EP0232765B1 - Electric switch, particularly for motor vehicles - Google Patents

Description

The invention relates to a switch, in particular for motor vehicles, according to the features of the preamble of claim 1.

In modern motor vehicles, switches with a snap-action switching system are increasingly being installed because these switches have advantages in terms of switching capacity and service life.

From DE-B-2 122 403 such a switch with a snap switch system is known, which is designed as a toggle switch. In this known embodiment, the snap spring is supported on one side in a fixed cutting edge bearing. On the opposite side, the snap spring is clamped in a swivel part, in which case this swivel part is formed directly as an actuating element.With such a design, the switching movement is initiated at one end, the snap spring being introduced due to the fixed clamping of the snap spring in this swivel part Deflection is predetermined in a way during the switching of the snap spring. The snap spring will bend in an S-shape during the switching process, which is advantageous because then when the switching process is initiated, the contact pressure is first increased. This has a favorable effect on the service life and the switching capacity of the switch.

However, the known switch cannot be used in all cases because a push-button switch is often required instead of a toggle switch. A push button switch with a snap switch system is known for example from DE-C-30 39 419. In this known embodiment, the linear movement of the actuating element designed as a pushbutton is transmitted to the movable contact tongue via a switching star with a switching cam. The switching force is therefore not introduced directly into one end of the snap spring. In such a pressure switch, the switching forces for switching the snap-action switching system differ because the cam body acts on the contact tongue with the lever arms of different lengths. This uneven shift feeling is often criticized by customers.

From DE-U-1 684 844 and from DE-B-1 098 073 push button switches according to the preamble of claim 1 are known, in which the switching plunger is pivotable relative to the push button and one in the idle state in the by the axis of rotation of the rocker switch and the direction of displacement the push button has a certain level. Depending on the position of the rocker switch, the actuating approach plunges into one or the other of two engagement notches of a switching curve of the switching rocker facing the switching plunger and is pivoted to the side by the shape of the switching curve and the tilting of the switching rocker.

In the push-button switches from DE-U-1 684 844 and DE-B-1 098 073, the switching plunger is acted upon by a helical spring so that it returns to its middle rest position after each actuation of the switch. This means that when the switch is actuated until the rocker switch begins to switch, a certain free travel and thus a relatively large stroke of the pushbutton is necessary.

Also, the actuating lug of the shift plunger first slides along the engagement notch and the rocker switch is only moved when the tip of the actuating lug strikes the notch. This means that initially only the force of a compression spring dividing the pushbutton is overcome and only after a certain actuation path does the actuation force increase sharply, because then the snap spring is also additionally stressed. Some customers object to this sudden increase in force during operation.

A relatively large stroke of the pushbutton and an abrupt increase in force also shows a pushbutton switch of the generic type known from DE-C-817 319. In this pushbutton switch, the switching plunger is formed by an arm of a leaf spring which is clamped into the switch housing at the side of the pushbutton, is slightly curved towards the pushbutton and merges into the arm in an arc adjacent to the pushbutton, which extends in the rest position of the pushbutton along its direction of movement and, due to its inherent elasticity, extends like the push-buttons of the pushbutton switches according to DE-U-1 684 844 and DE -B-1 098 073 is in a central position with respect to the rocker switch.

The invention has for its object to develop an electrical switch with the features from the preamble of claim 1 so that the idle stroke can be reduced in a simple manner and a jump in the amount of actuating force can be avoided.

This object is achieved in that an electrical switch in addition to the features from the preamble of claim 1 is additionally equipped with the features from the characterizing part of claim 1. With such an electrical switch, the switching plunger is always aligned exactly in the end region of an engagement notch so that there is no long sliding along the notch. As a result, the idle stroke is smaller and the actuating force increases to a certain extent linearly. Since it is no longer necessary to slide the switching plunger along an engagement notch, the two engagement notches on the switching rocker in the switches from DE-U-1 684 844 and DE-B-1 098 073 and DE-C-817 319 can be found on the switching rocker merge into a single recess on the switching plunger, in which there is no longer a tip.

In the case of a switch according to the invention, the respective rest position of the switching plunger is obtained without a part which is present in addition to the rocker switch and the switching plunger, that is to say in a very simple manner.

Advantageous configurations of an electrical switch according to the invention can be found in the subclaims.

So it is favorable if, according to claim 2, the snap spring is clamped at the other end in the rocker switch.

In the case of a switch according to the invention, close tolerances must be observed in order to ensure that it functions properly. Therefore, in the preferred embodiment according to claim 3, the snap spring is supported on both sides on the same part, preferably on a correspondingly shaped fixed contact.

In a switch according to the invention, the two end positions of the rocker switch are determined by the pretension of the snap spring in the two switch positions. If the axis of rotation of the rocker switch according to claim 4 is between these two stops, there is a symmetrical arrangement such that the switching force that must be exerted via the switching plunger is the same in both switching directions.

A particularly firm connection between the snap spring and the rocker switch and an exact assignment of these two parts is obtained in an embodiment according to claim 5.

In principle, as in the switch known from DE-B-2 122 403, the contact tongue could be formed separately from the snap spring, which is certainly advantageous for switches with a high current load. If the switch only has to switch low currents, an embodiment is preferred for reasons of cost in which the contact tongue is formed in one piece with the snap spring.

In an electrical switch according to the invention, it is particularly advantageous if the snap spring is switched from one end position to the other end position with as little friction as possible. This cannot be guaranteed with the support of the snap spring end in a cutting edge bearing known from DE-GM 1 684 844. An embodiment is therefore preferred in which the snap spring projects with at least one attachment into an opening, preferably at a fixed contact, the height of this opening allowing the snap spring attachment to move freely. In such an embodiment, the free end face of the snap spring is supported linearly on the fixed contact in the two switching positions of the snap spring on the side of the attachment, so that increased friction when switching is not to be expected.

It was mentioned at the beginning that the snap spring bends in an S-shape during the switching process. There are therefore areas that are subject to relatively high stress. In the interest of a long life of this snap spring, it is therefore proposed to design the snap spring so that it has a larger cross section in these areas of greater stress than, for example, in the support points or the clamping point on the rocker switch. In addition, in the interest of a long service life and, at the same time, the greatest possible freedom from bouncing, the contact tongue should be designed in such a way that it tapers from the section merging into the snap spring to the area carrying the contact.

Fig. 1

einen Schnitt durch das Ausführungsbeispiel senkrecht zur Drehachse der Schaltwippe,

Fig. 2

einen Schnitt entlang der Schnittlinie II-II in Figur 1,

Fig. 3

in vergrößerter Darstellung die Lagersteile der Schnappfeder an einem Festkontakt,

Fig. 4

eine Ansicht in Pfeilrichtung B in Fig. 3,

Fig. 5

eine Prinzipskizze des Schnappschaltsystems und

Fig. 6

eine Ansicht auf eine Schnappfeder.

The invention and its advantageous embodiments are explained below with reference to the embodiment shown in the drawing. Show it:

Fig. 1

2 shows a section through the exemplary embodiment perpendicular to the axis of rotation of the rocker switch,

Fig. 2

2 shows a section along the section line II-II in FIG. 1,

Fig. 3

in an enlarged representation the bearing parts of the snap spring on a fixed contact,

Fig. 4

3 shows a view in the direction of arrow B in FIG. 3,

Fig. 5

a schematic diagram of the snap switch system and

Fig. 6

a view of a snap spring.

In Figures 1 and 2, 10 denotes the base plate of the switch on which the snap-action switching system is built. This switch includes a plurality of contacts 11, 12 and 13 as well as a pretensioned snap spring 15 with a movable contact tongue 16 formed integrally therewith with a contact bead 17 which interacts with the angled stops on the fixed contacts 12 and 13. The snap spring 15 is supported on one side at a fixed bearing, namely the fixed contact 11, which will be explained in detail later. On the opposite side, this snap spring 15 is clamped in a rocker switch 18 which is pivotally mounted in the switch housing. It is advantageous to mount the rocker switch on two side wings of the fixed contact 11, since then the two support points of the snap spring 15 are ultimately located on the same part and the distance between the two support points is exactly maintained, which is important for proper switching behavior. Since the fixed contact 11 rests with respect to the housing, the rocker switch 18 then has an axis of rotation fixed to the housing as if it were stored directly in the housing. The rocker switch 18 has on one end face a recess 19 with two stops 41, 42 for a switching plunger 20 which is pivotally mounted on an actuating element 21 designed as a pushbutton about the pivot point DP. This pushbutton 21 is guided in a linearly displaceable manner in the housing designated by 22, guide webs 23 sliding in corresponding guide receptacles 24 of an intermediate plate 25.

It can be seen from FIGS. 1 and 2 that the rocker switch 18 is formed separately from the actuating element 21. This rocker switch can alternately be switched from one end position to the other by actuating the pushbutton 21, the switching plunger 20 engaging in the recess 19 when first actuated at the stop 41 and then after the pushbutton springs back, which is accomplished by the compression spring 26, is aligned with the stop 42 near the end of the recess 19 so that during the next switching operation this switching plunger 20 then engages the switching rocker 18 there and switches it back into the position shown. The end positions of the rocker switch 18 are determined by the deflection of the snap spring 15. To switch this snap system via the pushbutton 21, you will need exactly the same switching forces if you arrange the axis of rotation of this rocker switch 18 on the central plane M between the two stops formed by the bent ends of the fixed contacts 12, 13.

It can be seen in particular from FIGS. 3, 4 and 6 that the snap spring 15 has two lugs 30, 31 which protrude into corresponding openings 32, 33 on the fixed contact 11. The height H of these openings 32, 33 is selected such that the free movement of the lugs 30, 31 in the openings 32, 33 is ensured. The snap spring 15 should therefore not be bent in the transition zone to the shoulders 30, 31, which would be the case if the height H of the openings 32, 33 corresponded approximately to the thickness of the snap spring 15. Due to this special design of the support of the snap spring 15 at the fixed bearing point, friction-free mobility of the snap spring 15 is achieved, which in the area between the projections 30, 31 is only in linear contact with the fixed contact 11, as is indicated in FIG. 3 for L. .

The snap spring 15 is fixed in position in the rocker switch 18, because this snap spring 15 is preferably inserted into an injection mold and then the rocker switch 18 is injection molded.

5, the principle of the snap system is shown on an enlarged scale. It can be seen that the snap spring 15 is pretensioned between its support points and is therefore slightly curved. The contact bead 17 on the contact tongue 16 is in one switching position on the fixed contact 13. If the switching rocker 18 is now pivoted clockwise by the switching plunger, the snap spring bends according to the bending line BL. The snap spring 15 assumes an essentially S-shaped position. It is important that the end region of the snap spring supported on the fixed contact 11 has a greater curvature when the switching process is initiated, as is indicated by the broken line. Since the contact tongue 16 is molded onto this end region of the snap spring 15, the contact bead 17 is initially pressed with a greater force against the associated fixed contact 13 when the switching process is initiated. During the switching process, an increase in contact pressure occurs first, which is very important for the switching behavior.

In the electrical switch shown, the switching plunger 20 is pivotally mounted on the push button 21. It can be seen from FIG. 1 that the position of the rocker switch 18 determines the rest position of the switching plunger 20 via an elastic intermediate member 60, which is consequently essentially aligned such that it points directly into an end region of the recess 19. If the push button 21 is actuated in this switch, then only a very small idle stroke with a small actuating force has to be overcome until the switching plunger 20 abuts the switching rocker 18. After overcoming the idle stroke, the actuation force increases rapidly without a noticeable jump. This measure gives a good shift feeling.

A spring-elastic web 60, which is integrally formed on the rocker switch 18 and acts on the switching plunger 20 beyond the axis of rotation DP, serves as an elastic intermediate member. To this end, the end of this web 60 projects between two drivers 61, 62 at the end of the switching plunger 20 and thus determines the rest position of the switching plunger as a function of the switching position of the switching rocker 18.

From Fig. 2 it can be seen that the switching plunger 20 is pivotally mounted in a keyhole-like locking receptacle 63 on the push button 21.

Otherwise, the structure of the snap-action switch system in the switch according to FIGS. 1 and 2 essentially corresponds to the principle according to FIG. 5, so that further explanations are unnecessary. The snap spring 15 is - as shown particularly clearly in FIG. 5 - very heavily stressed, certain areas being exposed to greater loads. The shape of the snap spring is therefore preferably chosen so that it withstands these different loads even after a large number of switching operations, without the mass of the snap spring being increased inadmissibly. From Fig. 6 it can be seen that the snap spring 15 is stamped in one piece with the contact tongue 16 from a circuit board in such a way that two longer legs 70, 71 are connected to one another by ends 72.73. The web 72 lies against the stationary bearing point, that is to say against the fixed contact 11, while the opposite web 73 is clamped into the rocker switch 18. The contact tongue 16 extends from the web 72 near the stationary bearing point and extends parallel to the longer leg 70, 71. It is now essential that the longer legs 70, 71 have a larger width in their central region than in the transition zone to the connecting webs 72 and 73, because greater loads occur in this central region during the S-shaped deflection. The contact spring tongue 16 has an essentially triangular contour with the base on the connecting web 72 and the tip in the area of the contact bead 17. In this way, the mass of this contact tongue is chosen so small with sufficient load-bearing capacity that there is no fear of the switch bouncing.

Claims (10)

1. An electric switch, especially for motor vehicles, comprising a housing, a push-button switch (21) which is movable preferably linearly relative to the housing, comprising a switching tappet (20) displaceable with the push-button (21) and swivellable relative to the latter, a switching rocker (18) rotatably mounted in the housing and alternately to be swivel led to and fro between two end positions, and comprising a snap spring (15) supported on the switching rocker and by its one end on a bearing (11) fixed to the housing and coupled with a movable contact (11) which co-operates with at least one stationary contact (12, 13), characterised in that the switching rocker (18) defines the rest position of the switching tappet (20) via a resilient web (60) made in one piece with the switching rocker (18) and projecting from it, which web (60) - looked at from the axis of rotation of the switching rocker (18) engages at the switching tappet (20) beyond the axis of rotation (DP) of the switching tappet (20).
2. An electric switch according to claim 1, characterised in that the snap spring (15) is fixed at the switching rocker (18) with its other end.
3. An electric switch according to claim 1 or 2, characterised in that the snap spring (15) is one-sidedly directly supported on a stationary contact (11 and that the switching rocker (18) is also swivellably mounted on this stationary contact (11).
4. An electric switch according to one of claims 1 to 3, characterised in that the axis of rotation of the switching rocker (18) is arranged on the centre plane between two stops (12, 13) determining the switching positions of the snap spring.
5. An electric switch according to one of the preceding claims, characterised in that the snap spring (15) is embedded in the switching rocker (18).
6. An electric switch according to one of the preceding claims, characterised in that the reed (16) formed as a movable contact together with contact beads is made in one piece with the snap spring (15), especially is formed of a sheet metal strip.
7. An electric switch according to one of the preceding claims, characterised in that the snap spring (15) projects into an aperture (32, 33) on the stationary contact (11) by means of at least one stud (30, 31), the height (H) of the said aperture (32, 33) permitting a free movability of the snap spring stud (30, 31).
8. An electric switch according to one of the preceding claims, characterised in that the snap spring (15) has two longer shanks (70, 71) and two webs (72, 73) connecting these shanks, one web (72) having studs (30, 31) for a support on the stationary contact (11) and the other stud (73) being fixed at the switching rocker (18), and that, beginning from the web (72), the reed (16) extends alongside the longer shanks.
9. An electric switch according to claim 8, characterised in that the longer shanks (70, 71) have a larger width in their centre area than in the transitional area to the webs (72, 73).
10. An electric switch according to claim 8 or 9, characterised in that, beginning from the web (72), the reed (16)is preferably triangularly tapered.

Images