WO2017102836A1

WO2017102836A1 - Electrical securing device

Info

Publication number: WO2017102836A1
Application number: PCT/EP2016/080990
Authority: WO
Inventors: Mathias Fein; Mark Hellmann; Torsten Knorr
Original assignee: Robert Bosch Gmbh
Priority date: 2015-12-17
Filing date: 2016-12-14
Publication date: 2017-06-22
Also published as: DE102015225762A1

Abstract

The invention relates to an electrical securing device (65), comprising a first conductor (29) and a second conductor (23), which by way of a connecting material (38) are integrally connected to one another both electrically and mechanically such that there is a current path (63) between the first conductor (29) and the second conductor (23), wherein in the connecting material (38), a tensile stress operates by way of a force (F) effected by a spring element (41), characterized in that the spring element (41) is arranged in the current path (63).

Description

Description title

Electric safety device prior art

From the prior art it is known that in starter motors a fuse is used as a so-called overload protection. This fuse is intended to prevent components of the starter from becoming excessively hot when operated for too long or in the event of a fault. In such cases of error, otherwise, for example, could dissolve the molding compound of the commutator and solve the commutator fins in the episode. That the rotor would then eject corresponding commutator blades. For this purpose, it is imperative that parts outside the starter housing are made to glow, otherwise parts of the engine compartment could ignite as a result. Thus, limit temperatures can be defined for each component of the starter, which must not be exceeded in all load and fault cases. The main circuit must be broken in time.

For this purpose, bottlenecks with locally increased resistance are usually installed in today's starters in the main circuit. So the copper strands of the

Carbon brushes have a reduced cross-section or in busbars on the brush holder targeted locally reduces the cross section. A publication which describes targeted bottlenecks is, for example, DE102010063688A1. During operation of the starter or in the event of a fault, the bottleneck heats up. When the melting temperature of the material (e.g., copper or steel) is exceeded, the constriction melts and the main circuit is broken.

Disadvantages of these solutions is that locally temperatures above 1000 ° C (eg copper 1085 ° C or steel about 1500 ° C) are required to melt the material bring. In particular, in load or fault cases in which only a small current flows through the starter, the power loss may not be sufficient to reach the melting temperature. In addition, starters are known (for example, from DE 10 2009 002 725 AI), in which the plus carbon brushes are supplied via a busbar with voltage at the same time (together with the lying at negative potential brush plate) holds the brush holders.

The known solutions described above are all based essentially on the principle of self-heating. Due to the power loss caused by the locally increased resistance, the temperature in the material increases. Only by the self-heating, the very high melting temperatures can be achieved. In contrast, there are solutions that are mainly based on foreign warming. By using soft solders, significantly lower melting temperatures can be achieved. For example, the melting temperature of the main component tin is 232 ° C.

In addition, for example, DE102006040661A1 describes a starter in which the overload protection is realized in a two-part Y-shaped busbar by means of soft solder and a spring. The two parts of the busbar are connected by means of a soft solder. In case of overload, the soft solder melts at relatively low temperatures (e.g., 200 ° C), and a preloaded spring forces the two parts of the bus bar apart, thus breaking the circuit. Disadvantage of this solution is that, in particular in starters according to DE 10 2009 002 725 AI no such Y-shaped busbar is available or no space is available for this purpose. In addition, the installation location for the soft solder connection is relatively far away from the main heat source (contact surface brush / commutator), which makes it difficult to trigger at low currents and impairs the robustness of the function.

Disclosure of the invention

According to one aspect of the invention, provision is made for the copper strands or strands of the plus carbon brushes to be disconnected from a busbar in the event of overload.

This breaks a main circuit. Alternatively, the copper strands or strands of the negative carbon brushes can be separated from a brush plate. in the In normal operation, the strands are connected to a bus bar or brush plate using a soft solder. If the melting temperature of the soft salary is reached, the prestressed spring relaxes and the current path is interrupted. Compared to the prior art, this solution has the advantage that the point at which the soft solder is mounted as close as possible to the main heat source. This main heat source is the contact surface between the brushes and the commutator, the commutator surface. This ensures that the solder or soft solder is sufficiently heated even at low currents and can be melted after a sufficiently short time. In addition, this solution is applicable to all types of busbars or brush plates, so also at all points where brushes are mounted on an electrically conductive contact partner. The usual welding is simply replaced by a soft solder connection.

According to one aspect of the invention, it is provided that the spring element, which causes a tensile stress in the connecting material between the first conductor and the second conductor, is arranged in the current path. In particular, it is provided that the current path is formed between a first conductor and a busbar. In particular, it is provided that a solder is arranged between the spring element and the second conductor. This has the advantage, for example, that a surface which is relatively well defined by the surface condition is available for soldering, in particular soft soldering. The first conductor, the spring element and the second conductor are arranged in a stack. Preferably, the solder is also arranged in the stack between the spring element and the second conductor. If the spring element projects laterally out of the current path, then an anchoring point for one end of the spring element can be positioned relatively freely and in accordance with the space conditions. If the spring element is designed as a leaf spring, then the spring element is particularly easy to design. In addition, especially in a design as a leaf spring, the flat shape of the leaf spring easily adaptable to environmental conditions / space conditions. For example, the spring element may be rectangular, or designed as a free-form bow or designed U-shaped. If the spring element is designed as a flat spring, for example leaf spring, it is easy to set a release force by providing a set bending load, which is preferably designed as a simple beam bend. It is particularly preferred that a first conductor is a plus-side line. This allows a particularly reliable separation of rotating parts in the electric machine from the positive potential. According to further aspects of the invention can also be provided that, alternatively, a minus brush is secured to a brush plate accordingly. In this way, a main circuit of the electric machine would be interrupted. The functions described above can be implemented both with brush holders with four carbon brushes and with brush holders with six carbon brushes. That is, in particular, for example, in a total of four carbon brushes two plus carbon brushes or two Minuskohbürsten are each hedged by the securing device according to the invention. In the case of a total of six carbon brushes, protection of, for example, three carbon brushes on the plus side or three carbon brushes on the minus side would be indicated. According to a further variant, it is also possible to equip only one brush strand with the spring solder or spring soft solder system. In the event of a fault, therefore, initially only one current path will be separated via a single stranded wire. As a result, then the remaining plus or minus brushes or the remaining or the remaining plus or minus brush would be charged on average with a higher current. As a result, then a strand of a remaining brush could be made to melt and so in a kind of cascade finally the entire current path separated, so the starter are turned off. This has the advantage that less space and fewer components are required.

It is provided in particular that there is no current flow between the end of the spring element which is arranged in the current path and the end which is arranged or fastened in an insulator. The end in the insulator thus carries no current away from the junction with the first and second conductors.

Further advantages and expedient embodiments can be found in the further claims, the figures, the description and the drawings. Show it:

1 shows a starting device for an internal combustion engine with an electromagnetic starter relay for adjusting a starter pinion and for starting a starter motor, a first embodiment of a securing device, A second embodiment of a securing device.

In the figures, the same components are provided with the same reference numerals.

The electric machine shown in Fig. 1 is a starting device 1 for an internal combustion engine and has a starter pinion 2, which is brought to start the internal combustion engine 4 in engagement with a ring gear 3 of the internal combustion engine. The starter pinion 2 is mounted axially displaceably on a shaft 5 as indicated by the double arrow, wherein the starter pinion 2 is non-rotatably coupled to the shaft 5. The starter pinion 2 is moved between a retracted non-functional position and an advanced engagement position with the ring gear 3 of the internal combustion engine 4 via a starter relay 6, which is electromagnetically formed and a bestrombare relay winding 7 and an armature 8 35 includes the energizing the relay winding 7 in this axially is involved. The armature 8 is kinematically coupled via an engaging lever 9 with the starter pinion 2, so that the axial adjustment movement of the armature 8 between a rest position and an adjustment position in a corresponding axial adjusting movement of the starter pinion 2 between the non-functional position and the engaged position is used.

The rotating drive movement of the shaft 5 and the starter pinion 2 is generated by means of an electric starter motor 11 which is coupled via a planetary gear 12 with the shaft 5. Upon actuation of the electric starter motor 11, the shaft 5 and thus also the starter pinion 2 are rotated.

The starting device 1 is associated with a control or control device 10, via which the functions of the starter relay 6 and the starter motor 11 are controlled.

In an axial adjusting movement of the armature 8 upon actuation of the starter relay 6, the electric circuit of the starter motor 11 is closed upon reaching the adjustment position by the adjusting movement of the armature 8, so that the starter motor 11 is in motion and rotates the shaft 5 and the starter pinion 2 drives , The closing of the circuit of the starter motor 11 is effected by the fact that the ker 8 is a switching element, the carrier of an electrically conductive contact bridge, adjusted against two mating contacts 13, 14 in the circuit, so that the mating contacts 13, 14 are electrically connected to each other via the contact bridge.

In Figure 2, a portion of a brush apparatus 20 is shown in fragmentary form. Part of this brush apparatus 20 is, for example, a bus bar 23, which is formed here, for example, annular. At least one brush holder 26 is attached to this busbar 23. Typically, there are two so-called plus brushes and two so-called minus brushed brushes or three so-called plus brushes and three so-called minus brushed brushes. In a brush holder 26, a brush is used, which is not shown here. The brush is electrically and mechanically connected to a first conductor 29. This conductor 29 is particularly preferably designed as a stranded wire. The conductor 29 is indirectly attached to the bus bar 23 with a non-brush end 32. This attachment point 35 is shown in FIG.

The busbar 23 is electrically connected to a positive pole of a starter battery, which is not shown here. About this busbar 23, the brush, which is electrically connected via the conductor 29, connected to the electrical positive potential. For this purpose, the attachment point 35 is constructed as follows: The busbar 23 is connected in a material-locking manner via a connecting material 38, which is preferably formed as solder, in particular as soft solder, to a spring element 41. At this attachment point 35, in turn or beyond the spring element 41 is integrally connected to the one end 32 of the conductor 29. For this purpose, the end 32 is welded onto a surface 43 of the spring element 41.

As shown in FIG. 2, the spring element 41 preferably has an end on which or on which the conductor 29 is fastened or on which the attachment point 35 is arranged. At another end, which is designated by the reference numeral 45 in FIG. 2, the spring element 41 is anchored to the end 45 in an insulator 48.

This insulator 48 has a base plate 51, which rests on the busbar 23. This isolator 48 is firmly connected to the busbar 23 or the substrate by means of a snap connection or other form-fitting connection (not shown here). prevented. The base plate 51 has two lateral edge portions 53 and 54, which serve for the lateral bordering of the strip-shaped spring element 41. At one end of the base plate 51, which is farthest from the attachment point 35, there is a further edge portion 56. This edge portion 56 overlaps as well as the two edge portions 53 and 54, the sheet of the spring element 41. At the end 45 of the spring element 41 is further provided that two holes 58 in the spring element 41 engage in two pins 60. These pins 60 are formed integrally with the base plate 51.

For mounting the conductor 29 to the busbar 23, the following is provided: At the end 32 of the conductor 29, one end of the spring element 41 is integrally connected. The strip-shaped spring element 41 is initially free. The end 45 of the spring element 41 is initially pushed in the course of assembly along the length between the two edge portions 53 and 54 along. The two holes 58 in the spring element 41 are thereby pushed over the two mentioned pin 60 until they engage in the two holes 58. Finally, the edge portion 56 engages over the end 45 of the spring element 41st

After insertion of the end 45 of the spring element 41 in the base plate 51, the end of the spring element 41, which carries the end 32 of the conductor 29, by means of the bonding material 38 is firmly bonded to the busbar 23. It can be seen from FIG. 2 that, by fastening the end 45 of the spring element 41 on the busbar 23, the spring element 41 is slightly deflected. That is, the spring member 41 is bent by the amount delta h. This bend causes tension in the bonding material 38. As can be seen from FIG. 2, the spring element 41 is consequently located in a current path 63.

The electrical fuse device 65 shown in Figure 2 has a first conductor 29 and a second conductor, which is designed here as a busbar 23. The first conductor 29 and the second conductor are materially connected by the connecting material 38 electrically and mechanically. Accordingly, the current path 63 is formed between the first conductor 29 and the second conductor. In the connecting material 38 acts by a force acting through the spring element 41 force F is a tensile stress. The spring element 41 is arranged in the current path 63. As can also be seen from FIG. 2, the spring element 41 projects laterally out of the current path 63. As is apparent from the above explanations to the spring element 41, the spring element 41 is designed as a leaf spring. From the above it can also be seen that the spring element 41 is arranged with one end in the current path 63 and is anchored to the other end 45 in the insulator 48. As described above, in the spring member 41 between the two ends, a bending load. Furthermore, it is described that the first conductor 29 is a feed line, which is preferably designed as a stranded wire. This supply line is a supply line for a brush of an electric machine, which is preferably designed as a starting device for internal combustion engines. The first conductor 29 is preferably a positive-side line and accordingly arranged between, for example, a commutator and a connection part, which is contacted at a positive pole of a starter battery. It is provided that the second conductor 23 is a brush plate on which a brush holder 26 is mounted, in which a brush is arranged. Incidentally, a brush is stylized around the electric starter motor 11 in FIG.

The spring element 41 is mechanically and electrically connected to the first conductor 29, preferably by means of a welded connection. It is generally important that the junction between the conductor 29 and the spring element 41 is thermally higher loadable than the connection point between the spring element and the conductor 23rd

FIG. 3 shows a second exemplary embodiment of such a securing device 65. The differences from the embodiment of Figure 2 relate to the shape of the spring element 41 and the shape of the insulator 48. While the embodiment of Figure 2 shows a straight strip-shaped spring element 41, the spring element 41 according to the embodiment of Figure 3 is U-shaped. As can be clearly seen in comparison with Figure 2, the two embodiments have different extents in two axial directions. While the embodiment of Figure 2 is relatively long and narrow, on the other hand, the embodiment of Figure 3 is relatively short and a little wider. Depending on whether the space available for a safety device 65 is rather long and narrow or short and wide, the speaking embodiment of the safety device 65 can be selected. The U-shaped spring element 41 according to FIG. Gur 3 has at a first leg 70, the attachment point 35. A second leg 73 serves to at least partially absorb the already mentioned bending load in the spring element 41. For this purpose, the end 45 is inserted into the already mentioned insulator 48. This end 45 is inserted in an annular receptacle 76 of the insulator 48. As in the first embodiment, the spring element 41 is slightly bent, so that between the attachment point 35 and the receptacle 76, a deflection of the spring element 41 is set by a predetermined amount delta h. If a nearby electrical element is overloaded during operation of the electrical machine, then, due to the bias of the spring element 41, which thereby causes a tensile stress on the connecting material 38, in cooperation with the increased due to the overload temperature of the connecting material 38 is approaching set a melting temperature of the connecting material 38 (solder, soft solder) more or less quickly and thereby dissolve the association of spring element 41 and second conductor 23 and thereby address the safety device 65 as intended. Also in the second embodiment of Figure 3 is provided that the end 45 is held stationary in the insulator 48 after the response of the securing device 65. This is useful because after triggering the securing device 65 is to be prevented that the end 65 of the spring element 41 comes into contact with the second conductor 23. If the end 45 of the spring element 41 came into contact with the second conductor 23, the first conductor 29 would be under voltage at each contact, and accordingly the electrical machine would be operated again and again for a short moment.

Claims

claims

1. Electrical safety device (65), with a first conductor (29) and a second conductor (23), which are materially connected by a bonding material (38) electrically and mechanically, so that between the first conductor (29) and the second Conductor (23) is a current path (63), wherein in the connecting material (38) by a force acting by a spring element (41) force (F) acts a tensile stress, characterized in that the spring element (41) in the current path (63) is.

2. Electrical safety device according to claim 1, characterized in that the spring element (41) laterally protrudes from the current path (63).

3. Electrical safety device according to claim 1 or 2, characterized in that the spring element (41) is a leaf spring.

4. Electrical safety device according to one of the preceding claims, characterized in that the spring element (41) is arranged with one end in the current path and with another end (45) in an insulator (48) is anchored.

5. Electrical safety device according to claim 4, characterized in that in the spring element (41) between the two ends is a bending load.

6. Electrical safety device according to one of the preceding claims, characterized in that the first conductor (29) is a supply line, preferably a stranded wire, for a brush of an electric machine, preferably starting device for internal combustion engines.

7. Electrical safety device according to one of the preceding claims, characterized in that the first conductor (29) is a positive-side line.

8. Electrical safety device according to one of the preceding claims, characterized in that the second conductor (23) is a brush plate on which a brush holder is mounted, in which a brush is arranged.

9. Electrical safety device according to one of the preceding claims, characterized in that the spring element (41) with the first conductor (29) is connected by means of a welded connection.

10. Electrical safety device according to one of the preceding claims, characterized in that the spring element (41) is U-shaped.

11. Electrical safety device according to one of the preceding claims, characterized in that the current path (63) between a first conductor (29) and a busbar (23) is formed.

12. Electrical safety device according to one of the preceding claims, characterized in that between the end of the spring element (41), in which this in the current path (63) is arranged and the end (45) which in an insulator (48) arranged or is attached, there is no current flow.

13. Electrical safety device according to one of the preceding claims, characterized in that the first conductor (29), the spring element (41) and the second conductor (23) are arranged in a stack.

14. Electrical machine with an electrical safety device according to one of the preceding claims.