AU490397B2 - Improvements in ignition contact breakers for internal combustion engines - Google Patents

Description

(11) 4 9 0,3 9 7

PATENT SPECIFICATION (21) 83, 42 6 M Class (52) 66.8

2 F02P 7/06 Int. CI. (51)

Application Number (21) 83426/75 Lodged (22) 28th July, 1975 Complete Specification entitled (54) "IMPROVEMENTS IN IGNITION CONTACT BREAKERS FOR INTERNAL COMBUSTION ENGINES"

28th July, 1975 Accepted (44) 1st February, 1978 Lodged (23)

Convention Priority (30) 31st October. 1974 Published (41) 3rd February, 1977 DE P 24 51 819.2

Applicant (71) ROBERT BOSCH,GmbH

Actual Inventor (72) HEINZ BERGER HAROLD KALIPPKE UWE ZROGER HERBERT MAGDE FRAU ERICH PECHATSCHEK SEPP RAMSAUER HERBERT SCHRATZ HARTMUT BRAMMER

230499 (50786/59) 66.8 Related Art (56) 443986 (14137/70) 04.22,66.8 423154 (34314/68) 66.8

the best method of performing it The following statement is a full description of this invention, including known to us

1153/76- C. J. Thompson, Government Printer, Canber,

X951-66-2D-13 P.C.

$83,426/75

The invention relates to an ignition contact breaker

for an internal combustion engine in which a contact-breaker

lever, provided with a lever contact, is pivotable against the

force of a spring and in which a support contact, which is

movable relative to the lever contact, is pivotally mounted.

Owing to the action of the contact-breaker spark,

material migration takes place at the contact surfaces of igniti

contact breakers from the generally positive lever contact to

the negative anvil contact. Moreover, an oxide layer, which is

caused by vaporisation of the metalof the contacts and which

increases the electrical resistance in the primary circuit, is

also produced on the contact surfaces. Both changes of the

contact surfaces influence indirectly the magnitude of the

contact angle and hence also the firing instant, and, in

particular, necessitate the replacement of the contact breaker

after a relatively short working life.

A method has already been proposed wherein, in order

to prevent changes in the contact between the two contact that the points, relative movement is achieved in such a manner

two contacting surfaces are rubbed against each other. In

contact breakers in wnich it is possible to adjust the firing

instaiit by means of a linkage system, it has already been

proposed to utilise the arc-like pivotal movement of the lever

order for produce the relative movement. This contact in system proposed solution consequently makes the linkage two contacts necessary, and the relative movement between the the vacuum in the inlet takes place only on a change in

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manifold of the engine. This arrangement cannot be used,

however, in contact breakers of a different construction.

A construction of an ignition contact breaker having

a support contact mounted eccentrically in an insulating

sleeve is already known. Since there is rotational movement

between a fixed base plate and a contact-breaker plate,

pivotal movement of the contact-breaker plate causes eccent-

ric movement of the support contact relative to the lever

contact; in this case also, relative movement takes place

only when the contact-breaker plate is moved. In addition

to the rotational and eccentric mechanism, various other

parts are required; in view of present-day mass-production

methods, ignition contact breakers of such complexity are

no longer in demand owing to reasons of cost.

It is a feature of the invention to improve ignition

contact breakers for internal combustion engines of the

above-described type so that, in the event of a contact-

breaker plate being provided, relative movement is achieved

by means of simple, reliable components. Furthermore,

methods are proposed whereby relative movement may be

achieved even without the contact-breaker plate.

According to the invention there is provided an

ignition contact-breaker for an internal combustion engine

comprising a stationary base plate, on which a contact-

breaker lever provided with a lever contact is arranged

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to pivot against the force of a spring, and on which a

support contact is pivotally supported by means of a

stationary pivot pin which is upstanding from the base

plate and which journals a sleeve to which said support contact is attached, whereby the support contact is

moved by engine vibrations and the contacts are movable

relative to each other.

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Thus, the invention T,=efet~a-1 utilises the vibration the or vibration acceleration produced by the engine to provide embodiments relative movement.' An advantage achieved by preferred that, throughout of the invention lies, in particular, in the fact between the the time the engine is running, variable movement without lever contact and the support contact is achieved limitation reference to engine parameters, and that different of vibration. of movement is possible at different intensities to In order to be able to connect the support contact of the the ignition co~il and utilise the sliding properties is made of plastics material for bearing purposes, the sleeve parallel-to insulating material, and has a recess, preferably is arranged the axis of the pivot pin, and the support contact of insertion on a plate inserted in the recess, its direction position, in being limitedby means of a stop in its inserted of the which it is secured by retaining meanis. This embodiment the support invention also enables the plate provided with from the sleeve, contact to be readily inserted in and removed to the upper and also the insulated lead may easily be attached face of the plate. is In order to eliminate the inevitable pl-ay, which pin and the bearing detrimental to contacting, between the pivot of the inventior bore of the sleeve, according to a further feature in. a resilient bias is applied to the sleeve so that it is the support contact. abutment with the pivot pin in the region of by means of a Advantageously, this resilient bias may be applied spring. flat spring, a hairpin spring or a helical

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In order to ensure that the pivotal or rotational

movement of the support contact about the pivot pin is naintaine(

within predetermined limits, according to a further feature of

the invention, a lever extends substantially radially from the

sleeve and pivots between two stops on the adjacent plate,

thereby limiting the pivotal movement of the support contact. a In general, ignition distributors are provided with

rotatable contact-breaker plate, since, when the engine is

load, adjustment of the firing instant is effected under partial the inlet manifold of the engine. In by means of the vacuum in proposal of such an embodiment in accordance with a further by the invention, the relative movement is achieved additionally between the the provision of a tension spring, which extends of the sleeve and a stationary member, such as the housing being hooked prefera ignition distributor, one end of the spring

to a lug on the sleeve on the opposite side to the support is contact. If the tension spring has a low spring rating and 200 grammes designed for a minimum preload of approximately adjustment is weight, the effect of the spring on the vacuum insubstantial.

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If, as in yet a further proposal of the invention, the

lever extending outwardly from the sleeve is constructed as an

inertial mass, this serves advantageously to increase the moment

of inertia. Such an increase ensures the pivotal movement of the

support contact necessary to produce a relative movement.

The invention is further described, by way of example,

with reference to the accompanying drawings, in which:-

Fig. 1 is a partially cross-sectional view, along the

line I I in Fig. 2, of a first embodiment of contact breaker

in which a contact support is provided,

Fig. 2 is a plan view of the contact support as shown

in Fig. 1,

Fig. 3 is an end elevation of a variant of the embodi-

ment shown in Figs. 1 and 2,

Fig. 4 is an end elevation of a further variant of

the embodiment of Figs. 1 and 2, ond

Fig. 5 is a plan view of a further embodiment of

contact breaker.

Figs. I and 2 show an ignition contact breaker for an

internal combustion engine. A contact support 10, which is

secured by means of a screw (not shown) through an elongated plate (not hole 11 to a fixed contact-breaker plate or base

shown in Figs. 1 and 2, but see the base plate 65 in Fig.

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A stud 12 is riveted to the contact support 10 and a contact-

breaker lever 13 is pivotally mounted in the stud 12 and is

secured axially by means of a retaining washer 14. A cam

follower 15 is fitted to the contact-breaker. lever 13 and

cooperates with a cam (not shown). One arm 17 of a U-shaped

spring 16 exerts pressure on the contact-breaker lever 13, the

other arm 18 of the spring being secured to an upstanding flange

19 by means of a screw 20. A lever contact 21 is preferably

riveted on the outer end portion of the contact-breaker lever i] A pivot pin 23 is riveted in a countersunk portion 22

of the contact support 10. A sleeve 24 (also called a supportii

member) which is manufactured from insulating material, has a

bore 25 by wnich t%e sleeve is journalled in the pivot pin 23

to form a bearing point, so that the sleeve 24 is able to

perform a pivotal movement. Parallel to the pivot axis 27, the form o. sleeve 24 has a recess 26, whose cross-section is in the a coulisse. A metallic plate 28, provided on its broad side far with a support contact 29, is inserted in the recess 26 as which is as a stop 30. A lead 32 is attached to a terminal 31, 28. permanently attached to the upper end portion of the plate A slot 33 is formed in the bore 25, serving as a bearing, on the opposite side to the recess 26 and parallel to

pivot axis 27. A wavy leaf spring 34 is inserted in the slot 33 p and has a convex central portion which acts against the pivot base of 23, and two end portions which are supported a.ainstthe

the slot A spring ring 35 on the pivot pin 25 axially reta

the sleeve 24 and the leaf spring 34. In this spring- arrangeme it is in a resilient force is applied to the sleeve 24 so that

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abutnient with the pivot pin 23 in the region of the support contact 29. A lever 36,-on which a cam 57 is formed, extends substantially radially from the sleeve 24 of plastics naterial. A further curved slot 38, which is arcuate in its longitudinal direction, is formed in the contact support 10, the centre of the are being the pivot axis 27. The described ignition contact breaker operates as follows:- In the position shown in the drawings, the U-spring 16 urges the lever contact 21, via the contact-breaker lever 13, into contact with the support contact 29, whose contact surface is convex; the primary circuit is thereby closed. Similarly, the contact-breaker cam (not shown) lifts the contact-breaker lever 13, via the cam follower 15 of-the lever, away from the support contact against the force of the spring; 16, and thereby opens the primary circuit. Dependent upon the vibration acceleration caused by the engine, the support contact 29 performs movement about the pivot axis 27 whose magnitude is dependent. upon the vibration or jolting of the enGine. The pivotal movement of the support contact 29 is limited by the length of the slot 38. Fig. 3 differs from the embodiment shown in Figs. I and. 2 in that a hairpin spring 40 is used instead of the flat spring; the first arm 41 of this hairpin spring 40 is supported on the pivot pin 23, and its second arm 42 on a lug 43 on the sleeve 44. In this case also, the force of the hairpin spring acts on the sleeve 44Lso that the latter is in abutment with

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the pivot pin 23 in the region of the support contact 29. The method of operation and other constructional detai reference to are the same as in the embodiment described with Figs. I and 2. In the embodiment shown in Fig. 4, the resilient hook of force is provided by a helical spring 50. The first outwardl1 this spring 51 is supported in a lug 43, which extends contact from the sleeve 54 on the opposite side to the support stretcl 29. The second hook 52 is supported in a yoke 53, which lies between the end. portions of two arms 55, one of which forwardly of the plane of the drawing. material, The sleeve 54, which is made of insulating underside the also has a radially-disposed lever 56, to whose the previous cam 37 is attached. As is possible also in plain steel, so' embodiments, this cam 37 is manufactured from also as an inert that, owing to its increased weight, it serves the mass. The two arms 55 extend in the form of a fork from cam 37 in the manner contact support 10 and form stops for the of the support already described so that the pivotal movement contact 29 about the pivotal axis 27 is limited. housing 60, to Fig. 5 shows an ignition distributor is transmitted to which a vacuum diaphragm, whose displacement via a connecting spring-loaded connecting rod 63, is attached is a base plate member 61. Likewise'attached to the housing 60 supported on which a contact-breaker plate 66 is rotat.hly and from which a pin 67 is upstandinG so that a .linkage is 21 formed. The contact support 10, carrying the lever contact by means of a screw 68 and the support contact 29, is secured

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to the pivotable contact-breaher plate 66 arranged therebelow, the pivotal movement produced by thne connecting rod 63 being transmitted to the contact support The sleeve 64 is supported and axially secured about the pivot pin 23, and, as compared with the embodiments herein- before described, has a lug 45 arranged on the side substantially opposite to the support contact 29. A tension spring 70 has

two spring hooks 71 and 72, the first of which is hooked onto the lug 45, and the second is hooked onto an eye 75 screwed to the housing 60.. The tension spring 70 has a low spring rating and is designed for a minimum preload of approximately 200 Pond so that the effect of tolerances on the vacuum-control characteristic is .limited. The pivotal movement about the pivot pin 23 is trans- mitted to the sleeve 64 of plastics material, and hence also to the support contact 29 -attached thereto, only when, owing to a change in the vacuum in the inlet manifold of the engine, the connecting rod 63 Pivots the vacuum plate 66 and hence also the contact support 10. This pivotal movement, and the resultant relative movement with respect to the support contact 21, produced by means of the spring 70. Since ignition contact breakers are attached almost exclusively to a pivotable contact- breaker plate 66, this present embodiment of the invention provides a simple arrangement in which, in addition to vacuum adjustment, vibration acceleration cau sed by the engine is advantageously used t6 effect the relative movement of the two contacts 21 and 29.

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Claims (4)

83,426/75 The claims defining the invention are as follows:

1. An ignition contact-breaker for an internal

combustion engine comprising a stationary base plate, on

which a contact-breaker lever provided with a lever contact is arranged to pivot against the force of a spring,

and on which a support contact is pivotally supported by

means of a stationary pivot pin which is upstanding from

the base plate and which journals a sleeve to which said

support contact is attached, whereby the support contact

is moved by engine vibrations and the contacts are movable

relative to each other.

2. An ignition contact breaker as claimed in claim

1, in which the support contact and the contact-breaker

lever together with the lever contact are arranged on a

pivotable contact-breaker plate.

3- An ignition contact breaker as claimed in claim

1 or claim 2 in which the support contact and the contact-

breaker lever together with the lever contact are arranged

on a contact support.

4. An ignition contact breaker as claimed in any

preceding claim, in which the sleeve is constructed of

insulating material and is provided with a recess and the

support contact is arranged on a plate which is inserted in

the recess, the insertion of the plate being limited by a

stop on the sleeve.

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An ignition contact breaker as claimed in claim

4 in which a stop on the sleeve limits the insulation of

plate with the contact thereon.

6. An ignition contact breaker as claimed in claim

4 or 5 in which the recess is parallel to the axis of the

pivot

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pin. 7. An ignition contact breaker as claimed in claim 41! or 6 in which the sleeve is resiliently biassed so that the sleeve is in abutment with the piv ot -pin in the region of' the

support contact. 8. An ignition contact breaker as claimed in claim 7 in which the resilient bias is provided by a f'lat spring which f itted in a slot of' the bearing bore of' the sleeve. 9. An ignition contact breaker as claimed in claim 7 in which the resilient bias is provided by a hairpin spring, a first arm of which is supported on the pivot pin and a second arm of which i~s supported on the sleeve.- An ignition contact breaker as claimed in claim7 in which the resilient bias is provided by a helical spring oni end of which is attached to a lug on the sleeve and the other

end of which is supported by the contact support. 11. An ignition contact breaker as claimed in claim in which two arms extend outwardly, the end portions of the ai

being interconnected by a yoke to which said other end of' the helical spring is attached. 12. An ignition contact breaker as claimed in claim;

7or 10 in which a tension spring extends between the sleeve and a stationary member such as the housing of an ignition distributor. An ignition contact breaker as claimed in claim 12 in which the tension spring has a low spring constant and is constructed for a minimum preload of approximately 200 Pond.

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14i. An ignition contact breaker as claimed in any preceding claim in which the possible pivotal movement of the sleeve about the pivot-pin is limited. An ignition contact breaker as claimed in claim 1'4 in which the sleeve is provided with a caia. movable in an arcuate slot to limit the pivotal movement of the sleeve. 16. An ignition contact breaker as claimed in claim 14 in which a lever extends substantially radially from the sleeve

and is pivotable between two stops on an adjacent plate. 17. An ignition contact breaker as claimed in claim in wnich the caw is constructed as an inertial mass. 18. An ignition contact breaker as claimed in claims 2 and 14Iin which a sliding can on the sleeve cooperates with an oblique slideway in the base plate whereby the support contact is movable responsively to pivoting of the contact breaker plate.

II. An ignition contact breaker constructed substantially as herein described with reference to and as illustrated in Figs. 1 and 2, or Fig. 3 or Fig. 4 or Fig. of the accompanying drawings.

D A T E D this 25th day of July, 1975.

ROBERT BOSCH, G.m.b.H

By its Patent Attorneys. CAILINAN:, ATD ASSOCIATES.

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Fig.1

k, 37

Fig.2

Kl -I

Fig.3

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Fig. 4

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