US3715528A - Centrifugal advance device for an ignition distributor - Google Patents

Abstract

A centrifugal advance device for an ignition distributor for an internal combustion engine wherein there are provided two main flywheel masses and two auxiliary flywheel masses. The main masses are each pivotable on a pin mounted on a plate which is connected to a drivable shaft and the auxiliary masses are coupled to the main masses. These masses are adapted on rotation of said shaft to displace a plate connected to a cam which is adapted to actuate a contact-breaker arm for obtaining a variation in the timing of the spark. The auxiliary masses are arranged to move the main masses in their angular displacement during a first stage of variation corresponding to a lower region of engine speed. After the engine speed has passed through this lower region, two abutments fixed to the plate connected to the control shaft prevent further angular movement of the auxiliary masses and main masses, thus providing an intermediate region of engine speed during which the timing of the spark does not vary. As the engine speed increases still further into an upper region spring means acting on said masses are overcome to permit further angular movement of the main masses and thus further angular movement of the plate connected to said cam.

Description

Unite States Habert Feb. 6, I973 [75] Inventor: Roger I-Iabert, Epinay/Seine, France [73] Assignee: Ducellier & Cie, Paris, France [22] Filedz June 24, 1971 [21] Appl. No.: 156,207

[30] Foreign Application Priority Data July 10, 1970 France ..7025775 [52] US. Cl. ..200/19 R, 200/31 CA, 64/25 [51] Int. Cl. ..II011h [58] Field of Search ..200/19 R, 30, 31, 80 R, 31 LA;

[56] References Cited UNITED STATES PATENTS 2,008,647 7/1935 Schneider ..200/3l 3,202,777 8/1965 Scott ..200/3l 3,062,929 11/1962 Larges et a1. ..200/31 2,238,649 4/1941 Kishline ..64/24 2,219,480 10/1940 Hartzell et a1. .....64/25 2,533,755 12/1950 Bange ..64/25 3,139,081 6/1964 Tyzack ..123/l48 R 3,430,459 3/1969 Hill ..64/25 3,482,559 12/1969 Salomon ..l23/146.5 3,371,169 2/1968 Shiga et a1. ..200/19 R Primary Examiner-J. R. Scott Att0rneySughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A centrifugal advance device for an ignition distributor for an internal combustion engine wherein there are provided two main flywheel masses and two auxiliary flywheel masses. The main masses are each pivotable on a pin mounted on a plate which is connected to a drivable shaft and the auxiliary masses are coupled to the main masses. These masses are adapted on rotation of said shaft to displace a plate connected to a cam which is adapted to actuate a contactbreaker arm for obtaining a variation in the timing of the spark. The auxiliary masses are arranged to move the main masses in their angular displacement during a first stage of variation corresponding to a lower region of engine speed. After the engine speed has passed through this lower region, two abutments fixed to the plate connected to the control shaft prevent further angular movement of the auxiliary masses and main masses, thus providing an intermediate region of engine speed during which the timing of the spark does not vary. As the engine speed increases still further into an upper region spring means acting on said masses are overcome to permit further angular movement of the main masses and thus further angular movement of the plate connected to said cam.

3 Claims, 6 Drawing Figures Tr /mn PATENTEDFEB 6 I973 3,715,528

I SHEET 1 OF 2 INVENTOR PATENTED FEB. 6 I975 SHEET 2 OF 2 CENTRIFUGAL ADVANCE DEVICE FOR AN IGNITION DISTRIBUTOR The invention relates to a centrifugal advance device for an ignition distributor of an internal combustion engine, the device being of the kind which comprises a centrifugal governor with weights which, when rotated by the control shaft of the distributor, angularly moves a plate rigidly connected with a cam for actuating the contact-breaker arm in order to obtain variations in the timing of ignition.

In certain internal combustion engines, the most favorable operating conditions are only obtained if the variation of the timing of ignition (such variation depending on the number of'revolutions) does not take place in a linear manner, but is effected according to a stepped curve, i.e. in such a manner that there is, both in the lower region of the speed range as well as in the upper region, a variation which does depend on the engine speed, but that there is not, any such variation in the middle region of the speed range.

Variations of this type may be obtained, for example, by mechanisms which cause the variation in the lower region of the speed range to be initiated by one flywheel mass, namely a flywheel mass whose displace-- ment is opposed by only a weak spring, and the variation in the upper region of the speed range to be initiated by a second flywheel mass whose displacement is opposed by a more powerful spring, wherein in the central region of the speed range no variation can be produced because the centrifugal forces originating in this region are not capable of moving the second flywheel mass from its rest position.

Such an arrangement of this type causes an inbalance in the control of the distributor, an imbalance which acts in an unfavorable manner on the stability of the variation of the ignition when the engine is running.

Further, devices are also known for producing variations in the form of a stepped curve with three stages of variation. It is also known, for example, as described in French Pat. application No. 7,018,758, filed May 22nd 1970, to add to the centrifugal governor, an intermediate platewhich is pivotally mounted on the control shaft and accompanies the plate connected integral with the cam in its angular displacement during the first stage of variation under the joint action of a support member and a spring subject to a certain initial tension. The intermediate plate presses against a fixed abutment on the plate connected integral with the control shaft at a timing corresponding to the end of the first stage of variation, after which the tension of said spring and of a spring opposing the flywheel masses combine and oppose the centrifugal forces in order to obtain the second stage of variation until the centrifugal forces,

increasing due to the increase in the number of revolutions, overcome the tensions of said springs and determine the thirdstage of variation.

Although this makes it possible to solve the problem of inbalance of the device, the solution is not entirely satisfactory due'to the fact that the middle region of the speed range in which the moment of sparking does not vary, is relatively limited.

The object of the present invention is to provide an improved form of centrifugal advance device which overcomes these problems.

According to the present invention, there is provided a centrifugal advance device for an ignition distributor of an internal combustion engine of the kind comprising a centrifugal governor having rotatable masses which are adapted to angularly displace a plate connected to a cam which is adapted to actuate a contactbreaker arm for obtaining a variation in the moment of sparking dependent upon engine speed, such variation taking the form of a curve having three stages, namely a first and 3* third stage, associated respectively with the lower and upper regions of the engine speed, during which the moment of sparking varies in dependence upon the number of revolutions, and a second stage, associated with an intermediate region of the engine speed and during which the moment of sparking does not vary. The device comprises a shaft, a plate connected to said shaft, two main flywheel masses, each pivotable on a pin mounted on said plate connected to said shaft, and each arranged to act on the plate connected to the cam so as to to angularly to displace it, two auxiliary flywheel masses, coupled to the main flywheel masses, and spring means acting on said masses. The auxiliary masses are arranged to drive said main masses in their angular displacement during the first stage of variation by exerting on them additional centrifugal forces, there. Two abutments fixed to the plate connected to the control shaft. are provided and against which the auxiliary flywheel masses bear respectively at a moment corresponding to the end of said first stage of variation to prevent further. angular movement of said auxiliary masses and further angular movement of said main masses until increasing centrifugal forces acting on the main masses due to an increase in the engine speed are sufficient to overcome tension exerted by the spring means to permit further angular movement of said main masses and accordingly further angular movement of said plate connected to said cam, corresponding to said third stage.

The invention will now be more particularly described with reference to the accompanying drawings in which:

FIG. 1 is a view in longitudinal section of one example of a centrifugal advance device in accordance with the invention,

FIG. 2 is a plan view of the present invention in th stationaryposition,

FIGS. 3, 4 and 5 are plan views of the device of FIG. 1 in three different positions of the cam plate corresponding respectively to the three stages of variation of the moment of sparking, and

FIG. 6 shows a curve of variation of the the timing of sparking in the form of a stepped curve which may be obtained by a device according to the present invention.

The centrifugal advance device shown in the drawings has a shaft 1 which is connected to a plate 2 supporting two pins 3 and 4 about which pivot two main flywheel masses 5 and 6. A plate 7 connected to the cam 8, has two pins 9 and 10 which engage cam surfaces 1 l and 12 provided in the masses 5 and 6.

Two further or auxiliary flywheel masses 13 and 14 are coupled to the main flywheel masses 5 and 6 pivoting on the shafts 3 and 4. The further masses l3 and 14 are formed with apertures 15 and 16 through which pass pins 17 and 18 connected to the masses Sand 6,

the ends of said apertures 15 and 16 limiting the amplitude of the angular displacement of the masses and 6 relative to the masses 13 and 14. The amplitude of movement of said further masses l3 and 14 is limited by two abutments constituted by two brackets 23 and 24 produced by bending said plate 2. Two springs 19 and 20 have their ends respectively hooked to the pins 17 and 18 connected to the masses 5 and 6 and to brackets 21 and 22 formed by cutting and bending said plate 7 connected integral with the cam 8.

If it is assumed that the shaft 1 of the distributor rotates in a clockwise direction, said further flywheel masses 1'3 and'14 are thus the seat of centrifugal forces which tend to make them rotate about pins 3 and 4 in the direction of the arrows f. However, the spring 20 acting on the pin 18 connected to the main flywheel mass 6, keeps the device in its initial position relative to the plate 2 so long as the speed of rotation of the said shaft 1 does not reach a pre-determined value. When the speed of rotation becomes greater than that chosen, said further flywheel masses 13 and 14 turn in the direction of the arrows f and during this angular displacement drive the main flywheel masses 5 and 6 through the intermediary of the pins 17 and 18 which engage the ends 15a and 16a of the apertures 15 and 16 (FIG. 2).

The main flywheel masses 5 and 6 are then driven by the further flywheel masses 13 and 14 until said masses l3 and 14 contact the abutments 23 and 24 integral with the plate 2 and, by means of the cam surfaces 11 and 12 on which the pins 9 and 10 slide, force said cam plate 7 to rotate about the control shaft 1 by a certain angle proportional to the speed of rotation of the shaft, as determined by the profile of the cams ll, 12 and the tension of the springs 19 and 20, thus modifying the angle of advance of the spark in proportion to the speed of the engine.

The amplitude of movement of the plate 7 connected to the cam 8, relative to the plate 2, corresponds to the first stage of variation of the moment of sparking as il- I lustrated by the curve A in FIG. 6.

As soon as the further flywheel masses 13 and 14 'come into contact with the abutments 23 and 24 (FIG.

4), no further rotation of the plate 7 and cam 8 is produced for the time between speeds N and N as shown in FIG. 6, even when the number of revolutions increases, since the centrifugal force developed by the main flywheel masses 5 and 6 is insufficient to overcome the force exerted by the springs 19 and 20. This will thus provide a second stage during which the moment ofsparking does not vary as shown by line B of the curve in FIG. 6.

It is only after a further considerable increase in the number of revolutions of the associated internal combustion engine (i.e. on increase in speed of shaft 1) that masses 5 and 6 is limited by the ends 15b and 16b of the apertures 15 and 16.

With a centrifugal advance device as abovedescribed, it is possible to obtain curves of variation of the timing of ignition in the form of steps without any inbalance in the control affecting the regulation of the timing of sparking and without any limitation of the amplitude of the stages of variations.

It is to be understood that the embodiment which has been described above referring to the accompanying drawings has been given only as an example and is in no way limiting and that numerous modifications may be applied without diverging from the scope of the present invention. Thus, in contrast to the embodiment described, the pins 17 and 18 connected to the main flywheel masses and to which the springs 19 and 20 are hooked, may be connected to the further or auxiliary flywheel masses, with pins extending through apertures provided in the main flywheel masses.

I claim:

1. A centrifugal advance device for an ignition distributor of an internal combustion engine of the type including a centrifugal governor having rotatable masses which are adapted to angularly displace a plate connected to a cam, said cam being adapted to actuate a contact-breaker arm for obtaining a variation in the timing of the moment of sparking dependent upon engine speed, comprising a rotatable shaft, a plate connected to said shaft, two main flywheel masses, each main mass being pivotable on a pin mounted on said plate connected to said shaft and being operatively connected to said plate so as to angularly displace said plate when said main masses are pivoted on said pins, two auxiliary flywheel masses operatively coupled to said two main flywheel masses, spring means operatively connected between said masses and said plate, and further including two abutments fixed to said plate adjacent the paths of movement of said auxiliary masses, said auxiliary masses abutting said abutments upon moving a first predetermined angular distance jointly with said main masses, said abutments preventing further angular movement of said auxiliary masses, further angular movement of said main masses being prevented by the force of said spring means for a predetermined period of engine speed increase until increasing centrifugal forces acting on said main masses due to increases in the engine speed are sufficient to overcome tension exerted by said spring means to permit further angular movement of said main masses and thus further angular movement of said plate connected to said cam.

2. A centrifugal advance device according to claim 1, wherein each auxiliary mass is pivoted on the same pin as a main mass to which it is coupled, each auxiliary mass and the associated main mass being coupled together by a further pin which connected to one of said masses and extending through an aperture formed in the other mass coupled therewith, one end of a spring forming part of said spring means being hooked to one end of said further pin.

3. A centrifugal advance device according to claim 1 wherein said main and auxiliary masses in conjunction with said spring means and said abutments act to vary the timing of the moment of sparking in three stages, the first and third stages being associated respectively with the lower and upper regions of the engine speed, the moment of sparking in said first and third stages being dependent upon the number of revolutions of said engine, the second stage of said curve being associated with an intermediate region of the engine speed, the timing of the moment of sparking remaining constant in the intermediate region of said curve.

Claims (3)

1. A centrifugal advance device for an ignition distributor of an internal combustion engine of the type including a centrifugal governor having rotatable masses which are adapted to angularly displace a plate connected to a cam, said cam being adapted to actuate a contact-breaker arm for obtaining a variation in the timing of the moment of sparking dependent upon engine speed, comprising a rotatable shaft, a plate connected to said shaft, two main flywheel masses, each main mass being pivotable on a pin mounted on said plate connected to said shaft and being operatively connected to said plate so as to angularly displace said plate when said main masses are pivoted on said pins, two auxiliary flywheel masses operatively coupled to said two main flywheel masses, spring means operatively connected between said masses and said plate, and further including two abutments fixed to said plate adjacent the paths of movement of said auxiliary masses, said auxiliary masses abutting said abutments upon moving a first predetermined angular distance jointly with said main masses, said abutments preventing further angular movement of said auxiliary masses, further angular movement of said main masses being prevented by the force of said spring means for a predetermined period of engine speed increase until increasing centrifugal forces acting on said main masses due to increases in the engine speed are sufficient to overcome tension exerted by said spring means to permit further angular movement of said main masses and thus further angular movement of said plate connected to said cam.

1. A centrifugal advance device for an ignition distributor of an internal combustion engine of the type including a centrifugal governor having rotatable masses which are adapted to angularly displace a plate connected to a cam, said cam being adapted to actuate a contact-breaker arm for obtaining a variation in the timing of the moment of sparking dependent upon engine speed, comprising a rotatable shaft, a plate connected to said shaft, two main flywheel masses, each main mass being pivotable on a pin mounted on said plate connected to said shaft and being operatively connected to said plate so as to angularly displace said plate when said main masses are pivoted on said pins, two auxiliary flywheel masses operatively coupled to said two main flywheel masses, spring means operatively connected between said masses and said plate, and further including two abutments fixed to said plate adjacent the paths of movement of said auxiliary masses, said auxiliary masses abutting said abutments upon moving a first predetermined angular distance jointly with said main masses, said abutments preventing further angular movement of said auxiliary masses, further angular movement of said main masses being prevented by the force of said spring means for a predetermined period of engine speed increase until increasing centrifugal forces acting on said main masses due to increases in the engine speed are sufficient to overcome tension exerted by said spring means to permit further angular movement of said main masses and thus further angular movement of said plate connected to said cam.

2. A centrifugal advance device according to claim 1, wherein each auxiliary mass is pivoted on the same pin as a main mass to which it is coupled, each auxiliary mass and the associated main mass being coupled together by a further pin which connected to one of said masses and extending through an aperture formed in the other mass coupled therewith, one end of a spring forming part of said spring means being hooked to one end of said further pin.

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