Patent Publication Number: US-8125303-B2

Title: Solenoid switch for starters

Description:
FIELD OF THE INVENTION 
     The present invention relates to a solenoid switch for a starter of internal combustion engines. 
     BACKGROUND INFORMATION 
     Solenoid switches of the abovementioned type are conventional parts of the starting system for internal combustion engines of motor vehicles in multiple refinements, as also in a basic construction that is described in DE 198 14 504. 
     Such solenoid switches have a housing which accommodates a controlling magnet which acts upon a meshing drive via a control connection. Via the meshing drive, and in its meshed control position, the starter is drive-connected to the internal combustion engine in order to start it. 
     Opposite to the actuator acted upon by the magnet, the housing is covered by a switch cover at its end face, while defining an accommodation space. In this accommodation space there are contact surfaces of switch bolts, which pass through the end face wall of the cover and are axially braced with respect to it. For this purpose, the contact surfaces lying within the accommodation space are associated with broadened head parts of the switch bolts, which are supported on the edge of the cover wall next to the passageway opening, with respect to which the switch bolt is axially braced via an opposite nut screwed onto the switch bolt. 
     The switch bolts braced in a fixed position with respect to the switch cover extend outwards beyond the cover and are line-connected to the battery (terminal  30 ) and the starter motor (terminal  45 ). Depending on the respective position in the vehicle, as well as on conditions related to accidents, the switch bolts may also be exposed to abruptly larger forces. A possible break in the cover, caused by this, may lead to a short circuit connection between the switch bolt connected to the battery (terminal  30 ) and the body shell. 
     SUMMARY 
     Example embodiments of the present invention provide a solenoid switch, in such a way with respect to its cover that, without any impairment of the axially bracing fixing of the switch bolts to the cover of the switch, there exists no danger of a break of the cover even at extreme loads acting upon the switch bolts. 
     The design approach according to example embodiments of the present invention relates to, in the case of the fixed-position, durable bracing of the bolts with respect to the switch cover, the switch cover is made of an elastically deformable plastic material, and, regardless of the setting characteristics of such a plastic material, in the case of loads existing because of the axial bracing of the switch bolt with respect to the cover, the fixed and position-ensuring position of the switch bolt is assured by, in the vicinity of the edge zone of a respective passageway opening, the cover being rigid to pressure, i.e. pressure-resistant. 
     Thus, on the one hand, the bracing force required for ensuring the position of the switch bolt, with respect to the switch cover, is able to be maintained and, on the other hand, because of the flexibility of the cover, it is able to be ensured that extreme, particularly abrupt loads acting on the respective switch bolt are able to be at least partially intercepted by appropriate elastic deformations of the cover. 
     The arrangement of the edge zone of a passageway opening, that is particularly edge-enclosing, and axially inflexible, may be achieved, regardless of the rigid design of the cover, made of deformable, particularly elastically deformable plastic in that, during molding of the cover, plastic materials of different elasticity and different setting characteristics are used for the various areas of the cover, the material for the pressure-stressed edge zone of a respective passageway opening being able to be inserted even offset in time, if necessary. 
     An arrangement is also possible, in which the same elastically deformable plastic is used continually for the switch cover, but in the edge zone of a respective passageway opening, in each case a stiffening insertion is made as an insert or framework, which extends between the axially opposite support surfaces, at least over parts of the circumference of the passageway. 
     An example embodiment includes assigning a sleeve to the passageway opening as an edge-side limitation and insert, this sleeve being able to be connected to the base material of the cover in a continuous material or form locking manner. 
     As a deformable, particularly an elastically deformable base material for the cover, especially thermoplastic materials may be provided, while for the axially extending, pressure-loaded edge region of a respective passageway opening, or for the insert assigned to this edge region, thermosetting plastics should be considered, in particular. 
     Further features and aspects of example embodiments are described below with reference to the appended Figures 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows, in a longitudinal center section, a simplified overview of a solenoid switch for starters of internal combustion engines, 
         FIG. 2  shows an end face top view in the direction of arrow II onto the cover of the solenoid switch according to  FIG. 1 , without the switch bolts braced with respect to the cover, and 
         FIG. 3  shows a section according to III-III in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The sectional illustration according to  FIG. 1  shows a solenoid switch  1  for starters of internal combustion engines, in an overview. The switch housing is designated as  2 , which encloses windings  3  of a controlling magnet  4  which, on their part, lie circumferentially to axially shiftable magnet armature  5 . Magnet armature  5  is connected in fixed position to an actuating rod  6 , which is a component of a control connection to a meshing drive, via which the starter is connected to the internal combustion engine when the internal combustion engine is started. Starting systems of this type are described, for example, in “Kraftfahrtechnisches Taschenbuch”, Bosch 23. Edition, ISBN 3-528-03876-4, pp. 571 to 574. Furthermore, DE 198 14 504 shows and describes a solenoid switch which corresponds to the one in  FIG. 1 , in its basic design. 
     Covering a magnetic core  7  that is situated at the end face of switch housing  2 , housing  2  is connected to a switch cover  8 . In this exemplary embodiment, this switch cover  8  is crimped at  9  circumferentially onto switch housing  2 . 
     Switch cover  8  is arranged to be bowl-shaped and delimits an accommodation space  10  from switch housing  2  and magnetic core  7 . 
     Switch bolts  12  and  13 , that pass through switch cover  8  in its end-faced cover wall  11 , end in this accommodation space  10 , of which switch bolt  12 , as terminal  30 , is connected to the battery and switch bolt  13 , as terminal  45 , is connected to the starter motor. Furthermore, a connection  27 —terminal  50 —to the ignition lock is assigned to cover  8 . 
     Switch bolts  12  and  13  extend towards accommodation space  10  ending in head parts  14 ,  15  which have a greater cross section, at least in regions, compared to switch bolts  12  and  13 , and which engage over the peripheral edge zone towards the respective passageway openings  16 ,  17  that accommodate respective switch bolts  12  and  13 . Head parts  14 ,  15  have corrugated contact surfaces  34 ,  35  which are connected via a contact bridge  28 , when current is supplied to solenoid switch  1 , which is adjustable via a switch shaft  29  by magnetic armature  5  and is acted upon counter to the control direction of magnetic armature  5  when current is supplied, by a spring  30  that is situated in switch cover  8 . 
     This axial support takes place in the region of inserts  20 ,  21 , which—see especially FIG.  3 —are provided to be the linings of respective passageway openings  16 ,  17 , and which are formed by sleeves  22 ,  23  in the exemplary embodiment shown. Sleeves  22 ,  23  are each made of a plastic material which is inflexible with respect to the axial bracing forces that are a given in this case, and which has no substantial setting characteristics, and thus is a thermosetting plastic, in particular, and they are form-locking and/or have continuous material with the respectively enclosing region of cover wall  11 , for instance, in that sleeves  22 ,  23  are molded around with the material of cover  8 , during the production of cover  8 . Between sleeves  22 ,  23  and adjusting nuts  18 ,  19  there is in each case a tooth lock washer  31 , respective cable lug  32  and a spring lock washer  33 . 
     Since the forces mounted axially for bracing switch bolts  12 ,  13  are supported via sleeves  22 ,  23 , switch cover  8  may be provided, both with respect to the material and to the shaping, to the extent that forces solenoid switch bolt  12  and  13 , such as forces, for instance, becoming effective, through support, abruptly at parts of the body, because of an accident, only lead to deformations of cover  8 , but not to a break in cover  8 , or to any other type of releasing of respective switch bolt  12 ,  13  from the connection to switch cover  8 , which is especially critical with respect to switch bolt  12  that is connected to the battery as terminal  30 , because of the danger of a short circuit connected with that. 
       FIGS. 1 and 3  show that sleeves  22 ,  23  may be fixed to switch cover  8  both by material locking, as, for instance, by the corresponding adhesion of the working materials during molding, and by form locking, the form-locking fixing being able to be achieved by radial overlapping, at least in regions, of respective sleeve  22 ,  23  and the enclosing part of switch cover  8 . Such undercutting is achieved with respect to sleeve  22  by collar  25 , and with respect to sleeve  21  by collar  26 , collar  25  being designed in step-wise manner, in adaptation to the axially stepped arrangement of switch bolt  13 . 
     In the region between switch bolts  12  and  13 , cover  8  is provided with a rising screening wall  26 . 
     Example embodiments of the present invention provide a design approach in which switch cover  8 , made of plastic, demonstrates overall, at least in the vicinity of cover wall  11 , an elastic behavior, namely in response to a development, that is axially rigid to compression and has no setting behavior, of the edge region enclosing passageway openings  16 ,  17 .