Abstract:
A unit pump for use in a combustion engine is disclosed, as well as a method for assembling said combustion engine. The unit pump includes a tappet interacting with a crankshaft or camshaft for providing the fuel injection. The tappet includes first fixing sections interacting with a fastener to position the tappet relative to the cylinder or engine housing of the combustion engine when assembled.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Great Britain Patent Application No. 1501065.5, filed Jan. 22, 2015, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to a unit pump for use in a combustion engine, in particular of a Diesel engine driving a vehicle and relates to the combustion engine including the unit pump. A further aspect of the present disclosure relates to a kit of parts for mounting the unit pump on the combustion engine. Yet another aspect of the present disclosure relates to a method and a computer program for mounting the unit pump to the combustion engine. 
       BACKGROUND 
       [0003]    One of the major concerns of mankind in these days is the global warming that describes an observed century-scale rise in the average temperature of Earth&#39;s climate system. There are studies showing a dependency between rising temperature and rising emissions of carbon dioxide (CO 2 ). Among others CO 2  is released by combustion of fossil fuel so that a significant amount of the CO 2 -emissions is caused by combustion engines used in vehicles. As a consequence, the vehicle manufacturers are intensely searching for ways for reducing CO 2 -emissions. The reduction of weight of the vehicles is one promising way to reduce the CO 2 -emissions. In this respect unit pumps which are a specific type of injection pumps used in gasoline and Diesel engines are considered as an important contribution for the reductions of the CO 2 -emissions. Unit pumps are part of a common rail system and are additional pumps separate from the fuel pump. The unit pumps mainly serve for compressing the fuel delivered by the fuel pump before it is injected into the cylinders of a given combustion engine by respective injectors. One unit pump compresses the fuel injected to all cylinders as do high pressure fuel pumps in conventional Diesel engines. The unit pumps are driven by a camshaft or crankshaft via a tappet and may be located at any suitable position of the engine block of the combustion engine, the engine block typically forming a cylinder head. 
         [0004]    A commonly known concept for the reduction of CO 2 -emissions is the so-called downsizing in which mainly the cylinder capacity is reduced without reducing the power of the respective engine. Moreover, the number of cylinders may also be reduced so that engines having only three cylinders became available recently. As the majority of engines are based on four cylinders, the engine block needs to be redesigned which may be time-consuming and tedious. To avoid the redesign an engine block including four cylinder bores may be used, however, only three of them being equipped with a piston. The unit pump may be inserted into the remaining bore and fastened on the cylinder head. Particularly in the latter case the unit pumps do not need any casing so that their weight can be reduced. Moreover, unit pumps are lubricated by the engine oil and not by the fuel itself as in conventional Diesel engines. Thus, there is no need to lubricate the fuel so that the load on the fuel pump at low pressure can be reduced. Both facts lead to a reduction of CO 2 -emissions. 
         [0005]    Moreover, a very compact and space-saving design can be achieved by integrating the unit pump into the cylinder or engine housing and by using the crankshaft or the camshaft of the combustion engine for actuating the unit pump. 
         [0006]    Usually, the tappet is releasably connectable with the unit pump and movable relative to the unit pump against the pretension force of a pretension device. Depending on the configuration the pretention device is pretentioned either by the camshaft or the crankshaft. Upon assembly of the combustion engine the tappet has to be placed into a position in which the pretention device is pretentioned before the camshaft or the crankshaft is turned into a position to take over the pretentioning of the pretention device. To do so it is necessary that the crankshaft or the camshaft is already mounted on the combustion engine. To hold the tappet in the described position known assembly lines include particularly designed pushing devices. Next to the particular and thus expensive design the pushing devices are difficult to operate, in particular due to the fact that the access to the cylinders is obstructed by the crankshaft and/or the camshaft. 
       SUMMARY 
       [0007]    In accordance with one aspect of the present disclosure a unit pump and a combustion engine is provided that facilitate the mounting of the unit pump on the combustion engine. It is a further aspect of the present disclosure to provide a method for assembling a respective combustion engine. Preferred embodiments of the present disclosure are subject of the following description and claims, as well as the attached figures. 
         [0008]    The respective combustion engine includes a cylinder formed by a cylinder or engine housing, a crankshaft for transmitting the power provided by the combustion engine to power consuming units of the vehicle, and a camshaft for controlling the flow of air/fuel mixture intake and exhaust gases into and out of the cylinder. The unit pump is fixable to the cylinder or engine housing for compressing the fuel delivered by a fuel pump. The unit pump according to one embodiment includes a tappet interacting with the crankshaft or the camshaft for actuating the unit pump. The tappet is provided with first fixing sections interacting with a pin or rod-shaped fastener to position the tappet relative to the cylinder or engine housing upon mounting the unit pump to the combustion engine or upon assembly of the combustion engine. The first fixing sections are designed for an interaction with fastener so that the tappet can be positioned in a desired position relative to the cylinder or engine housing for a certain period of time before the crankshaft or the camshaft are ready to interact with the tappet. It depends on the chosen configuration of the combustion engine whether the camshaft or the crankshaft is interacting with the tappet. The unit pump enables the mounting of the unit pump on the cylinder or engine housing before the combustion engine is provided with the crankshaft or the camshaft. As the crankshaft or the camshaft in this assembling state does not obstruct the access to the cylinder or engine housing the mounting of the unit pump is significantly facilitated. Moreover, the use of the expensive pushing devices is not necessary anymore no that the costs for the assembly line can be reduced. Beyond that the unit pump can be mounted to the cylinder or engine housing in a preassembly station so the logistics and the assembly processes are more flexible and thus more efficient. 
         [0009]    In another embodiment the first fixing sections include recesses and/or protrusions for providing a form closure with the fastener. Recesses and protrusions are easy to provide so that the additional costs for implementing the inventive concept are manageable. Moreover, recesses and protrusions can be provided in a way so that they are very reliable and long-lasting. Providing a form closure for holding the tappet in the assembly position by means of protrusions and recesses is an easy task so that the error rate during the assembly process is very low. 
         [0010]    In a further embodiment the fastener is releasably engagable with the first fixing sections. The fastener can be removed after the crankshaft or the camshaft take over the pretensioning of the pretension device and be used in the assembly of another combustion engine. The fastener is reusable and thus sustainable. 
         [0011]    In an embodiment of a combustion engine, in particular of a Diesel engine driving a vehicle, the combustion engine including a cylinder formed by a cylinder or engine housing. The cylinder or engine housing includes second fixing sections interacting with fastener to position the tappet of a unit pump according to one of the embodiments previously presented relative to the cylinder or engine housing upon mounting of the unit pump on the combustion engine. The advantages and technical effects obtained by this embodiment of the combustion engine are the same as described for the inventive unit pump. In particular the assembly of the combustion engine is facilitated as it is possible to connect the unit shaft to the cylinder or engine housing before the camshaft and the crankshaft are mounted so that the latter do not obstruct the access to the cylinder or engine housing. 
         [0012]    In another embodiment the second fixing sections include recesses and/or protrusions for providing a form closure with the fastener. Recesses and protrusions are easy to provide so that the additional costs for implementing the inventive concept are manageable. Moreover, recesses and protrusions can be provided in a way so that they are very reliable and long-lasting. Providing a form closure for holding the tappet in the assembly position by means of protrusions and recesses is an easy task so that the error rate during the assembly process is very low. 
         [0013]    In yet another embodiment the fastener is releasably engagable with the second fixing sections. The fastener can be removed after the crankshaft or the camshaft take over the pretensioning of the pretension device and be used in the assembly of another combustion engine. The fastener is reusable and thus sustainable. 
         [0014]    The present disclosure also provides a kit of parts for mounting a unit pump on a combustion engine, including a unit pump according to one of the embodiments previously presented, a combustion engine according to one of the embodiments previously presented, and a fastener interacting with the first fixing sections of the unit pump and with the second fixing sections of the combustion engine for positioning the tappet relative to the cylinder or engine housing upon mounting of the unit pump on the combustion engine. 
         [0015]    The advantages and technical effects obtained by this kit of parts for mounting the unit pump on the combustion engine are the same as described for the inventive unit pump and the combustion engine as such. In particular the assembly of the combustion engine is facilitated as it is possible to connect the unit shaft to the cylinder or engine housing before the camshaft and the crankshaft are mounted so that the latter do not obstruct the access to the cylinder or engine housing. 
         [0016]    The present disclosure also provides an embodiment of a method for assembling a combustion engine. A tappet separated from the unit pump is placed in an assembly position relative to the cylinder or engine housing. The tappet is fixed in the assembly position by positioning the fastener so that they interact with the fixing sections. The unit pump or the tappet is provided with a pretension device so that the unit pump is connected with the tappet by connecting the unit pump to the cylinder or engine housing, thereby pretensioning the pretension device. The advantages and technical effects obtained by this method for assembling the combustion engine are the same as described for the inventive unit pump and the combustion engine as such. 
         [0017]    In a further development of the present method the combustion engine further includes a crankshaft for transmitting the power provided by the combustion engine to power consuming units of the vehicle, and a camshaft a camshaft for controlling the flow of air/fuel mixture intake and exhaust gases into and out of the cylinder. The crankshaft or the camshaft is mounted on the combustion engine and turned into a position in which it is interacting with the tappet to fix the tappet in the assembly position. The fastener is removed from the fixing sections. In this embodiment the assembly of the combustion engine is facilitated as it is possible to connect the unit shaft to the cylinder or engine housing before the camshaft and the crankshaft are mounted so that the latter do not obstruct the access to the cylinder or engine housing. 
         [0018]    In another embodiment the tappet is provided separate from the unit pump, and in the first instance placing the tappet in an assembly position relative to the cylinder or engine housing, fixing the tappet in the assembly position by positioning the fastener so that they interact with the fixing sections, providing the unit pump or the tappet with a pretension device, and connecting the unit pump with the tappet by connecting the unit pump to the cylinder or engine housing, thereby pretensioning the pretension device. Next, the crankshaft or the camshaft is mounted on the combustion engine, wherein turning the crankshaft or the camshaft into a position in which it is interacting with the tappet to fix the tappet in the assembly position, and removing the fastener from the fixing sections are conducted in a second place different from the first place. It is thus possible to carry out the assembling process of the combustion engine in at least two different places. Hereby logistical advantages may be realized as a supplier may already mount the unit pumps on the cylinder or engine housing whereas the crankshaft and the camshaft are mounted on the combustion engine by the car manufacturer. 
         [0019]    An embodiment further includes a computer program for mounting a unit pump according to one of the embodiments previously presented on a combustion engine according to one of the embodiments previously presented, the computer program including instructions that, when executed provides the tappet separated from the unit pump, places the tappet in an assembly position relative to the cylinder or engine housing, fixes the tappet in the assembly position by positioning the fastener so that they interact with the fixing sections, provides the unit pump or the tappet with a pretension device, and connects the unit pump with the tappet by connecting the unit pump to the cylinder or engine housing, thereby pretensioning the pretension device. 
         [0020]    The advantages and technical effects obtained by this method for assembling the combustion engine are the same as described for the inventive unit pump, the combustion engine as such and the method for assembling the combustion engine. 
         [0021]    In the context of a combustion engine having a crankshaft for transmitting the power provided by the combustion engine to power consuming units of the vehicle, and a camshaft for controlling the flow of air/fuel mixture intake and exhaust gases into and out of the cylinder, the computer program mounts the crankshaft or the camshaft on the combustion engine, turns the crankshaft or the camshaft into a position in which it is interacting with the tappet to fix the tappet in the assembly position, and removes the fastener from the fixing sections. 
         [0022]    In this embodiment the assembly of the combustion engine is facilitated as it is possible to connect the unit shaft to the cylinder or engine housing before the camshaft and the crankshaft are mounted so that the latter do not obstruct the access to the cylinder or engine housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0024]      FIG. 1  is a schematic view of one embodiment of a unit pump; 
           [0025]      FIGS. 2 to 8  are a cross-section through a cylinder of a combustion engine in which different stages of the assembly process are shown by a schematic diagram; and 
           [0026]      FIG. 9  is a flowchart schematically illustrating a method for assembling a combustion engine having the unit pump shown in  FIGS. 1-8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0028]    In  FIG. 1  one embodiment of a unit pump  10  is shown. The unit pump  10  includes a pump head  12  interacting with a tappet  14 . A pretension device  16 , e.g., a spring, is providing a pretension force between the tappet  14  and the pump head  12  acting along a longitudinal axis L. In operation the tappet  14  is movable along the longitudinal axis L against and with the pretension force whereas the pump head  12  is stationary. The tappet  14  includes a roller  18  rotatably mounted on the tappet  14 . Further the tappet  14  is provided with first fixing sections  20  that are embodied as first recesses  22 . 
         [0029]      FIGS. 2 to 8  are a cross-section through a cylinder  24  of a combustion engine (not shown). The figures schematically show different stages of an assembly process. In  FIG. 2  the first step of the assembly process is demonstrated. The cylinder  24  of the combustion engine is formed by a cylinder or engine housing  26 . The cylinder or engine housing  26  is provided with second fixing sections  28  that are embodied as second recesses  30 . Moreover the cylinder or engine housing  26  has a central bore  32  with a first end  34  and a second end  36 . The central bore  32  can be a cylinder bore of a combustion engine that is not equipped with pistons, valves etc. to perform the combustion process due to downsizing reasons. Existing cylinder bores can be used to arrange the unit pump in a way that its tappet may be driven by the crank shaft that is typically arranged opposite the cylinder head, i.e., at the first end  34 . 
         [0030]    As initially explained the downsizing also includes the reduction of the number of cylinders. A combustion engine including e.g. four cylinders and four cylinder bores may be used but only three of them equipped with pistons, valves etc. to perform the combustion process. The remaining fourth cylinder and the respective central bore  32 , i.e., the cylinder bore, may be used for arranging the unit pump  10 . As the majority of combustion engines used for vehicles include four cylinders the reduction to three cylinders does not require the construction of a new engine block. Moreover, the cylinder bore not used for performing the combustion process is used for the arrangement of the unit pump  10  such that no additional holes or other fastening sections are needed. This concept is not limited to a particular number of cylinders. 
         [0031]    The tappet  14  is separated from the unit pump  10  and fixed in an assembly position relative to the cylinder or engine housing  26  by pin or fastener  38  having a rod-shaped section fastener. The fastener  38  may a bolt. To fix the tappet  14  in the assembly position the fastener  38  is introduced into the first and second fixing sections  20 ,  28 . In the assembly position at least the roller  18  of the tappet  14  is protruding the first end  34 . Moreover, the tappet  14  may have two first fixing sections  20  and the cylinder or engine housing  26  may have two second fixing sections  28  so that the fastener  38  may be U-shaped to simultaneously introduce the fastener  38  into the two first and the second fixing sections  20 ,  28 . 
         [0032]    In the next step of the assembly process as shown in  FIG. 3 , the pump head  12  and the pretension device  16  are introduced into the central bore  32  of the cylinder or engine housing  26  via the second end  36 . Subsequently the pump head  12  is fastened to the cylinder or engine housing  26  by fasteners that are not further shown ( FIG. 4 ). As the tappet  14  is fixed in the assembly position the pretension device  16  is compressed so that the fasteners have to he tightened against the pretension force exerted by the pretension device  16  as indicated by the arrows A. As evident from  FIG. 3  the first recess is slightly oversized with respect to the fastener  38 . As a consequence the tappet  14  is slightly pushed towards the first end  34  when the pump head  12  is fastened to the cylinder or engine housing  26 . The fastener  38  is now butting against an upper surface  40  of the first recess  22 . 
         [0033]    The steps previously described may be conducted in a first location, whereas the subsequent steps may be conducted in a second location to which the combustion engine may be transported meanwhile. 
         [0034]    In  FIG. 5  the next step of the assembly process is shown in which a crankshaft  42  or a camshaft  44  is mounted on the combustion engine. The crankshaft  42  or a camshaft  44  is rotatable around a rotational axis R. The rotational axis R is running perpendicularly through the longitudinal axis L. It depends on the design of the combustion engine whether the crankshaft  42  or the camshaft  44  is interacting with the unit pump  10 , however, the following steps can be conducted regardless of the chosen design. Both the camshaft  44  and the crankshaft  42  have eccentric portions  46 . The camshaft  44  and the crankshaft  42  are mounted so that the eccentric portions  46  initially do not contact the tappet  14 . After that the crankshaft  42  or the camshaft  44  is turned so that the eccentric portion  46  is contacting the roller  18  of the tappet  14  ( FIG. 6 ). In the shown example the crankshaft  42  or the camshaft  44  is turned clockwise around the rotational axis R. Turning the crankshaft  42  or the camshaft  44  further moves the tappet  14  towards the pump head  12  thereby counteracting the pretension force exerted by the pretension device  16 . Thus, the fastener  38  is not butting against the upper surface  40  of the first recess anymore and can now easily be removed. The position of the tappet  14  relative to the cylinder or engine housing  26  is now completely governed by the rotational position of the crankshaft  42  or the camshaft  44 . The unit pump  10  and the crankshaft  42  or the camshaft  44  are now completely mounted and ready to operate ( FIG. 7 ) 
         [0035]    In  FIG. 8 , the camshaft  44  or the crankshaft  42  is in a rotational position in which a line (not shown) between the rotational axis R and the top of the eccentric portion  46  is almost running through the longitudinal axis L. In this rotational position the tappet  14  is almost pushed towards the second end  36  at maximum. However, the fastening means is not removed. Now the fastening means butt against a lower surface  40  of the first recess so no axial movement of the tappet  14  is possible anymore. Consequently the further rotation of the crankshaft  42  or the camshaft  44  is prevented. The blocked camshaft  44  or crankshaft  42  can be used as an indicator that the fastening means was erroneously not removed to ensure proper assembly. The camshaft  44  or the crankshaft  42  has to be turned in the opposite direction, namely counterclockwise to remove the fastening means (see  FIG. 6 ). 
         [0036]    In  FIG. 9 , a flow chart of the method executed by the computer program is given. At Block S 1  the tappet ( 14 ) is provided separated from the unit pump ( 10 ). At Block S 2  the tappet ( 14 ) is placed in an assembly position relative to the cylinder or engine housing ( 26 ) and the tappet ( 14 ) is fixed in the assembly position by positioning the fastener ( 38 ) so that they interact with the fixing sections ( 20 ,  28 ) At Block S 3 , the unit pump ( 10 ) or the tappet ( 14 ) is provided with a pretension device ( 16 ). At Block S 4 , the unit pump ( 10 ) is connected with the tappet ( 14 ) by connecting the unit pump ( 10 ) to the cylinder or engine housing ( 26 ), thereby pretensioning the pretension device ( 16 ). At Block S 5  the crankshaft ( 42 ) or the camshaft ( 44 ) is mounted on the combustion engine. At Block S 6 , the crankshaft ( 42 ) or the camshaft ( 44 ) is rotated into a position in which it is interacting with the tappet ( 14 ) to fix the tappet ( 14 ) in the assembly position. At Block S 7  the fastener ( 38 ) is removed from the fixing sections. The method is described above in the preferred sequence; however,  FIG. 8  is not to be understood in a way that the respective embodiments of the method and the computer program are limited to this sequence. 
         [0037]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.