Electric switch with rubbing contact

Abstract

The present invention relates to an electric switch with rubbing contact (3) comprising on the one hand at least one fixed contact (9) and on the other hand at least one moving rubbing contact (3) that can move along a predefined trajectory and exhibiting a contact surface (10) intended to rub on said at least one fixed contact (9), characterized in that at least said contact surface (10) is treated by ion bombardment by virtue of an ion beam, and in that the fixed (9) and moving (3) contacts are bare.

Claims

1. An electrical switch with rubbing contact comprising: at least one fixed contact disposed on a surface of a support; and at least one moving rubbing contact that moves along a predefined trajectory and has a contact surface that rubs across a surface of said at least one fixed contact during a rotational movement of the electrical switch, wherein at least said contact surface is treated by ion bombardment by an ion beam, and wherein the fixed and moving contacts are bare, wherein the at least one moving rubbing contact is U-shaped and has at least three curved branches, wherein two out of the three curved branches extend out of opposite sides of the at least one moving rubbing contact, and wherein a free terminal end of each of the at least three curved branches is stressed towards the surface of the support.

2. The electrical switch as claimed in claim 1, wherein said at least one fixed contact is free of contact grease.

3. The switch as claimed in claim 1, wherein all of the fixed and moving contacts are treated by ion bombardment by an ion beam, at least on the surfaces that can make electrical contact.

4. The electrical switch as claimed in claim 1, wherein the moving rubbing contact is made of one selected from the group consisting of steel, copper, stainless steel, bronze, brass, aluminum or an aluminum alloy.

5. The electrical switch as claimed in claim 1, wherein said contact surface of the rubbing moving contact comprises a nickel plating on a substrate that forms the rubbing moving contact and a noble metal plating on the nickel plating.

6. The electrical switch as claimed in claim 5, wherein the thickness of the noble metal plating is between 0.25 μm and 1 μm.

7. The electrical switch as claimed in claim 1, wherein said contact surface of the rubbing moving contact comprises a noble metal plating on a substrate that forms the rubbing moving contact.

8. The electrical switch as claimed in claim 1, wherein said contact surface that rubs across the surface of said at least one fixed contact has a curved surface having a first radius of curvature of between 0.5 mm and 5 mm in a direction of movement of the rubbing moving contact and a second radius of curvature of between 0.5 mm and 2 mm in a direction perpendicular to the movement of the rubbing moving contact.

9. The electrical switch as claimed in claim 1, wherein the fixed and moving contacts are dimensioned to convey a high current, notably greater than 1 A.

10. The electrical switch as claimed in claim 1, wherein the fixed and moving contacts are dimensioned to convey a low current, notably less than 20 mA.

11. The electrical switch as claimed in claim 1, wherein, for the treatment by ion bombardment, ions of the atoms of the group consisting of noble gases, nitrogen or boron atoms are chosen.

Description

(1) Other features and advantages of the invention will emerge from the following description, given as a nonlimiting example, in light of the attached drawings in which:

(2) FIGS. 1a and 1b are plan views of an electrical switch with rubbing contact according to the invention,

(3) FIGS. 2a and 2b are side and front views of ends of a moving rubbing contact,

(4) FIG. 2c is a cross-sectional view of an end of FIG. 2a, and

(5) FIG. 3 is a plan view of a fixed contact support of the electrical switch with rubbing contact.

(6) In these figures, identical elements bear the same reference numbers.

(7) FIGS. 1a, 1b and 3 illustrate an exemplary embodiment of an electrical switch with rubbing contact 1.

(8) Such an electrical switch 1 can, for example, be incorporated in a steering wheel control module for a motor vehicle, particularly to perform the electrical switch of safety functions such as, for example, control of the lights, of the windscreen wipers, etc., or else in a motorized windscreen wiper blade drive system for controlling the back and forth motion of the wipers.

(9) The figures show an electrical switch for low current, that is to say for conveying a current less than 20 mA.

(10) As an alternative, the invention can be transposed to an electrical switch for high current, that is say greater than 1 A, which is distinguished from a low current switch in particular by the increased cross section of the conductors so as to be able to convey this high current.

(11) This electrical switch 1 comprises, on the one hand, at least one, in FIG. 1a several, fixed contacts 9 arranged on a support 7. The support 7 is, for example, a printed circuit board and the fixed contacts 9 are contact lands.

(12) Electrical tracks of this printed circuit board link the fixed contacts 9 to an electrical control circuit.

(13) FIGS. 1 to 3 show a support 7 having a pierced center 8 so as to allow the passage of a lever and electrical wires for a steering wheel control stalk.

(14) As illustrated in FIGS. 1 to 3, the fixed contacts 9 are arranged in a circle on the support 7.

(15) It can thus be seen, in FIG. 3, that the support 7 comprises eight fixed contacts 9 in the form of circular arc strips.

(16) The fixed contacts 9 thus define four different switching states of the electrical switch 1, given that, for dependability reasons, the fixed contacts 9 are duplicated in this example.

(17) An additional fixed contact 14 is also provided, in the form of a ring, and linked to a power supply or to the ground.

(18) This additional fixed contact 14 is, for example, arranged concentrically to the circle formed by the fixed contacts 9.

(19) Also, the electrical switch 1 comprises at least one moving rubbing contact 3 that can move along a predefined trajectory; in this case a circular arc trajectory is able to bring it into contact with one or more of the fixed contacts 9. This trajectory is at least partially parallel to the plane defined by the support 7, that is to say the printed circuit board. According to the example shown in FIGS. 1a and 1b, the subject is a rotary switch and the moving rubbing contact 3 can therefore describe a rotational movement.

(20) According to a variant that is not represented, the moving rubbing contact can be produced in the form of a carriage moving along a straight-line trajectory so as to be able to make contact with fixed contacts arranged in a line.

(21) The moving rubbing contact 3 is, for example, linked to a control lever, notably for controlling the headlights or windscreen wipers. Thus, by the movement exerted by a user on the control lever, the moving rubbing contact 3 is moved along the predefined trajectory.

(22) The switch 1 can thus make an electrical contact for one or more predefined positions of the moving rubbing contact 3 with at least one corresponding fixed contact 9 borne by the support 7.

(23) As can be seen in FIGS. 1a and 1b, the moving rubbing contact 3 takes the form of a fork that has at least two, here three, branches 11, 12, 13, advantageously flexible, mounted on a moving base.

(24) The moving base also comprises means for fixing to a control element of the device (not represented).

(25) The branches 11, 12 are able to make two simultaneous electrical contacts with two corresponding fixed contact 9 and are duplicated to improve the dependability.

(26) The branch 13 is in rubbing contact with the additional fixed contact 14.

(27) The rubbing contact 3 comprises, on each branch 11, 12, 13, a curved end 5 stressed toward said support 7, Thus, depending on its angular position, the domed part of the curved end 5 makes frictional contact with the corresponding fixed contact 9, to make an electrical contact. The end 5 of each branch therefore forms a contact surface 10 intended to rub on said at least one fixed contact 9.

(28) At least this portion of the end 5 of each branch intended to rub on a fixed contact 9 is treated by ion bombardment by an ion beam.

(29) This treatment by ion bombardment confers on this treated portion a better surface condition reducing friction. Furthermore, this better surface condition prevents the contamination of the rubbing moving contact, for example by silicone.

(30) Furthermore, this treatment makes it possible to prevent the risks of oxidation which makes it possible to keep the contact resistance at an acceptable level throughout the life of the switch.

(31) Furthermore, the fixed 9 and moving 3 contacts are bare, that is to say free of any lubricant, such as, for example, contact grease.

(32) Thus, during the assembly procedure, there is no longer a need to provide a tedious contact grease application step. The elimination of the greasing step makes the switch less of a pollutant to the environment.

(33) According to one development, both the fixed 9 and moving rubbing 3 contacts are treated by ion bombardment by an ion beam. It may be a local treatment only on the surfaces which make contact, or it is also possible to consider a treatment of the fixed and moving rubbing contacts as a whole.

(34) The moving rubbing contact 3 can be made of steel, copper, stainless steel, bronze, brass, aluminum or an aluminum alloy.

(35) The reader's attention is notably drawn to moving rubbing contacts made of steel or stainless steel which are less expensive than contacts made of copper, bronze or brass. In practice, the ion bombardment makes it possible to reduce, even eliminate, the formation of an insulating oxide layer on the moving contact, such that a nickel plating is no longer necessary. In this case, it is envisaged that the substrate of the moving rubbing contact is subject as a whole to the ion bombardment by an ion beam.

(36) For the treatment by ion bombardment of all the embodiments, ions of the atoms of the group made up of noble gases (notably He, Ne, Ar, Kr, Xe), nitrogen or boron atoms are, for example, chosen.

(37) According to a variant, the contact surface 10 of the rubbing moving contact 3 comprises a nickel plating on the substrate forming the rubbing moving contact 3 and a plating of a noble metal, such as gold or silver, on the nickel plating. The ion bombardment in this case takes place after the deposition of the noble metal plating.

(38) According to another variant, said contact surface 10 of the rubbing moving contact 3 comprises only a plating of a noble metal, such as gold or silver, on the substrate forming the rubbing moving contact. This variant also has the advantage of eliminating the nickel plating which is necessary in the prior art to be able to make the noble metal adhere to the substrate, notably made of copper or brass. Therefore, in addition to the elimination of the contact grease, it is possible to dispense with the nickel which also makes it possible to make the switch less of a pollutant for the environment, both in its manufacture and at the end of life. Furthermore, the elimination of the nickel plating also makes it possible to eliminate a step in the manufacturing of the switch and reduce the cost of the electrical switch. In fact, the effect of the treatment by ion bombardment is not only to improve the surface condition of the electrical contact surface, but also to allow for the adherence of the noble metal to the substrate which is in a non-noble metal, and to do so without involving a plating such as nickel, for example.

(39) For these above two variants, provision is made for the thickness of the noble metal plating (gold or silver) to be between 0.25 μm and 1 μm, which is much less than the hitherto known thicknesses of 2 to 3 μm. With the material cost of the noble metals which has increased very significantly in recent times, the significant reduction of the noble metal thickness and therefore of the quantity of noble metal to be applied also allows for a significant reduction in the cost price of the electrical switch.

(40) According to a third variant, no plating is applied to the electrical contact surface 10. This end is therefore treated only by bombardment by an ion beam. This again makes it possible to reduce the manufacturing cost of the electrical switch while ensuring correct operation throughout the life of the electrical switch, and without contact grease.

(41) The following table summarizes the embodiments considered to be the most advantageous, without in any way being exhaustive. What is common to all these variants is that there is no longer any contact lubricant.

(42) TABLE-US-00001 Noble metal Contact Nickel plating (example Treatment by ion Embodiment Substrate lubricant plating gold, silver) bombardment 1 Copper No Yes Yes Electrical contact surface or the entire substrate 2 Brass No Yes Yes Electrical contact surface or the entire substrate 3 Steel No Yes Yes All the substrate 4 Stainless No Yes Yes Electrical contact surface or steel the entire substrate 5 Bronze No Yes Yes Electrical contact surface or the entire substrate 6 Copper No No Yes Electrical contact surface or the entire substrate 7 Brass No No Yes Electrical contact surface or the entire substrate 8 Steel No No Yes The entire substrate 9 Stainless No No Yes Electrical contact surface or steel the entire substrate 10 Bronze No No Yes Electrical contact surface or the entire substrate 11 Copper No No No Electrical contact surface or the entire substrate 12 Brass No No No Electrical contact surface or the entire substrate 13 Steel No No No The entire substrate 14 Stainless No No No Electrical contact surface or steel the entire substrate 15 Bronze No No No Electrical contact surface or the entire substrate 16 Aluminum No No Yes Electrical contact surface or the entire substrate 17 Aluminum No No Yes Electrical contact surface or alloy the entire substrate 18 Aluminum No No No Electrical contact surface or the entire substrate 19 Aluminum No No No Electrical contact surface or alloy the entire substrate

(43) As can be seen in the figures, notably 2a, 2b and 2c, the end 5 of the moving rubbing contacts is domed or curved.

(44) The radius of curvature R of the first domed part of the curved end 5 is between 0.5 mm and 5 mm (FIG. 2c) in the direction of movement of the rubbing moving contact.

(45) The radius of curvature r of the second domed part of the curved end 5 is between 0.5 and 2 mm (FIG. 2b) in the direction perpendicular to the movement of the rubbing moving contact.

(46) It will therefore be understood that it is possible to produce an electrical switch with rubbing moving contact without contact lubricant, even without nickel plating and even also without noble metal which allows for a competitive cost price, a better environmental compatibility while ensuring exemplary dependability.