Patent Abstract:
To reduce collision noise created by the operation of an electromagnetic suction valve provided on a high pressure fuel supply pump. In the present invention, in order to achieve the above object, the mass of a member which collides by magnetic attractive force is reduced to reduce the noise to be generated. The thus configured present invention provides the following advantageous effects. The noise generated when a core and an anchor collide with each other by magnetic attractive force depends on the magnitude of the kinetic energy of a moving element. The kinetic energy to be consumed in the collision is only the kinetic energy of the anchor. The kinetic energy of a rod, being absorbed by a spring, does not contribute to the noise; thus, the energy when the anchor and the core collide with each other can be reduced, whereby the noise to be created can be reduced.

Full Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a high pressure fuel supply pump for pumping high pressure fuel to an fuel injection valve of an internal combustion engine, in particular, to a high pressure fuel supply pump equipped with an electromagnetic suction valve for adjusting the volume of discharged fuel. 
       BACKGROUND ART 
       [0002]    In a high pressure fuel supply pump equipped with a conventional electromagnetic suction valve described in JP 2002-48033 A, the electromagnetic suction valve is in a valve-opened state where the suction valve is opened by a biasing force of a spring when an electromagnetic coil is not supplied with current. When the electromagnetic coil is supplied with current, the suction valve is closed by magnetic attractive force generated in the electromagnetic suction valve. Accordingly, the opening-closing motion of the suction valve can be controlled by existence and non-existence of the current in the electromagnetic coil; consequently, the supply amount of high pressure fuel can be controlled. 
       CITATION LIST 
     Patent Literature 
       [0003]    PTL 1: JP 2002-48033 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    When the electromagnetic coil is supplied with current, magnetic attractive force is generated between a core and an anchor, and the anchor, which is a moving element, starts to move in a valve-closing direction of the suction valve. There has been a problem that the anchor stops when colliding with the core, and a large noise is created due to impact at that time. In particular, the noise has been a problem in an idling operation state of a vehicle in which quietness is required. 
         [0005]    An object of the present invention is to reduce collision noise generated in an electromagnetic suction valve in a high pressure fuel supply pump. 
       Solution to Problem 
       [0006]    In the present invention, in order to achieve the object, the mass of a member which makes a collision by magnetic attractive force is made small to reduce the noise to be generated. For this purpose, a configuration is made in which a moving element which moves by magnetic attractive force is divided into two parts (an anchor and a rod), and even if the anchor collides with the core and the anchor stops moving, the rod continues to move. Preferably, kinetic energy of the rod is absorbed by a biasing force of a spring which biases the suction valve in a valve-opening direction. 
       Advantageous Effects of Invention 
       [0007]    The present invention configured in this way provides the following advantageous effects. 
         [0008]    The noise created when the core and the anchor collides with each other by magnetic attractive force depends on the magnitude of the kinetic energy of the moving element. The kinetic energy consumed by the collision is only the kinetic energy of the anchor. The kinetic energy of the rod is absorbed by the biasing force of the spring and does not contribute to the noise. Therefore, the energy at the collision between the anchor and the core can be made small, and the noise to be generated can be accordingly reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is an example of a diagram of a fuel supply system including a high pressure fuel supply pump according to a first embodiment in which the present invention is practiced. 
           [0010]      FIG. 2  is a vertical cross sectional view of a high pressure fuel supply pump according to the first embodiment in which the present invention is practiced. 
           [0011]      FIG. 3  is another vertical cross sectional view of a high pressure fuel supply pump according to the first embodiment in which the present invention is practiced. 
           [0012]      FIG. 4  is an enlarged cross-sectional view of an electromagnetic suction valve in a high pressure fuel supply pump according to the first embodiment in which the present invention is practiced, and, shows a state where the electromagnetic suction valve is in a valve-opened state. 
           [0013]      FIG. 5  is an enlarged cross-sectional view of the electromagnetic suction valve in the high pressure fuel supply pump according to the first embodiment in which the present invention is practiced, and shows a state where the electromagnetic suction valve is in a valve-closed state. 
           [0014]      FIG. 6  shows a state before the electromagnetic suction valve of the high pressure fuel supply pump according to the first embodiment in which the present invention is practiced is assembled into a pump main body. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Based on an embodiment shown in the drawings, the present invention will be described in detail below. 
       First Embodiment  
       [0016]    Based on  FIG. 1  to  FIG. 6 , a configuration of a high pressure fuel supply pump of an embodiment of the present invention will be described. 
         [0017]    In  FIG. 1 , the part surrounded by the broken line shows a pump housing  1  of the high pressure fuel supply pump, and shows that mechanisms and components illustrated in the broken line are integrally assembled into the pump housing  1  of the high pressure fuel supply pump. 
         [0018]    Fuel in a fuel tank  20  is pumped up by a feed pump  21  based on a signal from an engine control unit  27  (hereinafter, referred to as ECU), is pressurized to an appropriate feed pressure, and is fed to a low pressure fuel suction opening  10   a  of the high pressure fuel supply pump through a suction pipe  28 . 
         [0019]    In  FIG. 2 , on the top of the pump housing  1  is fixed a damper cover  14 . On the damper cover  14  is provided a suction joint  101 , which forms a low pressure fuel suction opening  10   a . The fuel having passed through the low pressure fuel suction opening  10   a  passes through a suction filter  102  fixed inside the suction joint  101 , and reaches a suction port  30   a  of an electromagnetic suction valve  30  further through a low pressure fuel flow path  10   b , a pressure pulsation reduction mechanism  9 , and a low pressure fuel flow path  10   c.    
         [0020]    The suction filter  102  in the suction joint  101  has a function of preventing the foreign matters which reside from the fuel tank  20  to the low pressure fuel suction opening  10   a  from being taken into the high pressure fuel supply pump by the flow of the fuel. 
         [0021]    In the pump housing  1 , there is formed a convex part  1 A as a compression chamber  11  at the center, and in an suction port  30   a  at the entrance of the compression chamber  11  there is provided an electromagnetic suction valve  30 . Inside the electromagnetic suction valve  30  is provided a moving element  31  configured with an anchor  31   b  and a rod  31   a . In the electromagnetic suction valve  30 , when an electromagnetic coil  52  is not supplied with current, the moving element  31  is moved leftward in the drawing as shown in  FIG. 4  by the difference between the biasing force of an anchor spring  34  and the biasing force of an suction valve spring  38 , and an suction valve  39  is in contact with an suction valve holder  35  to be in a valve-opened state. Thus, the electromagnetic suction valve  30  communicates the suction port  30   a  and the compression chamber  11  when the electromagnetic coil  52  is not supplied with current. 
         [0022]    The outer periphery of a cylinder  6  is held by a cylindrical fitting part  7   a  of a cylinder holder  7 . With a thread  7   g  cut in the outer periphery of the cylinder holder  7  being screwed into a thread  1   b  cut in the pump housing  1 , the cylinder  6  is fixed to the pump housing  1 . In addition, a plunger seal  13  is held on the lower end of the cylinder holder  7  by a seat holder  16  which is press-fit and fixed to an inner periphery cylindrical surface  7   c  of the cylinder holder  7  and by the cylinder holder  7 . Here, the axis of the plunger seal  13  is held coaxially with the axis of the cylindrical fitting part  7   a  by the inner periphery cylindrical surface  7   c  of the cylinder holder  7 . A plunger  2  and the plunger seal  13  are disposed slidably in contact with each other at the lower end, in the drawing, of the cylinder  6 . 
         [0023]    This arrangement prevents the fuel in the circular low pressure seal chamber  10   f  from flowing into the side of the tappet  3 , in other words, into the inside of the engine. At the same time, this arrangement prevent lubricant oil (including engine oil) for lubricating sliding parts in an engine housing from flowing into the inside of the pump housing  1 . 
         [0024]    Further, on the cylinder holder  7  is provided an outer peripheral cylindrical surface  7   b , and in the outer peripheral cylindrical surface  7   b  is provided a groove  7   d , in which an O-ring  61  is to be fit. The O-ring  61 , together with the inner wall of a fitting hole  70  in the engine side and the groove  7   d  in the cylinder holder  7 , secludes the cam side and the outside of the engine from each other and thus prevents the engine oil from leaking outside. 
         [0025]    The cylinder  6  has a pressure-bonding part  6   a  intersecting the direction of a reciprocating motion of the plunger  2 , and the pressure-bonding part  6   a  is in pressure contact with a pressure-bonding surface  1   a  of the pump housing  1 . The pressure contact is made by the force of a tightened screw. The compression chamber  11  is formed by this pressure contact, and the tightening torque of the screw must be controlled so that the fuel does not leak outside the compression chamber  11  through the pressure-bonding part even if the fuel in the compression chamber  11  is pressurized to a high pressure. 
         [0026]    In addition, in order to keep the sliding distance between the plunger  2  and the cylinder  6  in an appropriate range, a configuration is made such that the cylinder  6  is inserted deep into the compression chamber  11 . There is provided a clearance  1 B between the outer periphery of the cylinder  6  and the inner periphery of the pump housing  1  on the side of the compression chamber  11  from the pressure-bonding part  6   a  of the cylinder  6 . Since the outer periphery of the cylinder  6  is held by the cylindrical fitting part  7   a  of the cylinder holder  7 , it can be possible to prevent the outer periphery of the cylinder  6  and the inner periphery of the pump housing  1  from being in contact with each other by providing the clearance  1 B. 
         [0027]    In the manner described above, the cylinder  6  holds the plunger  2 , which performs a back-and-forth motion in the compression chamber  11 , slidably in the direction of the back-and-forth motion. 
         [0028]    At the lower end of the plunger  2 , a retainer  15  is fixed to the plunger  2  by fitting. The retainer  15  converts the rotational motion of a cam  5  into an up-and-down motion and transfers the motion to the plunger  2 , and the plunger  2  is pressed through the intermediary of the retainer  15  by a spring  4  against the inner surface of the bottom of a tappet  3 . This arrangement enables the plunger  2  to move up and down with the rotational motion of the cam  5 . 
         [0029]    In the case that the cam  5  is a three point cam (having three points of a cam) shown in  FIG. 2 , one rotation of a crankshaft or an overhead camshaft makes the plunger  2  reciprocate three times. In the case of a four cycle engine, the crankshaft rotates twice in one combustion stroke. In the case of a three point cam, when the crankshaft rotates the cam  5 , the plunger reciprocates  6  times in one combustion cycle (basically, the fuel injection valve injects fuel into the cylinder once) and pressurizes the fuel  6  times and discharges the fuel from a fuel discharge port  12 . 
         [0030]    At an outlet of the compression chamber  11  is provided a discharge valve unit  8 . The discharge valve unit  8  is configured with a discharge valve seat  8   a , a discharge valve  8   b  which comes in contact with and separates from the discharge valve seat  8   a , a discharge valve spring  8   c  biasing the discharge valve  8   b  against the discharge valve seat  8   a , and a discharge valve stopper  8   d  containing therein the discharge valve  8   b  and the discharge valve seat  8   a ; and the discharge valve seat  8   a  and the discharge valve stopper  8   d  are bonded at a contact part with a welding  8   e  to make an integral unit. 
         [0031]    In addition, inside the discharge valve stopper  8   d  is provided a stepped part  8   f  which limits the stroke of the discharge valve  8   b.    
         [0032]    In the state where there is no difference in fuel pressure between in the compression chamber  11  and in the fuel discharge port  12 , the discharge valve  8   b  is in a valve-closed state, being pressure-contacted with the discharge valve seat  8   a  by a biasing force of the discharge valve spring  8   c . Only after the fuel pressure in the compression chamber  11  becomes higher than the fuel pressure in the fuel discharge port  12 , the discharge valve  8   b  is opened against the discharge valve spring  8   c , whereby the fuel in the compression chamber  11  is discharged at high pressure into a common rail  23  through the fuel discharge port  12 . The discharge valve  8   b , when opening, comes in contact with the discharge valve stopper  8   d  to limit the stroke. Accordingly, the stroke of the discharge valve  8   b  is appropriately determined by the discharge valve stopper  8   d . This arrangement can prevent the fuel discharged at high pressure into the fuel discharge port  12  from flowing back into the compression chamber  11  again because of the delay of closing the discharge valve  8   b  because of too large a stroke, whereby the efficiency of the high pressure pump can be prevented from decreasing. Further, so as to allow the discharge valve  8   b  to move only in the direction of the stroke when the discharge valve  8   b  repeatedly opens and closes, the inner periphery surface of the discharge valve stopper  8   d  guides the discharge valve  8   b . With the above described arrangement, the discharge valve unit  8  works as a check valve for limiting the flow direction of the fuel. 
         [0033]    With these configurations, the compression chamber  11  is configured with the pump housing  1 , the electromagnetic suction valve  30 , the plunger  2 , the cylinder  6 , and the discharge valve unit  8 . 
         [0034]    Thus, of the fuel introduced into the low pressure fuel suction opening  10   a , a required amount is pressurized to a high pressure in the compression chamber  11  of the pump housing  1 , which is a pump main body, by the reciprocating motion of the plunger  2  and is pumped to the common rail  23  from the fuel discharge port  12 . 
         [0035]    The common rail  23  is equipped with injectors  24  and a pressure sensor  26 . The injectors  24  are provided in accordance with the number of cylinders in the internal combustion engine, and open and close valves in accordance with a control signal of the ECU  27  to inject the fuel into the cylinders. 
         [0036]    The high pressure fuel supply pump is fixed on the engine by using a mounting flange  41 , bolts  42 , and bushes  43 . The mounting flange  41  forms a circular fixing part with a full circumference thereof welded to the pump housing  1  on a welded part  41   a . In this embodiment, laser welding is used. 
         [0037]      FIG. 4  is an enlarged view of the electromagnetic suction valve  30  in the non-energized state where the electromagnetic coil  52  is not supplied with current. 
         [0038]      FIG. 5  is an enlarged view of the electromagnetic suction valve  30  in the state where the electromagnetic coil  52  is supplied with current. 
         [0039]    The moving element  31  is made up of two parts: a rod  31   a  and an anchor  31   b . The rod  31   a  and the anchor  31   b  are separate bodies, and between the rod  31   a  and the anchor  31   b  is provided a fine clearance. Since the rod  31   a  is slidably held also by a sliding part  32   d  of a valve seat  32  to be described later, the anchor  31   b  is slidably held by the rod  31   a  so that the motion is limited in the direction of a valve-opening motion and a valve-closing motion. 
         [0040]    The suction valve spring  38  is fit in the suction valve  39  and the suction valve holder  35  as shown in  FIG. 4 , and the suction valve spring  38  generates a biasing force in the direction to separate the suction valve  39  and the suction valve holder  35 . 
         [0041]    The anchor spring  34  is fit in the anchor inner periphery  31   c  and the core inner periphery  33   b  as shown in  FIG. 4 , and the anchor spring  34  generates a biasing force in the direction to separate the anchor  31   b  and the core  33 . Here, the biasing force of the anchor spring  34  is set larger than the biasing force of the suction valve spring  38 . With this arrangement, in the state where the electromagnetic coil  52  is not supplied with current, the difference between the biasing force of the anchor spring  34  and the biasing force of the suction valve spring  38  biases the moving element  31  in the valve-opening direction, leftward in the drawing, as shown in  FIG. 4  so that the suction valve  39  is in the valve-opened state. 
         [0042]    The valve seat  32  is configured with a suction valve seat  32   a , a suction path part  32   b , a press-fitting part  32   c , and a sliding part  32   d . The press-fitting part  32   c  is press-fit and fixed in the core  33 . The suction valve seat  32   a  is press-fit and fixed in the suction valve holder  35 , and the suction valve holder  35  is further press-fit and fixed in the pump housing  1 . This arrangement perfectly secludes the compression chamber  11  and the suction port  30   a  from each other. The sliding part  32   d  slidably holds the rod  31   a.    
         [0043]    The core  33  is configured with a first core part  33   a , a magnetic orifice part  33   b , a core inner periphery  33   c , and a second core part  33   d.    
         [0044]    When the electromagnetic coil  52  is supplied with current, magnetic flux is generated by the magnetic field created around the electromagnetic coil  52  as shown in  FIG. 4 , whereby magnetic attractive force is generated between the anchor  31   b  and the core  33 . In this embodiment, the components constituting the magnetic circuit are the anchor  31   b , the core  33 , a yoke  51  as shown in.  FIG. 4 , and materials of these components are all magnetic materials. In order to increase the magnetic attractive force, it is only necessary to increase the magnetic flux passing through magnetic attractive surfaces S of the anchor  31   b  and the core  33 . For this purpose, between the first core part  33   a  and the second core part  33   d  is provided a magnetic orifice part  33   b . The magnetic orifice part  33   b  is made as thin as possible as far as strength allows, and at the same time the other parts of the core  33  are made to have enough thicknesses. Further, the magnetic orifice part  33   b  is provided in the vicinity of the place where the core  33  and the anchor  31   b  are in contact with each other. Since this arrangement can decrease the magnetic flux passing through the magnetic orifice part  33   b  of the core  33 , most of the magnetic flux passes through the anchor  31   b , whereby the decrease of the magnetic attractive force generated between the core  33  and the anchor  31   b  is kept within an allowable range. 
         [0045]    If cross-sectional area of the magnetic orifice part  33   b  is too large, the magnetic flux directly passes between the first core part  33   a  and the second core part  33   d , and the magnetic flux passing through the anchor  31   b  is accordingly reduced, thereby decreasing the magnetic attractive force. If the magnetic attractive force is small, the response of the moving element  31  is bad, so that the suction valve is not closed or it takes a longer time for the suction valve to be closed, whereby there arises a problem that the amount of the fuel discharged at high pressure cannot be controlled during high speed operation (during high speed rotation of the camshaft) of the internal combustion engine. 
         [0046]    A configuration according to this embodiment does not need to use non-magnetic material for the magnetic orifice part  33   b , and the core  33  can be manufactured as an integral component. As a result, the core  33  does not need to be connected with non-magnetic material by using press-fitting, welding, or the like when assembling the core  33 , and machining and assembling of the components can be simplified. 
         [0047]    The core  33  is fixed by welding to the pump housing  1  at the welded part  37 , thereby secluding the suction port  30   a  and the outside of the high pressure fuel supply pump. 
         [0048]    When the electromagnetic coil  52  is in the non-energized state where the electromagnetic coil  52  is not supplied with current and there is no difference in fluid pressure between in the low pressure fuel flow path  10   c  (suction port  30   a ) and in the compression chamber  11 , the moving element  31  comes into a state where the moving element  31  has been moved leftward in the drawing as shown in  FIG. 4  by the difference between the biasing forces of the anchor spring  34  and the suction valve spring  38 . At this time, since the suction valve  39  comes in contact with the suction valve holder  35 , the position of the suction valve  39  in the valve-opening direction is limited this state, the suction valve  39  is in the valve-opened state. The gap between the suction valve  39  and the valve seat  32  defines a movable range of the suction valve  39 , and this gap corresponds to the stroke. 
         [0049]    If the stroke is too large, it takes a longer time for the suction valve  39  to come in contact with the valve seat  32  and be perfectly closed after the suction valve  39  starts the valve-closing motion upon the energization of the electromagnetic coil  52 . In addition, the distance between the anchor  31   b  and the core  33  is accordingly larger, whereby the magnetic attractive force to be generated becomes smaller. As a result, the response will be insufficient during the high speed operation (during the high speed rotation of the camshaft) of the internal combustion engine; thus, the suction valve  39  cannot be closed at a targeted time, thereby creating a problem that the amount of the fuel discharged at high pressure cannot be controlled. If the stroke is too small, an orifice effect is larger at this part, and the pressure loss is higher. For example, in the case that the internal combustion engine is operated at high speed (high speed rotation of the camshaft) at a high fuel temperature such as 60° C., the fuel is vaporized in this part when the fuel flows from the low pressure fuel flow path  10   c  into the compression chamber  11  on an suction stroke, whereby the amount of fuel to be pressurized to a high pressure is decreased. As a result, there has been a problem that this issue leads to a decrease in the volume efficiency of the high pressure fuel supply pump. In addition, in the return stroke, when the internal combustion engine is operated at high speed (high speed rotation of the camshaft), the fluid force generated on the suction valve  39  (the force in the valve-closing direction generated by the fuel flowing back from the compression chamber  11  to the low pressure fuel flow path  10   c ) becomes large. Thus, the suction valve  39  is closed at an unexpected time in the return stroke, thereby creating a problem that the amount of the fuel discharged at high pressure cannot be controlled. For these reasons, it is very important to control the stroke of the suction valve  39 . 
         [0050]    When a configuration is made as described in this embodiment, the stroke is determined only by the component dimensions of the suction valve holder  35  and the suction valve  39 , whereby the variation of the stroke can be minimized by properly setting the tolerances of these components. 
         [0051]    Further, the clearance between the anchor  31   b  and the core  33  must be set greater than the stroke between the suction valve  39  and the valve seat  32 . If the clearance is smaller than the stroke, the anchor  31   b  collides with the core  33  before the suction valve  39  comes in contact with the valve seat  32  after the suction valve  39  starts the valve-closing motion upon the energization of the electromagnetic coil  52 , whereby there arises a problem that the suction valve  39  does not come in contact with the valve seat  32 , in other words, the suction valve  39  cannot come into the perfect valve-closed state. However, the clearance is too large, even if the electromagnetic coil  52  is supplied with current, sufficient magnetic attractive force is not generated. As a result, the moving element  31  cannot be closed, or the response becomes bad, whereby there arises a problem that the amount of the fuel discharged at high pressure when the internal combustion engine is operated at high speed (high speed rotation of the camshaft). 
         [0052]    In a configuration according to this embodiment, the clearance is determined only by the dimensions of the components such as the suction valve holder  35 , the valve seat  32 , the rod  31   a , the core  33 , and the suction valve  39 , whereby the variation of the clearance can be minimized by properly setting the tolerances of these component dimensions. 
         [0053]    In the state of a suction stroke (during moving from the top dead center position to the bottom dead center position) where the plunger  2  is moved downward in  FIG. 2  by the rotation of the cam  5 , the electromagnetic coil  52  is not supplied with current. At this time, the suction valve  39  is open, whereby the volume of the compression chamber  11  is increased. In this stroke, the fuel flows from the suction port  30   a , through the suction path part  32   b  of the valve seat  32  and a suction opening  36 , and into the compression chamber  11 . Here, since the amount of displacement of the suction valve  39  is limited by the suction valve holder  35 , the suction valve  39  is not opened further. 
         [0054]    In this state, the plunger  2  finishes the suction stroke, and then goes on to the compression stroke (ascending stroke for moving from the bottom dead center to the top dead center). The volume of the compression chamber  11  is decreased with the compression motion of the plunger  2 ; however, in this state, since the fuel once suctioned into the compression chamber  11  is returned back to the low pressure fuel flow path  10   c  (suction port  30   a ) through the suction opening  36  in the valve-opened state, the pressure in the compression chamber is not raised. This stroke is referred to as a return stroke. 
         [0055]    At this time, to the suction valve  39 , there are applied forces, one of which is in the valve-opening direction and is based on the difference between the biasing force of the anchor spring  34  and the biasing force of the suction valve spring  38 , and the other of which is in the valve-closing direction and is based on the fluid force generated when the fuel flows from the compression chamber  11  back into the low pressure fuel flow path  10   c . In order to keep the suction valve  39  open during the return stroke, the difference between the biasing forces of the anchor spring  34  and the suction valve spring  38  is set larger than the fluid force. 
         [0056]    After the electromagnetic coil  52  in this state is supplied with current, magnetic attractive force is generated between the core  33  and the anchor  31   b  so that the core  33  and the anchor  31   b  attract each other; and when the magnetic attractive force becomes stronger than the difference between the biasing forces of the anchor spring  34  and the suction valve spring  38 , the anchor  31   b  starts to move in the valve-closing direction. 
         [0057]    The anchor  31   b  and the rod  31   a  are different bodies; however, when the anchor  31   b  has started in the valve-closing direction, the anchor  31   b  is engaged with a stopper part  31   f  of the rod  31   a , and the anchor  31   b  starts to move with the rod  31   a  in the valve-closing direction. When the anchor  31   b  collides with the core  33 , the anchor  31   b  stops moving and collision noise is created due to the kinetic energy which the anchor  31   b  has. Since the anchor  31   b  and the rod  31   a  are slidably held on each other at an anchor sliding part  31   e , the rod  31   a  continues to move in the valve-closing direction even after the anchor  31   b  stopped moving upon colliding with core  33 , and the rod  31   a  then stops moving with the kinetic energy absorbed by the anchor spring  34 . Therefore, the kinetic energy of the rod  31   a  does not contribute to the noise. The configuration as described above can reduce the noise due to the collision with the core  33 . 
         [0058]    As described above, when the anchor  31   b  and the rod  31   a  move in the valve-closing direction, only the biasing force of the suction valve spring  38  is applied to the suction valve  39 . Thus, the suction valve  39  is moved by the biasing force of the suction valve spring  38  in the valve-closing direction, and then comes into contact with the suction valve seat  32   a  to come into the valve-closed state, thereby closing the suction opening  36 . 
         [0059]    When the suction opening  36  is closed, the fuel pressure in the compression chamber  11  is raised with the ascending motion of the plunger  2 . Then, when the pressure becomes higher than the pressure in the fuel discharge port  12 , the fuel left in the compression chamber  11  is discharged at high pressure through the discharge valve unit (discharge valve mechanism)  8  and supplied to the common rail  23 . This stroke is referred to as a discharge stroke. The compression stroke of the plunger  2  is thus constituted by a return stroke and the discharge stroke. 
         [0060]    In a discharge stroke, after the pressurized fuel starts to be supplied, the supply of current to the electromagnetic coil  52  can be removed. This is because, when the pressure in the compression chamber  11  becomes higher than the pressure in the fuel discharge port  12 , the force due to the pressure in the compression chamber  11  is applied to the suction valve  39  in the valve-closing direction, and the force becomes larger than the biasing force of the suction valve spring  38 . Thus, the power consumption in the electromagnetic coil  52  can be reduced. 
         [0061]    Further, by controlling the time at which the electromagnetic coil  52  of the electromagnetic suction valve  30  is supplied with current, the amount of the discharged high pressure fuel can be controlled. 
         [0062]    When the electromagnetic coil  52  is supplied with current at a sooner time, the portion of the return stroke gets smaller and the portion of the compression stroke gets larger in the discharge stroke. 
         [0063]    As a result, the smaller amount of fuel is returned to the low pressure fuel flow path  10   c  (suction port  30   a ) and the larger amount of fuel is discharged at high pressure. 
         [0064]    Alternatively, when the electromagnetic coil  52  is supplied with current at a later time, the portion of the return stroke gets larger and the portion of the discharge stroke gets smaller in the compression stroke. As a result, the larger amount of fuel is returned to the low pressure fuel flow path  10   c , and the smaller amount of fuel is discharged at high pressure. The time to supply current to the electromagnetic coil  52  is controlled by the instruction from the ECU  27 . 
         [0065]    When the plunger  2  finishes the compression stroke and starts the suction stroke, the volume of the compression chamber  11  starts to increase again, and the pressure in the compression chamber  11  decreases. Thus, the fuel flows into the compression chamber  11  from the low pressure fuel flow path  10   c  through the suction port  30   a . The suction valve  39  starts the valve-opening motion leftward in the drawing due to the difference between the biasing forces of the anchor spring  34  and the suction valve spring  38 ; then, after having moved by the distance of the stroke, the suction valve  39  collides with the suction valve holder  35  and stops the motion. Since this collision is caused by the difference between the biasing forces of the anchor spring  34  and the suction valve spring  38 , the energy of collision is not so large. Therefore, the collision part does not need to have high hardness. For this reason, this embodiment employs austenite stainless steel as the material for the suction valve holder  35 . In addition, at this time, the anchor  31   b  is engaged with the stopper part  31   f  of the rod  31   a  and performs the valve-opening motion together with the rod  31   a.    
         [0066]    By configuring as described above and controlling the time to supply current to the electromagnetic coil  52 , the amount of the fuel discharged at high pressure can be controlled to be the amount which the internal combustion engine requires. 
         [0067]    At this time, the moving element  31  repeats the motion in the lateral direction in the drawing with the descending and ascending motion of the plunger  2 , and the suction valve  39  repeats the opening-closing motion of the suction opening  36 . Here, since there are fine clearances between the anchor  31   b  and the rod  31   a  of the moving element  31  and between the rod  31   a  and the valve seat  32 , the moving element  31  is slidably held, with the motion being limited in the direction of the valve-opening motion and the valve-closing motion, thereby repeating a sliding motion. The clearances at the two sliding parts are set as follows. If the clearances are too large, the rod  31   a  and the anchor  31   b  move in a direction different from the valve-opening motion or the valve-closing motion. Then, the response of the valve-opening motion and the valve-closing motion will be bad, whereby the opening and closing of the suction valve  39  cannot follow during the high speed operation (during the high speed rotation of the camshaft) of the internal combustion engine, and the amount of the discharged high pressure fuel cannot be controlled. Therefore, the clearances need to be set have appropriate values. In addition, the anchor sliding part  31   e  and the sliding part  32   d  need to have sufficiently low surface roughness so as not to create friction against the valve-opening motion and the valve-closing motion of the moving element  31 . 
         [0068]    Further, since high hardness is required from the point of view of durability, martensite stainless steel having high hardness is used as the material for the suction valve  39 , the valve seat  32  and the rod  31   a.    
         [0069]    The martensite stainless steel as the material for the rod  31   a  and the valve seat  32  is known as magnetic material, which creates magnetic flux therein when located in a magnetic field. Thus, a flow of magnetic flux is created in the rod  31   a  and the valve seat  32  through the anchor  31   b , thereby generating magnetic attractive force with which the rod  31   a  and the valve seat  32  attract each other. However, in the configuration of this embodiment, most of the magnetic flux flows through only the magnetic attractive surface S between the anchor  31   b  and the core  33 , whereby there is no possibility that the suction valve  39  cannot be opened. 
         [0070]    In addition, when the moving element  31  repeats the valve-opening motion and the valve-closing motion, the rod  31   a  gets in and out of the internal cylindrical part of the core  33 , whereby the volume of the fuel in the internal cylindrical part of the core  33  increases and decreases. 
         [0071]    Since the internal cylindrical part of the core  33  is filled with fuel, when the rod  31   a  gets in and out of the internal cylindrical part of the core  33 , the fuel displaced by the rod  31   a  have to reciprocates right and left in the drawing through a guide part  32   d  of the valve seat  32 . However, the clearance between the guide part  32   d  and the rod  31   a  of the valve seat  32  is so thin that sufficient amount of fuel cannot pass through, thereby impeding the response of the valve-opening motion and the valve-closing motion of the moving element  31 . To address this issue, a communication hole  32   e  is provided in the valve seat  32 . 
         [0072]    A volume of the space inside the cylindrical part constituted by the inner periphery surface of the anchor  31   b  and the inner periphery surface of the core  33  also increases and decreases with the valve-opening motion and the valve-closing motion of the moving element  31 . Further, when the anchor  31   b  and the core  33  collides with each other, the space inside the cylindrical part becomes perfectly sealed; thus, there is a problem that at the moment when the anchor  31   b  leaves from the core  33  and moves onto the valve-opening motion, the pressure decreases, whereby the valve-opening motion of the moving element  31  becomes unstable. To address this problem, an anchor communication hole  31   d  is provided in the anchor  31   b.    
         [0073]    The configuration as described above facilitates the fuel to pass through and secures the response of the valve-opening motion and the valve-closing motion of the moving element  31 . 
         [0074]    The electromagnetic coil  52  is configured with a lead wire  54  wound about the axis of the moving element  31 . The both ends of the lead wire  54  are welded to the terminals  56  at the lead wire welded part  55 . The terminals are made of conductive material and opened at a connector part  58 , and when a connector from the ECU  27  is connected to the connector part  58 , the terminals come in contact with the corresponding terminals and transfers current to the electromagnetic coil  52 . 
         [0075]    In this embodiment, the lead wire welded part  55  is positioned outside the yoke  51 . Since the lead wire welded part  55  is positioned outside the magnetic circuit, the lead wire welded part  55  does not require the space for the lead wire welded part  55 ; therefore, the magnetic circuit can have a short overall length, which arrangement makes it possible to generate sufficient magnetic attractive force between the core  33  and the anchor  31   b.    
         [0076]      FIG. 6  shows the state before the electromagnetic suction valve  30  being assembled in the pump housing  1 . 
         [0077]    In this embodiment, a suction valve unit  81  and a connector unit  82  are made first as units. Next, the suction valve holder  35  of the suction valve unit  81  is press-fit and fixed to the pump housing  1 , and welding is then performed at the welded part  37  all around the circumference. In this embodiment, laser welding method is used for welding. In this state, the connector unit  82  is press-fit and fixed to the core  33 . With this method, the direction of the connector part  58  can be freely selected. 
         [0078]    In the above three strokes of the suction stroke, the return stroke, and the discharge stroke, the fuel gets in and out of the suction port  30   a  (low pressure fuel flow path  10   c ) all the time; thus, the fuel pressure has a cyclic pulsation. This pressure pulsation is absorbed and reduced in the pressure pulsation reduction mechanism  9 , and the pressure pulsation is blocked from being transmitted to the suction pipe  28  which communicates from the feed pump  21  to the pump housing  1 , thereby preventing breakage or the like of the suction pipe  28  and enabling the fuel to be supplied to the compression chamber  11  with stable fuel pressure fuel. Since the low pressure fuel flow path  10   b  is connected to the low pressure fuel flow path  10   c , the fuel is well supplied to the both sides of the pressure pulsation reduction mechanism  9 , thereby effectively reducing the pressure pulsation of the fuel. 
         [0079]    The pressure pulsation reduction mechanism  9  is configured with two metal diaphragms, the outer peripheries of which are fixed by welding at a welded part at all the circumference with the space between the both diaphragms filled with gas. The pressure pulsation reduction mechanism  9  is also configured such that, when the both sides of the pressure pulsation reduction mechanism  9  are loaded with a low pressure pulsation, the pressure pulsation reduction mechanism  9  changes the volume so that the low pressure pulsation is reduced. 
         [0080]    The plunger  2  is made up of a large-diameter part  2   a  to slide on the cylinder  6  and a small-diameter part  2   b  to be slide on the plunger seal  13 . The diameter of the large-diameter part  2   a  is set greater than the diameter of the small-diameter part  2   b , and both are set coaxial to each other. Between the lower end of the cylinder  6  and the plunger seal  13 , there is provided a circular low pressure seal chamber  10   f , and the circular low pressure seal chamber  10   f  provided in the cylinder holder  7  communicates with the low pressure fuel flow path  10   c  through low pressure fuel communication paths  10   d  and  10   e , and a circular low-pressure path  10   h . Since a stepped part  2   c  between the large-diameter part  2   a  and the small-diameter part  2   b  is located in the circular low pressure seal chamber  10   f , when the plunger  2  repeats a sliding motion in the cylinder  6 , the stepped part between the large-diameter part  2   a  and the small-diameter part  2   b  repeats an up-and-down motion in the circular low pressure seal chamber  10   f , hence changing the volume of the circular low pressure seal chamber  10   f . In the suction stroke, the volume of the circular low pressure seal chamber  10   f  decreases, and the fuel in the circular low pressure seal chamber  10   f  flows to the low pressure fuel flow path  10   c  through the low pressure fuel communication paths  10   d  and  10   e . In the return stroke and the discharge stroke, the volume of the circular low pressure seal chamber  10   f  increases, and the fuel in the low pressure fuel communication path  10   d  flows to the circular low pressure seal chamber  10   f  through the low pressure fuel communication path  10   e.    
         [0081]    In regard to the low pressure fuel flow path  10   c , in the suction stroke, the fuel flows into the compression chamber  11  from the low pressure fuel flow path  10   c , and on the other hand, the fuel flows into the low pressure fuel flow path  10   c  from the circular low pressure seal chamber  10   f . In the return stroke, the fuel flows into the low pressure fuel flow path  10   c  from the compression chamber  11 , and on the other hand, the fuel flows into the circular low pressure seal chamber  10   f  from the low pressure fuel flow path  10   c . In addition, in the discharge stroke, the fuel flows into the circular low pressure seal chamber  10   f  from the low pressure fuel flow path  10   c . As described above, since the circular low pressure seal chamber  10   f  has a function to help the fuel get in and out of the low pressure fuel flow path  10   c , the circular low pressure seal chamber  10   f  is effective to reduce the pressure pulsation of fuel created in the low pressure fuel flow path  10   c.    
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  pump housing 
           2  plunger 
           2   a  large-diameter part 
           2   b  small-diameter part 
           3  tappet 
           4  cam 
           6  cylinder 
           7  cylinder holder 
           8  discharge valve unit 
           9  pressure pulsation reduction mechanism 
           10   a  low pressure fuel suction opening 
           10   b ,  10   c  low pressure fuel flow path 
           10   d ,  10   e  low pressure fuel communication path 
           10   f  circular low pressure seal chamber 
           11  compression chamber 
           12  fuel discharge port 
           13  plunger seal 
           20  fuel tank 
           21  feed pump 
           23  common rail 
           24  injector 
           26  pressure sensor 
           27  engine control unit (ECU) 
           30  electromagnetic suction valve 
           31  moving element 
           31   a  rod 
           31   b  anchor 
           31   c  anchor inner periphery 
           31   d  anchor communication hole 
           31   e  anchor sliding part 
           32  valve seat 
           33  core 
           34  anchor spring 
           35  suction valve holder 
           38  suction valve spring 
           39  suction valve 
           52  electromagnetic coil

Technology Classification (CPC): 5