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, a correction section 12, and a determination section 13. The calculation section 11 calculates a deviation D which is obtained by subtracting a first angle speed Ne1 which is a crank angle speed Ne when a crank angle θ is a first angle θ1 in a former half of a combustion stroke of the engine 1 from a second angle speed Ne2 which is the crank angle speed Ne when the crank angle θ is a second angle θ2 in a latter half of the combustion stroke. The correction section 12 calculates a corrected deviation C which is obtained by correcting the deviation D on the basis of an average engine angle speed deviation A in correspondence with a change tendency of the crank angle speed Ne in a prescribed crank angle range P2. The determination section 13 determines a misfire state of the engine 1 on the basis of the corrected deviation C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a misfire detection device for detecting misfires and semi-misfires in 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's crank angular velocity (engine rotation speed). For example, one technique calculates 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, and compares this amount of fluctuation with a predetermined misfire determination value to determine whether or not a misfire has occurred. It has also been proposed to set a lenient misfire determination value during sudden acceleration and deceleration in order to avoid erroneous misfire determination (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4490721 [Patent Document 2] Japanese Patent Application Publication No. 05-018311 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, if the criteria for determining misfire during sudden acceleration and deceleration are simply relaxed, as in the conventional technology, it becomes difficult to accurately identify poor combustion that is close to misfire (for example, slow combustion or misfire during combustion), and there is a risk that the accuracy of determining the misfire state will decrease. For example, as a result of relaxing the criteria for determining misfire, there is a possibility that misfire will not be detected even if a slight misfire (poor combustion) actually occurs.

[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 a misfire state 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 deviation by subtracting a first angular velocity, which is the crank angular velocity when the crank angle is a first angle in the first half of the engine combustion stroke, from a second angular velocity, which is the crank angular velocity when the crank angle is a second angle in the second half of the combustion stroke; a correction unit that calculates a corrected deviation by correcting the deviation based on an average engine angular velocity deviation that corresponds to a change trend of the crank angular velocity within a specified crank angle range; and a determination unit that determines a misfire state of the engine based on the corrected deviation. The correction deviation corresponds to the change trend of the crank angular velocity, and is calculated so as to avoid erroneous determination of a misfire state caused by a decrease in the change trend of the crank angular velocity when the change trend of the crank angular velocity is a decrease. [Effects of the Invention]

[0007] According to the disclosed engine misfire detection device, the accuracy of determining a misfire state can be improved with a simple configuration by using a correction deviation corrected based on the average engine angular velocity deviation. [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] 1 is a graph illustrating an average engine angular velocity deviation A, a gradient influence value B, a correction deviation C, and a deviation D calculated by the misfire detection device, and showing a change in crank angular velocity Ne with respect to crank angle θ. [Figure 3]FIG. 4 is a diagram for explaining the relationship between the correction deviation C and a misfire state. 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 as an embodiment is applied to an on-vehicle engine 1 shown in FIG. 1. This engine 1 is a four-cylinder, four-stroke gasoline engine. FIG. 1 shows one of the four cylinders provided in the engine 1. The engine 1 is provided with a fuel injection valve 2 and a spark plug 3. The fuel injection valve 2 is provided, for example, in an intake port for introducing intake air into the cylinder, and the spark plug 3 is provided at the top of the combustion chamber. If the engine 1 is a direct injection engine, the fuel injection valve 2 is provided in the combustion chamber. It is also possible to provide the fuel injection valve 2 in both the intake port and the combustion chamber.

[0011] A crank angle sensor 4 is provided near the crankshaft of the engine 1 to detect the crank angle θ. The crank angle sensor 4 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 (for example, 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. A catalytic device 5 for purifying exhaust gas is installed in the exhaust passage of the engine 1. Specific examples of the catalytic device 5 include a three-way catalyst, an oxidation catalyst, a DPF catalyst, an SCR catalyst, and a storage reduction catalyst. A catalyst temperature sensor 6 for detecting the catalyst temperature is provided near or inside the catalytic device 5.

[0012] An accelerator pedal depression sensor 8 that detects the amount of depression of the accelerator pedal (accelerator depression) and a vehicle speed sensor 9 that detects a parameter corresponding to the vehicle speed (vehicle running speed) are provided at arbitrary positions on the vehicle. The accelerator pedal depression is a parameter that corresponds to the driver's request for acceleration / deceleration, intention to start, intention to brake, etc. The vehicle speed sensor 9 also detects, for example, wheel speed, angular velocity of the wheel axle, or engine rotation speed. The vehicle speed is calculated based on these values.

[0013] This vehicle is equipped with a catalyst control device 7 for raising the temperature of the catalyst device 5 and a misfire detection device 10 for determining the misfire state of the engine 1. These are both electronic control units (ECUs). Each electronic control device has a built-in processor (central processing unit), memory (main memory), storage device, interface device, etc. (not shown), which are connected to each other so that they can communicate with each other. The contents of the control executed by each electronic control device are recorded and saved in the memory or storage device as firmware or application programs. When a program is executed, the contents of the program are expanded in memory space and arithmetic processing is performed by the processor.

[0014] The catalyst control device 7 performs temperature rise control to adjust the operating state of the engine 1 so that the catalyst temperature is in a predetermined active temperature range or so that the catalyst temperature is within a temperature range suitable for purifying exhaust gas. For example, when the engine 1 is cold started, in order to quickly raise the catalyst temperature to the active temperature range, the catalyst control performs air-fuel ratio control to adjust the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio, fuel injection control to retard the fuel injection timing, and ignition timing control to retard the ignition timing. These temperature rise controls raise the exhaust gas temperature, and the catalyst temperature quickly rises to the active temperature range.

[0015] Furthermore, when the amount of exhaust particulate matter accumulated in the catalytic converter 5 increases, the above-described air-fuel ratio control, fuel injection control, and ignition timing control are carried out in order to burn the exhaust particulate matter. These temperature rise controls allow the exhaust particulate matter to be burned quickly. Alternatively, when the amount of substances to be occluded (such as nitrogen oxides, hydrocarbons, etc.) in the catalytic converter 5 increases and exceeds a predetermined amount, the above-described air-fuel ratio control, fuel injection control, and ignition timing control are carried out to purify the substances to be occluded while desorbing them. These temperature rise controls allow the substances to be occluded to be efficiently purified.

[0016] The misfire detection device 10 determines whether the engine 1 is in a misfire state. It determines at least whether the combustion state in the cylinder is normal or not. The misfire detection device 10 of this embodiment has the function of distinguishing between a "misfire (complete misfire)" and a "semi-misfire," both of which are misfire states. A misfire means that the air-fuel mixture in the cylinder did not burn (there was no combustion reaction). A semi-misfire means that only a portion of the air-fuel mixture in the cylinder burned, that the air-fuel mixture burned incompletely due to slow combustion, or that the combustion reaction stopped midway.

[0017] The misfire detection device 10 is connected to a crank angle sensor 4, a catalyst control device 7, an accelerator opening sensor 8, and a vehicle speed sensor 9. In this embodiment, the misfire detection device 10 determines whether the engine 1 is in a misfire state based on the crank angle θ detected by the crank angle sensor 4 and the crank angular velocity Ne, which is its time derivative. The misfire detection device 10 also determines whether the engine 1 is in a misfire state by taking into account information related to the operating state of the engine 1 (accelerator opening, vehicle speed, and implementation status of temperature rise control of the catalyst device 5). The result of this determination is reflected in a notification device 14.

[0018] The alarm device 14 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 alarm device 14. On the other hand, 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.

[0019] As shown in Fig. 1, the misfire detection device 10 is provided with a calculation unit 11, a correction unit 12, and a determination unit 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. These elements may be written as independent programs, or as a composite program combining all of these functions.

[0020] The calculation unit 11 calculates a deviation D between the crank angular velocity Ne in the first half of a combustion stroke and the crank angular velocity Ne in the second half of the combustion stroke during the combustion cycle of the engine 1 during the combustion stroke of an air-fuel mixture. Here, the crank angular velocity Ne when the crank angle θ is a first angle θ1 during the first half of the combustion stroke of the engine 1 is defined as a first angular velocity Ne1. Also, the crank angular velocity Ne when the crank angle θ is a second angle θ2 during the second half of the combustion stroke is defined as a second angular velocity Ne2. The calculation unit 11 subtracts the first angular velocity Ne1 from the second angular velocity Ne2 to calculate the deviation D (D = Ne2 - Ne1).

[0021] The first angle θ1 is set in the first half of the combustion stroke of the engine 1, and the second angle θ2 is set in the second half of the combustion stroke of the engine 1. The range between the first angle θ1 and the second angle θ2 is referred to as a judgment angle width P1. In this embodiment, the values ​​of the first angle θ1 and the second angle θ2 are set so that the judgment angle width P1 is 130° (θ2 = θ1 + 130°).

[0022] There are two possible definitions for the first half of the combustion stroke and the second half of the combustion stroke. 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 θ<90° ATDC, and the second half, i.e., the range 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.

[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 this embodiment, 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. Note that 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) when the crank angular velocity Ne reaches 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 correction unit 12 corrects the deviation D in consideration of the influence of the overall change tendency that levels the periodic fluctuation of the crank angular velocity Ne. The correction unit 12 calculates the average engine angular velocity deviation A corresponding to the overall change tendency (degree of increase or decrease, inclination, trend) of the crank angular velocity Ne in the predetermined crank angle range P2, and calculates the correction deviation C obtained by correcting the deviation D based on the average engine angular velocity deviation A.

[0026] The predetermined crank angle range P2 is preferably a range that is short enough to reflect the overall change tendency of the crank angular velocity Ne and long enough to ensure a sufficient number of samplings. For example, the predetermined crank angle range P2 is preferably wider than the determination angle width P1 (P1 < P2), and is preferably set so as to completely include the determination angle width P1 (the start point of the predetermined crank angle range P2 is before the start point of the determination angle width P1, and the end point of the predetermined crank angle range P2 is after the end point of the determination angle width P1). In this embodiment, since the misfire determination calculation is performed every 180° with respect to the crank angle θ, the end point of the predetermined crank angle range P2 may be positioned within the misfire determination calculation range that includes the determination angle width P1.

[0027] The predetermined crank angle range P2 may be set based on the fluctuation period of the crank angular velocity Ne. For example, in a four-cylinder, four-stroke engine, the combustion stroke is repeated at a crank angle period of 180°. Therefore, it is conceivable to set the predetermined crank angle range P2 to 180°. Note that if the predetermined crank angle range P2 is around 180° (e.g., 160 to 200°), the overall change trend of the crank angular velocity Ne can be grasped, so the predetermined crank angle range P2 does not need to be set to 180° exactly. The predetermined crank angle range P2 may also be set to a range around an integer multiple of 180° (e.g., 160 to 200°, 340 to 380°, 520 to 560°, 700 to 740°, etc.). Similarly, in a three-cylinder, four-stroke engine, the combustion stroke of each cylinder is repeated at a crank angle period of 240°. Therefore, the predetermined crank angle range P2 may be set to about 240° (for example, 220 to 260°) or to a range of about an integral multiple of 240° (for example, 220 to 260°, 460 to 500°, 700 to 740°, etc.).

[0028] However, since the purpose of the predetermined crank angle range P2 is to observe the overall change tendency of the crank angular velocity Ne in the vicinity of the judgment angle range P1, it is preferable that the width of the predetermined crank angle range P2 is not too large. If the width of the predetermined crank angle range P2 is too large, it will reflect the change tendency of the crank angular velocity Ne at timing unrelated to the judgment angle range P1. Therefore, it is preferable that the predetermined crank angle range P2 be set to the crank angle period of the combustion stroke (180° in a four-cylinder four-stroke engine).

[0029] In this embodiment, the crank angle θ at the end of the predetermined crank angle range P2 is set to coincide with the second angle θ2, and the width of the predetermined crank angle range P2 is set to 180°. Here, the crank angle θ at the start of the predetermined crank angle range P2 is designated as a third angle θ3, and the crank angular velocity Ne when the crank angle θ is the third angle θ3 is designated as a third angular velocity Ne3. The third angle θ3 is the crank angle 180° before the second angle θ2 (θ3 = θ2 - 180°).

[0030] The correction unit 12 calculates the average engine angular velocity deviation A by subtracting the third angular velocity Ne3 from the second angular velocity Ne2 (A=Ne2-Ne3). The value of the average engine angular velocity deviation A represents the amount by which the crank angular velocity Ne increases or decreases from the start point to the end point of the predetermined crank angle range P2. To reflect this value in the deviation D, the correction unit 12 calculates a gradient influence value B, which is the product of the average engine angular velocity deviation A and the ratio of the determination angle width P1 between the first angle θ1 and the second angle θ2 with respect to the predetermined crank angle range P2 [B=A×(P1 / P2)].

[0031] The gradient influence value B represents the degree to which the overall change trend of the crank angular velocity Ne affects the deviation D. The correction unit 12 then subtracts the gradient influence value B from the deviation D to calculate a corrected deviation C (C=DB). The corrected deviation C corresponds to the deviation D obtained by removing the influence of the overall change trend of the crank angular velocity Ne. In other words, the corrected deviation C represents the degree to which the crank angular velocity Ne has changed during the determination angle width P1 when the overall change trend is removed from the fluctuations in the crank angular velocity Ne and the resulting fluctuations are normalized to a constant periodic fluctuation.

[0032] The determination unit 13 determines whether the engine 1 is in a misfire state based on the correction deviation C. Here, the misfire state is determined using the relationship between the correction deviation C and the misfire state, for example, as shown in FIG. 3. In this embodiment, the determination unit 13 determines that the combustion state is normal when the correction deviation C exceeds the first determination value C1. In this case, an indicator or telltale mark indicating the misfire state is not displayed on the alarm device 14. The first determination value C1 may be a positive value or a negative value. The value of the first determination value C1 may be set based on experiments, analysis, etc., to a value that can determine whether the combustion state is normal or not, based on the set values ​​of the first angle θ1 and the second angle θ2.

[0033] On the one hand, when the correction deviation C is less than or equal to the first determination value C1, the determination unit 13 determines that the engine 1 is in a misfire state, and outputs a signal for causing an indicator or a tail mark indicating the misfire state to be displayed on the lighting of the notification device 14. Further, when the correction deviation C is less than or equal to the first determination value C1 and exceeds the second determination value C2 (where C2 < C1), the determination unit 13 determines that it is a semi-misfire. On the other hand, when the correction deviation C is less than or equal to the second determination value C2, the determination unit 13 determines that it is a complete misfire. When the notification device 14 can display the semi-misfire and the misfire separately, an indicator or a tail mark corresponding to each state may be caused to be displayed on the lighting of the notification device 14. When the determination unit 13 determines that the engine 1 is in a semi-misfire state, control for eliminating the semi-misfire, such as increasing the fuel injection amount, may be performed.

[0034] Note that since the semi-misfire is not a complete misfire, when the determination unit 13 determines that it is a semi-misfire, it may not be displayed on the notification device 14. Further, the determination of a complete misfire may be made when the determination unit 13 makes a misfire determination a plurality of times (when the correction deviation C becomes less than or equal to the second determination value C2 over a plurality of times).

[0035] In the above determination, a control configuration may be adopted such that the determination unit 13 determines the misfire state of the engine 1 only when a predetermined condition is satisfied. For example, when any of the following conditions is satisfied, the determination unit 13 may be made to determine the misfire state of the engine 1. Condition 1. The vehicle is decelerating for a predetermined time or more Condition 2. The temperature increase control of the catalyst device 5 is being performed

[0036] Condition 1 can be determined based on the accelerator opening and the vehicle speed. For example, when the accelerator opening decreases from a certain large value and that state continues for a predetermined time or more (for example, 1 second or more), it may be determined that Condition 1 is satisfied. Alternatively, when the vehicle speed continues to decrease for a predetermined time or more (for example, 1 second or more), it may be determined that Condition 1 is satisfied. Condition 2 can be determined based on the operating state of the catalyst control device 7. For example, it may be determined that Condition 2 is met when the catalyst control device 7 is performing air-fuel ratio control, fuel injection control, and ignition timing control to raise the temperature of the catalyst device 5.

[0037] If neither condition 1 nor 2 is met, the determination unit 13 may stop determining whether a misfire is occurring. In this case, misfire may be determined from a temporary drop in average rotation speed, using a conventional misfire determination method, such as determining misfire based on the deviation between the previous and previous angular accelerations (the rate of change in rotation speed deviation), the previous angular velocity value, or the deviation between the previous and current angular accelerations. Note that this conventional misfire determination method has difficulty detecting a temporary drop in angular acceleration when combustion slows down.

[0038] [2.Effects] (1) The misfire detection device 10 of this embodiment includes a calculation unit 11, a correction unit 12, and a determination unit 13. The calculation unit 11 calculates a deviation D by subtracting a first angular velocity Ne1, which is the crank angular velocity Ne when the crank angle θ is a first angle θ1 in the first half of the combustion stroke of the engine 1, from a second angular velocity Ne2, which is the crank angular velocity Ne when the crank angle θ is a second angle θ2 in the second half of the combustion stroke. The correction unit 12 calculates a corrected deviation C by correcting the deviation D based on an average engine angular velocity deviation A, which corresponds to the overall change trend of the crank angular velocity Ne within a predetermined crank angle range P2. The determination unit 13 determines whether the engine 1 is in a misfire state based on the corrected deviation C.

[0039] In this way, by calculating the corrected deviation C by correcting the deviation D based on the average engine angular velocity deviation A and determining whether the engine 1 is in a misfire state based on the corrected deviation C, it is possible to evaluate the misfire state while eliminating the influence of the overall change trend in the crank angular velocity Ne. For example, as shown in FIG. 2, if the crank angular velocity Ne is decreasing overall over a crank angle width greater than the cycle in which the combustion stroke of the engine 1 is repeated (a crank angle cycle of 180° in FIG. 2) due to deceleration of the vehicle or the like, the value of the deviation D will be small (a negative value in FIG. 2), which will likely lead to an erroneous determination that the engine 1 is in a misfire state. Conversely, if the crank angular velocity Ne is increasing overall, it will likely lead to an erroneous determination that the engine 1 is not in a misfire state.

[0040] On the other hand, in this embodiment, an average engine angular velocity deviation A (a negative value in FIG. 2 ) corresponding to the overall change trend of the crank angular velocity Ne, which is decreasing overall, is calculated, and deviation D is corrected based on the average engine angular velocity deviation A to calculate a corrected deviation C. The corrected deviation C is a value slightly larger than deviation D (a negative value with an absolute value smaller than deviation D in FIG. 2 ), which makes it easier to avoid an erroneous determination that the engine 1 is in a misfire state. Similarly, when the crank angular velocity Ne is increasing overall, the corrected deviation C is a value slightly smaller than deviation D, which makes it easier to avoid an erroneous determination that the engine 1 is not in a misfire state. Therefore, the accuracy of determining a misfire state can be improved with a simple configuration.

[0041] (2) In this embodiment, the determination unit 13 determines that the engine 1 is in a misfire state when the corrected deviation C is equal to or smaller than the first determination value C1. In this way, the misfire state of the engine 1 can be determined with high accuracy using a simple configuration that simply compares the magnitude relationship between the corrected deviation C and the first determination value C1. Furthermore, in this embodiment, the determination unit 13 determines that the misfire state is "semi-misfire" when the corrected deviation C is smaller than the first determination value C1 and exceeds a second determination value C2 that is smaller than the first determination value C1, and determines that the misfire state is "misfire" when the corrected deviation C is equal to or smaller than the second determination value C2. In this way, by providing two determination values, the degree of the misfire state can be determined in stages.

[0042] (3) In this embodiment, the predetermined crank angle range P2 is set to be at least wider than the determination angle range P1 between the first angle θ1 and the second angle θ2. This allows the overall change trend of the crank angular velocity Ne to be accurately grasped, thereby improving the accuracy of calculating the average engine angular velocity deviation A. This increases the accuracy of correcting the deviation D and improves the accuracy of determining whether the engine 1 is in a misfire state.

[0043] (4) As shown in Fig. 2, in this embodiment, the end point of the predetermined crank angle range P2 is the second angle θ2, and the start point of the predetermined crank angle range P2 is a third angle θ3 that precedes the second angle θ2 by the amount of the predetermined crank angle range P2. Furthermore, when the crank angle θ is the third angle θ3, the crank angular velocity Ne is a third angular velocity Ne3, and the average engine angular velocity deviation A is a value obtained by subtracting the third angular velocity Ne3 from the second angular velocity Ne2.

[0044] In other words, the end point of the predetermined crank angle range P2 is set to coincide with the end point of the judgment angle range P1. This setting makes it possible to determine the overall change trend of the crank angular velocity Ne (average engine angular velocity deviation A) at the time when the deviation D within the judgment angle range P1 is determined, thereby improving the accuracy of calculating the corrected deviation C. This increases the accuracy of correcting the deviation D, thereby improving the accuracy of determining whether the engine 1 is experiencing a misfire. Furthermore, the overall change trend of the crank angular velocity Ne can be grasped with the simple configuration of calculating the difference between the two crank angular velocities Ne. This reduces the workload associated with calculating the average engine angular velocity deviation A and determining whether the engine 1 is experiencing a misfire.

[0045] (5) In this embodiment, the correction unit 12 calculates a gradient influence value B, which is the product of the ratio of the determination angle width P1 between the first angle θ1 and the second angle θ2 with respect to the predetermined crank angle range P2 and the average engine angular velocity deviation A, and calculates a corrected deviation C by subtracting the gradient influence value B from the deviation D. This calculation makes it possible to accurately determine the value of the corrected deviation C, from which the influence of the overall change trend of the crank angular velocity Ne has been subtracted. Therefore, the accuracy of correcting the deviation D can be improved, and the accuracy of determining whether the engine 1 is in a misfire state can be improved.

[0046] (6) Generally, when a vehicle decelerates, the crank angular velocity Ne (engine rotation speed) may gradually decrease, which may result in an erroneous determination that the engine 1 is in a misfire state. On the other hand, the correction unit 12 of this embodiment can calculate the correction deviation C when the vehicle equipped with the engine 1 is decelerating for a predetermined time or longer. In this way, by determining whether a misfire state is present using the correction deviation C when deceleration continues for a predetermined time or longer, it is possible to avoid erroneous determinations due to deceleration and improve the accuracy of determining whether the engine 1 is in a misfire state.

[0047] If the correction deviation C reflects the degree of deceleration during momentary deceleration (less than a predetermined time), the decrease in crank angular velocity Ne due to misfire will be reflected. Therefore, it is preferable to determine the misfire state using the correction deviation C when deceleration continues for a predetermined time or longer, so that the decrease in crank angular velocity Ne due to misfire is less likely to be reflected. Furthermore, because misfire is less likely to occur during acceleration, it is sufficient to perform misfire determination using the correction deviation C only during deceleration, and perform conventional misfire determination during acceleration.

[0048] (7) When temperature rise control of the catalytic converter 5 is being performed, combustion slows down, making misfire more likely to occur, and it is difficult to determine misfire using conventional misfire determination methods. On the other hand, the correction unit 12 of this embodiment can calculate the correction deviation C when temperature rise control is being performed on the catalytic converter 5 installed in the exhaust passage of the engine 1. In this way, if the correction deviation C is used to determine the misfire state when temperature rise control is being performed, erroneous determination can be avoided and the accuracy of determining the misfire state of the engine 1 can be improved.

[0049] [3. 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.

[0050] In the above embodiment, the condition for determining that the engine 1 is in a misfire state is that "the correction deviation C is equal to or less than the first determination value C1," but the specific condition is not limited to this. For example, the misfire state of the engine 1 may be determined by comparing the correction deviation C to which a predetermined offset value or drift value has been added or subtracted with the first determination value C1. By determining the misfire state of the engine 1 based on at least the correction deviation C, it is possible to prevent erroneous determinations of the misfire state, and to achieve the same functions and effects as the above embodiment.

[0051] In the above embodiment, the average engine angular velocity deviation A is calculated by subtracting the third angular velocity Ne3 at the start point (third angle θ3) of the predetermined crank angle range P2 from the second angular velocity Ne2 at the end point (second angle θ2) of the predetermined crank angle range P2. However, the specific method for calculating the average engine angular velocity deviation A is not limited to this. For example, a moving average value of the crank angular velocity Ne may be constantly calculated, and the increase or decrease in this moving average value within the predetermined crank angle range P2 may be calculated as the average engine angular velocity deviation A. By using at least a value that corresponds to the overall change trend of the crank angular velocity Ne (for example, a value such as the average engine angular velocity deviation A), it is possible to obtain the same functions and effects as the above embodiment and improve the accuracy of determining a misfire state.

[0052] [4. Notes] The following notes are provided regarding the above-described embodiments and modifications. [Appendix 1] a calculation unit (11) that calculates a deviation (D) obtained by subtracting a first angular velocity (Ne1), which is a crank angular velocity (Ne) when a crank angle (θ) is a first angle (θ1) in a first half of a combustion stroke of an engine (1), from a second angular velocity (Ne2), which is the crank angular velocity (Ne) when the crank angle (θ) is a second angle (θ2) in a second half of the combustion stroke; a correction unit (12) that calculates a corrected deviation (C) by correcting the deviation (D) based on an average engine angular velocity deviation (A) corresponding to a change tendency of the crank angular velocity (Ne) within a predetermined crank angle range (P2); a determination unit (13) that determines whether the engine (1) is in a misfire state based on the correction deviation (C); A misfire detection device (10) for an engine (1), comprising:

[0053] [Appendix 2] The determination unit (13) determines that the engine (1) is in a misfire state when the corrected deviation (C) is equal to or smaller than a first determination value (C1). 2. A misfire detection device (10) for an engine (1) according to claim 1.

[0054] [Appendix 3] The predetermined crank angle range (P2) is at least wider than the determination angle width (P1) between the first angle (θ1) and the second angle (θ2). 3. A misfire detection device (10) for an engine (1) according to claim 1 or 2.

[0055] [Appendix 4] the end point of the predetermined crank angle range (P2) is the second angle (θ2); a start point of the predetermined crank angle range (P2) is a third angle (θ3) that is the predetermined crank angle range (P2) before the second angle (θ2), When the crank angle (θ) is the third angle (θ3), the crank angular velocity (Ne) is a third angular velocity (Ne3), The average engine angular velocity deviation (A) is a value obtained by subtracting the third angular velocity (Ne3) from the second angular velocity (Ne2). 4. A misfire detection device (10) for an engine (1) according to any one of appendices 1 to 3.

[0056] [Appendix 5] The correction unit (12) calculates a gradient influence value (B) which is the product of the ratio of a judgment angle width (P1) between the first angle (θ1) and the second angle (θ2) with respect to the predetermined crank angle range (P2) and the average engine angular velocity deviation (A), and calculates the deviation (D) by subtracting the gradient influence value (B) from the deviation (D) as the corrected deviation (C). 5. A misfire detection device (10) for an engine (1) according to any one of appendices 1 to 4.

[0057] [Appendix 6] The correction unit (12) calculates the corrected deviation (C) when the vehicle equipped with the engine (1) is decelerating for a predetermined time or more. 6. A misfire detection device (10) for an engine (1) according to any one of appendices 1 to 5.

[0058] [Appendix 7] The correction unit (12) calculates the correction deviation (C) when temperature increase control of a catalytic converter (5) disposed in an exhaust passage of the engine (1) is being performed. 7. A misfire detection device (10) for an engine (1) according to any one of appendices 1 to 6. [Industrial Applicability]

[0059] 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]

[0060] 1 engine 2 fuel injection valves 3 Spark plugs 4 Crank angle sensor 5. Catalytic converter 6 Catalyst temperature sensor 7. Catalytic control device 8 Accelerator opening sensor 9 Vehicle speed sensor 10 Misfire detection device 11 Calculation section 12 Correction unit 13 Judgment Department 14. Alarm device A Mean Engine Angular Velocity Deviation B Gradient influence value C Correction deviation D deviation P1 judgment angle width P2 specified crank angle range θ crank angle θ1 first angle θ2 second angle θ3 third angle Ne crank angular velocity Ne1 first angular velocity Ne2 second angular velocity Ne3 triangular velocity C1 first judgment value C2 Second judgment value

Claims

1. a calculation unit that calculates a deviation by subtracting a first angular velocity, which is a crank angular velocity when the crank angle is a first angle in a first half of a combustion stroke of the engine, from a second angular velocity, which is the crank angular velocity when the crank angle is a second angle in a second half of the combustion stroke; a correction unit that calculates a corrected deviation by correcting the deviation based on an average engine angular velocity deviation corresponding to a change tendency of the crank angular velocity within a predetermined crank angle range; a determination unit that determines a misfire state of the engine based on the correction deviation; Equipped with The correction deviation corresponds to a change trend of the crank angular velocity, and is calculated so as to avoid an erroneous determination of a misfire state caused by a decrease in the change trend of the crank angular velocity when the change trend of the crank angular velocity is a decrease. An engine misfire detection device comprising:

2. The determination unit determines that the engine is in a misfire state when the corrected deviation is equal to or smaller than a first determination value.

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

3. The predetermined crank angle range is at least wider than the determination angle width between the first angle and the second angle.

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

4. an end point of the predetermined crank angle range is the second angle, a start point of the predetermined crank angle range is a third angle that is an angle that is earlier than the second angle by the predetermined crank angle range, the crank angular velocity when the crank angle is the third angle is a third angular velocity, The average engine angular velocity deviation is a value obtained by subtracting the third angular velocity from the second angular velocity.

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

5. The correction unit calculates a gradient influence value, which is a product of the ratio of a judgment angle width between the first angle and the second angle with respect to the predetermined crank angle range and the average engine angular velocity deviation, and calculates the corrected deviation by subtracting the gradient influence value from the deviation.

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

6. The correction unit calculates the corrected deviation when a vehicle equipped with the engine is decelerating for a predetermined period of time or more.

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

7. The correction unit calculates the correction deviation when temperature increase control of a catalytic converter disposed in an exhaust passage of the engine is being performed.

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

Images