Abstract:
The objective of the present invention is to dampen operating sounds of an electromagnetic drive mechanism used for a variable displacement control mechanism in a high-pressure fuel supply pump to reduce an individual difference depending on apparatus due to the change over time or installation tolerance. To achieve the above objective, the present invention is configured such that before the electromagnetic drive mechanism supplies a drive force to a plunger which is electromagnetically driven by the electromagnetic drive mechanism, another displacement force situates the plunger in a specific position. When compared to an occasion where the plunger is displaced all strokes by a magnetic biasing force, the above configuration is able to reduce the force of impact on a member (for example, valve body) mounted to the plunger and a restricting member, thereby damping the collision noise. Furthermore, since an extra member, such as a damping member, is not required, individual difference depending on apparatus do not easily occur.

Description:
CLAIM OF PRIORITY  
       [0001]     The present application claims priority from Japanese application serial No. 2005-069668, filed on Mar. 11, 2005, the contents of which is hereby incorporated by references into this application.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an electromagnetic drive mechanism, and specifically to a high-pressure fuel supply pump for an internal combustion engine that uses this kind of electromagnetic drive mechanism.  
         [0004]     2. Description of Related Art  
         [0005]     In a high-pressure fuel supply pump comprising a variable displacement mechanism that includes an electromagnetic drive mechanism described in Japanese Application Patent Laid-Open Publication No. 2002-250462, a damping alloy is provided in a restriction part for restricting the movement of a movable member in order to dampen operating sounds of a variable displacement control mechanism including an electromagnetic drive mechanism.  
         [0006]     [Patent Document 1] Japanese Application Patent Laid-Open Publication No. 2002-250462  
       SUMMARY OF THE INVENTION  
       [0007]     However, this configuration will increase cost and may create an individual difference depending on apparatus (difference of control characteristics among individual electromagnetic drive mechanisms) due to change over time or installation tolerance of a damping member.  
         [0008]     The object of the-present invention is to reduce an individual difference depending on apparatus due to the change over time or installation tolerance when damping operating sounds of an electromagnetic drive mechanism used for a variable displacement control mechanism in a high-pressure fuel supply pump.  
         [0009]     To achieve the above object, the present invention is configured such that before the electromagnetic drive mechanism supplies a drive force to a plunger which is electromagnetically driven by the electromagnetic drive mechanism, another displacement force situates the plunger in a specific position.  
         [0010]     When compared to an occasion where the plunger is displaced all strokes by a magnetic biasing force, the above configuration is able to reduce the force of impact on a member (for example, valve body) mounted to the plunger and a restricting member, thereby damping the collision noise.  
         [0011]     Furthermore, since an extra member, such as a damping member, is not required, an individual difference depending on apparatus is not easily occured. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a longitudinal sectional view of a high-pressure fuel supply pump of a first embodiment according to the present invention.  
         [0013]      FIG. 2  is a fuel supply system as an example, that uses a high-pressure fuel supply pump according to the present invention.  
         [0014]      FIG. 3  is a partial longitudinal sectional view of a high-pressure fuel supply pump at an electromagnetic intake valve is closed in a first embodiment according to the present invention.  
         [0015]      FIG. 4  is a partial longitudinal sectional view of a high-pressure fuel supply pump at an electromagnetic intake valve is opened in a first embodiment according to the present invention.  
         [0016]      FIG. 5  is an operation diagram of a high-pressure fuel supply pump of a first embodiment according to the present invention.  
         [0017]      FIG. 6  is a longitudinal sectional view of an electromagnetic intake valve applied to a high-pressure fuel supply pump of a first embodiment according to the present invention.  
         [0018]      FIG. 7  is a partial longitudinal sectional view of a high-pressure fuel supply pump of a second embodiment according to the present invention.  
         [0019]      FIG. 8  is an operation diagram of a high-pressure fuel supply pump of a second embodiment according to the present invention.  
         [0020]      FIG. 9  is an operation diagram of a high-pressure fuel supply pump of a third embodiment according to the present invention.  
         [0021]      FIG. 10  is an operation diagram of a high-pressure fuel supply pump of a fourth embodiment according to the present invention.  
         [0022]      FIG. 11  is a drawing showing a relationship between the DUTY ratio (ratio of time while an input voltage is being ON) in the DUTY control is executed and power consumed by a coil of an electromagnetic intake valve in a fourth embodiment according to the present invention.  
         [0023]      FIG. 12  is a longitudinal sectional view of an electromagnetic intake valve applied to a high-pressure fuel supply pump of a fifth embodiment according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     Hereafter, embodiments of the present invention will be explained with reference to the drawings.  
       Embodiment 1  
       [0025]      FIG. 1  is a longitudinal sectional view of an entire high-pressure fuel supply pump of a first embodiment according to the present invention.  
         [0026]      FIG. 2  is a schematic system diagram of a fuel supply system of an internal combustion engine.  
         [0027]     A damper cover  14  including a pressure pulsation damping mechanism  9  for damping the fuel pressure pulsation is mounted to the pump body  1 . The damper cover  14  has a fuel intake port  10   a.    
         [0028]     An intake passage  10  comprises fuel intake ports  10   a ,  10   b ,  10   c  and  10   d , and a pressure pulsation damping mechanism  9  for damping the fuel pressure pulsation is located in the middle of the passage.  
         [0029]     A fuel discharge port  12  is provided in the pump body  1 , and a pressure chamber  11  for pressurizing fuel is provided in the middle of the fuel passage which extends from the fuel intake port  10   a to the fuel discharge port  12 .  
         [0030]     An electromagnetic intake valve  30  is provided at the inlet of the pressure chamber  11 . The electromagnetic intake valve  30  receives a biasing force in the direction that closes the intake port by an intake valve spring  33  provided in the electromagnetic intake valve  30 . This configuration enables the electromagnetic intake valve  30  to function as a check valve which controls the direction of the fuel flow.  
         [0031]     A discharge valve  8  is provided at the outlet of the pressure chamber  11 . The discharge valve  8  comprises a discharge valve seat  8   a , discharge valve  8   b , discharge valve spring  8   c , and a discharge valve stopper  8   d . When there is no fuel differential pressure between the pressure chamber  11  and the fuel discharge port  12 , the discharge valve  8   b  is contact-bonded onto the discharge valve seat  8   a  by means of a biasing force caused by the discharge valve spring  8   c , thereby the valve is closed. When the fuel pressure of the pressure chamber  11  becomes larger than that of the fuel discharge port  12 , the discharge valve  8   b  begins to resist the discharge valve spring  8   c , thereby opening the valve; then, fuel in the pressure chamber  11  is delivered under high pressure to a common rail  23  via the fuel discharge port  12 . When the discharge valve  8   b  opens, it comes in contact with the discharge valve stopper  8   d , resulting in the restriction of the valve operation. Therefore, the stroke of the discharge valve  8   b  is properly determined by the discharge valve stopper  8   d . If the stroke is too long, fuel delivered to the fuel discharge port  12  under high pressure will flow back into the pressure chamber  11  due to the delay of closing the discharge valve  8   b , thereby decreasing the efficiency of a high-pressure pump. Furthermore, when the discharge valve  8   b  repeatedly opens and closes, the discharge valve stopper  8   d  directs so that the discharge valve  8   b  moves only in the direction of the stroke. This configuration enables the discharge valve  8  to function as a check valve which controls the direction of the fuel flow.  
         [0032]     The outer circumference of a cylinder  6  is held by a cylinder holder  7 , and the cylinder  6  is mounted to the pump body  1  by inserting a screw which is threaded on the outer circumference of the cylinder holder  7  into a screw thread made on the pump body. The cylinder  6  holds a plunger  2 , which is a pressurizing member, so that the plunger  2  can vertically slide.  
         [0033]     A tappet  3 , which converts a rotating motion of the cam  5  into a vertical motion and conveys that motion to the plunger  2 , is provided at the lower end of the plunger  2 . The plunger  2  is contact-bonded onto the tappet  3  by a spring  4  via a retainer  15 . This configuration can move the plunger  2  up and down according to the rotation of the cam  5 .  
         [0034]     Furthermore, as shown in the drawing, the lower end of the cylinder  6  is sealed by a plunger seal  13  in order to prevent gasoline (fuel) from leaking outside. Simultaneously, it prevents lubrication oil (engine oil can be used) which lubricates the sliding part from flowing into the inside of the pump body  1 .  
         [0035]     A pressure chamber  11  comprises an electromagnetic intake valve  30 , fuel discharge valve  12 , plunger  2 , cylinder  6 , and the pump body  1 .  
         [0036]     Fuel is directed from a fuel tank  20  to the fuel intake port  10   a  of the pump by a low-pressure pump  21  via an intake pipe  28 . At that time, the pressure of intake fuel flowing into the pump body  1  is regulated at a constant pressure by a pressure regulator  22 . Fuel that has been directed to the fuel intake port  10   a  is pressurized at a high pressure by the pump body  1 , and then pressure-fed from a fuel discharge port  12  to a common rail  23 . The common rail  23  is equipped with an injector  24 , relief valve  25 , and a pressure sensor  26 . Injectors  24  are mounted in accordance with the number of cylinders of the internal combustion engine, and inject fuel according to a signal from the engine control unit (ECU)  27 . Furthermore, the relief valve  25  opens when the pressure inside the common rail  23  exceeds a certain level, thereby preventing the pipe from being damaged.  
         [0037]     Next, by referring to  FIGS. 3, 4 , and  5 , a variable displacement control mechanism which controls the amount of fuel delivered under high pressure will be described.  
         [0038]      FIG. 3  is an enlarged view of the inside of the pump when an electromagnetic intake valve  30  is closed.  
         [0039]      FIG. 4  is an enlarged view of the inside of the pump. What is different from  FIG. 3  is that an electrical intake valve  30  is open in  FIG. 4 .  
         [0040]      FIG. 5  shows an operation diagram of a high-pressure fuel supply pump of the embodiment according to the present invention.  
         [0041]     The intake valve  31  comprises an intake valve plunger  31   a  which has an intake valve  31 A on the tip, an anchor  31   b , and a spring stopper  31   c . The anchor  31   b  and the spring stopper  31   c  are press-fitted to the intake valve plunger  31   a . When the intake valve  31 A is closed, the seat  31 C blocks the intake port  31 B, thereby blocking the intake passage  10  and the pressure chamber  11 .  
         [0042]     The intake valve spring  33  determines a biasing force in a position at which the spring stopper  31   c  press-fits.  
         [0043]     When an input voltage applied to an electromagnetic drive mechanism is shut off and there is no magnetic biasing force, and also when there is no fluid differential pressure between the intake passage  10   d  and the pressure chamber  11 , the biasing force of the intake valve spring  33  biases the intake valve  31  in the direction of closing the valve, as shown in  FIG. 3 , thereby closing the valve.  
         [0044]     When the plunger  2  is functioning in the intake process as the result of the rotation of the cam  5 , the volume of the pressure chamber  11  increases and the fuel pressure decreases. If the fuel pressure of the pressure chamber  11  becomes lower than the pressure of the intake passage  10   d , a valve-opening force is generated by fluid differential pressure of fuel in the intake valve  31 .  
         [0045]     Due to the valve-opening force caused by the fluid differential pressure, the intake valve  31  overcomes the biasing force of the intake valve spring  33  thereby becoming fully open as shown in  FIG. 4 . Since the amount of displacement of the intake valve  31  is restricted by core  35 , when the valve is fully open, the anchor  31   b  comes in contact with core  35 . Furthermore, the core  35  determines the stroke of the intake valve  31 .  
         [0046]     In this condition, if an input voltage from the ECU  27  is applied to a coil  36  via a terminal  137 , a current flows through the coil  36 . The waveform of the flowing current is determined by the resistance value and the inductance value of the coil  36 . This current generates a magnetic biasing force that attracts the anchor  31   b  and core  35  to each other. However, since the intake valve  31  has been fully open due to the fluid differential pressure and is coming in contact with core  35 , even if a magnetic biasing force is generated at this point, the anchor  31   b  and core  35  will not collide with each other.  
         [0047]     Furthermore, since the valve-opening force generated by the fluid differential pressure is much smaller than the magnetic biasing force, slight collision noise is made when the intake valve  31  opens due to the fluid differential pressure and collides with core  35  which is a restricting member.  
         [0048]     The above configuration makes it possible to dampen the collision noise made when an electromagnetic intake valve  30  operates without using a damping alloy.  
         [0049]     While an input voltage is being ON to the coil  36 , the plunger  2  finishes the intake process and moves onto the compressing process.  
         [0050]     When the plunger  2  begins the compressing process, the intake valve  31  is still open because there is no valve-opening force due to the fluid differential pressure and the input voltage is still being ON which means that the magnetic biasing force is being applied.  
         [0051]     The volume of the pressure chamber  11  reduces according to the compressing movement of the plunger  2 ; however in this condition, fuel that has been taken into the pressure chamber  11  is returned to the intake passage  10   d  via the intake valve  31  that is open, and therefore, the pressure of the pressure chamber does not increase. This process is called the “return process”. At this time, both a biasing force due to an intake valve spring  33  and a valve-closing force due to a fluid force generated when fuel flows back from the pressure chamber  11  to the intake passage  10   d  are applied to the intake valve  31 .  
         [0052]     However, a very weak biasing force created by the intake valve spring  33  is set.  
         [0053]     Thus, sufficient magnetic biasing force can be ensured to keep the valve open.  
         [0054]     Also at this time, pressure pulsation is generated in the intake passage  10  due to fuel that has been returned to the intake passage  10   d . The pressure pulsation is absorbed and dampened by a pressure damping mechanism  9  comprising two pressure pulsation dampers  9   a  and  9   b ; and the transmission of the pressure pulsation being applied to the intake pipe  28  extending from the low-pressure pump  21  to the pump body  1  is eliminated, thereby preventing the intake pipe  28  from being damaged and simultaneously enabling fuel to be supplied to the pressure chamber  11  under stable fuel pressure.  
         [0055]     In this condition, if the input voltage from the ECU  27  is shut off, the amount of current that flows through the coil  36  becomes zero; however, the magnetic biasing force applied to the intake valve will be eliminated after a certain time after the input voltage has been turned off (hereafter, this time is referred to as “magnetic release delays”). Because both a biasing force caused by the intake valve spring  33  and a valve-closing force generated when fuel flows back from the pressure chamber  11  to the intake passage  10   d  are applied to the intake valve  31 , the valve closes, and at that point in time, the fuel pressure of the pressure chamber  11  increases as the plunger  2  moves upward. Then, the pressure exceeds the pressure of the discharge port  12 , fuel that remains in the pressure chamber  11  is delivered under high pressure via a discharge valve  8 , and supplied to the common rail  23 . This process is called the “delivery process”. That is, the plunger&#39;s compressing process includes a return process and a delivery process.  
         [0056]     Furthermore, it is possible to control the amount of fuel that is delivered under high pressure by controlling the timing at which the application of an input voltage to the coil  36  is OFF. If the input voltage is turned off earlier, the ratio of the return process to the entire compressing process is small and the ratio of the delivery process is large. That is, the amount of fuel that is returned to the intake passage  10   d  is small, and the amount of fuel that is delivered under high pressure is large. On the other hand, if the input voltage is turned off later, the ratio of the return process to the entire compressing process is large and the ratio of the delivery process is small. That is, the amount of fuel that is returned to the intake passage  10   d  is large, and the amount of fuel that is delivered under high pressure is small.  
         [0057]     The timing at which the input voltage is turned off is decided by the command of the ECU.  
         [0058]     The above configuration ensures a sufficient magnetic biasing force to keep the intake valve  31  open. And also, by controlling the timing for turning off the input voltage, it is possible to control the amount of fuel which is to be delivered under high pressure so that the required amount of fuel to the internal combustion engine can be ensured.  
         [0059]     Next, the configuration of an electromagnetic intake valve  30  applied to a high-pressure fuel supply pump will be described with reference to  FIG. 6 .  
         [0060]      FIG. 6  shows an electromagnetic intake valve, alone.  
         [0061]     An intake valve  31  comprises an intake valve plunger  31   a , anchor  31   b , and a spring stopper  31   c ; and the anchor  31   b  and the spring stopper  31   c  are press-fit and held by an intake valve plunger  31   a . A biasing force of an intake valve spring  33  is adjusted at the position of the spring stopper  31   c , and when an input voltage applied to a coil  36  is turned off, the intake valve is closed due to a biasing force of the intake valve spring  33 . When the valve is closed, the fuel sealing property is maintained by an intake valve plunger  31   a  coming in contact with a valve block  32 . The clearance between a first holding member  34  and the intake valve  31   a  of the intake valve  31  is kept so that the intake valve  31  can slide.  
         [0062]     When an intake valve is repeatedly opened and closed by repeatedly applying an input voltage to the coil  36  and turning it off, the intake valve  31  swings like a pendulum with a first holding member  34  as the center. This causes the opening and closing operations of the intake valve  31  to become unstable. Furthermore, if the intake valve  31  swings with large amplitude, the anchor  31   b  comes in contact with core  37 , causing the opening and closing operations of the intake valve  31  to become more unstable. If the opening and closing operations of the intake valve  31  become unstable, it becomes impossible to stably control and supply the amount of high-pressure fuel.  
         [0063]     Therefore, a second holding part  32   a  is provided in the valve block  32 . The clearance between the intake valve plunger  31   a  and the second holding part  32   a  is provided to restrict pendulum motions that occur when the intake valve  31  repeatedly opens and closes, and does not block the sliding motions.  
         [0064]     As a result, even if the intake valve  31  repeatedly opens and closes by repeatedly applying an input voltage to the coil  36  and turning it off, the intake valve  31  does not swing like a pendulum, and the anchor  31   b  does not come in contact with core (B)  37 . Therefore, stable opening and closing operations can be ensured, thereby making it possible to stably control and supply the amount of high-pressure fuel.  
         [0065]     Furthermore, since the intake valve spring  33  is incorporated in the intake valve  31 , it is possible to integrate the intake valve  31  and the valve block  32  into a unit of electromagnetic intake valve. Furthermore, it is mounted to a pump body  1  by inserting a screw threaded on the outer circumference of the yoke  38  into a screw thread made on the pump body  1 .  
         [0066]     By doing so, it is possible to integrate the intake valve  31  into a unit; and since the integrated unit can be incorporated into the pump body, the number of fabrication steps can be reduced.  
       Embodiment 2  
       [0067]     Next, a second embodiment of the present invention will be described with reference to  FIGS. 7 and 8 .  
         [0068]      FIG. 7  is an enlarged view of the inside of the pump. What is different from  FIG. 3  and  FIG. 4  is that the intake valve  31  is open but is not fully open, and does not come in contact with core  35  which is a restricting member.  
         [0069]      FIG. 8  shows the operation of the pump. What is different from  FIG. 5  is that the intake valve  31  is open but is not fully open until halfway of the intake process, and does not come in contact with core  35  which is a restricting member.  
         [0070]     When the plunger  2  is functioning in the intake process as the result of the rotation of the cam  5 , the volume of the pressure chamber  11  increases and the fuel pressure decreases. If the fuel pressure of the pressure chamber  11  becomes lower than the pressure of the intake passage  10   d , a valve-opening force is generated by fluid differential pressure of fuel in the intake valve  31 .  
         [0071]     Due to the valve-opening force caused by the fluid differential pressure, the intake valve  31  overcomes the biasing force of the intake valve spring  33  thereby becoming open, as shown in  FIG. 7 ; however, it has been determined that the value of the biasing force of the intake valve spring  33  be small so that the fluid differential pressure is balanced with the biasing force generated by the intake valve spring  33 , and the intake valve  31  does not come in contact with core  35  which is a restricting member.  
         [0072]     In this condition, if an input voltage from the ECU  27  is applied to a terminal  137 , a current flows through the coil  36 . This current generates a magnetic biasing force that attracts the anchor  31   b  and core  35  to each other, then the intake valve  31  moves the remaining strokes and collides with core  35  which is a restricting member.  
         [0073]     Furthermore, because the intake valve  31  has displaced to the position at which a valve-opening force generated by the fluid differential pressure is balanced with a biasing force of the intake valve spring  33 , collision noise that is caused by applying an input voltage is quieter than the collision noise made by moving full stroke.  
         [0074]     The above configuration makes it possible to dampen the collision noise made when an electromagnetic intake valve  30  operates without using a damping alloy, and also makes it possible to control the amount of fuel delivered when the capacity is increased.  
       Embodiment 3  
       [0075]     Next, a third embodiment of the present invention will be described with reference to  FIG. 9 .  
         [0076]      FIG. 9  shows the operation of the pump. What is different from  FIG. 8  is that generated current is restricted.  
         [0077]     When the plunger  2  is functioning in the intake process as the result of the rotation of the cam  5 , the volume of the pressure chamber  11  increases and the fuel pressure decreases. If the fuel pressure of the pressure chamber  11  becomes lower than the pressure of the intake passage  10   d , a valve-opening force is generated by fluid differential pressure of fuel in the intake valve  31 .  
         [0078]     Due to the valve-opening force, the valve overcomes a biasing force of the intake valve spring  33  and opens. At this time, as shown in  FIG. 5 , it is possible to determine the necessary biasing force of the intake valve spring  33  so that the valve fully opens due to the fluid differential pressure, and comes in contact with core  35  which is a restricting member. Furthermore, it is also possible to determine the necessary biasing force of the intake valve spring  33  so that the fluid differential pressure is balanced with the biasing force of the intake valve spring  33  and the intake valve  31  does not come in contact with core  35  which is a restricting member as shown in  FIG. 7 .  
         [0079]     In this condition, if an input voltage from the ECU  27  is applied to a terminal  137 , a current flows through the coil  36 . This current is controlled as shown by the solid line with a waveform in  FIG. 9 . The waveform shown by the broken line in  FIG. 9  is a current waveform when current is not controlled. When the value of the current is small, the value of the magnetic biasing force that is applied to the intake valve  31  is also small.  
         [0080]     This configuration makes it possible to make the collision noise made when the intake valve  31  collides with core (A)  35  quieter than that of embodiment  2 .  
         [0081]     Furthermore, during the compressing process of the plunger  2 , both the biasing force of the intake valve spring  33  and the valve-closing force generated when fuel flows back from the pressure chamber  11  to the intake passage  10   d  are applied to the intake valve  31 ; and therefore, it is possible to control the amount of fuel delivered under high pressure by controlling current so that the magnetic biasing force greater than those resultant forces can be generated in the intake valve  31 .  
         [0082]     The above configuration makes it possible to further dampen the collision noise made when an electromagnetic intake valve  30  operates without using a damping alloy, and also makes it possible to control the amount of fuel delivered when the capacity is increased.  
         [0083]     Furthermore, because the value of the current flowing through the coil  36  is small, the amount of generated heat is low, thereby keeping the power consumption low.  
         [0084]     Moreover, because the amount of generated heat is small, the coil  36  will not be broken.  
       Embodiment 4  
       [0085]     Next, a fourth embodiment of the present invention will be described with reference to  FIG. 10 .  
         [0086]      FIG. 10  shows the operation of the pump. What is different from  FIG. 8  is that during the period from when an input voltage is applied to when it is turned off, the input voltage is periodically applied and turned off in a shorter circle.  
         [0087]     When the plunger  2  is functioning in the intake process as the result of the rotation of the cam  5 , the volume of the pressure chamber  11  increases and the fuel pressure decreases. If the fuel pressure of the pressure chamber  11  becomes lower than the pressure of the intake passage  10   d , a valve-opening force is generated by fluid differential pressure of fuel in the intake valve  31 .  
         [0088]     Due to the valve-opening force, the intake valve  31  overcomes a biasing force of the intake valve spring  33  and opens. At this time, as shown in  FIG. 5 , it is possible to determine the necessary biasing force of the intake valve spring  33  so that the intake valve  31  fully opens due to the fluid differential pressure, and comes in contact with core  35  which is a restricting member. Furthermore, it is also possible to determine the necessary biasing force of the intake valve spring  33  so that the fluid differential pressure is balanced with the biasing force of the intake valve spring  33  and the intake valve  31  does not come in contact with core  35  which is a restricting member as shown in  FIG. 10 .  
         [0089]     In this condition, if an input voltage from the ECU  27  is applied to a terminal  137 , a current flows through the coil  36 . At this point in time, during the period from when an input voltage is applied to when it is turned off, the input voltage is periodically applied and turned off in a shorter circle. If, in this way, the time period from when an input voltage is applied to when it is turned off is controlled by means of the DUTY control, current flowing through the coil  36  is as shown by the solid line with a waveform in  FIG. 10 . The waveform, shown by the broken line in  FIG. 10 , is a waveform of the current when the DUTY control is not executed. Because the input voltage is periodically applied and turned off in a shorter circle during the period from when an input voltage is applied to when it is turned off, the current that started to flow decreases to zero, but the current starts to flow again by the application of the voltage. Even if the value of the current decreases to zero, the magnetic biasing force that has been generated in the intake valve  31  is not immediately eliminated. As shown in  FIG. 10 , there is a magnetic release delay, and the magnetic biasing force can be held even if current does not flow for a certain period. Therefore, even if the value of the current decreases to zero, if another cycle causes an input voltage to be applied so that current starts to flow again during the time of the magnetic release delay, the intake valve  31  can be kept open, or it is possible to ensure sufficient magnetic biasing force to keep the valve body open.  
         [0090]     This configuration makes it possible to make the collision noise made when the anchor  31   b  collides with core  35  quieter than that of embodiment 2.  
         [0091]     Furthermore, during the compressing process of the plunger  2 , both the biasing force caused by the intake valve spring  33  and the valve-closing force due to a fluid force generated when fuel flows back from the pressure chamber  11  to the intake passage  10   d  are applied to the intake valve  31 ; and therefore, it is possible to control the amount of fuel delivered under high pressure by creating a short cycle and determining the appropriate timing for applying and turning off an input voltage so that a magnetic biasing force greater than those resultant forces can always be generated in the intake valve  31  during the period from when an input voltage is applied to when it is turned off.  
         [0092]     The above configuration makes it possible to further dampen the collision noise made when an electromagnetic intake valve  30  operates without using a damping alloy, and also makes it possible to control the amount of fuel delivered when the capacity is increased.  
         [0093]     Furthermore, the waveform of the current flowing through the coil  36  is as shown in  FIG. 10 . If an input voltage is applied again after it has been once turned off, current starts to flow again, but due to the inductance of the coil  36 , the current gradually starts flowing as shown by the solid line with a curve in  FIG. 10 . Consequently, the amount of heat generated in the coil  36  can be effectively reduced.  FIG. 11  shows the relationship between the DUTY ratio (ratio of the time period when an input voltage is being ON) obtained as the result of the DUTY control of the time period from when an input voltage is applied to when it is turned off, as shown above by the solid line, and the power consumed by the coil  36 . The broken line in  FIG. 11  shows power consumption when the DUTY control is not executed. In order to generate a greater magnetic biasing force in the intake valve  31 , it is necessary to make the DUTY ratio as large as possible. On the other hand, when compared to the occasion in which the DUTY control is not executed, power consumed by the coil  36  can be sufficiently reduced even when the DUTY ratio is near 100%. Therefore, it is possible to effectively keep power consumed by the electromagnetic intake valve  30  low.  
         [0094]     Thus, because the amount of generated heat can be small, the coil  36  will not be broken.  
         [0095]     Furthermore, it is also possible to simplify the ECU circuit when compared to embodiment  3  in which the current is controlled. This is an advantage.  
       Embodiment 5  
       [0096]     Next, a fifth embodiment of the present invention will be described with reference to  FIG. 12 .  
         [0097]      FIG. 12  shows a single electromagnetic intake valve.  
         [0098]     An intake valve  31  comprises an intake valve plunger  31   a  and an anchor  31   b , and the anchor  31   b  is press-fit and held by the intake valve plunger  31   a . A biasing force of an intake valve spring  33  is adjusted at the position of the anchor  31   b , and when an input voltage is not applied to a coil  36 , the intake valve is closed due to a biasing force of the intake valve spring  33 . The clearance between a first holding member  34  and the intake valve plunger  31   a  of the intake valve  31  is kept so that the intake valve  31  can slide.  
         [0099]     When an intake valve is repeatedly opened and closed by repeatedly applying an input voltage to the coil  36  and turning it off, the intake valve  31  swings like a pendulum with a first holding member  34  as the center. This causes the opening and closing operations of the intake valve  31  to become unstable. If the opening and closing operations of the intake valve  31  become unstable, it becomes impossible to stably control and supply the amount of high-pressure fuel.  
         [0100]     Therefore, a second holding part  32   a  is provided in the valve block  32 . The clearance between the intake valve plunger  31   a  and the second holding part  32   a  is provided to restrict pendulum motions that occur when the intake valve  31  repeatedly opens and closes, and does not block the sliding motions.  
         [0101]     As a result, even if the intake valve  31  repeatedly opens and closes by repeatedly applying an input voltage to the coil  36  and turning it off, the intake valve  31  does not swing like a pendulum. Therefore, stable opening and closing operations can be ensured, thereby making it possible to stably control and supply the amount of high-pressure fuel.  
         [0102]     Furthermore, since the intake valve spring  33  is incorporated in the intake valve  31 , it is possible to integrate the intake valve  31  and the valve block  32  into a unit of electromagnetic intake valve. Furthermore, it is mounted to the pump body  1  by inserting a screw threaded on the outer circumference of the yoke  38  into a screw thread made on the pump body  1 .  
         [0103]     By doing so, it is possible to integrate the intake valve  31  into a unit, and since the integrated unit can be incorporated into the pump body, the number of fabrication steps can be reduced.  
         [0104]     Thus, problems to be solved by this embodiment, description of the embodiment, and the effects of the embodiment can be summarized as follows:  
         [0105]     This embodiment relates to an electromagnetic drive mechanism; specifically to a high-pressure fuel supply pump for pumping high-pressure fuel to a fuel injection valve of an internal combustion engine that uses this kind of electromagnetic drive mechanism. It also relates to a high-pressure fuel supply pump including a variable displacement mechanism which controls the amount of fuel delivered.  
         [0106]     This embodiment can be applied to a high-pressure fuel supply pump including a variable displacement mechanism which controls the amount of fuel delivered which is described in International Publication WO00-47888.  
         [0107]     There is a problem with the one described in International Publication WO00-47888 in that if the capacity of the high-pressure fuel supply pump is increased and the amount of high-pressure fuel to be delivered is increased, it is not possible to control the amount of flow volume to be delivered so that it becomes very low or zero by using the variable displacement control mechanism.  
         [0108]     In other words, when trying to control the flow volume to become very low or zero by using a variable displacement control mechanism which opens an intake valve by means of a spring force when an input voltage to an electromagnetic drive mechanism is turned off, most of the fuel that has been taken into the pressure chamber via an intake passage as the volume of the pressure chamber increases during the intake process of the plunger has to be returned to the intake passage via the intake valve when the volume of the pressure chamber decreases during the compressing process of the plunger. At this time, a valve-closing force is applied to the intake valve which is caused by a fluid force generated when fuel flows back. Therefore, the spring force must be set to become greater than the valve-closing force. This is because if the valve-closing force is greater and the intake valve closes as the result of resisting the spring force, the high-pressure fuel discharge starts at that point in time, thereby making it impossible to control the flow volume so that it becomes very low or zero.  
         [0109]     On the other hand, in order to increase the discharge capacity of the high-pressure fuel supply pump, it is necessary to increase the diameter of the plunger or to increase the stroke of the reciprocating movement of the plunger. At this point, because a lot of fuel is taken into the pressure chamber via the intake passage as the volume of the pressure chamber increases during the intake process of the plunger, the amount of fuel returned to the intake passage from the pressure chamber as the volume of the pressure chamber decreases during the compressing process of the plunger becomes large. Then, the valve-closing force generated when fuel flows back increases, which causes the intake valve to unexpectedly close as it resists the spring force, thereby making it impossible to control the flow volume to become very low or zero.  
         [0110]     Furthermore, to solve the above problem, if the spring force is made greater than a relatively great valve-closing force, another problem arises in that the electromagnetic drive mechanism must generate a magnetic biasing force greater than the relatively great spring force in order to close the intake valve, which causes the electromagnetic drive mechanism to consume a large amount of electric power.  
         [0111]     Or, there is another problem in that this large, power consumption results in generating a large amount of heat in the electromagnetic drive mechanism, which may result in a broken wire of the coil.  
         [0112]     Furthermore, another problem arises in that if the variable displacement mechanism is activated to control the amount of fuel delivered under high pressure, a loud noise is generated when a restricting member which restricts the movement of the movable member collides with a movable part.  
         [0113]     Or, if a damping alloy is provided in the colliding part so as to dampen the collision noise, as shown in Japanese Application Patent Laid-Open Publication No. 2002-250462, the production cost increases. Furthermore, there is another problem in decreased reliability.  
         [0114]     Moreover, there is yet another problem in that when the electromagnetic drive mechanism is driven to repeatedly open and close the intake valve, the intake valve also moves in a direction perpendicular to the direction along which the intake valve slides, which makes opening and closing operations of the intake valve, especially the closing operation, unstable, and the amount of flow volume delivered is not constant.  
         [0115]     Furthermore, still yet another problem is that an electromagnetic drive mechanism and an intake valve must separately be incorporated into the high-pressure fuel supply pump body, thereby causing the number of fabrication processes to increase.  
         [0116]     This embodiment is able to solve at least one of those problems, it embodies a high-pressure fuel supply pump whose capacity can be increased and which controls the amount of fuel delivered under high pressure, thereby damping operating sounds made by the variable displacement control mechanism.  
         [0117]     Specifically, an electromagnetic drive mechanism (electromagnetic intake valve  30 ), comprising a movable plunger (intake valve plunger  31   a , anchor  31   b ) operated by an electromagnetic force, a restricting member (core  35 ) for restricting the displacement of the plunger in a specific position, and a biasing member (intake valve spring  33 ) for biasing the movable plunger to the opposite side of the restricting member, is configured such that a force other than the electromagnetic force can aid the movable plunger along the same direction in which the movable plunger moves as the result of the electromagnetic force, and the electromagnetic force is applied to the plunger after the movable plunger has been moved a specific displacement in the direction toward the restricting member by means of a force other than the electromagnetic force. Herein, the plunger can drive not only the intake valve but also an overflow valve which is an inward-opening valve that opens and closes an overflow port through which overflowing fuel from the pressure chamber flows.  
         [0118]     Furthermore, an electromagnetic valve mechanism comprises  
         [0119]     an inward-opening valve body (intake valve  31 A or overflow valve) provided at a fluid intake port (intake port  31 B),  
         [0120]     a movable plunger (intake valve plunger  31   a ) mounted to the valve body,  
         [0121]     an electromagnetic drive mechanism (electromagnetic intake valve  30 ) which electromagnetically biases the movable plunger and opens the valve body, and  
         [0122]     a spring (intake valve spring  33 ) which biases the valve body (intake port  31 B) and the movable plunger (intake valve plunger  31   a ) along the direction of closing the fluid intake port (intake port  31 B) and operates the valve body in the direction of opening the valve in cooperation with the fluid differential pressure between the upstream side pressure and the downstream side pressure of the valve body (intake valve  31 A).  
         [0123]     Moreover, an electromagnetic valve mechanism, comprising  
         [0124]     an inward-opening valve body (intake valve  31 A) provided at a fluid intake port (intake port  31 B),  
         [0125]     a movable plunger (intake valve plunger  31   a ) mounted to the valve body,  
         [0126]     a spring (intake valve spring  33 ) which biases the valve body (intake valve  31 A) and the movable plunger (intake valve plunger  31   a ) in the direction along which the fluid intake port is closed, and  
         [0127]     an electromagnetic drive mechanism (electromagnetic intake valve  30 ) which electromagnetically biases the movable plunger and opens the valve body, is configured such that after the valve body has initially opened as the result of resisting the force of the spring caused by the fluid differential pressure between the upstream side pressure and the downstream side pressure of the valve body, the electromagnetic drive mechanism (electromagnetic intake valve  30 ) biases the movable plunger (intake valve plunger  31   a ) in the direction along which the valve body is kept open or kept further open.  
         [0128]     More specifically, an electromagnetic intake valve, comprising  
         [0129]     an intake valve operated by a magnetic biasing force,  
         [0130]     an electromagnetic drive mechanism which opens the intake valve and keeps it open by the magnetic biasing force,  
         [0131]     a restricting member for restricting the displacement due to the open-operation of the intake valve in a specific position, and  
         [0132]     a spring which biases the intake valve in the direction of closing the valve, is configured such that the electromagnetic drive mechanism closes the intake valve due to a spring force when an input voltage is not applied and there is no fluid differential pressure between the intake channel side pressure and the pressure chamber side pressure of the intake valve. Then, during the intake process of the plunger, the spring force is adjusted so that the fluid differential pressure between the intake channel side pressure and the pressure chamber side pressure is applied to the intake valve as a result of an increase in the volume of the pressure chamber, thereby opening the intake valve.  
         [0133]     When the fluid differential pressure is applied, the intake valve overcomes the spring force due to a valve-opening force and opens. At this time, it is possible to set the spring force so that the intake valve is fully open due to the fluid differential pressure, and the intake valve comes in contact with the restricting member. Furthermore, it is also possible to set the spring force so that the fluid differential pressure balances with the spring force thereby preventing the intake valve from coming in contact with the restricting member.  
         [0134]     The above configuration makes it possible to set the value of the spring force to be very small.  
         [0135]     If the plunger&#39;s intake process starts while an input voltage to the electromagnetic drive mechanism is turned off, the intake valve is kept open due to a fluid differential pressure between the intake channel side pressure and the pressure chamber side pressure which is generated due to an increase in the volume of the pressure chamber, and then an input voltage will be applied to the electromagnetic drive mechanism.  
         [0136]     The intake valve has been completely displaced before an input voltage is applied, and when the intake valve is coming in contact with the restricting member, an additional collision will not occur even if a magnetic biasing force is applied. When the valve opens due to the fluid differential pressure, the intake valve collides with the restricting member; however, the fluid differential pressure is very small compared to the magnetic biasing force.  
         [0137]     The above configuration decreases the impact force generated between the intake valve and the restricting member thereby making it possible to dampen the collision noise.  
         [0138]     Furthermore, when the fluid differential pressure balances with the spring force, and the intake valve does not reach the restricting member before an input voltage is applied, the intake valve will displace remaining strokes toward the restricting member by means of the magnetic biasing force applied to the intake valve.  
         [0139]     When the plunger is in the intake process, the volume of the pressure chamber increases by the amount of space the descending plunger creates, and therefore, fuel flows into the pressure chamber from the intake passage.  
         [0140]     Until the plunger begins the compressing process, an input voltage is applied to the electromagnetic drive mechanism, thereby keeping the valve open. At this time, because the volume of the pressure chamber decreases by the amount of space created by the movement of the plunger, the corresponding amount of fuel that has flown into the pressure chamber will be returned to the intake passage. This process is called the “return process”. At this time, the magnetic biasing force generated in the intake valve by the electromagnetic drive mechanism must be greater than the sum of the valve-closing force due to the fluid force generated when fuel flows back and the spring force. However, it is possible to set the value of the spring force small, thereby making it possible to generate a sufficient magnetic biasing force.  
         [0141]     If an input voltage to the electromagnetic drive mechanism is turned off in the middle of the compressing process of the plunger and a magnetic biasing force that has been applied to the intake valve is turned off, the intake valve closes due to the valve-closing force generated when fuel flows back and the spring force. At this point in time, fuel in the pressure chamber is pressurized by the compressing motion of the plunger, and when the pressure of the fuel in the pressure chamber becomes higher than the discharge pressure, fuel starts to be delivered under high pressure from the discharge valve. This process is called the “delivery process”. That is, the compressing process of the plunger includes a return process and a delivery process.  
         [0142]     The controller  27  controls the amount of fuel delivered under high pressure by controlling the timing for turning off the input voltage applied to the electromagnetic drive mechanism. If the controller  27  turns off the input voltage earlier, the ratio of the return process of the compressing process is small and the ratio of the delivery process is large. This means that an amount of fuel returned from the pressure chamber to the intake passage is small, and an amount of fuel delivered under high pressure becomes large. If the controller  27  turns off the input voltage later, the ratio of the return process of the compressing process is large and the ratio of the delivery process is small. This means that an amount of fuel returned from the pressure chamber to the intake passage is large, and an amount of fuel delivered under high pressure becomes small.  
         [0143]     The above configuration makes it possible for the capacity of the high-pressure fuel supply pump to be increased as well as enabling the variable displacement control mechanism to execute the controls.  
         [0144]     Furthermore, at this time, the controller  27  controls current flowing through the electromagnetic drive mechanism so that it is minimized. Then, the magnetic biasing force becomes small, thereby further damping noise made when the intake valve and the restricting member collide with each other due to the application of the magnetic biasing force.  
         [0145]     Also, it is possible to reduce the amount of power consumed by the electromagnetic drive mechanism.  
         [0146]     Furthermore, it is possible to prevent the coil from a broken wire due to heat.  
         [0147]     Furthermore, during the period from when an input voltage is applied to when it is turned off, the controller  27  outputs control signals so that an input voltage is periodically applied and turned off in a shorter cycle. By doing so, the value of the magnetic biasing force also becomes small, thereby further damping noise made when the intake valve and the restricting member collide with each other due to the application of the magnetic biasing force.  
         [0148]     Thus, it is possible to reduce the amount of power consumed by the electromagnetic drive mechanism.  
         [0149]     Furthermore, it is possible to prevent the coil from a broken wire due to heat.  
         [0150]     As stated above, in this embodiment, a controller itself, an electromagnetic drive mechanism itself, or a control method of an electromagnetic valve mechanism itself have characteristics.  
         [0151]     Furthermore, a first holding part which slidably holds the-intake valve is provided, and also a second holding part is provided which restricts the motion generated in a direction perpendicular to the direction of sliding when the intake valve slides.  
         [0152]     This configuration keeps the opening and closing operations of the intake valve stable even when the intake valve repeatedly opens and closes by driving the electromagnetic intake valve, thereby making it possible to obtain a constant amount of fuel discharge.  
         [0153]     Furthermore, by providing a spring inside the electromagnetic drive mechanism, it is possible to integrate the electromagnetic drive mechanism with the intake valve as a unit.  
         [0154]     By doing so, it is possible to integrate as a unit the electromagnetic drive mechanism and the intake valve into the pump body thereby reducing the number of fabrication steps.  
         [0155]     Moreover, in the above embodiment, if the intake port is used as the overflow port, and the intake valve is used as the overflow valve, another embodiment in which the overflow valve is driven by an electromagnetic mechanism can be configured.