Patent Publication Number: US-7707996-B2

Title: High pressure fuel supply pump for internal combustion engine

Description:
TECHNICAL FIELD 
   The present invention relates to a high pressure fuel supply pump, and particularly, to a high pressure fuel supply pump suitable for feeding under pressure high pressure fuel to a fuel injection valve of an internal combustion engine. 
   Further, the invention relates to a high-pressure fuel supply pump provided with a variable capacity mechanism for adjusting quantity of fuel discharged. 
   BACKGROUND ART 
   {circle around (1)} In a conventional high pressure fuel supply pump, for example, as shown in Japanese Patent No. 2690734 Specification, fuel is supplied from a tank to a high pressure pump by a low pressure pump to increase its pressure to high, and is supplied to a common rail. Within the high pressure pump, an intake passage and a discharge passage are communicated with an upper end surface of a pressurizing chamber and an intermediate side wall of the pressurizing chamber, respectively. 
   Further, in the other conventional high pressure fuel supply pump, for example, as shown in Japanese Patent Application Laid-Open No. Hei10-318091 Publication, an intake passage and a discharge passage are communicated with an intermediate side wall or an upper end surface of a pressurizing chamber and an upper end surface of the pressurizing chamber, respectively. 
   Incidentally, when the engine is first started, or restarted after stoppage for a long period, vapor of air or fuel is present within a fuel pipe. Therefore, immediately after start, the pressure increasing characteristic of the high pressure pump is apt to be deteriorated. To prevent this, it is necessary to rapidly discharge air or fuel vapor within the pressurizing chamber of the high pressure pump to thereby secure the pressure increasing characteristic of the high pressure pump, and to rapidly supply fuel into the common rail by a low pressure pump of large discharge capacity. 
   However, in the high pressure fuel supply pump described in Japanese Patent No. 2690734 Specification, an intake passage and a discharge passage are provided on an upper end surface of a pressurizing chamber and an intermediate side wall of the pressurizing chamber, respectively, thus posing a problem in that in the intake stroke, vapor or the like is hard to be discharged on the intake passage side due to the intake fuel, and in the discharge stroke, the vapor or the like is apt to remain within the pressurizing chamber above the discharge passage, thereby lowering the supply property of fuel. 
   Also in the constitution described in FIG. 5 of Japanese Patent Application Laid-Open No. Hei10-318091 Publication, a discharge passage within the high pressure pump is provided in an upper end of a pressurizing chamber, and therefore, vapor within the pressurizing chamber is apt to be discharged. However, both the above-described prior arts have a problem in that since fuel fed from the low pressure pump is communicated with the pressurizing chamber which changes in volume due to piston motion within the high pressure pump, even if an attempt is made to supply fuel to the common rail by the low pressure pump immediately after the engine starts, the piston motion within the pressurizing chamber makes resistance to delay a supply of fuel. 
   Further, in the conventional constitution described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei10-318091 Publication, since an upper flat surface of a cylinder fixing portion is compressed and fitted, fuel flows into the outer periphery of a delivery valve passing through the outer circumference of a cylinder when the intake passage is communicated with the intermediate side wall of the pressurizing chamber, because of which, an O-ring is provided for sealing from outside. However, this poses a problem in that when an O-ring is formed from an elastic member, it moves due to the pressure variation in the pressuring chamber, and therefore, pressure rising of the pressurizing chamber reduces, or rubbing wear or rupture of the O-ring occurs. 
   {circle around (2)} Further, with respect to a seal mechanism against a leakage of high pressure fuel, in the conventional high pressure fuel supply pump, fuel in the pressurizing chamber is increased to high pressure by reciprocating movement of a plunger. Here, since fuel pressure pressurized is considerably high pressure, fuel possibly leaks out of a clearance between the plunger and the cylinder. 
   In view of the foregoing, in the conventional high pressure fuel supply pump, a seal material of an elastic member is disposed on the end of a sliding portion of a plunger, as described in Japanese Patent Application Laid-Open No. Hei 10-318068 Publication and Japanese Patent Application Laid-Open No. Hei8-368370 Publication, to prevent a leakage of fuel. On the fuel chamber side of the seal material is provided with a passage communicated with a fuel tank which is substantially at atmospheric pressure. Further, a sliding portion of the plunger is provided therein with a fuel reservoir leading to a fuel intake port which is a low pressure portion. By the provision of these constitutions noted above, when one end of the seal material is in contact with the atmospheric pressure, the other end is also communicated with the fuel tank to be substantially atmospheric pressure so as not to apply high pressure of the pressurizing chamber onto the seal material directly, thus preventing a leakage of fuel from the seal material. 
   However, the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 10-318068 Publication poses a problem in that since the distance from the fuel reservoir (a pulsation reducing space in  FIG. 1 ) in communication with the low pressure fuel chamber to the sliding end of the plunger is short, when the seal material is broken or fallen off, a large quantity of fuel possibly flows outside from a clearance of the plunger sliding portion. 
   On the other hand, in the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 8-68370 Publication, since the distance from the fuel reservoir (a sliding hole  11   a  of a cylinder  11  in  FIG. 1 ) in communication with the low pressure fuel chamber to the sliding end of the plunger is long, it is possible to make small the quantity of fuel which flows out when the seal material is broken or fallen off. However, since the sliding distance of the plunger from the pressurizing chamber to the fuel reservoir cannot be made long, thus posing a problem in that when pressurized, fuel leaks into the low pressure portion from a clearance of the sliding portion of the plunger to deteriorate the discharge efficiency. 
   Further, in the high pressure fuel supply pump described in FIG. 1 of Japanese Patent Application Laid-Open No. Hei 8-68370 Publication, the distance from the pressurizing chamber to the fuel reservoir is prolonged to thereby enable prevention of a leakage of fuel, but it is necessary, to this end, to prolong the full length of the sliding portion, thus posing a problem in that the whole pump becomes large in size. 
   Further, in the conventional high pressure fuel supply pumps described in Japanese Patent Application Laid-Open No. Hei 10-318068 and No. Hei 8-68370, since both ends of the seal material are made substantially at atmospheric pressure, it is necessary to provide, on the fuel chamber side of the seal material, a passage in communication with the fuel tank substantially at atmospheric pressure, thus making it necessary to have a passage for connecting the pump to the fuel tank. As a result, there was a problem in that processing of a pump becomes complicated, and a piping for connecting the pump to the tank is necessary, thus increasing the cost. 
   {circle around (3)} Next, with respect to the variable capacity mechanism, an apparatus heretofore known has the constitution wherein, for example, as described in Japanese Patent No. 2690734, an electromagnetic valve is provided within an intake passage, and a returning quantity to the intake side is controlled by opening and closing operation of the electromagnetic valve to thereby adjust the discharge quantity. 
   Further, the constitution is known for example, from Japanese Patent Application Laid-Open No. Hei 10-153157, wherein a check valve is provided within an intake passage, and a spill (overflow) valve is provided in a fuel spill (overflow) passage in communication with a pressurizing chamber whereby quantity of fuel spill to a fuel tank is controlled by opening and closing the spill valve to thereby adjust the discharge quantity. 
   Since rotation of a pump increases by a multiple of a cam of the pump with respect to the number of revolutions of the engine, it is necessary to open and close the intake valve or the spill valve in order of msec (millisecond). However, in such a state of high speed opening and closing, mass of the electromagnetic valve influences on the respondence. 
   DISCLOSURE OF INVENTION 
   A first object of the present invention is to provide a high pressure fuel supply pump capable of enhancing fuel supply property to a common rail immediately after start of an engine. 
   A second object of the present invention is to provide a high pressure fuel supply pump capable of enhancing pressure increasing property to a common rail immediately after start of an engine. 
   A third object of the present invention is to provide a high pressure fuel supply pump which suppresses an external leakage of fuel to a small quantity, even when a seal material of a sliding portion is broken or fallen off, and which is small in size and cheap. 
   A fourth object of the present invention is to provide a high pressure fuel supply pump having a variable capacity mechanism which is excellent in opening and closing respondence. 
   (1) For achieving the aforementioned first object, the present invention provides a high pressure fuel supply pump for pressurizing fuel supplied from an intake passage of fuel by a pressurizing member to feed it under pressure to a discharge passage, wherein in addition to a main pressurizing chamber in which said pressurizing member is arranged, a sub-pressurizing chamber for communication between said intake passage and said discharge passage is provided. 
   With the above constitution, fuel supplied from an intake passage by a low pressure pump can be supplied to a common rail via a discharge passage without being impeded by resistance caused by motion of a pressurizing member of a high pressure pump, thus enabling enhancement of fuel supply property to the common rail. 
   (2) In the above-described (1), preferably, said intake passage and said discharge passage are placed in communication with an upper end portion of said pressurizing chamber. 
   With the above constitution, in the discharge stroke, discharging of air and fuel vapor in the pressurizing chamber can be carried out securely, and a dead volume of the pressurizing chamber (a volume of the pressurizing chamber at the top dead center) can be minimized without impairing a fuel supply to the pressurizing chamber, thus enabling miniaturization of the high pressure pump. 
   (3) In the above-described (1), preferably, said sub-pressurizing chamber is arranged substantially annularly on the outer periphery of said main pressurizing chamber. 
   (4) For achieving the aforementioned second object, the present invention provides a high pressure fuel supply pump for pressurizing fuel supplied from an intake passage of fuel by a pressurizing member to feed it under pressure to a discharge passage, comprising a pressurizing chamber forming member having a tapered surface on the end and formed from a member separately from a pump body, said tapered surface of the pressurizing chamber forming member being compressed and fitted by a fixing member to thereby form said pressurizing chamber. 
   With the above constitution, the pressurizing chamber forming member can be fixed without providing an elastic member such as rubber, thus enabling enhancement of pressure increasing property to the common rail. 
   (5) For achieving the aforementioned third object, the present invention provides a high pressure fuel supply pump having an intake passage of fuel, a pressurizing chamber in communication with a discharge passage, and a pressurizing member for feeding under pressure fuel within said pressurizing chamber to said discharge passage, comprising: a seal material arranged on a sliding portion of said pressurizing member, a connecting passage for communicating the fuel chamber side of said seal material with the intake passage of fuel, and a check valve for impeding entry of fuel into said seal material side from said fuel intake passage side. 
   With the aforementioned constitution, even if the seal material is broken or the like, a leakage of fuel due to the check valve can be prevented, and by providing no portion in communication with the atmospheric, miniaturization and reduction in cost can be achieved. 
   (6) In the aforementioned (5), preferably, said check valve is opened when operation of a pump is stopped. 
   With the above constitution, it is possible to prevent the check valve when the pump is stopped from being adhered to the seat surface. 
   (7) In the aforementioned (6), preferably, said check valve is formed from an elastic member. 
   (8) The fourth object of the present invention is achieved by providing a high pressure pump comprising a valve body for opening and closing a fuel through-hole provided between a cylinder and a low pressure side passage, a spring for biasing said valve body in a closing direction with respect to said through-hole, an operating rod in contact with or spaced from said valve body to adjust opening and closing timing of said valve body, and an electromagnetic mechanism for driving the operating rod electromagnetically in association with the operating condition of the internal combustion engine. 
   In the present invention constructed as described above, since mass of the valve body will not be a load with respect to the electromagnetic driving mechanism, the respondence of the discharge capacity control mechanism is improved. 
   (9) In the aforementioned (8), the electromagnetic driving mechanism can be used in common with the intake valve mechanism. 
   (10) In the aforementioned (8), the electromagnetic driving mechanism can be constituted as a spill (overflow) valve mechanism. 
   (11) Further, preferred embodiments of the present invention are as follows: 
   An intake valve is provided on the intake passage, and to the intake valve is applied a small biasing force in a closing direction to a degree that automatically opens when fuel flows into the pressurizing chamber. Further, an engaging member having a biasing force for holding in an opening direction is engaged with the intake valve, and the engaging member controls the intake valve to open and close according to operating timing of an actuator. 
   Thereby, in the intake stroke of the pump, the intake valve can be opened irrespective of the operation of the actuator. Also in the compression stroke, since the intake valve maintains its open state unless the actuator is operated (ON), surplus fuel in the pressurizing chamber reduced as a result of the compression is returned to the intake side. Accordingly, since pressure of the pressurizing chamber is not risen, fuel is not fed under pressure to the discharge passage. In this state, when the actuator is operated (ON), the intake valve is closed by self-closing force so that pressure of the pressurizing chamber increases and the fuel is fed under pressure to the discharge passage. In this manner, the discharge quantity can be adjusted by controlling the operating timing of the actuator. 
   Upon maximum discharging, the ON state of the actuator is maintained whereby the intake valve is automatically opened and closed in synchronism with pressure of the pressurizing chamber, and therefore, the maximum discharge can be carried out without depending on the respondence of the actuator. 
   Further, upon low discharging, the actuator is turned ON from the latter half of the compression stroke and turned OFF till the termination of the intake stroke, and therefore, the high respondence is not necessary. 
   Furthermore, at the time of discharge, only the intake valve is required to close, and therefore, a leakage of fuel from the seat can be reduced. 
   (12) Preferably, if an electromagnetic type actuator is employed, control can be made simply by an engine control unit. Further, a fuel injection valve can also be used for the actuator. 
   (13) Further, preferably, an engaging portion between an intake valve and an engaging member is made in the form of a concavo-convex engagement, whereby deviation, slipping out or the like of the engaging portion can be prevented to secure positive operation. 
   (14) Further, preferably, a ball valve is used for the intake vale or the discharge valve, whereby the processing accuracy of the seat portion can be readily enhanced. Further, a cylindrical member is engaged with the ball valve, and the outer circumference of the cylindrical member is held capable of being reciprocated and slidably moved within the intake passage, so that the oscillation of the ball valve can be prevented. Further, since the cylindrical member is separated from the ball valve, both of them can be fabricated in an easy method. 
   (15) Further, preferably, in a plunger reciprocating and sliding type pump, a sliding portion of a plunger is made to be a cylindrical member separately from a pump body, whereby only the sliding member can be formed of a material suitable for sliding movement. Further, an inner wall of the cylindrical member is formed with a sliding hole of a plunger and an expanded inner wall portion having a larger inside diameter than the former, and only the outer peripheral portion of the diffused inner wall can be pressed and fitted in the pump body whereby preventing the sliding hole from being deformed. Accordingly, it is not necessary to re-process the sliding hole after fitting the cylindrical member, enabling fabrication at low cost. 
   (16) Further, preferably, a clearance is provided at a position other than the portion in which the cylindrical member is fitted in the pump body, an annular passage is formed on the outer peripheral portion of the cylindrical member, and the annular passage is made to communicate with one end of the plunger sliding hole and a fuel introducing passage, whereby fuel introducing pressure is guided into the annular passage to reduce a pressure difference relative to the pressurizing chamber, and thus enabling reduction in leakage quantity of fuel when passing through the fitting portion and the sliding portion from the pressurizing chamber. Further, since the fuel covers the outer circumference of the sliding portion, it is possible to cool the sliding portion. 
   (17) Moreover, preferably, a member in engagement with the pump body and the cylindrical member is provided in the fuel passage whereby the cylindrical member can be prevented from falling off while preventing a leakage of fuel from the engaging portion to the outside the pump or occurrence thereof. 

   
     BRIEF DESCRIPTION OF DRAWING 
       FIG. 1  is a horizontal sectional view of a high pressure fuel supply pump according to a first embodiment of the present invention. 
       FIG. 2  is a vertical sectional view of a high pressure fuel supply pump according to a first embodiment of the present invention. 
       FIG. 3  is a system constituent view of a fuel injection system using a high pressure fuel supply pump according to a first embodiment of the present invention. 
       FIG. 4  is a vertical sectional view of a high pressure fuel supply pump according to a second embodiment of the present invention. 
       FIG. 5  is a partial enlarged view of  FIG. 4 . 
       FIG. 6  is a partial enlarged view showing a vertical sectional view of a high pressure fuel supply pump according to a third embodiment of the present invention. 
       FIG. 7  is an entire system constituent view of a fuel injection system using a high pressure fuel supply pump according to a fourth embodiment of the present invention. 
       FIG. 8  is a longitudinal sectional view showing the constitution of a high pressure fuel supply pump according to a fourth embodiment of the present invention. 
       FIG. 9  is a sectional view when a check valve is opened, using a high pressure fuel supply pump according to a fourth embodiment of the present invention. 
       FIG. 10  is a sectional view when a check valve is closed using a high pressure fuel supply pump according to a fourth embodiment of the present invention. 
       FIG. 11  is a view for explaining a conception of a variable capacity mechanism according to the present invention, by conceptually showing  FIGS. 2 and 8 . 
       FIGS. 12 to 14  are respectively views showing other embodiments of a spill valve (an overflow valve) or an intake valve of another embodiment. 
       FIG. 15  is a concrete enlarged sectional view of the intake vale of  FIGS. 2 and 8 , and a portion corresponding to a solenoid driving portion. 
       FIG. 16  is an enlarged sectional view of a P portion of  FIG. 15 . 
       FIG. 17  is a side view of a holder. 
       FIG. 18  is a cross sectional view of a holder. 
       FIG. 19A  is a sectional view of an intake valve,  19 B being a right side view thereof. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   The constitution of a high pressure fuel supply pump according to a first embodiment of the present invention will be described hereinafter with reference to  FIGS. 1 to 3 . 
     FIG. 1  is a horizontal sectional view of a high pressure fuel supply pump according to the present embodiment,  FIG. 2  is a vertical sectional view of a high pressure fuel supply pump according to the present embodiment, and  FIG. 3  is a system constituent view of a fuel injection system using a high pressure fuel supply pump according to the present embodiment. Note that in the drawings, the same reference numerals indicate the same parts. 
   As shown in  FIG. 1 , a pump body  1  comprises a fuel intake passage  10 , a discharge passage  11 , and a pressurizing chamber  12 . The intake passage  10  is provided with an intake valve  5  in the form of a check valve which is held in one direction by a spring  5   a  to limit a flowing direction of fuel from the fuel intake passage  10  to a fuel intake passage  5   b . The discharge passage  11  is provided with a discharge valve  6  in the form of a check valve which is held in one direction by a spring  6   a  to limit a flowing direction of fuel from a fuel discharge passage  6   b  to the fuel discharge passage  11 . 
   In the present embodiment, the pressurizing chamber  12  is divided into a main pressurizing chamber  12   a  and an annular sub-pressurizing chamber  12   b  positioned on the outer periphery thereof, which are communicated by a communication hole  12   c  to each other. The sub-pressurizing chamber  12   b  is provided for communication between the fuel intake passage  5   b  and the fuel discharge passage  6   b.    
   As shown in  FIG. 2 , a plunger  2  as a pressurizing member is held slidably in the main pressurizing chamber  12   a  of the pressurizing chamber  12 . A lifter  3  provided on the lower end of the plunger  2  is pressed against a cam  100  by means of a spring  4 . The plunger  2  is reciprocated by the cam  100  rotated by an engine cam shaft or the like to change capacity in the pressurizing chamber  12 . When the intake valve  5  is closed during the compression stroke of the plunger  2 , pressure in the pressurizing chamber  12  rises whereby the discharge valve  6  is automatically opened to feed fuel under pressure to a common rail  53 . While the intake valve  5  is automatically opened when pressure of the pressurizing chamber  12  gets lower than that of a fuel introducing port, closing valve operation thereof is decided by operation of a solenoid  200 . 
   The solenoid  200  is mounted in the pump body  1 . An engaging member  201  and a spring  202  are provided on the solenoid  200 . When the solenoid  200  is turned OFF, the engaging member  201  is biased in a direction of opening the intake valve  5  by means of a spring  202 . The biasing force of the spring  202  is greater than that of the intake valve spring  5   a , so that when the solenoid  200  is turned OFF, the intake valve  5  is in the open state, as shown in  FIGS. 1 and 2 . 
   Energization to the solenoid  200  is controlled so that where high pressure fuel is supplied from the pump body  1 , the solenoid  200  assumes an ON (energization) state, and where a supply of fuel is stopped, the solenoid  200  assumes an OFF (deenergization) state. 
   When the solenoid  200  maintains the ON (energization) state, electromagnetic force greater than the biasing force of the spring  202  is generated to draw the engaging member  201  towards the solenoid  202 , and therefore, the engaging member  201  is separated from the intake valve  5 . In this state, the intake valve  5  serves as an automatic valve which is opened and closed in synchronism with reciprocating motion of the plunger  2 . Accordingly, during the compression stroke, the intake valve  5  is closed, and fuel for a portion reduced in capacity of the pressurizing chamber  12  pushes to open the discharge valve  6  and is fed under pressure to the common rail  53 . 
   On the other hand, when the solenoid  200  maintains an OFF (deenergization) state, the engaging member  201  is engaged with the intake valve  5  by the biasing force of the spring  202  to hold the intake valve  5  in an open state. Accordingly, also in the compression stroke, pressure of the pressurizing chamber  12  maintains a low pressure state substantially equal to that of the fuel introducing port, and therefore, the discharge valve  6  cannot be opened, and fuel for a portion reduced in capacity of the pressurizing chamber  12  is returned toward the fuel introducing port passing through the intake valve  5 . 
   If the solenoid  200  is turned into the ON state in the midst of the compression stroke, fuel is fed under pressure to the common rail  53  from that time on. If the pressure feeding once starts, pressure in the pressurizing chamber  12  rises, and therefore, even if the solenoid  200  is turned into the OFF state later, the intake valve  5  maintains its closed state and the intake stroke is synchronized with the beginning to automatically open the valve. 
   The system constitution of a fuel supply system using a high pressure fuel supply pump according to the present embodiment will be described hereinafter with reference to  FIG. 3 . 
   Fuel in a tank  50  is guided to a fuel supply port  10  of the pump body  1  by a low pressure pump  51 . Pressure of fuel guided to the fuel supply port  10  is regulated so as to have a fixed pressure by means of a pressure regulator  52 . Fuel supplied to the pump body  1  is pressurized by the pump body  1  and fed under pressure from a fuel discharge port  11  to the common rail  53 . Mounted on the common rail  53  are an injector  54 , a relief valve  55 , and a pressure sensor  56 . The injector  54  is mounted while adjusting its number with the number of cylinders of the engine, and injects at the timing and quantity according to a fuel injection control signal of an engine control unit ECU. The relief valve  55  opens when pressure in the common rail  53  exceeds a fixed value to prevent a breakage of piping system. 
   When the engine starts first time or stops for a long period of time, air or fuel vapor is present in the fuel piping (including the interior of a high pressure pump and a common rail). Therefore, when the engine is started, it is necessary to rapidly fill the common rail  53  with fuel. 
   With respect to this point, in the present embodiment, the pressurizing chamber  12  comprises the main pressurizing chamber  12   a  for pressurizing fuel by reciprocation of the plunger  2 , and the sub-pressurizing chamber  12   b  for communication between the fuel intake passage  5   b  and the fuel discharge passage  6   b , as described above. 
   Accordingly, even if the plunger  2  is stopped at the top dead center and slidably moved, a sufficient passage can be formed between the intake passage  5   b  and the discharge passage  6   b  by the sub-pressurizing chamber  12   b . Therefore, fuel can be fed under low pressure to the common rail  53  by the low pressure pump  51  before the high pressure pump starts feeding fuel under high pressure, and the common rail  53  can be filled with fuel momentarily. When the engine starts as mentioned above, pressure in the common rail  53  is close to the atmospheric pressure, and therefore, even if fuel pressure of the fuel discharge port  6   b  is in the state of discharge pressure of the low pressure fuel pump  51 , the discharge valve  6  opens so that fuel flows from the fuel discharge port  6  to the fuel discharge port  11 , and fuel can be supplied to the common rail  53 . 
   Further, when fuel in the piping is supplied to the common rail  53  by the low pressure pump  61  whose discharge capacity is high, air and vapor can be fed under pressure to the common rail at the same time. 
   Further, in the present embodiment, the fuel intake passage  5   b  and the fuel discharge passage  6   b  are communicated with the upper end side wall, and no vapor reservoir is provided in the pressurizing chamber  12 , as shown in  FIG. 2 . Therefore, vapor or the like is fed under pressure from the discharge passage  6   b  to the common rail  53  side and is not stayed in the pressurizing chamber  12 . Accordingly, the pressurizing chamber is momentarily filled with fuel, making it possible to feed fuel under high pressure, it is possible to securely discharge air and fuel vapor within the pressurizing chamber. 
   Further, when the plunger  2  is positioned at the top dead center, the intake passage  5   b  and the discharge passage  6   b  are not blocked merely by providing an adequate clearance (1 to 2 mm) to prevent interference between the upper end of the plunger  2  and the upper surface of the pressurizing chamber  12 , because of which, the dead volume of the pressurizing chamber (the volume of the pressurizing chamber at the top dead center) can be minimized without impairing a supply of fuel to the pressurizing chamber, enabling miniaturization of a pump. 
   As described above, according to the present embodiment, since when the engine starts or the like, low pressure fuel can be supplied to the common rail without impairing piston motion of the high pressure pump, the fuel supply property to the common rail immediately after start of engine can be improved. 
   The constitution of a high pressure fuel supply pump according to a second embodiment of the present invention will be described hereinafter with reference to  FIGS. 4 and 5 . 
     FIG. 4  is a vertical sectional view of a high pressure fuel supply pump according to the present embodiment, and  FIG. 5  is a partial enlarged view of  FIG. 4 . In  FIGS. 4 and 5 , the same reference numerals as those of  FIGS. 1 to 3  indicate the same parts. 
   Also in the present embodiment, the pressurizing chamber  12  is provided with the main pressurizing chamber  12   a  and the sub-pressurizing chamber  12   b . The feature of the present embodiment comprises a method of forming the pressurizing chamber  12 . 
   The pressurizing chamber  12  is formed with a cylinder  20  having a sliding portion of a plunger  2  and being a pressurizing chamber forming portion as well, and a fixing member  30  for fixing the cylinder  20 . The inner surface of an upper end portion  20   a  of the cylinder  20  is in a tapered shape, at which the fixing member  30  compresses and holds, whereby the upper end portion  20   a  is deformed outward and fitted in the pump body  1 , as shown in  FIG. 5 , from a state (before deformation) to a state (after changed). Thereby, the pressurizing chamber  12 , the intake passage  5   b  and the discharge passage  6   b  are isolated from the outside the pump by the upper end portion  20   a  of the cylinder, and therefore, a pressurizing chamber can be formed without using an elastic member such as rubber. 
   Accordingly, since an elastic member is not used as in the prior art, no change in volume of the pressurizing chamber caused by movement of the elastic member occurs, even if the pressure in the pressurizing chamber changes and the pressure increasing characteristic of the pump is not lowered. 
   Further, even if an O-ring is disposed, as a backup of seal, on the outer periphery of the fixing member  30 , variation in pressure of the pressurizing chamber is not applied to the O-ring directly since a clearance between the outer circumference of the upper end portion  20   a  of the cylinder and the pump body  1  is very small, thus no rubbing wear or rupture occurs in the O-ring. 
   Further, even if members which are different in linear expansion coefficient are used for the body  1  and the cylinder  20  and even if the upper end portion of the cylinder is tightened up due to thermal contraction, the amount of deformation is scarce since the upper end portion of the cylinder is held by the fixing member  30  and high in rigidity, and no galling or the like due to the deformation of a sliding hole of the plunger  2  occurs. 
   As described above, according to the present embodiment, since low pressure fuel can be supplied to the common rail without impairing piston motion of the high pressure pump when the engine starts, the fuel supply property to the common rail immediately after start of the engine can be improved, and the pressure increasing characteristic of the high pressure fuel supply pump can be improved. 
   Now, the constitution of a high pressure fuel supply pump according to a third embodiment of the present invention will be described with reference to  FIG. 6 . 
     FIG. 6  is a partial enlarged view showing a vertical sectional view of a high pressure fuel supply pump according to the present embodiment. The whole constitution of the high pressure fuel supply pump is similar to that shown in  FIG. 4 . The same reference numerals as those of  FIGS. 1 to 5  indicate the same parts. 
   Also in the present embodiment, the pressurizing chamber  12  is provided with the main pressurizing chamber  12   a  and the sub-pressurizing chamber  12   b . The feature of the present embodiment comprises a method of forming the pressurizing chamber  12 , which is the other example of those shown in  FIGS. 4 and 5 . 
   In the present embodiment, the periphery of the pressurizing chamber comprises a member for forming a pressurizing chamber  21  which is a member different from the cylinder  20 . An upper end portion  21   a  of the pressurizing chamber forming member  21  has a function similar to that of the upper end portion  20   a  of the cylinder shown in  FIG. 5 . 
   According to the present embodiment, further, it is possible to suppress deformation of a sliding hole of a plunger of the cylinder  20 . 
   In examples shown in  FIGS. 4 to 6 , the outer circumference of the fixing member  30  is formed with threads which are threadedly engaged, to thereby exert compressive force on the cylinder  20 , but not limiting to the threads. 
   As described above, according to the present embodiment, since low pressure fuel can be supplied to the common rail without impairing piston motion of the high pressure pump when the engine starts or the like, the fuel supply property to the common rail immediately after start of the engine can be improved, and the pressure increasing characteristic of the high pressure fuel supply pump can be improved. 
   According to the present embodiment, the fuel supply property to the common rail immediately after start of the engine can be improved. 
   Further, the pressure increasing property to the common rail immediately after start of the engine in the high pressure fuel supply pump can be improved. 
   In the following, the constitution of a seal mechanism of a high pressure fuel supply pump according to one embodiment of the present invention will be descried with reference to  FIGS. 7 to 10 . 
   First, the whole constitution of a fuel injection system using a high pressure fuel supply pump according to the present embodiment will be described with reference to  FIG. 7 . 
   Fuel in a tank  50  is guided to a fuel intake passage  110  of a pump body  100  by a low pressure pump  51 . At that time, the fuel guided to the fuel intake passage  110  is regulated to a fixed low pressure by means of a pressure regulator  52 . At this time, fuel pressure is regulated, for example, to 0.3 MPa in relative pressure in association with the atmospheric pressure as a reference. The fuel guided to the pump body  100  is pressurized by the pump body  100 , and is fed under pressure from a fuel discharge passage  111  to the common rail  53 . Pressure of fuel discharged from the fuel discharge passage  111  is pressurized, for example, to 7 to 10 MPa in relative pressure in association with the atmospheric pressure as a reference. 
   On the common rail  53  are mounted with an injector  54 , a relief valve  55 , and a pressure sensor  56 . The injector  54  is mounted while adjusting its number with the number of cylinders of the engine, and injects a fixed quantity of fuel at fixed timing in accordance with a signal of an engine control unit (ECU). The relief valve  56  opens when pressure in the common rail  53  exceeds a fixed value to prevent breakage of a piping system. 
   The schematic constitution of the pump body  100  will be described below. The detailed constitution of the pump body  100  will be described later with reference to  FIG. 8 . 
   The pump body  100  is provided with a fuel intake passage  110 , a fuel discharge passage  111 , and a pressurizing chamber  112 . The fuel intake passage  110  and the fuel discharge passage  111  are provided with an intake valve  105  and a discharge valve  106 , respectively, which are held in one direction by springs  105   a  and  106   a , respectively, in the form of a check valve for limiting a flowing direction of fuel. 
   A plunger  102  is supported to be capable of being reciprocated and slidably moved within a cylinder  108 . A pressurizing chamber  112  is formed between an upper portion in the cylinder  108  and an end of the plunger  102 . 
   In the outer peripheral portion of the plunger  102  is provided with a seal material  120  fabricated of an elastic substance to prevent fuel in the pump from flowing out to the outside. The outer peripheral portion of the seal material  120  is secured to the cylinder  108 . The inner peripheral portion of the seal material  120  slidably holds the plunger  102 . 
   The plunger  102  is reciprocated whereby the volume in the pressurizing chamber  112  is varied. When the intake valve  105  is closed during the compression stroke of the plunger  102 , pressure in the pressurizing chamber  112  rises whereby the discharge valve  106  is automatically opened to feed fuel under pressure to the common rail  53 . While the intake valve  105  is automatically opened when pressure of the pressurizing chamber  112  gets lower than that of the fuel introducing port, closing of valve is decided by operation of a solenoid  130  controlled by ECU  60 . 
   The solenoid  130  is mounted on the pump body  100 . The solenoid  130  is provided with an engaging member  131  and a spring  132 . The engaging member  131  is applied, when the solenoid  130  is turned OFF, with biasing force in a direction of opening the intake valve  105  by means of a spring  132 . Since the biasing force of the spring  132  is greater than that of an intake valve spring  105   a , when the solenoid  130  is turned OFF, the intake valve  105  is in the open state. 
   Energization to the solenoid is limited so that where high pressure fuel is supplied from the pump body  100 , the solenoid  130  is in the On (energization) state, and where a supply of fuel is stopped, the solenoid  130  is in the OFF (deenergization) state. When the solenoid  130  maintains the ON (energization) state, electromagnetic force in excess of biasing force of the spring  132  is generated to draw the engaging member  131  towards the solenoid  130  so that the engaging member  131  is separated from the intake valve  105 . In this state, the intake valve  105  is in the form of an automatic valve to be opened and closed in synchronism with reciprocating motion of the plunger  102 . Accordingly, during the compression stroke, the intake valve  105  is closed, and fuel for a portion reduced in volume in the pressurizing chamber  112  pushes to open the discharge valve  106  and is fed under pressure to the common rail  53 . 
   On the other hand, when the solenoid  130  maintains OFF (deenergization) state, the engaging member  131  is engaged with the intake valve  105  by the biasing force of the spring  132  to hold the intake valve  105  in the open state. Accordingly, since also in the compressions stroke, pressure of the pressurizing chamber  112  maintains the low pressure state substantially equal to that of the fuel introducing port, the discharge valve  106  cannot be opened, and fuel for a portion reduced in volume of the pressurizing chamber  112  is returned to the fuel introducing port side passing through the intake valve  105 . 
   Further, if in the midst of the compression stroke, the solenoid  130  is turned into an ON state, fuel is fed under pressure to the common rail  53  from that time. Further, if pressure feeding is once started, pressure in the pressurizing chamber  112  rises, and therefore, even if the solenoid  130  is turned into an OFF state, the intake valve  105  maintains its closed state, and is automatically opened in synchronism with the start of the intake stroke. 
   Further, according to the present embodiment, a space  107  on the fuel chamber side of the seal material  120  is connected to the fuel intake passage  110  through a connecting passage  109  and a check valve  113 . The check valve  113  is provided so as to control a flowing direction of fuel from the fuel intake passage  110  side to the fuel chamber side space  107 . In the state in which the check valve  113  is opened, low pressure (for example, pressure higher by 0.3 MPa than the atmospheric pressure) supplied to the fuel intake passage  110  is applied to the fuel chamber side space  107  of the seal material  120 . 
   Accordingly, fuel passing through a gap between the cylinder  108  and the plunger  102  from the pressurizing chamber  112  in the pressurizing stroke can flow into the fuel intake passage  110  side which is a low pressure portion, and pressure on the fuel chamber side of the seal material  120  is equal to that of the fuel intake passage  110  to enable prevention of an external leakage of fuel without considerably increasing the rigidity of the seal material  120 . 
   On the other hand, when the seal material  120  is broken or fallen off so that fuel begins to leak outside, pressure of the fuel chamber side space  107  is lower than that of the fuel intake passage  110  side, whereby the check valve  113  is closed to prevent an inflow of fuel from the fuel intake passage  110  side. Therefore, only the fuel passing through the gap between the cylinder  108  and the plunger  102  from the pressurizing chamber  112  flows into the seal material  120  portion. This flow-rate is in inverse proportion to the length of the sliding portion between the cylinder  108  and the plunger  102 , and if the distance for which the plunger  102  can slidably move adequately is secured as in the present embodiment, the flow-rate can be suppressed to a small quantity. Accordingly, even when the seal material  120  is broken or fallen off, it is possible to prevent a large quantity of fuel from flowing out in a short period of time. 
   Further, since as described above, the outflow of fuel from the pressurizing chamber  112  through the gap of the plunger sliding portion is minimized, the discharge efficiency of the pump can be enhanced during the normal operation. 
   The construction of the high pressure fuel supply pump according to the present embodiment will be described with reference to  FIG. 8 . 
     FIG. 8  is a longitudinal sectional view showing the constitution of a high pressure fuel supply pump according to one embodiment of the present invention. The same reference numerals as those of  FIG. 7  designate the same parts. 
   The pump body  100  is provided with a fuel intake passage  110 , a fuel discharge passage  111 , and a pressurizing chamber  112 . The fuel intake passage  110  and the fuel discharge passage  111  are provided with an intake valve  105  and a discharge valve  106 , respectively, which are held in one direction by springs  105   a  and  106   a , respectively, to limit a flowing direction of fuel serving as a check valve. 
   A plunger  102  as a pressurizing member is slidably held in a pressurizing chamber  112  formed interiorly of a cylinder  108 . The pressurizing chamber  112  is formed by the cylinder  108  having a sliding hole  108   a  for supporting the plunger  102  to be capable of being reciprocated and slidably moved. The inside diameter portion of the cylinder  108  comprises a sliding hole  108   a  whose diametral gap relative to the plunger  102  is equal to or smaller than 10 μm in order to minimize a leakage of fuel from the pressurizing chamber, and a large-diameter inner wall  108   b  formed to have a large diameter in order to form the pressurizing chamber. 
   The cylinder  108  is held by press-fitting a part of an outer wall  108   c  corresponding to the large diameter inner wall  108   b  into the body  1 . Thereby, deformation in dimension of the inside diameter of cylinder caused by the press-fitting occurs only in the large diameter inner wall portion  108   b , and the sliding hole  108   a  can maintain a dimensional state processed in advance. Accordingly, finish-processing of the sliding hole  108   a  after the press-fitting is unnecessary, and a material having a good abrasion resistance may be selected merely for the sliding portion, thus reducing the cost. Even if materials different in linear expansion coefficient are used for the body  1  and the cylinder  108 , deformation in inside diameter of cylinder caused by change in temperature occurs merely in the large diameter inside wall  108   b , thus not exerting a bad influence on the sliding property of the plunger  2 . 
   An annular passage  109  is provided between the cylinder  108  and the pump body  1 , the annular passage  109  being communicated with the sliding hole  108   a , and the intake passage  110  in communication with a fuel introducing port  110   a  and the annular passage  109  are communicated by a passage  109   b . Thereby, since pressure in the annular passage  109  is substantially the same pressure (atmospheric pressure +0.3 MPa) as that of the introducing port  110   a , a pressure difference from the pressurizing chamber  112  is reduced, so that a leakage of fuel from a pressing-in portion  108   c  and the sliding hole  108   a  can be reduced. Heat generation at the sliding portion can be cooled by fuel, and seizure of the sliding portion can be prevented. 
   A seal material  120  fabricated from an elastic substance is provided on the outer peripheral portion of the plunger  102  in order to prevent fuel in the pump from flowing out and to prevent oil for lubricating a cam  140  from flowing into the pump. In the present embodiment, the seal material  120  is formed integrally with a metal tube  120   a  and is press-fitted in the pump body  100 , but a method of fixing the seal material  120  is not limited to the above method. An end of the metal tube  120   a  formed integrally with the seal material  120  is fitted in the pump body  100 . A leakage of fuel from the sliding portion between the plunger  102  and the seal material  120  can be reduced by extending length of the seal material  120 . Since pressure on the fuel chamber side of the seal material  120  is the pressure of low pressure fuel (which is, for example, higher than the atmospheric pressure by 0.3 MPa), and pressure on the other side of the seal material  120  is the atmospheric pressure, a pressure difference between both end surfaces of the seal material  120  is small, for example, 0.3 MPa, and therefore, sealing property can be enhanced even if the full length of the seal material  120  is not so much prolonged. 
   A lifter  103  provided on the lower end of the plunger  102  is pressed against a cam  140  by means of a spring  104 . The plunger  102  is reciprocated by the cam  140  rotated by an engine cam shaft or the like to change the volume in the pressurizing chamber  112 . When the intake valve  105  is closed during the compression stroke of the plunger  102 , pressure in the pressurizing chamber  112  rises whereby the discharge valve  106  is automatically opened to feed fuel under pressure to the common rail  53 . While the intake valve  105  is automatically opened when pressure of the pressurizing chamber  112  is lower than that of the fuel introducing port, closing of valve is decided by operation of a solenoid  130 . 
   The solenoid  130  is mounted on the pump body  100 . The solenoid  130  is provided with an engaging member  131  and a spring  132 . The engaging member  131  is applied, when the solenoid  130  is turned OFF, with biasing force in a direction of opening the intake valve  105  by a spring  132 . Since the biasing force of the spring  132  is greater than that of an intake valve spring  105   a , the intake valve  105  is in the open state when the solenoid is turned OFF as shown in the figure. 
   Energization to the solenoid  130  is limited so that where high pressure fuel is supplied from the pump body  100 , the solenoid  130  is turned into the ON (energization) state, and where a supply of fuel is stopped, the solenoid  130  is turned into the OFF state (deenergization). 
   When the solenoid  130  holds the ON (energization) state, electromagnetic force greater than the biasing force of the spring  132  is generated to draw the engaging member  131  toward the solenoid  132 , and therefore, the engaging member  131  is separated from the intake valve  105 . In this state, the intake valve  105  takes the form of an automatic valve which is opened and closed in synchronism with reciprocation of the plunger  102 . Accordingly, during the compression stroke, the intake valve  105  is closed, and fuel for a portion reduced in volume of the pressurizing chamber  112  pushes to open the discharge valve  106  and is fed under pressure to the common rail  53 . 
   On the other hand, when the solenoid  130  holds the OFF (deenergization) state, the engaging member  131  is engaged with the intake valve  105  by the biasing force of the spring  132  to hold the intake valve  105  in the open state. Accordingly, even in the compression stroke, since pressure of the pressurizing chamber  112  keeps the low pressure state substantially equal to that of the fuel introducing port, the discharge valve  106  cannot be opened, and fuel for a portion reduced in volume of the pressurizing chamber  112  is returned to the fuel introducing port passing through the intake vale  105 . 
   If the solenoid  130  is turned into the ON state in the midst of the compression stroke, fuel is fed under pressure to the common rail  53  from that time on. If feeding under pressure is once started, pressure in the pressurizing chamber  112  rises, and therefore, even if the solenoid  130  is turned into the OFF state later, the intake valve  105  maintains its closed state, and is automatically opened in synchronism with the start of the intake stroke. 
   Further, the pump body  100  is interiorly provided with a longitudinal passage  109   b  connected to the fuel chamber side space  107  of the seal material  120  and a lateral passage  109   a  connected to the longitudinal passage  109   b  to constitute a connecting passage  109  as shown in  FIG. 7 . The longitudinal passage  109   b  is easily formed because it is formed between the outer peripheral portion of the cylinder  108  and a hole formed in the pump body  100  by inserting and fitting the cylinder  108  into the hole formed in the pump body  100 . A check valve  113  is provided on the end of the lateral passage  109   a . The check valve  113  is formed from a ball-like elastic substance. Materials for the check valve  113  to be used are those having gasoline resistance, for example, such as fluorine rubber, nitrile rubber, etc. The check valve  113  is normally in the open state, details of which will be described later with reference to  FIGS. 9 and 10 . As described above, the fuel chamber side space  107  of the seal material  120  is connected to the fuel intake passage  110  through the connecting passage  109  and the check valve  113 . The check valve  113  is provided so as to control a flowing direction of fuel from the fuel intake passage  110  to the fuel chamber side space  107 . In the state in which the check valve  113  is open, low pressure (for example, pressure higher than the atmospheric pressure by 0.3 MPa) supplied to the fuel intake passage  110  is applied to the fuel chamber side space  107  of the seal material  120 . 
   Thereby, fuel passing through a gap between the cylinder  108  and the plunger  102  from the pressurizing chamber  112  in the pressurizing stroke can flow into the fuel intake passage  110  side which is a low pressure portion, and therefore, pressure on the fuel chamber side of the seal material  120  is equal to that of the fuel intake passage  110  to enable suppression of an external leakage of fuel without considerably increasing rigidity of the seal material  120 . 
   On the other hand, when the seal material  120  is broken or fallen off so that fuel begins to leak outside, the pressure of the fuel chamber side space  107  is lower than that of the fuel intake passage  110 , and therefore, the check valve  300  is closed to enable prevention of fuel from flowing into from the fuel intake passage  110  side. Therefore, only the fuel passing through a gap between the cylinder  108  and he plunger  102  from the pressurizing chamber  112  flows into the seal material  120  portion. This flow-rate takes in inverse proportion to the length of the sliding portion between the cylinder  108  and the plunger  102 , and therefore, if distance in which the plunger  102  can be slidably moved adequately is secured as in the present embodiment, the flow-rate can be suppressed to a small quantity. Accordingly, even when the seal material  120  is broken or fallen off, it is possible to prevent a large quantity of fuel from flowing out in a short period of time. 
   Further, as described above, since the outflow of fuel in the pressurizing chamber  112  from the gap of the plunger sliding portion is suppressed to the minimum, the discharge efficiency of the pump can be enhanced during normal operation. 
   The construction of a check valve used for a high pressure fuel supply pump according to the present embodiment will be described hereinafter with reference to  FIGS. 9 and 10 . 
     FIG. 9  is a sectional view when a check valve is opened using a high pressure fuel supply pump according to one embodiment of the present invention, and  FIG. 10  is a sectional view when a check valve is closed using a high pressure fuel supply pump according to one embodiment of the present invention. 
   As shown in  FIG. 9 , a check valve  113  formed from a ball-like elastic substance is controlled in movement in a right direction in the figure by an end of a solenoid  130  in order to prevent it from falling off from a lateral passage  109   a . A seat surface  113   a  with which the check valve  113  is engaged to close the valve is formed on the right side end in the figure of the lateral passage  109   a , but is formed perpendicular to the lateral passage  109   a  extending in a horizontal direction, because of which, it forms a substantially vertical surface. In a pump body  100 , the vertical direction as shown in the figure is the top and bottom direction. Accordingly, in the state in which the pump body  100  is mounted in the top and bottom direction, the ball-like check valve  113  is not in contact with the seat surface  113   a , so that when the front and rear pressures of the check valve  113  is equal to each other, it can be turned into the open valve state. 
   A countermeasure to prevent falling-off of the check valve  113  is not limited to the means using the end of the solenoid  130 , but for example, a separate member may be used to prevent the check valve  113  from falling off. Alternatively, the lateral passage  109   a  may be inclined so that the seat surface  113   a  is in the lower direction. Further alternatively, also the seat surface  113   a  is not only to be made substantially vertical but may be inclined. Further, the check valve  113  may be installed not only at the outlet of the lateral passage  109   a  but within the passage. Further, when the seat surface  113   a  forms the horizontal surface, a spring or the like may be interposed between the check valve  113  and the seat surface  113   a  so that when the front and rear pressures of the check valve  113  are equal to each other, the check valve  113  is not closed. 
   As described above, also when the pump is stopped, the check valve  113  is opened to thereby prevent the check valve  113  from being adhered to the seat surface  113   a . Further, since also during operation, the opening valve pressure of the check valve  113  is zero, pressure in the fuel chamber side of the seal material  120  can be made equal to that of the fuel intake passage  110  portion. 
   On the other hand, as shown in  FIG. 10 , when pressure on the fuel chamber side of the seal material  120  is lowered due to the falling off of the seal material  120 , pressure of the lateral passage  109   a  gets lower than the pressure of the fuel intake passage  110 . Therefore, the check valve  113  is pressed against the seat surface  113   a  so that the check valve  113  is promptly closed to prevent fuel from flowing out from the fuel intake passage  110  side. 
   Further, the check valve  113  is formed from an elastic substance whereby hardness of the seat surface  113   a  need not be increased, and it can be fabricated inexpensively. 
   As described above, in the present embodiment, the fuel chamber side space  107  of the seal material  120  is connected to the fuel intake passage  110  to constitute a fuel reservoir to which low pressure (for example, pressure higher by 0.3 MPa than the atmospheric pressure) supplied to the fuel intake passage  110  is applied. That is, the fuel reservoir is not provided within the sliding portion of the plunger, as in the prior art. That is, the pressurizing chamber  112  being high pressure is formed at the upper end in the figure of the cylinder  108 , whereas the fuel chamber side space  107  (fuel reservoir) being low pressure is formed at the lower end in the figure of the cylinder  108 , and therefore, the distance from the pressurizing chamber  112  to the fuel chamber side space (fuel reservoir)  107  can be prolonged so that a leakage of the high pressure fuel of the pressurizing chamber  112  to the fuel chamber side space  107  can be easily reduced. Accordingly, the pump can be miniaturized, and the leakage during pressurizing can be reduced to enhance the discharge efficiency. 
   Further, in the present embodiment, since the passage having substantially atmospheric pressure as in the prior art is not provided on the fuel chamber side of the seal material, processing of such a passage is unnecessary, and piping for connecting from the pump to the fuel tank is also unnecessary. Accordingly, the manufacturing cost is low. 
   Further, the seal material  120  has the construction in which the integrally molded metal pipe  120   a  is secured to the pump body  100 , so that the length of the seal material  120  tends to be prolonged to extend the sliding distance relative to the plunger  102 , thus enabling enhancement of the sealing property, and since pressure applied to both ends of the seal material  120  is low pressure, the sealing property can be enhanced. 
   Further, when the seal material  120  is broken or the like, the check valve  113  provided on the connecting passage  109  for communicating the fuel intake passage  110  with the fuel chamber side space  107  is activated to promptly prevent fuel from leaking from the fuel intake passage  110  to the atmosphere side. 
   Further, since during operation of the pump, the check valve  113  is in the open state, it is possible to easily prevent the check valve from adhering to the seat surface. 
   According to the present embodiment, even when the seal material of the sliding portion is broken or fallen off, an external leakage of fuel can be suppressed to a small quantity, as well as being small in size and inexpensive. 
   While some embodiments have been described, the characteristic constitution common to these embodiments will be further explained in detail hereinafter with reference to  FIG. 11 . 
   A pump body  1  is formed with a fuel intake passage  10 , a discharge passage  11 , and a pressurizing chamber  12 . A plunger  2  as a pressurizing member is slidably held on the pressurizing chamber  12 . The intake passage  10  and the discharge passage  11  are formed with an intake chamber  5 A and a discharge chamber  6 A, respectively, leading to an intake hole  5   b  and a discharge hole  6   b , respectively, of the pressurizing chamber  12 , the respective chambers being provided with an intake valve  5  and a discharge valve  6 . The intake valve  5  and the discharge valve  6  are held in one direction by springs  5   a  and  5   a , respectively, to constitute a check valve for restricting a flowing direction of fuel. More specifically, the intake valve  5  is biased by spring  5   a  so as to close a hole  5 Aa from the inside of the inlet hole  5 Aa of the intake chamber  5 A. A solenoid  200  as an electromagnetic driving device is pressed and held in a tubular casing portion  1 A formed integrally with the pump body  1 , the solenoid  200  being provided with an engaging member  201  formed as a plunger rod, and a spring  202 . When the solenoid  200  is turned OFF, the engaging member  201  is guided to a projecting position by the spring  202 , as a consequence of which, it is engaged with the intake valve  5  to bias it in a direction of opening the valve. Since biasing force of the spring  202  is set to be greater than that of the spring  5   a  for biasing the intake valve  5  in a closing direction, when the solenoid  200  is turned OFF, the intake valve  5  is pushed to open by the engaging member  201  to assume the open state. Fuel is guided by the low pressure pump  51  from the tank  50  to the fuel introducing port of the pump body  1 , and is regulated to a fixed pressure by the pressure regulator  52 . Thereafter, fuel is pressurized by the pump body  1  and fed under pressure from the fuel discharge port  11  to the common rail  53  in  FIG. 7 . 
   The operation of the high pressure pump constituted as described above will be described hereinafter. 
   The lifter  3  provided at the lower end of the plunger  2  is pressed against the cam  100  by the spring  4 . The plunger  2  is reciprocated by the cam  100  rotated by an engine cam shaft or the like to change the volume in the pressurizing chamber  12 . 
   When the intake valve  5  is closed during the compression stroke of the plunger  2 , pressure in the pressurizing chamber  12  rises whereby the discharge valve  6  is automatically opened to feed fuel under pressure to the common rail  53 . 
   The intake valve  5  is automatically opened when pressure of the pressurizing chamber  12  gets lower than that of the fuel introducing port, but closing of valve is decided according to operation of the engaging member  201  of the solenoid  200 . 
   When the solenoid  200  keeps the ON (energization) state, electromagnetic force in excess of biasing force of the spring  202  is generated, the engaging member  201  is drawn to the solenoid  202  side to assume a returning position, at which point of time the engaging member  201  is separated from the intake valve  5 . In this state, the intake valve  5  works as an automatic valve which is opened and closed by a pressure difference between upstream and downstream of the intake valve  5  in synchronism with the reciprocation of the plunger  2 . Accordingly, during the compression stroke, the intake valve  5  is closed, and fuel for a portion reduced in volume of the pressurizing chamber  12  pushes to open the discharge valve  6  and is fed under pressure to the common rail  53 . Thereby, the maximum discharge of the pump can be carried out irrespective of the respondence of the solenoid  200 . 
   On the other hand, when the solenoid  200  is in the OFF (deenergization) state, the engaging member  201  is engaged with the intake valve  5  by biasing force of the spring  202  to hold the intake valve  5  in the open state. Accordingly, fuel in the cylinder (in the pressurizing chamber) is returned through the through hole  5 Aa opened during the compression stroke so that pressure of the pressurizing chamber  12  keeps the low pressure state substantially equal to the fuel introducing port, because of which, the discharge valve  6  cannot be opened. Thereby, the pump discharge quantity can be made zero. 
   If the solenoid  200  is turned into the ON state in the midst of the compression stroke, the intake valve  5  which has lost biasing force in the opening direction caused by the engaging member  201  to momentarily close the through hole  5 Aa by the spring  5   a  and the pressure of the pressurizing fuel. Accordingly, the discharge valve  6  is opened, from that time on, to feed fuel under pressure from the discharge hole  11  to the common rail  53 . If pressure feeding is once started, pressure in the pressurizing chamber  12  rises till next intake stroke takes place, and therefore, even if the solenoid  200  is turned into the OFF state later, the intake valve  5  maintains its closed state till next intake stroke starts. When the intake stroke starts, pressure in the pressurizing chamber gets lower than that of the low pressure passage so that the intake valve  5  is automatically opened. Thereby, the discharge quantity can be adjusted according to ON timing of the solenoid  200  (that is, drawing timing of the engaging member). Since the engaging member of the solenoid  200  may be returned to the projecting position (that is, the position when the solenoid is turned OFF) before the compression stroke starts, the high speed respondence of the engaging member  201  is not required. Thereby, biasing force of the spring  202  can be made small, and as a consequence, the OFF-ON respondence of the solenoid  200  (that is, the projection-drawing respondence of the engaging member) can be improved. 
   Importantly, being different from the conventional electromagnetic driving valve, since the solenoid will suffice to draw the plunger rod only, the movable portion becomes light, from which point, the respondence is improved. Driving can be made by a small solenoid. 
   Further, since the valve body is not strongly knocked against the seat by electromagnetic attraction different from the electromagnetic valve, no damage possibly occurs. 
   The ON time or ON timing of the solenoid  200  in the compression stroke is controlled whereby the discharge quantity to the common rail  53  can be controlled variably. Further, adequate discharge timing is computed by the ECU on the basis of a signal of a pressure sensor  56  to control the solenoid  200 , whereby pressure of the common rail  53  can be maintained at substantially constant value. Further, the OFF-ON respondence can be enhanced without making the solenoid  200  larger in size. 
   Next, modifications of the intake valve  5 , the engaging member  201 , and the valve body will be described with reference to  FIGS. 12 to 14 . In these embodiments, either of the intake valve  5  and the engaging member  201  is made to be a concave shape, while the other is made to be a convex shape so that the concavo-convex engagement is provided. With this constitution, it is possible to prevent the engaging portion from being displaced and/or slipped off, and the secure operation of the intake valve  5  and the engaging member  201  can be carried out. While in the present embodiment, the shape of the intake valve  5  is in the form of a ball valve and a cylindrical valve, it is noted that a conical valve, a reed valve or the like can be also employed. 
   In  FIGS. 12 and 13 , a position of the intake valve  5  upon opening is decided by a stopper  201   a  portion provided on the engaging member  201 . With this, since set load of the spring  202  can be maintained constant, attraction speed (valve-closing respondence) of the engaging member  201  can be stabilized. Accordingly, control of the valve-closing timing is made easy. 
   Further, in  FIG. 14 , a position of the intake valve  5  upon opening is decided by a stopper  5   b  portion provided on the intake valve  5 . With this constitution, since a positional relationship between the intake valve  5  and the seat portion can be made constant, passage resistance when the valve is opened can be made constant as well. Accordingly, the opening stroke of the intake valve  5  need not be made greater than that is needed to provide miniaturization. 
   The position of the stopper can be selected according to the required content of the pump. 
   Returning to  FIG. 8 , a further detailed embodiment will be described. In the present embodiment, a ball valve is used for the discharge valve  106 , and a cylindrical member  106   c  held for reciprocation and sliding movement in a discharge passage  111  is placed in engagement therewith by means of a spring  106   a . By doing so, the respective members can be easily fabricated, and the ball valve  106  can be securely held, and oscillations or the like of the ball valve caused by the fuel flow when the valve is opened can be suppressed. Further, it is also possible for holding the ball valve more securely to integrate the cylindrical member  106   c  with the ball valve  106  by welding or the like. These constructions can be also used in the intake valve. 
   The capacity variable mechanism will be described in further detail with reference to  FIGS. 15 and 16 . An annular recess portion  5 B is formed at a part upstream of an intake hole  5   b  of the pump body  1 . 
   An outer peripheral portion of one end of a holder  5 C for accommodating an intake valve  5  is spigot-fitted in the annular recess  5 B, both of which are fixedly pressed in. On the intake hole  5   b  side of the holder  5 C are bored with five through-holes  5 D as shown in  FIGS. 17 and 18 . 
   A spring  105   a  ( 5   a ) is retained in the center of the holder  5 . On the intake hole ( 5   b ) side of the spring  105   d  ( 5   a ), a cup-shaped valve  105  ( 5 ) shown in  FIGS. 19A and 19B  is mounted so as to surround the spring  105   a  ( 5   a ). 
   The pump body  1  is further formed with an annular chamber  110 A larger in diameter than that of the annular recess  5 B. As a consequence, the chamber  110 A forms an intake chamber in communication with a low pressure fuel passage  110 . 
   The pump body  1  is further formed with an annular cavity  130 B with a threaded groove  130 A larger in diameter than that of the annular chamber  110 A. 
   A solenoid  200  ( 130 ) constituting an electromagnetic driving mechanism is mounted on the annular cavity  130 A. 
   An adaptor  200 A formed with threads  200   a  is mounted on the outer periphery of the solenoid  200  ( 130 ), and the threads are engaged into the threaded groove of the cavity  130 A whereby the solenoid is mounted on the cavity  130 A. 
   Numeral  200   b  designates a seal ring, which isolates the fuel intake chamber  110 A from outside air. 
   An annular electromagnetic coil  200 B is accommodated in a closed-end cup-shaped outer core  200 D. A hollow tubular internal fixed core  200 C is inserted into the center of the annular electromagnetic coil  200 B. A disk-like radial-direction core portion  200 E is formed integrally with one side end of the hollow tubular internal fixed core  200 C, and the outer circumference of the diametral-direction core is secured to the inner peripheral wall on the open end side of the cup-like outer core  200 D by tension-connection. The electromagnetic coil  200 B comprises an annular bobbin  200   c  through which the internal fixed core  200 C, a coil  200   d  wound therearound, and a molded resin outer layer  200   f  in which the outer periphery of the coil  200   d  is subjected to molding with resin. 
   The annular electromagnetic coil  200 B is accommodated in a state of being axially pressed between the inner bottom of the cup-shaped outer core  200 D and the disk-like radial-direction core portion  200 E. A seal ring  200   g  is put in a cavity facing to the bobbin  200   c , the resin outer layer  200   f  and the inner fixed core  200 C. A seal ring  200   h  is put in a cavity facing to the resin outer layer  200   f , the radial-direction core portion  200 E and the cup-shaped outer core  200 D. 
   The open end side of the cup-shaped outer core  200 D is sealed by resin mold so as to cover the outside of the radial-direction core portion  200 E, and at that time, an outer removing terminal of the electromagnetic coil  200 B is also molded together to form a connector  200 F. 
   The P portion circled in  FIG. 15  will be described in more detail in an enlarged scale in  FIG. 16 . 
   A portion  230  of the bottom of the closed-end cup-shaped outer core  200 D has a through hole  231  in the center thereof. 
   An annular recess  232  is formed continuously to the outside of the through hole  231 . The diameter of the annular recess  232  is larger than that of the through hole  231 . 
   A movable core  131   a  is inserted into the through hole  231 . An engaging member  201  in the form of a plunger rod is formed integrally with the movable core  131   a.    
   An annular movable stopper  201   c  is also formed integrally at a longitudinal intermediate position of the engaging member  201 . A C ring-like fixed stopper member  233  is fitted, between the stopper  201   c  and the movable core  131   a , into the rod portion of the engaging member  201  in the radial direction using a cut groove. In this state, the movable core  131   a  is inserted into the through hole  231 , the fixed stopper member  233  is pressedly fixed into the annular recess  232 , and the movable core  131   a  and the engaging member  201  are mounted on the solenoid  200  in such a manner of extending through the bottom portion  230  of the outer fixed core  200 D. 
   Further, a guide member  220  is press-fitted in the annular recess  232  so as to hold a C-ring fixed stopper  233 . 
   The guide member  220  is formed with a stopper surface  221  facing to the stopper surface  233   a  of the fixed stopper  233 , and a movable stopper  201 C can be reciprocated by stroke Ss=45 micron between these two stopper surfaces. 
   The guide  220  is bored in the center with a guide hole  220   b . The engaging member  201  extends through the guide hole  220   b  to thereby control the radial movement for reciprocation along the center axis of the solenoid  200 . 
   The guide  220  is bored with a plurality of through holes  220 C in a radial direction. The through holes  220 C are communicated with a low pressure fuel passage around the guide  220 . 
   The through holes  220 C are connected to a center hole  220 A of the guide  220 . The center hole  220 A is open ( 220 B) to the axial end of the guide  220 , and an end surface  220   a  around the opening  220 B forms a seat surface of the intake valve  105  ( 5 ). 
   As a consequence, as shown in  FIG. 15 , in the state in which the solenoid  200  ( 130 ) is mounted on the pump body  1 , the outer periphery of the axial-direction end surface of the guide  220  comes in pressure contact with the end surface of the holder  5 C, both of which constitute an intake valve mechanism. 
   In addition, in the engaging member  201 , a metal ball is secured to the end of the plunger rod portion by welding. 
   The cup-shaped movable core  131   a  accommodates internally a spring  202  ( 132 ), and one side end of the spring  202  ( 132 ) is in contact with the end surface of an adjust screw  200 G threadedly fitted in the center of a fixed core  200 C in the center side. 
   The adjust screw  200 G adjusts a set load of the spring  202  ( 132 ) to adjust properties of moving operation of the engaging member  201 . 
   The spring  202  ( 132 ) biases the movable core  131   a  and the engaging member  201  ( 131 ) in the direction opposite to the adjuster  200 G, and as a result, the stopper surface  201   a  of the stopper  201   c  comes in contact with the stopper surface  221  of the guide member  220 . 
   As a result, the ball member  210  at the end of the engaging member  201  ( 131 ) projects by dimension of Sg=35 micron from the end  220   a  of the guide  220 . At that time, the ball member  210  causes the valve body  105  ( 5 ) to levitate by dimension of Sg=35 micron from the seat surface of the guide member  220  against the force of the spring  105   a  ( 5   a ) to connect the opening  220 B to the intake hole  5   b  of the cylinder through five holes  5 D of the holder  5 C. 
   The axial end surface of the movable core  131   a  faces away by a gap Ga from the axial-direction end surface of the inner fixed core  200 C. On the other hand, the outer peripheral surface of the movable core  131   a  faces through a slight diametral gap to the inner peripheral surface of the through hole  231  of the outer fixed core  200 D. 
   As a result, when power is supplied (that is, energization) from a connector  200 F to a coil  200 B, there is formed a closed magnetic path passing through the outer fixed core  200 D, the movable core  131   a , the inner fixed core  200 C and the disk member  200 E. 
   As a result, magnetic attraction is generated between the opposing end of the movable core  131   a  and the inner fixed core  200 C. 
   This magnetic attraction draws the movable core  131   a  toward the inner fixed core  200 C against the force of the spring  132 . 
   The stroke of the movable core  131   a  terminates at a position where the stopper  201   c  of the engaging member  201  comes in contact with the stopper surface  233   a  of the fixed stopper  233 . Its distance is Ss=45 micron. 
   At the end of stroke of the movable core  131   a , a gap Ga between the movable core  131   a  and the end surface of the inner fixed core  200 C is 6 micron. 
   A non-magnetic ring  133  is secured to the inner periphery of the movable core  131   a , a portion projecting from the movable core  131   a  of the non-magnetic ring  133  is guide to the inner peripheral surface of the inner fixed core  200 . As a result, the radial movement of the movable core  131   a  is controlled. 
   Thus, the engaging member  201  and the movable core  131  are guided at two places distanced each other in the axial direction to enable the stable movement. 
   After all, as a result of the stroke of the movable core  131   a , the ball member  210  at the end of the engaging member  201  ( 131 ) is held at a position withdrawn by dimension of Sa=10 micron from the seat surface  220   a  of the guide member  220 . 
   At that time, the intake valve  105  ( 5 ) is disengaged from the ball member  210  and is pressed against the seat surface  220   a  of the guide member  220  by the force of the spring  105   a  ( 5   a ). As a result, the intake valve  105  ( 5 ) closes the center opening  220 B of the guide member  220  to intercept between the low pressure fuel passage and the holder  5 . 
   The intake valve  105  ( 5 ) is formed in a cup-shape, as shown in  FIGS. 19A and 19B , and is held in the state of being put around the spring  105   a  ( 5   a ). 
   The axial-direction end surface to be the seal surface has a circular convex portion  105 A whose center comes in contact with the ball member  210 , and an annular convex portion  105 B in contact with the seat surface  220   a  of the guide  220 . An annular groove  105  is formed between both the convex portions. 
   Both the convex portions are subjected to cutting so that their heights are the same. 
   Since the seat surface is constituted by the annular convex portion  105 B, one-sided abutment with the seat surface on the guide member side is reduced so that the contact therebetween becomes tight to enhance the seat property. The intake valve  105  ( 5 ), the guide member  220  and the ball member  210  impinge upon one another, the number of times of which extends to a million during the service life of the internal combustion engine. Allowable abrasion of these members under these conditions is only in order of 10 micron. Particularly, when the contact portion between the intake valve  105  ( 5 ) and the ball member  210  becomes worn by 35 micron, even if the movable core  131   a  and the engaging member  201  ( 131 ) stroke by 45 micron, the intake valve  105  ( 5 ) cannot be levitated from the seal surface. That is, in such a state as described, the opening valve state of the intake valve  105  ( 5 ) cannot be maintained, and control of capacity cannot be accomplished. Then, it has been found as a result of various studies of conditions less in abrasion that use of material having hardness equal to or more than 30 H RC  in Vickers hardness scale is preferable. More specifically, it has been found that as a material to satisfy with this condition, stainless steel SUS440C as set forth in Japanese Industrial Standard (JIS) is advantageous. 
   On the other hand, since the movable core  131   a  and the plunger rod portion of the engaging member  201  ( 131 ) constitute a magnetic path, material need be a magnetic material, from a viewpoint of which it has been found that the magnetic stainless steel SUS420J2 as set forth in Japanese Industrial Standard (JIS) is advantageous. 
   Thus, in the deenergization state of the coil of the solenoid  200  ( 130 ), it can be set so that the force of the spring  132  overcomes the force of the spring  105   a  ( 5   a ), and the engaging member  201  ( 131 ) strokes by 35 micron to levitate the intake valve  105  ( 5 ) from the seat surface. 
   In the present embodiment, since the ball member  210  is separated from the plunger rod portion, materials matching with the respective functions can be used. 
   Where the movable core  131   a  and the plunger rod portion of the engaging member  201  ( 131 ) are formed separately of different materials, and then are integrated by post-processing through a method such as welding or tension bonding, it is possible that the plunger rod portion and the ball member can be formed integrally. In this case, the ball portion, the plunger rod portion and the stopper portion are cut out from the same member by cutting. 
   The ball member not always need be spherical. The joining surface with the engaging member  201  ( 131 ) may be flat. Therefore, the ball member may be a hemisphere. 
   In the present embodiment, the engaging member is formed at its end with an annular recess, into which a part of a spherical member is embedded and held, and the contact surfaces thereof are welded for joining, and therefore, the joining work is very easy, and the centers of the ball member and the engaging member tend to be registered. 
   In the present embodiment, mounting of an intake valve mechanism having a variable capacity function is completed merely by press-fitting the valve holder  5 C into the recess  5 B of the pump body  1 , and screwing the solenoid  200  ( 130 ) assembled separately into the recess portion  130 B with a threaded groove, thus achieving the good workability. 
   Reference numeral  200   e  designates a foam escaping hole. Where vapor is generated in the low pressure fuel passage due to heat of the engine, the foam is temporarily protected in an annular cavity  200   i  passing through the foam escaping hole  200   e  to prevent the vapor entering the pressurizing chamber in the cylinder  8  passing through the intake valve  105  ( 5 ). 
   In the description of the present embodiment, the entirety including the movable core, the plunger rod portion and the ball member is called, macrowise, the engaging member. However, the movable core may also be formed from a separate member, and it may sometimes be necessary to be distinguished from the movable core in functionality. In some passages, the plunger rod portion and the ball member portion have been explained as the engaging member taking the above into consideration. 
   In the present embodiment, the valve body is completely separated from the electromagnetic driving mechanism, from which point, the present embodiment is exactly different in constitution and operation from the variable capacity mechanism by way of an electromagnetic valve (a valve being secured to the driving mechanism) in the prior art. 
   Since extra attraction of the driving mechanism after the contact of the valve body with the seat is completed does not exert on the valve body, the valve body and the seat surface are less worn, and no mechanical stress acts between the valve body and the plunger of the driving mechanism. The force involved in opening operation of the valve body when the valve body is opened due to a pressure difference between upstream and downstream of the valve body is only the spring force for generating a valve closing force, making the movement quick. 
   In the prior art of the electromagnetic valve system, not only the valve body but also the plunger of the driving mechanism and the movable core need to move together, and it is necessary to make great by what is required for the force of the spring (which exerts in a valve opening direction) on the side of the electromagnetic driving mechanism, and as a result, when driving to the closing side, a great force is necessary whereby the electromagnetic mechanism becomes large. 
   Further, the movement of the valve body itself also becomes dull. 
   For the reasons mentioned above, in the present embodiment, despite the fact that the valve body and the electromagnetic plunger are independent thereof, the present embodiment should be clearly distinguished from the prior art electromagnetic valve system. 
   According to the further characteristic constitution, the intake opening ( 220   a ) opened and closed by the intake valve  105  ( 5 ) is formed on the side of the electromagnetic driving mechanism. 
   This is the very important constitution in controlling the stroke of the plunger rod as the engaging member  201  ( 131 ) on the basis of the seat surface on which the intake valve seats. 
   That is, this provides the merit capable of independently adjusting and inspecting the seat surface and the stroke of the engaging member before incorporating them into the pump body. 
   In the present embodiment, the relation between the seat surface of the intake valve and the stroke of the engaging member exactly remains unchanged even after the electromagnetic driving mechanism has been incorporated into the pump body.