Abstract:
Described is a crankcase and a method for assembling a multi-part crankcase. The method can include providing a cylinder block and a bearing tunnel upper part. The cylinder block has a plurality of threaded holes into each of which a stud screw is screwed, where the stud screws protrude from the cylinder block. The bearing tunnel upper part has a plurality of through-holes, where each of the through-holes is arranged coaxially to a corresponding stud screw. On a side facing the cylinder head, each of the through-holes has an internal thread having a first direction of rotation. A plurality of threaded sleeves, each threaded sleeve has an internal thread that has a second direction of rotation, an external thread that has a first direction of rotation, and a driver profile for inserting a screwdriver tool in a positive-locking manner, are provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. DE 10 2013 114 318.0 filed Dec. 18, 2013, which is hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present application lies in the field of engine construction and relates in particular to a multi-part crankcase that can be screwed together, for example for a V engine. 
       BACKGROUND 
       [0003]    It is known in the field of reciprocating internal combustion engines to assemble the crankcase from a plurality of components. Multi-part crankcases are used, for example, if for strength reasons or weight reduction reasons, individual parts are produced from a different material (e.g. aluminum) than other parts. For example, the publication EP 1 843 029 A2 (Title: “Composite cylinder case”) describes a crankcase, wherein a cylinder block is screwed together with a cast iron part that is designated as “Kurbelraumeinheit” (“crank chamber unit”). A reinforcement element which forms the bearing tunnel upper part for the crankshaft is cast in the cast iron part. A bearing cap that is screwed to the reinforcement element forms the bearing tunnel lower part. 
         [0004]    Crankcases composed of a plurality of components which have to be screwed together can result in an increased assembly effort in production. It is therefore an object of the application to provide a multi-part crankcase that requires comparatively little assembly effort. 
       SUMMARY 
       [0005]    The aforementioned object is achieved by a method and a crankcase according to the claims. Exemplary configurations and refinements thereof are the subject matter of the dependent claims. 
         [0006]    A method for assembling a multi-part crankcase is disclosed below. According to one embodiment, the method comprises providing a cylinder block and a bearing tunnel upper part. The cylinder block has a plurality of threaded holes into each of which a stud screw is screwed, wherein the stud screws protrude from the cylinder block. The bearing tunnel upper part has a plurality of through-holes, wherein each of the through-holes is arranged coaxially to a corresponding stud screw. On a side facing the cylinder block, each of the through-holes has an internal thread having a first direction of rotation. Furthermore, a plurality of threaded sleeves are provided. Each threaded sleeve has an internal thread having a second direction of rotation, an external thread having a first direction of rotation, and a driver profile for inserting a screwdriver tool in a positive-locking manner. The bearing tunnel upper part, the cylinder block and the threaded sleeves are positioned relative to one another in such a manner that the threaded sleeves are arranged between and coaxially to the stud screws and the through-holes. A screwdriver tool is inserted through one of the through-holes into at least one driver profile of one of the threaded sleeves. By rotating the threaded sleeve, the threaded sleeve is screwed into the internal thread of the through-hole and, at the same time, is screwed onto the stud screw. 
         [0007]    Furthermore, a crankcase is described which is particularly suitable for a V engine. According to a further example, the crankcase comprises at least one cylinder block having a plurality of threaded holes into each of which a stud screw is screwed, wherein the stud screws protrude from the cylinder block. The crankcase further comprises a bearing tunnel upper part having at least two bearing blocks arranged along a longitudinal axis and having a plurality of through-holes. Each of the through-holes is arranged coaxially to a corresponding stud screw and, on a side facing the cylinder head, each of the through-holes has an internal thread having a first direction of rotation. Furthermore, a plurality of threaded sleeves are provided, each with an external thread that has the first direction of rotation, with an internal thread that has the second direction of rotation and with a driver profile for inserting a screwdriver tool in a positive-locking manner. The external thread of each threaded sleeve is screwed into the internal thread of the corresponding through-hole, and the internal thread of each threaded sleeve is screwed onto a corresponding stud screw. 
         [0008]    A further cylinder block can be screwed together with the bearing tunnel upper part, in the same manner as the first cylinder block. According to the example described here, a bearing tunnel lower part is screwed together with the bearing tunnel upper part in such a manner that the bearing blocks arranged in the bearing tunnel upper part and the bearing caps arranged in the bearing tunnel lower part form corresponding bearing points for the crankshaft. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]    The disclosed embodiments are explained in more detail below by means of the examples illustrated in the figures. The illustrations are not necessarily true to scale and the application is not limited only to the illustrated aspects. Rather, emphasis is placed on illustrating the principles underlying the application. In the figures: 
           [0010]      FIG. 1  shows an example of a crankcase in an isometric illustration with two cylinder blocks and a bearing tunnel upper part during assembly (the bearing tunnel lower part is not illustrated); 
           [0011]      FIG. 2  shows the example from  FIG. 1  in a view from below; 
           [0012]      FIG. 3  shows the example from  FIG. 1  in a cross-sectional illustration, with the cylinder block not completely assembled yet; 
           [0013]      FIG. 4  shows a view of the crankcase corresponding to the cross-sectional illustration from  FIG. 3 , with the cylinder block assembled; 
           [0014]      FIG. 5  shows the crankcase from  FIG. 1  after assembly, including a bearing tunnel lower part in an isometric illustration; 
           [0015]      FIG. 6  shows the crankcase from  FIG. 5  in a view from the right; 
           [0016]      FIG. 7  shows the example from  FIG. 5  in a cross-sectional illustration in which the screw connection of the bearing tunnel and the cylinder blocks is shown; and 
           [0017]      FIG. 8  shows a detail from  FIG. 3  in an enlarged scale. 
           [0018]    In the figures, the same reference numerals designate the same or similar components each with the same or similar function. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  is an isometric illustration of a crankcase of a V engine. However, the principles explained here can also be applied to other designs of reciprocating internal combustion engines. The illustrated example comprises a first casting, which constitutes a bearing tunnel upper part  1 , and two cylinder blocks  3  and  4 . The first cylinder block  3  is already illustrated in the assembled state in which the cylinder block is screwed together with the bearing tunnel upper part  1 . In the example illustrated in  FIG. 1 , the second cylinder block  4  is still in an intermediate state during assembly. The stud screws (e.g. according to DIN 938) (pre-assembled on the cylinder block) by means of which the second cylinder block  4  is screwed to the bearing tunnel upper part  1  are designated by the numeral  5 . The specific structure of the bearing tunnel upper part  1  and the cylinder block  4  as well as the assembly process are explained in more detail by means of the following  FIGS. 2 to 4 . 
         [0020]      FIG. 2  is a view of the crankcase from  FIG. 1  in a direction indicated by the arrow “I” (see  FIG. 1 ).  FIG. 2  also shows a view from below in the direction of the longitudinal axes  40  (see also  FIG. 3 ) of the cylinder bores in the cylinder block  4 . In  FIG. 2 , the individual bearing points forming the bearing tunnel can be seen. The bearing blocks  11 ,  12 ,  13 ,  14  and  15 , which together with the bearing tunnel lower part  8  (also referred to as bedplate, not illustrated in  FIGS. 1-4 ) form the bearing points for the crankshaft (e.g. sliding bearings), are arranged in the bearing tunnel upper part  1 . 
         [0021]    Through-holes  7  through the bearing tunnel upper part  1  are arranged to the left and to the right of the longitudinal axis  10  of the bearing tunnel upper part  1  (and in a direction perpendicular to the longitudinal axis) and next to the bearing blocks  11 - 15  in the direction of the cylinder block  4 . In the present example, a through-hole  7  is provided on both sides of the bearing block at each bearing point of the bearing tunnel upper part  1 . The longitudinal axes of the through-holes  7  are coaxial to the stud screws  5  screwed into the associated cylinder block  4  (see  FIG. 1 ) and are substantially parallel to the longitudinal axes  40  of the cylinders. The through-holes  7  and the stud screws  5  are more clearly shown in the cross-sectional illustration from  FIG. 3 . The associated sectional plane A-A is illustrated in  FIG. 2 . 
         [0022]    Screwing the cylinder block  4  to the bearing tunnel lower part is explained by means of the cross-sectional illustrations in  FIGS. 3 and 4 . For the sake of simplicity, only the through-holes  7  for the cylinder block  4  are illustrated in the  FIGS. 3 and 4 . However, the longitudinal axes (designated by  7 ′) of the through-holes for the cylinder block  3  are also illustrated. The assembly planes  16  (for the cylinder block  4 ) and  16 ′ (for the cylinder block  3 ) are located on the outside of the bearing tunnel upper part  1 . The surface of the bearing tunnel upper part  1  is substantially planar in these assembly planes  16  and  16 ′ so that the cylinder blocks  3  and  4  fit tightly on the bearing tunnel upper part  1  (in the assembly planes  16  and  16 ′) in the assembled state. In the present example, two through-holes  7  are provided at each bearing point for each cylinder block. In the present example, each of the two cylinder blocks  3  and  4  comprises four cylinders. Therefore, the bearing tunnel has five bearing points. Accordingly, ten through-holes  7  are provided per cylinder block (for ten screw connections in each case). 
         [0023]    Each of the through-holes  7  has an internal thread  71  at the upper end thereof (i.e. at the assembly planes  16  and  16 ′), the internal thread being formed as a right-hand thread in the present example. A threaded sleeve  2  is screwed into each of the internal threads  71 . For this purpose, each threaded sleeve  2  has an external thread  22  which, in the present example, is a right-hand thread that matches the internal thread  71 . The external thread  22  extends along the entire outside of the threaded sleeve. At one end (which faces towards the cylinder blocks  3 ,  4 ), the inside of the threaded sleeves  2  has in each case an internal thread  21  which is formed as a left-hand thread  21  in the present case. At the other end of the threaded sleeves  2  (which faces towards the bearing tunnel upper part  1 ), a hexalobular socket  23  is arranged in each case on the inside thereof. However, other driver profiles for screws such as, e.g., a hexagon socket can also be used. The threaded sleeves  2  are designed in such a manner that they can be screwed onto the ends of the stud screws  5  which protrude from the cylinder blocks  3 ,  4 . This means the ends of the stud screws  5 , which ends protrude from the cylinder blocks  3 ,  4 , have a left-hand thread  51  that matches the internal thread  21 . The arrangement of the threaded sleeve  2  on the bearing tunnel upper part  1  and the cylinder block  4  is shown in more detail in  FIG. 8  ( FIG. 8  shows the detail II from  FIG. 3 ). 
         [0024]    For mounting the cylinder block  4  on the bearing tunnel upper part  1 , the stud screws  5  are already screwed into corresponding internal threads provided in the cylinder block  4 . In the present example, ten stud screws  5  are provided. The threaded sleeves  2  are screwed in first instance into the threads  71  of the through-holes  7  only so far (approx. a quarter turn) that they are fixed in the through-holes  7 . The driver profiles (hexalobular socket  23 ) of the threaded sleeves are oriented towards the bearing tunnel. Thereafter, the cylinder head  4  including the stud screws  5  is arranged on the bearing tunnel upper part  1  in such a manner that each of the stud screws  5  is aligned coaxially to the associated through-hole  7  and engages on the internal thread  21  of the respective threaded sleeve  2 . Screwdriver tools (e.g. with a hexalobular head) can be inserted through the through-holes  7  so as to engage in the driver profiles (hexalobular socket  23 ) in a positive-locking manner. The direction from which the screwdriver tools are inserted into the through-holes  7  during assembly of the cylinder block  4  is indicated by the arrow  24  in  FIG. 4 . By rotating the screwdriver tools (in the present example, a counterclockwise rotation is carried out), the threaded sleeves  2  are screwed simultaneously in a single work step, on the one hand, into the bearing tunnel upper part  1  (right-hand thread pairing with internal thread  71  and external thread  22 ) and, on the other hand, onto the stud screws  5  (left-hand thread pairing with internal thread  21  and external thread  51 ). By dimensioning the thread lengths correctly, the cylinder block  4  can thus be screwed together with the bearing tunnel upper part  1  in a single step, wherein the stud screws  5  (on the cylinder block) and the threaded sleeves  2  (on the bearing tunnel upper part  1  or alternatively on the stud screws  5 ) can be pre-assembled. In the present example, this assembly process takes place two times, one time for the first cylinder block  3  and one time for the second cylinder block  4 . 
         [0025]      FIG. 4  shows substantially the same cross-sectional illustration as  FIG. 3 , wherein, however, the threaded sleeves  2  are screwed in completely so that the cylinder block fits tightly on the bearing tunnel upper part  1 .  FIG. 4  also shows the hole intersections  6   a  between the through-holes  7  (to the cylinder block  4 ) and the through-holes  7 ′ (to the cylinder block  3 ). These hole intersections  6   a  result from the limited space between the individual cylinders (next to the bearing blocks  11 - 15 , see  FIG. 2 ) and from the fact that the cylinder blocks  3  and  4  are constructed substantially identical. 
         [0026]      FIG. 5  is an isometric illustration of the assembled crankcase with the cylinder blocks  3  and  4 , which are screwed together with the bearing tunnel upper part  1  in the above-described manner, and with a bearing tunnel lower part  8  (bedplate) that is screwed together with the bearing tunnel upper part  1 . The bearing tunnel lower part  8  comprises, among other things, bearing caps for the bearing blocks  11 - 15 . In the assembled state, each bearing block in the bearing tunnel upper part  1  together with the associated bearing cap in the bearing tunnel lower part  8  forms a (split) bearing for receiving the crankshaft. 
         [0027]      FIG. 6  is a side view of the example illustrated in  FIG. 5  viewed from the direction designated by “II” in  FIG. 5  (from the right). The main bearing screws  10  and the screws of the transverse screw connection  82  can be seen. Both serve for screwing the bearing tunnel upper  1  and the bearing tunnel lower part  8  together and are explained in more detail below with reference to  FIG. 7 . 
         [0028]      FIG. 7  shows a cross-sectional illustration (similar to  FIG. 4 ) in which the screw connection between the two bearing tunnel parts  1  and  8  can be seen. The associated sectional plane, designated as B-B, is illustrated in  FIG. 6 . Threaded holes  9  are provided in bearing tunnel upper part  1  and associated (i.e. coaxial) through-holes  9 ′ are provided in the bearing tunnel lower part  8  for fastening the two bearing tunnel parts  1 ,  8  to one another. Screws  10  designated as main bearing screws are fed through the through-holes  9 ′ of the bearing tunnel lower part  8  and are screwed into threaded holes  9  of the bearing tunnel upper part  1 , thereby fixing the two bearing tunnel parts to one another. Two screws  10  are provided for each bearing point in the present example so that a total of ten screws  10  are required. The threaded holes  9  in the bearing tunnel upper part likewise intersect the aforementioned through-holes  7  and  7 ′. The corresponding hole intersections are designated by  6   b  (see  FIGS. 3 and 4 ). 
         [0029]    In addition to the main bearing screw connection, a transverse screw connection, which is approximately perpendicular to the main bearing screw connection, can also be provided. For this purpose, the bearing tunnel lower part  8  has threaded holes  81 . The associated through-holes  81 ′ (coaxial to the threaded holes  81 ) are provided in the bearing tunnel upper part  1 . The longitudinal axis of the threaded holes  81  and the through-holes  81 ′ extends in the transverse direction, i.e., approximately perpendicular to the longitudinal axes of the main bearing screw connection. For the transverse screw connection, screws  82  are fed through the through-holes  81 ′ in the bearing tunnel upper part  1  and are screwed into the threaded holes  81  in the bearing tunnel lower part  8 . Two screws  82  for the transverse screw connection are provided for each bearing point so that ten screws  82  are required in the present example. The main bearing screws  10  and the screws  82  for the transverse screw connection  2  can each be screwed in and tightened in one step. 
         [0030]    The method described here for screwing the cylinder blocks  3 ,  4  together with the bearing tunnel upper part  1  enables screwing them together from below during assembly and, at the same time, avoids space constraints which would arise in the case of a conventional screw connection. Next to the bearing blocks  11  to  15  (see  FIG. 2 ), the holes  7  and  7 ′ as well as the threaded hole  9  (see  FIGS. 4 and 7 , intersections  6   b ) intersect (due to lack of space, the holes cannot be arranged next to one another). In order to be able to screw the screws  10  of the main bearing screw connection into the threaded hole  9 , the through-holes  7  and  7 ′ must be clear. Due to the use of the above-described threaded sleeves  2 , the through-holes  7  and  7 ′ are closed by the screwdriver tools (cf.  FIG. 4 , arrow  24 ) only during assembly. Thereafter, the screwdriver tools are removed and the screws  10  can be screwed in without any problems.