Patent Publication Number: US-11047353-B2

Title: High-pressure fuel supply pump

Description:
TECHNICAL FIELD 
     The present invention relates to a high-pressure fuel supply pump for an internal combustion engine, and more particularly, to a high-pressure fuel supply pump provided with a pressure pulsation reduction mechanism upstream of a pressurizing chamber for pressurizing fuel. 
     BACKGROUND ART 
     In high-pressure fuel supply pumps, a pressure pulsation reduction mechanism for reducing pressure pulsation generated in the pump is housed in a damper chamber formed in a low-pressure fuel passage. Among the high-pressure fuel supply pumps equipped with a pressure pulsation reduction mechanism, there is a known device that reduces the number of parts during the work of assembling a metal diaphragm damper (metal damper) as a pressure pulsation reduction mechanism into the low-pressure fuel passage, and reduces parts shortage and incorrect assembly (for example, see PTL 1). 
     The high-pressure fuel supply pump described in PTL 1 includes a metal damper in which two disc-shaped metal diaphragms are joined over the entire circumference and a sealed space is formed inside the joint, and gas is enclosed in the sealed space of the damper. Further, a pair of pressing members for applying a pressing force to both outer surfaces of the metal damper at a position radially inward of the joint is provided. The pair of pressing members are combined into a unit while interposing the metal damper. The unitized metal damper and the pair of pressing members (damper unit) are housed and held in a damper chamber formed by the pump body and a cover member attached to the pump body. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2009-264239 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the high-pressure fuel supply pump described in PTL 1, in order to position the pair of pressing members (damper unit) holding the metal damper, it is necessary to process a part of the pump body, so that the manufacturing cost increases accordingly. Further, in order to spread fuel to both surfaces of the metal damper, it is necessary to process a part of the pump body to form a flow path communicating with the damper chamber, thereby increasing the manufacturing cost. In addition, in order to spread fuel to both surfaces of the metal damper, it is necessary to secure the flow path communicating with the damper chamber by forming the cover member in a complicated shape (for example, a shape having a protruding portion having a missing portion), thereby increasing the manufacturing cost. 
     The invention has been made to solve the above problems, and an object thereof is to provide a high-pressure fuel supply pump capable of reducing a manufacturing cost of a part for holding a pressure pulsation reduction mechanism (damper). 
     Solution to Problem 
     The present application includes a plurality of means for solving the above-mentioned problems. For example, a pump body that includes a pressurizing chamber inside, a damper cover that forms a damper chamber on an upstream side of the pressurizing chamber together with the pump body, a damper that is disposed in the damper chamber and formed by laminating two diaphragms, and a first holding member that is disposed in the damper chamber and presses and holds the damper from one side are provided. The first holding member includes a first regulation portion for regulating movement of the damper in the radial direction, and a second regulation portion that regulates a radial movement of the first holding member in the damper chamber. A flow path that allows fuel in the damper chamber to circulate to both surfaces of the damper is formed at the position of the second regulation portion. 
     Advantageous Effects of Invention 
     According to the invention, the first holding member includes a first regulation portion that regulates the radial movement of the damper and a second regulation portion that regulates the radial movement of the damper itself, and a flow path for communicating with the damper chamber is formed at a position of the second regulation portion. Therefore, there is no need of positioning the first holding member and the damper with respect to the pump body and no need of processing for the flow path. Further, there is no need to secure a flow path depending on the shape of the damper cover. Therefore, the shapes of the parts of the pump body and the damper cover can be simplified, and the manufacturing cost of those parts can be reduced. 
     Objects, configurations, and effects besides the above description will be apparent through the explanation on the following embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram illustrating a fuel supply system for an internal combustion engine including a high-pressure fuel supply pump according to a first embodiment of the invention. 
         FIG. 2  is a longitudinal cross-sectional view illustrating the high-pressure fuel supply pump according to the first embodiment of the invention. 
         FIG. 3  is a lateral cross-sectional view of the high-pressure fuel supply pump according to the first embodiment of the invention illustrated in  FIG. 2 , as viewed from the direction of arrows III-III. 
         FIG. 4  is a longitudinal cross-sectional view illustrating a state in which the high-pressure fuel supply pump according to the first embodiment of the invention is cut along a plane (a plane different from  FIG. 1 ) including both axes of a plunger and a suction joint. 
         FIG. 5  is a longitudinal cross-sectional view illustrating an enlarged state of an electromagnetic suction valve mechanism that forms a part of the high-pressure fuel supply pump according to the first embodiment of the invention. 
         FIG. 6  is an enlarged perspective view illustrating a cut-away state of a metal damper and a holding structure thereof that form a part of the high-pressure fuel supply pump according to the first embodiment of the invention. 
         FIG. 7  is a perspective view illustrating a first holding member that forms a part of the high-pressure fuel supply pump according to the first embodiment of the invention illustrated in  FIG. 6 . 
         FIG. 8  is an explanatory view illustrating a step for assembling the metal damper in the high-pressure fuel supply pump according to the first embodiment of the invention. 
         FIG. 9  is a longitudinal cross-sectional view illustrating a high-pressure fuel supply pump according to a modification of the first embodiment of the invention. 
         FIG. 10  is a lateral cross-sectional view of a high-pressure fuel supply pump according to a modification of the first embodiment of the invention illustrated in  FIG. 9 , when viewed from the direction of arrows X-X. 
         FIG. 11  is a longitudinal cross-sectional view illustrating a state in which a high-pressure fuel supply pump according to a modification of the first embodiment of the invention is cut along a plane (a plane different from  FIG. 9 ) including both axes of a plunger and a discharge valve mechanism. 
         FIG. 12  is a longitudinal cross-sectional view illustrating a high-pressure fuel supply pump according to a second embodiment of the invention. 
         FIG. 13  is an enlarged perspective view illustrating a cut-away state of a metal damper and a holding structure thereof that form a part of a high-pressure fuel supply pump according to the second embodiment of the invention. 
         FIG. 14  is a perspective view illustrating a first holding member that forms a part of the high-pressure fuel supply pump according to the second embodiment of the invention illustrated in  FIG. 13 . 
         FIG. 15  is an explanatory view illustrating a step for assembling a metal damper in the high-pressure fuel supply pump according to the second embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the high-pressure fuel supply pump of the invention will be described with reference to the drawings. Further, the same symbol in the drawings represents the same portion. 
     First Embodiment 
     (Fuel Supply System) First, the configuration and operation of a fuel supply system for an internal combustion engine including the high-pressure fuel supply pump according to a first embodiment of the invention will be described with reference to  FIG. 1 .  FIG. 1  is a configuration diagram illustrating the fuel supply system for the internal combustion engine including the high-pressure fuel supply pump according to the first embodiment of the invention. 
     In  FIG. 1 , a portion surrounded by a broken line indicates a pump body  1  which is a main body of the high-pressure fuel supply pump. The mechanisms and components illustrated in the broken lines indicate that they are incorporated in the pump body  1 . 
     In  FIG. 1 , the fuel supply system includes a fuel tank  20  for storing fuel, a feed pump  21  for pumping up and sending out the fuel in the fuel tank  20 , and a high-pressure fuel supply pump for pressurizing and discharging a low-pressured fuel sent from the feed pump  21 , and a plurality of injectors  24  for injecting the high-pressure fuel pumped from the high-pressure fuel supply pump. The high-pressure fuel supply pump is connected to the feed pump  21  via a suction pipe  28 . The high-pressure fuel supply pump pumps fuel to the injector  24  via a common rail  23 . The injectors  24  are mounted on the common rail  23  according to the number of cylinders of the engine. A pressure sensor  26  is mounted on the common rail  23 . The pressure sensor  26  detects the pressure of the fuel discharged from the high-pressure fuel supply pump. 
     This high-pressure fuel supply pump is applied to a so-called direct injection engine system in which the injector  24  directly injects fuel into a cylinder of an engine as an internal combustion engine. The high-pressure fuel supply pump includes a pressurizing chamber  11  for pressurizing the fuel, an electromagnetic suction valve mechanism  300  as a variable capacity mechanism for adjusting the amount of fuel sucked into the pressurizing chamber  11 , a plunger  2  for pressurizing the fuel in the pressurizing chamber  11  by reciprocating motion, and a discharge valve mechanism  8  for discharging the fuel pressurized by the plunger. On the upstream side of the electromagnetic suction valve mechanism  300 , a metal damper  9  is provided as a pressure pulsation reduction mechanism for reducing the pressure pulsation generated in the high-pressure fuel supply pump from spreading to the suction pipe  28 . 
     The feed pump  21 , the electromagnetic suction valve mechanism  300 , and the injector  24  are controlled by a control signal output from an engine control unit (hereinafter, referred to as an ECU)  27 . The detection signal of the pressure sensor  26  is input to the ECU  27 . 
     The fuel in the fuel tank  20  is pumped by a feed pump  21  driven based on the control signal of the ECU  27 . This fuel is pressurized to an appropriate feed pressure by the feed pump  21  and sent to a low-pressure fuel suction port  10   a  of the high-pressure fuel supply pump through the suction pipe  28 . The fuel that has passed through the low-pressure fuel suction port  10   a  reaches a suction port  31   b  of the electromagnetic suction valve mechanism  300  via the metal damper  9  and a suction passage  10   d . The fuel flowing into the electromagnetic suction valve mechanism  300  passes through a suction valve  30  that opens and closes based on the control signal of the ECU  27 . The fuel that has passed through the suction valve  30  is sucked into the pressurizing chamber  11  during a downward stroke of the reciprocating plunger  2  which reciprocates, and is pressurized in the pressurizing chamber  11  during an upward stroke of the plunger  2 . The pressurized fuel is pumped to the common rail  23  via the discharge valve mechanism  8 . The high-pressure fuel in the common rail  23  is injected into the cylinder of the engine by the injector  24  driven based on the control signal of the ECU  27 . 
     The high-pressure fuel supply pump discharges a desired amount of fuel in response to the control signal from the ECU  27  to the electromagnetic suction valve mechanism  300 . 
     The high-pressure fuel supply pump illustrated in  FIG. 1  includes a pressure pulsation propagation prevention mechanism  100  upstream of the metal damper  9  (pressure pulsation reduction mechanism). The pressure pulsation propagation prevention mechanism  100  includes a valve seat (not illustrated), a valve  102  that comes into contact with and separates from the valve seat, a spring  103  that urges the valve  102  toward the valve seat, and a spring stopper (not illustrated) that limits the stroke of the valve  102 . Further, the pressure pulsation propagation prevention mechanism  100  is not illustrated in drawings other than  FIG. 1 . In addition, the high-pressure fuel supply pump may be configured without the pressure pulsation propagation prevention mechanism. 
     (High-Pressure Fuel Supply Pump) Next, the configuration of each part of the high-pressure fuel supply pump according to the first embodiment of the invention will be described with reference to  FIGS. 2 to 5 . 
       FIG. 2  is a longitudinal cross-sectional view illustrating the high-pressure fuel supply pump according to the first embodiment of the invention.  FIG. 3  is a lateral cross-sectional view of the high-pressure fuel supply pump according to the first embodiment of the invention illustrated in  FIG. 2 , as viewed from the direction of arrows III-III.  FIG. 4  is a longitudinal cross-sectional view illustrating a state in which the high-pressure fuel supply pump according to the first embodiment of the invention is cut along a plane (a plane different from  FIG. 1 ) including the both axes of a plunger and a suction joint. 
       FIG. 5  is a longitudinal cross-sectional view illustrating an enlarged state of the electromagnetic suction valve mechanism that forms a part of the high-pressure fuel supply pump according to the first embodiment of the invention. Further, in  FIG. 5 , a part of the connector is omitted, and the electromagnetic suction valve mechanism is illustrated in an open state. 
     In  FIG. 2 , the high-pressure fuel supply pump includes a pump body  1  having the pressurizing chamber  11  therein, the plunger  2  mounted on the pump body  1 , the electromagnetic suction valve mechanism  300 , the discharge valve mechanism  8  (see  FIG. 3 ), a relief valve mechanism  200 , and the metal damper  9  as a pressure pulsation reduction mechanism. The high-pressure fuel supply pump is in close contact with a pump mounting portion  80  of the engine using a mounting flange  1   e  (see  FIG. 3 ) provided at one end of the pump body  1 , and is fixed with a plurality of bolts (not illustrated). An O-ring  61  is fitted on the outer peripheral surface of the pump body fitted with the pump mounting portion  80 . The O-ring  61  seals between the pump mounting portion  80  and the pump body  1 , and prevents engine oil and the like from leaking out of the engine. 
     As illustrated in  FIGS. 2 and 4 , the pump body  1  is provided with a bottomed, stepped first accommodation hole  1   a . A cylinder  6  for guiding the reciprocating motion of the plunger  2  is press-fitted into the middle diameter portion of the first accommodation hole  1   a  on the outer peripheral side thereof, and forms a part of the pressurizing chamber  11  together with the pump body  1 . The cylinder  6  is pressed toward the pressurizing chamber  11  by a fixing portion if in which a part of the pump body  1  is deformed to the inner peripheral side, and an end surface  6   b  on the pressurizing chamber  11  side (the upper side in  FIGS. 2 and 4 ) is pressed against the wall surface of the first accommodation hole  1   a  of the pump body  1 , so that the fuel pressurized in the pressurizing chamber  11  is sealed not to leak to the low pressure side. 
     The plunger  2  has a large-diameter portion  2   a  that slides on the cylinder  6 , and a small-diameter portion  2   b  that extends from the large-diameter portion  2   a  to the side opposite to the pressurizing chamber  11 . A tappet  3  is provided on the tip side (the lower end side in  FIGS. 2 and 4 ) of the small-diameter portion  2   b  of the plunger  2 . The tappet  3  converts the rotational motion of a cam  81  (cam mechanism) attached to a cam shaft (not illustrated) of the engine into a linear reciprocating motion and transmits the motion to the plunger  2 . The plunger  2  is pressed against the tappet  3  by the urging force of the spring  4  via a retainer  15 . With this configuration, the plunger  2  can make a reciprocating motion according to the rotation motion of the cam  81 . 
     A seal holder  7  is press-fitted and fixed to the large-diameter portion of the first accommodation hole  1   a  of the pump body  1 . Inside the seal holder  7 , there is formed a sub-chamber  7   a  for storing the fuel leaking from the pressurizing chamber  11  via a sliding portion between the plunger  2  and the cylinder  6 . 
     A plunger seal  13  is provided on the small-diameter portion  2   b  of the plunger  2 . The plunger seal  13  is held at the inner peripheral end of the seal holder  7  on the cam  81  side so as to be able to slide on the outer peripheral surface of the small-diameter portion  2   b . The plunger seal  13  seals the fuel in the sub-chamber  7   a  and prevents the fuel from flowing into the engine when the plunger  2  reciprocates. At the same time, the lubricating oil (including the engine oil) in the engine is prevented from flowing into the pump body  1  from the engine side. 
     In addition, as illustrated in  FIGS. 3 and 4 , a suction joint  51  is attached to a side surface of the pump body  1 . The suction pipe  28  (see  FIG. 1 ) is connected to the suction joint  51 , and the fuel from the fuel tank  20  (see  FIG. 1 ) is supplied to the inside of the high-pressure fuel supply pump through the low-pressure fuel suction port  10   a  of the suction joint  51 . A suction filter  52  is attached downstream of the low-pressure fuel suction port  10   a . The suction filter  52  has a function of preventing foreign substances existing between the fuel tank  20  (see  FIG. 1 ) and the pump body  1  from being absorbed into the high-pressure fuel pump by the flow of the fuel. 
     As illustrated in  FIGS. 2 and 3 , the pump body  1  is provided with an electromagnetic suction valve mechanism  300  for supplying fuel to the pressurizing chamber  11 . As illustrated in  FIG. 5 , the structure of the electromagnetic suction valve mechanism  300  is roughly classified into a suction valve portion mainly configured by the suction valve  30 , a solenoid mechanism mainly configured by a rod  35  and an anchor  36 , and a coil portion mainly configured by an electromagnetic coil  43 . 
     The suction valve portion includes the suction valve  30 , a suction valve housing  31 , a suction valve stopper  32 , and a suction valve urging spring  33 . The suction valve housing  31  includes, for example, a cylindrical valve housing portion  31   h  that houses the suction valve  30  on one side (the right side in  FIG. 5 ), and an annular suction valve seat portion  31   a  that protrudes on the inner peripheral side of the valve housing portion  31   h . The suction valve housing  31  is formed integrally with a rod guide  37  described later. The suction valve housing  31  is provided with a plurality of suction ports  31   b  radially communicating with the suction passage (low-pressure fuel flow path)  10   d . The suction valve stopper  32  is press-fitted and fixed to the valve housing portion  31   h . The suction valve  30  closes by abutting on the suction valve seat portion  31   a , and abuts on the suction valve stopper  32  when the valve is open. The suction valve urging spring  33  is disposed between the suction valve  30  and the suction valve stopper  32 , and urges the suction valve  30  in the valve closing direction. 
     The solenoid mechanism includes the rod  35  and the anchor  36  that are movable parts, the rod guide  37 , an outer core  38 , and a fixed core  39  that are fixing portion, a rod urging spring  40 , and an anchor portion urging spring  41 . 
     The rod  35  is slidably held in the axial direction on the inner peripheral side of the rod guide  37 . The rod  35  has a tip end on one side (the right side in  FIG. 5 ) that can be brought into contact with and separated from the suction valve  30 , and has a rod flange  35   a  at an end on the other side (the left side in  FIG. 5 ). The inner peripheral side of the anchor portion  36  slidably holds the rod  35 . In other words, the rod  35  and the anchor portion  36  are configured to be slidable in the axial direction within a geographically restricted range. The anchor portion  36  has a through hole  36   a  that penetrates in the axial direction, thereby minimizing the restriction of the movement of the anchor portion  36  due to the pressure difference between both sides in the axial direction. 
     The rod guide  37  has a cylindrical central bearing portion  37   b , and guides the reciprocating operation of the rod  35 . The rod guide  37  is provided with a through hole  37   a  penetrating in the axial direction, so that the movement of the anchor portion  36  is not hindered by the pressure in the chamber accommodating the anchor portion  36 . The rod guide  37  is press-fitted on the inner peripheral side of one side (the right side in  FIG. 5 ) of the outer core  38  in the axial direction. The anchor portion  36  is slidably disposed on the inner peripheral side on the other side in the axial direction (the left side in  FIG. 5 ). The fixed core  39  is disposed such that the end surface on one side (the right side in  FIG. 5 ) faces the end surface on the rod flange  35   a  side of the anchor portion  36 . One end surface of the fixed core  39  and the end surface of the anchor portion  36  facing the one end surface form a magnetic attraction surface S which a magnetic attractive force acts therebetween. When the suction valves  30  are in the open state, they face each other via a magnetic gap. 
     The rod urging spring  40  is disposed between the fixed core  39  and the rod flange  35   a . The rod urging spring  40  applies an urging force in the valve opening direction of the suction valve  30 , and is set so as to be an urging force for keeping the suction valve  30  open when the electromagnetic coil  43  is not energized. The anchor portion urging spring  41  is disposed such that one end thereof is inserted into the central bearing portion  37   b  of the rod guide  37 , and applies an urging force to the anchor part  36  toward the rod flange  35   a.    
     The coil portion includes a first yoke  42 , the electromagnetic coil  43 , a second yoke  44 , a bobbin  45 , and a connector  47  having a terminal  46  (see  FIG. 2 ). The electromagnetic coil  43  is formed by winding a copper wire around the outer periphery of the bobbin  45 , and is assembled on the outer peripheral side of the fixed core  39  and the outer core  38  in a state surrounded by the first yoke  42  and the second yoke  44 . The first yoke  42  has its hole fixed to the outer peripheral side of the outer core  38 . The second yoke  44  is configured such that the outer peripheral side is fixed to the inner peripheral side of the first yoke  42 , and the inner peripheral side is close to the outer periphery of the fixed core  39  with a clearance. 
     In the above configuration, the outer core  38 , the first yoke  42 , the second yoke  44 , the fixed core  39 , and the anchor  36  form a magnetic circuit. In this magnetic circuit, when a current is applied to the electromagnetic coil  43 , a magnetic attractive force is generated between the fixed core  39  and the anchor portion  36 , and a force for attracting each other is generated. 
     In addition, on the outlet side of the pressurizing chamber  11  of the pump body  1 , the discharge valve mechanism  8  is provided as illustrated in  FIG. 3 . The discharge valve mechanism  8  is configured by a discharge valve seat  8   a , a discharge valve  8   b  which comes into contact with or separates from the discharge valve seat  8   a , a discharge valve spring  8   c  which urges the discharge valve  8   b  toward the discharge valve seat  8   a , and a discharge valve stopper  8   d  which determines a stroke (moving distance) of the discharge valve  8   b . The discharge valve stopper  8   d  is held by a plug  8   e . By connecting the plug  8   e  to the pump body  1  by welding at a contact portion  8   f , leakage of fuel to the outside is blocked. A discharge valve chamber  12   a  is formed on the secondary side of the discharge valve  8   b.    
     In a state where there is no difference in fuel pressure between the pressurizing chamber  11  and the discharge valve chamber  12   a , the discharge valve  8   b  is tightly pressed to the discharge valve seat  8   a  by the urging force of the discharge valve spring  8   c , and enters a closed state. When the fuel pressure of the pressurizing chamber  11  becomes larger than that of the discharge valve chamber  12   a , first the discharge valve  8   b  is opened against the urging force of the discharge valve spring  8   c . When the discharge valve  8   b  is opened, the high-pressure fuel in the pressurizing chamber  11  is discharged to the common rail  23  (see  FIG. 1 ) through the discharge valve chamber  12   a , a fuel discharge passage  12   b  described below, and a fuel discharge port  12  described below. 
     When being opened, the discharge valve  8   b  comes into contact with the discharge valve stopper  8   d , and the stroke is restricted. Therefore, the stroke of the discharge valve  8   b  is appropriately determined by the discharge valve stopper  8   d . With this configuration, it is possible to prevent that the stroke becomes so large to delay the close of the discharge valve  8   b  and thus the fuel discharged at a high pressure to the discharge valve chamber  12   a  flows back into the pressurizing chamber  11 . Therefore, deterioration in efficiency of the high-pressure fuel supply pump can be suppressed. In addition, when the discharge valve  8   b  repeatedly opens and closes, the discharge valve  8   b  is guided by the outer peripheral surface of the discharge valve stopper  8   d  so as to move only in the stroke direction. With the above configuration, the discharge valve mechanism  8  functions as a check valve that restricts the direction of fuel flow. 
     Further, the pressurizing chamber  11  is configured by the pump body  1  (pump housing), the electromagnetic suction valve mechanism  300 , the plunger  2 , the cylinder  6 , and the discharge valve mechanism  8 . 
     In addition, as illustrated in  FIGS. 2 and 3 , a discharge joint  60  is attached to the pump body  1  at a position opposite to the electromagnetic suction valve mechanism  300 . 
     The discharge joint  60  has the fuel discharge port  12  formed therein, and the fuel discharge port  12  communicates with the discharge valve chamber  12   a  via the fuel discharge passage  12   b . The discharge joint  60  is configured to house the relief valve mechanism  200  therein. 
     The relief valve mechanism  200  includes a relief body  201 , a relief valve seat  202 , a relief valve  203 , a relief valve holder  204 , and a relief spring  205 . After the relief spring  205 , the relief valve holder  204 , and the relief valve  203  are inserted in this order in the relief body  201 , the relief valve seat  202  is press-fitted and fixed. One end of the relief spring  205  is in contact with the relief body  201 , and the other end is in contact with the relief valve holder  204 . The relief valve  203  shuts off the fuel by the urging force of the relief spring  204  acting via the relief valve holder  204  and being pressed by the relief valve seat  202 . The valve opening pressure of the relief valve  203  is determined by the urging force of the relief spring  205 . The relief valve mechanism  200  communicates with the pressurizing chamber  11  via a relief passage  210 . 
     In addition, as illustrated in  FIGS. 2 and 4 , a concave portion  1   p  is provided on the tip end side (the upper end side in  FIGS. 2 and 4 ) of the pump body  1 . A cylindrical-bottomed damper cover  14  (cup shape) is fixed to the pump body  1  by welding so as to cover the concave portion  1   p . A low-pressure fuel chamber  10  is formed by the concave portion  1   p  of the pump body  1  and the damper cover  14 . The low-pressure fuel chamber  10  communicates with the low-pressure fuel suction port  10   a  and also communicates with the suction port  31   b  of the electromagnetic suction valve mechanism  300  via the suction passage  10   d . That is, the low-pressure fuel chamber is formed upstream of the pressurizing chamber  11 . In addition, the low-pressure fuel chamber  10  communicates with the sub-chamber  7   a  via a fuel passage  10   e.    
     In the low-pressure fuel chamber  10 , the metal damper  9  is disposed. That is, the pump body  1  and the damper cover  14  form a damper chamber that houses the metal damper  9 . The metal damper  9  is held in the low-pressure fuel chamber (damper chamber)  10  while being interposed between a first holding member  9   a  and a second holding member  9   b.    
     The first holding member  9   a  is disposed between the damper cover  14  and the metal damper  9  in the low-pressure fuel chamber (damper chamber)  10 , and presses and holds the metal damper  9  from one side (the upper side in  FIGS. 2 and 4 ). The second holding member  9   b  is disposed in the low-pressure fuel chamber (damper chamber)  10  on the opposite side of the first holding member  9   a  across the metal damper  9  (between the pump body  1  and the metal damper  9 ), and presses and holds the metal damper  9  from the other side (the lower side in  FIGS. 2 and 4 ). 
     (Details of Metal Damper and Holding Structure of Metal Damper) Next, details of the configuration and structure of the metal damper and components for holding the metal damper will be described with reference to  FIGS. 6 and 7 .  FIG. 6  is an enlarged perspective view illustrating a cut-away state of a metal damper and a holding structure thereof that form a part of the high-pressure fuel supply pump according to the first embodiment of the invention.  FIG. 7  is a perspective view illustrating a first holding member that forms a part of the high-pressure fuel supply pump according to the first embodiment of the invention illustrated in  FIG. 6 . 
     In  FIG. 6 , for example, the metal damper  9  is formed by welding all over the periphery of two corrugated disk-shaped metal diaphragms at their peripheral edges, and sealing an inert gas such as argon to an internal space formed between the two laminated diaphragms. In other words, the metal damper  9  is configured by a substantially circular main body portion  91  having an internal space in which an inert gas is sealed, a welding portion  92  formed in a peripheral portion, and an annular and flat plate portion  93  extending between the main body portion  91  and the welding portion  92 . The flat plate portion  93  is a portion where the planar portions of the two metal diaphragms overlap, and is located radially inward of the welding portion  92 . The metal damper  9  reduces pressure pulsation by increasing or decreasing the volume of the internal space of the main body portion  91  due to pressure acting on both surfaces. 
     The concave portion  1   p  of the pump body  1  is formed in a truncated cone shape whose diameter on the opening side is enlarged. At the end of the pump body  1  on the concave portion  1   p  side, an outer peripheral surface  1   r  is formed in a cylindrical shape, and the end surface  1   s  is formed in an annular shape. In other words, an annular protrusion  1   v  is formed at the end of the pump body  1  on the concave portion  1   p  side. The end of the pump body  1  on the side of the concave portion  1   p  and the concave portion  1   p  have a rotationally symmetric shape. 
     The damper cover  14 , for example, is formed in a stepped cylindrical shape (cup shape) with one side closed and is formed in a rotationally symmetric shape, and is configured to accommodate three components: the first holding member  9   a , the metal damper  9 , and the second holding member  9   b . Specifically, the damper cover  14  is configured by a cylindrical small-diameter cylindrical portion  141 , a circular closing portion  142  that closes one side of the small-diameter cylindrical portion  141 , a cylindrical large-diameter cylindrical portion  143  on the opening side, and a cylindrical medium-diameter cylindrical portion  144  located between the small-diameter cylindrical portion  141  and the large-diameter cylindrical portion  143 . The damper cover  14  is formed, for example, by pressing a steel plate. The large-diameter cylindrical portion  143  of the damper cover  14  is press-fitted into the outer peripheral surface  1   r  at the end of the pump body  1  on the concave portion  1   p  side and fixed by welding. By providing a plurality of steps in the cylindrical portion of the damper cover  14 , the tip end (small-diameter cylindrical portion  141 ) can be reduced in size with respect to the portion (large-diameter cylindrical portion  143 ) attached to the pump body  1 , and this is advantageous when the installation space for the high-pressure fuel supply pump is narrow. 
     The first holding member  9   a  is, for example, an elastic body having a bottomed cylindrical shape (cup shape) and rotationally symmetrical shape as illustrated in  FIGS. 6 and 7 . Specifically, the first holding member  9   a  includes a contact portion  111  that abuts on the damper cover  14 , an annular pressing portion  112  that presses the flat plate portion  93  of the metal damper  9  over the entire circumference, a cylindrical first side wall surface portion  113  which connects the contact portion  111  and the pressing portion  112  and increases its diameter from the contact portion  111  toward the pressing portion  112 , an annular curved portion  114  that protrudes radially outward from the entire periphery of the pressing portion  112  to be bent to receive a part of the welding portion  92  of the metal damper  9 , and a cylindrical enclosing portion  115  that extends in the axial direction from the curved portion  114  and surrounds the peripheral edge of the metal damper  9 . The first holding member  9   a  is formed, for example, by pressing a steel plate. 
     The contact portion  111  is formed in a circular and planar shape. A first communication hole  111   a  is provided at the center of the contact portion  111 . In this embodiment, a configuration in which the first communication hole  111   a  is not provided is also possible. However, the first communication hole  111   a  is a structure necessary when applied to a modification of the first embodiment described later, and is provided for the purpose of sharing components. Further, the details of the first communication hole  111   a  will be described in the description of the modification. 
     In the first side wall surface portion  113 , a plurality of second communication holes  113   a  are provided at intervals in the circumferential direction. The second communication hole  113   a  is a communication passage that communicates with a space (a space surrounded by the first holding member  9   a  and the metal damper  9 ) formed radially inside the cylindrical first side wall surface portion  113  and a space (a space surrounded by the first holding member  9   a  and the damper cover  14 ) formed outside in the radial direction of the first side wall surface portion  113 , and functions as a flow path that allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the main body portion  91  of the metal damper  9 . 
     The enclosing portion  115  is set so that the inner diameter thereof has a gap (first gap) within a predetermined range than the outer diameter of the metal damper  9 , and functions as a first regulation portion that regulates movement of the metal damper  9  in the radial direction. The first gap between the inner peripheral surface of the enclosing portion  115  and the peripheral edge of the metal damper  9  is set in a range where the pressing portion  112  of the first holding member  9   a  does not abut on the welding portion  92  of the metal damper  9  even if the metal damper  9  is radially displaced from the first holding member  9   a  by the first gap. 
     A plurality of projections  116  projecting outward in the radial direction are provided at the opening-side end of the enclosing portion  115  at intervals in the circumferential direction. The plurality of projections  116  are configured to face the inner peripheral surface of the medium-diameter cylindrical portion  144  of the damper cover  14  with a gap (second gap) within a predetermined range, and functions as a second regulation portion that regulates movement of the first holding member  9   a  in the radial direction in the low-pressure fuel chamber (damper chamber)  10 . In other words, the plurality of projections  116  have a function of centering the first holding member  9   a  in the damper cover  14 . In order to sufficiently exhibit the centering function, it is desirable to provide six or more projections  116 . The second gap between the tip of each projection  116  and the inner peripheral surface of the medium-diameter cylindrical portion  144  of the damper cover  14  is set in a range where the pressing portion  112  of the first holding member  9   a  does not abut on the welding portion  92  of the metal damper  9  even if the first holding member  9   a  is displaced in the radial direction with respect to the damper cover  14  by the second gap. 
     Each projection  116  is formed, for example, by cutting and raising, and a space P extending in the circumferential direction is formed between adjacent projections  116 . This space P forms a communication path for communicating the space on one side (upper side in  FIG. 6 ) of the metal damper  9  with the space on the other side (lower side in  FIG. 6 ), and functions as a flow path that allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the main body portion  91  of the metal damper  9 . The length of each of the projections  116  can be set to be short as long as cutting and raising is possible. Even in a case where the length of the projections  116  is made as short as possible, the space P as a flow path can be always secured between the adjacent projections  116 , so that the first holding member  9   a  can be minimized in the radial direction. 
     The second holding member  9   b  is, for example, an elastic body having a cylindrical and rotationally symmetric shape as illustrated in  FIG. 6  (see also  FIG. 8  described later). Specifically, the second holding member  9   b  is configured by a cylindrical second side wall surface portion  121  whose one side expands in diameter, and an annular pressing portion  122  bent radially inward from an opening end on the small diameter side of the second side wall surface portion  121 , and an annular flange portion  123  protruding radially outward from an opening end on the large diameter side of the second side wall surface portion  121 . The second holding member  9   b  is formed, for example, by pressing a steel plate. 
     In the second side wall surface portion  121 , a plurality of third communication holes  121   a  are provided at intervals in the circumferential direction. The third communication hole  121   a  is a communication passage that communicates with a space (a space surrounded by the second holding member  9   b , the metal damper  9 , and the concave portion  1   p  of the pump body  1 ) formed radially inside the cylindrical second side wall surface portion  121  and a space (a space surrounded by the second holding member  9   b  and the damper cover  14 ) formed outside in the radial direction of the second side wall surface portion  121 , and functions as a flow path that allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the main body portion  91  of the metal damper  9 . 
     The pressing portion  122  is configured to press the flat plate portion  93  of the metal damper  9  over the entire circumference, and is formed to have substantially the same diameter as the pressing portion  122  of the first holding member  9   a . That is, the pressing portion  122  of the second holding member  9   b  and the pressing portion  112  of the first holding member  9   a  are configured to interpose both surfaces of the flat plate portion  93  of the metal damper  9  in the same manner. 
     The flange portion  123  is configured to abut on the end surface is of the pump body  1  on the side of the concave portion  1   p . In addition, the flange portion  123  is configured to face the inner peripheral surface of the large-diameter cylindrical portion  143  of the damper cover  14  with a gap (third gap) within a predetermined range, and functions as a third regulation portion that regulates movement of the second holding member  9   b  in the low-pressure fuel chamber (damper chamber)  10  in the radial direction. In other words, the flange portion  123  has a function of centering the second holding member  9   b  inside the damper cover  14 . The third gap between the outer peripheral edge of the flange portion  123  and the inner peripheral surface of the large-diameter cylindrical portion  143  of the damper cover  14  is set in a range where the pressing portion  122  of the second holding member  9   b  does not abut on the welding portion  92  of the metal damper  9  even if the second holding member  9   b  is displaced in the radial direction with respect to the damper cover  14  by the third gap. 
     As described above, in the holding structure of the metal damper  9  according to this embodiment, the space P between the second communication hole  113   a  of the first side wall surface portion  113  of the first holding member  9   a  and the adjacent projection  116  of the first holding member  9   a , and the third communication hole  121   a  of the second side wall surface portion  121  of the second holding member  9   b  serve as a flow path which allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the metal damper  9 . Therefore, it is not necessary to provide the flow path in the pump body  1 , and the shape of the pump body  1  and the concave portion  1   p  of the pump body  1  can be simplified to a rotationally symmetric shape. In this case, the processing of the flow path for the pump body  1  is unnecessary, and the processing of the pump body  1  and the concave portion  1   p  of the pump body  1  becomes easy. Therefore, the manufacturing cost of the high-pressure fuel supply pump can be reduced. 
     In addition, in the holding structure of the metal damper  9  according to this embodiment, as described above, the second communication hole  113   a  of the first holding member  9   a , the space P between the adjacent projections  116 , and the third communication hole  121   a  of the second holding member  9   b  serve as a flow path that allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the metal damper  9 . For this reason, the damper cover  14  does not need to have a complicated shape for securing the flow path, and can be simplified to a rotationally symmetric shape. 
     In this case, the processing of the damper cover  14  becomes easy, and the manufacturing cost of the high-pressure fuel supply pump can be reduced. 
     In addition, in the holding structure of the metal damper  9  according to this embodiment, the radial positioning (centering) of the first holding member  9   a , the metal damper  9 , and the second holding member  9   b  in the damper cover  14 , is performed by the enclosing portion  115  of the first holding member  9   a , the projection  116 , and the flange portion  123  of the second holding member  9   b.    
     Therefore, it is not necessary to provide the pump body with a structure for positioning (centering) the first holding member  9   a , the metal damper  9 , and the second holding member  9   b . Therefore, it is possible to avoid complication of the shape of the pump body  1 , and to simplify the shape of the pump body  1  and the concave portion  1   p  of the pump body  1  to a rotationally symmetric shape. In this case, the processing of the pump body  1  becomes easy, and the manufacturing cost of the high-pressure fuel supply pump can be reduced. 
     (Step for Assembling Metal Damper) Next, the step for assembling the metal damper in the high-pressure fuel supply pump according to the first embodiment of the invention will be described with reference to  FIG. 8 .  FIG. 8  is an explanatory view illustrating the step for assembling the metal damper in the high-pressure fuel supply pump according to the first embodiment of the invention. 
     First, as illustrated in  FIG. 8 , the damper cover  14  is disposed such that the closing portion  142  is on the lower side and the opening is on the upper side. 
     Next, the first holding member  9   a  is inserted into the damper cover  14  with the contact portion  111  facing downward, and placed on the closing portion  142  of the damper cover  14 . At this time, the first holding member  9   a  is positioned in the damper cover  14  in the radial direction by the plurality of projections  116  of the first holding member  9   a . That is, the centering of the first holding member  9   a  in the damper cover  14  is performed only by inserting the first holding member  9   a  into the damper cover  14 . In this embodiment, since the second gap is provided between the projection  116  of the first holding member  9   a  and the inner peripheral surface of the medium-diameter cylindrical portion  144  of the damper cover  14 , the first holding member  9   a  is easily assembled to the damper cover  14 . 
     Next, the metal damper  9  is placed on the pressing portion  112  of the first holding member  9   a  in the damper cover  14 . At this time, the metal damper  9  is positioned in the radial direction in the first holding member  9   a  by the enclosing portion  115  of the first holding member  9   a.    
     In this case, since the first holding member  9   a  is centered in the damper cover  14 , the metal damper  9  is simply placed on the first holding member  9   a , so that the metal damper  9  is centered in the damper cover  14 . In this embodiment, since the first gap is provided between the inner peripheral surface of the enclosing portion  115  of the first holding member  9   a  and the peripheral edge of the metal damper  9 , the first gap is easily assembled to the first holding member  9   a  of the metal damper  9 . 
     Subsequently, the second holding member  9   b  is inserted into the damper cover  14  with the pressing portion  122  facing downward, and placed on the flat plate portion  93  of the metal damper  9 . At this time, the second holding member  9   b  is positioned in the damper cover  14  in the radial direction by its own flange portion  123 . That is, the centering of the second holding member  9   b  in the damper cover  14  is performed only by inserting the second holding member  9   b  into the damper cover  14 . In this embodiment, since the third gap is provided between the outer edge of the flange portion  123  of the second holding member  9   b  and the inner peripheral surface of the large-diameter cylindrical portion  143  of the damper cover  14 , the second holding member  9   b  is easily assembled to the damper cover  14 . 
     Finally, the end of the pump body  1  (see  FIG. 6 ) on the concave portion  1   p  side is press-fitted into the large-diameter cylindrical portion  143  of the damper cover  14 , and the end surface is of the pump body  1  on the concave portion  1   p  side presses the flange portion  123  of the second holding member  9   b . In this state, the damper cover  14  is fixed to the pump body  1  by welding. 
     In this case, the flange portion  123  and the second side wall surface portion  121  of the second holding member  9   b  are in a state of being elastically bent. In addition, the contact portion  111  of the first holding member  9   a  is pressed by the closing portion  142  of the damper cover  14 , and the second side wall surface portion  121  of the first holding member  9   a  is elastically bent. As a result, a spring reaction force is generated in the first holding member  9   a  and the second holding member  9   b , and the metal damper  9  is reliably held in the low-pressure fuel chamber (damper chamber)  10  by the urging force. 
     As described above, in the step for assembling the metal damper  9  in this embodiment, the first holding member  9   a , the metal damper  9 , and the second holding member  9   b  can be positioned (centered) in the damper cover  14  only by sequentially inserting the first holding member  9   a , the metal damper  9 , and the second holding member  9   b  into the damper cover  14 . Therefore, the step for positioning each of the components  9 ,  9   a , and  9   b  is not required. 
     In addition, since it is not necessary to unitize the three components of the first holding member  9   a , the metal damper  9 , and the second holding member  9   b  and assemble them into the damper cover  14 , a subassembly step for unitizing the components  9 ,  9   a , and  9   b  is not necessary. 
     Further, since the damper cover  14 , the first holding member  9   a , the metal damper  9 , and the second holding member  9   b  are each formed in a rotationally symmetric shape, only the axial direction of the component needs to be considered when assembling. 
     Therefore, it is possible to improve productivity and reduce costs by simplifying the assembly process. 
     (Operation of High-Pressure Fuel Supply Pump) Next, the operation of the high-pressure fuel supply pump will be described with reference to  FIGS. 2 to 6 . 
     When the plunger  2  moves toward the cam  81  and enters a suction stroke state while the cam  81  rotates illustrated in  FIG. 2 , the volume of the pressurizing chamber  11  is increased, and the fuel pressure in the pressurizing chamber  11  is lowered. If the fuel pressure in the pressurizing chamber  11  is lowered than the pressure of the suction port  31   b  in this stroke, the suction valve  30  enters an open state. Therefore, as illustrated in  FIG. 5 , the fuel passes through an opening  30   e  of the suction valve  30 , and flows to the pressurizing chamber  11 . 
     After the end of the suction stroke, the plunger  2  moves up to the compression stroke. Here, the electromagnetic coil  43  is kept in the non-energized state, and no magnetic urging force is generated. In this case, the suction valve  30  is maintained in the open state by the urging force of the rod urging spring  40 . The volume of the pressurizing chamber  11  is reduced according to the compression movement of the plunger  2 . However, in a state where the suction valve  30  is opened, the fuel once sucked into the pressurizing chamber  11  returns to the suction passage  10   d  through the opening  30   e  of the suction valve  30 . Therefore, the pressure of the pressurizing chamber  11  is not increased. This stroke is called a returning stroke. 
     In this state, when the control signal of the ECU  27  (see  FIG. 1 ) is applied to the electromagnetic suction valve mechanism  300 , a current flows through the electromagnetic coil  43  via the terminal  46  (see  FIG. 2 ). Then, the magnetic attractive force operates between the fixed core  39  and the anchor  36 , so that the magnetic urging force overcomes the urging force of the rod urging spring  40  to make the rod  35  move in a direction away from the suction valve  30 . Therefore, the suction valve  30  is closed by the urging force of the suction valve urging spring  33  and the fluid force caused by the fuel flowing into the suction passage  10   d . By closing the suction valve  30 , the fuel pressure in the pressurizing chamber  11  rises in accordance with the rising motion of the plunger  2 , and when the pressure becomes equal to or higher than the pressure of the fuel discharge port  12 , the discharge valve  8   b  of the discharge valve mechanism  8  illustrated in  FIG. 3  opens. Thereby, the high-pressure fuel in the pressurizing chamber  11  is discharged from the fuel discharge port  12  through the discharge valve chamber  12   a  and the fuel discharge passage  12   b , and is supplied to the common rail  23  (see  FIG. 1 ). This stroke is called a discharge stroke. 
     In other words, the compression stroke of the plunger  2  illustrated in  FIG. 2  (the upward stroke from the lower start point to the upper start point) includes the returning stroke and the discharge stroke. In addition, the flow rate of the discharging high-pressure fuel can be controlled by controlling timing for energizing the electromagnetic coil  43  of the electromagnetic suction valve mechanism  300 . If the timing for energizing the electromagnetic coil  43  is set to be advanced, the ratio of the returning stroke in the compression stroke becomes small, and the ratio of the discharge stroke becomes large. In other words, the fuel returning to the suction passage  10   d  becomes less, and on the other hand the discharged high-pressure fuel becomes large. On the other hand, if the energization timing is delayed, the ratio of the returning stroke during the compression stroke increases, and the ratio of the discharge stroke decreases. In other words, the fuel returning to the suction passage  10   d  becomes large, and on the other hand the discharged high-pressure fuel becomes less. The timing for energizing the electromagnetic coil  43  is controlled by a command from the ECU  27 . 
     As described above, it is possible to control the amount of high-pressure fuel to be discharged as much as the engine requires by controlling the timing for energizing the electromagnetic coil  43 . 
     In the above-described pump displacement control, in a case where the fuel once flowing into the pressurizing chamber is returned to the suction passage  10   d  again through the suction valve  30  in the open state (in the case of the returning stroke), the fuel flows back from the pressurizing chamber  11  to the suction passage  10   d . Therefore, pressure pulsation occurs in the low-pressure fuel chamber  10 . The pressure pulsation is transmitted to the surface of the metal damper  9  disposed in the low-pressure fuel chamber (damper chamber)  10  illustrated in  FIG. 6  on the pump body  1  side (the lower side in  FIG. 6 ), and transmitted to the surface of the metal damper  9  on the damper cover  14  side (the upper side in  FIG. 6 ) sequentially through the third communication hole  121   a  of the second holding member  9   b , the space P between the adjacent projections  116  of the first holding member  9   a , and the second communication hole  113   a  of the first holding member  9   a . This pressure pulsation is reduced by the expansion and contraction of the main body portion  91  of the metal damper  9 . 
     In addition, as illustrated in  FIG. 4 , the volume of the sub-chamber  7   a  increases or decreases due to the reciprocating motion of the plunger  2  having the large-diameter portion  2   a  and the small-diameter portion  2   b . When the plunger  2  moves down, the volume of the sub-chamber  7   a  decreases, and the fuel flows from the sub-chamber  7   a  to the low-pressure fuel chamber via the fuel passage  10   e . On the other hand, when ascending, the volume of the sub-chamber  7   a  increases, and the fuel flows from the low-pressure fuel chamber  10  to the sub-chamber  7   a  via the fuel passage  10   e . This makes it possible to reduce the fuel flow into and out of the pump during the suction stroke or the returning stroke of the pump, and reduce pressure pulsation generated inside the pump. 
     Further, in a case where the pressure of the fuel discharge port  12  becomes larger than the set pressure of the relief valve mechanism  200  due to a failure of the electromagnetic suction valve mechanism  300  illustrated in  FIG. 3 , the relief valve  203  is opened, and abnormally high-pressure fuel is released to the pressurizing chamber  11  through the relief passage  210 . 
     As described above, according to the high-pressure fuel supply pump according to the first embodiment of the invention, the first holding member  9   a  includes the enclosing portion (first regulation portion)  115  that regulates movement in the radial direction of the metal damper  9  (damper) and the projection (second regulation portion)  116  that regulates movement in the radial direction of the projection  116 . The flow path (space P) communicating with the inside of the low-pressure fuel chamber (damper chamber)  10  is formed at the position of the projection (second regulation portion)  116 . Therefore, the pump body  1  is not required to position the first holding member  9   a  and the metal damper  9  and to process the flow path. Further, there is no need to secure the flow path by the shape of the damper cover  14 . Therefore, the shapes of the components of the pump body  1  and the damper cover  14  can be simplified, and the manufacturing cost of the components  1  and  14  can be reduced. 
     In addition, the projection (second regulation portion)  116  of the first holding member  9   a  positions the first holding member  9   a  in the radial direction within the damper cover  14 , and the enclosing portion (first regulation portion)  115  of the first holding member  9   a  positions the metal damper  9  in the radial direction within the damper cover  14 . Therefore, the components  9  and  9   a  are easily centered during assembly. 
     Further, according to this embodiment, the first holding member  9   a  is configured such that the second gap is formed between the projection  116  of the first holding member  9   a  and the inner peripheral surface of the damper cover  14 . Therefore, the holding member  9   a  can be easily assembled into the damper cover  14 . 
     In addition, according to this embodiment, the second gap between the projection  116  of the first holding member  9   a  and the inner peripheral surface of the damper cover  14  is set in a range where the pressing portion  112  of the first holding member  9   a  does not abut on the welding portion  92  of the metal damper  9  even if the first holding member  9   a  moves in the radial direction by the second gap. Therefore, even if the first holding member  9   a  is configured to have a clearance fit with the damper cover  14 , the first holding member  9   a  does not press the welding portion  92  of the metal damper  9 . Therefore, it is possible to prevent the pressing force of the first holding member  9   a  from acting on the welding portion  92 , thereby preventing the welding portion  92  from being damaged such as a crack. 
     In addition, according to this embodiment, the metal damper  9  is interposed and held by the first holding member  9   a  disposed on one side of the metal damper  9  and the second holding member  9   b  disposed on the other side. Therefore, the metal damper  9  can be firmly held in the low-pressure fuel chamber (damper chamber)  10 , and the metal damper  9  can be prevented from being directly held by the pump body  1  and the damper cover  14 . 
     Further, according to this embodiment, since the second holding member  9   b  has the flange portion (third regulation portion)  123  for regulating the movement of the second holding member  9   b  in the radial direction, the second holding member  9   b  is easily positioned in the radial direction within the damper cover  14 . 
     In addition, according to this embodiment, the second holding member  9   b  is configured such that the third gap is formed between the flange portion  123  of the second holding member  9   b  and the inner peripheral surface of the damper cover  14 . Therefore, the second holding member  9   b  can be easily assembled into the damper cover  14 . 
     Further, according to this embodiment, the third gap between the flange portion  123  of the second holding member  9   b  and the inner peripheral surface of the damper cover  14  is set in a range where the second holding member  9   b  does not abut on the welding portion  92  of the metal damper  9  even if the second holding member  9   b  moves in the radial direction by the third gap. Therefore, even if the second holding member  9   b  is configured to have a clearance fit with the damper cover  14 , the second holding member  9   b  does not press the welding portion  92  of the metal damper  9 . Therefore, it is possible to prevent the pressing force of the second holding member  9   b  from acting on the welding portion  92 , thereby preventing the welding portion from being damaged such as a crack. 
     In addition, according to this embodiment, in the cylindrical first side wall surface portion  113  of the first holding member  9   a , the second communication hole  113   a  is provided to communicate a space formed radially inward of the first side wall surface portion  113  in the low-pressure fuel chamber  10  and a space formed radially outward. Therefore, it is possible to reliably secure a flow path that allows the fuel in the low-pressure fuel chamber  10  to flow on both surfaces of the metal damper  9 . 
     In addition, according to this embodiment, since the enclosing portion  115  as the first regulation portion of the first holding member  9   a  is configured to surround the entire peripheral portion of the metal damper  9 , it is possible to make the metal damper  9  of the first regulation portion securely centered. 
     In addition, according to this embodiment, since the first holding member  9   a  is configured as an elastic body that abuts against the damper cover  14  during assembly, the metal damper  9  can securely be held in the low-pressure fuel chamber (damper chamber)  10  by the spring reaction force of the first holding member  9   a.    
     Similarly, according to this embodiment, since the second holding member  9   b  is configured as an elastic body that abuts on the pump body  1  during assembly and is elastically deformed, the metal damper  9  can be securely held in the low-pressure fuel chamber (damper chamber)  10  by the spring reaction force of the second holding member  9   b.    
     In addition, according to this embodiment, since the contact portion  111  of the first holding member  9   a  that abuts on the closing portion  142  of the damper cover  14  is formed in a planar shape, the pressing force of the damper cover  14  acting on the contact portion  111  is dispersed, and it is possible to suppress the occurrence of locally large stress in the contact portion  111 . 
     Modification of First Embodiment 
     Next, a high-pressure fuel supply pump according to a modification of the first embodiment of the invention will be described with reference to  FIGS. 9 to 11 .  FIG. 9  is a longitudinal cross-sectional view illustrating the high-pressure fuel supply pump according to the modification of the first embodiment of the invention.  FIG. 10  is a lateral cross-sectional view of the high-pressure fuel supply pump according to the modification of the first embodiment of the invention illustrated in  FIG. 9 , when viewed from the direction of arrows X-X.  FIG. 11  is a longitudinal cross-sectional view illustrating a state in which the high-pressure fuel supply pump according to the modification of the first embodiment of the invention is cut along a plane (a plane different from  FIG. 9 ) including the both axes of the plunger and the discharge valve mechanism. Further, in  FIGS. 9 to 11 , the same reference numerals as those illustrated in  FIG. 1  to are the same portions, and a detailed description thereof will be omitted. 
     The high-pressure fuel supply pump according to the modification of the first embodiment of the invention illustrated in  FIGS. 9 to 11  is different from the high-pressure fuel supply pump according to the first embodiment in that the suction joint  51  is mounted to the side surface of the pump body  1  (see  FIGS. 3 and 4 ), and the suction joint  51  is mounted to a damper cover  14 A. 
     Specifically, as illustrated in  FIGS. 9 and 11 , the damper cover  14 A includes a mounting cylinder portion  145  at the center of the closing portion  142 . The mounting cylinder portion  145  is formed so as to match with the axis X of the suction joint  51  and the axis of the damper cover  14 A. The mounting cylinder portion  145  is formed by, for example, press working. The suction joint  51  is fixed to the inside of the mounting cylinder portion  145  by press-fitting welding. Inside the suction joint  51 , the suction filter  52  is disposed. 
     The low-pressure fuel suction port  10   a  of the suction joint  51  communicates with the first communication hole  111   a  (see also  FIG. 7 ) of the first holding member  9   a  via the mounting cylinder portion  145 . The first communication hole  111   a  of the first holding member  9   a  is formed to be larger in diameter than the flow path diameter of the suction pipe  28  (see  FIG. 1 ) attached to the suction joint  51 . In addition, the diameter of the first communication hole  111   a  is set such that the first holding member  9   a  can maintain elastic deformation when the first holding member  9   a  is deformed by the damper cover  14 A abutting on the contact portion  111  of the first holding member  9   a  (see also  FIG. 6  and  FIG. 8 ). 
     In the high-pressure fuel supply pump according to this modification, as illustrated in  FIG. 9 , the fuel flowing from the low-pressure fuel suction port  10   a  of the suction joint  51  flows to the low-pressure fuel chamber  10  via the first communication hole  111   a  of the first holding member  9   a . The fuel in the low-pressure fuel chamber  10  further flows into the suction port  31   b  of the electromagnetic suction valve mechanism  300  through the second communication hole  113   a  of the first holding member  9   a  (see  FIG. 6 ), the space P between the projections  116  of the first holding member  9   a  (see  FIG. 6 ), and the third communication hole  121   a  of the second holding member  9   b  (see  FIG. 6 ). In the electromagnetic suction valve mechanism  300 , the capacitance control of the pump is performed as in the first embodiment. 
     According to the high-pressure fuel supply pump according to the modification of the above-described first embodiment of the invention, the same effects as those of the above-described first embodiment can be obtained. 
     In addition, according to this embodiment, since the suction joint  51  is configured to be attached to the damper cover  14 A, there is no need to process the pump body  1  for mounting the suction joint  51  as illustrated in  FIG. 10  compared with the case of the first embodiment in which the suction joint  51  is attached to the pump body  1  (see  FIG. 3 ). In this case, it is necessary to form a mounting cylinder portion  142   a  by, for example, pressing the damper cover  14 A. However, the pressing of the damper cover  14 A can reduce the manufacturing cost more than the processing of the pump body  1 . 
     Further, according to this embodiment, the diameter of the first communication hole  111   a  of the first holding member  9   a  is set to be larger than the flow path of the suction pipe (see  FIG. 1 ) attached to the suction joint  51 . Therefore, when the fuel flows into the low-pressure fuel chamber  10  from the low-pressure fuel suction port  10   a , the pressure loss of the fuel due to the first communication hole  111   a  of the first holding member  9   a  can be suppressed. 
     In addition, according to this embodiment, the diameter of the first communication hole  111   a  of the first holding member  9   a  is set to a size that the first holding member  9   a  can maintain the elastic deformation when the damper cover  14  abuts on the contact portion  111  of the first holding member  9   a . Therefore, plastic deformation of the first holding member  9   a  is prevented, and the metal damper  9  can be securely held in the low-pressure fuel chamber (damper chamber)  10  by the spring reaction force of the first holding member  9   a.    
     Second Embodiment 
     Next, a configuration of a high-pressure fuel supply pump according to a second embodiment of the invention will be described with reference to  FIGS. 12 to 14 .  FIG. 12  is a longitudinal cross-sectional view illustrating the high-pressure fuel supply pump according to the second embodiment of the invention.  FIG. 13  is an enlarged perspective view illustrating a cut-away state of a metal damper and a holding structure thereof that form a part of the high-pressure fuel supply pump according to the second embodiment of the invention.  FIG. 14  is a perspective view illustrating a first holding member that forms a part of the high-pressure fuel supply pump according to the second embodiment of the invention illustrated in  FIG. 13 . Further, in  FIGS. 12 to 14 , the same reference numerals as those illustrated in  FIGS. 1 to 11  are the same parts, and a detailed description thereof will be omitted. 
     The high-pressure fuel supply pump according to the second embodiment of the invention illustrated in  FIG. 12  to is different from the high-pressure fuel supply pump according to the first embodiment in that a damper cover  14 B is formed in a stepless cylindrical shape of which one side is closed, and a first holding member  9   c  has an annular flange  117  instead of the projection  116  (see  FIG. 7 ) of the first holding member  9   a  of the first embodiment. 
     Specifically, as illustrated in  FIGS. 12 and 13 , the damper cover  14 B is formed in a cylindrical, rotationally symmetric shape with one side closed, and three components of the first holding member  9   c , the metal damper  9 , and the second holding member  9   b  can be accommodated. That is, the damper cover  14 B is configured by the cylindrical portion  147  and a circular closing portion  148  that closes one side of the cylindrical portion  147 , and is formed by, for example, pressing a steel plate. 
     As illustrated in  FIGS. 13 and 14 , the first holding member  9   c  is an elastic body having a bottomed cylindrical shape (cup shape) and a rotationally symmetric shape, and is formed by, for example, pressing a steel plate. As in the first embodiment, the first holding member  9   c  includes the circular contact portion  111  having the first communication hole  111   a , an annular pressing portion  112 , a cylindrical first side wall surface portion  113  connecting a contact portion  111  and a pressing portion  112 , the annular curved portion  114  protruding from the pressing portion  112 , and a cylindrical enclosing portion  115  as a first regulation portion extending from the curved portion  114 . 
     An annular flange  117  protruding radially outward is provided at an opening-side end of the enclosing portion  115 . The flange  117  is configured to face the inner peripheral surface of the cylindrical portion  147  of the damper cover  14 B with a gap within a predetermined range (fourth gap), and functions as a second regulation portion that regulates movement of the first holding member  9   c  in the radial direction in the low-pressure fuel chamber (damper chamber)  10 . In other words, the flange  117  has a function of centering the first holding member  9   c  inside the damper cover  14 B. The fourth gap between the outer edge of the flange  117  and the inner peripheral surface of the cylindrical portion  147  of the damper cover  14 B is set in a range where the pressing portion  112  of the first holding member  9   c  does not to abut on the welding portion  92  of the metal damper  9  even if the first holding member  9   c  is shifted in the radial direction with respect to the damper cover  14 B by the fourth gap. 
     A plurality of fourth communication holes  117   a  are provided in the flange  117  at intervals in the circumferential direction. The fourth communication hole  117   a  forms a communication path for communicating the space on one side (upper side in  FIG. 13 ) of the metal damper  9  with the space on the other side (lower side in  FIG. 13 ) of the metal damper  9 , and functions as a flow path that allows the fuel in the low-pressure fuel chamber (damper chamber)  10  to circulate to both surfaces of the main body portion  91  of the metal damper  9 . The width (the length in the radial direction) of the flange  117  is set in a range where the fourth communication hole  117   a  can be formed. 
     (Step for Assembling Metal Damper) Next, the step for assembling the metal damper in the high-pressure fuel supply pump according to the second embodiment of the invention will be described with reference to  FIG. 15 .  FIG. 15  is an explanatory view illustrating a step of assembling a metal damper in the high-pressure fuel supply pump according to the second embodiment of the invention. 
     As in the case of the first embodiment, the damper cover  14 B is disposed such that the closing portion  148  is on the lower side and the opening is on the upper side, as illustrated in  FIG. 15 . 
     Next, the first holding member  9   c  is inserted into the damper cover  14 B with the contact portion  111  facing downward, and placed on the closing portion  148  of the damper cover  14 B. 
     At this time, the first holding member  9   c  is positioned in the radial direction within the damper cover  14 B by its own flange  117 . That is, the centering of the first holding member  9   c  in the damper cover  14 B is performed only by inserting the first holding member  9   c  into the damper cover  14 B. In this embodiment, since the fourth gap is provided between the flange  117  of the first holding member  9   c  and the inner peripheral surface of the cylindrical portion  147  of the damper cover  14 B, the first holding member  9   c  is easily assembled to the damper cover  14 B. 
     Next, the metal damper  9  is placed on the pressing portion  112  of the first holding member  9   c  in the damper cover  14 B. At this time, the metal damper  9  is positioned in the radial direction in the first holding member  9   c  by the enclosing portion  115  of the first holding member  9   c , as in the case of the first embodiment, and is centered in the damper cover  14 B. 
     Subsequently, the second holding member  9   b  is inserted into the damper cover  14 B with the pressing portion  122  facing downward, and is placed on the flat plate portion  93  of the metal damper  9 . At this time, similarly to the case of the first embodiment, the second holding member  9   b  is radially positioned in the damper cover  14 B by its own flange portion  123 , and is centered in the damper cover  14 B. 
     Finally, the end of the pump body  1  (see  FIG. 13 ) on the side of the concave portion  1   p  is press-fitted into the cylindrical portion  147  of the damper cover  14 B, and the end surface is of the pump body  1  on the side of the concave portion  1   p  is fixed by welding while pressing the flange portion  123  of the second holding member  9   b . Thus, as in the case of the first embodiment, a spring reaction force is generated in the first holding member  9   c  and the second holding member  9   b , and the urging force causes the metal damper  9  to be securely held inside the low-pressure fuel chamber (damper chamber)  10 . 
     As described above, in the step for assembling the metal damper  9  in this embodiment, similarly to the case of the first embodiment, the first holding member  9   c , the metal damper  9 , and the second holding member  9   b  can be positioned (centered) in the damper cover  14 B only by sequentially inserting the first holding member  9   c , the metal damper  9 , and the second holding member  9   b  into the damper cover  14 B. Therefore, the positioning step of the components  9 ,  9   b , and  9   c  is unnecessary. 
     In addition, since it is not necessary to assemble the three components of the first holding member  9   c , the metal damper  9 , and the second holding member  9   b  and assemble them into the damper cover  14 B, the subassembly step for unitizing the components  9 ,  9   b , and  9   c  is necessary. 
     Further, since the damper cover  14 B, the first holding member  9   c , the metal damper  9 , and the second holding member  9   b  are each formed in a rotationally symmetric shape, only the axial direction of the component needs to be considered when assembling. 
     Therefore, it is possible to improve productivity and reduce costs by simplifying the assembly process. 
     According to the high-pressure fuel supply pump according to the above-described second embodiment of the invention, the same effects as those of the above-described first embodiment can be obtained. 
     In addition, according to this embodiment, since the damper cover  14 B is formed in a bottomed cylindrical shape with no step, the step for forming a step can be omitted, and the manufacturing cost of the damper cover  14 B can be reduced compared with the configuration of the stepped bottomed cylindrical shape as in the damper cover  14  of the first embodiment (see  FIG. 9 ). 
     Further, according to this embodiment, since the annular flange  117  is used as the second regulation portion of the first holding member  9   c , the risk of deformation is small, and the function of the second regulation portion can be reliably exhibited compared with the projection  116  used as the second regulation portion of the first embodiment (see  FIG. 7 ). 
     Further, the invention is not limited to the above embodiments, but various modifications may be contained. The above-described embodiments have been described in detail for clear understating of the invention, and are not necessarily limited to those having all the described configurations. Some of the configurations of a certain embodiment may be replaced with the configurations of the other embodiments, and the configurations of the other embodiments may be added to the configurations of a certain embodiment. In addition, some of the configurations of each embodiment may be omitted, replaced with other configurations, and added to other configurations. 
     REFERENCE SIGNS LIST 
     
         
           1  pump body 
           14 ,  14 A,  14 B damper cover 
           9  metal damper (damper) 
           9   a ,  9   c  first holding member 
           9   b  second holding member 
           10  low-pressure fuel chamber (damper chamber) 
           11  pressurizing chamber 
           28  suction pipe 
           92  welding portion 
           111  contact portion 
           111   a  first communication hole (communication hole) 
           112  pressing portion 
           113  first side wall surface portion (side wall surface portion) 
           113   a  second communication hole (communication hole) 
           115  enclosing portion (first regulation portion) 
           116  projection (second regulation portion) 
           117  flange (second regulation portion) 
           117   a  fourth communication hole (flow path) 
           123  flange portion (third regulation portion) 
         P space (flow path)