JPS6410667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a capacitor discharge type ignition device for an internal combustion engine.

For the purpose of preventing overrun and preventing seizure of 2-stroke engines, the rotation speed is set to N ₁ as shown in Figure 1.
Ignition timing characteristics that start more retarded may be required.

To meet these demands, the Japanese Patent Laid-Open Publication No.
As shown in Publication No. 52-3941, there is a known method in which a transistor is connected in parallel with the sensor coil and the transistor is operated at a set rotation speed to reduce the input impedance of the gate circuit, but this method has the following problems. There is.

The circuit configuration becomes complicated, resulting in a significant increase in cost.

It is not possible to obtain a retard width greater than the sensor signal width. (A waveform width greater than the retard width is required.) Therefore, in order to solve the above problem, the present invention connects a series circuit of a resistor and a capacitor in parallel with the sensor coil (before the diode), and The purpose is to satisfy the ignition timing characteristics shown in Figure 1 by retarding the ignition timing by more than the sensor signal width with a simple configuration by applying a negative half wave to the ignition sensor and a positive half wave after an arbitrary angular interval α°. shall be.

The present invention will be described below with reference to embodiments shown in the drawings. In Fig. 2, 1 is a capacitor charging coil, 2 is an ignition capacitor, 3 is an ignition coil, 4 is a spark plug, 5 is an ignition thyristor, 6,
7 and 8 are diodes, and 9 is a sensor coil, which generates one cycle of alternating current signals in the order of negative and positive at intervals of α. (See Figure 3). The structure of the sensor section having this sensor coil 9 is as shown in FIG.
A long protrusion 13 is formed on the outer periphery of the sensor 2 at an angle approximately equal to the signal interval α, and the sensor 16 has a built-in magnet structure.

10 is a resistor (several ohms to several hundred ohms), 11 is a control capacitor (0.1 to several μF), and the resistor 10 sets the time constant for charging and discharging the capacitor 11.

Figure 5 is a structural diagram of the sensor section, where 12 is the rotor, 1
3 is a long protrusion (forms an inductor, and is constructed by stamping or welding a magnetic material to the outer periphery of the rotor 12), 14 is a magnet, and 15 is a sensor core (the magnet 14 and the long protrusion 13 form a magnetic path). ).

In the above configuration, when the rotor 12 rotates and the elongated protrusion 13 faces the sensor core 15, the magnetic flux within the sensor core 15 changes, so that the signal interval becomes smaller than the elongated protrusion 1.
One cycle of signal waveforms with different polarities approximately equal to the angle of 3 are generated in the order of negative and positive. (Figure 3). Point A is negatively biased by charging the control capacitor 11 to the polarity shown (FIG. 2) with the first negative half wave of this sensor signal (waveform a in FIG. 3). The charge stored in the capacitor 11 is discharged at a time constant determined by the inductance and internal resistance of the sensor coil 9, the resistor 10, and the capacitor 11, and the potential at point A returns to 0V.

At low speeds below the retardation start setting rotation speed N ₁ , the charge stored in the capacitor 11 is transferred to the sensor coil 9.
By the time the next positive half wave (waveform b in Figure 3) rises, the electric potential at point A has returned to 0V, so the ignition timing is determined by the position at which the waveform b rises.

When the rotation increases and reaches the retard start setting rotation speed N ₁ , point A is still negatively biased at the start of the b waveform rise, so the b wave rise is delayed and the ignition timing is delayed. make a corner

Furthermore, as the rotation speed increases from N ₁ to N ₂ to N ₄ , the potential at point A at the rise of the b waveform becomes lower and lower as shown in Figure 4, so as the rotation speed increases, the retard angle increases, and the set rotation speed decreases. The ignition timing performance shown in FIG. 1, which is linearly retarded from N ₁ , can be obtained. Here, TL in FIG. 4 indicates the trigger level of the thyristor 5.

The retardation start rotation speed N ₁ and retardation width settings are determined by the interval α between the negative and positive waveforms of the sensor signal (the interval between the a and b waveforms)
That is, this is done by changing the angle of the long protrusion 13 and the discharge time constant of the capacitor 11 (by changing the capacitance of the capacitor 11 and the resistance 11).

In addition, with this method, even if the negative bias at point A is large and the potential at point A does not return to 0V until the end of the no-load voltage waveform of wave b, as shown in N4 in Figure ₄ , the sensor Since a resonant waveform is generated between the inductance of the coil 16 and the capacitor 11, ignition is not disabled, and the retard width is not limited by the sensor waveform width as in the conventional system and can be widened. In experiments, a retardation width of 40° was obtained with the present invention, compared to the 5° retardation width of the conventional system.

In the above-mentioned embodiment, a case is described in which an inductive rotation type sensor is used, but a magnet rotation type sensor in which a magnet 17 is fixed to the outer periphery of a rotor 12 as shown in FIG. 6 may also be used. , can be used as long as the sensor signal waveforms are generated in negative and positive order.

As described above, in the present invention, without using short-circuiting thyristors or transistors, with a simple and inexpensive circuit configuration, the charge of the capacitor charged by the negative direction signal can be used until the end of the no-load waveform of the positive direction signal. Even if the positive side of the sensor coil is biased to negative polarity, a trigger signal can be applied from the sensor coil to the gate of the ignition thyristor via the diode due to the resonance phenomenon between the sensor coil's inductance and the capacitor. This has the excellent effect of being able to obtain a retard width that is greater than the width of the positive direction output signal of the sensor coil.

[Brief explanation of the drawing]

FIG. 1 is an ignition timing characteristic diagram obtained by the device of the present invention, FIG. 2 is an electric circuit diagram showing one embodiment of the device of the present invention, FIG. 3 is a waveform diagram of the output signal of the sensor coil in the above embodiment, and FIG. 2 is a voltage waveform diagram at point A in the illustrated embodiment, FIG. 5 is a partial cross-sectional plan view showing the configuration of the sensor section in the above embodiment, and FIG. 6 is a section showing another embodiment of the above sensor section. FIG. 5... Ignition thyristor, 8... Diode,
9...Sensor coil, 10...Resistor, 11...Control capacitor.

Claims (1)

[Claims] 1 A sensor coil that generates alternating current signals in the order of negative and positive at regular intervals is connected in parallel to this sensor coil via a resistor, and after being charged by the negative direction output of the sensor coil, this charged charge causes the and a capacitor that biases the positive side of the sensor coil to a negative polarity from the rotation speed after the retardation starting rotation speed when a positive direction output is generated in the sensor coil, and the positive side of the sensor coil is connected to the ignition side through a diode. Non-contact ignition device for internal combustion engines connected to the gate of the thyristor.