Abstract:
A valve seat and valve guide machining tool for the precision machining of valve seats and valve guides in a cylinder head of an internal combustion engine is disclosed, comprising at least two tool parts ( 3,5 ) of which a first comprises at least one geometrically defined cutter ( 11 ), provided for the valve seat machining and a second comprises at least one geometrically-defined cutter ( 15 ), provided for valve guide machining, which are connected to each other by means of a precision interface ( 17 ). The precision interface ( 17 ) is a squat conical connection, comprising a first plane surface ( 19 ) on the first tool part ( 3 ) and second plane surface ( 21 ) on the second tool part ( 5 ), arranged perpendicular to a mid-axis ( 23 ) of the tool ( 1 ) and, in the assembled state of the tool ( 1 ), lie adjacent to each other, said first tool part ( 3 ) being made from steel. The tool is characterised in that the second tool part ( 5 ) is divided into two sections ( 39,41 ) of which a first section ( 39 ) is made from a hard metal and is provided with the precision interface ( 17 ) and a second section ( 41 ) is made from a material which is more elastic than the material of the first tool part ( 3 ), and comprises the at least one cutter ( 13 ) of the second tool part ( 5 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 371 US National Stage of International Application No. PCT/EP2006/005886, filed Jun. 20, 2006. This application claims the benefit of German Application DE 10 2005028 368.3, filed Jun. 20, 2005. The disclosure of the above application is incorporated herein by reference. 
   DESCRIPTION 
   The invention relates to a valve seat and valve guide machining tool for fine machining of valve seat and valve guide in a cylinder head of a combustion engine in accordance with the preamble of claim  1 . 
   Tools of the kind addressed here are known (DE 101 37 000 A1). It has emerged that when machining a valve seat and valve guide in the cylinder head of a combustion engine surface quality in the area of the valve guide on the one hand and the coaxiality between valve and valve guide on the other hand are of great importance. Coaxiality is an important criterion for the tightness and for the use of the combustion engine. The quality of the surface area of the valve guide is essential for low-wear operation of the combustion engine. In a known tool, two tool parts are provided, of which a first is assigned to valve seat machining and a second to valve guide machining. The two tool parts are connected to each other through a precision interface, wherein one tool part has a truncated cone and the other a conical seat for the truncated cone. Both tool parts have flat surfaces in the area of the precision interface which are located perpendicular to the center axis of the tool. The precise coaxial alignment of the two tool parts to each other is ensured by the precision interface. It effects a clear increase in the stiffness of the tool so that bending in the area of the second part of the tool is reduced. The surface qualities of valve seat and valve guide are increased still further because vibrations occurring in the fine machining of the areas mentioned inside the tool are suppressed by the precision interface and thus strongly dampened. By selecting different materials for the two tool parts, vibration is reduced still further. Steel is used for the first tool part for valve seat machining and carbide for the second tool part for valve guide machining. It has been shown that in some cases surface quality in the area of the valve guide is not adequate and relative high wear results on the second tool part. 
   The object of the invention is therefore to create a valve seat and valve guide machining tool for fine machining of valve seat and valve guide in a cylinder head of a combustion engine which does not suffer from this disadvantage. 
   To achieve this object, a valve seat and valve guide machining tool is proposed which has the features named in claim  1 . The tool comprises in turn two tool parts, one of which is assigned to machining the valve seat and a second tool is assigned to machining the valve guide. The first tool for machining the valve seat is made in turn from steel. The tool however is distinguished by the fact that the second part of the tool is divided and has two sections of which only one is of carbide, namely the first section which is allocated to the precision interface. The second section of the second tool part consists of a material which is more ductile than that of the first section. It is therefore possible that the second section of the second tool part conforms optimally to the surface of the valve guide because of its ductility, preventing rapid wear of the second tool part and substantially improving the surface quality of the valve guide. 
   An embodiment of the tool is preferred whose characteristics are that the second section consists of steel or heavy metal. These materials are characterized by greater ductility than carbide so that the second tool part in the area of the second section can conform better to the surface of the valve guide. The resulting additional advantage is that the material of the second section is easier to machine than that of the first section. 
   Additional embodiments become clear from the remaining dependent claims. 

   
     The invention is explained in more detail from the drawing. 
       FIG. 1  shows a principal view of a valve seat and valve guide machining tool in a side view as an exploded drawing; 
       FIG. 2  shows a side view of part of the tool shown in  FIG. 1  and 
       FIG. 3  shows an enlarged end view of the tool part from  FIG. 2 . 
   

     FIG. 1  shows a valve seat and valve guide machining tool designated in what follows as tool  1  which has two tool parts, namely a first tool part  3  used for valve seat machining and a second tool part  5  used for valve guide machining. The first tool part  3  here has a shaft  7  which is used to connect tool  1  to a machine tool. It is configured correspondingly and, as an example, provided here with a conical outer surface. It further comprises a cutter plate  9  with a blade  11  which is used for machining a valve seat. 
   The second tool part  5  also has a cutter plate  13  which comprises a geometrically determined blade  15 . 
   The two tool parts  3  and  5  are connected by a precision interface  17  which is configured as a truncated cone connection and a first flat surface  19  on the first tool part  3  and a second flat surface  21  on the second tool part  5 . The flat surfaces are located perpendicular to the rotational and center axis  23  of the tool  1 . The precision interface  17  comprises a cone on the one hand and on the other a recess to receive the cone. The intention here is that the cone  25  is provided on the second tool part  5  and the conically configured recess  27  on the first tool part  3 . 
   A clamping screw is shown in the exploded drawing which is provided with a first threaded section which engages the first tool part  3 , in addition with a second threaded section  33  which engages the tool part  5 . The threaded sections  31 ,  33  comprise opposite threads. If the clamping screw is turned in a first direction, the two parts of the tool  3  and  5  are clamped together in the area of the precision interface  17 , where the cone  25  is pulled into the recess  27  and the flat surfaces  19  and  21 , which are configured here as annular surfaces, abut solidly against each other. 
   With a turn of the clamping screw  29  in the opposite direction, the two parts of the tool  3  and  5  are pushed apart so that the clamping forces between cone  25  and recess  27  are loosened. 
   When fine machining the valve seat and valve guide in the cylinder block of a combustion engine, the two tool parts  3  and  5  are clamped together by the precision interface  17 , which results in a high degree of rigidity for the tool  1 , and in addition absolutely precise locational positioning of the tool parts  3  and  5  to each other. 
   The second tool part  5  is configured as a reamer which is used to machine the valve guide. The first tool part  3  is used to machine the valve seat. For this reason the blade  11  of the cutting plate  9  of the first tool part inclined at an angle to the center axis. Incidentally, it slopes in the advance direction of the tool indicated by an arrow  35 . 
   In the area of the second tool part  5  at least one guide strip is provided by way of which the second tool part  5  supports itself against the surface of a valve seat guide while it is being machined by the blade  15  of the cutter plate  3 . 
   It should be pointed out that the blades  11  and  15  of the cutter plates  9  and  13  can also be provided directly on the base body of the tool parts  3  and  5 . In order to ensure adjustability of the blades, they are preferably part of a cutter plate, as shown here, which coacts with a suitable adjusting mechanism. 
   In  FIG. 1  it is indicated that the second tool part  5  has a first section  39  and a second section  41  which are configured as separate elements and joined. Here only a dividing line  43  can be seen which reveals the contact area between the two sections  39  and  41 . 
   The principal view from  FIG. 1  shows that the first tool part  3  has a larger outside diameter than the second tool part  5 . This is because of a cylindrical area with a small diameter in a conical area  45  on which the second flat surface  21  is provided. In the area of the flat surface  21  the outer diameter of the second tool part  5  is considerably larger than, for example, in the area of the dividing line  43 . The length of the cylindrical area to the right and left of this dividing line  43  is selected as a function of the length of the guide of the valve guide. 
   From  FIG. 2  the second tool part  5  of the tool  1  can be seen in a side view. It is reproduced in partial section. Identical parts are given identical reference numerals so that in this regard reference is made to the description for  FIG. 1 . 
   The tool part  2  is shown enlarged so that details are more recognizable than in  FIG. 1 . It is clearly recognizable here that the second tool part  5  has two sections  39  and  41  which are connected in a suitable way, here soldered together. 
   Here it is clearly recognizable that the second section  41  and the area of the first section  39  bordering the dividing line  43  have a cylindrical outer surface and the cylindrical outer surface of the first section  39  transitions over a conical area  45  into the flat surface of the precision interface  17  running perpendicular to the center axis. 
   From the partial section in  FIG. 2  it is clearly recognizable that the second tool part  5  is made up of the two sections  39  and  41 . They are not butted against each other in the area of the dividing line  43 . Instead, one of the sections has a projection and the other has a matching recess which the projection engages. Here the intention is that the first section  39  has a conical or truncated conical projection  47  in the connecting area indicated by the dividing line  43  which engages a correspondingly conical or truncated conical recess  49  in the second section  41 . The projection  47  is preferably soldered into the recess  49 . 
   The second tool part  5  has a coolant/lubricant passage  51  running concentrically here to the center axis  23  through which a coolant/lubricant is supplied to the blade  15  of the cutter plate  13 . The coolant/lubricant passage  51  runs through the first section  39  and empties in a distributor chamber  53  which connects here to the recess  49  in the second section  41 . A passage runs from here which rises opposite the center axis  23  from the distributor chamber  53  in the direction of the advance mechanism indicated by the arrow  35  and brings coolant/lubricant into the area of the blade  15 . 
   The cutter plate  13  is held by a chucking jaw  57  which is retained by a screw in the main body of the second section  41 . Normally tightening bolts are used which are known and therefore not shown here. 
   The second part of the tool  5  has at least one guide bead  59 . The intention here is that each of the two sections  39  and  41  has its own guide bead. The first guide bead  59  in the area of the second section  41  continues on the other side of the dividing line  43  in the guide bead  59 ′ of the first section  39 . The intention here is that the first guide bead  59  is narrower than the guide bead  59 ′.  FIG. 2  reveals that the first guide bead  59  continues to the right beyond the chucking jaw  57  after an interruption and thus comprises a guide bead element  59 ″. 
   A centering element  63  which comprises a centering hole  65  is mounted on the face  61  of the second part of the tool  5 . It is used for machining the tool  1  or the second tool part  5  when manufacturing the tool and as part of repairs. Center bores of the type discussed here are known so that there is no need to pursue them further. 
   The first guide bead  59  of the second section  41  and the corresponding guide bead  59 ′ in the area of the first section  39  as well as the guide bead element  59 ″ which forms the extension of the first guide bead  59 , extend parallel to the center axis of  23  of the tool  1  and thus lie along one line. 
     FIG. 3  shows the second tool part in an end view, that is a view of the face  61 . Identical parts are given identical reference numerals so that reference is made to the description of the preceding figures. For reasons of greater clarity, the centering element  63  is omitted. 
     FIG. 3  shows clearly that the second section  41  of the second part of the tool  5  has a base body  66  into which the cutter plate  13  with the blade  15  is inserted. Similarly the first guide bead, of which the guide bead element  59 ″ is recognizable, is set into the circumferential surface  67  of the second part of the tool  5 . The guide bead element  59 ″ follows the blade  15  by 270° in the direction of rotation of the tool indicated by an arrow  69 . An additional guide bead element  71  follows the blade by approx. 45°. Finally, a third guide bead  73  is provided which lies diametrically opposite the blade  15 . 
   The chucking jaw  57  is indicated by lines in  FIG. 3  which is clamped by a locking screw  75  to the base body of the second part of the tool  5 . Finally,  FIG. 3  shows an adjusting device  77  with the aid of which the extension of the blade  15  can be adjusted, that is the radial extension of the blade  15 . The adjusting device  77  has an adjusting screw  79  which coacts with the underside of the cutter plate  13  lying opposite the blade  15 , not directly but by way of an adjusting wedge  83 . 
   Adjusting devices  77  of the type addressed here are fundamentally known so that no further discussion is necessary. 
   In the case of the tool  11 , provision is made that the first part of the tool  3  is made of steel. It was already indicated above that the second part of the tool consists of carbide in known tools. Here provision is made that only the first section  39  of the second part of the tool  5  is made of carbide and that the second part  41  consists of steel or heavy metal. It is crucial that the second section  41  of the second part of the tool  5  consist of a metal that is more ductile than the material of the first section  39 . 
   Different materials are used within the second part of the tool  5 , where the material of the second section  41  is more ductile than that of the first section  39 . The tool  1  is further characterized in that it is more easily machined. It is possible to realize a groove to receive the cutter plate  13  in the second section  41  in a relatively inexpensive manner, furthermore a recess in which the clamping jaw  57  comes to rest. Finally, the clamping screw  75  and the adjusting device  77  can be installed relatively easily into the base body  66  of the second section  41  with the appropriate threads. 
   The characteristics of second part of the tool  5  are that the second section  41  is so ductile that it can lie flush on the surface of the valve guide. In this way, the at least one guide bead of the second guide section lies optimally against the valve guide surface while the latter is undergoing metal-removing fine machining by means of the blade  15 . The optimal position of the second section  41  against the valve guide surface results in improved surface quality, and in addition reduced wear on the blade  15 . Beyond that, it is easier to machine the material of the second section  41  which consists of steel or heavy metal and not of carbide in order to insert the cutter plate  13 , the clamping jaw  57 , the adjusting device and the guide beads into the base body of the second section  41 . 
   Provision is preferably made that at least one guide bead, here the guide bead  73 , lies diametrically opposite the blade  15 . Finally, a third guide bead is provided in the circumferential surface  67  of the second section  41 . Advantageously the guide bead  71  is also provided, following the blade  15  by approx. 45° in order to ensure optimal guidance of the tool in the valve guide which is to be machined. Finally, an especially good guidance results from a third guide bead being provided in the circumferential surface  67  of the second section  41 .