Patent Publication Number: US-10330066-B2

Title: High-pressure fuel pump

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage Application of International Application No. PCT/EP2015/073137 filed Oct. 7, 2015, which designates the United States of America, and claims priority to DE Application No. 10 2014 220 878.5 filed Oct. 15, 2014, the contents of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to high-pressure fuel pumps and the teaching may be applied to pumps in which a pump piston, by means of which a fuel is acted on with a high pressure, is guided in a guiding sleeve. 
     BACKGROUND 
     High-pressure fuel pumps are often used for fuel injection systems for internal combustion engines. They exert high pressure on a fuel to be supplied to a combustion chamber of the internal combustion engine and are mostly constructed as piston pumps. In such pumps, a pump piston compresses the fuel located in a pressure chamber by means of a translational back and forth movement and consequently produces a high pressure in the fuel. For example, with high-pressure fuel pumps for petrol internal combustion engines, the fuel is acted on with a pressure of from 200 bar-300 bar whilst the fuel for diesel internal combustion engines is acted on with a pressure of from 2000 bar-3000 bar. 
     As a result of the high pressures, it is advantageous from a tribological viewpoint to provide a wear-resistant configuration of a piston guide in which the pump piston is guided. To this end, for example, it is known to use a specially constructed guiding sleeve for the pump piston. Such a high-pressure fuel pump is known, for example, from DE 103 22 603 B4. 
     A positive-locking connection is achieved therein between a guiding sleeve for the pump piston and a housing of the high-pressure fuel pump by pressing in the guiding sleeve and caulking a collar to the housing. 
     However, this type of positive-locking connection involves high necessary assembly forces of several kN and produces tensions in the components, which may lead to deformations of these components. In this instance, deformations, for example, of valve seats of the high-pressure fuel pump or the guide of the pump piston itself are considered to be particularly critical since they can lead to internal leakage paths and consequently in the worst case to loss of the function of the high-pressure fuel pump. 
     In addition, during operation of the high-pressure fuel pump, as a result of the operating conditions such as temperature, oscillations, etcetera, a settling behavior of the positive-locking connection may take place at the caulking of the guiding sleeve and a leakage path from a pressure chamber of the high-pressure fuel pump via the outer diameter of the guiding sleeve may thereby occur again since the required pretensioning of the guiding sleeve at the side which is directed toward the pressure chamber is no longer ensured. 
     SUMMARY 
     The teachings of the present disclosure may provide a high-pressure fuel pump which overcomes the problems mentioned. 
     Some embodiments may include a high-pressure fuel pump ( 10 ) having: a housing ( 12 ) having a housing recess ( 14 ), and a guiding sleeve ( 18 ) which is arranged in the housing recess ( 14 ) for guiding a pump piston ( 16 ) of the high-pressure fuel pump ( 10 ). The guiding sleeve ( 18 ) is connected to the housing recess ( 14 ) by means of a materially engaging connection ( 38 ). 
     In some embodiments, the materially engaging connection ( 38 ) has an adhesive connection ( 41 ) which comprises an adhesive ( 40 ). 
     In some embodiments, the adhesive ( 40 ) is thermally stable up to a temperature of at least 180° C. 
     In some embodiments, the adhesive ( 40 ) is insoluble in fuels ( 26 ), in particular in petrol and/or diesel. 
     In some embodiments, the guiding sleeve ( 18 ) is arranged in an offset ( 20 ) of the housing recess ( 14 ) which extends adjacent to a pressure chamber ( 22 ) of the high-pressure fuel pump ( 10 ) as far as a chamber ( 34 ) at an end of the pump piston ( 16 ) opposite the pressure chamber ( 22 ), wherein the offset ( 20 ) has an offset end face ( 46 ) on which a guiding sleeve end face ( 48 ) of the guiding sleeve ( 18 ) is arranged, wherein the adhesive ( 40 ) is arranged between the offset end face ( 46 ) and the guiding sleeve end face ( 48 ). 
     In some embodiments, the offset ( 20 ) has an offset side face ( 52 ) on which a guiding sleeve side face ( 54 ) is arranged, wherein the adhesive ( 40 ) is arranged between the offset side face ( 52 ) and the guiding sleeve side face ( 54 ). 
     In some embodiments, the materially engaging connection ( 38 ) has a weld connection ( 42 ), in particular a friction weld connection. 
     In some embodiments, the materially engaging connection ( 38 ) has a region in which the guiding sleeve ( 18 ) is vulcanized to the housing recess ( 14 ). 
     In some embodiments, a sealing arrangement ( 50 ) is provided between the housing recess ( 14 ) and the guiding sleeve ( 18 ). 
     In some embodiments, the guiding sleeve ( 18 ) is formed from a material which has a greater hardness than the material of the housing ( 12 ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The teachings of the present disclosure are explained in greater detail below with reference to the appended drawings, in which: 
         FIG. 1  is a longitudinally sectioned view of a first embodiment of a high-pressure fuel pump with a materially engaging connection between a guiding sleeve and a housing recess; 
         FIG. 2  is a longitudinally sectioned view of a second embodiment of a high-pressure fuel pump with a materially engaging connection between the guiding sleeve and the housing recess; 
         FIG. 3  is a longitudinally sectioned view of a third embodiment of a high-pressure fuel pump with a materially engaging connection between the guiding sleeve and the housing recess, wherein an additional sealing arrangement is provided. 
     
    
    
     DETAILED DESCRIPTION 
     In some embodiments, a high-pressure fuel pump has a housing having a housing recess and a guiding sleeve which is arranged in the housing recess for guiding a pump piston of the high-pressure fuel pump. The guiding sleeve is connected to the housing recess by means of a materially engaging connection. 
     In place of the positive-locking connection, therefore, the pump may include a materially engaging connection of the components housing and guiding sleeve of the high-pressure fuel pump. Tensions and deformations in these components can thereby be prevented, which leads to a reduction of defects in the high-pressure fuel pump. Some embodiments may include a guiding gap between the guiding sleeve and the pump piston which is guided therein which during operation is filled with a fuel in order to thus act as a lubricant during the movement of the pump piston in the guiding sleeve. 
     In some embodiments, the materially engaging connection has an adhesive connection which comprises an adhesive. Adhesives may be fitted in the housing recess or to the guiding sleeve in a simple manner so that the guiding sleeve can be connected to the housing by means of a particularly simple method. The adhesive may be thermally stable up to a temperature of at least 180° C. 
     During operation of the high-pressure fuel pump peak temperatures between 150° C. and 180° C. may occur. Embodiments with an adhesive that does not soften in this temperature range may improve the performance of the connection between the housing and guiding sleeve and reduce the chance it might become disengaged. In some embodiments, the adhesive may be thermally stable and not soften up to a temperature of at least 180° C. 
     In some embodiments, the adhesive may be insoluble in fuels, in particular in petrol and/or diesel. If the adhesive does not dissolve as a result of contact with fuel, the connection between the housing and guiding sleeve may not become disengaged. 
     For example, the adhesive may be based on water glass and/or cement and/or polyurethane. Adhesives based on these materials which have a high temperature-resistance and insolubility in fuels, which is advantageous for the above-mentioned reasons, are commercially available. The guiding sleeve may be arranged in an offset of the housing recess which extends adjacent to a pressure chamber of the high-pressure fuel pump as far as a chamber at the other end of the pump piston. In this instance, the offset may have an offset end face on which a guiding sleeve end face of the guiding sleeve is arranged, wherein the adhesive is arranged between the offset end face and the guiding sleeve end face. 
     Such embodiment may provide sealing of a joint between the housing recess and guiding sleeve toward the pressure chamber automatically. A fuel leak in the joint between the housing recess and guiding sleeve can thereby be avoided. 
     In some embodiments, the offset has an offset side face on which a guiding sleeve side face is arranged, wherein the adhesive is arranged between the offset side face and the guiding sleeve side face. If the adhesive is arranged not only in the region of the end faces, but instead also in the region of the side faces, an improved sealing of the joint with respect to a fuel leakage may be produced. 
     Alternatively or additionally, the materially engaging connection may have a weld connection. For example the weld connection may be a friction weld connection, that is to say, a weld connection in which the guiding sleeve has been connected by means of advantageous rubbing-together of a guiding sleeve surface and a housing recess wall with the housing recess. 
     Weld connections may be particularly secure and sealed against a fuel leakage. Alternatively or additionally, the materially engaging connection may also have a region in which the guiding sleeve is vulcanized to the housing recess. 
     Some embodiments may include a sealing arrangement between the housing recess and the guiding sleeve. An additional sealing arrangement may prevent, together with the materially engaging connection, the introduction of fuel leakage into the joint between the housing recess and guiding sleeve. 
     In some embodiments, the guiding sleeve is formed from a material which has a greater hardness than the material of the housing. It is thereby possible to achieve a wear-resistant construction of the pairing pump piston/guiding sleeve. At the same time, the high-pressure fuel pump can be constructed in a more cost-effective manner since only the region which is subjected to wear as a result of movement of the pump piston, that is to say, the guiding sleeve, is formed from the higher-quality material whilst the housing is formed from a standard material which is more cost-effective. For example, the guiding sleeve may be constructed from a hardened high-grade steel, whilst the housing is formed from a normal high-grade steel. 
     In some embodiments, in which the materially engaging connection has a weld connection or a vulcanized region, these regions may also be located on the respective end faces of the offset and guiding sleeve in order in this instance to lead to a sealing action of the materially engaging connection directly in the region of the pressure chamber. 
     Improved sealing of the connection can be further achieved when this type of materially engaging connection—weld connection or vulcanization—is also arranged in regions of the side faces of the guiding sleeve and offset. 
     It is further also possible in this instance to arrange a sealing arrangement between the housing recess and guiding sleeve. 
       FIG. 1  is a longitudinally sectioned view of a high-pressure fuel pump  10  which has a housing  12  with a housing recess  14  in which a pump piston  16  and a guiding sleeve  18  are arranged in order to guide the pump piston  16 . 
     The guiding sleeve  18  is formed from a harder material than the housing  12  so that, in the region of the pairing pump piston  16 /guiding sleeve  18 , a wear-resistant construction of the high-pressure fuel pump  10  can be achieved. 
     The housing recess  14  has an offset  20  in which the guiding sleeve  18  is arranged. In an upper region of the housing recess  14 , there is formed a pressure chamber  22  in which a fuel  26  can be introduced via a valve  24 . 
     The pump piston  16  is movably guided along a longitudinal axis  28  in the guiding sleeve  18 . In this instance, there is formed between the guiding sleeve  18  and pump piston  16  a guiding gap  30  which is filled during operation with the fuel  26  as a lubricant so that the guiding sleeve  18  is arranged in the housing recess  14  in a force-free manner during operation. 
     As a result of the translational movement of the pump piston  16  along the longitudinal axis  28 , the fuel  26  located in the pressure chamber  22  is compressed and acted on with high pressure. The fuel  26  acted on with pressure is then discharged from the pressure chamber  22  via an additional valve  32  and is supplied to a combustion chamber (not shown) of an internal combustion engine. 
     The offset  20  opens opposite the pressure chamber  22  relative to a chamber  34  at the lower end of the pump piston  16 . 
     The guiding sleeve  18  is secured in the offset  20  by means of a materially engaging connection  38 . 
     The materially engaging connection  38  may in this instance be formed by an adhesive  40  and may consequently form an adhesive connection  41 , but it may also be a weld connection  42 , such as, for example, a friction weld connection or a vulcanized region  44 . 
     In the embodiment shown in  FIG. 1 , the materially engaging connection  38  is constructed between an offset end face  46  and a guiding sleeve end face  48  which are arranged adjacent to the pressure chamber  22  in the housing  12 . 
     In some embodiments, the materially engaging connection  38  may be resistant against an influence of the fuel  26 , that is to say, for example, in the embodiment using adhesive  40 , for the adhesive  40  not to be soluble in the fuel  26 . 
     In some embodiments, the materially engaging connection  38 , in particular the adhesive  40 , may be able to withstand temperature ranges of up to 180° C. and to be thermally stable, that is to say, not to melt in these temperature ranges. 
     In the embodiment according to  FIG. 1 , the materially engaging connection  38  is used not only to connect the housing recess  14  and guiding sleeve  18 , but at the same time also as a sealing arrangement  50  which prevents a leakage of fuel from the pressure chamber  22  to the chamber  34 . 
     In some embodiments, such as that shown as the longitudinally sectioned view in  FIG. 2 , the materially engaging connection  38  is arranged not only on the offset end face  46  or the guiding sleeve end face  48 , but also on offset side faces  52  or guiding sleeve side faces  54 . It is thereby possible to achieve even better securing of the guiding sleeve  18  in the housing recess  14  and on the whole also a better sealing action of the materially engaging connection  38  which acts as a sealing arrangement  50 . 
       FIG. 3  is a longitudinally sectioned view of an embodiment of the high-pressure fuel pump  10  in which in addition to the materially engaging connection  38  in the region of the offset end face  46  or the guiding sleeve end face  48 , a separate sealing arrangement  50 , for example, an  0  ring  56 , is provided for sealing a joint  58  between the housing recess  14  and the guiding sleeve  18  against a fuel leakage. The high-pressure fuel pump  10  consequently has a first sealing arrangement  50  and a second sealing arrangement  50  of different types. 
     In contrast to known pumps, the materially engaging connection  38  replaces a positive-locking connection of the components guiding sleeve  18  and housing  12  by means of pressing and caulking and thus prevents the occurrence of tensions via the high assembly forces required, and consequently at the same time deformations in the components. 
     Secondly, the materially engaging connection  38  acts as a seal against a fuel leakage from the pressure chamber  22  so that, in principle, it would be possible to dispense with additional sealing arrangements  50 . 
     LIST OF REFERENCE NUMERALS 
     
         
           10  High-pressure fuel pump 
           12  Housing 
           14  Housing recess 
           16  Pump piston 
           18  Guiding sleeve 
           20  Offset 
           22  Pressure chamber 
           24  Valve 
           26  Fuel 
           28  Longitudinal axis 
           30  Guiding gap 
           32  Valve 
           34  Chamber 
           36  Tappet 
           38  Materially engaging connection 
           40  Adhesive 
           41  Adhesive connection 
           42  Weld connection 
           44  Vulcanized region 
           46  Offset end face 
           48  Guiding sleeve end face 
           50  Sealing arrangement 
           52  Offset side face 
           54  Guiding sleeve side face 
           56  O ring 
           58  Joint