JPS6140463A - Self-trigger type ignition device - Google Patents

Abstract

PURPOSE:To prevent an engine from keeping up its reverse rotation in time of starting, by installing a magnet and a pair of magnetic poles at the rotor side, while installing the magnet and a pair of yokes at the fixed side, and setting each magnetic range of these magnetic poles to the specified size. CONSTITUTION:A magnet 4 and a pair of magnetic poles 3 are installed at the rotor side. A pair of yokes 7 having a leg each are installed at the fixed side. A coil 8 is rolled on each yoke. A magnetic range is formed into structure to which the next expression comes into existence thetaP1>thetaY1, thetaP2<=thetaY1, and in time of regular rotation, the side of a magnetic pole 3a wide in a magnetic range is constituted to be set to the inlet side of a leg part 7a of the yoke 7 while the side of a magnetic pole 3b narrow in the magnetic range to the outlet side of a leg part 7b, respectively. Thus, continuation of reverse rotation in time of engine starting is preventable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a self-trigger type ignition device for an engine, and more particularly to an ignition device designed to prevent reverse rotation when starting the engine.

(Prior art) Compared to conventional ignition devices, a self-trigger type ignition device does not require a special signal generation coil, and the armature winding of the generator is shared on the primary side of the ignition coil. Because of its simple and compact structure, it is used as an ignition device for small general-purpose engines, especially two-stroke engines.

The self-trigger ignition system is activated when the engine is running normally as shown in Figure 5 (
A voltage Va having a waveform as shown in a) is output, and ignition is made at a point P where the negative voltage -Va reaches approximately the peak point. However, if the engine reverses due to kickback during startup, etc., the situation shown in Fig. 5 (b)
), the voltage vb has a waveform opposite to the voltage Va, and the end Q reaches approximately the peak point of the first negative voltage -vb.
ignition occurs, and as a result, the engine may continue to rotate in reverse.

An ignition device that prevents reverse rotation of the engine during startup is equipped with a magnet and a pair of poles on the rotor side, a U-shaped iron core with a pair of legs on the fixed side, The magnetic resistance in the magnetic path on the other leg side of an engine transistor ignition device comprising an ignition coil inserted into one leg of the engine is increased, and the primary coil of the ignition coil is An ignition device has been proposed in which the flowing current is reduced and ignition is disabled (Utility Model Application Laid-Open No. 58-114458).

However, the above-described ignition device has problems such as difficulty in adjusting the magnetic resistance of the legs of the U-shaped iron core and poor assemblability.

(Object of the Invention) The present invention has been made in view of the above points, and includes reducing the negative voltage on the side that contributes to ignition among the voltage signals generated when the engine rotates in reverse to disable ignition. The purpose is to increase the negative voltage on the side that does not contribute to ignition to actively discharge energy and prevent ignition from continuing during reverse rotation.

(Summary of the Invention) In order to achieve the above object, the present invention includes a magnet that generates a radial magnetic field on the rotor side, and a pair of magnetic poles arranged on both sides of the magnet with respect to the rotational direction of the rotor. A self-trigger ignition system for an engine, comprising: a yoke having a pair of legs on a fixed side that can face the magnet and each magnetic pole; and an ignition coil wound around the yoke. The width of the magnetic pole along the direction of rotation of the magnetic pole located forward in the direction of rotation with respect to the magnet is made wider than the width of the magnetic pole along the direction of rotation of the magnetic pole located at the rear of the direction of rotation, so that when the rotor reverses rotation, the width of the magnetic pole is greater than the width of the magnetic pole along the direction of rotation of the magnet. To provide a self-trigger ignition device for an engine that discharges the energy of an ignition signal at a timing that does not contribute to the continuation of ignition.

(Example of the invention) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a self-trigger ignition device to which the present invention is applied, in which a flywheel 2 fixed to one end of a crankshaft 1 of an engine is formed of a non-magnetic material such as aluminum, and a predetermined location on its circumferential surface 2a is shown. An arcuate notch 2b of a predetermined length along the circumferential direction is concentrically formed in the notch 2b.
A substantially U-shaped yoke 3 made of a magnetic material such as iron is fitted in the yoke 3 . A magnet 4 is disposed between the legs 3a and 3b of the yoke 3, and one end surface 4a is crimped and fixed to the opposing surface 3c of the yoke 3. This magnet 4 has end faces 4a and 4b each forming a magnetic pole, and generates a magnetic field in the radial direction of the flywheel 2. Therefore, for example, when the end surface 4b of the magnet 4 is the N pole and the end face 4b is the S pole,
The legs 3a and 3b of the yoke 3 both serve as south poles. Therefore,
The legs 3a and 3b are hereinafter referred to as magnetic poles. these yokes 3
The circumferential surface of each magnetic pole 3a, 3b and the circumferential surface 4b of the magnet 4
is flush with the circumferential surface 2a of the flywheel '2. Further, the flywheel 2 is also used as a rotor.

Circumferential width θP 1 rθ of magnetic poles 3a and 3b of yoke 3
P2 is different, and the width θP1 of the magnetic pole 3a located in front of the magnet 4 is different from the width θP1 of the magnetic pole 3b located in the rear of the magnet 4 with respect to the forward rotation direction shown by the arrow C of the flywheel 2.
is set wider than the width θP2 (θP1>θP2),
There is a predetermined width θN1 between each of these magnetic poles 3a, 3b and the magnet 4. Gaps 5 and 5' of θN2 (=θN1) are provided.

Incidentally, a nonmagnetic member may be interposed in each of these gaps 5, 5'', or the gaps may remain as they are.

The yoke 7 of the ignition coil 6 has a substantially U-shape,
Both end surfaces 7a and 7b are arranged to face and be spaced apart from the circumferential surface 2a of the flywheel 2 at a predetermined interval.
The magnetic poles 3a and 3b of the yoke 3 and the magnet 4 are arranged so as to be able to face each other when the yoke 3 rotates. A coil 8 is wound around the central portion 7c of the yoke 7. Each leg 7a of this yoke 7.

Width θYllθ along the rotational direction of the flywheel 2 of 7b
Y2 and both legs 7a, ? The interval θY between b.

Circumferential width θM1 of magnetic pole 4b of magnet 4 and width θpi, θP2 of each magnetic pole 3a, 3b of yoke 3 Air gap 5
, 5" widths θNl and θN2 are set as follows.

That is, 0758M...(1) θN+
=θN2≦θYl =θY2...(2) Above formula (1)
, Under the condition of (2), the following formula, -θP1>θY1
(=θY2) ... (3) θP2≦θyt (
=θY2)...A structure is formed in which (4) holds true.

Moreover, as described above, when the flywheel 2 rotates in the forward direction shown by arrow C, the magnetic pole 3a side with the wide magnetic pole width is the entry side of the leg 7a of the yoke 7, and the magnetic pole 3b side with the narrow magnetic pole width is the exit side of the leg 7b. Configure.

With this configuration, when the flywheel 2 rotates normally (in the direction of arrow C), a voltage Va having a waveform as shown in FIG. The voltage +Val becomes larger than the positive voltage +Va3 on the extraction side by the magnetic pole 3b. Further, when the flywheel 2 is reversed, the voltage vb generated in the coil 7 changes as shown in FIG. It becomes larger than the negative voltage -Vb on the input side.

By the way, the ignition timing zone in which reverse rotation is possible for a two-stroke engine generally ranges from BTDC 130° (reverse direction) to ATDC 30" (as shown by diagonal lines in Fig. 3 ('e)).
(reverse direction). On the other hand, in the ignition system of the present invention, the forward rotation ignition timing is set to BTDC as shown in FIG. 3(d).
20", the reverse ignition timing is as shown in Figure 3(e), (
As shown in f), ATDC is around 70° (reverse direction), which is significantly outside the reversible ignition timing zone.

FIG. 2 shows the circuit configuration of the ignition device of the present invention, in which each end of the primary coil 8a of the coil 8 of the ignition coil 6 is connected to a line 20, 21, and each end of the primary coil 8a of the coil 8 of the ignition coil 6 is connected to a line 20, and each of the transistors Trt+Trz of the ignition unit 10 is connected to the line 20. emitter is connected,
The base of transistor 7r2 is connected to the connection point of resistors R2 and R3 of a voltage divider circuit connected in series between lines 20 and 21. The collector of the transistor Trl is connected to the line 21, the collector of the transistor Tr2 is connected to the line 21 via the resistor R1, and the base of the transistor Tr is connected to the line 21.
Connected to the collector of l'r2. One end of the secondary coil 8b of the coil 8 is connected to one end of the spark plug 11, and the second
The other ends of the secondary coil 8b and the spark plug 11 are connected to wires 21, respectively.
, and the line 21 is grounded.

Next, the operation will be explained.

When the flywheel 2 rotates forward, when the voltage Va is generated in the primary coil 8a of the coil 8, the voltage +Va1 (
If the situation shown in Fig. 3(a) occurs, the transistor "
, +Tr2 are both turned off, and the ignition unit 10 does not operate. Next, when the voltage -Va2 at which the collector side of the transistor Tr becomes a positive potential, the transistor Tr
Trl is turned on, and a primary current 1a (Fig. 3(b)
) flows. When the collector-emitter potential of the transistor Tr gradually rises and the base voltage of the transistor Tr2 divided by the resistors R2+R3 reaches the trigger voltage,
The transistor Tr2 is turned on, the transistor Tr1 is turned off, and the primary current I of the primary coil 8a of the coil 8 is
a is interrupted (FIG. 3(b)), and as a result, a high voltage pulse Vp (FIG. 3(C)) is applied to the secondary coil 8b of the coil 8.
) is induced to cause the spark plug 11 to generate a spark. The ignition timing zone at this time is BTDC 20° as shown in FIG. 3(d).

Voltage + at which the emitter side of transistor Tr1 has a positive potential
When Va3 (FIG. 3(a)) is reached, the ignition unit 10 becomes inoperative as described above.

Now, when the engine starts, the flywheel 2 rotates in reverse and the voltage V shown in FIG. 3(f) is applied to the primary coil 8a of the coil 8.
When voltage -V b t is generated such that the collector side of the transistor Tr1 has a positive potential, the transistor Tr1 is turned on and the primary coil 8a of the coil 8 is turned on.
A primary current 1b (FIG. 3(g)) flows through. However, since the voltage -vb at this time is low, the transistor T
r2 is on.

In other words, the voltage level at which the primary current Ib is cut off is not reached, and no high voltage is generated in the secondary coil 8b. Next, the voltage −v at which the collector side of the transistor Trl becomes a positive potential
When b3 (FIG. 3(f)) is generated, first the transistor Tr is turned on and the primary current Ib flows through the primary coil 8a.
flows. Voltage at this time = ■ b3 is the transistor T
The voltage is sufficient to turn on r2, and the transistor T
When r2 is turned on, the transistor Tr is turned off, the primary current rb is cut off (Fig. 3 (g)), and a high voltage pulse Vp' (Fig. 3 (h)) is induced in the secondary coil 8b. , causing the ignition brush 11 to generate a spark. The ignition position at this time is the waveform position on the side where the magnetic pole 3a is removed as shown in Fig. 1, and as shown in Fig. 2 (e), it is close to ATDC 70° and is sufficiently far from the reversible ignition timing zone. , there is no possibility of reversal.

FIG. 4 shows another embodiment of the present Bonmei, in which the flywheel 2
' is made of a ferromagnetic material such as iron, and the magnet mounting notch 2b' and the magnetic poles 2c'' and 2d'' are integrally formed. In this case, each magnetic pole 2c".

2d'', the radius r of the outer circumferential surface of each magnetic pole 2c'', 2d'' is set to be larger ((r>r'') than the radius r'' of the outer circumferential surface 2a'' forming the step.

(Effects of the Invention) As explained above, according to the present invention, when the rotor rotates forward, the magnetic pole width along the rotational direction of the magnetic pole located in the front of the magnet in the rotational direction is changed in the rotational direction of the magnetic pole located in the rear of the rotational direction. When the rotor reverses, the ignition coil's energy is actively discharged in the ignition timing zone where it cannot be reversed, and ignition is not performed in the ignition timing zone where it is possible to start the engine. It is possible to prevent the clock from continuing to rotate in the opposite direction. In addition, the configuration is simple, just by changing the magnetic pole width, and fI! There are advantages such as there is no adjustment point and the ease of assembly can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the self-trigger ignition device for an engine according to the present invention, FIG. 2 is a circuit diagram showing an example of an ignition circuit, and FIG. 3 is a rotor diagram of the circuit diagram shown in FIG. 2. FIG. 4 is a diagram showing the configuration of another embodiment of the present invention, and FIG. 5 is a graph showing voltage waveforms of a conventional self-trigger ignition device. be. 1... Crankshaft, 2.2'... Flywheel,
3...Yoke, 4...Magnet, 6...Ignition coil, 7...Yoke, 8...Coil, 1
o...Ignition unit, 11...Spark plug. Applicant Honda Motor Co., Ltd. Agent Patent Attorney Toshi Watanabe Otoma Kanji Nagato Figure 1 5o'; 1L127

Claims (1)

[Claims] 1. A magnet that generates a radial magnetic field on the rotor side, and a pair of magnetic poles arranged on both sides of the magnet with respect to the rotational direction of the rotor, and the fixed side can face the magnet and each magnetic pole. In the self-trigger type ignition device for an engine, the engine includes a yoke having a pair of legs, and an ignition coil wound around the yoke. A self-trigger type ignition device for an engine, characterized in that a magnetic pole width along the rotational direction of the magnetic pole is wider than a magnetic pole width along the rotational direction of the magnetic pole located at the rear in the rotational direction.