Patent Publication Number: US-9840995-B2

Title: High-pressure pump

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional of U.S. application Ser. No. 13/433,561, filed Mar. 29, 2012 which claims the benefit of Japanese Patent Application No. 2011-78484 filed on Mar. 31, 2011, the disclosures of both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a high-pressure pump which pressurizes and discharges a fuel. 
     BACKGROUND 
     A high-pressure pump has a plunger which reciprocates to pressurize fuel in a pressurizing chamber. When the plunger slides down, the fuel is suctioned into a pressurization chamber through a suction passage. When the plunger slides up, the metered quantity of fuel is pressurized to be discharged through a discharge passage. JP-2004-138062A shows such a high-pressure pump in which a cylinder engaged with a housing has a through-hole through which a plunger is slidably inserted. The pressurization chamber is defined between an inner wall of the housing and an outer wall of the plunger. 
     It has been required that a high-pressure fuel discharges large quantity of fuel in high pressure. A housing receiving high pressure force from a pressurization chamber should have enough thickness to endure the high pressure force. In the high-pressure pump shown in JP-2004-138062A, the housing is thick and heavy. Moreover, as the fuel pressure in the pressurization chamber becomes higher, higher sealing is required between the housing and the cylinder. If the cylinder is firmly engaged with the housing to enhance the sealing therebetween, it is likely that an outer wall surface of the cylinder may be damaged when inserted into the housing. This damage on the cylinder may deteriorate the sealing therebetween. 
     SUMMARY 
     It is an object of the present disclosure to provide a high-pressure pump having a configuration in which weight of a housing is reduced and a sealing between a cylinder and a housing is ensured. 
     A high-pressure pump includes a plunger, a cylinder and a housing. The plunger performs a reciprocating movement. The cylinder has a bottom portion, a cylindrical portion and a large-diameter cylindrical portion. Further, the cylinder has a cylinder inner wall on which the plunger reciprocatively slides. The cylinder defines pressurization chamber between the cylinder inner wall, a top surface of the plunger and an inner surface of the bottom portion. The cylinder has a suction port and a discharge port which communicate with the pressurization chamber. The housing has a small engaging hole with which outer walls of the bottom portion and the cylindrical portion are engaged by press-fit. The housing has a large engaging hole with which an outer wall of the large-diameter cylindrical portion is engaged by press-fit. 
     During a pressurization stroke of the above high-pressure pump, a cylinder inner wall and a plunger receive a fuel pressure from the pressurization chamber. Meanwhile, the housing does not receive the fuel pressure from the pressurization chamber. Moreover, the cylinder has the cylindrical portion and the large-diameter cylindrical portion. When inserting the large-diameter cylindrical portion into the large engaging hole, the cylindrical portion of the cylinder is not brought into contact with the housing. Thus, it is restricted that the cylindrical portion is damaged. The high liquid-tightness between the cylinder and the housing can be ensured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a cross-sectional view showing a high-pressure pump according to a first embodiment; 
         FIG. 2  is a cross-sectional view taken along a line II-II in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along a line in  FIG. 1 ; 
         FIGS. 4A, 4B and 4C  are schematic cross sectional views for explaining a method in which a cylinder is assembled to a lower housing of the high-pressure pump; 
         FIG. 5  is a cross-sectional view showing a high-pressure pump according to a second embodiment; 
         FIG. 6  is a cross-sectional view showing a high-pressure pump according to a third embodiment; 
         FIG. 7  is a cross-sectional view showing a high-pressure pump according to a fourth embodiment; 
         FIG. 8A  is a front view of a fixing member; 
         FIG. 8B  is a cross-sectional view taken along a line VIIIb-VIIIb in  FIG. 8A ; 
         FIG. 9  is a cross-sectional view showing a high-pressure pump according to a fifth embodiment; 
         FIG. 10A  is a front view of a fixing member; 
         FIG. 10B  is a cross-sectional view taken along a line Xb-Xb in  FIG. 10A ; 
         FIG. 11  is a front view of a fixing member according to another embodiment; and 
         FIG. 12  is a front view of a fixing member according to the other embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Multiple embodiments of the present invention will be described with reference to accompanying drawings. 
     First Embodiment 
       FIGS. 1 to 3  illustrate a high-pressure pump  1  according to a first embodiment. The high-pressure pump  1  supplies fuel pumped up from a fuel tank (not shown) by a low-pressure pump (not shown) to a pressurization chamber. Then, the fuel pressurized in the pressurization chamber is supplied to a fuel accumulator (not shown). The high pressure fuel in the fuel accumulator is injected into a combustion chamber through a fuel injector. The high-pressure pump  1  includes a body portion  10 , a fuel supply portion  30 , a plunger portion  50 , a fuel suction portion  70 , and a fuel-discharge-relief portion  90 . In the following description, the upper side of  FIG. 1  will be taken as “up”, “upward” or “upper,” and the low side of the  FIG. 1  will be taken as “down”, “downward” or “lower.” 
     The body portion  10  includes a lower housing  11 , a cylinder  13  and an upper housing  15 . The lower housing  11  includes: a cylindrical cylinder-holding-portion  111 ; an annular flange portion  112  protruded from the lower part of the cylinder-holding-portion  111 ; and a cylindrical engaging portion  113  which is engaged with an engine (not shown). The cylinder-holding-portion  111  has a large-diameter engaging hole  121  in which the cylinder  13  is press-inserted. 
     The flange portion  112  has a plurality of fuel paths  114  through which fuel flows. As shown in  FIG. 3 , the flange portion  112  has bolt-through holes  117  through which a bolt (not shown) is inserted so that the flange portion is fixed on the engine. 
     The cylinder-holding-portion  111  and the cylindrical engaging portion  113  are grinded in order to be engaged with the engine. The lower housing  11  is made from stainless steel. 
     The cylinder  13  has an inner wall surface  131  on which the plunger  51  slides. The inner wall surface  131  defines a pressurization chamber  14  in cooperation with a top surface  511  of the plunger  51 . When the plunger  51  slides up in the cylinder  13 , the fuel in the pressurization chamber  14  is pressurized. The cylinder  13  includes a suction port  141  and a discharge port  142  which communicate with the pressurization chamber  14 . The suction port  141  and the discharge port  142  are symmetrically arranged with respect to an axis of the plunger  51 . 
     The hardness of the cylinder  13  is enhanced by heat treatment, such as quenching, in order to suppress seizure and wear due to sliding of the plunger  51 . 
     As illustrated in  FIG. 3 , the upper housing  15  is substantially in a shape of a rectangular parallelepiped extending in a direction substantially orthogonal to an axis of the cylinder  13 . The upper housing  15  is formed independently from the lower housing  11 . The upper housing  15  has a press-insert hole  151  through which the cylinder  13  is inserted. The upper housing  15  and the cylinder  13  are fluid-tightly in contact with each other. Although the upper housing  15  and the lower housing  11  are in contact with each other in the present embodiment, it is not always required for them to be in contact with each other. 
     The upper housing  15  includes a stepped suction passage  152  and multiple communication passages  153 . The suction passage  152  penetrates the upper housing  15  in a direction opposite to the pressurization chamber  14  in such a manner as to communicate with the suction port  141 . The communication passages  153  orthogonally extend from the suction passage  152 . The suction passage  152  and the communication passages  153  communicate with the pressurization chamber  14  through the suction port  141 . 
     The upper housing  15  includes a stepped discharge passage  154  penetrating the upper housing  15  in a longitudinal direction thereof toward the opposite side to the pressurization chamber  14  with respect to the discharge port  142 . The discharge passage  154  communicates with the pressurization chamber  14  through the discharge port  142 . 
     The above press-insert hole  151 , the suction passage  152 , the communication passages  153  and the discharge passage  154  are formed by machining the upper housing  15 . As long as these hole and passages can be formed in the upper housing  15 , the upper housing  15  can be made thin to reduce its weight. 
     The fuel supply portion  30  will be described hereinafter. 
     The fuel supply portion  30  includes a cover  31 , a pulsation damper  33 , and a fuel inlet  35 . 
     The cover  31  is cup-shaped. The cover  31  accommodates a top portion of the cylinder  13  and the upper housing  15 . The cover  31  is comprised of a flat portion  311  and a cylindrical portion  312 . The flat portion  311  closes an upper portion of the cylindrical portion  312 . The cylindrical portion  312  is comprised of a first cylindrical portion  321 , an octagonal portion  322  and a second cylindrical portion  323 . 
     The first and the second cylindrical portion  321 ,  323  have a circular cross section. An inner diameter of the first cylindrical portion  321  is smaller than that of the second cylindrical portion  323 . 
     The octagonal portion  322  has an octagonal cross section. The octagonal portion  322  has four pairs of flat walls. A minimum inside measurement of the octagonal portion is larger than an inner diameter of the first cylindrical portion  321 . A maximum inside measurement of the octagonal portion is smaller than an inner diameter of the second cylindrical portion  323 . The first cylindrical portion  321  and the second cylindrical portion  323  are connected to the octagonal portion  322  through curved walls, which enhances a rigidity of the cover  31 . 
     The octagonal portion  322  has a first through-hole  325  and a second through-hole  326  which confront each other. A suction valve body  72  is inserted into the first through-hole  325 . A fuel-discharge-relief housing  91  is inserted into the second through-hole  326 . 
     Further, the octagonal portion  322  has a third through-hole  327  circumferentially adjacent to the second through-hole  326 , as shown in  FIG. 3 . A based portion of the fuel inlet  35  is inserted into the third through-hole  327 . The cover  31  is made of stainless steel. As long as a fuel gallery  32  can be defined inside of the cover  31 , the cover  31  can be made thin to reduce its weight. 
     The cover  31 , the flange portion  112 , the suction valve body  72 , the fuel-discharge-relief housing  91  and the fuel inlet  35  are respectively connected by welding. The cover  31  defines the fuel gallery  32  therein. The fuel gallery  32  communicates with the communication passages  153 . The fuel in the fuel gallery  32  is supplied to the pressurization chamber  14  through the communication passages  153 . 
     A pulsation damper  33  is arranged in the fuel gallery  32 . The pulsation damper  33  is configured by joining together the peripheral edge portions of two diaphragms  331 ,  332 . The pulsation damper  33  is sandwiched between an upper support member  341  and a lower support member  342  so as to be fixed on an inner wall of the first cylindrical portion  321 . A gas of predetermined pressure is sealed inside of the pulsation damper  33 . The pulsation damper  33  is elastically deformed according to change in the fuel pressure in the fuel gallery  32 , whereby a fuel pressure pulsation in the fuel gallery  32  is reduced. The cover  31  functions as a housing member for the pulsation damper  33 . 
     The plunger portion  50  will be described hereinafter. The plunger portion  50  includes a plunger  51 , an oil seal holder  52 , a spring seat  53 , a plunger spring  54 , and the like. The plunger  51  has a large-diameter portion  512  and a small-diameter portion  513 . The large-diameter portion  512  slides on the inner wall  131  of the cylinder  13 . The small-diameter portion  513  is inserted into an oil seal holder  52 . 
     The oil seal holder  52  is placed at an end of the cylinder  13  and includes: a base portion  521  positioned on the circumference of the small-diameter portion  512  of the plunger  51 ; and a press-fit portion  522  press-inserted into the engaging portion  113  of the lower housing  11 . 
     The base portion  521  has a ring-shaped seal  523  therein. The seal  523  is comprised of a ring located inside and an O-ring located outside. The thickness of a fuel oil film around the small-diameter portion  512  of the plunger  51  is adjusted by the seal  523  and the leakage of fuel to the engine is suppressed. The base portion  521  has an oil seal  525  at a tip end thereof. The thickness of an oil film around the small-diameter portion  512  of the plunger  51  is controlled by the oil seal  525  and oil leakage is suppressed. 
     The press-fit portion  522  is a portion cylindrically extending around the base portion  521 . The extending cylindrical portion has “U-shaped” portion. A recessed portion  526  corresponding to the press-fit portion  522  is formed in the lower housing  11 . The oil seal holder  52  is press-fit so that the press-fit portion  522  is press-inserted to the inner wall of the recessed portion  526 . 
     A spring seat  53  is provided at an end of the plunger  51 . The tip end of the plunger  51  is in contact with a tappet (not shown). The tappet has its outer surface abutted against a cam installed on a cam shaft and is reciprocatively moved in the axial direction according to the cam profile by the rotation of the cam shaft. 
     One end of the plunger spring  54  is engaged with the spring seat  53  and the other end of the plunger spring  54  is engaged with the press-fit portion  522 . As a result, the plunger spring  54  functions as a return spring for the plunger  51  and biases the plunger  51  so as to abut against the tappet. 
     With this configuration, the plunger  51  is reciprocatively moved according to the rotation of the cam shaft. As this time, the volumetric capacity of the pressurization chamber  14  is varied by the movement of the large-diameter portion  511  of the plunger  51 . 
     The fuel section portion  70  will be described hereinafter. 
     The fuel suction portion  70  includes a suction valve portion  71  and an electromagnetic driving unit  81 . The suction valve portion  71  includes a suction valve body  72 , a seat body  73 , a suction valve member  74 , a first spring holder  75 , a first spring  76 , and the like. The suction valve body  72  is joined to the upper housing  15  by press-fitting in the suction passage  152 . The suction valve body  72  defines a suction chamber  711  therein. The suction chamber  711  communicates with the fuel gallery  32  through the communication passages  153 . The cylindrical seat body  73  is placed in the suction chamber  711 . A valve seat  731  (refer to  FIG. 3 ) that can be abutted against the suction valve member  74  is formed on the seat body  73 . 
     The suction valve member  74  is arranged inside of the seat body  73  in such a manner as to reciprocatively move in the suction chamber  711 . When unseated from the valve seat  731 , the suction valve member  74  fluidly connects the suction chamber  711  and the pressurization chamber  14 . When seated on the valve seat  731 , the suction valve member  74  fluidly disconnects the suction chamber  711  and the pressurization chamber  14 . The first spring holder  75  is disposed in the suction chamber  711 . A first spring  76  is provided inside of the first spring holder  75  in such a manner as to bias the suction valve member  74  toward the valve seat  731 . 
     An electromagnetic actuator  81  is comprised of a fixed core  83 , a movable core  84  and a needle  86 . The movable core  84  is slidably arranged inside of the suction valve body  72 . One end of the needle  86  is connected to the movable core  84 . The needle  86  is reciprocatively supported by a second spring holder  852  fixed on the inner wall of the suction valve body  72 . A stopper  861  of the needle  86  can be brought into contact with the second spring holder  862 . A second spring  851  is provided inside of the second spring holder  852  in such a manner as to bias the needle  86  toward the suction valve member  74 . The second spring  851  biases the movable core  84  in the valve opening direction with a force larger than a force with which the first spring  76  biases the suction valve member  74  in the valve closing direction. 
     The fixed core  83  is arranged inside of a connector  891 . The connector  891  has a coil  87  and a terminal  892  for energizing the coil  87 . When the coil  87  is energized, a magnetic attraction force is generated between the fixed core  83  and the movable core  84 . The movable core  84  and the needle  86  are attracted to the fixed core  83 , so that the suction valve body  74  seats on the seat body  73  to close the suction passage. When the coil  87  is deenergized, the second spring  851  biases the movable core  84  and the needle  86  toward the pressurization chamber  14 , so that the suction passage is opened. 
     Then, the fuel-discharge-relief portion  90  will be described in detail, hereinafter. 
     The fuel-discharge-relief portion  90  includes a fuel-discharge-relief housing  91 , a valve body  92 , a discharge valve member  94  and a relief valve member  96 . The fuel-discharge-relief housing  91  is press-inserted into the discharge passage  154  formed in the upper housing  15 . The fuel-discharge-relief housing  91  accommodates the valve body  92 , the discharge valve member  94  and the relief valve member  96 . 
     The valve body  92  is cup-shaped and has an opening toward the pressurization chamber  14 . The valve body  92  has a discharge passage  95  and a relief passage  97 . These passages  95 ,  97  do not communicate with each other. The discharge passage  95  extends radially outwardly. Also, the relief passage  97  extends radially outwardly. 
     In the fuel-discharge-relief housing  91 , the discharge valve member  94  is disposed adjacent to a bottom wall of the valve body  92 . A discharge-valve-spring holder  945  holds a discharge valve spring  943 . The discharge valve spring  943  biases the discharge valve member  94 . 
     The relief valve member  96  is arranged in the fuel-discharge-relief housing  91 . The relief valve member  96  is biased toward the relief passage  97  by a relief valve spring  963 . 
     An operation of the high-pressure pump  1  will be described hereinafter. 
     (I) Suction Stroke 
     When the plunger  51  is moved down from the top dead center to the bottom dead center by rotation of the cam shaft, the volumetric capacity of the pressurization chamber  14  is increased and the fuel pressure in the pressurization chamber  14  is decreased. The discharge passage  95  is closed by the discharge valve member  94 . At this time, since the coil  87  has not been energized, the movable core  85  is moved toward the pressurization chamber  14  by the biasing force of the second spring  85 . The needle  86  biases the suction valve member  74  toward the first spring holder  75  to maintain the valve closed state. Thus, the fuel is suctioned into the pressurization chamber  14  from the suction chamber  711  through the suction port  141 . 
     (II) Metering Stroke 
     When the plunger  51  is moved up from the bottom dead center to the top dead center by rotation of the cam shaft, the volumetric capacity of the pressurization chamber  14  is reduced. The energization of the coil  87  is stopped until a predetermined time. The suction valve member  74  is in the open state. Thus, a part of the fuel suctioned into the pressurization chamber  14  in the suction stroke  121  is returned to the suction chamber  711 . When the energization of the coil  87  is started at the predetermined time in the process of the plunger  51  ascending, a magnetic attractive force is generated between the fixed core  83  and the movable core  84 . When this magnetic attractive force becomes larger than a resultant force of the biasing forces of the second spring  851  and the first spring  76 , the movable core  84  and the needle  86  are moved toward the fixed core  83  and the biasing force of the needle  86  against the suction valve member  74  is canceled. As a result, the suction valve member  74  is seated on the valve seat  731  formed on the seat body  73 . 
     (III) Pressurization Stroke 
     After the suction valve member  74  is closed, the fuel pressure in the pressurization chamber  14  is increased with ascent of the plunger  51 . When the fuel pressure force exerted on the discharge valve member  94  becomes larger than the following resultant force, the discharge valve member  94  is opened. The resultant force is a resultant of the pressure force of fuel in the fuel discharge port  99  and the biasing force of the discharge valve spring  943 . Thereby, high-pressure fuel pressurized in the pressurization chamber  14  is discharged from the fuel outlet  99  through the discharge port  142 . 
     As mentioned above, the high-pressure pump  1  repeats the suction stroke, the metering stroke, and pressurization stroke. The suctioned fuel is pressurized and discharged into the fuel accumulator through the fuel outlet  99 . 
     When the fuel pressure in the fuel accumulator is less than a predetermined value, the relief valve is closed. However, the fuel pressure in the fuel accumulator may be increased due to a malfunction. When the fuel pressure force exerted on the relief valve member  96  exceeds a specified value, the relief valve member  96  is moved toward the pressurization chamber  14  and the relief valve  95  is opened. The specified value corresponds to the sum of the force exerted on the relief valve member  96  and the biasing force of the relief valve spring  963 . As a result, the flow of fuel from the fuel discharge port  99  to the pressurization chamber  14  is permitted. 
     A configuration of the cylinder  13  will be described more in detail hereinafter. 
     The cylinder  13  is comprised of a flat portion (bottom portion)  132 , a cylindrical portion  133  and a large-diameter cylindrical portion  134 . An outer diameter “d 1 ” of the cylindrical portion  133  is smaller than an outer diameter “d 2 ” of the large-diameter cylindrical portion  134 . The large-diameter cylindrical portion  134  is press-inserted into a large engaging hole  121  of the cylinder-holding portion  111 . 
     An inner diameter of a small engaging hole  151  is smaller than that of the large engaging hole  121 . The cylindrical portion  133  is inserted into the small engaging hole  151 . The cylindrical portion  133  has the suction port  141  and the discharge port  142 . The suction port  141  communicates with the pressurizing chamber  14 . Also, the discharge port  142  communicates with the pressurizing chamber  14 . The suction port  141 , the discharge port  142 , the suction passage  152  and the discharge passage  154  define a fuel passage. 
     An outer diameter of the cylindrical portion  133 , which is denoted by an arrow “A” in  FIG. 2 , is constant. The cylindrical portion  133  is inserted into the small engaging hole  151  without any clearance therebetween. 
     The large-diameter cylindrical portion  134  has an annular protrusion  135  which is in contact with a cylinder-contacting portion  118  of the cylinder-holding portion  111 , whereby a movement of the cylinder  13  is restricted. 
     When assembling the cylinder  13  to the lower housing  11 , the flat portion  132  of the cylinder is inserted into the small engaging hole  151  of the upper housing  15 , as shown in  FIG. 4A . The large-diameter cylindrical portion  134  is inserted into the large engaging hole  121  until the annular protrusion  135  is brought into contact with the cylinder-contacting portion  118 , as shown in  FIGS. 4B and 4C . The flat portion  132  and the outer wall of the cylindrical portion  133  are not in contact with the lower housing  11 . 
     During the pressurization stroke, the cylinder inner wall  131  and the plunger  51  receive a fuel pressure from the pressurization chamber  14 . Meanwhile, the upper housing  15  does not receive the fuel pressure from the pressurization chamber  14 . Therefore, the upper housing  15  can be made thin. Further, since the housing is comprised of an upper housing  15  and the lower housing  11 , the shapes thereof can be made simplified. The weight of the housing can be reduced. 
     According to the present embodiment, the cylinder  13  is comprised of the flat portion  132 , the cylindrical portion  133  and the large-diameter cylindrical portion  134 . When inserting the large-diameter cylindrical portion  134  into the large engaging hole  121 , the flat portion  132  and the cylindrical portion  133  are not brought into contact with the lower housing  11 . Thus, it is restricted that the flat portion  132  and the cylindrical portion  133  are damaged. The high liquid-tightness between the flat portion  132 , the cylindrical portion  133  and the small engaging hole  151  can be ensured. 
     Further according to the present embodiment, the inner diameter of a large engaging hole  121  is greater than that of the small engaging hole  151 . Thus, when inserting the large-diameter cylindrical portion  134  into the large engaging hole  121 , it can be surely avoided that the inner surface of the large engaging hole  121  is brought into contact with the outer surface of the cylindrical portion  133 . 
     The upper housing  15  has the suction passage  152  communicating with the pressurization chamber  14  through the suction port  141  and the discharge passage  154  communicating with the pressurization chamber  14  through the discharge port  142 . Moreover, the outer diameter “d 1 ” of the cylindrical portion  133  is constant. Thus, the outer surface of the cylindrical portion  133  can be brought into close contact with the inner surface of the small engaging hole  151 . The sealing can be ensured between the upper housing  15  and the cylinder  13 . 
     Further, since the outer surface of the cylindrical portion  133  can be brought into close contact with the inner surface of the small engaging hole  151  without any clearance, it can be avoided that a dead volume is formed in the suction passage  152  and the discharge passage  154 . 
     The cylinder  13  has the annular protrusion  13  which is in contact with the cylinder-holding portion  111 , whereby a movement of the cylinder is restricted. 
     Second Embodiment 
     In the following second to fifth embodiments, the substantially same parts and the components as the first embodiment are indicated with the same reference numeral and the same description will not be reiterated. 
     Referring to  FIG. 5 , a high-pressure pump  2  according to a second embodiment will be described hereinafter. The lower housing  16  of the high-pressure pump  2  has a cylinder-holding portion  161  which is formed independently from the flange portion  162 . The cylinder-holding portion  161  includes the large engaging hole  121 . The cylinder-holding portion  161  is sandwiched between the flange portion  162  and the upper housing  15 . Since each component constituting the lower housing  16  has simple shape, the lower housing  16  can be easily manufactured. 
     Third Embodiment 
     Referring to  FIG. 6 , a high-pressure pump  3  according to a third embodiment will be described hereinafter. The high-pressure pump  3  has a cylinder  17  of which one opening end is closed by a lid member  172 . The inner wall surface of the cylinder can be easily grinded from its both opening ends. 
     Fourth Embodiment 
     Referring to  FIGS. 7, 8A and 8B , a high-pressure pump  4  according to a fourth embodiment will be described hereinafter. The cylinder  18  is provided with a fixing member  181  as a protruding portion. As shown in  FIGS. 8A and 8B , the fixing member  181  is a snap ring of which cross section is circle. Before providing the fixing member  181 , the outer surfaces of the cylindrical portion  133  and the large-diameter cylindrical portion  134  are grinded. 
     Fifth Embodiment 
     Referring to  FIGS. 9, 10A and 10B , a high-pressure pump  5  according to a fifth embodiment will be described hereinafter. The cylinder  19  is provided with a fixing member  191  as a protruding portion. As shown in  FIGS. 10A and 10B , the fixing member  191  is a snap ring of which cross section is square. Before providing the fixing member  191 , the outer surfaces of the cylindrical portion  133  and the large-diameter cylindrical portion  134  are grinded. 
     Other Embodiment 
     The high-pressure pump may be used as a fluid pump that discharges a fluid to a device other than an engine. As the protruding portion provided on the cylinder, a fixing member  201  shown in  FIG. 11  or a fixing member  211  shown in  FIG. 12  may be applied. 
     The cylinder and the cylinder-holding portion can be connected by shrinkage fitting or expansion fitting. Also, the cylinder and the upper housing can be connected by shrinkage fitting or expansion fitting. 
     The present invention is not limited to the embodiments mentioned above, and can be applied to various embodiments.