JP4480026B2 - Engine ignition device - Google Patents

Description

  The present invention relates to an ignition device for an engine, and more particularly, an engine having a CDI circuit that charges a capacitor with an output of a generator driven by the engine and discharges the capacitor at a preset control timing according to the engine speed. The present invention relates to an ignition device.

  An ignition device for a small general-purpose engine used for driving a work machine or the like is generally an operation timing adapted to the rotation of the engine detected by a signal coil such as a pulsar coil provided for a flywheel connected to the engine. It is driven by.

  On the other hand, in recent years, for example, as in the digital CDI described in Japanese Patent Application Laid-Open No. 2005-163616, the ignition device is controlled by a microcomputer, and the engine speed and ignition timing are arbitrarily set to be appropriate. Advancing angle characteristics are also provided. In a small general-purpose engine equipped with such a microcomputer-controlled ignition device, there is an example in which the output of a generator driven by this engine is used for both ignition energy and engine rotation detection.

On the other hand, in a small general-purpose engine, since it is required that the engine can be started and stopped with a simple operation, a rotary switch, a push button switch, or the like, which is an engine stop switch, is provided to be exposed outside the aircraft. There are many cases.
JP 2005-163616 A

  As described above, in a situation where the engine can be easily started and stopped, the stop switch is erroneously repeatedly turned on (= stop operation) or turned off in a short time with respect to the operating engine. There is a case. However, if such a repeated operation is performed, the engine speed signal cannot be detected temporarily, and it may be recognized as an incorrect speed and an ignition signal corresponding to this may be output.

  An object of the present invention is to provide an engine ignition device suitable for solving the above-described problems and operating the ignition device based on an accurate engine speed.

  In order to achieve the above object, the present invention provides a power generation coil that generates power by rotating an engine, a rectifier circuit that charges an output capacitor of the power generation coil to an ignition capacitor connected to a primary side of the ignition coil, and an engine speed An ignition device for an engine having a means for outputting an ignition timing according to the engine, a switching means for discharging the ignition capacitor at an ignition timing according to the engine speed, and an engine stop switch. Means for detecting the engine speed based on the period of the signal formed on the basis of the signal, and the signal is newly transmitted within a determination time set to a time longer than the period based on the period of the signal detected last time. If not detected, the forced drive means for driving the switching means regardless of the ignition timing according to the engine speed. There is first characterized in that the Bei.

  The determination time has a second feature in that a time obtained by multiplying the period of the previous detection signal by a predetermined coefficient is set.

  Further, the present invention is characterized in that the rectifier circuit is configured to supply one half cycle of the AC output of the power generation coil to the ignition capacitor while supplying the other half cycle as a control power source. There is a third feature.

  Furthermore, the present invention has a fourth feature in that the engine stop switch is disposed at a position where the ignition output of the power generation coil is short-circuited.

  According to the first feature, the engine stop switch is erroneously operated and the engine stop / start operation is repeated, so that a new signal is not detected within the determination time set longer than the previously detected cycle. In this case, the forcible driving means operates so that the ignition capacitor maintains a discharged state. As a result, ignition at an inaccurate ignition timing of the ignition device is suppressed.

  In addition, since the detection signal processing can solve the problem caused by the erroneous operation of the engine stop operation switch, the degree of freedom of the layout of the switch position can be increased in terms of the electric circuit configuration.

  According to the second feature, even if the engine speed greatly changes, the determination time can be appropriately changed correspondingly.

  According to the third feature, since the control power source of the ignition device can be obtained from the output not used for the ignition energy of the power generation coil, the ignition device can be made battery-free.

  According to the fourth feature, since the ignition control power supply disappears after the ignition operation is stopped and the engine rotation is substantially stopped, the ignition operation until the engine stops is surely stopped. be able to.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a perspective view of a brush cutter to which an engine ignition device according to an embodiment of the present invention is applied. In FIG. 2, the brush cutter 100 includes an engine 1, an operation sleeve 20 that extends from the engine 1 and includes a cutting blade 110 at a tip, a handle 120 provided in the middle of the operation sleeve 20, and a right end of the handle 120. And an operating device 16 serving as a grip provided in the section. A throttle cable 9 extending from the operating device 16 to the carburetor 8 of the engine 1 is provided. The engine 1 is a small (for example, 25 cubic cm) air-cooled four-stroke single-cylinder engine suitable for the brush cutter 100, and a flywheel generator (not shown) is directly connected to the engine 1.

  FIG. 1 is a diagram showing a configuration of an engine speed control device. The generator coil 2 of the flyhole generator generates an alternating current synchronized with the rotation of the engine. This alternating current is rectified by the diodes 3 and 4. One half cycle of the rectified alternating current is input to the regulator 5 forming the control power source and adjusted to the operating voltage of the CPU 6, and the operating voltage is supplied to the CPU 6.

  The other half cycle of the rectified alternating current is connected to the primary side 11 of the ignition coil 10 via the capacitor 7. The secondary side 12 of the ignition coil 10 is connected to a spark plug 13.

  Thus, the battery-less ignition device is configured by using the output of the power generation coil 2 as the ignition energy power source and the ignition control power source.

  The other half cycle of the rectified alternating current is further input to the rectangular wave circuit 14. The capacitor 7 is connected in parallel with a thyristor (SCR) 15 as a switch means. The output of the rectangular wave circuit 14 is input to the CPU 6. The CPU 6 has a function of detecting the falling edge of the waveform shaped by the rectangular wave circuit 14 and detecting its cycle. The detection cycle is also a value representative of the engine speed. An ignition timing (crank angle) as a function of the engine speed calculated by the CPU 6 based on a signal input from the rectangular wave circuit 14 is preset in the ignition timing map 17. The CPU 6 searches for an ignition timing corresponding to the engine speed input from the ignition timing map 17. In this case, the CPU 6 may be configured not to search the ignition timing from the map but to calculate the ignition timing using a preset function formula of the engine speed. In any case, the relationship between the engine speed and the ignition timing is performed by digital arithmetic processing using digital data.

  The CPU 6 generates an ignition signal when the rotational position of the engine 1 reaches the crank angle read from the ignition timing map 17, that is, the ignition timing. The ignition signal is input to the gate of the SCR 15, the capacitor 7 is discharged, a high voltage is induced on the secondary side 12 of the ignition coil 10, and the spark plug 13 is ignited.

  Further, a stop operation switch 18 for stopping the engine 1 is provided on the cathode side of the diode 4. The stop operation switch 18 is provided at a position for short-circuiting the output on one side of the output of the power generation coil 2 via the diode 4. By closing the stop operation switch 18 and short-circuiting the generator coil 2, the energy supplied to the ignition coil 10 is lost. At this time, since the supply to the regulator 5 of the output of the power generation coil 2 is continued as it is, the control power supply can be maintained until the output of the power generation coil 2 substantially stops. The ignition operation can be reliably maintained in the stopped state until the switch 18 is turned on and the engine 1 substantially stops.

  Furthermore, the CPU 6 has a function of reliably stopping the engine 1 by maintaining the capacitor 7 in a discharged state when the falling of the rectangular wave input from the rectangular wave circuit 14 is not detected within a predetermined time.

  FIG. 3 is a timing chart showing the stop operation of the engine 1. In the figure, the input pulse is a rectangular wave input from the rectangular wave circuit 14 to the CPU 6. The falling cycle of this input pulse corresponds to one cycle of the engine 1. The SCR 15 is turned on at a timing corresponding to the detected cycle of the engine 1, that is, the rotational speed. The capacitor 7 starts charging at the falling edge of the input pulse and is discharged when the SCR 15 is turned on.

  When the trailing edge of the next input pulse is not detected within the predetermined determination time Tr after detecting the period T1 of the previous input pulse, the CPU 6 turns on the SCR 15 and maintains that state. The determination time Tr is, for example, a value obtained by multiplying the previous cycle T1 by a coefficient A. The coefficient A is “4”, for example. That is, if an input pulse is not detected even after a time four times the previous period T1, the capacitor 7 is forcibly discharged to stop the engine 1.

  For example, it is assumed that the engine 1 is rotating at 3000 rpm. Since the period of one rotation is 20 milliseconds, in this example, the determination time is set to 80 milliseconds. The operation of the stop operation switch 18 from OFF to ON usually takes 5 to 10 milliseconds, but is sufficiently shorter than 80 milliseconds, so that when the stop operation switch 18 is turned ON, the generator coil 2 is short-circuited, and Since the SCR 15 is turned on when the time during which no input pulse is detected exceeds 80 milliseconds, the engine 1 can be reliably stopped.

  On the other hand, if the stop operation switch 18 is turned on and then turned off within a short time, the input pulse is not input at an accurate cycle for determining the rotation speed. For example, some input pulses may be missing and the period may be determined to be a much longer time T2. Therefore, the ignition timing may be determined based on an inappropriate cycle T2. However, the cycle T2 when the stop operation switch 18 is repeatedly turned on and off is generally several hundred milliseconds, which exceeds the determination time Tr (80 milliseconds). The falling edge of the input pulse is not detected within Tr. Therefore, the SCR 15 is forcibly turned on and the engine 1 is stopped. Therefore, even if the stop operation switch 18 is erroneously turned on and off within a short time, it is possible to prevent ignition at an inappropriate ignition timing.

  If the coefficient A is set to about “1”, the engine may be stopped even if the contact is connected even for a short time by touching the stop operation switch 18 and one pulse is missing. If the coefficient A is set to “4”, such a problem can be avoided.

  Further, by multiplying by the coefficient A, it is possible to make the allowable rotation speed detection error range even when the rotation speeds are greatly different.

  For example, assuming that the engine 1 is rotating at 7000 rpm, since the cycle of one rotation is 8.6 ms, the determination time is set to 4 × 8.6 ms = 34.4 ms in this example.

  In the present embodiment, a battery-less ignition device such as a recoil starter starting engine is configured. However, the ignition system can be appropriately used for a control system including a battery.

It is a block diagram which shows the structure of the ignition device of the engine which concerns on one Embodiment of this invention. It is a perspective view of a brush cutter to which the control device of the present invention is applied. It is a timing chart which shows the principal part operation | movement of the ignition device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Power generation coil, 3, 4 ... Diode, 5 ... Regulator, 6 ... CPU, 7 ... Capacitor, 8 ... Carbator, 9 ... Throttle cable, 10 ... Ignition coil, 13 ... Spark plug, 15 ... Thyristor, 17 ... ignition timing map, 18 ... stop operation switch, 20 ... operation sleeve

Claims (4)

A power generation coil that generates power by rotating the engine, a rectifier circuit that charges an ignition capacitor connected to the primary side of the ignition coil with an output current of the power generation coil, means for outputting an ignition timing according to the engine speed, In an engine ignition device having switching means for discharging the ignition capacitor at an ignition timing corresponding to the engine speed, and an engine stop switch,
Means for detecting an engine speed based on a period of a signal formed based on an induced voltage of the power generation coil;
When the signal is not newly detected within the determination time set to a time longer than the cycle based on the cycle of the signal detected last time, the switching means is turned on regardless of the ignition timing according to the engine speed. An engine ignition device comprising: a forced drive means for driving.   2. The engine ignition device according to claim 1, wherein the determination time is set to a time obtained by multiplying a cycle of the previous detection signal by a predetermined coefficient.   2. The rectifier circuit is configured to supply one half cycle of the AC output of the power generation coil to the ignition capacitor while supplying the other half cycle as a control power source. An ignition device for an engine as described. The engine ignition device according to claim 2, wherein the engine stop switch is disposed at a position for short-circuiting the ignition output of the power generation coil.

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