EP0974991A1 - Procédé de production de contacts bimétalliques pour unités électromagnétiques de moteurs de démarrage - Google Patents

Procédé de production de contacts bimétalliques pour unités électromagnétiques de moteurs de démarrage Download PDF

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Publication number
EP0974991A1
EP0974991A1 EP99113121A EP99113121A EP0974991A1 EP 0974991 A1 EP0974991 A1 EP 0974991A1 EP 99113121 A EP99113121 A EP 99113121A EP 99113121 A EP99113121 A EP 99113121A EP 0974991 A1 EP0974991 A1 EP 0974991A1
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EP
European Patent Office
Prior art keywords
bimetallic
contact
bar
contacts
electric conductivity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP99113121A
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German (de)
English (en)
Inventor
Mario Tomietto
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STA FIL SpA
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STA FIL SpA
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Publication date
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Publication of EP0974991A1 publication Critical patent/EP0974991A1/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
    • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
    • H01H11/041—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by bonding of a contact marking face to a contact body portion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H51/00—Electromagnetic relays
    • H01H51/02—Non-polarised relays
    • H01H51/04—Non-polarised relays with single armature; with single set of ganged armatures
    • H01H51/06—Armature is movable between two limit positions of rest and is moved in one direction due to energisation of an electromagnet and after the electromagnet is de-energised is returned by energy stored during the movement in the first direction, e.g. by using a spring, by using a permanent magnet, by gravity
    • H01H51/065—Relays having a pair of normally open contacts rigidly fixed to a magnetic core movable along the axis of a solenoid, e.g. relays for starting automobiles

Definitions

  • This invention concerns a method to produce "bimetallic contacts" for electromagnet blocks for starter motors and the “bimetallic contacts" produced with this method, as set forth in the respective main claims.
  • the invention is applied in the field of production of components for motor vehicles, boats, motor-bikes and similar, or more generally in any application where there is a starter motor which activates the ignition of an engine, particularly an internal combustion engine.
  • the invention is applied to the electromagnet units which, by means of an activation command, engage and establish the necessary electric connection to the starter motor in order to start the engine.
  • the state of the art includes the standard configuration of electromagnet units, commonly known more simply as starter electromagnets or starters.
  • Electrodes substantially consist of a metal container inside which there is a coil which surrounds a movable core, which has one end protruding from the container.
  • a conductor disk On the other end of the movable core, inside the coil, there is a conductor disk, usually made of copper.
  • two fixed contacts In the container of the electromagnet there are also two fixed contacts, usually consisting of two metal bolts separated from each other, with the shank protruding from one side of the container and the head inside the container and facing the conductor disk.
  • One of the two metal bolts is electrically connected to the starter motor and the other to the feed battery.
  • the coil When the ignition mechanism is activated, normally with a key, the coil is energised and causes an axial return movement of the movable core inside the container.
  • the first effect of this axial movement by means of lever systems associated with the outer end of the movable core, is to engage a pinion on the crown of the engine.
  • a second effect is to take the conductor disk to a position of proximity with the heads of the "fixed bolts" which protrude from the container of the electromagnet.
  • the high resistance ensures that, during the installation step, no damage is caused to the structure of the fixed contacts due to torsional stresses caused by the clamping tools being used too energetically.
  • the state of the art includes "bimetallic contacts" wherein a little seating is made on the front part of a steel body wherein a head or disk made of copper is inserted and mechanically coupled, to serve as a conductor element.
  • the copper head is installed in the relative seating by means of lateral and frontal percussion so as to give the copper a rounded shape which protrudes from the seating, thus improving the conduction contact with the disk on the movable core.
  • This document teaches to achieve bimetallic contacts consisting of a first body, made of iron and shaped like a bar, including a pre-shaped, cylindrical blind seating in correspondence with its head, and a second body made of copper and suitable to be inserted into the said pre-shaped seating by means of plastic deformation created by closing an element of a mold.
  • the initial shape of the second, copper body is higher and narrower than that of the seating into which it is inserted, so that, when the mold is closed, the second body is plastically deformed and crushed, and fills the seating in the head of the first body.
  • this embodiment guarantees a certain level of certainty that the second body will not become detached from the first, on the other hand it does not guarantee an optimum capacity of electric conduction, since it is impossible to ensure, with this method, that all the interstices between the first and second body are completely filled.
  • This method has the disadvantage that it causes an extremely high increase in temperature, with the production of an intermetallic component with a high carbon content in the zone of transition between the two metals which causes a limitation to the electric conduction of the contact.
  • the purpose of the invention is to obtain bimetallic contacts for electromagnet units in starter motors for internal combustion engines which will guarantee on the one hand high characteristics of electric conductivity and mechanical resistance, particularly to torsion, and on the other hand will guarantee that these characteristics will remain substantially unchanged in time, even after an extremely high number of ignition cycles.
  • the bimetallic contact is made starting from a steel bar, of a desired shape which may even be standardised, on the top of which a cavity is made of a desired depth and with a flared top.
  • steel we also mean materials other than steel but with the same or similar mechanical characteristics.
  • the steel bar may substantially be of any shape whatsoever, and may not even have a direct resemblance to the shape of the bimetallic contact in its definitive configuration.
  • a small copper cylinder is inserted, in a substantially free manner, of a shape mating with that of the cavity.
  • copper we mean other materials too, which have similar characteristics of electric conductivity.
  • the third step is to subject the steel bar and the copper cylinder to a heat treatment, for example thermo-welding, whereby the two materials are made solid with each other in a single piece.
  • a heat treatment for example thermo-welding
  • the heat treatment provides a treatment of thermal diffusion with at least partial molecular exchange between the two metals, or a similar treatment, whereby the two materials are partly melted and penetrate each other in the areas of reciprocal contact.
  • the said heat treatment guarantees absolute adherence over the whole contact area, which can also be prolonged for a long segment of the bar and therefore can be not limited to the area of the head alone.
  • the mutual penetration of the two metals with at least a partial molecular exchange guarantees that there are no interstices or zones of non-adherence between the two bodies, thus optimising the characteristics of electric conduction of the contact even after a large number of cycles and even when there are environmental conditions of wear.
  • the bimetallic half-finished product is sent to molding and rolling to obtain the definitive form with the copper part acting as the head and penetrating to a desired depth into the steel body, ensuring a sufficient area of contact for the due transmission of electric current.
  • the molding and rolling step is carried out with the two materials already substantially solid, it is possible to correct any possible flashes and deformations caused during the coupling step, thus obtaining a final product which has no surface defects and which therefore guarantees optimum functioning in every application.
  • the molding and rolling step finishes off the coupling between the two materials, particularly in the parts of the copper head which protrude from the cavity made in the steel bar.
  • the surface configuration of the copper head may have various patterns and or knurling, according to the specifications of the purchaser; the shape and section of the copper part may also vary according to the technological and operational requirements.
  • the electromagnet unit, or simply electromagnet, 20 shown in Fig. 5 has a container 19 which houses a movable core 18, one end 18a of which protrudes from the side of the container 19.
  • a movable core 18 Around the movable core 18 there is a coil 17, the ends 17a of which are associated with electric feed means connected to the ignition key.
  • a cup-shaped support 16 Inside the container 19 there is also a cup-shaped support 16, axially hollow, inside which there is a rod 15, axially movable and protruding from the cup-shaped support 16 towards the movable core 18.
  • a conductor disk 14 On the face of the cup-shaped support 16 which is opposite the movable core 18 there is mounted a conductor disk 14, normally made of copper.
  • the shank 11 of two metallic contacts 10 emerges; the head 12 is located inside the container 19 in a position adjacent to the conductor disk 14.
  • a first metallic contact 10 is electrically connected to the engine of the automobile, while a second metallic contact 10 is electrically connected to the battery.
  • the coil 17 is energised, and this generates a return movement of the movable core 18 inside the container 19.
  • the movable core 18 is connected on the outside to a system of levers, which is not shown here as it has no effect as far as the invention is concerned, by means of which the return movement causes a pinion to engage on the crown of the engine.
  • a further return movement of the movable core 18 inside the container 19 causes the rod 15 to thrust and displace the conductor disk 14 in the direction of the heads 12 of the metallic contacts 10.
  • the electric circuit between the engine and the battery is completed through the contacts 10 and the conductor disk 14, thus giving power to the engine which starts, and makes the pinion rotate.
  • a bimetallic contact 10 according to the invention, shown in part section in Fig. 2, comprises a shank 11 made of steel or similar material and a head 12 made of copper or similar material.
  • the copper head 12 extends inside the steel shank 11 for a desired depth, which may even be considerable with respect to the overall length of the shank 11 itself, in such a manner as to ensure the necessary contact area for the current to be transmitted, and may be of any shape whatsoever, for example square (Fig. 3), circular or otherwise.
  • the surface of the head 12 has knurls 13 which reduce over-heating as the current passes through.
  • the shape of the head 12, the inclusion and pattern of the knurls 13, the depth of the head 12 inside the shank 11 are part of the design specifications of the contact 10 and may vary from case to case according to the requirements of the specific user.
  • the method to achieve the bimetallic contact 10 is articulated in four essential steps and is shown in diagram form in Fig. 1.
  • the step shown in Fig. 1a is the shearing to size of a steel bar 22 from a bar 122; the bar 22 is then subjected to a molding operation which tapers the lower end and makes a cavity 24 flared at the top on a segment of the upper part, so as to obtain a half-worked piece 22a.
  • the bar 22, as the starting body, may be substantially of any shape, even very different from the final configuration of the bimetallic contact; to be more exact, the bar 22 may be of a standardised shape from which various distinct shapes of the bimetallic contact as the final product may then be derived.
  • a cylinder 23 is sheared, with a shape mating with that of the cavity 24; the cylinder 23 is assembled mechanically with the steel bar 22, possibly by means of a slight compression which can even be performed manually, so as to achieve a pre-coupling with the flared shape of the cavity 24.
  • the said heat treatment achieving an at least partial molecular exchange over the whole area of contact between the two materials, guarantees an optimum, indissoluble coupling, with no possibility of cracks or interstices forming, with the possible infiltration of humidity.
  • the half-worked piece 26 is subjected to a molding and rolling operation so as to obtain the final form of the contact 10, with the copper head 12 protruding so as to cover the top part of the shank 11 and which extends inside the shank 11 for a desired length "1" such as to ensure the necessary contact surface between the steel and copper for an efficient transmission of the electric current.
  • any knurls 13 are made on the piece, and/or any other profiles or patterns possibly requested by the users.
  • This step is also used to remove any possible flashes or slight deformations which have been generated during the coupling step of the two elements 22 and 23.
  • the final result obtained is a contact 10 with a coupling surface for the conductor disk 14 made entirely of copper and with an outer body made entirely of steel, thus ensuring the optimum combination of high conductivity and high mechanical resistance, particularly to torsion.
  • the indissoluble coupling achieved by heat treatment guarantees that the mechanical stability of the contact 10 is maintained even when there are strong heat stresses and even after an extremely high number of repeated ignition cycles, which ensures an optimum and long-lasting productivity of the electromagnet 20.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Lubrication Of Internal Combustion Engines (AREA)
  • Contacts (AREA)
EP99113121A 1998-07-21 1999-07-07 Procédé de production de contacts bimétalliques pour unités électromagnétiques de moteurs de démarrage Withdrawn EP0974991A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITUD980131 ITUD980131A1 (it) 1998-07-21 1998-07-21 Procedimento di produzione di contatti bimetallici per blocchi ad elettromagnete dei motori di avviamento e relativi
ITUD980131 1998-07-21

Publications (1)

Publication Number Publication Date
EP0974991A1 true EP0974991A1 (fr) 2000-01-26

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Application Number Title Priority Date Filing Date
EP99113121A Withdrawn EP0974991A1 (fr) 1998-07-21 1999-07-07 Procédé de production de contacts bimétalliques pour unités électromagnétiques de moteurs de démarrage

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EP (1) EP0974991A1 (fr)
IT (1) ITUD980131A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022018029A1 (fr) * 2020-07-21 2022-01-27 Vitesco Technologies Germany Gmbh Disjoncteur à mettre en place dans un coffret disjoncteur et coffret disjoncteur pour véhicule à moteur

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2086221A (en) * 1934-12-10 1937-07-06 Mallory & Co Inc P R Contact assembly
CH289818A (de) * 1950-06-22 1953-03-31 Fr Ghielmetti & Cie Ag Schalterkontakt mit Kontakthalter für elektrische Apparate.
US2755368A (en) * 1953-11-27 1956-07-17 Gen Motors Corp Welding method
FR2030944A5 (fr) * 1969-06-07 1970-11-13 Bosch
EP0059341A1 (fr) * 1981-03-04 1982-09-08 Hitachi, Ltd. Méthode de production de contacts électriques
DE4119298A1 (de) * 1991-06-12 1992-12-17 Bosch Gmbh Robert Kontaktbolzen mit kontaktplatte aus edlerem metall

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2086221A (en) * 1934-12-10 1937-07-06 Mallory & Co Inc P R Contact assembly
CH289818A (de) * 1950-06-22 1953-03-31 Fr Ghielmetti & Cie Ag Schalterkontakt mit Kontakthalter für elektrische Apparate.
US2755368A (en) * 1953-11-27 1956-07-17 Gen Motors Corp Welding method
FR2030944A5 (fr) * 1969-06-07 1970-11-13 Bosch
EP0059341A1 (fr) * 1981-03-04 1982-09-08 Hitachi, Ltd. Méthode de production de contacts électriques
DE4119298A1 (de) * 1991-06-12 1992-12-17 Bosch Gmbh Robert Kontaktbolzen mit kontaktplatte aus edlerem metall

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022018029A1 (fr) * 2020-07-21 2022-01-27 Vitesco Technologies Germany Gmbh Disjoncteur à mettre en place dans un coffret disjoncteur et coffret disjoncteur pour véhicule à moteur

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Publication number Publication date
ITUD980131A1 (it) 2000-01-21

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