Abstract:
A method of jointly fitting or removing a piston and a cylinder liner in or from an engine block of an internal combustion engine is provided. During the fitting or removal operation, the cylinder liner is supported or held on a contact shoulder which is arranged at a connecting rod of the piston or at the piston.

Description:
BACKGROUND OF THE INVENTION 
   The present invention concerns a method of jointly fitting and/or removing a piston and a cylinder liner in and/or from an engine block of an internal combustion engine. The invention also concerns an arrangement having a cylinder liner and a piston which can be arranged therein and optionally a connecting rod arranged on the piston as well as the piston, the connecting rod and the cylinder liner itself, and also an internal combustion engine and a gripping device. 
   Particularly in the case of large engines such as, for example, stationary gas engines the problem arises that, for strength reasons, the connecting rod eye which embraces the crankshaft of the internal combustion engine must be so large that the connecting rod can no longer be guided through the cylinder liner when fitting and/or removing the piston. For that situation, it is already known in the state of the art for the piston, connecting rod, and cylinder to be jointly fitted and/or removed. Thus it has already been proposed that gripping devices are to be used, which are fixed both to the piston and also to the cylinder liner. That however suffers from the disadvantage that additional screwthreads, eyes, hooks or the like have to be provided on the piston and the cylinder liner. Alternatively it is also known for spreading bodies to be spread in the cylinder liner and hold the piston under a reduced pressure. That procedure however suffers from the disadvantage that leaks mean that there is always the danger that the piston is not sufficiently securely held in the fitting and/or removal operation. Furthermore, fixing of the cylinder liner, which is based purely on friction, is also suitable rather only for lighter arrangements of cylinder liner and piston. 
   SUMMARY OF THE INVENTION 
   The object of the invention is to provide a method of the general kind set forth, in which the stated problems are avoided. 
   In accordance with the invention, the object is achieved in that during the fitting and/or removal operation, the cylinder liner is supported or held on a contact shoulder (flange) arranged at a connecting rod of the piston and/or at the piston and preferably integrally formed thereon. 
   A basic idea of the invention is therefore that the cylinder liner is to be supported during the fitting and/or removal operation on a contact shoulder which can be disposed on the connecting rod of the piston and/or on the connecting rod, whereby the cylinder liner is securely held. It is thus possible to prevent the cylinder liner from falling down. 
   In an advantageous variant, during the fitting and/or removal operation, the piston and the cylinder liner are jointly, preferably exclusively, held on the piston and/or pushed into the engine block and/or pulled out of the engine block. When smaller cylinder liners and pistons are involved, it is possible in that respect to grip and hold the piston by hand. Particularly with larger and heavier assemblies, however, it is generally appropriate to use a gripping device in order to hold the piston and also hang therefrom the connecting rod and cylinder liner. In all those variants, it is thus provided that the cylinder liner hangs from the connecting rod and/or piston and the entire assembly is gripped or held at the piston. 
   In accordance with a further aspect of the invention, there is also provided a gripping device for gripping around a piston having such an arrangement, which can be used for the method according to the invention. 
   An arrangement comprising a cylinder liner and a piston which can be arranged therein, which is suitable for carrying out the method, provides that the piston and/or the connecting rod has (have) a preferably integrally arranged contact shoulder (flange) at which the cylinder liner can be supported or held during the fitting and/or removal operation. A further aspect of the invention also embraces pistons, connecting rods and cylinder liners which are suitable therefor as well as internal combustion engines which have such an arrangement. The internal combustion engines can be for example stationary gas engines. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details and features of the invention will be apparent from the specific description hereinafter with reference to the drawings, in which: 
       FIG. 1  is a perspective sectional view of an engine block with a first embodiment of an arrangement according to the invention comprising a cylinder liner, a piston and a connecting rod, 
       FIG. 2  is a corresponding vertical and flat section view, 
       FIG. 2   a  is a detail view from  FIG. 2  in the region in which the cylinder liner is supported on the connecting rod in the fitting and/or removal operation, 
       FIG. 3  is a detail section view of the region of the piston and the gripping device, 
       FIG. 4  is a vertical flat section view through a second embodiment according to the invention, and 
       FIG. 4   a  is a detail view from  FIG. 4  in the region in which the cylinder liner is supported on the connecting rod in the fitting and/or removal operation. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 ,  2  and  4  show the condition in which the connecting rod yoke (no longer shown here) is released from the connecting rod  3  and the connecting rod eye  19  has been lifted off the crankshaft  11 . In the illustrated view, the connecting rod  3  has been pushed upwardly on the cylinder head side out of the cylinder liner  6  by means of the mounting bar assembly  10  to such an extent that the two half-shells  8 ′ of the gripping device  8  can be fitted on to and grip around the piston  1 . In order to avoid additional adaptations in respect of the piston to the nature of the gripping device, an advantageous variant provides that the gripping device  8  has at least one projection for engaging into a groove  4  on the piston  1 . After removal of the piston rings, the gripping device  8  can engage directly into the piston ring grooves  4  in which the piston rings are otherwise disposed. Alternatively, the gripping device, can also engage behind the piston  8  by means of preferably inclined gripping surfaces  20 , as shown in  FIG. 3 . 
   In the position shown in  FIGS. 1 ,  2  and  4  the cylinder liner  6  is supported at the contact shoulder (flange)  16  ( FIGS. 1 and 2 ) or at the contact shoulders (flange)  16  and  16 ′ ( FIG. 4 ) of the connecting rod  3 . The embodiment shown in  FIGS. 1 and 2  additionally has on the connecting rod  3 , in opposite relationship to the contact shoulder  16 , a further (secondary) support surface  17  which serves to center the connecting rod  3  in the cylinder liner  6  as soon as the connecting rod  3  is pushed into the position shown in  FIGS. 1 and 2  by the bar assembly  10  which is only present in the assembly operation. The term “centering” in this context is used essentially to denote a fit in accurate register relationship, which prevents the cylinder liner  6  from being able to slip down off the contact shoulder  16  when pulling on the piston  1 . In the embodiment shown in  FIGS. 4 and 4   a , the centering effect is afforded by the cooperation of the two contact shoulders (flanges)  16  and  16 ′. The connecting rod  3  has its maximum diameter in the region of the connecting rod eye  19 . In other words, the maximum diameter of the connecting rod  3  is at its end region which in the operative position is towards the crankshaft  11 , and its maximum diameter is larger than the inside diameter of the cylinder liner  6 . The contact shoulder  16  and the support surface  17  as shown in  FIGS. 1 and 2  or the contact shoulders  16  and  16 ′ as shown in  FIGS. 4 and 4   a  are arranged in the illustrated embodiment in that end region and are formed integrally on the connecting rod  3 . The contact shoulder  16  or the contact shoulders  16 ,  16 ′ as illustrated engages or engage the lower edge  18  of the cylinder liner  6 , which in the installation position faces towards the crankshaft  11 . 
   The operation of fitting the piston  1 , the connecting rod  3  and the cylinder liner  6  by means of a fitting method of a nature in accordance with the invention will now be briefly described hereinafter. Firstly the piston  1 , the gudgeon pin  2  of the piston and the connecting rod  3  are assembled. The gudgeon pin  2  is secured with the gudgeon pin securing rings  5 . That unit which is pre-assembled in that fashion is now introduced into the cylinder liner  6  from below (that is to say on the side of the lower edge  18  of the cylinder liner  6 ). Thereafter the unit consisting of the piston  1  and the connecting rod  3  is pushed upwardly in the cylinder liner  6  to such an extent that the connecting rod  3  is centered in the cylinder liner  6  by means of the contact shoulder  16  and the further support surface  17  or by means of the contact shoulders  16 ,  16 ′. The cylinder liner  6  now rests on the contact shoulder  16  or the contact shoulders  16 ,  16 ′. The piston rings are now fitted on to the piston  1 , and the gripping device  8  must also be fitted thereon. In that case, for example, the two half-shell portions  8 ′ can be fitted on to the piston  1  in such a way that the inclined gripping surfaces  20  engage behind the piston  1 , as shown in  FIG. 3 . 
   The connecting rod bearing shell  15  is now secured to the open connecting rod eye  19  to prevent the shell  15  from rotating with respect to the connecting rod  3 , and the shell  15  is fixed with the fixing lugs  14  shown in  FIGS. 2 and 2   a . In the second embodiment shown in  FIGS. 4 and 4   a , the fixing lugs  14  are admittedly not explicitly shown but they can also be shaped similarly as in the first embodiment. The sealing rings  12  are now fitted externally into the corresponding grooves in the cylinder liner  6 . The unit which is pre-assembled in that way and consisting of the piston, the connecting rod, the cylinder liner and the gripping device is now introduced from above (on the cylinder head side) into the engine block or the crank case  7  after the seating surface in the crank case  7  has been previously provided with a suitable sealing agent which is known in the state of the art. The entire unit is then driven downwardly into the engine block  7 —for example by means of a plastic hammer—until the annular flange  21  on the cylinder liner  6  bears against the corresponding seat on the crank case  7 . That position is to be seen in  FIGS. 1 ,  2  and  4 . The mounting bar assembly  10  is now mounted laterally to the crank case  7  and adjusted or fixed at the fixing lugs  14 , whereby the connecting rod  3  is fixed to the mounting bar assembly  10 . In the second embodiment as shown in  FIGS. 4 and 4   a  the mounting bar assembly  10  does not engage a fixing lug  14 , but instead engages a centering pin  23  on the connecting rod  3 . When that has been done, the gripping device  8  can be removed and a piston insertion sleeve (which is not shown here but which is known in the state of the art) can be centered at the upper cylinder liner fitting entry. After the piston  1  has been released from the gripping device  8 , the connecting rod  3  together with the piston  1  can be moved downwardly by means of the mounting bar assembly  10  and the open connecting rod eye  19  can be fitted on to the crankshaft  11 . Then the connecting rod yoke (which is not shown here but which is known in the state of the art), with the connecting rod bearing shell fitted therein, can be screwed to the connecting rod  3  with its initial tightening torque. After removal of the piston insertion sleeve which is not shown here further operation is effected as is known in the state of the art with a device for clamping down the cylinder liner  6 . That clamping-down device can then be removed after hardening of the sealing agent and after a sealing integrity check. The further steps for fitting the cylinder head at the cylinder head bolts  9  are known in the state of the art. 
   In the removal operation, the procedure involved in accordance with the invention can be as follows: firstly the connecting rod yoke which is not shown in the drawings, with the bearing shell  15 , is unscrewed from the connecting rod eye  19  and removed. The fixing lugs  14  are screwed to the connecting rod  3  in the first embodiment of  FIGS. 1 and 2 . Thereafter, the mounting bar assembly  10  is mounted to the crank case  7  and adjustment or fixing of the mounting bar assembly  10  to the lower fixing lug  14  is effected, whereby the connecting rod  3  is fixed or secured to the bar assembly  10 . In the second embodiment, the mounting bar assembly  10  does not engage the fixing lug  14 , but instead engages the centering pin  23 . Now, the unit consisting of the connecting rod  3  and the piston  1  is pushed upwardly by means of the mounting bar assembly  10 , that is to say away from the crankshaft  11 , to such an extent that the connecting rod  3  is centered in the cylinder liner  6  by means of the further support surface  17  or the two contact shoulders  16 ,  16 ′, whereby then the cylinder liner  6  automatically bears against the contact shoulder  16  or the contact shoulders  16 ,  16 ′ of the connecting rod  3 . In that upward displacement, the piston  1  is pushed upwardly out of the cylinder liner  6  to such an extent that the piston rings in the piston ring grooves  4  snap out of the cylinder liner  6  whereby the piston  1  and the connecting rod  3  are prevented from sliding back. The gripping device  8  is then fitted. In that respect, in a first variant, the two gripping surfaces  20  can engage behind the piston  1  as shown in  FIG. 3 . Alternatively, the sealing rings are first removed from the piston ring grooves  4  so that the piston ring grooves  4  can be engaged by means of suitable projections on the gripping device  8 . In both variants at any event after conclusion of the mounting operation the gripping device  8 , the piston  1 , the connecting rod  3  and the cylinder liner are fixed. Subsequently to the above-depicted steps, the cylinder liner  6  now has to be released from the crank case  7 . For that purpose it may be sufficient for the connecting rod  3  and the cylinder liner  6  supported thereon to be further pushed upwardly out of the crank case  7  by means of the mounting bar assembly  10 . Frequently, however, in particular after operation over a prolonged period of time, it happens that the cylinder liner  6  is very firmly seated in the crank case  7 . If that is the case, the unit consisting of the gripping device  8 , the piston  1 , the connecting rod  3  and the cylinder liner  6  can be pressed upwardly by some millimeters by means of the hydraulic cylinders  13  shown in  FIG. 3  so that the connection between the cylinder liner  6  and the crank case  7  is released. As shown in  FIG. 3  it is advantageous if the hydraulic cylinders  13  are supported against the crank case  7  and press against corresponding projections  22  on the gripping device  8 . After release of the cylinder liner  6 , the entire unit, hanging from the gripping device  8 , can be lifted out of the crank case  7  by hand or, when dealing with larger units, by means of a crane. In the release operation as also in the operation of lifting the unit out, the cylinder liner  6  can be supported according to the invention on the connecting rod  3 , while the gripping device  8  engages the piston  1 . The further steps in the removal procedure are performed in the reverse sequence to the fitting procedure and therefore do not have to be set forth separately once again here.