DE102004029715B4 - Electromagnetic switching device for switching high inrush currents and measures for separating emerging adhesive and welded connections at the contacts - Google Patents

Abstract

Electromagnetic switching device having a lever (1) movably mounted in a housing (11) and carrying a first contact (4) supported by a spring (2), the first contact (4) being positively guided relative to the lever (1) is movable, wherein the lever (1) is drivable to move the first contact (4) against a fixed second contact (7), wherein the lever (1) has a support arm (10), the first contact (4) leads, wherein the first contact (4) and the support arm (10) by the engagement of a guide cone (12) in an embossment (13) are positively connected to each other and wherein during a closing movement of the first contact (4) at a lower contact point (FAu ) and an upper support point (FAo) rests on the support arm (10) of the lever (1) and the lever (1) is moved until contact of the first contact (4) with a stop (6) of the lever (1) and during the Closing movement contact surfaces of contact rivets (8, 9) of the ers ten contact (4) and the second contact (7) are not only pressed together, but simultaneously roll on each other and slide as a result of triggered by the stop (6) tilting movement of the first contact (4) relative to the lever (1).

Description

The invention relates to an electromagnetically driven switching relay, which has one or more controlled via a shift lever contacts for closing and opening of electrical circuits. Such switching devices are used for example in the building installation technology for switching different lamp loads.

In many applications of electrical switching devices depending on the type of electrical load (lamp, motor, valve, ...) inrush currents that are many times greater than the continuous currents themselves. With incandescent loads, the contact current load increases in the switch-on z. B. to ten times the value of the continuous current. This is often associated with a very high electrical and thermal stress on the contacts, which can then Kontaktverschweißungen result.

Due to the very high level of heat, the switch-on arc, whose temperature is between 2,000 and 10,000 ° C, has a major influence on the contact surfaces. This often Entfestigungs- and melting temperatures of the contact material can be achieved, which then glue the contact at the confluence of molten contact surfaces (easily solvable) or weld (massive metallic compound). Adhesive or welded joints on electrical switch contacts can never be avoided with complete safety.

An electromagnetic switching device is from the JP H09 161639 A known. This switching device has a holder, a first contact and a second contact, wherein the holder is drivable to move the first contact against the second stationary contact. However, in this switching device is not ensured that the movable first contact maintains its position over the entire stroke, which can represent next adhesive or welded joints on electrical switch contacts another unwanted contact connection. Furthermore, in the case of this switching device, contact wear can occur on impact of the first contact with the second contact, as a result of which the contact service life is shortened.

From this, the task is derived from countering the undesirable contact connections by targeted and appropriate design measures and thus to master them in practice. This is on the one hand to achieve the highest possible electrical contact life of importance, on the other hand, but also to achieve the required switching safety and low error rate in the course of the specified life.

This object is achieved by a switching device according to claim 1.

During the development and construction of the electromechanical switching device, all switching-device-specific influencing variables determining the thermal load, such as the reaction time of the drive (t _on ), contact _{bounce time} (t _bounce ) and also the arc _burning time are reduced to a minimum.

The closing mode of the contact (relative movement, rolling and sliding movement ...) and the contact forces (closing and opening forces) are simultaneously brought to the best possible level. This also applies to the material engineering and geometric definition of all live components to z. B. to dissipate the resulting heat sufficiently and quickly.

In the following the invention is explained in more detail in an embodiment. The show 1 to 4 schematically the switching device in four successive positions of the movement from the rest position to the full closed position. In 5 the case of a fault is shown by "contact welding".

One in the housing system 11 movably mounted lever 1 carries one through the compression spring 2 supported contact 4 , In order to withstand mechanical shock and vibration stresses are the contact 4 and the support arm 10 through the engagement of the guide cone 12 in the coinage 13 positively connected with each other. This ensures that the contact 4 maintains its position throughout the entire stroke (a + h).

The lever 1 is by the force F _{S of} a drive system, not shown, by the travel a or (a + h) against the fixed contact 7 emotional. Thus, the closing movement has taken place and the required contact force F _K2 arises between the contact rivets 8th . 9 as a result of the effective spring force F _K1 . During the closing movement, the contact surfaces of the contact rivets 8th . 9 not only compressed, but they roll and slide simultaneously on each other, as a result of the attack 6 triggered tilting movement of the contact 4 ,

1 : Shows the rest position of the contact.

2 : Lever 1 was moved from the rest position by the distance a (≙ contact opening) in the direction of X. The contact pieces 8th . 9 are just touching each other, ie F _K2 → 0. Contact 4 is located at the lower support point F _Au and the upper support point F _Ao . Hub h is unchanged.

3 : Lever 1 was based on the position of the 2 around the stroke h of the contact 4 until touching with stop 6 moved further in the direction of X. Contact force F _K2 between the contact pieces 8th . 9 is effective. Contact 4 lies at the top with F _Ao on the support arm 10 and simultaneously with F _Au at the stop 6 of the lever 1 at. Hub h adjusts itself as stroke h '(h = h').

4 : Lever 1 was based on the position of 3 moved so far in the direction X that the tilting about the pivot point D contact 4 from the upper contact point (F _Ao ) to the distance S lifts. This raises a higher contact force F _{K2 '} between the contact pieces 8th . 9 a (F _{K2 '} > F _K2 ), with simultaneous rolling and sliding movement of the contact surfaces. The guide cone 12 remains in the coinage 13 still engaged. The desired closing of the contact is hereby completed. The opening process is in the reverse direction of X 'vonstatten.

5 : Shows an error. Contacts are welded due to high thermal loads. Contact 4 occupies a fixed position as shown. lever 1 is pulled by an associated return force F _back to the starting position. In this case, a breaking moment M _A becomes effective around the contact point k (M _A = F _back × L ₃ ). As a result of this leverage the welding forces are released and the contact opens and takes again the rest position lt. 1 one.

Assuming that the contact 4 in the welding trap the in 4 shown position, so comes to the Aufbrechwirkung of the moment M _A additionally a jerky, dynamic force at the support point between the support arm 10 and the padding 5 to the effect. This further increases the probability that the contact seals will be removed and the switching device will continue to function.

The switching device according to the invention offers the following advantages:
The closing movement takes place under a simultaneous rolling and sliding movement of the contacts. As a result, the sticking and welding tendency of the contacts is substantially reduced. When switching small loads, this relative movement has the effect of self-cleaning the contact surfaces (destruction of oxide layers).

This closing mode favors the contact bounce behavior, as the dynamic forces occurring when the contacts strike are largely absorbed by the rolling and sliding (rubbing) and thus prevent a damaging, long quake.

The stop 6 acts to dampen the dynamic forces acting on the contacts as well as the contact bumpers. As a result, the contact wear is reduced or the contact life is significantly increased.

The stop 6 increases due to the inevitable tilting movement of the contact 4 the contact force F _{K2 '} . As a result, both the contact life and the switching reliability of the switching device is increased.

In the case of Kontaktverschweißungen acts during the return movement opening movement) of the lever 1 a breaking moment M _A at the contact point k against the welding forces and thereby breaks the connection. The switching devices thus remain much longer functional.

LIST OF REFERENCE NUMBERS

a

contact opening

d

Tipping direction of the contact 4

D

Pivot to which the contact 4 tilts in direction d

F _Ao

Upper contact force of the contact 4

F _au

Lower contact force of the contact 4

F _{au '}

Lower contact force of the contact 4 at the stop 6

F _K1

Spring force used to press the contact 4 on lever arm 10 and to build up the contact force F _K2 on the contact pieces 8th . 9 needed is F _K2 contact force between the contact pieces 8th . 9 is effective

F _{K2 '}

Contact force, which is in the end position of the switching contact between the contact pieces 8th . 9 established. F _{K2 '} is due to the tilting movement of the contact 4 around point D, greater than F _K2

F _return

At the lever 1 effective restoring force or on the support arm 10 attacking breakaway power

F _S

Operating force of the drive system, not shown in the figures

H

Hub of contact 4 inside the lever 1 (until the stop 6 )

H'

Stroke of the lever 1 between contact 4 and support arm 10 (h '= h)

k

contact welding

L ₁

Effective lever arm of the contact 4 , from level 0 to the force action line of the spring force F _K1

L ₂

Center point of contact 7 or of the contact rivet 9 viewed from level 0

L ₃

Effective lever arm on the welded contacts

.DELTA.L

Difference amount L ₁ -L ₂

M

The torque which determines the upper bearing force F _Ao

M _A

Aufbrechmoment

s

Distance to which the contact 4 from the support arm 10 lifts as a result of the tilting movement

X

Direction of movement of the lever 1 (Closing movement)

X '

Direction of movement of the lever 1 (Opening movement)

1

lever

2

compression spring

3

Spring guide pin

4

Contact (mobile)

5

circulation nubs

6

Stop (for contact 4 )

7

Contact (fixed)

8, 9

contact rivet

10

support arm

11

Switchgear housing (fixed)

12

Guide cone, as a part of the support arm 10

13

Imprint in contact 4

Claims (2)

Electromagnetic switching device with one in a housing ( 11 ) movably mounted lever ( 1 ), one by a spring ( 2 ) based first contact ( 4 ), the first contact ( 4 ) in relation to the lever ( 1 ) is guided positively guided, wherein the lever ( 1 ) is drivable to the first contact ( 4 ) against a fixed second contact ( 7 ), the lever ( 1 ) a support arm ( 10 ) having the first contact ( 4 ), the first contact ( 4 ) and the support arm ( 10 ) by the engagement of a guide cone ( 12 ) in a coinage ( 13 ) are positively connected with each other and wherein during a closing movement of the first contact ( 4 ) at a lower support point (F _Au ) and an upper support point (F _Ao ) on the support arm ( 10 ) of the lever ( 1 ) and the lever ( 1 ) until touching the first contact ( 4 ) with a stop ( 6 ) of the lever ( 1 ) is moved and during the closing movement contact surfaces of contact rivets ( 8th . 9 ) of the first contact ( 4 ) and the second contact ( 7 ) not only be compressed, but at the same time roll on each other and slide in consequence of the attack ( 6 ) triggered tilting movement of the first contact ( 4 ) opposite the lever ( 1 ). Switching device according to claim 1, wherein the support arm ( 10 ) of the lever ( 1 ) at the opening movement the first contact ( 4 ) if necessary from the second contact ( 7 ) separates.

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