Stroke determination device for four-stroke cycle single-cylinder engine

Abstract

The present invention relates to a stroke discriminating device for a four-stroke cycle single-cylinder engine that uses a relatively small number of components to discriminate the stroke of the four-stroke cycle single-cylinder engine. After the engine is started, the stroke discriminating device for the four-stroke cycle single-cylinder engine calculates the average time before the ignition reference point required to generate an arbitrary number of pulses from a toothless portion to an ignition reference point and the average time after the ignition reference point required to generate the arbitrary number of pulses after the ignition reference point, and compares the time obtained by multiplying the average time before the ignition reference point by a prescribed coefficient with the average time after the ignition reference point. When the average time after the ignition reference point is smaller, it is discriminated that the current crank top dead center is the compression top dead center and the next crank top dead center is the exhaust top dead center.

Description

Technical Field

[0001] The invention relates to a stroke distinguishing device for a four-stroke cycle single-cylinder engine. Background Art

[0002] In the past, for example, as an internal combustion engine for vehicles, a four-stroke cycle single-cylinder engine is widely known. This four-stroke cycle single-cylinder engine repeats the four strokes of intake stroke, compression stroke, expansion stroke, and exhaust stroke as a cycle to obtain a rotational output. However, since the piston reciprocates twice in one cycle, it is difficult to determine which stroke it corresponds to by only looking at the position of the piston (crank angle).

[0003] The fuel injection timing is performed during the intake stroke, and the ignition timing is performed near the terminal (top dead center) during the compression stroke. On the other hand, fuel injection is not required during the intake stroke, and ignition is not required during the expansion stroke. In order to prevent the occurrence of afterburning, etc., and to perform efficient ignition injection control, a certain stroke discrimination method is required.

[0004] As a method for determining the stroke of a single-cylinder engine, for example, a method for determining the stroke based on a crank signal and an intake pipe pressure signal is known, such as the invention described in Japanese Patent Laid-Open No. 10-227252 (Patent Document 1). However, in recent years, in order to control vehicles at low cost, it is necessary to reduce the number of sensors or components installed as much as possible.

[0005] In this regard, there is known an engine stroke discriminating device that compares the voltage of an ignition signal to discriminate between a compression stroke and an exhaust stroke, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2014-070537 (Patent Document 2).

[0006] However, although the invention described in the document utilizes the fact that the peak voltage of the spike waveform of the ignition signal shows different waveforms due to the difference in the exhaust stroke and the compression stroke depending on the engine rotation speed, it is impossible to set an appropriate threshold value, or when the peak voltage of the spike waveform changes due to degradation, etc., it may be impossible to distinguish the stroke.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-227252

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-070537 Summary of the invention

[0009] Therefore, an object of the present invention is to perform stroke discrimination of a four-stroke cycle single-cylinder engine with a small number of parts without using an intake pipe pressure sensor or an ignition signal voltage.

[0010] The present invention implemented to solve the above-mentioned problems is a stroke discrimination device for a four-stroke cycle single-cylinder engine, characterized in that it includes: a rotating body, which rotates synchronously with the crankshaft of the four-stroke cycle single-cylinder engine, and has a plurality of teeth formed at equal angles on the outer circumference and a missing tooth portion formed by cutting off one of the teeth, a crank angle sensor, which detects the teeth and outputs a pulse signal, and an electronic control unit, to which the pulse signal is input; the tooth portion located at a specified number from the missing tooth portion becomes an ignition reference point corresponding to the crank top dead center, and after the engine is started, the number of pulses generated between the missing tooth portion and the ignition reference point is measured. The method comprises the following steps: calculating the required total time before the ignition reference point and the required total time after the ignition reference point required to generate the arbitrary number of pulses after the ignition reference point, calculating the average time before the ignition reference point obtained by dividing the total time before the ignition reference point by the arbitrary number of pulses, and the average time after the ignition reference point obtained by dividing the total time after the ignition reference point by the arbitrary number of pulses, and comparing the time obtained by multiplying the average time before the ignition reference point by a specified coefficient with the average time after the ignition reference point. When the average time after the ignition reference point is smaller, it is determined that the current crank top dead center is the compression top dead center and the next crank top dead center is the exhaust top dead center.

[0011] According to the present invention, only the crank angle sensor is used to measure the time and perform simple calculations, that is, the intake pipe pressure sensor and the voltage of the ignition signal are not used. The stroke of a four-stroke cycle single-cylinder engine can be determined with a simple structure that does not require additional components.

[0012] In the present invention, it is preferred that the teeth are provided at intervals of 15°, the tooth at the ignition reference point is the ninth tooth from the missing tooth portion, and the arbitrary number of pulses is 7 pulses.

[0013] In the present invention, when the predetermined coefficient is a value smaller than 1, it is possible to prevent erroneous determination when the stroke is determined based on the crank speed difference before and after the ignition reference point in consideration of the piston acceleration due to the explosion.

[0014] According to the present invention, the stroke determination of a four-stroke cycle single-cylinder engine can be performed with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram showing the overall structure of the stroke discriminating device of a four-stroke cycle single-cylinder engine according to the present invention.

[0016] Figure 2 It is a diagram showing the flow of the stroke discrimination process in the present invention.

[0017] Figure 3 This is a diagram showing a pulse signal before the stroke discrimination is completed in the present invention.

[0018] Figure 4 It is a diagram showing the waveform of the pulse signal in the present invention.

[0019] Description of Reference Numerals

[0020] 1: Four-stroke cycle single cylinder engine,

[0021] 2: Crankshaft,

[0022] 3: Cylinder,

[0023] 4: Piston,

[0024] 5: Crank,

[0025] 6: Intake valve,

[0026] 7: Exhaust valve,

[0027] 8: Spark plug,

[0028] 10: Rotating body,

[0029] 11: Tooth,

[0030] 12: Toothless part,

[0031] 20: Crank angle sensor,

[0032] 30: Electronic control unit,

[0033] 31: Ignition coil,

[0034] 32: Fuel injection device. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0036] Figure 1 It is a schematic diagram showing the overall structure of the stroke determination device of the four-stroke cycle single-cylinder engine of the present invention. As shown in the figure, the device includes a rotating body 10 that rotates synchronously with the crankshaft 2, a crank angle sensor 20 and an electronic control unit 30; it is used to perform stroke determination of the four-stroke cycle single-cylinder engine 1.

[0037] The four-stroke cycle single-cylinder engine 1 is an engine used, for example, for vehicles, and has a crank 5 that rotates around the crankshaft 2 and moves the piston 4 up and down in the cylinder 3, an intake valve 6, an exhaust valve 7 and a spark plug 8. The four strokes of intake stroke, compression stroke, expansion stroke and exhaust stroke are repeated as a cycle to obtain a rotational output.

[0038] The rotating body 10 has a plurality of teeth 11 formed at equal angles on the outer circumference and a missing tooth 12 formed by cutting off one of the teeth 11. Since the rotating body 10 rotates synchronously with the crankshaft 2, when the four-stroke cycle is completed, the rotating body 10 rotates twice like the crankshaft 2. In this embodiment, the teeth 11 are arranged every 15°.

[0039] The crank angle sensor 20 is a non-contact sensor that detects the teeth 11 formed on the rotating body 10 and outputs a pulse signal, and for example, a magnetic sensor may be used.

[0040] The electronic control unit 30 is a device that receives the pulse signal, has a timer function for measuring the time, and can perform calculations. In this embodiment, an ECU (electronic control unit) for a vehicle is used to control the ignition coil 31 and the fuel injection device 32 to perform ignition injection control.

[0041] The following is based on Figures 2 to 4 The stroke determination process in the present invention will be described.

[0042] Figure 2 It is a diagram showing the flow of the stroke discrimination process in the present invention.

[0043] When the stroke discrimination process starts, it is first determined whether the stroke discrimination is completed. If the stroke discrimination has not yet been performed, regardless of whether it is the intake stroke or compression stroke (hereinafter referred to as the outer stroke) that requires fuel injection or ignition, or the expansion stroke or exhaust stroke (hereinafter referred to as the inner stroke) that does not require fuel injection or ignition, ignition is carried out when the fuel injection and the pulse serving as the ignition reference (hereinafter referred to as the ignition reference point) arrive.

[0044] One of the teeth located at the predetermined number from the missing tooth portion (standing) becomes the ignition reference point corresponding to the crank top dead center. In this embodiment, the tooth portion of the ignition reference point is the 9th tooth portion from the missing tooth portion (refer to Figure 3 : Pulse I).

[0045] The total time required from several pulses before the ignition reference point to the observation of the ignition reference point is measured, and the average time before one pulse passes the desired ignition reference point is calculated (refer to Figure 4 :Time1). Then, as mentioned above, ignition is carried out in both the outer stroke and the inner stroke. Then, the total time required from one pulse after the ignition reference point to the observation of the following pulses is measured and the average time after a pulse passes the desired ignition reference point is calculated in the same way (refer to Figure 4 :Time2).

[0046] In the present embodiment, the number of pulses is set to 7. In the present embodiment using a rotating body composed of 23 teeth and 1 missing tooth, 7 pulses are suitable for measuring the total time and calculating the average time, but it can also be set to other pulse numbers according to the number of teeth of the rotating body, etc.

[0047] Then, the time obtained by multiplying the average time before the ignition reference point (Time1) by the coefficient is compared with the average time after the ignition reference point (Time2).

[0048] When ignition is performed and combustion is complete during the table stroke, when the time obtained by multiplying the average time before the ignition reference point by a coefficient is compared with the average time after the ignition reference point, the average time after the ignition reference point is a smaller value.

[0049] Therefore, when the average time after the ignition reference point is small, it is determined that ignition has occurred in the outer stroke, the next stroke is set as the inner stroke, the stroke determination is completed and the process returns to the process before the start of the stroke determination process to perform subsequent ignition injection control.

[0050] At this time, the coefficient is set to a value less than 1. The purpose is to prevent erroneous judgment by multiplying the average time before ignition by a coefficient greater than 0 and less than 1 when the stroke is judged based on the crank speed difference before and after the ignition reference point, because the piston is accelerated when the top dead center explodes, and the generation time of one pulse after ignition is shorter than that before ignition.

[0051] In addition, because the battery voltage is low during startup, the amplitude is small before ignition, and because the engine is completely burned and the battery begins to charge, the amplitude becomes larger after ignition, but the size of the amplitude has nothing to do with control.

[0052] When comparing the time obtained by multiplying the average time before the ignition reference point (Time1) by a coefficient with the average time after the ignition reference point (Time2), if the average time after the ignition reference point (Time2) is larger or equal, the process returns to the process before the start of the stroke discrimination process with the stroke discrimination being incomplete.

[0053] After completing stroke discrimination and transferring to ignition injection control, fuel injection is performed only in the injection stroke which is the outer stroke, and ignition is performed only in the compression stroke. No fuel injection or ignition is performed in the expansion stroke or exhaust stroke which are the inner strokes.

[0054] As described above, according to the present invention, only the crank angle sensor is used to measure the time and perform simple calculations, that is, the intake pipe pressure sensor and the voltage of the ignition signal are not used, so the stroke of the four-stroke cycle single-cylinder engine can be determined with a simple structure that does not require additional components.

Claims

1. A stroke determination device for a four-stroke cycle single-cylinder engine, characterized in that: include: The rotating body rotates synchronously with the crankshaft of the four-stroke cycle single-cylinder engine, and has a plurality of teeth formed at equal angles on the outer circumference and a missing tooth portion formed by cutting off one of the teeth. a crank angle sensor, detecting the tooth portion and outputting a pulse signal, and an electronic control unit, into which the pulse signal is input; The tooth portion located at a predetermined number from the missing tooth portion becomes an ignition reference point corresponding to the crank top dead center. After the engine is started, the total time before the ignition reference point required to generate an arbitrary number of pulses from the tooth-missing portion to the ignition reference point and the total time after the ignition reference point required to generate the arbitrary number of pulses after the ignition reference point are measured. Calculating an average time before the ignition reference point obtained by dividing the total time before the ignition reference point by the arbitrary number of pulses and an average time after the ignition reference point obtained by dividing the total time after the ignition reference point by the arbitrary number of pulses, The time obtained by multiplying the average time before the ignition reference point by a predetermined coefficient is compared with the average time after the ignition reference point. When the average time after the ignition reference point is small, it is determined that the current crank top dead center is the compression top dead center and the next crank top dead center is the exhaust top dead center.

2. The stroke determination device for a four-stroke cycle single-cylinder engine according to claim 1, characterized in that: The teeth are arranged at intervals of 15°. The tooth portion of the ignition reference point is the ninth tooth portion from the missing tooth portion, The arbitrary number of pulses is 7 pulses.

3. The stroke determination device for a four-stroke cycle single-cylinder engine according to claim 1, characterized in that: The prescribed coefficient is a value smaller than 1.

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