Patent Publication Number: US-10309359-B2

Title: High-pressure fuel pump

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a high-pressure fuel pump, in particular of a common-rail injection system of an internal combustion engine, having a pump cylinder head, having a suction valve arranged in the direction of the pump cylinder axis in the pump cylinder head, and having a high-pressure fuel outlet arranged laterally on the pump cylinder head, wherein a protective cap is provided which at least partially covers the high-pressure fuel pump. 
     A high-pressure fuel pump of said type is known from DE 10 2013 211 176 A1. Said high-pressure fuel pump of a common-rail injection system of an internal combustion engine has a pump cylinder head which is formed in one piece with a pump cylinder. In the pump cylinder head, in the direction of the pump cylinder axis, there is arranged a suction valve via which fuel can be introduced into a pump working chamber. Furthermore, a high-pressure fuel outlet with a check valve is arranged laterally on the pump cylinder head. On the pump cylinder head, there is mounted a protective cap which surrounds the pump cylinder head and which has a continuous headwall in particular in the region of the suction valve. 
     The invention is based on the object of providing a high-pressure fuel pump having a protective cap, in the case of which the protective cap can be mounted on an assembled high-pressure fuel pump. 
     SUMMARY OF THE INVENTION 
     Said object is achieved in that an electrical plug with a lateral line connector is mounted onto the electrically actuated suction valve, and in that the protective cap, in a first embodiment, is formed in two parts and has two protective cap parts. The object is likewise achieved in that an electrical plug with a lateral line connector is mounted onto the electrically actuated suction valve, and in that the protective cap, in a second embodiment, is of ring-shaped form and has a clearance slot which interrupts the ring-shaped protective cap. The protective cap formed in this way can, in both embodiments, be mounted on an assembled high-pressure fuel pump without the need for the electrical plug of the electrical connector line for the actuation of the electrically actuated valve having to be removed. In this way, the reliability of the installation of the high-pressure fuel pump is increased through the avoidance of a situation in which the electrical plug has to be dismounted for the purposes of mounting the protective cap and is possibly subsequently mounted again incorrectly. Here, the protective cap that can be mounted in this way furthermore performs further tasks. The pump cylinder head of the high-pressure fuel pump is produced from a metallic material, preferably as a cast part, and is mechanically blank on its surface pointing toward the surroundings. In particular, the pump cylinder head is not covered by a corrosion prevention means, for example in the form of a lacquer. The pump cylinder head can therefore corrode over the course of time without impairing the function of the high-pressure fuel pump, which constitutes an undesired visual appearance. Since the pump cylinder head is however covered with the protective cap formed according to the invention, this negative appearance is avoided. Furthermore, the protective cap constitutes a noise shield, which is effective in suppressing noise emissions originating from the high-pressure fuel pump. Finally, the protective cap constitutes a thermal guard for example for preventing the high-pressure fuel pump, that has warmed up during operation, from being touched. Since the electrical plug is manufactured from a non-metallic material, in particular from a plastics material, said electrical plug can perform the functions discussed above in addition to the protective cap, such that the protective cap designed according to the invention can have an aperture region in the region of the electrical plug without restricting functionality. In other words, said aperture region thus in particular forms a recess around the electrical plug. 
     The protective cap formed in two parts may be composed of two entirely independent protective cap parts, which are connected to one another during the mounting process. For this purpose, the two protective cap parts preferably each have a detent hook which engages into a corresponding detent groove of the second protective cap part. The two protective cap parts may however also be connected to one another at one side by means of a hinge, wherein, during the mounting process, the two protective cap parts are pivoted about the pump cylinder head and are connected to one another on the opposite side in relation to the hinge by means of the detent hook that engages into the detent groove. Here, the parting plane of the two protective cap parts preferably lies transversely with respect to the axis of the high-pressure fuel outlet. Furthermore, in the region of the high-pressure outlet, one protective cap part has a downwardly open recess, whereas the second protective cap part is formed without a recess. The protective cap thus formed from two protective cap parts can be mounted very easily. 
     The hinge that connects the two protective cap parts is advantageously designed as a film hinge. That is to say, the two protective cap parts are integrally connected by means of the film hinge. The two parts of the protective cap accordingly need not imperatively be two entirely independent protective cap parts. During the mounting process, the two protective cap parts connected by means of the film hinge are placed around the pump cylinder head so as to enclose the latter in ring-shaped fashion. At their ends respectively situated opposite the film hinge, the two protective cap parts are subsequently connected. The connection may in turn be realized by means of a detent or snap-action connection. No auxiliary tool is required for this purpose. 
     The film hinge preferably permits pivoting of the two protective cap parts about a pivot axis which runs parallel to the pump cylinder axis. In this case, the two protective cap parts may be formed as half-shells which are pivotable relative to one another and which, after being placed on and connected, form a substantially ring-shaped protective cap. 
     In a further embodiment of the invention, it is preferable for both protective cap parts to have in each case one domed projection which extends in the direction of the electrical plug. When the protective cap has been mounted, said domed projection forms a ring which surrounds a sleeve nut by means of which the suction valve is fastened to the pump cylinder head. Here, the domed projection may be formed so as to directly adjoin the electrical plug, so as to realize a visually unitary appearance of said components. The protective cap with the protective cap parts and the domed projection are preferably manufactured from a plastics material, and can thus be easily produced in a corresponding injection mold. Here, the abovementioned hinge may easily be designed as a connecting lug of the two covering parts, in particular as a film hinge. Finally, by means of this embodiment, a possible ingress of water into the suction valve is reduced in that a partition with respect to the lower region of the sleeve nut can be realized by means of the protective cap. 
     The protective cap of ring-shaped form with the clearance slot which interrupts the ring-shaped protective cap is fitted over the electrical plug with the line connector, and the clearance slot is thus aligned relative to the lateral high-pressure fuel outlet such that the latter is arranged in the clearance slot when the protective cap has been mounted. The protective cap thus formed can be mounted easily in the case of an electrical plug with a lateral or upwardly directed line connector, wherein the lateral cable exit of the electrical plug may be pivoted through any desired angle with respect to the lateral high-pressure fuel outlet. In all possible embodiments, the protective cap is fitted with the clearance slot firstly over the line connector (with the onward-leading lines) of the electrical plug, and the protective cap is then pivoted such that the clearance slot is aligned in the direction of the lateral high-pressure fuel outlet. The protective cap is then pushed downward onto the pump cylinder head. 
     In a refinement of the invention, the protective cap has clamping lugs which are adjacent to the clearance slot and which serve for interacting with a clamping ring. After the mounting of the protective cap onto the pump cylinder head, the clamping ring is mounted over the high-pressure fuel outlet and is pushed over the two clamping lugs. The protective cap is thus connected in the region of the clearance slot so as to form a continuous component. Here, the clamping ring preferably has a covering lug for the clearance slot, such that a continuous top wall is formed after the mounting process has been performed. 
     In a further embodiment of the invention, the protective cap has a domed projection which extends in the direction of the electrical plug and which has a slot. This embodiment ensures that the above-described sleeve nut for the fastening of the suction valve is also encased. Here, the domed projection and the protective cap may be formed as separate components, which are mounted one after the other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantageous embodiments of the invention emerge from the description of the drawings, in which exemplary embodiments of the invention illustrated in the figures are described in more detail. 
       In the figures: 
         FIG. 1  shows a perspective partial view of a high-pressure fuel pump with a mounted protective cap which is composed of two protective cap parts, 
         FIG. 2  shows a further perspective partial view of a high-pressure fuel pump with a mounted protective cap, 
         FIG. 3  shows a side view of a high-pressure fuel pump with, in section, a protective cap, 
         FIG. 4  shows a detailed view of a protective cap, 
         FIG. 5  shows a perspective partial view of a high-pressure fuel pump with a protective cap which has a domed projection, 
         FIG. 6  shows a perspective partial view of a high-pressure fuel pump with a mounted protective cap in a further embodiment, 
         FIG. 7  shows a further partial view of a high-pressure fuel pump with a protective cap analogous to  FIG. 6 , 
         FIG. 8  shows a further perspective partial view of a high-pressure fuel pump with a protective cap analogous to  FIG. 6 , 
         FIG. 9  shows a further perspective partial view of a high-pressure fuel pump with a mounted protective cap analogous to  FIG. 6 , and 
         FIGS. 10 a  and 10 b    are plan views of a two-part protective cap with film hinge a) open and b) closed. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  show the upper part of a high-pressure fuel pump  1  having a pump housing  2  on which a pump cylinder head  3  (see in particular  FIG. 2 ) is mounted. By contrast to  FIG. 1 ,  FIG. 2  shows a protective cap  10  that has been sectioned in the plane of the high-pressure fuel outlet  5 , in order to provide a better illustration of the pump cylinder head  3 . The pump cylinder head  3  is fastened to the pump housing  2  by means of four screws  4 , and has a lateral high-pressure fuel outlet  5 . A high-pressure line is fastenable to the high-pressure fuel outlet  5 , through which high-pressure line the fuel delivered by the high-pressure fuel pump  1  is conducted into a high-pressure accumulator. The high-pressure fuel pump  1  is preferably part of a common-rail injection system which is installed on an internal combustion engine. Here, the high-pressure fuel pump  1  is fed with fuel from a low-pressure system through a feed arranged in the pump housing  2  and in the pump cylinder head  3 , wherein the metered fuel quantity is determined by a suction valve  6  formed as an electrically actuated valve. The suction valve  6  is fastened to the pump cylinder head  3  by means of a sleeve nut  7 . The suction valve  6  connects the feed to a pump working chamber in the pump cylinder head  3  in order to define the fuel delivered by the high-pressure fuel pump  1 . An electrical plug  8  with a lateral line connector  9  is mounted onto the suction valve  6 . The line connector  9  is preferably formed in one piece with an onward-leading signal line (not illustrated) which is connected to a control unit for actuating the suction valve. In the exemplary embodiment illustrated, the electrical plug  8  is oriented with the lateral line connector  9  rotated relative to the high-pressure fuel outlet  5  through approximately 90°. 
     Onto the pump cylinder head  3 , which is produced from a metallic material, for example by casting, and which is metallically blank on its surface pointing toward the surroundings, there is mounted a protective cap  10  which is composed of two protective cap parts  11   a ,  11   b . The parting plane  12  that defines the two protective cap parts  11   a ,  11   b  runs transversely with respect to, in particular, the high-pressure fuel outlet  5 . Accordingly, the protective cap part  11   b  has a recess  13  which surrounds the high-pressure fuel outlet  5  and which is open toward the pump housing  2 . The two protective cap parts  11   a ,  11   b  have in each case one detent hook  14 , which can be engaged into an oppositely situated detent groove  15  of the other protective cap part  11   b ,  11   a . Alternatively, at one side, instead of a detent hook  14  and a detent groove  15 , the two protective cap parts  11   a ,  11   b  may also have a hinge which connects the two protective cap parts  11   a ,  11   b . The protective cap parts  11   a ,  11   b  are preferably produced from a plastics material, such that the hinge may be formed as an elastic lug which connects the two protective cap parts  11   a ,  11   b.    
     To ensure a secure seat of the protective cap  10  on the pump cylinder head  3 , the two protective cap parts  11   a ,  11   b  have clamping lugs  16  which, as can be seen from  FIG. 3 , project under the sleeve nut  7 . 
       FIG. 4  shows a further embodiment of the clamping lugs  16  of the two protective cap parts  11   a ,  11   b , which are additionally hooked one into the other. 
       FIG. 5  shows a protective cap  10  analogous to the embodiments described in the preceding figures, wherein, in the embodiment illustrated in  FIG. 5 , the protective cap  10  has a domed projection  17  which surrounds the sleeve nut  7  and which in turn is composed of two domed projection parts  18   a ,  18   b , which are in each case formed in one piece with the protective cap parts  11   a ,  11   b . Ultimately, by means of this embodiment, a possible ingress of water into the suction valve  6  is reduced in that a partition with respect to the lower region of the sleeve nut  7  is realized by means of the protective cap  10  together with the domed projection  17 . 
     In the embodiments of the protective cap  10   a  illustrated in  FIGS. 6 to 9 , said protective cap is of ring-shaped form and has a clearance slot  19  which interrupts the ring. The protective cap  10   a  is mounted by being fitted, as illustrated in  FIG. 6 , over the electrical plug  8  with the lateral line connector  9 , then, when situated below the lateral line connector  9 , being rotated as shown in  FIG. 7  such that the clearance slot  19  lies above the lateral high-pressure fuel outlet  5 , and then being fitted over the pump cylinder head  3  until it makes contact with the pump housing  2 , as shown in  FIG. 8 . The protective cap  10   a  has clamping lugs  20  arranged to both sides of the clearance slot  19 . A clamping ring  21  can be pushed onto said clamping lugs  20 , as illustrated in  FIG. 9 . The clamping ring has a covering lug  22  which, when the clamping ring  21  has been mounted, covers the clearance slot  19  at the top wall of the protective cap  10   a.    
     The protective cap  10   a  may also have a domed projection (not illustrated) which has an elongated slot above the clearance slot. The domed projection is preferably formed from an elastic plastic, such that it can be rotated under the line connector  9  in a reversibly deformable manner. In this embodiment, the clamping ring may be designed such that a widened covering lug also covers the clearance slot of the domed projection. Alternatively, the domed projection may also be formed separately from the protective cap  10   a  and mounted after the protective cap  10   a  has been mounted. 
       FIG. 10  shows a unipartite embodiment of a two-part protective cap  10 . This is because, in this case, the two protective cap parts  11   a  and  11   b  are connected by means of a film hinge  23 . The pivot axis of the film hinge  23  runs parallel to the pump cylinder longitudinal axis, such that two protective cap parts  11   a  and  11   b  in the form of two half-shells are formed, which are pivotable relative to one another. The parting plane  12  running through the pivot axis is, with regard to its angular position, arranged offset with respect to the center of the recess  13  by 90°. The recess  13 , which serves for receiving the high-pressure fuel outlet  5 , is in the present case formed in the protective cap part  11   b.    
     During the mounting of the protective cap  10 , the two protective cap parts  11   a  and  11   b  are pivoted relative to one another such that an opening is formed on the side situated opposite the film hinge  23  (see  FIG. 10 a   ). The opening enables the protective cap  10  to be placed onto the pump cylinder head  3  such that the high-pressure fuel outlet  5  comes to lie within the recess  13  of the protective cap part  11   b . The other protective cap part  11   a  is subsequently pivoted such that the two protective cap parts  11   a  and  11   b  enclose the pump cylinder head  3  in ring-shaped fashion. Here, a detent hook  14  formed on the protective cap part  11   a  engages into a detent groove  15  formed on the protective cap part  11   b  (see  FIG. 10 b   ). 
     The two protective cap parts  11   a  and  11   b  illustrated in  FIG. 10  together form a domed projection  17 . For this purpose, they have in each case one domed projection part  18   a  and  18   b  respectively. If no domed projection  17  is required, the two protective cap parts  11   a  and  11   b  may also be formed without domed projection parts  18   a  and  18   b —analogously to the embodiment illustrated in  FIG. 1 .