JPH0114765Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a non-contact ignition device for an internal combustion engine for automatically adjusting the ignition timing of the internal combustion engine according to the engine speed.

[Conventional technology]

In an ignition system for an internal combustion engine, a compressed air-fuel mixture in a cylinder is ignited by an electric spark, causing combustion in the cylinder and generating power for reciprocating a piston. Such ignition devices include a battery type, a magneto type, etc. Among these, a variety of non-contact ignition devices as shown in FIG. 1 are provided as the magneto type.

This non-contact ignition device is attached to a small general-purpose internal combustion engine and has a simple structure as a whole. 1st
In the figure, 1 is a rotor that constitutes a generator, which is attached to the rotating shaft of the engine, and includes magnets 3, 4 and a pole piece 5 on a non-magnetic material 2 made of aluminum, for example.
The outer peripheral surfaces of the pole pieces 5, 6, and 7 are exposed on the outer peripheral surface side of the non-magnetic material 2, and form an arcuate surface that is continuous with the arcuate surface of the pole pieces 5, 6, and 7. . Further, the magnets 3 and 4 are connected to each pole piece 5, 6, and 7 such that the center pole piece 6 has a different polarity from the pole pieces 5 and 7 on both sides.

Reference numeral 8 denotes a power generation section provided near the rotor 1, and a leg 9a on the rotor rotation direction side, which is one of the U-shaped cores 9.
It consists of a generator coil 10 wound around the coil. That is, the power generating coil 10 is wound around the leg 9a on the opposite side to the leg 9b on the side where the pole piece 5 first faces in the rotational direction of the rotor 1.

An ignition control circuit 11 is connected to both ends of the generator coil 10. This ignition control circuit consists of diodes 12, 13, 14, 15, a thyristor 16 as a first switching element, a first capacitor 17, and an ignition coil 18 connected as shown in the figure. A spark plug 19 is connected to the ignition plug 19 .

The first capacitor 17 is used to charge the positive voltage induced in the power generating coil 10. Further, the thyristor 16, which is the first switching element, becomes conductive in response to a trigger voltage based on the negative voltage induced in the power generating coil 10.
The charge stored in the first capacitor 17 is discharged through the primary coil of the ignition coil 18.

[Problem that the invention attempts to solve]

In such a non-contact ignition system, when the rotor 1 rotates in the direction of arrow X due to engine operation, a voltage having a waveform shown by a solid line P in FIG. 2 is induced in the generator coil 10 in a low speed rotation range. When a positive direction voltage is obtained among this induced voltage, the diode 13, capacitor 17, and ignition coil 18
A positive current is caused to flow through the primary coil and the ground to charge the capacitor 17. When the induced voltage becomes the second negative voltage, current flows through the gate/cathode of the thyristor 16 and the path of the diode 12, and the trigger level voltage V _T of the thyristor 16 is changed to the negative voltage. reaches at θ ₁ , thyristor 1
6 becomes conductive, discharging the charge in the capacitor 17 through the anode/cathode of the thyristor 16 and the diode 14 to the primary side of the ignition coil 18, inducing a high voltage on the secondary side, and producing the desired ignition spark. This is caused to occur at the plug 19.

By the way, the ignition timing of a small general-purpose internal combustion engine is
The angle is set approximately 30 degrees before top dead center in consideration of combustion pressure and heat loss in the exhaust gas, thereby achieving maximum output and optimum fuel efficiency.

However, if ignition occurs at the above ignition timing in a low-speed operating range such as when starting or warming up the engine, combustion due to early ignition will generate combustion pressure during the compression process, creating a force that tends to reverse rotation. As a result, vibration, vibration noise, and exhaust noise become significant, and various mechanical loads are imposed on the rotation transmission system, which is not preferable. In addition, if the ignition timing is delayed and the ignition is ignited 5° to 10° before top dead center, heat loss in the exhaust stroke in medium and high-speed operating ranges will increase, making it impossible to obtain sufficient output. This will lead to deterioration in fuel efficiency and acceleration performance.

On the other hand, in the high-speed operation range of the engine, the induced voltage waveform of the generator coil 10 becomes like a dotted line Q, which is an induced voltage waveform that lags behind the solid line P in the low-speed operation range, as shown in FIG. This is due to the influence of magnetomotive force due to the current induced in the generator coil 10, that is, the influence of armature reaction.

The influence of this armature reaction is more significant at the second negative voltage 'immediately after the positive voltage' than at the first negative voltage 'immediately before the positive voltage'.

Therefore, when the thyristor 16 is triggered by this second negative direction voltage', the ignition timing at high speed is significantly delayed by θ ₂ compared to at low speed. As a result, there have been problems in that engine output in high-speed driving ranges is reduced and fuel efficiency is significantly reduced. Curve A in FIG. 3 is an ignition timing characteristic diagram showing such a delayed ignition timing situation.

The present invention has been devised by focusing on these conventional problems.

This invention prevents delays in ignition timing due to armature reaction when the engine is running at high speeds, and automatically advances the ignition timing from low to medium speeds. It is an object of the present invention to provide a non-contact ignition device for an internal combustion engine that maintains substantially constant ignition timing from 1 to 3 in a high-speed rotation range.

[Means to solve the problem]

In order to achieve the above object, the present invention consists of a rotor having at least two or more pole pieces of which adjacent pole pieces have different polarities, and a U-shaped core arranged around the rotor and around which a power generating coil is wound. A generator in which the above-mentioned pole piece on the rotor rotation direction side is extended in the rotation direction side compared to the pole piece on the opposite side to the rotor rotation direction, and the buried depth with respect to the rotor is gradually deepened, and the above-mentioned power generation A first capacitor and a second capacitor that charge the positive voltage induced in the coil are electrically connected in response to a trigger voltage based on the negative voltage induced in the generator coil, and the charge charged in the first capacitor is ignited. a first switching element for discharging the electric charge of the second capacitor through the primary coil; a discharging circuit for discharging the charge of the second capacitor at a predetermined time constant; a second switching element that discharges the charge of the capacitor in a short time; and a second switching element that receives the discharge voltage of the second capacitor and becomes conductive to bypass the trigger voltage of the first switching element; and a third switching element that makes the switching element conductive.

〔Example〕

FIG. 4 is a circuit diagram of a non-contact ignition device showing an embodiment of the present invention, and the same components as those shown in FIG.

21 is a Zener diode connected between the anode of the diode 12 and the cathode of the thyristor 16.

22 is a diode, 23 is a resistor, 24 is a second capacitor, and 25 is a diode, which together with the generating coil 10 constitute a series connection circuit. Note that the second capacitor 24 is used to charge the positive voltage induced in the generator coil 10. A thyristor 26 is a third switching element. The anode of the thyristor 26 is grounded, the cathode is connected to the midpoint C between the second capacitor 24 and the diode 25, and the gate is connected to the resistor through a resistor 27. 23 and the second capacitor 24, and a discharge circuit is connected between the resistor 27 and the gate and cathode of the thyristor 26 to discharge the charge of the second capacitor 24 at a predetermined time constant. It consists of Therefore, the thyristor 26 is made conductive upon receiving the discharge voltage of the second capacitor 24. Note that the above time constant is set to be relatively large. 28 is a thyristor which is a second switching element, its anode is connected to the connection midpoint D, its gate is connected to the connection midpoint C, and the cathode of this thyristor 28 is connected to the gate via a diode 29 and to the zener. Each is connected to the anode of the diode 21. That is,
The thyristor 28 is configured to discharge the charge of the second capacitor 24 in a short time with priority over the discharge circuit when it is conductive, and the thyristor 28 is configured to discharge the charge of the second capacitor 24 in a short time with priority over the discharge circuit.
The thyristor 26, which is a switching element, is connected to the thyristor 16, which is a first switching element, when conductive.
The trigger voltage is bypassed through the anode/cathode of the thyristor 26 -> the gate/cathode of the thyristor 28 -> the diode 12, and the thyristor 28, which is the second switching element, is made conductive during the bypass.

On the other hand, the pole piece 5A embedded in the non-magnetic material 2
has an extended portion 5a, a part of which is extended in the direction of rotation of the rotor 1, and this extended portion 5a is buried gradually deeper toward the center of the rotor as it approaches the tip. Note that the length, shape, and thickness of this extension portion 5a can be set arbitrarily, and by doing so, the waveform of the voltage induced in the power generating coil 10 can be made to rise slowly with an arbitrary tendency. .

[Effect]

In the low-speed operating range of the engine, the rotation of the rotor is also slow, and the induced voltage obtained in the generator coil 10 at this time is as shown by the curve R shown in FIG. 13 → capacitor 17 → the primary coil of ignition coil 18, and the capacitor 17 is charged.At the same time, current also flows through the path of diode 22 → resistor 23 → capacitor 24 → diode 25, and the capacitor 24 is charged. Charging is performed.For this reason, a trigger current is also applied to the gate of the thyristor 26 via the resistor 27, and the thyristor 26 is turned on.

Eventually, the charge in the capacitor 24 is discharged through the path from the resistor 27 to the gate and cathode of the thyristor 26. However, the discharge time constant at this time is selected to a value that keeps the thyristor 26 turned on until the second negative direction voltage is generated even when the engine speed is low.

Next, a second negative voltage is applied to the generating coil 10.
is induced, but since the thyristor 26 is kept turned on by the above-mentioned time constant, the negative current flows through the path of the anode/cathode of the thyristor 26 → the gate/cathode of the thyristor 28 → the diode 12. Therefore, the Zener diode 21 does not break over and the potentials between the gate and cathode of the thyristor 16 become approximately equal, and the trigger voltage of the thyristor 16 is eventually bypassed, so that the thyristor 16 cannot be turned on.

Furthermore, since the thyristor 28 is turned on at this time, the residual charge in the capacitor 24 is discharged along the path from the anode/cathode of the thyristor 28 to the diode 29.

Thus, at the time when the second negative direction voltage is obtained, the thyristor 16 is not triggered and the ignition voltage is not supplied from the capacitor 17 to the ignition coil 18. Note that FIG. This shows the waveform of the induced voltage assuming a load, and when the second negative direction voltage is obtained, it is actually around 0V.

Next, the first negative direction voltage is applied to the generating coil 10.
, the capacitor 24 already has no charge and the thyristor 26 is off, so a negative current flows through the path from the gate/cathode of the thyristor 16 to the Zener diode 21 to the diode 12. At this time, the thyristor 16 is turned on. Therefore, the charge in the capacitor 17 is discharged in the path from the anode/cathode of the thyristor 16 to the diode 14 to the primary coil of the ignition coil 18, and a high voltage is induced in the secondary coil of the ignition coil 18. Produces a spark at the spark plug. The trigger timing of the thyristor 16 at this time is θ ₃ in FIG. 5a, and the charging/discharging voltage waveform and timing of the capacitor 17 are as shown in FIG. 5b.

Similarly, when the engine is operated in a high-speed range, an induced voltage S that lags behind the induced voltage R described above is obtained, but at this time, the second negative voltage shown by the dotted line with a large lag is not obtained, but due to the armature reaction. Since the thyristor 16 is triggered by the first negative direction voltage which is not affected by the above, it is possible to solve the problem that the ignition timing is delayed when the engine is operating at high speed. Note that the trigger timing of the thyristor 16 at this time is θ ₄ in FIG. 5a.

By the way, the pole piece 5A has an extension part 5a. Therefore, in the low speed rotation range of the engine, the first negative direction voltage has a waveform with a slow rise depending on the length and depth of the extension portion 5a of the pole piece 5A. As the rotation speed gradually increases from the rotation range, the level of the induced voltage in the generator coil 10 increases accordingly.
The rise of the negative voltage gradually becomes steeper as the rotational speed of the engine increases, and becomes steeper in the high-speed rotational range as shown in FIG. 5a. On the other hand, since the trigger level V _T of the thyristor 16 is constant in any rotation range, the ignition timing advances from θ ₃ to θ ₄ in Fig. 5a from the low speed range to the high speed range of the engine. The rate at which the ignition timing is advanced is greater in the lower speed range.

Therefore, the engine speed gradually increases until it reaches around medium speed, and remains approximately constant above that speed. Curve B in FIG. 3 shows such ignition timing characteristics. In this way, optimal ignition timing can be obtained depending on the engine speed, and it is possible to improve engine output and fuel efficiency.

In the above embodiment, when the generating coil 10 is wound around the leg 9b of the core 9 on the side opposite to the rotor rotation direction, the generating coil 10 has a level higher than the second negative direction voltage. A sufficiently large first negative voltage can be obtained. Therefore, the thyristor 16
By setting the trigger to a level that makes it possible with the first negative voltage but impossible with the second negative voltage, the aforementioned delay in trigger timing due to armature reaction during high-speed operation can be easily avoided. can be prevented,
The ignition control circuit for canceling the second negative voltage as described above becomes unnecessary.

However, even when the generating coil 10 is provided on the leg 9b, the first and second negative direction voltage levels become approximately equal due to the shape and dimensions of the core 9 or the arrangement of the pole pieces 5A, 7. In such a case, the second negative voltage cancel ignition control circuit of the present invention is required, and by using this, the original purpose can be achieved.

In this way, among the voltages induced by the generator coil 10, the positive direction voltage is used to charge the capacitor 17,
By using the first negative direction voltage as a control signal for discharging the capacitor 17, it is possible to eliminate the delay in discharging timing due to the armature reaction that occurs in the generator coil when the engine is running at high speed. By forming the extension part 5a,
Without installing a special advance control circuit, the ignition timing can be delayed in the engine's low-speed operating range, and ignition timing can be appropriately advanced in the medium-high speed operating range, ensuring optimal output and control over the entire engine operating range. This provides fuel efficiency.

[Effect of idea]

As explained above, according to the present invention, it is possible to avoid delays in ignition timing in the high speed range due to the influence of armature reaction, and also to delay the ignition timing at low engine speeds and adjust the ignition timing appropriately at medium and high speeds. This means that the ignition timing in the steady-state operating range can be automatically optimally adjusted from the time the engine is started.

Further, the structure for obtaining such effects is simple and inexpensive, and can be made compact, so it is extremely useful when installed in a machine tool having a small engine such as a chainsaw.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a conventional non-contact ignition device, Figure 2
Figure 3 is a diagram of the induced voltage waveform of the generator coil, Figure 3 is an ignition timing characteristic diagram, Figure 4 is an explanatory diagram of the non-contact ignition device of the present invention, and Figure 5 is the voltage waveform of each part of the circuit of the non-contact ignition device. It is a diagram. DESCRIPTION OF SYMBOLS 1... Rotor, 5A, 6, 7... Pole piece, 5a... Extension part, 8... Power generation part, 9... U-shaped core, 9a, 9b... Legs, 10... Power generation coil, 16... ...Thyristor as a first switching element, 17...First capacitor, 24...Second
26... a thyristor as a third switching element, 28... a thyristor as a second switching element.

Claims (1)

[Scope of utility model registration request] A rotor having at least two adjacent pole pieces of different polarities, and a U-shaped core arranged around the rotor and wrapped with a power generating coil, the pole piece being located on the side in the rotational direction of the rotor. A generator in which the pole piece is extended in the rotation direction side compared to the pole piece on the opposite side to the rotor rotation direction and the buried depth with respect to the rotor is gradually deepened, and the generator coil is charged with a positive direction voltage induced in the generator coil. A first capacitor and a second capacitor are connected to each other in response to a trigger voltage based on a negative voltage induced in the power generation coil, and discharge the charge in the first capacitor through the primary coil of the ignition coil. a discharging circuit that discharges the charge in the second capacitor at a predetermined time constant; and a second switching element that discharges the charge in the second capacitor in a short time with priority over the discharge circuit when conductive. In response to the discharge voltage of the second capacitor, the switching element of No. 2 is electrically connected to the first switching element of the second capacitor.
A non-contact ignition device for an internal combustion engine, comprising a third switching element that bypasses the trigger voltage of the switching element and makes the second switching element conductive during the bypass.