Patent Publication Number: US-2004056540-A1

Title: Device with a suppressor for reducing interference

Description:
BACKGROUND OF THE INVENTION  
       [0001] The invention relates to a device with a suppressor for reducing interference according to the preamble of claim 1.  
       [0002] In order to reduce interference in the high-frequency range in electric motors, it is known to electrically connect two suppressors in a supply lead of the electric motor between a pole shoe and a commutator of the electric motor. The suppressors are secured separately from each other in cartridges in a motor housing and comprise connection cables having different lengths. Each of the suppressors has a coil and a core.  
       ADVANTAGES OF THE INVENTION  
       [0003] The invention relates to a device having at least one suppressor for reducing interference, especially in the high-frequency range of an electrical machine, and also comprising at least one connection element for connection to a pole shoe of the electric machine.  
       [0004] The invention provides that the suppressor is secured in a receiving area of the connection element which is provided with a plug-in element for connection to the pole shoe, and is combined therewith to form a module. Cables and fastening components can be spared, and a compact module that can be integrated in space-saving fashion is attained, which said module can be integrated particularly advantageously in hand power tools, and particularly in hand power tools that comprise an electric motor with a turnable brush plate which typically takes up more space than a fixed brush plate. The module can be situated advantageously close to a commutator of the electric machine and, therefore, to the source of interference, and a high level of efficiency of the suppressor can be attained.  
       [0005] With the module, simple and fast installation and removal can be attained, of other components and assemblies as well in particular, such as carbon brushes of the electrical machine, and a high level of electrical safety can be attained using a simple construction by the fact that current-carrying lines can be situated relatively far away from an outer housing, providing advantageous external protection.  
       [0006] Installation expenditure and the amount of space required can be further reduced by integrating a plug-in element in the connection element for connection to an armature and/or by integrating a plug-in element in the module for connection to a control switch. The plug-in element for connection to the armature of the electric machine can be mounted or, advantageously, integrally molded on the connection element, by way of which assembly expenditure can be avoided.  
       [0007] The plug-in elements can be formed out of various elements appearing reasonable to one skilled in the art, such as blade terminals or receptacles.  
       [0008] If the device comprises two constructionally identical modules, incorrect fitting resulting from the modules being mixed up can be advantageously prevented, and the number of different components and, therefore, the total cost, can be reduced.  
       [0009] The invention further provides that two modules are combined on a carrier unit to form one insertable unit, which allows them to be advantageously secured in a housing in one installation step and with few fastening elements.  
       [0010] The module or modules can be secured on a carrier unit formed by an additional component or, advantageously, on a component belonging to the electric machine, e.g., on a brush plate of the electric machine. The need for additional components can be prevented in this manner.  
       [0011] According to a further embodiment, the invention provides that at least part of the module is encapsulated in plastic. Encapsulation can provide advantageous protection against vibrations in particular. With encapsulation, it can furthermore be easily ensured that the components are correctly matched up with each other inside the module using few fastening elements. The module can be partially inserted into the connection plate and then encapsulated or, advantageously, it can be encapsulated at least partially by the connection plate. Assembly expenditure can be reduced in this manner.  
       [0012] The device can be used in various electric machines appearing reasonable to one skilled in the art, e.g., in alternators operated in the high-frequency range, for example. Due to the attainable compact construction, however, they can be used particularly advantageously in hand power tools. 
     
    
    
     SUMMARY OF THE DRAWINGS  
     [0013] Further advantages result from the following description of the drawings. An exemplary embodiment of the invention is presented in the drawings. The drawings, the description, and the claims contain numerous features in combination. One skilled in the art will advantageously consider them individually as well and combine them into reasonable further combinations.  
     [0014]FIG. 1 is a side view of a schematic representation of an impact drill,  
     [0015]FIG. 2 is a module with a suppressor and a connection element,  
     [0016]FIG. 3 is the module in FIG. 2, mounted on a connection plate of an electric motor,  
     [0017]FIG. 4 is an alternative to the module shown in FIG. 2, comprising an integrated plug-in element for connection to a control switch, and  
     [0018]FIG. 5 is the module shown in FIG. 4, mounted on a connection plate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0019]FIG. 1 is a side view of an impact drill shown in a schematic representation, comprising an electric motor  18  located in a housing  78 , which said electric motor is equipped with a not-shown turnable brush plate. The impact drill comprises a device having two suppressors  10 ,  12  for reducing interference in the high-frequency range, each having a connection element  14 ,  16  for connection to a pole shoe of an electric motor  18  (FIGS. 1, 2, and  3 ).  
     [0020] According to the invention, the suppressor  10 ,  12  is secured in a receiving area  20 ,  22  of the connection element  14 ,  16  which is provided with a plug-in element  24 ,  26  for connection to the pole shoe, and is combined therewith to form a module. The modules  28 ,  30  are constructionally identical. The design of the modules  28 ,  30  will be described hereinbelow using module  28  as an example (FIG. 2).  
     [0021] The suppressor  10 , which is formed by a coil  54  and an iron core  56  enclosed by the coil  54 , is inserted in the receiving area  20  of the connection element  14  when the module  28  is installed. The receiving area  20  is formed by two holding arms  62 ,  64  integrally molded on the connection element  14 . The free ends of said holding arms point in the direction of insertion  66  of the module  28  into a connection plate  48  of the electric motor  18  (refer to FIGS. 2 and 3). The suppressor  10  is guided via ends  58 ,  60  of the coil  54  into notches  68 ,  70  formed in the free ends of the holding arms  62 ,  64 . The holding arms  62 ,  64  are then crimped and soldered in the region of the notches  68 ,  70  to fix the suppressor  10  in position in the connection element  14  and to electrically connect said suppressor with said connection element.  
     [0022] Once the suppressor  10  is fixed in position in the receiving area  20  of the connection element  14  and combined with the connection element  14  to form a module  28 , they are inserted into a housing  72  shown in FIG. 2, which said housing is then covered with plastic  52 . The module  28  and/or the suppressor  10  and the connection element  14  are thereby advantageously protected from vibrations.  
     [0023] The module  28  and the constructionally identical module  30  are inserted via their plug-in elements  24 ,  26 —formed as blade terminals—into the insertion sleeves  74 ,  76  integrally molded on the connection plate  48  of the electric motor  18  (FIG. 3). To enhance clarity, modules  28 ,  30  are shown in FIG. 3 without housing  72  or plastic encapsulation. Together with the connection plate  48 , which is part of the stator, the two modules  28 ,  30  form a unit  44  which can then be pressed into the housing  78  of the impact drill in one installation step.  
     [0024] A plug-in element  36 ,  38  developed as insertion sleeve is integrally molded on each side of the connection element  14 ,  16  furthest from the plug-in element  24 ,  26 , into which said plug-in element developed as insertion sleeve a not-shown plug-in element developed as blade terminal of the armature of the electric motor  18  can be inserted. In FIG. 2, current flow  80  from the armature through the module  28  to the pole shoe is shown schematically. Current flows from the plug-in element  36  through the holding arm  64  to the end  60  of the coil  54 , through the coil  54  to the holding arm  62  and through the holding arm  62 —one leg  82  of which extends parallel to the iron core  56  of the suppressor  10 —to the plug-in element  24 . If the direction of current flow changes, the current then flows in the opposite direction through the module  28 .  
     [0025] An alternative device is shown in FIGS. 4 and 5. Components that are essentially identical are labelled with the same reference numerals. Furthermore, reference is made to the description of the exemplary embodiment in FIGS. 1 through 3 with regard for features and functions that remain the same. The following description is essentially limited to the differences from the exemplary embodiment in FIGS. 1 through 3.  
     [0026] The device comprises two constructionally identical modules  32 ,  34  plugged into a connection plate  50  of an electric motor. Said modules, together with the connection plate  50 , form a unit  46  capable of being inserted in a housing. Each of the modules  32 ,  34  comprises an integrated plug-in element  40 ,  42  designed as a 90-degree connector for connection to a control switch. The plug-in element  40  is placed in a housing  72  enclosing the module  32 , and it is encapsulated as well when the module  32  and/or a suppressor  10  and a connection element  14  are encapsulated in plastic  52  (FIG. 4). The plug-in element  40  is electrically insulated from the suppressor  10  and the connection element  14  via the plastic  52 .  
     REFERENCE NUMERALS  
     [0027]                                      10   Suppressor       12   Suppressor       14   Connection element       16   Connection element       18   Electric motor       20   Receiving area       22   Receiving area       24   Plug-in element       26   Plug-in element       28   Module       30   Module       32   Module       34   Module       36   Plug-in element       38   Plug-in element       40   Plug-in element       42   Plug-in element       44   Unit       46   Unit       48   Connection plate       50   Connection plate       52   Plastic       54   Coil       56   Iron core       58   End       60   End       62   Holding arm       64   Holding arm       66   Direction of insertion       68   Notch       70   Notch       72   Housing       74   Insertion sleeve       76   Insertion sleeve       78   Housing       80   Current flow       82   Leg