JPH037576Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an engine ignition system, and in particular charges a charging/discharging capacitor with the output of an alternator driven in synchronization with the engine. The charge in this charging/discharging capacitor is discharged through a switching element connected in parallel to the primary coil of the ignition coil, and by cutting off this switching element at a predetermined timing, a current is suddenly caused to flow through the primary coil of the ignition coil. The present invention relates to an ignition device for an engine that performs ignition operation by inducing a high voltage in a secondary coil of an ignition coil.

〓Summary of the invention〓 The present invention is an ignition device that performs ignition operation using a charging/discharging capacitor based on the output of an alternator. In an ignition device that causes a current to suddenly flow through a primary coil of an ignition coil and induces a high voltage in a secondary coil by cutting off an element at a predetermined timing,
By providing a circuit consisting of a diode to short-circuit a current in the opposite direction to the sudden current described above, and by passing current through this circuit so that at least a portion of the primary coil is short-circuited, the engine speed is increased. This is intended to protect the switching element in the event of an accident.

〓Prior art〓 For example, Japanese Utility Model Application Publication No. 55-114359 has an ignition device that uses an alternating current generator and a charging/discharging capacitor. An ignition device has been disclosed in which a current is suddenly caused to flow through the primary coil by interrupting the primary coil, thereby inducing a high voltage in the secondary coil.

That is, as shown in Fig. 4, a charging/discharging capacitor 3 is charged via a diode 2 by the output V ₁ in the negative direction of the exciter coil 1 constituting the alternator, and the charge/discharge capacitor 3 is charged by the charged charge of the capacitor 3. By supplying a base current to the base of the transistor 5 through the resistor 4 and making the transistor 5 conductive, the charge in the charging/discharging capacitor 3 is discharged through the collector of the transistor 5, and a predetermined amount The signal coil 6 makes the thyristor 7 conductive at the timing of , and the transistor 5 is cut off by short-circuiting the base current of the transistor 5. Therefore, in synchronization with the shutoff of the transistor 5, the discharge current of the charging/discharging capacitor 3 suddenly flows into the primary coil 9 of the ignition coil 8. Due to the change in magnetic flux accompanying this change in current, the secondary coil 10 of the ignition coil 8
A high voltage is induced in the spark plug 11, causing the spark plug 11 to perform an ignition operation.

Problems to be Solved by the Invention A drawback of such a conventional ignition device is that the transistor 5 may generate heat or be destroyed. That is, when the engine speed is low, the primary coil 9 of the ignition coil 8
Since the impedance of the ignition coil 8 is low, a current as shown by the arrow 12 flows through the primary coil 9 of the ignition coil 8 due to the negative output V ₁ of the exciter coil 1 . However, as the engine speed increases,
Since the impedance of the coil 9 becomes high, it becomes difficult for the current shown by the arrow 12 to flow, and instead, the current flows between the emitter and the collector of the transistor 5 as shown by the arrow 13. Therefore, the engine speed increases and the output goes in the negative direction.
If the value of V ₁ increases, the rating of the transistor 5 will be exceeded, which will cause the transistor 5 to generate heat or be destroyed.

The present invention was developed in view of these problems, and even if the output of the exciter coil increases as the engine speed increases, the transistor, etc. connected in parallel with the primary coil of the ignition coil An object of the present invention is to provide an ignition device for an engine that prevents a switching element from generating heat or being destroyed.

〓Means for solving the problem〓 The present invention charges a charging/discharging capacitor with the output of an alternator driven in synchronization with the engine, and transfers the electric charge of this charging/discharging capacitor to the ignition coil. By discharging through a switching element connected in parallel with the primary coil and cutting off this switching element at a predetermined timing, a current suddenly flows through the primary coil of the ignition coil, and a high voltage is applied to the secondary coil. In the ignition device, a circuit made of a diode is provided to short-circuit at least a part of the primary coil of the ignition coil, and a current in a direction opposite to the sudden current is short-circuited through the circuit made of the diode. This is what I did.

〓Effect〓 Therefore, according to the present invention, as the engine speed increases, the impedance value of the primary coil to the ignition coil increases, and the current is short-circuited by the circuit consisting of the diode, thereby causing switching. Current can be prevented from passing through the element. Therefore, this makes it possible to prevent the switching element from generating heat or being destroyed.

〓Example〓 An illustrated embodiment of the present invention will be described below.

FIG. 1 shows an ignition system for an engine according to this embodiment. connected in series circuit. Furthermore, the charging/discharging capacitor 16 is connected to the primary coil 19 of the ignition coil 18 . A transistor 20 is connected in parallel to this primary coil 19, and the base of the transistor 20 is connected to a resistor 2.
1 to the connection point between the capacitor 16 and the diode 17. Also, the transistor 20
The base of is connected to the thyristor 22, and the gate of the thyristor 22 is connected to the signal coil 23.
is connected. Further, the secondary coil 24 of the ignition coil 18 is connected to a spark plug 25.

Furthermore, in the ignition device according to this embodiment, the center tap 2 is connected to the primary coil 19 of the ignition coil 18.
A diode 27 is connected between the center tap 26 and one end of the coil 19, thereby forming a short circuit.

In the above configuration, the exciter coil 15 generates output voltages V ₁ and V ₂ as shown in FIG. 2A for each rotation of the engine. On the other hand, the signal coil 23 connected to the gate of the thyristor 22 generates a signal output waveform as shown in FIG. 2B. and exciter coil 15
The charging/discharging capacitor 16 is charged in the negative direction by the output V ₁ via the diode 17 as shown in FIG. 2C. Due to the charge stored in the capacitor 16, a base current is supplied to the base of the transistor 20 through the resistor 21 as shown in FIG. 2D, and the transistor 20 becomes conductive. Therefore, when the output of the exciter coil 15 changes to the positive direction and generates an output of V ₂ , a second voltage is generated between the collector and emitter of the transistor 20.
A collector current as shown in Figure E flows.

However, when the voltage generated in the signal coil 23 exceeds the gate trigger voltage Vg of the thyristor 22,
At this point, the thyristor 22 becomes conductive, and the base current of the transistor 20 is short-circuited by the thyristor 22. This therefore switches the transistor 20 into the cut-off state, and all the current that hitherto was flowing through this transistor 20 now flows through the primary coil 19 of the ignition coil 18. That is, when the output of the signal coil 23 exceeds the gate trigger voltage of the thyristor 22, the transistor 20 is cut off and the current in the primary coil 19 of the ignition coil 18 increases rapidly, as shown in FIG. 2F. Due to the change in magnetic flux accompanying this increase in current, the secondary coil 2 of the ignition coil 18
A high voltage is induced in the spark plug 25, and the spark plug 25 performs the ignition operation.

Then, due to the negative output V ₁ generated by the exciter coil 15, the charge/discharge capacitor 16
At the same time, a current flows through the primary coil 19 of the ignition coil 18 as shown by an arrow 28. Even if the engine speed increases and the impedance of this coil 19 increases, a current as shown by arrow 28 will flow through the short circuit consisting of the diode 27 connected to the center tap 26. This prevents current from flowing in the opposite direction through transistor 20. Therefore, the short circuit formed by such a diode 27 makes it possible to prevent the transistor 20 from being overheated and destroyed. Note that as the engine speed increases, the temperature of the ignition coil 18 increases due to the current 28, but this temperature increase does not pose a particular problem because the heat is dissipated by the iron core.

Next, a modification of the above embodiment will be explained with reference to FIG. In this modification, parts corresponding to those in the above embodiment are given the same reference numerals, and descriptions of parts having the same configuration will be omitted. A feature of this modification is that a transistor 30 is used in place of the thyristor 22, and the transistor 30 is used to cut off the transistor 20. That is, the positive output V ₂ of the exciter coil 15 is divided by a pair of resistors 31 and 32, and this divided voltage is applied to the base of the transistor 30. Therefore, when the positive output V ₂ of the exciter coil 15 reaches a predetermined value, the transistor 30 becomes conductive and the base current of the transistor 20 is bypassed. This therefore switches the transistor 20 into the cut-off state and the ignition coil 1
A current suddenly flows through the primary coil 19 of 8, and the ignition operation is performed in the same manner as in the above embodiment.

Therefore, according to this modification, the thyristor 22 can be replaced with the transistor 30, and the signal coil 23 can be omitted. Also in this modification, the short circuit consisting of the diode 27 connected to the center tap 26 prevents the transistor 20 from generating heat and being destroyed.

Effects of the invention As described above, according to the invention, a circuit consisting of a diode is provided to short-circuit at least a part of the primary coil of the ignition coil, and a current in the opposite direction to the sudden current applied to the primary coil is prevented. A short circuit is created through a circuit consisting of this diode. Therefore, it is possible to prevent current from flowing in the opposite direction to the switching element, thereby preventing heat generation and destruction thereof.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an ignition device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the same ignition device, FIG. 3 is a circuit diagram of an ignition device according to a modified example, and FIG. 4 is a circuit diagram of a conventional ignition device. In addition, in the symbols used in the drawings, 15...exciter coil, 16...charging/discharging capacitor, 1
8...Ignition coil, 19...Primary coil, 20...
...Transistor, 22...Thyristor, 24...
Secondary coil, 26...center tap, 27...diode, 30...transistor.

Claims (1)

[Scope of utility model registration request] A charging/discharging capacitor is charged by the output of an alternator driven in synchronization with the engine, and the electric charge of this charging/discharging capacitor is discharged through a switching element connected in parallel with the primary coil of the ignition coil. Moreover, in an ignition device in which the switching element is cut off at a predetermined timing to cause a sudden current to flow through the primary coil of the ignition coil and to induce a high voltage in the secondary coil, the primary coil of the ignition coil An ignition device for an engine, characterized in that a circuit made of a diode is provided to short-circuit at least a part of the coil, and a current in a direction opposite to the rapid current is short-circuited through the circuit made of the diode.