GB2277834A

GB2277834A - Electromagnetic relay for the starter of an internal combustion engine

Info

Publication number: GB2277834A
Application number: GB9400643A
Authority: GB
Inventors: Karlheinz Boegner; Ngoc-Thach Nguyen; Josef Weigt; Manfred Eyermann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-01-16
Filing date: 1994-01-14
Publication date: 1994-11-09
Anticipated expiration: 2014-01-14
Also published as: ITMI940037A1; FR2700637B1; FR2700637A1; DE4301056A1; GB9400643D0; GB2277834B; ITMI940037A0; IT1269427B

Description

2277834

-1DESCRIPTION ELECTRO-MAGNETIC SWITCH SUCH AS AN ENGAGEMENT SOLENOID SWITCH FOR THE STARTER OF AN INTERNAL COMBUSTION ENGINE

The invention relates to an electro-magnetic switch in the form of an engagement solenoid relay for a starter of an internal combustion engine, having a solenoid core with which a relay coil is associated and an armature which comprises a switching pin which extends through an opening of the solenoid core and at one of its ends carries a contact bridge protruding into a contact chamber, the contact bridge having contact surfaces disposed in an axial direction and being associated with maincurrent contacts. The main current contacts have contact surfaces.

Solenoid switches of this type serve the purpose of switching a high current using a relatively low control current. The high current (starter current), which is necessary for the starting of an internal combustion engine by means of a starter, can be, for example in a passenger motor vehicle, up to approximately 1,000 amps, and in a commercial vehicle up to approximately 2,500 amps.

A starter switch is sufficient to switch on the low control current. The high starter current is switched by means of an engagement solenoid relay.

The armature of the engagement solenoid relay comprises a contact bridge, which connects the maincurrent contacts to each other when the engagement solenoid switch is in the energised state.

Because of the high starting currentr mentioned above, great importance is attached to the form of the contact surfaces of the contact bridge as well as of the main-current contacts. It is known in engagement solenoid relays of this type to guide the bridge contact, formed as a plate, against the force of a spring towards the main-current contacts. Due to the rigidity of the contact bridge and of the main-current contacts, complete freedom from chatter of the contacts cannot be assured. However it is precisely the freedom from chatter of the contact that influences the service life of the contacts to a considerable degree. Chatter of the contacts can cause contact-welding when the high starter currents for switching are present. Every contact-weld, however small, leads to a reduction in the electrical conductivity of the contact surfaces, which is detrimental to the service life of the starter.

It is the object of the present invention to create an electromagnetic switch of the generic type which has a low-chatter contact arrangement and therefore has a long service life.

The invention resides in an electro-magnetic relay, having a solenoid core with which a relay coil is associated, and having an armature comprising a switching pin, which extends through an opening of the solenoid core and at one of its ends carries a contact bridge protruding into a contact chamber, which contact bridge contact has contact surfaces disposed in an axial direction and associated with main-current contacts, which have contact surfaces. wherein the contact bridge and the main current contacts have contact surfaces which are inclined to the axial direction and at least one of the contact surfaces is formed resiliently in a radial direction.

When the contact bridge and the main-current contacts have contact surfaces which are inclined to the an axial direction and at least one of the contact surfaces is resiliently mounted in a radial direction, secure and chatter-free contacting can be effected.

By means of this arrangement the advantage arises that, even when very high currents are switched, for example starter currents, secure contacting can be carried out without the danger arising of a contactweld.

With the contact arrangement in accordance with the invention a high contact pressure is simultaneously realised over the entire contact -4surface so that the electrical resistance value of the entire contact arrangement is influenced in a positive way. Furthermore, contact surfaces in accordance with the invention can be made larger so that the build up of heat, which is inevitable during contact operation and contact release, can be better dissipated over the area of the transitional surface.

In a particularly advantageous embodiment of the invention it is provided that the contact surface of the contact bridge as well as the contact surfaces of the main-current contacts, are resiliently mounted in a radial direction. It is thereby achieved that possible shape- or positional tolerances arising during production can be reliably balanced out by means of the simultaneous resilient arrangement, so that in each case it is possible to produce a reliable contact.

Furthermore, by means of the resilient arrangement on both sides, the danger of a chatter effect of the contact arrangement is further reduced.

Specific embodiments of the invention will now be described, by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal section through an engagement solenoid relay of a starter device of an internal combustion engine; Figure 2 is a longitudinal sectional view of the contact point of the engagement solenoid relay of Figure 1; Figure 3 is a further longitudinal sectional view of a contact point; Figure 4 is a further longitudinal sectional view of a contact point; Figure 5 illustrates in plan view an arrangement of two main-current contacts; and Figure 6 illustrates the contact elements individually, in a perspective view.

Figure 1 is a longitudinal sectional view through an engagement solenoid relay 10. The engagement solenoid relay 10 comprises a solenoid core 12, an armature 14, a relay coil 16, an armature-guiding sleeve 18 and a housing 20. The armature 14 is mounted in the armature guiding sleeve 18 in an axially displaceable manner and comprises a switching pin 26 consisting of the parts 22 and 24. The part 22 of the switching pin 26 is allocated to the armature 14 and the part 24 of the switching pin 26 to the solenoid core 12. In the non-energised position of the engagement solenoid switch 10, as Figure 1 shows the parts 22 and 24 are axially separated from each other. A helical compression spring 28 is disposed between the solenoid core 12 and the armature 14, -6which spring protrudes into and engages a recess 30 in the armature 14 and serves as a return spring for the armature 14. The part 24 of the switching pin 26 is situated in an opening 32 of the solenoid core 12. A free end of the part 24 of the switching pin 26 is directed towards a contact chamber 36. The part 24 of the switching pin 26 comprises there a stop collar 38, against which one end of a pressure spring 40 bears. The other end of the spring 40 abuts against the inner side of a housing cover 42. The contact chamber 36. referred to above is formed in the interior of the housing cover 42.

An insulating material washer 44 abuts against the other side of the stop collar 38, and the bridge contact 48 is disposed between said washer and a liner 46 which extends into the opening 32. The housing cover 42 has openings 50 in which main-current contacts 52 are disposed. The maincurrent contacts 52 each have at the contact chamber side, enlarged diameter regions 54.

The enlarged diameter regions 54 of the maincurrent contacts 52 thus simultaneously form the electrodes which work in co-operation with the bridge contact 48.

Details of the contacts are illustrated in Figures 2 to 6.

The operation of the engagement solenoid relay 10 shown in Figure 1 is briefly explained hereinunder. When a switching current is fed to the relay coil 16, this coil, draws the armature 14 towards the solenoid core 12 magnetically. The armature is thus moved against the force of the spring 28. In a first step, the part 22 of the switching pin 26 contacts the part 24 of the switching pin and moves this part against the force of the spring 40 through the liner 46, disposed in the opening 32, in an axial direction towards the housing cover 42. The axial movement of the armature 14 is restricted by abutment of the collar 15 against the base of the recess 17 of the solenoid core 12. During the axial movement of the part 24 of the switching pin 26, the contact bridge 48, situated thereon, is moved towards the maincurrent.contacts 52. By means of the foremost part 22 of the switching pin, the pinion of the starter, not illustrated, is at the same time engaged in a known manner into a toothed ring of the internal combustion engine. Prior to the final position of the armature 14 being reached, an electrically conductive connection between the main-current contacts 52 is produced by the contact bridge 48, by way of which a starter current flows.

When the engagement solenoid switch is put into a -8non-operational position by the switching off of the voltage at the relay coil 16, the armature 14 and the part 24 of the switching pin 26 are brought back to their starting position by means of the springs 28 and 40. The contact bridge 48 is thus separated from the main-current contacts 52 so that the flow of the starter current is interrupted.

The contacts according to Figure 1 are shown in more detail in Figure 2 wherein the same parts are provided with the same reference numbers.

The form of the contact bridge 48 is dealt with in more detail hereinunder. This contact bridge comprises a portion 56 which runs approximately parallel to the stop collar 38 and rests by way of the washer 44 against this collar. The contact bridge 48 extends outwards from the region 56 in a radial direction in inclined contact surfaces 58. The contact surfaces 58 are thus disposed in such a manner that the larger diam ter portion of these surfaces lies in the direction towards the solenoid core 12. The contact bridge 48, has furthermore, a portion 60F which is formed in a annular shape and is mounted on a smaller diameter step of the liner 46.

In a preferred embodiment, the entire bridge contact 48, with its regions 56 and 60 as well as the contact surfaces 58, is produced as a single part.

-9This part is, for example, a drawn or deep-drawn or pressed sheet metal piece.

Furthermore, the larger diameter region 54 forming the head 64 of the main-current contact 52 has chamfered regions 66 at its side facing the contact chamber 36, which chamfered regions simultaneously form the contact surfaces 68 of the main-current contacts 52. The chamfered regions 66 are formed in such a way that the resulting contact surfaces 68 are inclined to the axial direction and parallel to the contact surfaces 58 of the bridge contact 48. By means of this arrangement, in accordance with the invention, of the contact surfaces 58 or 68 the following function arises.

In the energised state of the engagement solenoid relay 10, the part 24 of the switching pin 26 is moved axially towards the housing cover 42. During this axial movement. the bridge contact 48 is moved towards the main-current contacts 52. At a predetermined moment, the contact surface 58 of the contact bridge 48 thus comes to abut against the contact surfaces 68 of the main-current contacts 52. Due to the fact that the two contact surfaces 48 and 68 are inclined to the axial direction and the contact bridge 48 is moved in an axial direction towards the main-current contacts 52, the contact surface 58 of the bridge contact 48 _10can, by means of the resulting contact pressure, be moved radially inwards towards the part 24. By means of this radial resilient movement of the contact surfaces 58, a violent impact between the bridge contact 48 and the main-current contacts 52 can be avoided, thereby preventing chattering of the contacts and therewith the disadvantages described above, in particular the danger of welding of the contacts. The resilient force of the contact surfaces 58 is automatically adjusted by the material of the entire bridge contact 48 in such a way that a sufficiently large contact pressure remains.

A further advantage arises in that the contact area over the whole contact surfaces 58 or 68 is enlarged by means of the axial inclination of the surfaces and an over-all improvement in dissipation of heat, built up unavoidably during the switching process, is possible.

In further embodiments, not illustrated here, the formation of the contact surfaces 58 and 68 can be such that these surfaces comprise, for example, a spherical-cap shape and/or are provided with undulations on their outer surfaces which lead to a further enlargement of the contact surfaces.

Figure 3 illustrates a further possibility for the formation of the contacts of the engagement -11solenoid relay shown in Figure 1. The same parts are provided with the same reference numbers. In Figure 3, the bridge contact 70 is formed as a disc disposed on the step 62 of the liner 46. The contact bridge 70 thus comprises at its outer surface chamfered edges 72 extending in an axial direction so that the contact bridge 70 is in the shape of a truncated cone. The edges 72 thus simultaneously form the contact surfaces 74. The truncated cone is constructed in such a way that the larger diameter region of the contact bridge 70 is situated at the side nearest to the solenoid core 12. In contrast to this. the larger diameter region of the main-current contacts 52, which regions are formed as a head 64, comprise spring elements 78 at their contact surfaces 76. The spring elements 78 are riveted in a recess 80 on the inside of the head 64. The spring elements 78 are in direct contact with the contact surfaces 76. By means of the sudden impact, described above, of the bridge contact 70 with the main-current contacts 52. pressure is exerted by way of the contact surfaces 74 of the contact bridge 70 on the contact surfaces 76 of the main-current contacts 52, which pressure causes radial movement of the contact surfaces 76 of the main-current contacts 52 which are also inclined to the axial direction. A chatter-free and therefore contact- weld-free -12connection of the main-current contacts 52 by means of the contact bridge 70 is thereby possible.

Figure 4 illustrates a further embodiment of the contacts of an engagement solenoid relay according to the invention, wherein the same parts are again provided with the same reference numbers. The contact bridge 48 is here constructed analogously to the contact bridge 48 shown and explained in Figure 2, so that it is not necessary to go into further details here. This embodiment differs therefrom in that an angular contact part 82 is disposed on each of the heads 64 of the main-current contacts 52. The contact part 82 consists of a base region 84 and an angular contact region 86 bent inwards. The base region 84 is fixedly connected with the head 64 of the main-current contacts 52 by means of wobble rivets or by welding or soldering. The contact region 86 is inclined to the axis, towards the base region 84 to such an extent that the contact surface 88 situated at the contact region 86 lies parallel to the contact surface 58 of the contact bridge 48. By means of this arrangement the contact region 86 produces, in respect of the base region 84, a part which is resiliently movable in a radial direction. When the engagement solenoid switch 10 is triggered, the part 24 is then again guided in an axial direction towards the housing cover 42 and -13thus by means of the contact bridge 48, produces an electrically conductive connection between the main current contacts 52. By means of this special embodiment of the contact bridge 48 or of the contact parts 82, a radial resilient movement of the contact surfaces 48 or of the contact region 86 arises when contact of the contact of the contact surfaces 48 and 88 is brought about at a predetermined pressure.

Hereby it is possible in a particular advantageous manner, to avoid chatter during the contact operation and at the same time to balance out, in a convenient manner, any manufacturing tolerances which would arise during production of a rigid contact.

Consequently with every contact operation of the engagement solenoid switch, even after long and frequent use. a contact pressure of the same level is produced so that a reliable connection of the main current contacts 52 can be produced at any time.

In the plan view shown in Figure 5 of a contact bank, which is here illustrated in the closed state, it is clear that the contact surface 58 of the bridge contact 48 fits closely against the contact surface 88 of the contact part 82 in a locking manner.

Furthermore. the conical or spherical-cap form of the segments having peripheral surfaces producing the -14contact surfaces 58 or 88 is clearly shown here. By means of this conical, semi-circular shaped construction of the contact regions 86, a maximum size contact surface, having the overall round shaped contact bridge 48, is achieved.

It is feasible, in a further embodiment of the invention, that the contact bridge 48 is mounted rotatably around the step 62 of the liner 46. so that in each case different circular segments of the bridge contact 48 from Figure 6 are available to produce the contact and thus on the whole a longer service life of the bridge contact 48 can be achieved. It is thus possible to dispense with the costly to manufacture arrangement of the contact bridge 48.

In a perspective view in Figure 6,'the arrangement of the contact elements corresponding to the embodiment shown in Figure 4 is shown. The spherical-cap form of the contact bridge 48, which has an opening 92 in its middle part 90. and which serves to receive the step of the liner 46, is clearly evident. The contact parts 82, disposed on the main current contacts 52, have at their contact regions 86 a peripheral surface corresponding to the sphericalcap form of the bridge contact 48 and producing the contact surfaces 88. The bridge contact 48, as well as the contact parts 82, can be produced in a -15convenient manner from sheet metal pieces, for example copper sheet pieces, which can be bent or pressed into the desired form without a need for machining.

1

Claims

-16CLAIMS

1. An electro-magnetic relay, having a solenoid core with which a relay coil is associated, and having a armature comprising a switching pin, which extends through an opening of the solenoid core and at one of its ends carries a contact bridge protruding into a contact chamber, which contact bridge has contact surfaces disposed in an axial direction and associated with main-current contacts, which have contact surfaces, wherein the contact bridge and the main current contacts have contact surfaces which are inclined to the axial direction and at least one of the contact surfaces is formed resiliently in a radial direction.

2. An electro-magnetic relay according to claim 1, wherein the contact bridge is formed as a contact disc ozz contact plate and has a conical or sphericalcap-shaped peripheral surface forming a contact surface which extends radially outwards at the relay coil side.

3. An electro-magnetic relay according to claim 1 or 2, wherein the contact bridge is a drawn, deepdrawn or pressed sheet metal piece.

4. An electro-magnetic relay according to any preceding claim, wherein the contact surface of the contact bridge has undulations on its outer surface.

1

5. An electro-magnetic relay according to any preceding claim, wherein the head of each of the main current contacts has inclined edges producing contact surfaces.

6. An electro-magnetic relay according to any preceding claim, wherein the edges are formed conically or shaped as a part-spherical-cap.

7. An electro-magnetic relay according to any preceding claim, wherein the contact bridge is formed as a disc which has edges which are inclined to the axial direction and form contact surfaces.

8. An electro-magnetic relay according to any preceding claim. wherein the contact bridge is rotatably mounted on a step of a liner of insulating material.

9. An electro-magnetic relay according to any preceding claim, wherein the head of each of the maincurrent contacts has a contact part which has a contact region inclined towards its base region to the axial direction.

10. An electro-magnetic relay according to any preceding claim, wherein the contact part is formed as a single part and is fixed by its base region onto the head of the main current contacts in an electrically conductive manner in such a way that the contact region is directed towards the contact surfaces of the 9 -18contact bridge.

11. An electro-magnetic relay according to any preceding claim, wherein the contact region has a surface structure adapted to the contact surfaces of the contact bridge.

12. An electro-magnetic relay according to any preceding claim, wherein the head of each of the main current contacts has a recess in which contact surfaces formed as segments of a circle, of spring elements are arranged.

13. An electro-magnetic relay substantially as herein described with reference to and as illustrated in the accompanying drawings.