Abstract:
The invention relates to a hand-held machine tool, particularly to a drill hammer and/or chisel hammer, having a hand-held machine tool housing and a transmission chamber with at least one transmission element arranged inside the hand-held machine tool housing. According to the invention, the hand-held machine tool includes a pressure equalization unit, provided for equalizing pressure in the transmission housing and serving at least partially for supporting the transmission element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/061590 filed on Sep. 3, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a hand-held power tool. 
     2. Description of the Prior Art 
     A hand-held power tool embodied in the form of a rotary hammer and/or chisel hammer is already known, having a hand-held power tool housing and a transmission compartment that has at least one transmission element and is situated inside the hand-held power tool housing. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     The invention is based on a hand-held power tool, in particular a rotary hammer and/or chisel hammer, having a hand-held power tool housing and a transmission compartment that has at least one transmission element and is situated inside the hand-held power tool housing. 
     According to one proposal, the hand-held power tool has a pressure compensation unit that is provided to achieve a pressure compensation in the transmission compartment and serves to at least partially support the transmission element. In this context, “provided” should in particular be understood to mean especially equipped and/or designed. In addition, a “transmission compartment” should in particular be understood to be a closed unit that is embodied as closed off from a surrounding region with regard to a gas exchange or air exchange, with the exception of the pressure compensation unit; a “surrounding region” should be understood to be a motor compartment and/or an intermediate housing compartment and/or a compartment outside of the hand-held power tool housing. The transmission compartment is provided to accommodate a transmission unit. The embodiment according to the invention makes it possible to achieve an advantageous pressure compensation and to prevent an undesirable excess pressure in the transmission compartment; the excess pressure in this case can build up due to a heating of components of the transmission unit during an extended operation of the hand-held power tool. In addition, a particularly compact embodiment of the hand-held power tool can be achieved in that the pressure compensation unit performs a combination of at least two functions—pressure compensation and support. In addition, based on a pressure compensation of the pressure compensation unit, an undesirable escape and/or exchange of lubricant such as bearing grease, etc. can be advantageously prevented at bearing points of the transmission unit, thus at least reducing a premature wear on individual parts of the transmission unit and/or motor unit and enabling an operability of the hand-held power tool over a longer period of time. Another advantage of the pressure compensation unit is that decreasing the undesirable excess pressure achieves an advantageous temperature decrease, particularly inside the transmission compartment. This can be achieved in a particularly advantageous way if the pressure compensation unit has at least one pressure compensation opening by means of which an excess pressure can be reduced. 
     In this case, the pressure compensation opening preferably at least partially connects the transmission compartment to the motor compartment, thus permitting an excess pressure in the transmission compartment to be reduced in a particularly advantageous way by allowing air to escape from the transmission compartment into the motor compartment. 
     According to another proposal, the pressure compensation opening is at least partially comprised of a pressure compensation conduit through which an excess pressure in a subregion or more precisely stated, in the transmission compartment, can be selectively discharged. The pressure compensation conduit is advantageously composed of a bore, thus permitting an implementation of the pressure compensation opening in a particularly simply designed fashion. 
     According to another proposal, the pressure compensation opening is embodied as at least partially tapered; in addition to an advantageous pressure compensation, at least one functional element can be situated inside the pressure compensation opening in a simply designed fashion. Preferably, the tapered pressure compensation opening is embodied as stepped for this purpose. 
     In another proposed embodiment of the invention, the hand-held power tool has a pin, which is situated at least partially between the transmission compartment and the motor compartment and is equipped with the pressure compensation opening. By means of this, the pressure compensation opening can be advantageously integrated in a particularly space-saving fashion into an already existing component of the hand-held power tool, e.g. if the pin is constituted by a bearing pin for supporting a transmission element and/or by other components deemed suitable by the person skilled in the art. In addition, the pressure compensation unit can be advantageously preinstalled in the pin during a manufacturing process of the hand-held power tool, thus advantageously achieving a production of the hand-held power tool that reduces assembly complexity and/or costs. Preferably, the pin is constituted by a part whose surface advantageously has an at least slight contact with a lubricant or, in a particularly advantageous embodiment, is entirely lubricant-free, thus avoiding an undesirable exchange of lubricants, at least to a large extent. To this end, the pin can protrude in at least one direction into a central region of the transmission compartment and/or the motor compartment, thus keeping lubricant deposits away from the pressure compensation opening. 
     According to another proposal, the pressure compensation unit has at least one gas-permeable separating element, thus advantageously preventing an undesirable exchange and/or escape of lubricant and simultaneously permitting a pressure compensation. In this context, a “gas-permeable separating element” should in particular be understood to be an element that has a permeability for gas, in particular for a pressure compensation, and preferably for fluids and/or solid substances such as lubricants, has a separating property that advantageously prevents a permeability. 
     A particularly inexpensive and preferably weight-saving gas-permeable separating element can be advantageously achieved if the gas-permeable separating element is constituted by a felt element. A “felt element” should in particular be understood to be an element composed of a nonwoven made of wool and/or other textile fibers. 
     If the gas-permeable separating element is situated at least partially inside the pressure compensation opening, it is possible to achieve an especially space-saving, particularly compact arrangement of the gas-permeable separating element inside the pressure compensation unit. 
     According to another proposal, the pressure compensation unit has at least one fixing element that is provided to fix the gas-permeable separating element inside the pressure compensation opening, as a result of which the gas-permeable separating element can be advantageously prevented from undesirably falling out. 
     Preferably, the fixing element is constituted by a sleeve, thus permitting a simply designed fixing of the gas-permeable separating element inside a stepped pressure compensation opening. Embodying the fixing element in the form of a sleeve also assures an advantageous gas-permeability inside the pressure compensation opening. The sleeve can be constituted by a clamping sleeve, e.g. a shear stress pin, thus advantageously enabling further savings in terms of parts, space, assembly complexity, and costs for fastening the sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail below in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic depiction of a hand-held power tool according to the invention, embodied in the form of a rotary hammer and equipped with a pressure compensation unit; and 
         FIG. 2  is an enlarged schematic detail of the hand-held power tool equipped with the pressure compensation unit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1 and 2  schematically depict a hand-held power tool  10  embodied in the form of a rotary hammer. The hand-held power tool  10  has a hand-held power tool housing  12 , a transmission compartment  14  situated inside the hand-held power tool housing  12 , and a motor compartment  16  situated inside the hand-held power tool housing  12 . The motor compartment  16  has a motor unit  34 , which includes an electric motor  36  and a fan  38 , and the transmission compartment  14  has a transmission unit  40  equipped with an impact mechanism  42 . In addition, the motor compartment  16  and the transmission compartment  14  are embodied as units that are separate from each other and are closed off from each other, preventing a gas exchange and a pressure compensation. For this purpose, the hand-held power tool  10  or more precisely stated, the hand-held power tool housing  12 , has a bearing housing  44  for a separation of the transmission compartment  14  from the motor compartment  16 ; the bearing housing  44  is provided to support a motor shaft  46  of the motor unit  34  and to support transmission elements of the transmission unit  40  such as a ring gear  48  and an eccentric gear  50  of an eccentric unit  52 . Instead of a bearing housing  44 , it is essentially also conceivable in another embodiment to use a bearing flange and/or other components deemed suitable by a person skilled in the art to separate the transmission compartment  14  from the motor compartment  16 . For a pressure compensation in the transmission compartment  14 , the hand-held power tool  10  has a pressure compensation unit  18 . 
     The bearing housing  44  has a pin  24  embodied in the form of a bearing pin that is press-fitted into the bearing housing  44 . The pin  24  protrudes along the drive axis  58  of the motor unit  34  from the motor compartment  16  in the direction  66  toward the transmission compartment  14  and into the transmission compartment  14 . A transmission element  80  comprised of the eccentric gear  50  of the transmission unit  40  is rotatably supported on the pin  24  and during operation, transmits the drive moment to the impact mechanism  42  in order to generate a hammering impulse for a tool that is not shown in detail. To this end, a main extension direction  54  of the pin  24  is oriented essentially parallel to a rotation axis  56  of the eccentric gear  50  and to the drive axis  58  of the motor shaft  46 . In order to assure the lowest possible friction in the rotary motion of the eccentric gear  50  in relation to the pin  24 , two needle bearings  60 ,  62  are situated between the eccentric gear  50  and the pin  24 . 
     The pressure compensation unit  18  is situated in the pin  24  so that the pressure compensation unit is provided to support the transmission element  80 . To this end, the pin  24  has a bore extending along its main extension direction  54 , which is composed of a pressure compensation opening  20  embodied in the form of a pressure compensation conduit  22 . The pressure compensation conduit  22  connects the transmission compartment  14  to the motor compartment  16  so that during operation of the hand-held held power tool  10 , an excess pressure in the transmission compartment  14  can be discharged into the motor compartment  16  by means of the pressure compensation conduit  22 . In addition, along the main extension direction  54  in the end regions  64  of the pressure compensation conduit  22  and pin  24 , the pressure compensation conduit  22  has a wall with a 60° slope in relation to the main extension direction  54 . The 60° slope simplifies a grinding process of the pressure compensation conduit  22  during a manufacture of the pin  24  together with the pressure compensation unit  18 . 
     The pressure compensation conduit  22  is embodied as tapered, with a tapering extending along the main extension direction  54  from the motor compartment  16  in the direction  66  toward the transmission compartment  14 . The tapering of the pressure compensation conduit  22  is embodied as stepped. 
     The pressure compensation unit  18  also has a gas-permeable separating element  26  and a fixing element  30  embodied in the form of a sleeve  32 . The gas-permeable separating element  26  is composed of a cylindrical felt element  28 ; the cylindrical felt element  28  has a transverse span that is oriented essentially transverse to the main extension direction  54  of the pin  24  and corresponds/is equal to a transverse span or inner diameter of a stage  70  of the tapered pressure compensation conduit  22  situated in the middle in the main extension direction  54  of the pin  24 . By means of this, a step-shaped shoulder  72  of the pressure compensation conduit  22  holds the cylindrical felt element  28  in position along the main extension direction  54  from the motor compartment  16  in a direction  66  toward the transmission compartment  14 . A longitudinal span of the cylindrical felt element  28  oriented in the main extension direction  54  of the pin  24  corresponds to a longitudinal span of the middle stage  70 . 
     In order to fix the cylindrical felt element  28  along the main extension direction  54  of the pin  24  from the transmission compartment  14  in a direction  74  toward the motor compartment  16 , the sleeve  32 , which is embodied in the form of a clamping sleeve such as a sheer stress pin, is situated inside the pressure compensation conduit  22  and clamped to the pin  24 ; the sleeve  32  is situated in the direction  74  toward the motor compartment  16  after the cylindrical felt element  28 , in the region of a step  78  of the pressure compensation conduit  22  oriented toward the motor compartment. In addition, it is embodied with a material thickness that is thicker than a step height so that the cylindrical felt element  28  is secured in a way that prevents it from undesirably falling out in the direction  66  toward the motor compartment  16  and is securely fixed in the pressure compensation conduit  22 . 
     During operation of the hand-held power tool  10 , a rotation movement of transmission components and a production of a hammering impulse of the transmission unit  40  inside the transmission compartment  14  can lead to a heating of individual components of the transmission unit  40 . This heating results in a heating of air inside the transmission compartment  14  and to an undesirable pressure increase or more precisely stated, an undesirable excess pressure. By means of the pressure compensation unit  18 , it is possible to discharge the excess pressure from the transmission compartment  14  into the motor compartment  16  in the process of which warm air flows from the transmission compartment  14  through the pressure compensation opening  20  into the motor compartment  16 . 
     Also during a pressure compensation by means of the pressure compensation opening  20  of the pressure compensation unit  18 , an exchange or escape of lubricants through the pressure compensation conduit  22  is prevented by means of the cylindrical felt element  28 . A rotation of the eccentric gear  50 , which rotates around the pin  24  and therefore around the pressure compensation unit  18 , produces a centrifugal force during operation of the hand-held power tool  10  that acts on lubricant possibly emerging in the vicinity of the eccentric gear  50  and removes the lubricant from the pressure compensation conduit  22 , thus preventing to the greatest possible extent a lubricant exchange via the pressure compensation conduit  22 . In addition, an arrangement of the pin  24  protruding far into the transmission compartment  14  impedes a contact of the pressure compensation conduit  22  with the lubricant and protects the pressure compensation conduit  22  from a possible entry of lubricants. 
     The foregoing relates to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.