US3759237A

US3759237A - Igniter for two-cycle multi-cylinder engine

Info

Publication number: US3759237A
Application number: US00191607A
Authority: US
Inventors: G Shino; K Okamoto; K Shimura
Original assignee: Sawafuji Electric Co Ltd
Current assignee: Sawafuji Electric Co Ltd
Priority date: 1971-10-22
Filing date: 1971-10-22
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18

Abstract

An igniter for a multi-cylinder engine comprises a plurality of ignition circuits each consisting of a breaker, an ignition coil and a spark plug. The circuits are connected in series to one another and to one end of an ignition generator coil of an engine driven magneto. The ends of the ignition circuits and the other end of the ignition generator coil are grounded.

Description

Unite States Faieni 1 Shino et al.

1451 Sept. 18,1973

1 1 IGNITER FOR TWO-CYCLE MULTl-CYLINDER ENGINE [76] lnventors: Goro Shino; Katsuyuki Okamoto; Katsumi Shimura, all of Sawafuji Denki Kabushiki Kaisha, l0, 6-chome, Maino-cho, ltabashi-ku, Tokyo, Japan [22] Filed: Oct. 22, 1971 [21] Appl. No.: 191,607

52 us. 121...... 123/148 E, 123/148 R, 123/149 R, 123/148 AC, 123/149 A, 123/148 DC,

51 Int. Cl. F02p 1/00 [58] Field of Search 123/148 R, 148 E, 123/149 R, 149 A,148 AC, 148 DC, 148 DS [56] References Cited UNITED STATES PATENTS 3,576,183 4/1971 Miyamoto 123/148 2,256,907 9/1941 Ochscnbcin 123/149 3,464,397 9/1969 Burson 123/149 2,845,850 7/1958 Kongsted 123/149 2,047,431 7/1936 Randolph 123/148 Primary ExaminerLaurence M. Goodridge Assistant ExaminerRonald B. Cox Attorney-Arthur G. Connolly et a1.

[57] ABSTRACT An igniter for a multi-cylinder engine comprises a plurality of ignition circuits each consisting of a breaker, an ignition coil and a spark plug. The circuits are connected in series to one another and to one end of an ignition generator coil of an engine driven magneto. The ends of the ignition circuits and the other end of the ignition generator coil are grounded.

5 Claims, 4 Drawing Figures PATENTED SEN 8'91! SHEET 1 BF 2 IGNITER FOR TWO-CYCLE MULTI-CYILINDER ENGINE BACKGROUND OF THE INVENTION The present invention relates to an igniter for a twocycle multi-cylinder engine.

There are two types of igniters for a two-cycle multicylinder engine--battery type and flywheel magneto type. In the flywheel magneto type the electric output of the flywheel magneto driven by the torque of the engine is tapped separately for each of the multi-split coils. The alternating electromotive forces generated in the plural coils of the flywheel magneto are each connected to the primary winding of a booster coil of which the secondary winding is connected to the spark plug. Moreover, the coil of the above-mentioned flywheel magneto, a breaker to short-circuit this circuit and a capacitor efiective to prevent the sparks generated with the breaker action from generating a noise radio wave are connected in parallel to the primary winding of the booster coil.

In such conventional igniters there must be as many spark plugs as flywheel magneto coils, and there is no interchangeability between engines designed with different numbers of cylinders. Also, the number of capacitors for noise elimination must be the same as the number of cylinders.

Another drawback to conventional igniters is that when the engine is manually or otherwise rotated in the wrong direction by mistake, the engine continues to run in the wrong direction.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a circuit that makes it possible to apply the same flywheel magneto toseveral types of engines differing in the number of cylinders whereby it is impossible for the engine to rotate in the wrong direction and a single capacitor suffices for noise elimination.

In accordance with the present invention an ignition is provided for a multi-cylinder engine comprising a plurality of ignition circuits each consisting of a breaker and ignition coil and a spark plug. The circuits are connected in series to one another and to one end of an ignition generator coil of an engine driven magneto. The ends of the ignition circuits and the other end of the ignition generator coil are grounded.

Also, a diode may be connected between the ground and the ignition generator coil. Alternatively, the diode may be connected between the ignition generator coil and the plurality of ignition circuits. Moreover, the junction between the ignition generator coil and the plurality of ignition circuits may be connected to one end of a capacitor with the other end of the capacitor connected to a ground.

BRIEF DESCRIPTION OF THE DRAWINGS Novel features and advantages of the present invention in addition to those mentioned above will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing wherein:

FIG. 1 is a schematic elevational view of a flywheel magneto according to the present invention;

FIG. 2 is a wiring diagram for a flywheel magneto according to the present invention;

FIG. 3 is a wiring diagram for another embodiment of the present invention; and

FIG. 4 is a diagram comparing the working principle of the present invention with a conventional device.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity to the drawing, FIG. I illustrates one embodiment of the present invention including a flywheel type magneto I attached to a three-cylinder two-cycle engine (hereinafter referred to as the engine) and driven in synchronism with the engine crankshaft 6, and a main assembly 2 of the flywheel for the magneto I. The main assembly of flywheel 2 is fabricated of magnetic material like iron plate and shaped in the form of a disk.

On the inside cylindrical surface of the main assembly of flywheel 2 there are positioned six magnets 3, each magnetized in the radial direction, together with pole pieces 4 such that magnets with different polarities may be next to one another. Item 5 is a breaker opening and closing cam, and this cam and the above mentioned main assembly of flywheel are fixed to the engine crankshaft 6. A stator plate 7 is attached to the engine crankcase (not shown), and three cores 10, ll, 12 are fitted at equal intervals on the stator plate. Cores 10, II and 12 are respectively attached to the ignition generator coil 8, the charging generator coil 9 and the ignition generator coil 13 in such manner that they may magnetically oppose the six magnets 3 of the above mentioned main assembly of flywheel 2.

Also, on the stator plate 7 are fitted the breakers 17, I8, 19 for the

ignition circuits

30, 31, 32 (shown in FIG. 2) of the first, second and third cylinders; the spark eliminating capacitor 20 for these breakers; and the diode 21. As indicated in FIG. 4 (a) (b) (c), the cam 5 sets the opening crank angles a 01 a of the

breakers

17, 18, 19 at about 60 and the opening positions at about 30 ahead of the crank angles 0 (piston at top dead center) respectively of the first, second and third cylinders of the engine. FIG. 2 is a wiring diagram of the device of one embodiment of the invention in which the first, second and third cylinders of the engine can be ignited in succession at approximately equal intervals by the power generated in the ignition generator coil of the flywheel type magneto 1 shown in FIG. 1. In FIG. 2, 23, 24, 25 denote the three ignition coils provided on the outside of the magneto l and they consist respectively of primary coils 23a, 24a, 25a and secondary coils 2312, 243b, 2512. The primary coils 23a, 24a, 25a are connected to the

breakers

17, 18, I9, and the

secondary coils

23b, 24b, 251; are connected to

spark plugs

27, 28, 29, thereby respectively constituting the

ignition circuits

30, 31, 32 for the first, second and third cylinders. In this manner, the

breakers

17, 18, 19 of the

ignition circuits

30, 3t, 32 are connected in series, one end being grounded and the other end being connected in series to one end of the ignition generator coil 13 of the magneto l. The other end of the ignition generator coil I3 is grounded via the diode 21. One end of the capacitor 20 is connected to the junction between the ignition circuit 30 of the first cylinder and the ignition generator coil 13, and the other end is grounded.

The operation of the device is as follows. Assuming the engine is rotating in the direction of the arrow of FIG. d, the six magnets 3 of the flywheel 2 cause positive voltages V V V and negative voltages V,', V V of the wave forms illustrated in FIG. 4 (d) to be generated in the ignition generator coil 13. Then in the circuit comprising the ignition generator coil i3,

ignition circuits

30, 31, 32 of the first, second and third cylinders and diode 2i, currents flow having wave forms a,, a a as illustrated in FIG. 4 (c), with the negative voltages V V V suppressed by the diode 21 and the generating positions of the currents lagging about 30 behind the generating positions of the positive voltages V,, V V due to the impedance of the ignition generator coil 13. When the time comes for ignition of the first cylinder and the breaker 17 of the ignition circuit of the first cylinder opens at the point (FIG. 4 (2.)), i.e., about 30 ahead of the crank angle of the first cylinder (with piston at top dead center), a current a, having a wave form as illustrated in FIG. 4 (f) flows suddenly in the primary coil 23a of the ignition coil 23. As a result, a high voltage occurs in the secondary coil 23b whereby ignition is effected by a high voltage spark generated in the spark plug 27 of the first cylinder. The breaker 17 closes at the point t, (FIG. 4 (a)), i.e., at about a 30 crank angle of the first cylinder.

Next, when the time comes for ignition of the second cylinder and the breaker 18 for the ignition circuit 31 of the second cylinder opens at the point 2, (FIG. 4 (b)), i.e., about 30 ahead of the crank angle 0 of the second cylinder, a current a having a wave form as illustrated in FIG. 4 (g) suddenly flows in the primary coil 24a of the ignition coil 24. As a result, a high voltage occurs in the secondary coil 24b whereby ignition is efi'ected by a high voltage spark generated in the spark plug 28 of the second cylinder. The breaker l8 closes at r,', i.e., about a 30 crank angle of the second cylinder.

Then as the time comes for ignition of the third cylinder and the breaker 19 for the ignition circuit 32 of the third cylinder opens at i (FIG. 4 (c)), i.e., about 30 ahead of the crank angle 0 of the third cylinder, a current a;,' having a wave form as illustrated in FIG. 4 (h) suddenly flows in the primary coil 25a of the ignition coil 25. As a result, a high voltage occurs in the secondary coil 25b whereby ignition is effected by a high voltage spark generated in the spark plug 29 of the third cylinder. The breaker l9 closes at t;,, i.e., about a 30 crank angle of the third cylinder. Through repetition of the above process, the first, second and third cylinders of the engine are successively ignited to rotate the engine in the right direction for continuous operation.

If by mistake the engine is rotated by hand or other means in a wrong direction as indicated by the broken arrow of FIG. 4, the six magnets 3 of the flywheel 22 cause the positive voltages V V V and negative voltages V,,', V,,', V each having a wave form as illustrated in FIG. 4 (i) to be generated in the ignition generator coil H3 in the order of V V V V V V,, from right to left in the drawing. Then, in the circuit comprising the ignition generator coil 13

ignition circuits

30, 31, 32 of the first, second and third cylinders, and diode 21, currents flow having wave forms a a a as illustrated in FIG. 4 (j), with the negative voltages V,,', V,,, V,,' suppressed by the diode 2i and the generating positions of the currents lagging about 30 behind the positive voltages V V V Therefore, even if the breaker 19 for the ignition circuit 32 of the third cylinder opens at i as indicated in FIG. 4 (o), no current flows in the breaker 19 as seen from FIG. 4 (j), and accordingly no current flows in the primary coil 25a of the ignition coil 25. Thus, no voltage occurs in the secondary coil 25!), and accordingly, with no spark flying in the spark plug 23 of the third cylinder, the third cylinder is not ignited. The breakers l3, I? for the

ignition circuits

31, 30 of the second and first cylinders, even if opened at r,', t, as indicated in FIG. 4 (b) (a), do not cause ignition in the same manner as with the ignition circuit 32 of the third cylinder. Thus there is no possibility of the engine being rotated in the wrong direction.

Next, another embodiment of the present invention as illustrated in FllG. 3 is described below.

Whereas in the embodiment illustrated in FIG. 2 a diode 21 is connected in series with the ignition generator coil R3 to prevent the negative voltage from being impressed on the

ignition circuits

30, 31, 32 of the first, second and third cylinders, in the embodiment illus trated in FIG. 3 a diode 21' is connected in parallel with the ignition generator coil 13 to short circuit the negative voltage generated in the coil 113 to the diode 2i This prevents the negative voltage from being impressed on the

ignition circuits

30, 31, 32 of the first, second and third cylinders. Otherwise, the construction and performance are the same as in the embodiment in FIG. 2.

In the event the diode 21 of FIG. 2 is deleted from the circuit and short circuited, with this further embodiment of the invention, just as in the embodiment using the diode, there is no relation between the number of ignition generator coils in the flywheel magneto and the number of spark plugs, and no trouble arises when the engine is rotated in the right direction. However, when the engine is mistakenly rotated in a wrong direction the positive voltages V V V and the negative volt ages V V V of the same wave form as occur in the diode igniter embodiment of the present invention are generated in the order of V V V V,,', V V from right to left in the drawing. Then the above mentioned positive and negative voltages are impressed on the

ignition circuits

30, 31, 32 of the first, second and third cylinders which have no diode connected in series or in parallel with i the ignition genei ator 53ers in the above mentioned case. Due to the impedance of the ignition generator coil 13, with the generating position lagging about 30 behind the positive and negative voltages, positive currents a a a and negative currents a a ai having a wave form as illustrated in FIG;

4 (k) flow from right to left in the drawing in the order of a a a a a a As a result, the opening po-- sitions t t 1 of the breakers l7, l8, 19 for the

igni tion circuits

30, 3t, 32 of the first, second and third cylinders as shown in FIG. 4 (a) (b) (0) agree with the generating positions of the negative currents o a a Thus, when the

breakers

17, 18, 19 open, the cur-- rents a a a having wave forms as illustrated respectively in FIG. 4 (l) (m) (n) flow in the primary coils 23a, 2%, 25a of the ignition coils 23, 2d, 25. Thereupon a high voltage occurs in the

secondary coils

23b, 25b, 25b, and as a result a high voltage spark in the spark plugs 27, 28, 29 ignites the first, second and third cylinders. Thus, there is a possibility of the engine being rotated in a wrong direction, and this is the same as in conventional devices. The possibility of the engine running in a wrong direction may be eliminated if the breaker opening position in wrong running or the breaker closing position in right running is shifted closer to the position where a spark cannot ignite any cylinder, for example, to an engine crank angle of (with piston at bottom dead center). In other words, the opening angles a,a,a, of the breakers l7, l8, 19 shown in FIG. 4 (a) (b) (c) are widely enlarged. But in that case the currents a,, 1,, a flowing in the ignition generator coil 13 shown in FIG. 4 (e) (same as the currents flowing in the

ignition circuits

30, 31, 32) will drop and the ignition efficiency will somewhat deteriorate as compared to the case of using a diode as in one embodiment of the invention.

According to one embodiment of the present invention, the igniter has a diode connected in series or in parallel with the ignition generator coil to impress an AC half wave voltage on the ignition circuit of each cylinder. The ignition efficiency of each cylinder does not deteriorate nor is there any possibility of any cylinder of the engine being ignited through a mistake in manually or otherwise turning the engine. Thus, running of the engine in the wrong direction is prevented.

The above explanation of the invention applied to a three-cylinder, two-cycle engine, but it goes without saying that the present invention is applicable to any multi-cylinder two-cycle engine.

What is claimed is:

1. An igniter for a multi-cylinder engine comprising a flywheel assembly secured to an engine crankshaft, a plurality of equally spaced apart magnets arranged in circular fashion on the inside cylindrical surface of the flywheel assembly with each magnet magnetized in a radial direction relative to the engine crankshaft, a stator plate and an ignition generator coil positioned inside the flywheel assembly on the stator plate, a cam fixed to the engine crankshaft, a plurality of breakers fitted on the stator plate constructed and arranged for opening and closing by the cam, a plurality of ignition circuits each having a pair of primary and secondary coils constructed and arranged to generate a high tension voltage through the intermittent opening and closing of the breakers, the primary coils in the ignition circuits being connected to the breakers and the secondary coils being connected to spark plugs, and the breakers of the ignition circuits being connected in series with one end grounded and the other end connected to the ignition generator coil.

2. An igniter for a multi-cylinder engine as in claim 1 wherein the other end of the ignition generator coil is connected to the plus side of a diode, the minus side of which is grounded.

3. An igniter for a multi-cylinder engine as in claim 1 wherein the junction between the ignition generator coil and the plurality of ignition circuits is connected to one end of a capacitor, the other end of which is grounded.

4. An igniter for a multi-cylinder engine as in claim 1 wherein the junction between the ignition generator coil and the plurality of ignition circuits is connected to the plus side of a diode, the minus side of which is grounded.

5. An igniter for a multi-cylinder engine as in claim 2 wherein the junction between the ignition generator coil and the plurality of ignition circuits is connected to the plus side of a diode, the minus side of which is grounded.

i i I! i UNITED STATES PATENT @FFICE CERTIFICATE OF CGREECTION Patent N :33759,237 Dated September 18, 1973 Inventor) Goro Shino et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Front Page, insert Assignee: Sawafuji Denki Kabushiki Kaisha,

Tokyo, Japan Foreign Application Priority Data December 2 1970 Japan 5-118mm Signed and sealed this 26th day of March 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents