Engine Control Unit

Abstract

To provide an engine control device which controls an engine using a crank angle sensor so as to prevent a reduction in accuracy of determining a tooth removed position on a crank signal plate even when output frequency of a crank signal fluctuates.SOLUTION: An engine control module 270: reads output signals of a crank angle sensor 240 which detects tooth sections on a crank signal plate 230 with a tooth removed section formed thereon and outputs pulsed crank signals; and determines a tooth removed position defined by the tooth removed section on the crank signal plate 230 on the basis of a frequency ratio of output intervals of the crank signals. In this instance, the engine control module 270 changes methods for calculating the frequency ratios between a first state where the output intervals of the crank signals get gradually extended and a second state where the output intervals of the crank signals get gradually reduced.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an engine control device that electronically controls an engine. [Background technology]

[0002] Electronically controlled engines use a crank angle sensor that detects the teeth of a crank signal plate attached to the end of the crankshaft and outputs a pulse-like crank signal. A portion of the teeth of the crank signal plate is missing, forming a missing tooth portion that defines the reference angle for a crank angle of 360°. As described in JP 2010-242715 A (Patent Document 1), a technique for determining the position of a missing tooth is proposed in which the period of the crank signal output from the crank angle sensor is successively measured, and when the "current period / previous period" exceeds a predetermined threshold value, it is determined that the position of the missing tooth has occurred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-242715 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an engine, the rotation speed of the crankshaft fluctuates. For example, before the top dead center of each cylinder, the rotation speed of the crankshaft decreases due to compression, while after the top dead center of each cylinder, the rotation speed of the crankshaft increases due to combustion. When the rotation speed of the crankshaft increases, the output interval of the crank signal gradually becomes shorter. For this reason, even if an attempt is made to determine the position of a missing tooth on the crank signal plate when the rotation speed of the crankshaft is increasing, the period ratio of the crank signal becomes smaller than that in the steady state and does not exceed the predetermined threshold, which may reduce the accuracy of determining the position of the missing tooth.

[0005] Therefore, an object of the present invention is to provide an engine control device that can suppress a decrease in accuracy in determining the position of a missing tooth on a crank signal plate even if the output period of the crank signal fluctuates. [Means for solving the problem]

[0006] The engine control device reads the output signal of the crank angle sensor which detects the tooth portion of the crank signal plate on which the tooth chipping portion is formed and outputs a pulse-like crank signal, and determines the tooth chipping position defined by the tooth chipping portion of the crank signal plate from the cycle ratio of the output interval of the crank signal. At this time, the engine control device determines the first state in which the output interval of the crank signal is gradually increased. Now, calculate the cycle ratio by dividing the current cycle of the crank signal output interval by the previous cycle. , the second state in which the crank signal output interval gradually becomes shorter Now, calculate the cycle ratio by dividing the previous cycle of the crank signal by the current cycle. . Effect of the Invention

[0007] According to the present invention, in an engine control device that controls an engine using a crank angle sensor, even if the output period of the crank signal varies, it is possible to suppress a decrease in the accuracy of determining the position of a missing tooth on a crank signal plate. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of a control system for a four-stroke engine. [Diagram 2] FIG. 4 is a plan view showing an example of a crank signal plate. [Diagram 3] FIG. 4 is a plan view showing an example of a cam signal plate. [Figure 4] FIG. 2 is an explanatory diagram of various parameters used in engine control. [Diagram 5] FIG. 2 is an explanatory diagram of fluctuations in rotation speed that occur in an Otto cycle engine. [Figure 6] 5 is a graph showing a change in the output period of a crank signal caused by fluctuations in the rotation speed of a crankshaft, and a change in a period ratio which is a parameter for determining a position of a missing tooth; FIG. [Figure 7] 13 is a flowchart showing an example of a missing tooth position determination process. [Figure 8] 13 is a flowchart illustrating an example of a changeover switch setting process. [Figure 9] 11A and 11B are diagrams illustrating problems that occur when a method for calculating a period ratio is switched. [Figure 10] FIG. 11 is an explanatory diagram of a method for solving a problem caused by switching the method of calculating the period ratio. [Figure 11] 11 is an explanatory diagram of a method for switching a calculation method of a period ratio during rotation of a crankshaft. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of a control system for a four-stroke engine mounted on a vehicle such as an automobile.

[0010] The engine 100 includes a cylinder block 110, a piston 120, a crankshaft 130, a connecting rod 140, and a cylinder head 150. A cylinder bore 110A is formed in the cylinder block 110, into which the piston 120 is inserted so as to be capable of reciprocating. A crankshaft 130 is disposed in a lower portion of the cylinder block 110 via a bearing (not shown) so as to be rotatable relative to the cylinder block 110. The piston 120 is coupled to the crankshaft 130 via the connecting rod 140 so as to be rotatable relative to the crankshaft 130.

[0011] The cylinder head 150 is formed with an intake port 150A for introducing intake air and an exhaust port 150B for discharging exhaust gas. The cylinder head 150 is fastened to the upper surface of the cylinder block 110, so that an area defined by the cylinder bore 110A of the cylinder block 110, the crown surface of the piston 120, and the lower surface of the cylinder head 150 functions as a combustion chamber 160. An intake valve 180 that is driven to open and close by an intake camshaft 170 is disposed at an open end of the intake port 150A facing the combustion chamber 160. An exhaust valve 200 that is driven to open and close by an exhaust camshaft 190 is disposed at an open end of the exhaust port 150B facing the combustion chamber 160.

[0012] An electromagnetic fuel injection valve 210 that injects fuel into the combustion chamber 160 and an ignition plug 220 that ignites a mixture of fuel and intake air are attached to predetermined positions of the cylinder head 150 facing the combustion chamber 160. Note that the fuel injection valve 210 is not limited to a configuration that directly injects fuel into the combustion chamber 160, but may be a configuration that injects fuel into the intake port 150A, or a configuration that has both.

[0013] A crank signal plate 230 is attached to the end of the crankshaft 130. As shown in FIG. 2, the crank signal plate 230 is a detectable member in which a disk-shaped plate portion 230A and a plurality of teeth portions 230B extending radially outward from the outer circumferential end of the plate portion 230A are integrated. In addition, the crank signal plate 230 is formed with a tooth-missing portion 230C that defines the angle reference at a crank angle of 360° by missing a part of the tooth portion 230B. Here, in the example of the crank signal plate 230 shown in FIG. 2, the tooth-missing portion 230C is formed by missing two tooth portions 230B, but the tooth-missing portion 230C may be formed by missing any number of tooth portions 230B.

[0014] In the case of a four-cylinder engine, the crank signal plate 230 has, for example, 34 teeth 230B with a predetermined angle of 10°, and a tooth-missing portion 230C spanning 30° in which two teeth 230B are missing. The crank signal plate 230 may have two or more tooth-missing portions 230C.

[0015] A crank angle sensor 240 is attached to the lower part of the cylinder block 110 at a predetermined position facing the outer circumferential end of the crank signal plate 230. The crank angle sensor 240 detects the teeth 230B of the crank signal plate 230 and outputs a pulse-like crank signal CRS.

[0016] A cam signal plate 250 is attached to the end of the intake camshaft 170. As shown in Fig. 3, the cam signal plate 250 is a detectable member that is an integrated member of a disk-shaped plate portion 250A and an arc-shaped extension portion 250B that extends radially outward from a part of the outer circumferential end of the plate portion 250A.

[0017] A cam angle sensor 260 is attached to a predetermined position on the upper part of the cylinder head 150 facing the outer circumferential end of the cam signal plate 250, which detects the extension portion 250B of the cam signal plate 250 and outputs a rectangular cam signal CMS. The extension portion 250B of the cam signal plate 250 is provided so that, for example, at two tooth missing positions where the crank angle sensor 240 detects the tooth missing portion 230C of the crank signal plate 230 during two rotations of the crankshaft 130, the extension portion 250B of the cam signal plate 250 outputs a LOW signal at the tooth missing position in the first rotation and a HIGH signal at the tooth missing position in the second rotation. Therefore, the cam angle sensor 260 outputs a cam signal CMS of different levels depending on whether or not the extension portion 250B of the cam signal plate 250 is detected.

[0018] Therefore, by monitoring such a cam signal CMS, it is possible to distinguish whether the crankshaft 130, which rotates at twice the rotational speed of the intake camshaft 170, is rotating in its first rotation (0° to 360°) corresponding to 0° to 180° of the intake camshaft 170, or is rotating in its second rotation (360° to 720°) corresponding to 180° to 360° of the intake camshaft 170. In other words, while the intake camshaft 170 makes one rotation, it is possible to distinguish whether the crankshaft 130 is rotating in its first rotation or in its second rotation.

[0019] The cam signal plate 250 and the cam angle sensor 260 may be provided on the exhaust camshaft 190, not limited to the intake camshaft 170. The cam signal plate 250 is not limited to the shape shown in Fig. 3, and may have any shape as long as it can output signals of different levels at the tooth missing position in the first rotation and the tooth missing position in the second rotation.

[0020] The crank signal CRS of the crank angle sensor 240 and the cam signal CMS of the cam angle sensor 260 are input to an engine control module (ECM) 270 incorporating a microcomputer 270A. In addition to the output signals of the crank angle sensor 240 and the cam angle sensor 260, the engine control module 270 also receives output signals from a rotation speed sensor 280 that detects the rotation speed Ne of the engine 100, a load sensor 290 that detects the load Q of the engine 100, a water temperature sensor 300 that detects the water temperature Tw of the engine 100, and an air-fuel ratio sensor 310 that detects the air-fuel ratio A / F in the exhaust. Here, as the load Q of the engine 100, for example, a state quantity closely related to the required torque, such as an intake flow rate, an intake negative pressure, a supercharging pressure, an accelerator opening, or a throttle opening, can be used. The engine control module 270 is an example of an engine control device.

[0021] The engine control module 270 executes application programs stored in a non-volatile memory (not shown) of the microcomputer 270A, thereby electronically controlling the fuel injector 210 and the spark plug 220 in response to the output signals of the crank angle sensor 240, the cam angle sensor 260, the rotational speed sensor 280, the load sensor 290, the water temperature sensor 300, and the air-fuel ratio sensor 310.

[0022] At this time, in consideration of the fact that the crank signal CRS of the crank angle sensor 240 is generated every 10° and has low resolution, the engine control module 270 uses a multiplication circuit (not shown) built into the microcomputer 270A to generate a multiplied crank signal CRS' by multiplying (doubling the frequency) the crank signal CRS by 10, as shown in Fig. 4. Therefore, the multiplied crank signal CRS' indicates that the crankshaft 130 has rotated 1°. Note that the multiplied crank signal CRS' is not limited to a configuration in which the crank signal CRS is generated by multiplying it by 10, and may be generated by multiplying the crank signal CRS by a predetermined factor.

[0023] Here, the multiplication circuit sequentially measures the output interval of two consecutive crank signals CRS, and generates a multiplied crank signal CRS' by multiplying the output interval of the previous crank signal CRS by 10. Furthermore, when two consecutive crank signals CRS sandwich a missing tooth position, the multiplication circuit generates a multiplied crank signal CRS' by multiplying the output interval of the previous crank signal CRS by 10. On the other hand, the multiplication circuit generates a multiplied crank signal CRS' by multiplying the output interval of the crank signal CRS immediately before the missing tooth position by 10, because the precision is poor immediately after the missing tooth position due to the missing tooth position.

[0024] Furthermore, the engine control module 270 uses a crank signal counter, a crank angle, and a crank angle counter as parameters used in fuel injection control and ignition control, as shown in FIG.

[0025] The crank signal counter is a counter for determining whether or not the rotation angle of the crankshaft 130 is at a position corresponding to the missing tooth portion 230C of the crank signal plate 230. The crank signal counter counts up in synchronization with the crank signal CRS, and when the count value reaches or exceeds a missing tooth determination threshold value (predetermined threshold value), it is reset by the input of the next crank signal CRS.

[0026] The crank angle is, for example, a counter that periodically counts 0° to 720° of the crankshaft 130, with the top dead center (TDC) of the #1 cylinder as the base point. The crank angle angle recognition value is counted up in synchronization with the crank signal CRS, and is reset when the top dead center of the #1 cylinder is detected.

[0027] The crank angle counter is a counter for controlling the fuel injection timing and the ignition timing. The crank angle counter counts up in synchronization with a crank signal CRS' obtained by multiplying the crank signal CRS by 10, and is reset by the input of the next crank signal CRS after a tooth chipping determination is performed for a specific cylinder. At this time, the crank angle counter is updated successively taking into account the tooth chipping portion 230C of the crank signal plate 230.

[0028] The crank signal counter, crank angle, and crank angle counter may be counted and reset by the engine control module 270, or may be counted and reset by a dedicated electronic circuit.

[0029] The engine control module 270 reads the rotation speed Ne and the load Q from the rotation speed sensor 280 and the load sensor 290, respectively, and calculates a basic fuel injection amount according to the engine operating state specified by the rotation speed Ne and the load Q. The engine control module 270 also reads the water temperature Tw from the water temperature sensor 300, and calculates a fuel injection amount obtained by correcting the basic fuel injection amount with the water temperature Tw. Furthermore, the engine control module 270 calculates the fuel injection timing and the ignition timing according to the rotation speed Ne, the load Q, and the fuel injection amount, respectively.

[0030] When the rotation angle of the crankshaft 130 specified by the crank angle counter reaches the fuel injection timing, the engine control module 270 outputs a control signal corresponding to the fuel injection amount to the fuel injection valve 210, causing the fuel injection valve 210 to inject fuel into the combustion chamber 160. When the rotation angle of the crankshaft 130 specified by the crank angle counter reaches the ignition timing, the engine control module 270 outputs an operation signal to the ignition plug 220 to ignite the mixture of the fuel and the intake air. At this time, the engine control module 270 reads the air-fuel ratio A / F from the air-fuel ratio sensor 310, and feedback controls the fuel injection valve 210 so that the air-fuel ratio A / F in the exhaust approaches the target air-fuel ratio. The engine control module 270 determines the cylinder for which fuel injection and ignition are to be performed according to the output signal of the cam angle sensor 260.

[0031] In an Otto cycle engine, as shown in Fig. 5, an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke are repeated. In the compression stroke of each cylinder, the piston 120 moves toward the top dead center, so that the volume of the combustion chamber 160 gradually decreases, and the rotation speed of the crankshaft 130 temporarily decreases. In the combustion stroke in which the mixture of fuel and intake air is ignited and burned in each cylinder, the combustion pressure of the mixture rapidly pushes the piston 120 toward the bottom dead center, so that the rotation speed of the crankshaft 130 temporarily increases. In this way, in an Otto cycle engine, the rotation speed of the crankshaft 130 fluctuates. The rate of fluctuation of the rotation speed of the crankshaft 130 is large, for example, at low rotation speed, such as during starting.

[0032] In an engine in which the rotational speed of crankshaft 130 fluctuates, if the ignition timing occurs immediately after top dead center of each cylinder, determining the position of missing teeth based on the cycle ratio "current cycle / previous cycle" of the output cycle of the crank signal as in the conventional technology can easily cause the following problems.

[0033] In a steady state where the crankshaft 130 rotates at a constant speed, the output period of the crank signal output from the crank angle sensor 240 is T' (T'=3T) at the position of the missing tooth, where T is the period before the missing tooth, as shown in Fig. 6. In this case, the period ratio of the crank signal at the position of the missing tooth is T' / T=3.

[0034] When the rotation speed of crankshaft 130 decreases, the output period of the crank signal output from crank angle sensor 240 is T before the tooth chipping, as shown in Fig. 6, and becomes T' (T'<3T) at the position of the tooth chipping. In this case, the period ratio of the crank signal at the position of the tooth chipping is T' / T>3. Because the period ratio is greater than 3, no problems occur even if the predetermined threshold value in the prior art is used.

[0035] When the rotation speed of the crankshaft 130 increases, the output period of the crank signal output from the crank angle sensor 240 is T before the missing tooth, as shown in Fig. 6, and then becomes T' (T'<3T) at the position of the missing tooth. In this case, the period ratio of the crank signal at the position of the missing tooth is T' / T<3. Since the period ratio is smaller than 3, if a predetermined threshold value in the prior art is used, the period ratio will not exceed the predetermined threshold value, and there is a risk that the position of the missing tooth cannot be accurately determined.

[0036] Therefore, in this embodiment, when the rotation speed of the crankshaft 130 increases at the missing tooth position, instead of using "current period / previous period" as the period ratio, "previous period / current period" is used to suppress a decrease in the period ratio compared with the predetermined threshold value, and to prevent a decrease in the accuracy of determining the missing tooth position. This process will be described in detail below.

[0037] 7 shows an example of a missing tooth position determination process that the engine control module 270 executes in synchronization with a crank signal from the crank angle sensor 240. The engine control module 270 executes the missing tooth position determination process in accordance with an application program stored in the non-volatile memory of the microcomputer 270A (same below).

[0038] In step 10 (abbreviated as "S10" in FIG. 7, and the same applies below), the engine control module 270 stores the output period of the crank signal measured in the previous control cycle (the previous period) in a volatile memory. Note that, since the previous period is indefinite immediately after starting the engine control module 270, for example, a default value may be set in advance as the previous period, or the previous period may not be stored (and the same applies below).

[0039] In step 11, the engine control module 270 measures the output period from the previous crank signal to the current crank signal (current period) by using, for example, a timer function, etc. If the multiplication circuit has a function for measuring the output period, the engine control module 270 may measure the output period by using this function (same below).

[0040] In step 12, the engine control module 270 determines whether a changeover switch (described in detail later) for switching the calculation method of the period ratio of the crank signal is set to "1". If the engine control module 270 determines that the changeover switch is set to "1" (Yes), the process proceeds to step 13. On the other hand, if the engine control module 270 determines that the changeover switch is not set to "1", i.e., that the changeover switch is set to "0", the process proceeds to step 14.

[0041] In step 13, the engine control module 270 obtains a value obtained by dividing the current period by the previous period as the period ratio of the crank signal (period ratio=current period / previous period). After obtaining the period ratio of the crank signal, the engine control module 270 proceeds to step 15.

[0042] In step 14, the engine control module 270 obtains a value obtained by dividing the previous period by the current period as the period ratio of the crank signal (period ratio=previous period / current period). After obtaining the period ratio of the crank signal, the engine control module 270 proceeds to step 15.

[0043] In step 15, the engine control module 270 determines whether the crank signal period ratio obtained in step 13 or step 14 is equal to or greater than a predetermined threshold. Here, the predetermined threshold is a threshold for determining the position of the missing tooth on the crank signal plate 230 from the ratio of the output periods of two temporally consecutive crank signals, and can be set appropriately according to, for example, the number of teeth 230B on the crank signal plate 230 and the formation angle (length) of the missing tooth portion 230C. If the engine control module 270 determines that the crank signal period ratio is equal to or greater than the predetermined threshold (Yes), it proceeds to step 16. On the other hand, if the engine control module 270 determines that the crank signal period ratio is less than the predetermined threshold (No), it ends the missing tooth position determination process.

[0044] In step 16, the engine control module 270 determines that the crank signal plate 230 is at a missing tooth position because the crank signal period ratio is equal to or greater than a predetermined threshold value. That is, at the missing tooth position of the crank signal plate 230, the output period is longer than the output period of the crank signal immediately before it, so whether or not the position is at a missing tooth position is determined from the ratio of these. Note that the missing tooth position determined in step 16 can be used to read the cam signal from the cam angle sensor 260 and perform cylinder discrimination, as described above.

[0045] According to the tooth missing position determination process, the period of the crank signal in the previous control cycle is stored in synchronization with the crank signal of the crank angle sensor 240, and the period of the crank signal in the current control cycle is measured. If the changeover switch is at "1", the period ratio of the crank signal is calculated by dividing the current period by the previous period (period ratio=current period / previous period). If the changeover switch is at "0", the period ratio of the crank signal is calculated by dividing the previous period by the current period (period ratio=previous period / current period). Then, the period ratio of the crank signal is compared with a predetermined threshold value, and if the period ratio is equal to or greater than the predetermined threshold value, it is determined that the crank signal plate 230 is at a tooth missing position.

[0046] 8 shows an example of a changeover switch setting process that the engine control module 270 executes in synchronization with a crank signal from the crank angle sensor 240. The changeover switch setting process may be executed when the vehicle is not accelerating or decelerating, such as when the rotation speed Ne of the engine 100 remains within a predetermined range (e.g., 600 to 1200 rpm) for a predetermined time (e.g., 5 seconds) or more.

[0047] In step 20, similar to step 10, the engine control module 270 stores the output period of the crank signal measured in the previous control cycle (previous period) in a volatile memory.

[0048] In step 21, similarly to step 11, the engine control module 270 measures the output period from the previous crank signal to the current crank signal (current period) by using a timer function or the like.

[0049] In step 22, the engine control module 270 determines whether the crank signal is due to the first tooth portion 230B after determining the missing tooth position, for example, by using a flag that is set when it is determined that the position is a missing tooth. If the engine control module 270 determines that the crank signal is due to the first tooth portion 230B after determining the missing tooth position (Yes), the process proceeds to step 23. On the other hand, if the engine control module 270 determines that the crank signal is not due to the first tooth portion 230B after determining the missing tooth position (Yes), the process proceeds to step 24.

[0050] In step 23, the engine control module 270 obtains the period ratio α of the crank signal by dividing the current period by the previous period (period ratio α=current period / previous period). Then, the engine control module 270 refers to the minimum value of the period ratio α stored in the volatile memory of the microcomputer 270A, and updates the minimum value of the period ratio α if the currently obtained period ratio α is smaller than the minimum value. Here, the expected value of the period ratio α is 1 in a steady state, greater than 3 in a decreasing state, and less than 3 in an increasing state, with respect to the rotation speed of the crankshaft 130.

[0051] In step 24, the engine control module 270 uses a method similar to that in step 22 to determine whether the crank signal is due to the second tooth portion 230B after determining the position of the missing tooth. If the engine control module 270 determines that the crank signal is due to the second tooth portion 230B after determining the position of the missing tooth (Yes), the process proceeds to step 25. On the other hand, if the engine control module 270 determines that the crank signal is not due to the second tooth portion 230B after determining the position of the missing tooth (Yes), the process proceeds to step 26.

[0052] In step 25, the engine control module 270 obtains the value of the previous period divided by the current period as the period ratio β of the crank signal (period ratio α=previous period / current period). Then, the engine control module 270 refers to the minimum value of the period ratio β stored in the volatile memory of the microcomputer 270A, and updates the minimum value of the period ratio β if the currently obtained period ratio β is smaller than the minimum value. Here, the expected value of the period ratio β is 1 in the steady state, less than 3 in the decreasing state, and greater than 3 in the increasing state, with respect to the rotation speed of the crankshaft 130.

[0053] In step 26, engine control module 270 refers to the minimum value of period ratio α and the minimum value of period ratio β stored in the volatile memory of microcomputer 270A, and determines whether the minimum value of period ratio α is equal to or greater than the minimum value of period ratio β. If engine control module 270 determines that the minimum value of period ratio α is equal to or greater than the minimum value of period ratio β (Yes), it proceeds to step 27. On the other hand, if engine control module 270 determines that the minimum value of period ratio α is less than the minimum value of period ratio β (No), it proceeds to step 28.

[0054] In step 27, the engine control module 270 sets the changeover switch to "1" and ends the changeover switch setting process. In step 28, the engine control module 270 sets the changeover switch to "0" and ends the changeover switch setting process.

[0055] According to the changeover switch setting process, the period of the crank signal in the previous control cycle is stored in synchronization with the crank signal of the crank angle sensor 240, and the period of the crank signal in the current control cycle is measured. Then, if the crank signal of the crank angle sensor 240 is due to the first tooth after the tooth missing position of the crank signal plate 230, the minimum value of the value obtained by dividing the current period by the previous period is sequentially updated as the minimum value of the period ratio α of the crank signal. Also, if the crank signal of the crank angle sensor 240 is due to the second tooth after the tooth missing position of the crank signal plate 230, the minimum value of the value obtained by dividing the previous period by the current period is sequentially updated as the minimum value of the period ratio β of the crank signal. After that, if the minimum value of the period ratio α of the crank signal is equal to or greater than the minimum value of the period ratio β, the changeover switch is set to "1". On the other hand, if the minimum value of the period ratio α of the crank signal is less than the minimum value of the period ratio β, the changeover switch is set to "0".

[0056] Therefore, when the rotation speed of the crankshaft 130 decreases, the output interval of the crank signal gradually becomes longer, so by using the period ratio obtained by dividing the current period of the crank signal by the previous period, it is possible to prevent the period ratio from becoming small and suppress a decrease in the accuracy of determining the position of the missing tooth. Also, when the rotation speed of the crankshaft 130 increases, the output interval of the crank signal gradually becomes shorter, so by using the period ratio obtained by dividing the previous period of the crank signal by the current period, it is possible to prevent the period ratio from becoming small and suppress a decrease in the accuracy of determining the position of the missing tooth.

[0057] In short, by changing the method of calculating the period ratio between a first state in which the output interval of the crank signal gradually becomes longer and a second state in which the output interval of the crank signal gradually becomes shorter, it is possible to avoid a decrease in the period ratio and suppress a decrease in the accuracy of determining the position of missing teeth. In this case, in the first state, the period ratio is obtained by dividing the current period of the output interval of the crank signal by the previous period, and in the second state, the period ratio is obtained by dividing the previous period of the crank signal by the current period.

[0058] Incidentally, when the position of a missing tooth is determined using the period ratio obtained by dividing the current period of the crank signal by the previous period, a missing tooth determination is performed when the period ratio becomes equal to or greater than a predetermined threshold, and the crank signal counter is reset at the first tooth after the missing tooth determination, as shown in Fig. 9. On the other hand, when the position of a missing tooth is determined using the period ratio obtained by dividing the previous period of the crank signal by the current period, a missing tooth determination is performed when the period ratio becomes equal to or greater than a predetermined threshold, and the crank signal counter is reset at the first tooth after the missing tooth determination, as shown in Fig. 9. As is clear from Fig. 9, the timing at which the crank signal counter is reset differs between the case where the period ratio obtained by dividing the current period of the crank signal by the previous period and the case where the period ratio obtained by dividing the previous period by the current period is used, which may affect, for example, fuel injection control or ignition control.

[0059] Therefore, when using the period ratio obtained by dividing the current period of the crank signal by the previous period, as shown in Fig. 10, a missing tooth determination flag may be set when the period ratio becomes equal to or greater than a predetermined threshold, and the missing tooth determination and resetting of the crank signal counter may be performed in response to the next crank signal. By implementing such processing, the crank signal counter is reset at the same timing in both cases where the period ratio obtained by dividing the current period of the crank signal by the previous period is used and where the period ratio obtained by dividing the previous period by the current period is used. Therefore, regardless of which method of calculating the period ratio is used, the crank signal counter is counted in the same way, and it is possible to avoid, for example, affecting fuel injection control or ignition control.

[0060] As shown in Fig. 11, the period ratio of the crank signal may be always calculated as a first period ratio obtained by dividing the current period by the previous period, and a second period ratio obtained by dividing the previous period by the current period. When the value obtained by dividing the current period by the previous period is used as the period ratio of the crank signal, the missing tooth determination may be performed using the first period ratio, and when the value obtained by dividing the previous period by the current period is used as the period ratio of the crank signal, the missing tooth determination may be performed using the second period ratio. In this way, it is possible to appropriately switch the calculation method of the period ratio during the rotation of the crankshaft 130. For example, even if there are multiple missing tooth positions during two rotations (720°) of the crankshaft 130, it is possible to select an appropriate calculation method for each missing tooth position.

[0061] As described above, the rate of change in the rotation speed of the crankshaft 130 is large when the engine is rotating at low speed, such as at start-up. On the other hand, the rate of change in the rotation speed of the crankshaft 130 is small when the engine is rotating at medium to high speed, such as during high-speed driving. Therefore, when the engine is rotating at high speed, the method of calculating the period ratio of the crank signal can ensure sufficient accuracy in determining the position of the missing tooth regardless of whether the period ratio is obtained by dividing the current period by the previous period or the previous period by the current period. For this reason, when the rotation speed Ne of the engine 100 is equal to or lower than a predetermined value, the calculation method of the period ratio may be switched. Here, the predetermined value may be a value at which the fluctuation in the rotation speed of the crankshaft 130 cannot be ignored, taking into account the number of cylinders and characteristics of the engine 100.

[0062] In addition, in consideration of the possibility that the crank signal output from the crank angle sensor 240 becomes abnormal and the engine control module 270 erroneously determines the position of the missing tooth, the determination of the position of the missing tooth may be prohibited during a period in which a predetermined number of crank signals are output when the determination of the position of the missing tooth is performed. Here, the predetermined number may be, for example, 3.

[0063] Furthermore, a person skilled in the art will easily understand that new embodiments can be created by omitting parts of the technical ideas of the various above-mentioned embodiments, combining parts of them appropriately, or replacing parts of them with well-known technology.

[0064] For example, the state in which the rotation speed of the crankshaft 130 decreases and increases may be determined in relation to the combustion stroke of the engine 100, instead of the output interval between two consecutive crank signals, or in consideration of the ignition timing of the engine 100. The changeover switch may be set using the maximum value of the period ratio of the crank signal, instead of the minimum value. Furthermore, the changeover switch may be set only once, for example, when the steady state is deviated from, instead of every time in synchronization with the crank signal. [Explanation of symbols]

[0065] 230... crank signal plate 230B... tooth portion 230C... missing tooth portion 240... crank angle sensor 270... engine control module (engine control device)

Claims

1. 1. An engine control device comprising: a crank angle sensor that detects a tooth portion of a crank signal plate having a missing tooth portion formed thereon, reads an output signal of the crank angle sensor that outputs a pulse-like crank signal, and determines a position of the missing tooth portion of the crank signal plate based on a cycle ratio of an output interval of the crank signal, the engine control device comprising: In a first state in which the output interval of the crank signal gradually becomes longer, a period ratio is obtained by dividing a current period of the output interval of the crank signal by a previous period, and in a second state in which the output interval of the crank signal gradually becomes shorter, a period ratio is obtained by dividing a previous period of the crank signal by the current period. Engine control device.

2. When the period ratio is equal to or greater than a predetermined threshold value, it is determined that the tooth chipping position exists. The engine control device according to claim 1.

3. The change in the calculation method of the period ratio is performed when the engine rotation speed is equal to or lower than a predetermined value. The engine control device according to claim 1 or 2.

4. when the position of the missing tooth is determined, the determination of the position of the missing tooth is prohibited during a period in which a predetermined number of the crank signals are output. The engine control device according to any one of claims 1 to 3.

Images