distinguishing between the two. The result of the determination by the misfire detection device 10 is preferably recorded in a storage device of the misfire detection device 10 as diagnostic result information (diagnosis information).

[0016] [2. Misfire detection device] As shown in Fig. 1, the misfire detection device 10 is provided with a calculation unit 11, a determination unit 12, and a misfire map 13. These elements are shown by conveniently classifying the functions of the misfire detection device 10 for determining the misfire state of the engine 1. Each of these elements may be configured as an independent program (or database), or may be written as a composite program combining multiple functions.

[0017] The calculation unit 11 calculates the first deviation ΔNe based on the crank angular velocity Ne in the combustion stroke of the engine 1. A and the second deviation ΔNe B The first deviation ΔNe is calculated. Ais a parameter that represents the degree of change in the crank angular velocity Ne in the first half of the combustion stroke of the engine 1, and the second deviation ΔNe B is a parameter that represents the degree of change in the crank angular velocity Ne in the latter half of the combustion stroke of the engine 1. A has the characteristic of rising appropriately even during deceleration of the vehicle, as long as the combustion state of the engine 1 is normal.

[0018] In this embodiment, since the engine 1 is a four-cylinder, four-stroke gasoline engine, a combustion stroke is performed in one of the cylinders every half rotation of the crank angle θ, and the first deviation ΔNe A is calculated. In addition, the second deviation ΔNe B is at least the first deviation ΔNe A When it is determined that there is no possibility of misfire in the engine 1, the second deviation ΔNe in the combustion stroke is calculated. B The calculation of can be omitted.

[0019] First deviation ΔNe A A specific example of this is the amount of change in crank angular velocity Ne between two points included in the first half of the combustion stroke. Alternatively, a plurality of crank angular velocities Ne between two points included in the first half of the combustion stroke may be calculated, and the average or median of these values ​​may be used as the first deviation ΔNe. A Similarly, the second deviation ΔNe B A specific example of this is the amount of change in crank angular velocity Ne between two points included in the latter half of the combustion stroke. Alternatively, a plurality of crank angular velocities Ne between two points included in the latter half of the combustion stroke may be calculated, and the average or median of these values ​​may be used as the second deviation ΔNe. B It may be calculated as:

[0020] In this embodiment, as shown in Figure 2, the crank angular velocity Ne when the crank angle θ is a first angle θ1 in the first half of the combustion stroke is defined as a first angular velocity Ne1, and the crank angular velocity Ne when the crank angle θ is a second angle θ2 in the first half of the combustion stroke is defined as a second angular velocity Ne2. The range of crank angles θ from the first angle θ1 to the second angle θ2 is called a first crank angle range P1. First deviation ΔNe A has a value obtained by subtracting the first angular velocity Ne1 from the second angular velocity Ne2 (ΔNe A If the crank angle θ changes from the first angle θ1 to the second angle θ2 and the crank angular velocity Ne decreases, the first deviation ΔNe A will be negative.

[0021] Similarly, in this embodiment, the crank angular velocity Ne when the crank angle θ is a third angle θ3 in the latter half of the combustion stroke is referred to as a third angular velocity Ne3, and the crank angular velocity Ne when the crank angle θ is a fourth angle θ4 in the latter half of the combustion stroke is referred to as a fourth angular velocity Ne4. The range of crank angles θ from the third angle θ3 to the fourth angle θ4 is referred to as a second crank angle range P2. The second deviation ΔNe B has a value obtained by subtracting the third angular velocity Ne3 from the fourth angular velocity Ne4 (ΔNe B If the crank angle θ changes from the third angle θ3 to the fourth angle θ4 and the crank angular velocity Ne decreases, the second deviation ΔNe B will be negative.

[0022] The first half of the combustion stroke and the second half of the combustion stroke can be defined in the following two ways. The first definition is based on the crank angle θ, and defines the first half of the entire combustion stroke, i.e., in this embodiment (a four-cylinder, four-stroke gasoline engine), as the range of θ<90° ATDC, and the second half, i.e., the range of 90≦θ[° ATDC], as the second half of the combustion stroke. Note that the boundary value between the first and second half (90° ATDC) may be changed depending on the type and operating state of the engine 1, etc.

[0023] The second definition is based on the crank angular velocity Ne, and defines the period before the time (or crank angle θ) when the crank angular velocity Ne reaches its maximum in the combustion stroke as the first half of the combustion stroke, and the period after that time (or crank angle θ) as the second half of the combustion stroke. In either case, the angle corresponding to the start of the combustion stroke is around 0° ATDC, and the angle corresponding to the end is around 180° ATDC. However, the times (or crank angle θ) corresponding to the start and end of the combustion stroke can be changed as appropriate depending on the characteristics and type of engine 1. Furthermore, the time (or crank angle θ) that marks the boundary between the first and second halves may be shifted forward or backward based on the time (or crank angle θ) at which crank angular velocity Ne is at its maximum.

[0024] In this application, the "combustion stroke" refers to the combustion stroke of the entire engine 1. That is, in a four-cylinder, four-stroke gasoline engine, the strokes of each cylinder are shifted by 180° with respect to the crank angle θ, so the combustion strokes occur every 180° and start and end within a range of 180°.

[0025] The determination unit 12 determines the first deviation ΔNe A Based on this, the possibility of misfire in engine 1 is determined, and the second deviation ΔNe B The possibility of misfire is judged based on the first deviation ΔNe. A For example, as shown in FIG. 3A, the first deviation ΔNe A is less than the first threshold value C1, it is determined that "there is a possibility of misfire in the engine 1." The first threshold value C1 may be a positive value or a negative value. The first threshold value C1 may be a fixed value that is set in advance, or may be a variable value that is set depending on the operating state of the engine 1 and the running state of the vehicle.

[0026] First deviation ΔNe A If it is determined that there is a possibility of misfire based on the second deviation ΔNe, BThe type of misfire (whether it is a real misfire or a partial misfire) is determined based on the first deviation ΔNe obtained from the first half of a certain combustion stroke. A is less than the first threshold C1, the second deviation ΔNe obtained from the second half of the same combustion process B is checked, and it is determined whether the misfire in engine 1 is a real misfire or a partial misfire.

[0027] On the other hand, the first deviation ΔNe obtained from the first half of a certain combustion process A If the first threshold value C1 or more is greater than the first threshold value C1, it is considered that there is no possibility of misfire in that combustion stroke (the combustion state is normal), so the second deviation ΔNe obtained from the latter half of that combustion stroke B In this sense, in the combustion stroke where it is determined that there is no possibility of misfire, the second deviation ΔNe in the calculation unit 11 is B The calculation of can be omitted.

[0028] In this embodiment, two methods will be described as methods for determining the type of misfire. B For example, as shown in FIG. 3B, the second deviation ΔNe B is less than the second threshold C2, it is judged as a "main misfire", and the second deviation ΔNe B is equal to or greater than the second threshold C2, it is determined that a "semi-misfire" has occurred. The determination result is reflected in, for example, the alarm device 5. The second threshold C2 may be a positive value or a negative value. The second threshold C2 may be a fixed value that is set in advance, or may be a variable value that is set depending on the operating state of the engine 1 and the running state of the vehicle.

[0029] The second method is to determine whether a misfire is occurring or not by taking into consideration the degree of deceleration of the vehicle. For example, when the degree of deceleration of the vehicle is large, the crank angular velocity Ne may suddenly decrease significantly, and the second deviation ΔNe Bis likely to be less than the second threshold value C2. In other words, even if the engine 1 is not actually experiencing poor combustion, it may be erroneously determined that the engine 1 has experienced a serious misfire. Therefore, the stronger the degree of deceleration, the greater the second deviation ΔNe B It is conceivable that the erroneous determination of the misfire can be suppressed by increasing the value of the first deviation ΔNe or decreasing the second threshold C2. The degree of deceleration may be grasped based on information relating to the running state of the vehicle (accelerator opening, vehicle speed, etc.) or may be grasped from the change in the crank angle θ. For example, the above-mentioned first deviation ΔNe A It may be understood based on the

[0030] Figure 4 shows the first deviation ΔNe A 4 is a graph for explaining a method for grasping the degree of deceleration based on the above. The thick solid line in FIG. 4 is a graph showing the change in crank angular velocity Ne during normal combustion when the vehicle is not decelerating (when the vehicle is traveling at a substantially constant speed). On the other hand, the dashed line in FIG. 4 is a graph showing an example of the change in crank angular velocity Ne when the engine 1 misfires (full misfire or semi-misfire) when the vehicle is not decelerating. Also, ΔNe in FIG. 4 mf is the amount of decrease in the crank angular velocity Ne when the crank angle θ changes from the first angle θ1 to the second angle θ2 in the dashed line graph. Hereinafter, this will be referred to as the estimated deviation ΔNe mf It is called.

[0031] The thin solid line in Fig. 4 is a graph showing the change in crank angular velocity Ne when the engine 1 experiences a semi-misfire during deceleration of the vehicle, and the two-dot chain line in Fig. 4 is a graph showing the change in crank angular velocity Ne when the engine 1 experiences a full misfire during deceleration of the vehicle. As shown in these graphs, during deceleration of the vehicle, the crank angular velocity Ne may suddenly decrease significantly due to the influence of the deceleration. At this time, the first deviation ΔNe during deceleration in the first crank angle range P1 A includes the amount of change in crank angular velocity Ne due to poor combustion and the amount of change in crank angular velocity Ne due to the effect of deceleration.

[0032] Here, the former change amount is the change amount of the crank angular velocity Ne that is not affected by deceleration, so the estimated deviation ΔNe mf Therefore, the latter change amount is the first deviation ΔNe A Estimated deviation ΔNe from mf The amount of change due to the effect of deceleration (deceleration rate (ΔNe A -ΔNe mf ) ) is the first deviation ΔNe A Not only the second deviation ΔNe B Therefore, the change due to the effect of deceleration (ΔNe A -ΔNe mf ) the second deviation ΔNe B By subtracting this from the third deviation ΔNe, a corrected value can be obtained that excludes the effect of deceleration. C The third deviation ΔNe C By comparing the magnitude relationship between the second threshold C1 and the second threshold C2, it becomes possible to accurately determine whether the type of misfire during deceleration is a real misfire or a semi-misfire.

[0033] In addition, when the first crank angle range P1 and the second crank angle range P2 are different, the second deviation ΔNe is calculated in accordance with the ratio (P2 / P1) of the second crank angle range P2 to the first crank angle range P1. B The value to be subtracted from the third deviation ΔNe can be adjusted. C is the first deviation ΔNe A and estimated deviation ΔNe mf The difference (ΔNe A -ΔNe mf ) and the ratio (P2 / P1) of the second crank angle range P2 to the first crank angle range P1, B can be obtained by subtracting from C =ΔNe B -(P2 / P1)×(ΔNe A -ΔNe mf ).

[0034] The above estimated deviation ΔNe mfThe estimated deviation ΔNe may be a preset fixed value, but is preferably set as a variable value having a magnitude according to the operating state of the engine 1. mf is set, for example, in accordance with the crank angular velocity Ne, and is set, for example, in accordance with the load of the engine 1 (engine torque, intake air amount, charging efficiency, etc.). mf may be corrected according to the vehicle's running conditions (outside temperature, outside air pressure, etc.). mf When the engine 1 misfires (full misfire or partial misfire) while the vehicle is not decelerating, that is, when the first deviation ΔNe A becomes less than the first threshold value C1, the amount of change in the crank angular velocity Ne in the first crank angle range P1 may be stored.

[0035] The misfire detection device 10 of this embodiment stores a misfire map 13 as shown in Fig. 5 in a storage device. This misfire map 13 is used to calculate the crank angular velocity Ne and the load and estimated deviation ΔNe when the engine 1 misfires (full misfire or partial misfire) while the vehicle is not decelerating. mf This is a three-dimensional map that defines the relationship between the crank angular velocity Ne and the load and the estimated deviation ΔNe. mf The relationship between the estimated deviation ΔNe and the actual deviation ΔNe is determined through tests and experiments and is specified in advance. mf The value of θ is set to be larger as the crank angular velocity Ne or the load increases, for example.

[0036] [3.Effects] (1) The misfire detection device 10 of this embodiment includes a calculation unit 11 and a determination unit 12. The calculation unit 11 calculates a first deviation ΔNe that represents a change tendency of the crank angular velocity Ne in the first half of the combustion stroke of the engine 1. A and the second deviation ΔNe, which represents the change tendency of the crank angular velocity Ne in the latter half of the combustion stroke. B The determination unit 12 also calculates the first deviation ΔNe. A Determine the possibility of misfire of engine 1 based on the second deviation ΔNe B Based on this, it is determined whether the misfire in engine 1 is a real misfire or a partial misfire.

[0037] First deviation ΔNe in the first half of the combustion stroke A Even if the vehicle is decelerating, as long as the combustion state is normal, the first deviation ΔNe of this characteristic rises appropriately. A By determining the possibility of misfire in the engine 1 based on the second deviation ΔNe, it is possible to easily avoid erroneous determination of a misfire state during deceleration, and to realize misfire determination that is less susceptible to the influence of disturbances (such as deceleration of the vehicle). Therefore, the accuracy of determining poor combustion can be improved with a simple configuration. B Based on this, it is possible to determine whether the misfire in engine 1 is a real misfire or a semi-misfire, and therefore it is possible to perform control to eliminate the misfire according to the misfire state, such as changing the increase in the fuel injection amount depending on whether it is a real misfire or a semi-misfire.

[0038] (2) The determination unit 12 of this embodiment determines the first deviation ΔNe A is less than the first threshold C1, it is determined that there is a possibility of misfire in the engine 1, and the second deviation ΔNe B Then, for example, the second deviation ΔNe B If the second deviation ΔNe is equal to or greater than the second threshold C2, it is determined to be a semi-misfire. B If the value is less than the second threshold value C2, it is determined that a misfire has occurred.

[0039] With this configuration, the first deviation ΔNe A In the situation where it is judged that there is no possibility of misfire of engine 1, the second deviation ΔNe B Therefore, it is possible to reduce the occurrence of erroneous determination of a misfire state, and improve the accuracy of determining poor combustion with a simple configuration. B By omitting the determination based on the above, the calculation load can be reduced, and the power consumption of the misfire detection device 10 can be reduced.

[0040] (3) The determination unit 12 of this embodiment is configured to determine whether a misfire is occurring or not, taking into account the degree of deceleration of the vehicle equipped with the engine 1. For example, as shown by the thin solid line in FIG. 4, when a semi-misfire occurs during deceleration, the rise in the crank angular velocity Ne in the latter half of the combustion stroke may be small due to the influence of deceleration. On the other hand, by determining whether a misfire is occurring or not, taking into account the degree of deceleration, it becomes possible to grasp the behavior of the crank angular velocity Ne after the influence of deceleration has been removed. Therefore, the accuracy of determining poor combustion can be improved with a simple configuration.

[0041] (4) The determination unit 12 of this embodiment determines the first deviation ΔNe in the first half of the combustion stroke. A The degree of deceleration can be grasped based on the second deviation ΔNe in the latter half of the combustion stroke. B Based on the value corrected in accordance with the degree of deceleration, it is possible to determine whether a misfire has occurred or whether it is a partial misfire. A Using the deceleration rate (ΔNe A -ΔNe mf ) can be calculated, the degree of deceleration can be grasped with high accuracy without excessively increasing the calculation load, and the accuracy of determining poor combustion can be improved with a simple configuration.

[0042] (5) As shown in Fig. 1, the misfire detection device 10 of this embodiment may include a misfire map 13. The misfire map 13 defines the relationship between the crank angular velocity Ne, the load on the engine 1, and the deceleration rate when the engine 1 misfires while the vehicle is not decelerating. For example, as shown in Fig. 5, the relationship between the crank angular velocity Ne and the load and the estimated deviation ΔNe mf The relationship between the above is defined in the misfire map 13 as a three-dimensional map.

[0043] Further, the calculation unit 11 calculates the estimated deviation ΔNe based on the misfire map 13. mf can be calculated, and the first deviation ΔNe A and estimated deviation ΔNe mf The difference (ΔNe A -ΔNe mf ) can be calculated. The difference (ΔNe A -ΔNemf The value of the second deviation ΔNe corresponds to the degree of deceleration of the vehicle. B from the difference (ΔNe A -ΔNe mf ) (i.e., the third deviation ΔNe C ) based on which a real misfire or a partial misfire can be determined.

[0044] With this configuration, the effect of deceleration can be quantitatively evaluated to determine the second deviation ΔNe B The third deviation ΔNe after correction can be corrected. C Furthermore, by preparing the misfire map 13 in advance, the influence of deceleration can be quickly quantified without requiring complex estimation calculations, and the second deviation ΔNe can be calculated with high accuracy. B Therefore, the accuracy of determining imperfect combustion can be improved with a simple configuration.

[0045] [4. Other] The above-described embodiment is merely illustrative, and does not intend to exclude various modifications or applications of techniques not explicitly described in the present embodiment. The components of the present embodiment can be modified in various ways without departing from the spirit of the present embodiment. Furthermore, the components of the present embodiment can be selected or combined as needed. For example, while the above-described embodiment illustrates a misfire detection device 10 applied to an engine 1 mounted on a vehicle, the application of the misfire detection device 10 is not limited to automobile engines, but can also be applied to marine engines, industrial engines, general-purpose engines, and the like.

[0046] [5. Notes] The following notes are provided regarding the above-described embodiments and modifications. [Appendix 1] The first deviation (ΔNe) represents the change tendency of the crank angular velocity (Ne) in the first half of the combustion stroke of the engine (1). A ) and a second deviation (ΔNe B ) a calculation unit (11) for calculating The first deviation (ΔNe A) based on which the possibility of misfire of the engine (1) is determined, and the second deviation (ΔNe B a determination unit (12) for determining whether a misfire in the engine (1) is a serious misfire or a partial misfire based on the A misfire detection device (10) for an engine (1), comprising:

[0047] [Appendix 2] The determination unit (12) determines the first deviation (ΔNe A ) is less than a first threshold value (C1), it is determined that there is a possibility of misfire in the engine (1) and the second deviation (ΔNe B ) and the second deviation (ΔNe B ) is equal to or greater than a second threshold value (C2), the second deviation (ΔNe B ) is less than the second threshold value (C2), the main misfire is determined to have occurred. 2. A misfire detection device (10) for an engine (1) according to claim 1.

[0048] [Appendix 3] The determining unit (12) determines whether the engine (1) is a real misfire or a partial misfire by taking into consideration the degree of deceleration of the vehicle in which the engine (1) is mounted. 3. A misfire detection device (10) for an engine (1) according to claim 1 or 2.

[0049] [Appendix 4] The determination unit (12) determines the first deviation (ΔNe A ) based on which the degree of deceleration is grasped, and the second deviation (ΔNe B ) is corrected in accordance with the degree of deceleration, and the determination of the actual misfire and the partial misfire is based on the corrected value. 4. A misfire detection device (10) for an engine (1) according to claim 3.

[0050] [Appendix 5] The crank angular velocity (Ne) in the first half of the combustion stroke when the engine (1) misfires while the vehicle is not decelerating, and the estimated deviation (ΔNe) which is the deviation between the load of the engine (1) and the crank angular velocity (Ne) mf ) a map (13) defining a relationship between The calculation unit (11) calculates the estimated deviation (ΔNe mf ) and the first deviation (ΔNe A ) and the estimated deviation (ΔNe mf ) and the difference (ΔNe A -ΔNe mf ) is calculated, The determination unit (12) determines the second deviation (ΔNe B ) from the estimated deviation (ΔNe mf ) and the first deviation (ΔNe A ) minus the difference (ΔNe C ) based on which the main misfire and partial misfire are judged. 5. A misfire detection device (10) for an engine (1) according to claim 4. [Industrial Applicability]

[0051] The present invention is applicable to the manufacturing industry of engine misfire detection devices, and also applicable to the manufacturing industry of vehicles, ships, industrial machinery, etc. that are equipped with engines to which misfire detection devices are applied. [Explanation of symbols]

[0052] 1 engine 2 crank angle sensor 3 Accelerator opening sensor 4 Vehicle speed sensor 5. Alarm device 10 Misfire detection device 11 Calculation section 12 Judgment Department 13 Misfire Map (Map) Ne crank angular velocity Ne1 first angular velocity Ne2 second angular velocity Ne3 triangular velocity Ne4 square velocity ΔNe A First deviation ΔNe B second deviation ΔNe C third deviation ΔNe mf Estimated deviation C1 First Threshold C2 Second Threshold θ1 first angle θ2 second angle θ3 third angle θ4 quadrature P1 First crank angle range P2 Second crank angle range

Claims

1. a calculation unit that calculates a first deviation representing a change tendency of a crank angular velocity in a first half of a combustion stroke of an engine and a second deviation representing a change tendency of the crank angular velocity in a second half of the combustion stroke; a determination unit that determines the possibility of a misfire in the engine based on the first deviation, and determines whether the misfire in the engine is a real misfire or a partial misfire based on the second deviation; An engine misfire detection device comprising:

2. The determination unit determines that there is a possibility of misfire in the engine when the first deviation is less than a first threshold value and checks the second deviation, determines that there is a partial misfire when the second deviation is equal to or greater than a second threshold value, and determines that there is a real misfire when the second deviation is less than the second threshold value.

2. The engine misfire detection device according to claim 1.

3. The determination unit determines whether the misfire is a real misfire or a partial misfire by taking into consideration the degree of deceleration of the vehicle in which the engine is mounted.

2. The engine misfire detection device according to claim 1.

4. The determination unit grasps the degree of deceleration based on the first deviation in the first half of the combustion stroke, and determines the main misfire and the partial misfire based on a value obtained by correcting the second deviation in the second half of the combustion stroke according to the degree of deceleration.

4. The engine misfire detection device according to claim 3.

5. a map defining a relationship between the crank angular velocity in the first half of the combustion stroke and an estimated deviation that is a deviation between the load on the engine and the crank angular velocity when the engine misfires while the vehicle is not decelerating, the calculation unit calculates the estimated deviation based on the map and calculates a difference between the first deviation and the estimated deviation; The determination unit determines whether the misfire is a real misfire or a partial misfire based on a value obtained by subtracting the difference between the estimated deviation representing the degree of deceleration and the first deviation from the second deviation.

5. The engine misfire detection device according to claim 4.

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