JPS61272472A - Spark ignition engine - Google Patents

Abstract

PURPOSE:To prevent the engine-stop at the engine-start and to enable he engine speed at idling to be lowered, by providing a means which delays the ignition timing at a low engine speed range. CONSTITUTION:When the engine speed is low, since the charging voltage for a condenser 35 is also low, the voltage of the condenser 35 becomes lower than the gate trigger voltage of a thyrister 34 before an exciter coil 10 generates a negative output E3. Accordingly, the thyrister 34 is never electrified by a negative output E3 generated by the exciter coil 10. As a result, electrifying time to the thyrister 19 is delayed until the charging voltage of a condenser 41 reaches a specified voltage, thereby delaying the spark generating timing. When the engine speed goes up, since the negative output E3 generated by the exciter coil 10 goes upward, the thyrister 34 is electrified. Thus, the thyrister 19 is electrified to the rise of the output E2, thereby performing ignition and also advancing the crank angle by a specified angle.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a spark ignition type engine, and more particularly to a spark ignition type engine in which a spark is generated by an ignition device, and the spark ignites the engine to cause combustion and explosion, thereby obtaining output. KSummary of the Invention 1 The present invention delays the ignition timing of a spark ignition engine that generates sparks to ignite the engine at low speeds, and furthermore, when the engine speed reaches an arbitrary predetermined speed in the process of increasing the speed. By advancing the ignition timing in steps and setting the ignition timing at a predetermined value in the engine's normal rotation range, and further retarding the ignition timing in steps from the ignition timing at low speeds in the high-speed rotation range, It is designed to improve the characteristics of KPrior Art 1 In an engine that uses an ignition device to generate sparks to ignite, the ignition timing is set at the normal rotation speed at the time of startup, that is, at an angle approximately 30 degrees advanced from top dead center. When igniting the engine, it tends to squeak when the recoil starter is pulled, which worsens the starting feeling. Additionally, engine rotation becomes unstable during idle link. In order to prevent such a phenomenon, the timing of ignition can be delayed. On the other hand, when used in an engine that drives equipment with large load fluctuations, such as a lawn mower or a pump, the rotational speed of the engine rapidly increases when the load on the engine decreases. This creates the possibility of engine overrun and further engine destruction. Even if it is not destroyed, durability deteriorates, vibration increases due to overrun, noise is generated, and furthermore, it is accompanied by discomfort during use. Problems to be Solved by the K Invention: If the ignition angle is delayed to prevent engine firing when starting the engine, the voltage required by the plug will increase.
It becomes necessary to increase the secondary voltage when the magnet generator rotates at low speed. Therefore, it is not necessarily desirable to recklessly delay the ignition angle beyond the overrun region in pursuit of engine feel. On the other hand, during normal operation and high speed, the engine speed is increasing, so the secondary voltage of the magnet generator is also high, so even if the ignition timing is delayed from the starting time, the voltage increase required by the plug will not be met. is not a big problem. Next, in order to prevent an overrun in which the engine speed suddenly increases due to a sudden decrease in load, it is possible to prevent overspeed by using a mechanical governor or carburetor. However, mechanical governors are large and heavy, which is disadvantageous for engines used in hand-held machines. Also, when controlling high speed with a capretor,
Since a large amount of fuel is supplied at high speeds to make the fuel rich and suppress the rotation speed, it is necessary to set the carburetor so that a large amount of fuel is temporarily supplied from the high speed side of the normal rotation range, which reduces fuel consumption. In addition, the acceleration performance in the normal rotation range will deteriorate. Furthermore, this method
This has the disadvantage that the control rotational speed varies widely. The present invention has been made in view of these problems, and provides a spark ignition engine that prevents engine failure during startup, lowers the rotational speed during idling, and prevents engine overrun. The purpose is to Means for Solving Problem K 1 The present invention provides an engine in which an ignition device generates a spark, ignites the spark, causes combustion and explosion, and thereby obtains output. A method for delaying the timing of engine rotation, a means for advancing the ignition angle stepwise when the engine speed reaches a predetermined speed during the process of increasing the engine speed, and a means for increasing the ignition angle in steps when the engine speed reaches an overrun region. A means for retarding the ignition timing in steps further than the ignition timing in the low rotational speed region is provided. 1. Therefore, according to the present invention, ignition is performed at a delayed angle in a low speed region, and it is possible to prevent the engine from stalling when starting the engine. Further, according to the present invention, by lowering the idling speed and advancing the ignition timing in steps, it is possible to maintain a predetermined ignition timing in the normal speed range, and moreover, when the engine speed reaches the overrun region. In this case, ignition is performed at a stepwise retardation compared to the low speed region, thereby making it possible to prevent overrun.

【Example】

The present invention will be explained below with reference to an illustrated embodiment. FIG. 1 shows an ignition system for a spark-ignition engine according to an embodiment of the present invention, and this ignition system is equipped with an exciter coil 10 and a magnet 12 provided on a rotor 11. The output is generated by magnetic flux. This exciter coil 10 is connected to a capacitor 15 via a retard circuit 13 and a diode 14. A diode 16 is connected in parallel to the capacitor 15. The capacitor 15 is connected to the primary coil 18 of the ignition coil 17.
is connected to. Further, a thyristor 19 and a diode 20 are connected in series with the capacitor 15 and the primary coil 18. An advance angle circuit 21 is connected between the thyristor 19 and the diode 20. In addition, the ignition coil 17
A spark plug 23 is connected to the secondary coil 22 of. Next, the retard circuit 13 will be explained. This retard circuit 13 includes a second thyristor 24 and a resistor 2.
5 is connected in series. And this thyristor 24
The gate of is connected via a capacitor 26 and a resistor 27. Capacitor 26 is connected to exciter coil 10 via diode 28. Furthermore, a varistor 29 and a thermistor 3 are connected in parallel to the capacitor 26.
A series circuit of 0 and a resistor 31 and a variable resistor 32 are connected. Furthermore, this retard circuit 13 includes a diode 33. Next, the advance angle circuit 21 connected to the thyristor 19 will be explained. The advance angle circuit 21 is connected to the third thyristor 3.
4, the gate of which is connected to the capacitor 35 via a resistor 45. In addition, a varistor 36 is connected in parallel to this capacitor 35.
A series circuit of a thermistor 37 and a resistor 38, and a variable resistor 39 are connected. Further, the advance angle circuit 21 includes a capacitor 41, which is connected to the negative side of the exciter coil 10 via a diode 40. The connection point between this capacitor 41 and diode 40 is
It is connected to the gate of the thyristor 19 via a resistor 42. Next, the operation of the engine equipped with the ignition device having the above configuration will be explained. Each time the rotor 11 rotates, the exciter coil 10 is activated as shown in FIG. 3A or 4A.
Generates an output waveform as shown in . That is, an output E1 in a negative direction, an output E2 in a positive direction, and an output E3 in a negative direction are generated every rotation of the rotor 11. Then, due to the positive output E2 of the exciter coil 10, current flows through the diode 28, the capacitor 26, the diode 14, the capacitor 15, the primary coil 18 of the ignition coil 17, and the exciter coil 10 in this order. At the same time, the current flowing through the diode 28 flows through the varistor 29, the thermistor 30, and the resistor 3.
1 series circuit and the resistor 32, respectively. This current causes the capacitor 15 to
It will be charged to the polarity shown in the figure and will store energy for ignition. The change in voltage of this capacitor 15 is shown in Figure 3B.
or as shown in FIG. 4B. Next, when the output of the exciter coil 10 changes to the negative direction and the exciter coil 10 generates an output E3 in the negative direction,
Exciter coil 10, diode 40, capacitor 4
1, a current flows through the diode 44, the diode 33, and the exciter coil 10 in this order. The capacitor 41 is then charged by this current. Changes in the charging voltage of the capacitor 41 are shown in the third or fourth diagram. The charge in the capacitor 41 flows through the resistor 42, the gate of the thyristor 19, the cathode thereof, the varistor 36, and the capacitor 41 in this order and is discharged. Therefore, as shown in the third diagram, when the charging voltage of the capacitor 41 exceeds the gate trigger voltage V (11) of the thyristor 19, the ignition thyristor 19 becomes conductive. The electric charge rapidly flows through the anode of the thyristor 19, the cathode of the thyristor, the varistor 36, the diode 20, the primary coil 18 of the ignition coil 17, and the capacitor 15 in this order, and as a result, a high voltage is generated in the secondary coil 22 of the ignition coil 17. , a spark is generated in the ignition plug 23 to perform the ignition operation. Therefore, when the engine speed is low, the conduction of the thyristor 19 is stopped until the charging voltage of the capacitor 41 reaches the predetermined voltage Vg1 as described above. This causes a delay in the timing of spark generation. This delay in the ignition angle in the low engine speed range is shown in Figure 2. The operation of advancing the angle in steps when it reaches an arbitrary predetermined rotation speed in the process of increasing the rotation speed will be explained.As described above, when the thyristor 19 is turned on for ignition, the The electric charge is supplied to a part of the coil 18 of the ignition coil 17 through the thyristor 19 and the varistor 36, but at this time, part of the current passes through the diode 43 and is then supplied to the capacitor 3.
5. The current is shunted to a series circuit of a thermistor 37 and a resistor 38, and a variable resistor 39. and capacitor 35
Since some current flows through the capacitor 35, this capacitor 35 is charged as shown in FIG. 3E or FIG. 4E. The charge stored in the capacitor 35 flows through the resistor 45, the gate and cathode of the thyristor 19, the gate and cathode of the thyristor 19, the varistor 36, and the capacitor 35 in this order, and is discharged. When the engine speed is low, the charging voltage of the capacitor 35 is also low, so before the exciter coil 10 generates the negative output E3'', the voltage of the capacitor 35 is changed to the thyristor as shown in FIG. 3E. Therefore, the thyristor 34 is not turned on by the negative output E3 of the exciter coil 10. However, when the engine speed reaches a predetermined speed,
As shown in FIG. 4E, the voltage of the capacitor 35 is maintained at a voltage higher than the gate trigger voltage VO3 of the thyristor 34 until the exciter coil 10 produces a negative output E3. is made conductive by the negative output E3 of the exciter coil 10. When the thyristor 34 becomes conductive due to the rising of the output E3 in the negative direction of the exciter coil 10 as the engine speed increases, the exciter coil 1
The negative output E3 of 0 is applied to the gate of the thyristor 19 through the anode and cathode of the thyristor 34, and this thyristor 19 is connected to the exciter coil 1.
The conduction occurs at the timing of the rise of the output E3 in the negative direction of 0 to perform the ignition operation. Therefore, as shown in FIG. 4B, the angle is advanced by an angle of 01. This advance angle operation is shown in FIG. In this way, at a normal rotation speed, ignition is performed at an ignition angle commensurate with the normal rotation speed. Next, the operation of preventing overrun when the engine is running at speed will be explained. This overrun prevention operation is achieved by the retard circuit 13 shown in FIG. Exciter coil 1 for charging the capacitor 15
The zero positive output E2 is supplied to a capacitor 26 through a diode 28, and this capacitor 26 is also charged. The time constant of this capacitor 26 is constant, and therefore the time during which the thyristor 24 whose gate is connected to this capacitor 26 is conductive is also constant. When the engine speed does not reach the overrun region, as shown by the solid line in FIG. 3C or FIG. 4C, the capacitor 26 The charging voltage becomes lower than the gate trigger voltage VO2 of the thyristor 24. Therefore, due to the negative direction output E3 of the exciter coil 10? The lever thyristor 24 is never conductive. On the other hand, when the engine speed reaches the overrun region, the charging voltage of the capacitor 26 is maintained at the thyristor 24 until the exciter coil 10 generates a negative output E3, as shown by the dotted line in FIG. 4C. is held at a value greater than or equal to the gate trigger voltage Vg2, and the thyristor 24 is rendered conductive. Then, a part of the current due to the negative voltage of the exciter coil 10 flows in this order from the exciter coil 10 to the resistor 25, the anode of the thyristor 24, the cathode, the diode 33, and the exciter coil 10. The current supplied to the gate of is reduced. When the thyristor 24 becomes conductive and some of the current is shunted through the thyristor 24, the current flowing through the thyristor 34 to the gate of the thyristor 19 decreases, and the current between the gate and cathode of the thyristor 19 decreases. The voltage increases from the state shown by the solid line to the state shown by the dotted line in FIG. Therefore, the angle until the gate trigger voltage g1 applied to the gate of the thyristor 19 is reached is delayed by θ2. Therefore, as shown in FIG. 2, in the overrun region, the ignition timing is retarded stepwise to a state that is further delayed than the ignition timing in the low rotation speed region. In this way, in the engine equipped with the ignition device according to this embodiment, the ignition angle at the time of startup is retarded than the ignition timing set at the normal rotation speed. It becomes possible to prevent this. In addition, the rotation of the idle link becomes stable, making it possible to lower its rotation speed, thereby reducing fuel consumption during idling and reducing vibration during idle link. Furthermore, at a rotation speed that has passed the idle link time,
Since the angle is advanced in steps, it is possible to expect ignition operation commensurate with the rotation speed within the normal rotation range, making it possible to fully demonstrate the engine's performance. Furthermore, when the engine speed increases and reaches the overrun region, the ignition angle is further delayed in steps compared to the ignition timing in the low speed region, thereby reliably suppressing overrun. becomes possible. In particular, since overrun prevention is achieved using an ignition device consisting of such an electronic circuit, the size does not increase even if the overrun prevention function is added, and it is lightweight and maintains a stable control speed. can do. Furthermore, according to such a configuration, the fuel
Engine acceleration is not impaired compared to overrun prevention using a fuel-rich carb setting. Next, when we applied the ignition system shown in Fig. 1 to a 4Qcc 2-night mower engine and delayed the ignition angle by 10 degrees at low speeds, the maximum vibration during idling was reduced from 13G to 4G. The average value of vibration was also reduced from 7-8G to 2G. We also gradually lowered the engine speed during idling and examined the dead slow speed, which is the lower limit of engine speed at which the engine could operate continuously, and found that it dropped from 2,500 to 2,000. Also, the fuel flow rate during idling is 0.18. e/h to 0.15β/h.

【Effect of the invention】

As described above, the present invention includes a means for delaying the ignition timing in a low rotational speed region, a means for advancing the ignition angle in steps when an arbitrary predetermined rotational speed is reached in the process of increasing the rotational speed, A means is provided for delaying the ignition timing further in steps than the ignition timing in the low engine speed range when the engine speed reaches the overrun range. Therefore, according to the present invention, it is possible to prevent engine failure during startup, reduce fuel consumption by lowering the idle link rotation speed, and furthermore prevent engine overrun.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an ignition system used in a spark ignition engine according to an embodiment of the present invention, Fig. 2 is a graph showing the characteristics of this ignition system, and Fig. 3 is a graph showing the characteristics of this ignition system when the engine speed is low. FIG. 4 is a graph showing the ignition operation when the engine speed increases, and FIG. 5 is a graph showing the overrun prevention operation. In addition, in the symbols used in the drawings, 10... Exciter coil 11... Rotor 12... Magnet 13... Retard circuit 15... Capacitor 17... Ignition coil 18... - Secondary coil 19 ... Thyristor 21 ... Advance angle circuit 22 ... Secondary coil 23 ... Spark plug 24 ... Second thyristor 26 ... Capacitor 27 ... Resistor 34 ... Third thyristor 35... Capacitor 41... Capacitor 42... Resistor. Placement) Mouth, cheek, and armpit

Claims (1)

[Claims] In an engine in which a spark is generated by an ignition device, the spark ignites and causes a combustion explosion, thereby obtaining output, there is a means for delaying the ignition timing in the low rotation speed region, and a means for delaying the ignition timing in the process of increasing the rotation speed. means for advancing the ignition angle in steps when the engine speed reaches an arbitrary predetermined rotation speed, and means for advancing the ignition timing in steps further than the ignition timing in the low rotation speed region when the engine speed reaches an overrun region. A spark ignition engine characterized in that the spark ignition engine is provided with a means for delaying the time.