Crank angular velocity measuring device and misfire determination device

Abstract

A crank angle velocity measuring device and a misfire determination device are provided, which measure the crank angle velocity using the output of a magnetic sensor of an AC rotating motor that rotates synchronously with the crankshaft of an engine. The AC rotating motor has a rotor formed by circumferentially arranging permanent magnets of S poles and N poles at equal intervals from each other, and first, second, and third magnetic sensors that detect the magnetization boundaries of the permanent magnets, and rotates synchronously with the crankshaft. A timing unit counts a first elapsed time from when the first magnetic sensor detects the magnetization boundary to when the second magnetic sensor detects the magnetization boundary, a second elapsed time from when the second magnetic sensor detects the magnetization boundary to when the third magnetic sensor detects the magnetization boundary, and a third elapsed time from when the third magnetic sensor detects the magnetization boundary to when the first magnetic sensor detects the magnetization boundary. A moving average calculation unit calculates the crank angle velocity based on the moving average of the first, second, and third elapsed times.

Description

Technical Field

[0001] The present invention relates to a crank angle velocity measuring device and a misfire determining device for an internal combustion engine vehicle, and in particular to a crank angle velocity measuring device and a misfire determining device for measuring the crank angle velocity using the output of a magnetic sensor of an AC rotating electric machine that rotates synchronously with the crankshaft of the engine. Background Art

[0002] In a four-wheel vehicle, a technique for determining engine misfire based on a crank angular velocity measured from a time interval between crankshaft pulses (inter-crankshaft pulse time) is known. Here, the misfire determination parameter (misfire parameter) includes the inter-tooth error of the crankshaft pulse generator rotor, so the inter-tooth error of the crankshaft pulse generator rotor needs to be removed for accurate misfire determination.

[0003] Patent document 1 discloses a method for removing the inter-tooth error of a crankshaft pulse generator rotor, which focuses on the fact that, in an equal-interval explosion-type engine, the crank angular velocity component caused by the inertia torque changes within the pulse generation period of TDC. Patent document 2 discloses a technique for obtaining a relative value of the crank angular velocity and removing the inter-tooth error of a crankshaft pulse generator rotor based on the cumulative value of the relative value.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: (Japanese) Patent Publication No. 2008-111354

[0007] Patent Document 2: WO2018-179340

[0008] In recent years, from the perspective of improving repairability and environmental protection, the use of misfire determination technology in motorcycles has been discussed. The method for eliminating the tooth error of a crankshaft pulse generator rotor in Patent Document 1 is based on the premise that the engine belongs to an equal-interval explosion-ignition engine and is equipped with a crankshaft pulse generator rotor system. It is not applicable to vehicles that do not use a crankshaft pulse generator rotor system or single-cylinder engines and unequal-interval explosion-ignition multi-cylinder engines.

[0009] In Patent Document 2, regardless of whether the engine is an equal-interval explosion type or an unequal-interval explosion type, a fixed error component such as the tooth-to-tooth error of the crankshaft pulse generator rotor can be removed. On the other hand, the crank angular velocity can also be measured by the following method: without using the crankshaft pulse generator rotor, for example, by using a magnetic sensor to detect the rotation speed of a magnet that rotates synchronously with the crankshaft provided in the ACG starter motor.

[0010] Here, due to environmental changes such as temperature, humidity, and air pressure and changes over time, the function and sensitivity of the magnetic sensor will change and deteriorate. Therefore, in the measurement using the magnetic sensor, in addition to the fixed error component depending on the installation accuracy, the variable error component depending on the environmental changes and changes over time must also be considered. However, in Patent Document 2, although the fixed error component can be eliminated, the variable error component cannot be eliminated. Summary of the invention

[0011] The object of the present invention is to solve the above-mentioned technical problems and to provide a crank angle velocity measuring device and a misfire determination device, which are not equipped with a crankshaft pulse generator rotor system, and can correctly measure the crank angle velocity by eliminating the error components included in the measurement error of the crank angle velocity that vary due to environmental changes and aging changes, and can correctly perform misfire determination based on the measurement result of the crank angle velocity.

[0012] In order to achieve the above-mentioned object, the crank angular velocity measuring device of the present invention is characterized by having the following structures (1) and (2).

[0013] (1) An AC rotating electric machine having a rotor in which permanent magnets with S poles and N poles are arranged in a circumferential shape at equal intervals from each other, and a first magnetic sensor, a second magnetic sensor, and a third magnetic sensor for detecting magnetization boundaries of the permanent magnets, and rotating synchronously with a crankshaft; a timing unit for timing a first elapsed time from when the first magnetic sensor detects the magnetization boundary to when the second magnetic sensor detects the magnetization boundary, a second elapsed time from when the second magnetic sensor detects the magnetization boundary to when the third magnetic sensor detects the magnetization boundary, and a third elapsed time from when the third magnetic sensor detects the magnetization boundary to when the first magnetic sensor detects the magnetization boundary; and a unit for calculating a crank angular velocity based on a moving average of the first elapsed time, the second elapsed time, and the third elapsed time.

[0014] (2) The unit for calculating the crank angular velocity repeatedly calculates an average value of a first elapsed time from when the first magnetic sensor detects the nth magnetization boundary to when the second magnetic sensor detects the nth magnetization boundary, a second elapsed time from when the second magnetic sensor detects the nth magnetization boundary to when the third magnetic sensor detects the nth magnetization boundary, and a third elapsed time from when the third magnetic sensor detects the nth magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary; and a third elapsed time from when the second magnetic sensor detects the nth magnetization boundary to when the third magnetic sensor detects the nth magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary. a third elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary, and an average value of the first elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary; a third elapsed time from when the third magnetic sensor detects the n+1th magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary, the first elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary, and an average value of the second elapsed time from when the second magnetic sensor detects the n+1th magnetization boundary to when the third magnetic sensor detects the n+1th magnetization boundary.

[0015] In order to achieve the above-mentioned object, the misfire determination device of the present invention is characterized by having the following structures (3) and (4).

[0016] (3) An AC rotating electric machine having a rotor in which permanent magnets with S poles and N poles are arranged in a circumferential shape at equal intervals from each other, and a first magnetic sensor, a second magnetic sensor, and a third magnetic sensor for detecting magnetization boundaries of the permanent magnets, and rotating synchronously with a crankshaft; a timing unit for timing a first elapsed time from when the first magnetic sensor detects the magnetization boundary to when the second magnetic sensor detects the magnetization boundary, a second elapsed time from when the second magnetic sensor detects the magnetization boundary to when the third magnetic sensor detects the magnetization boundary, and a third elapsed time from when the third magnetic sensor detects the magnetization boundary to when the first magnetic sensor detects the magnetization boundary; a unit for calculating a crank angular velocity based on a moving average of the first elapsed time, the second elapsed time, and the third elapsed time; and a misfire determination unit for determining engine misfire based on the calculation result of the crank angular velocity.

[0017] (4) The unit for calculating the crank angular velocity repeatedly calculates an average value of a first elapsed time from when the first magnetic sensor detects the nth magnetization boundary to when the second magnetic sensor detects the nth magnetization boundary, a second elapsed time from when the second magnetic sensor detects the nth magnetization boundary to when the third magnetic sensor detects the nth magnetization boundary, and a third elapsed time from when the third magnetic sensor detects the nth magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary; and a third elapsed time from when the second magnetic sensor detects the nth magnetization boundary to when the third magnetic sensor detects the nth magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary. a third elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary, and an average value of the first elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary; a third elapsed time from when the third magnetic sensor detects the n+1th magnetization boundary to when the first magnetic sensor detects the n+1th magnetization boundary, the first elapsed time from when the first magnetic sensor detects the n+1th magnetization boundary to when the second magnetic sensor detects the n+1th magnetization boundary, and an average value of the second elapsed time from when the second magnetic sensor detects the n+1th magnetization boundary to when the third magnetic sensor detects the n+1th magnetization boundary.

[0018] Effects of the Invention

[0019] (1) According to the crank angular velocity measuring device of the present invention, when the crank angular velocity is measured using the output of a magnetic sensor that detects the UVW phase of an AC rotating motor that rotates synchronously with a crankshaft, even if an error occurs in the measured value of the crank angular velocity due to changes in the spacing and function of the magnetic sensors caused by environmental or time effects, the error can be offset according to the calculation process of the present invention and excluded from the crank angular velocity, thereby enabling accurate crank angular velocity measurement.

[0020] (2) According to the misfire determination device of the present invention, when misfire determination is performed based on the crank angle velocity measured using the output of the magnetic sensor that detects the UVW phase of the AC rotating electric machine that rotates synchronously with the crankshaft, even if an error occurs in the measured value of the crank angle velocity due to changes in the spacing and function of the magnetic sensors caused by the environment or the passage of time, the error can be offset according to the calculation process of the present invention and excluded from the crank angle velocity, thereby enabling accurate crank angle velocity measurement. As a result, a highly accurate misfire determination can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a functional block diagram showing the structure of a misfire determination device to which the present invention is applied.

[0022] Figure 2 This is a functional block diagram showing the structure of a crank angular velocity measuring unit to which the present invention is applied.

[0023] Figure 3 : is a timing chart showing the relationship between the crank angle and the output of each magnetic sensor.

[0024] Figure 4 This is a diagram for explaining the principle of canceling out errors in the mutual intervals between magnetic sensors.

[0025] Figure 5 : is a figure which shows the calculation method of the moving average value of the elapsed time Δt.

[0026] Figure 6 This is a diagram for explaining the function of the 720-degree filter processing unit.

[0027] Figure 7 (a) and (b) are diagrams for explaining the function of the relative angular velocity calculation unit.

[0028] Figure 8 (a) and (b) are diagrams for explaining the function of the cumulative angular velocity calculation unit.

[0029] Fig. 9 is an example diagram showing the calculation results of the inertia torque on a computer

[0030] Fig.10 : is a diagram showing an example of relative values ​​of the amount of change in crank angular velocity caused by inertia torque with respect to the compression upper limit point.

[0031] Fig.11 is an example diagram showing a suction torque component.

[0032] Fig.12 This is a diagram for explaining the function of the crank angular velocity measurement error removing unit.

[0033] Fig.13 (a) to (c) are diagrams showing an example (no misfire) of a misfire determination method in which a relative angular velocity is obtained from a crank angular velocity and an integrated value of the relative angular velocity is used as a misfire parameter.

[0034] Fig.14 (a) to (c) are diagrams showing an example (misfire) of a misfire determination method in which a relative angular velocity is obtained from a crank angular velocity and an integrated value of the relative angular velocity is used as a misfire parameter.

[0035] Description of Reference Numerals

[0036] 5: Crank angular velocity measuring unit;

[0037] 6: 720 degree filtration treatment unit;

[0038] 7: Relative angular velocity calculation unit;

[0039] 8: Cumulative angular velocity calculation unit;

[0040] 9: Inertia torque component removal unit;

[0041] 10: suction torque component removal unit;

[0042] 11: crank angular velocity measurement error component removal unit;

[0043] 12: Fire determination unit;

[0044] 100: Fire determination device. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, a misfire determination method using a crank angle velocity measured by a crank angle velocity measurement method of the present invention will be described in outline, and then embodiments thereof will be described in detail.

[0046] Fig.13 , 14 This is an example of a misfire determination method in which the relative angular velocity is obtained from the measured value of the crank angular velocity [each figure (a)], and the cumulative value (cumulative angular velocity) [each figure (c)] is obtained as a misfire parameter. Each figure (a) is a graph showing the crank angular velocity on the vertical axis with the crank angle at the compression upper limit point as the origin. The relative angular velocity of the crank angular velocity is calculated by subtracting the reference angular velocity detected near the compression upper limit point of each cylinder of the engine from the measured result of the crank angular velocity at each crank angle. Fig.13 Shows the normal combustion situation. Fig.14 There was a fire.

[0047] The relative angular velocity increases when combustion is normal in the combustion stroke after the upper limit point of engine compression, and decreases when misfire occurs [Figure (b)]. Therefore, the cumulative angular velocity obtained by integrating the relative angular velocity within a predetermined crank angle range is a positive value when combustion is normal, and a negative value when misfire occurs, and can be used as a parameter for determining a misfire cylinder.

[0048] However, the cumulative angular velocity includes, in addition to the combustion torque, angular velocity components that vary due to measurement errors of the crank angular velocity, noise caused by dynamic changes in the sensor gap, load torque, friction, inertia torque, and suction torque. Therefore, in order to accurately perform misfire determination, all of these varying components must be removed from the cumulative angular velocity.

[0049] Among these variable components, noise, load torque, friction, and inertia torque are removed by statistical processing, engine control, or computer calculation. Suction torque can be removed by the technology disclosed in Patent Document 2. In addition, among the crank acceleration measurement errors, fixed errors can be removed by the technology disclosed in Patent Document 2, but there is no effective method for removing errors that vary due to the environment and the passage of time.

[0050] Here, the so-called error due to the influence of the environment and the passage of time included in the measurement error of the crank angular velocity refers to errors caused by, for example, fluctuations in the temperature characteristics of the magnetic sensor, positional deviation of the magnetic sensor caused by deformation of the magnetic sensor holding component, and changes in the responsiveness of the magnetic sensor caused by time-dependent degradation.

[0051] Next, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 Here, a motorcycle equipped with a four-stroke single-cylinder engine E and an ACG starter motor (three-phase AC rotating electric machine) M is described as an example.

[0052] In the misfire determination device 100 , the crank angular velocity measuring unit 5 measures the angular velocity of the crankshaft of the engine E. Figure 2 1 is a functional block diagram showing a configuration involved in crank angle velocity measurement to which the present invention is applied. In the present embodiment, the crank angle velocity is measured based on the outer rotor angular velocity of the ACG starter motor M that rotates synchronously with the crankshaft of the engine E.

[0053] The ACG starter motor M includes: an outer rotor (omitted in the figure) formed by arranging the permanent magnets 60 of the S pole and the N pole in a circumferential shape at equal intervals from each other, and the first, second and third magnetic sensors 61 (61a, 61b, 61c) for detecting the magnetization boundaries of the permanent magnets 601. In the present embodiment, the magnetization boundary switching from the S pole to the N pole is detected, but the magnetization boundary switching from the N pole to the S pole can also be detected. The first, second and third magnetic sensors 61a, 61b, 61c also have the function of detecting the U phase, V phase and W phase of the ACG starter motor M.

[0054] The crank angle velocity measuring unit 5 includes the first, second and third timing units 51a, 51b, 51c and a moving average calculating unit 52, and calculates the crank angle velocity for misfire determination at each stage of engine control. The moving average calculating unit 52 removes noise caused by dynamic changes in the gap between the magnetic sensors 61 or between the permanent magnets 60, noise caused by dynamic changes in the sensor gap, and errors that change over time. Here, the so-called dynamic change in the sensor gap refers to the change in the interval between the magnetic sensor 61 and the permanent magnet 60 during operation (the change in the gap between the magnetic sensor 61 is a change over time caused by the deformation of the sensor holding member due to heat).

[0055] Figure 3 1 is a timing chart showing the relationship between the crank angle of the engine E and the output signals of the magnetic sensors 61 .

[0056] The first timing unit 51a measures a first elapsed time Δt1 from when the first magnetic sensor 61a detects the nth magnetization boundary Bn to when the second magnetic sensor 61b detects the nth magnetization boundary. The second timing unit 51b measures a second elapsed time Δt2 from when the second magnetic sensor 61b detects the magnetization boundary Bn to when the third magnetic sensor 61c detects the magnetization boundary Bn. The third timing unit 51c measures a third elapsed time Δt3 from when the third magnetic sensor 61c detects the magnetization boundary Bn to when the first magnetic sensor 61a detects the next (n+1th) magnetization boundary Bn+1.

[0057] The moving average calculation unit 52 calculates the moving average of three consecutive elapsed times Δt1, Δt2, and Δt3. Specifically, after obtaining the first elapsed time Δt1, the second elapsed time Δt2, and the third elapsed time Δt3, the moving average thereof is calculated as (Δt1+Δt2+Δt3) / 3.

[0058] Then, after timing the second first elapsed time Δt1_2 from when the first magnetic sensor 61a detects the magnetization boundary Bn+1 to when the second magnetic sensor 61b detects the magnetization boundary Bn+1, the moving average calculation unit 52 calculates the moving average value (Δt2+Δt3+Δt1_2) / 3 of the second elapsed time Δt2, the third elapsed time Δt3 and the second first elapsed time Δt1_2.

[0059] Then, after timing the second second elapsed time Δt2_2 from when the second magnetic sensor 61b detects the magnetization boundary Bn+1 to when the third magnetic sensor 61c detects the magnetization boundary Bn+1, the moving average calculation unit 52 calculates the moving average value (Δt3+Δt1_2+Δt2_2) / 3 of the third elapsed time Δt3, the second first elapsed time Δt1_2, and the second second elapsed time Δt2_2.

[0060] Here, if Figure 4 As shown, assuming that the interval between the magnetic sensors 61a / 61b, 61b / 61c is A, and the interval between the magnetization boundary Bn and the magnetization boundary Bn+1 (magnetization interval) is B (=2A+α) which is longer than 2A by α, then the measured distance of the first elapsed time Δt1 is A, the measured distance of the second elapsed time Δt2 is A, and the measured distance of the third elapsed time Δt3 is B-2A.

[0061] Furthermore, in the present embodiment, the distance L to be measured for the crank angular velocity is the sum of the measured distances of the first, second, and third elapsed times Δt1, Δt2, and Δt3, and therefore A+A+(B-2A)=B and is not related to A. In addition, the error of the magnetization interval B is fixed and there is no need to consider environmental changes or aging, and therefore it can be corrected using the method of Patent Document 2.

[0062] Therefore, even if the intervals between the magnetic sensors 61a / 61b, 61b / 61c include errors Δd1 and Δd2 due to manufacturing errors such as processing accuracy and assembly accuracy and errors due to environmental changes and time effects in addition to the designed interval A, the errors can be calculated as follows: Figure 5 As shown, the crank angular velocity ω is measured independently of the crank angle without being affected by the error component included in the output of each magnetic sensor 61 .

[0063] Back to Figure 1 The 720-degree filtering unit 6 takes the calculation result (moving average) of the crank angular velocity ω measured as described above as an object, eliminates the linear variation within one stroke cycle, and extracts the variation component of a relatively long cycle. In this way, the angular velocity variation component caused by the load torque applied from the tires or auxiliary machines of the engine-driven vehicle or the friction of the sliding parts of the engine can be removed. Figure 6 An example of using 720-degree filtering in a stroke in which combustion torque is generated but deceleration is caused by load torque is shown.

[0064] like Figure 7 As shown, the relative angular velocity calculation unit 7 uses the crank angular velocity ω measured near the upper compression limit point (TDC: crank angle 0 degrees) as the reference angular velocity ω1ref [same as Figure (a)], and calculates the difference between the angular velocity ω1_i measured at each crank angle i in the crank angle range from the TDC to 180 degrees and the reference angular velocity ω1ref as the relative angular velocity ωω1_i (=ω1_i-ω1ref) [same as Figure (b)].

[0065] like Figure 8As shown, the cumulative angular velocity calculation unit 8 accumulates the relative angular velocity ωω1_i within a crank angle range of 180 degrees to calculate a cumulative angular velocity Σωω1_i.

[0066] The inertia torque component removing unit 9 removes the inertia torque component from the cumulative angular velocity Σωω1_i to calculate the removed cumulative angular velocity Σωω1'_i. The inertia torque component can be calculated on a computer using the method disclosed in Patent Document 2, for example. The inertia torque Tq of a single-cylinder engine is, for example, Fig. 9 As shown in , the relative value dω' of the crank angular velocity change dω caused by the inertia torque based on the value of the upper compression limit point is as follows Fig.10 shown.

[0067] In this embodiment, the relative value dω' obtained from the unit engine speed is subjected to the same moving average calculation as the moving average calculation unit 52, and the value accumulated in the same interval as the cumulative angular velocity calculation unit 8 is calculated and set in the ECU. By multiplying this value by the engine speed, the inertia torque component at any engine speed can be calculated. In addition, using this value, the accumulated angular velocity Σωω1'_i after removal can be calculated.

[0068] The suction torque component removing unit 10 calculates the removed cumulative angular velocity Σωω1'_i by removing the crank angular velocity component caused by the torque generated by the pumping action of the engine E. The above-mentioned error removal can be implemented by setting the ECU to obtain the suction torque component using the method disclosed in Patent Document 2 (a method of measuring the cumulative angular velocity in a fuel supply cut-off state in a standard vehicle without error and removing the inertia torque).

[0069] The suction torque component depends on the engine speed and the intake manifold pressure. The suction torque component of a single-cylinder engine is, for example, Fig.11 As shown in , it is obtained in the form of a line map based on the engine speed and the intake manifold pressure. In this embodiment, the line map data is set in the ECU and used for correction of the misfire parameter.

[0070] The crank angle velocity measurement error component removal unit 11 removes the cumulative angular velocity error caused by the inter-tooth error of the pulse generator rotor and the magnetization position deviation in this embodiment. The above error removal is implemented by using the inter-tooth error removal method disclosed in Patent Document 2 (the inertia torque component and the suction torque component set in advance in the ECU are subtracted from the cumulative angular velocity calculated in the fuel supply cut-off state, and the result is divided by the reference angular velocity ωref1, thereby calculating the coefficient Kpul1 for calculating the crank angle velocity measurement error caused by the inter-tooth error at a unit speed, and after storing the coefficient in the ECU, the error component at any engine speed is obtained by multiplying the reference angular velocity ωref1, and the component is removed from the cumulative angular velocity).

[0071] Fig.12 An example is shown in which the inertia torque component (2) and the suction torque component (3) are removed from the integrated value (1) of the relative angular velocity to extract the crank angular velocity measurement error component.

[0072] In the present embodiment, a value obtained by removing the crank angular velocity measurement error component from the removed cumulative angular velocity Σωω1′_i is used as a misfire parameter. The misfire determination unit 12 determines the presence or absence of misfire based on the misfire parameter.

[0073] According to the present embodiment, when a misfire determination is performed based on the crank angular velocity measured using the output of a magnetic sensor that detects the UVW phase of an AC rotating electric machine that rotates synchronously with the crankshaft, even if an error occurs in the measured value of the crank angular velocity due to changes in the spacing and functions of the magnetic sensors caused by the environment or time, the error can be offset according to the calculation process of the present invention and excluded from the crank angular velocity, thereby enabling accurate crank angular velocity measurement. As a result, a highly accurate misfire determination can be performed.

[0074] In the above embodiment, the application to a single-cylinder engine is described as an example, but the present invention is not limited thereto and can also be applied to a multi-cylinder engine in the same manner. In this case, it does not matter whether it is an equal-interval explosion-type engine or an unequal-interval explosion-type engine.

Claims

1. A crank angle velocity measuring device for measuring the crank angle velocity of an engine (E), characterized in that: have: An AC rotating motor (M) comprising a rotor having permanent magnets (60) of S poles and N poles arranged circumferentially at equal intervals from each other, and a first magnetic sensor (61a), a second magnetic sensor (61b) and a third magnetic sensor (61c) for detecting magnetization boundaries of the permanent magnets, and rotating synchronously with a crankshaft; a timing unit (51a) for timing a first elapsed time from when the first magnetic sensor (61a) detects a magnetization boundary to when the second magnetic sensor (61b) detects a magnetization boundary, a second elapsed time from when the second magnetic sensor (61b) detects a magnetization boundary to when the third magnetic sensor (61c) detects a magnetization boundary, and a third elapsed time from when the third magnetic sensor (61c) detects a magnetization boundary to when the first magnetic sensor (61a) detects a magnetization boundary; a moving average calculation unit (52) for calculating a crank angular velocity based on a moving average of the first elapsed time, the second elapsed time, and the third elapsed time; Assuming that the interval of the magnetization boundaries is A, and the interval between the first magnetic sensor (61a) and the third magnetic sensor (61c) is B which is longer than 2A by α, then the measuring distance of the first elapsed time is A, the measuring distance of the second elapsed time is A, and the measuring distance of the third elapsed time is B-2A.

2. The crank angular velocity measuring device according to claim 1, wherein: The timing unit times a first elapsed time from when the first magnetic sensor (61a) detects the nth magnetization boundary to when the second magnetic sensor (61b) detects the nth magnetization boundary, a second elapsed time from when the second magnetic sensor (61b) detects the nth magnetization boundary to when the third magnetic sensor (61c) detects the nth magnetization boundary, and a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary.

3. The crank angular velocity measuring device according to claim 1 or 2, characterized in that: The timing unit times a second elapsed time from when the second magnetic sensor (61b) detects the nth magnetization boundary to when the third magnetic sensor (61c) detects the nth magnetization boundary, a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary, and a first elapsed time from when the first magnetic sensor (61a) detects the n+1th magnetization boundary to when the second magnetic sensor (61b) detects the n+1th magnetization boundary.

4. The crank angular velocity measuring device according to claim 1 or 2, characterized in that: The timing unit times a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary, a first elapsed time from when the first magnetic sensor (61a) detects the n+1th magnetization boundary to when the second magnetic sensor (61b) detects the n+1th magnetization boundary, and a second elapsed time from when the second magnetic sensor (61b) detects the n+1th magnetization boundary to when the third magnetic sensor (61c) detects the n+1th magnetization boundary.

5. A misfire determination device for determining misfire based on the crank angular velocity of an engine (E), characterized in that: have: An AC rotating motor (M) comprising a rotor having permanent magnets (60) of S poles and N poles arranged circumferentially at equal intervals from each other, and a first magnetic sensor (61a), a second magnetic sensor (61b) and a third magnetic sensor (61c) for detecting magnetization boundaries of the permanent magnets, and rotating synchronously with a crankshaft; a timing unit (51a) for timing a first elapsed time from when the first magnetic sensor (61a) detects a magnetization boundary to when the second magnetic sensor (61b) detects a magnetization boundary, a second elapsed time from when the second magnetic sensor (61b) detects a magnetization boundary to when the third magnetic sensor (61c) detects a magnetization boundary, and a third elapsed time from when the third magnetic sensor (61c) detects a magnetization boundary to when the first magnetic sensor (61a) detects a magnetization boundary; a moving average calculation unit (52) for calculating a crank angular velocity based on a moving average of the first elapsed time, the second elapsed time, and the third elapsed time; a misfire determination unit (10a) for determining engine misfire based on the calculation result of the crank angular velocity; Assuming that the interval of the magnetization boundaries is A, and the interval between the first magnetic sensor (61a) and the third magnetic sensor (61c) is B which is longer than 2A by α, then the measuring distance of the first elapsed time is A, the measuring distance of the second elapsed time is A, and the measuring distance of the third elapsed time is B-2A.

6. The misfire determination device according to claim 5, characterized in that: The timing unit times a first elapsed time from when the first magnetic sensor (61a) detects the nth magnetization boundary to when the second magnetic sensor (61b) detects the nth magnetization boundary, a second elapsed time from when the second magnetic sensor (61b) detects the nth magnetization boundary to when the third magnetic sensor (61c) detects the nth magnetization boundary, and a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary.

7. The misfire determination device according to claim 5 or 6, characterized in that: The timing unit times a second elapsed time from when the second magnetic sensor (61b) detects the nth magnetization boundary to when the third magnetic sensor (61c) detects the nth magnetization boundary, a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary, and a first elapsed time from when the first magnetic sensor (61a) detects the n+1th magnetization boundary to when the second magnetic sensor (61b) detects the n+1th magnetization boundary.

8. The misfire determination device according to claim 5 or 6, characterized in that: The timing unit times a third elapsed time from when the third magnetic sensor (61c) detects the nth magnetization boundary to when the first magnetic sensor (61a) detects the n+1th magnetization boundary, a first elapsed time from when the first magnetic sensor (61a) detects the n+1th magnetization boundary to when the second magnetic sensor (61b) detects the n+1th magnetization boundary, and a second elapsed time from when the second magnetic sensor (61b) detects the n+1th magnetization boundary to when the third magnetic sensor (61c) detects the n+1th magnetization boundary.

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