Patent Publication Number: US-7905215-B2

Title: Fuel supply apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and incorporates herein by reference Japanese Patent Application No. 2008-146468 filed on Jun. 4, 2008 and Japanese Patent Application No. 2009-069754 filed on Mar. 23, 2009. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel supply apparatus that includes a high-pressure pump and a controller that controls the high-pressure pump. 
     2. Description of Related Art 
     A high-pressure pump has a plunger and a pressurizer chamber, and the plunger is reciprocably movable such that the plunger compresses and pumps fuel that is suctioned by the pressurizer chamber. In the above, fuel compressed in the pressurizer chamber is metered based on valve-closing timing of an inlet valve. In other words, fuel in the pressurizer chamber is returned to a source, from which fuel is suctioned, during the inlet valve is opened after the plunger has started moving upward from a bottom dead center. When the inlet valve is closed, fuel is compressed in the pressurizer chamber. 
     The inlet valve is contactable with a needle that is fixed with a movable core by welding. Thus, the movable core and the needle move integrally and constitute a movable unit. When a coil is not energized and thereby a magnetic attractive force is not formed, the movable unit is urged toward the inlet valve or toward an opening-side position by a biasing force of a spring. As a result, the inlet valve is opened. 
     In order to close the inlet valve that is opened as above, the energization is made in order to attract the movable unit toward a closing-side position or to move the movable unit in a direction away from the inlet valve. Due to the above, when the movable unit is displaced to the closing-side position, the inlet valve is closed due to a spring of the inlet valve and due to pressure of fuel in the pressurizer chamber located downstream of the inlet valve (see, for example, JP-A-H9-151768). 
     However, in the conventional art, when the movable unit is displaced toward the closing-side position, noise may be generated due to collision of the movable unit with another member. Sometimes, the noise may be so large that the noise may be noticeable to a driver disadvantageously. 
     SUMMARY OF THE INVENTION 
     The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to address at least one of the above disadvantages. 
     To achieve the objective of the present invention, there is provided a fuel supply apparatus mounted on a vehicle, the apparatus including a receiver, a fuel passage, a valve member, a pressurizer chamber, a discharge unit, a movable unit, a coil, a drive circuit portion, and a drive control portion. The receiver receives fuel from an exterior. The fuel passage is communicated with the receiver. The valve member is provided in the fuel passage. The pressurizer chamber is located downstream of the fuel passage, and the pressurizer chamber receives fuel and compresses fuel in the pressurizer chamber. The discharge unit discharges fuel compressed in the pressurizer chamber. The movable unit is contactable with the valve member, and the movable unit is displaceable between a closing-side position and an opening-side position. The coil generates a magnetic attractive force attracting the movable unit. The drive circuit portion is adapted to energize the coil with a drive electric current such that the coil generates the magnetic attractive force. The drive circuit portion energizes the coil with the drive electric current of a first value such that the movable unit is displaced from the opening-side position to the closing-side position. The drive circuit portion energizes the coil with the drive electric current of a second value that is smaller than the first value such that the movable unit is held at the closing-side position. The drive control portion is adapted to control the drive circuit portion to change the drive electric current from the first value to the second value in order to displace the movable unit toward the closing-side position while the movable unit is being displaced toward the closing-side position based on energization of the coil with the drive electric current of the first value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with additional objectives, features and advantages thereof will be best understood from the following description, the appended claims and the accompanying drawings in which: 
         FIG. 1  is an explanatory diagram illustrating a general configuration including a fuel supply apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a schematic cross-sectional view illustrating a configuration of a high-pressure pump of the fuel supply apparatus according to the first embodiment of the present invention; 
         FIG. 3  is a block diagram illustrating the fuel supply apparatus of the first embodiment of the present invention; 
         FIG. 4  is an explanatory diagram illustrating an operation of the high-pressure pump of the fuel supply apparatus of the first embodiment of the present invention; 
         FIG. 5  is an explanatory diagram illustrating an operation of a fuel supply apparatus of a comparison example; 
         FIG. 6  is an explanatory diagram illustrating an operation of the fuel supply apparatus of the first embodiment of the present invention; 
         FIG. 7  is an explanatory diagram illustrating a relation between an energization time period and a vibration amplitude; 
         FIG. 8  is an explanatory diagram illustrating a learning control of the first embodiment of the present invention; 
         FIG. 9  is a flow chart illustrating a learning control of the first embodiment of the present invention; 
         FIG. 10  is a flow chart illustrating a learning condition determination operation of the first embodiment of the present invention; 
         FIG. 11A  is an explanatory diagram illustrating a relation between a pump rotational speed and a valve-closing force; 
         FIG. 11B  is an explanatory diagram illustrating a relation between an engine rotational speed and a vibration amplitude; 
         FIG. 12A  is an explanatory diagram illustrating behavior of a cam lift and a cam speed; 
         FIG. 12B  is an explanatory diagram illustrating a relation between an engine load ratio and a vibration amplitude; 
         FIG. 13A  is an explanatory diagram illustrating a learning control for each of operational ranges; 
         FIG. 13B  is another explanatory diagram illustrating a learning control for each of operational ranges; 
         FIG. 14A  is still another explanatory diagram illustrating a learning control for each of the operational ranges; 
         FIG. 14B  is further another explanatory diagram illustrating a learning control for each of the operational ranges; 
         FIG. 15  is a flow chart illustrating a modification of the learning condition determination operation of the first embodiment of the present invention; 
         FIG. 16  is an explanatory diagram illustrating a learning control according to a second embodiment of the present invention; 
         FIG. 17  is an explanatory diagram illustrating a learning control according to a third embodiment of the present invention; 
         FIG. 18A  is a block diagram illustrating a fuel supply apparatus according to the other embodiment of the present invention; and 
         FIG. 18B  is another block diagram illustrating a fuel supply apparatus according to the other embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Embodiment 
       FIG. 1  shows a general configuration that includes a fuel supply apparatus  100  according to the first embodiment of the present invention. 
     The fuel supply apparatus  100  of the present embodiment includes a high-pressure pump  10 , an electronic control device (ECU)  101 , and a fuel pressure sensor  102 . 
     The high-pressure pump  10  includes a plunger unit  30 , a metering valve unit  50 , and a discharge valve unit  70 . The high-pressure pump  10  compresses fuel that is pumped by a low-pressure pump  201  from a fuel tank  200 , and the high-pressure pump  10  discharges the compressed fuel to a fuel rail  400 . The high-pressure pump  10  defines therein a pressurizer chamber  14 , in which fuel is compressed. Specifically, when a camshaft  300  having a cam  301  rotates, a plunger  31  is reciprocably displaced along a cam profile of the cam  301 . As a result, a volume of the pressurizer chamber  14  is changed. Fuel is discharged to the fuel rail  400  through the discharge valve unit  70  in accordance with pressure of fuel in the pressurizer chamber  14 . The fuel rail  400  is connected with multiple injectors  401 . Each of the injectors  401  injects fuel into a combustion chamber  501  defined in a cylinder  500  of an engine. 
     The metering valve unit  50  adjusts an amount of fuel in the pressurizer chamber  14 , and the ECU  101  controls energization of the metering valve unit  50 . Because the ECU  101  is connected with the fuel pressure sensor  102  that is provided to the fuel rail  400 , the ECU  101  controls the energization of the metering valve unit  50  based on fuel pressure in the fuel rail  400 . 
     Next, a configuration of the high-pressure pump  10  will be described.  FIG. 2  is a schematic cross-sectional view illustrating the configuration of the high-pressure pump  10 . 
     As shown in  FIG. 2 , the high-pressure pump  10  mainly includes a housing body  11 . The housing body  11  is made of, for example, martensitic stainless steel. A cover  12  is attached to one side of the housing body  11  (upper side in  FIG. 2 ). Also, the plunger unit  30  is provided on the other side of the housing body  11  opposite from the cover  12 . Also, the metering valve unit  50  and the discharge valve unit  70  are arranged in a direction that is orthogonal to a direction, in which the cover  12  and the plunger unit  30  are arranged. 
     A fuel chamber  13  serving as a “receiver” is defined between the housing body  11  and the cover  12  in a state, where the cover  12  is attached to the housing body  11 . The fuel chamber  13  receives fuel that is supplied by the low-pressure pump  201  from the fuel tank  200  (see  FIG. 1 ). The fuel thus supplied into the fuel chamber  13  is pumped via the interior of the metering valve unit  50 , via the pressurizer chamber  14  provided around the center of the housing body  11 , and via the discharge valve unit  70  (see  FIG. 1 ), and then, is supplied to the fuel rail  400 . 
     Next, the plunger unit  30 , the metering valve unit  50 , and the discharge valve unit  70  will be describe in turn. 
     Firstly, the plunger unit  30  will be described. The plunger unit  30  includes the plunger  31 , a plunger supporter  32 , an oil seal  33 , a lower seat  34 , a lifter  35 , and a plunger spring  36 . 
     The housing body  11  defines therein a cylinder  15 . The cylinder  15  receives therein the plunger  31  such that the plunger  31  is reciprocably displaceable within the cylinder  15  in a longitudinal direction of the plunger  31 . The plunger supporter  32  is provided at a longitudinal end of the cylinder  15 . Thus, the plunger supporter  32  and the cylinder  15  support the plunger  31  such that the plunger  31  is reciprocable in the longitudinal direction. 
     The plunger  31  has one end adjacent the pressurizer chamber  14  and the other end remote from the pressurizer chamber  14 . The one end of the plunger  31  has an outer diameter similar to an inner diameter of the cylinder  15 . The other end of the plunger  31  has a diameter smaller than that of the one end of the plunger  31 . The plunger supporter  32  has a fuel seal  37  provided inside the plunger supporter  32 . The fuel seal  37  limits fuel leakage from the pressurizer chamber  14  to the engine. Also, the plunger supporter  32  has the oil seal  33  provided at an end of the plunger supporter  32 . The oil seal  33  limits oil from entering into the pressurizer chamber  14  from the engine. 
     The lower seat  34  is attached to the other end portion of the plunger  31  remote from the pressurizer chamber  14 , and the lower seat  34  integrates the lifter  35  with the plunger  31 . The lifter  35  is a hollow cylinder having an opening end on one side thereof and receives therein the plunger spring  36 . The plunger spring  36  has one end engaged with the housing body  11  and has the other end engaged with the lower seat  34 . 
     In the above configuration, the lifter  35  is in contact with a contact surface of the cam  301 , which is provided below the lifter  35 , and which is attached to the camshaft  300  (see  FIG. 1 ). Thus, the lifter  35  is reciprocably displaceable in the longitudinal direction in accordance with the cam profile of the cam  301  when the camshaft  300  rotates. Accordingly, the plunger  31  is reciprocably displaceable in the longitudinal direction. The plunger spring  36  is a return spring of the plunger  31  and urges the lifter  35  toward the contact surface of the cam  301 . 
     Next, the metering valve unit  50  will be described. 
     The metering valve unit  50  includes a tubular portion  51 , a valve unit cover  52 , a connector  53 , and a connector housing  54 . The tubular portion  51  is a part of the housing body  11 , and the valve unit cover  52  covers an opening of the tubular portion  51 . 
     The tubular portion  51  has a generally hollow cylindrical shape, and defines therein a fuel passage  55  and a communication passage  16  that communicates the fuel passage  55  with the fuel chamber  13 . Also, a rubber seal  17  is provided at an outer periphery of the tubular portion  51  in order to limit fuel leakage from the fuel passage  55 . The fuel passage  55  receives therein a seat body  56  that has a generally hollow cylindrical shape. The seat body  56  has a rubber seal  57  provided at an outer periphery of the seat body  56 , and the rubber seal  57  seals a clearance between the seat body  56  and an inner wall of the tubular portion  51 . Due to the above configuration, fuel flows inside the seat body  56 . 
     The seat body  56  receives therein an inlet valve  58 . The inlet valve  58  has a disc-shaped bottom portion  59  and a hollow cylindrical wall portion  60 . The bottom portion  59  and the wall portion  60  define therein an inner space, in which a spring  61  is received. The spring  61  has an end portion that is engaged or stopped by an engaging portion  62  that is located on a side of the inlet valve  58  toward the pressurizer chamber  14 . It should be noted that the engaging portion  62  is engaged with a snap ring  63  that is attached to an inner wall of the seat body  56 . 
     Also, the bottom portion  59  of the inlet valve  58  contacts a needle  64 . The needle  64  extends through the valve unit cover  52  and reaches a position inside the connector  53 . The connector  53  has a coil  65  and a terminal  53   a  that is used to energize the coil  65 . A stationary core  66 , a spring  67 , and a movable core  68  are provided at positions radially inward of the coil  65 . The stationary core  66  is held at a predetermined position. The movable core  68  is fixed to the needle  64  by welding. In other words, the movable core  68  is integral with the needle  64 . Also, the spring  67  has one end that is engaged with the stationary core  66  and has the other end that is engaged with the movable core  68 . 
     Due to the above configuration, when the terminal  53   a  of the connector  53  is energized, the coil  65  generates a magnetic flux that causes a magnetic attractive force formed between the stationary core  66  and the movable core  68 . As a result, the movable core  68  is moved toward the stationary core  66 , and thereby the needle  64  is moved in a direction away from the pressurizer chamber  14 . As a result, the inlet valve  58  becomes movable without limitation imposed by the needle  64 . Accordingly, the bottom portion  59  of the inlet valve  58  is movable to contact a seat part  69  of the seat body  56 . Thus, when the inlet valve  58  is seated on the seat part  69 , the fuel passage  55  is discommunicated from the pressurizer chamber  14 . In contrast, when the terminal  53   a  of the connector  53  is deenergized, the magnetic attractive force disappears, and thereby a biasing force of the spring  67  urges the movable core  68  to move in a direction away from the stationary core  66 . As a result, the needle  64  moves toward the pressurizer chamber  14 , and thereby the inlet valve  58  moves toward the pressurizer chamber  14 . In the above case, the bottom portion  59  of the inlet valve  58  is detached from the seat part  69 , and thereby the fuel passage  55  is communicated with the pressurizer chamber  14 . 
     Next, the discharge valve unit  70  will be described. The discharge valve unit  70  has a receiving portion  18 , a valve element  71 , a spring  72 , an engaging portion  73 , and a discharge port  74 . The receiving portion  18  is a cylindrical bore formed at the housing body  11 . 
     The receiving portion  18  defines therein a receiving chamber  19 . The receiving chamber  19  receives therein the valve element  71 , the spring  72 , and the engaging portion  73 . The valve element  71  is urged toward the pressurizer chamber  14  by a biasing force of the spring  72  that has one end engaged with the engaging portion  73 . Due to the above configuration, the valve element  71  closes an opening of the receiving chamber  19 , which opens to the pressurizer chamber  14 , while pressure of fuel in the pressurizer chamber  14  is low. As a result, the pressurizer chamber  14  is disconnected from the receiving chamber  19 . In contrast, when pressure of fuel in the pressurizer chamber  14  becomes greater, and thereby the fuel pressure exceeds the sum of the biasing force of the spring  72  and pressure of fuel in the fuel rail  400 , the valve element  71  moves toward the discharge port  74 . For example, the valve element  71  defines therein a space, through which fuel passes. When the fuel flows into the pressurizer chamber  14 , fuel is flows through the internal space of the valve element  71  and is discharged through the discharge port  74 . In other words, the valve element  71  functions as a check valve that is capable of stopping and allowing discharge of fuel. 
     Next, a block configuration of the fuel supply apparatus will be described with reference to  FIG. 3 . 
     As above, the fuel supply apparatus  100  includes the ECU  101 . The ECU  101  is electrically connected to the terminal  53   a  of the connector  53  and controls energization of the coil  65 . In other words the ECU  101  controls the displacement of the needle  64  of the metering valve unit  50 . 
     The fuel supply apparatus  100  includes the ECU  101  and the fuel pressure sensor  102 . For example, the ECU  101  is a microcomputer that has a CPU, a ROM, a RAM, an I/O, and a bus line connecting therebetween. The ECU  101  of the present embodiment has a fuel pressure controller  103  and a drive circuit  104 . 
     The fuel pressure sensor  102  is a sensor for measuring a pressure of fuel that is discharged from the discharge port  74  (see  FIG. 2 ). Accordingly, as above, the fuel pressure sensor  102  is provided to the fuel rail  400  that is located downstream of the discharge port  74  of the discharge valve unit  70 . The fuel pressure sensor  102  is not limited to be provided to the fuel rail  400 , but may be alternatively located at any position provided that the fuel pressure sensor  102  is capable of measuring or sensing pressure of pumped fuel. Then, the fuel pressure controller  103  receives signals from the fuel pressure sensor  102 . 
     The fuel pressure controller  103  controls the drive circuit  104  based on the signals from the fuel pressure sensor  102  such that fuel pressure becomes a target pressure. The drive circuit  104  is capable of energizing the high-pressure pump  10  with different drive electric currents (two values) in accordance with a drive signal from the fuel pressure controller  103 . 
     Next, an operation of the high-pressure pump  10  will be described with reference to  FIG. 4 . 
     When the camshaft  300  shown in  FIG. 1  rotates, the plunger  31  is reciprocably moved in the longitudinal direction as described above. The plunger  31  is reciprocable between a top dead center and a bottom dead center, and a position of the plunger  31  is indicated as a “cam lift” as shown in  FIG. 4 . In the present embodiment, (1) intake stroke, (2) return stroke, and (3) compression stroke in the operation will be separately described. 
     (1) Intake Stroke 
     While the plunger  31  is displaced toward the bottom dead center or is displaced downward in  FIG. 2 , the energization of the coil  65  is stopped. The above displacement occurs in a range from a cam angle of A to a cam angle of B in  FIG. 4 . In other words, the above displacement occurs in a range from the top dead center to the bottom dead center. Therefore, the inlet valve  58  is urged by the needle  64  that is integral with the movable core  68 , which is biased by the spring  67 , and thereby the inlet valve  58  is displaced toward the pressurizer chamber  14 . As a result, the inlet valve  58  is detached from or spaced from the seat part  69  of the seat body  56 , and thereby the fuel chamber  13  is communicated with the pressurizer chamber  14 . In the above state, the movable core  68  and the needle  64  are located at an “opening-side position”. Also, at this time, pressure in the pressurizer chamber  14  is reduced. Accordingly, fuel in the fuel chamber  13  is suctioned into the pressurizer chamber  14 . 
     (2) Return Stroke 
     When the plunger  31  starts moving from the bottom dead center toward the top dead center or starts moving upward in  FIG. 2 , fuel pressure in the pressurizer chamber  14  increases, and thereby the inlet valve  58  receives a force in a direction caused by fuel in the pressurizer chamber  14  such that the inlet valve  58  is urged to be seated on the seat part  69  of the seat body  56 . The above upward movement of the plunger  31  occurs in a range from the cam angle of B to a cam angle of D in  FIG. 4 . In other words, above upward movement of the plunger  31  occurs in a range from the bottom dead center to the top dead center. Because the inlet valve  58  is detached from the seat part  69  of the seat body  56  and thereby the inlet valve  58  is opened as above, the upward movement of the plunger  31  causes fuel in the pressurizer chamber  14  to flow back to the fuel chamber  13 , in contrast to the suction of the fuel in the intake stroke. 
     (3) Compression Stroke 
     When the coil  65  is energized during the return stroke, the magnetic field generated by the coil  65  forms a magnetic circuit. Accordingly, the magnetic attractive force is generated between the stationary core  66  and the movable core  68 . When the magnetic attractive force generated between the stationary core  66  and the movable core  68  becomes greater than the biasing force of the spring  67 , the movable core  68  is displaced toward the stationary core  66 . Thereby, the needle  64  that is integral with the movable core  68  is also displaced toward the stationary core  66 , and as a result, the inlet valve  58  is moved apart from the needle  64 . In the above state, the movable core  68  and the needle  64  are located at a “closing-side position”. As a result, the inlet valve  58  receives the biasing force of the spring  61  and pressure of fuel in the pressurizer chamber  14 , and thereby the inlet valve  58  becomes seated on the seat part  69  of the seat body  56 . The above operation corresponds to the cam angle of C in  FIG. 4 . 
     When the inlet valve  58  is seated on the seat part  69 , the fuel chamber  13  is disconnected from the pressurizer chamber  14 . The above disconnection ends the return stroke, in which fuel flows from the pressurizer chamber  14  to the fuel chamber  13 . Accordingly, by adjusting timing of performing the disconnection, an amount of fuel that is returned from the pressurizer chamber  14  to the fuel chamber  13  is adjusted, and also an amount of fuel that is compressed in the pressurizer chamber  14  is determined. 
     When the plunger  31  moves further toward the top dead center in a state, where the pressurizer chamber  14  is disconnected from the fuel chamber  13 , fuel pressure in the pressurizer chamber  14  further increases. The above further displacement of the plunger  31  corresponds to a range from the cam angle of C to the cam angle of D in  FIG. 4 . When fuel pressure in the pressurizer chamber  14  becomes equal to or greater than a predetermined pressure, the valve element  71  of the discharge valve unit  70  is displaced in a direction away from the pressurizer chamber  14 . Due to the above configuration, the pressurizer chamber  14  becomes communicated with the receiving chamber  19 , and thereby fuel compressed in the pressurizer chamber  14  is discharged through the discharge port  74 . The fuel discharged through the discharge port  74  is supplied to the injector  401  via the fuel rail  400  shown in  FIG. 1 . 
     When the plunger  31  reaches the top dead center (corresponding to the cam angle of D in  FIG. 4 ), the plunger  31  starts moving toward the bottom dead center or moves downwardly in  FIG. 2 . 
     It should be noted that when fuel pressure in the pressurizer chamber  14  reaches the predetermined value, the coil  65  is deenergized. When fuel pressure in the pressurizer chamber  14  increases, fuel on a side of the inlet valve  58  adjacent the pressurizer chamber  14  holds the inlet valve  58  seated on the seat part  69  of the seat body  56 . 
     By repeating the above strokes (1) to (3), the high-pressure pump  10  compresses suctioned fuel and discharges the compressed fuel. The discharge amount of fuel is adjusted by adjusting timing of energizing the coil  65  of the metering valve unit  50 . 
     The operation of the high-pressure pump  10  has been described as above. The present embodiment is characterized in timing of energizing the high-pressure pump  10 . Thus, the characteristic of the present embodiment will be described in comparison with a comparison example. 
       FIG. 5  is an explanatory diagram illustrating a comparison example. The explanatory diagram corresponds to a valve-closing operation of the inlet valve  58  at the cam angle of C in  FIG. 4 , and the inlet valve  58  is closed at time t 4  (see “inlet valve behavior” of  FIG. 5 ). 
     As appreciated from  FIG. 5 , firstly, two different drive signals, such as a first drive signal, a second drive signal, are outputted (see “first drive signal” and “second drive signal” of  FIG. 5 ). Then, the energization is made based on the drive signals in order to generate the attractive force to attract the movable core  68  (see “electric current” of  FIG. 5 ). Thus generated attractive force moves the needle  64 , and thereby the needle  64  that is integral with the movable core  68  reaches the closing side position. Then, the inlet valve  58  is closed (see “needle behavior” of  FIG. 5 ). 
     The fuel pressure controller  103  of the ECU  101  shown in  FIG. 3  outputs the first drive signal and the second drive signal to the drive circuit  104 . Then, the drive circuit  104  energizes the high-pressure pump  10 . The drive circuit  104  supplies a drive electric current that is changed in accordance with the first drive signal and the second drive signal from the fuel pressure controller  103 . More specifically, the drive circuit  104  supplies the drive electric current to the high-pressure pump  10  while the first drive signal is at a high level. In the above case, when the second drive signal indicates a high level, the drive circuit  104  energizes the high-pressure pump  10  with a first drive electric current that is relatively large. The first drive electric current corresponds to “the drive electric current of a first value (I 1  in FIG.  5 )”. In contrast, when the second drive signal indicates a low level, the drive circuit  104  energizes the high-pressure pump  10  with a second drive electric current that is relatively small. The second drive electric current corresponds to “the drive electric current of a second value (I 2  in FIG.  5 )” that is smaller than the first value. In detail, the first drive electric current is sufficient enough to displace the movable core  68  and the needle  64  from the “opening-side position” to the “closing-side position”. Also, the second drive electric current is sufficient enough to hold the movable core  68  and the needle  64  at the “closing-side position” such that the inlet valve  58  remains closed. As above, the drive circuit  104  energizes the high-pressure pump  10  by switching the drive electric current between the first drive electric current and the second drive electric current (between the first value and the second value). For example, when the inlet valve  58  is closed based on the energization with the first drive electric current, it is possible to maintain the inlet valve  58  closed without the energization with the first drive electric current, because the fuel pressure in the pressurizer chamber  14  has increased substantially by the time of closing the valve  58 . Thus, by energizing the high-pressure pump  10  with the second drive electric current, electric power consumption is saved effectively. Due to the above reason, the drive electric current is switched between the first drive electric current and the second drive electric current as necessary. 
       FIG. 5  will be described again. Because both the first drive signal and the second drive signal indicate the high level at time t 1 , the drive electric current of the drive circuit  104  starts rising at time t 1 . Then, during a period from time t 2  to time t 4 , the drive circuit  104  energizes the high-pressure pump  10  with the first drive electric current (I 1  in  FIG. 5 ), and during another period from time t 5  to time t 6 , the drive circuit  104  energizes the high-pressure pump  10  with the second drive electric current (I 2  in  FIG. 5 ). It should be noted that more specifically, the first drive electric current may be decreased temporarily as indicated by “d” in  FIG. 5  in accordance with the behavior of the needle  64 . When the drive circuit  104  starts energization at time t 1 , the magnetic attractive force is generated, and thereby the movable core  68  moves in a direction away from the pressurizer chamber  14 . Accordingly, the needle  64  moves with the movable core  68 . In  FIG. 5 , the movement of the needle  64  has completed at time t 3 . After the above, the inlet valve  58  that is not in contact with the needle  64  is closed at time t 4  (see “inlet valve behavior” of  FIG. 5 ), and thereby pressure in the pressurizer chamber  14  starts rising from time t 4  (see “pressure in pressurizer chamber” of  FIG. 5 ). 
     In the comparison example, the second drive signal becomes the low level at time t 4 , at which the inlet valve  58  gets closed. After this, the energization with the second drive electric current is performed during the period from time t 5  to time t 6  as above. The above operation is made because the inlet valve  58  is only required to be held closed once after the inlet valve  58  is moved to the valve-closing position. 
     However, in the comparison example, because the energization with the first drive electric current is maintained until time t 4 , at which the inlet valve  58  is fully closed, a travel speed of the needle  64  at time t 3  may be relatively large. The travel speed of the needle  64  corresponds to an inclination of a part indicated by K in the needle behavior chart in  FIG. 5 . Thus, for example, collision noise may be generated due to the collision between the stationary core  66  and the movable core  68 , and thereby noise of the needle  64  becomes larger disadvantageously in the comparison example. 
     In order to address the above disadvantages, an energization time period, in which the high-pressure pump  10  is energized, is adjusted in the present embodiment.  FIG. 6  is an explanatory diagram illustrating an operation of the fuel supply apparatus  100 . 
     In the above comparison example, the second drive signal is turned to the low level from the high level at time t 4 , at which the inlet valve  58  is closed. In contrast, in the present embodiment, the second drive signal is turned to the low level at time T 2 , at which the movement of the needle  64  toward the closing-side position has not been fully completed yet. Due to the above, a travel speed of the needle  64  after time T 2  is gradually reduced. The travel speed of the needle  64  corresponds to an inclination of a part indicated by K in the chart of the needle behavior in  FIG. 6 . The above operation may be referred as a “soft landing” of the needle  64 . Due to the above, for example, the collision noise between the stationary core  66  and the movable core  68  is effectively limited, and thereby the noise of the needle  64  is effectively reduced in the present embodiment. 
     When an “energization time period”, during which the second drive signal is kept at the high level, becomes shorter, displacement completion timing, at which the displacement of the needle  64  toward the closing-side position has been completed, may be delayed or retarded. As a result, valve-closing timing of fully closing the inlet valve  58  may be delayed. When the valve-closing timing of the inlet valve  58  is delayed, a time period for the return stroke of the high-pressure pump  10  (see the operation (2)) may become longer, and a time period for the compression stroke of the high-pressure pump  10  (see the operation (3)) may become shorter accordingly. In sum, discharge by the high-pressure pump  10  may fail when the energization time period is excessively short. 
       FIG. 7  is an explanatory diagram illustrating the above relation. According to  FIG. 7 , when the energization time period Tv exceeds TvA, a vibration amplitude sharply becomes larger or noise sharply becomes larger. However, when the energization time period is less than TvB, failure in the discharge by the high-pressure pump  10  may occur. Thus, in the present embodiment, the energization time period Tv is set such that the energization time period Tv stays within a range indicated by DD in  FIG. 7 . The setting of the energization time period Tv is executed by a learning control. 
     Next, the learning control of the energization time period Tv will be described. A control of the fuel pressure controller  103  illustrated in  FIG. 3  will be detailed. 
     In the ECU  101 , the fuel pressure controller  103  receives a signal from the fuel pressure sensor  102  that detects the fuel pressure, and the fuel pressure controller  103  outputs the first drive signal and the second drive signal to the drive circuit  104 . The fuel pressure controller  103  makes both the first drive signal and the second drive signal at the high level at time T 1  in  FIG. 6  in order to close the inlet valve  58 . The above timing of starting energization of the drive circuit  104  is defined as energization start timing that corresponds to time T 1 . The energization start timing is feed-back controlled such that the fuel pressure detected by the fuel pressure sensor  102  becomes the target pressure. Thus, when the fuel pressure detected by the fuel pressure sensor  102  decreases, time t 1  advances. In other words, the energization start timing is made to come earlier. 
     Hereinafter, the energization start timing, at which the first drive signal and the second drive signal from the fuel pressure controller  103  becomes the high level, is represented by “spill valve closing timing epduty”. It should be noted that the spill valve closing timing epduty corresponds to a cam angle (BTDC) that is based on the top dead center indicated as D in  FIG. 4 . For example, in  FIG. 4 , cam angle “D” corresponds to 0° CA and cam angle “A” corresponds to 180° CA indicating one cycle in a case, where the camshaft has two cams. Cam angle “A” is not limited to 180° CA but may be a different value depending on the number of cams. For example, cam angle “A” is 120° CA in another case, where the camshaft has three cams. Thus, when the energization start timing T 1  advances, the cam angle indicated by BTDC advances in a direction from D to A in  FIG. 4 . Thus, the spill valve closing timing epduty becomes greater when the energization start timing T 1  becomes earlier or advances. In contrast, the spill valve closing timing epduty becomes smaller when the energization start timing T 1  becomes delayed or retarded. The spill valve closing timing epduty corresponds to “energization start timing”. 
     In the present embodiment, the above configuration is applied. The energization time period Tv is gradually shortened from an initial value during a period from E 0  to E 1  in  FIG. 8 . The initial value may be set as a maximum value of the energization time period Tv, to which the initial value is changeable to the most. For example, the initial value may be set as a period from time t 1  to time t 4  of the comparison example illustrated in  FIG. 5 . 
     The shorter the energization time period Tv becomes, the earlier the second drive signal is changed to the low level from the high level. In other words, if the energization time period Tv is made shorter, a period before the second drive signal is switched to the low level from the high level is made shorter. Also, as described in the description of  FIG. 6 , when the energization time period is made short enough such that the second signal is changed to the low level from the high level before the displacement of the needle  64  is completed, valve-closing timing of the inlet valve  58  is delayed. As a result, the discharge amount is reduced, and thereby the fuel pressure detected by the fuel pressure sensor  102  is reduced. In the above case, the spill valve closing timing epduty is feed-back controlled to become larger during a period from E 1  to E 2  in  FIG. 8 . In other words, the “advancing” of the spill valve closing timing epduty is executed. 
     Furthermore, when the energization time period Tv is shortened further to a threshold value, the “advancing” of the spill valve closing timing epduty may not work to maintain the fuel pressure at a certain range. As a result, the fuel pressure may not be maintained at the target pressure (corresponding to E 2  in  FIG. 8 ). 
     As illustrated in  FIG. 7 , the spill valve closing timing epduty starts increasing when the energization time period Tv is shortened to a certain value in order to change the second drive signal to the low level before the displacement of the needle  64  is completed. The above certain value approximately corresponds to the energization time period TvA in  FIG. 7 . For example, when the energization time period Tv is reduced from a larger value to become smaller than the energization time period TvA, vibration sharply decreases. Also, when the energization time period Tv is further reduced, the fuel pressure starts decreasing even when the “advancing” of the spill valve closing timing epduty is executed. Thus, the threshold value of the energization time period corresponds to an energization time period TvB in  FIG. 7 . 
     In the present embodiment, the energization time period Tv at timing E 2  in  FIG. 8  is learned in a provisional learning operation. Then, in a main learning operation, the energization time period Tv is increased based on a half of an increase Δepduty of the spill valve closing timing epduty measured between E 1  and E 2  in  FIG. 8 . As a result, the energization time period Tv is set as a value that is approximately in a middle of the range DD in  FIG. 7 . 
     The above learning control of the present embodiment will be described with reference to a flow chart in  FIG. 9 . The process in the flow chart in  FIG. 9  is repeated at predetermined intervals in the present embodiment. 
     At S 100 , it is determined whether a learning condition is satisfied. The above determination at S 100  depends on whether a learning flag extv is ON. The learning flag extv is set as or turned to ON when the learning condition is satisfied in a process described later. When it is determined that the learning flag extv is ON, corresponding to YES at S 100 , control proceeds to S 110 , where the energization time period Tv is shortened. More specifically, at S 110 , the energization time period Tv is updated by subtracting a predetermined value from the current energization time period Tv. Then, control proceeds to S 120 . In contrast, when it is determined that the learning flag extv is OFF, corresponding to NO at S 100 , the learning control is ended. 
     At S 120 , it is determined whether the fuel pressure (epr) starts decreasing. The above determination process is made in order to determine timing E 2  in  FIG. 8 . When it is determined that the fuel pressure starts decreasing, corresponding to YES at S 120 , control proceeds to S 130 . In contrast, when it is determined that the fuel pressure is maintained at a constant value, corresponding to NO at S 120 , learning control is ended. 
     At S 130 , a provisional learning operation is executed. In the provisional learning operation, a provisional learning value Tvpre is set equivalent to the current energization time period Tv. Then, control proceeds to S 140 , where the main learning operation is executed. In the main learning operation, a main learning value Tvcal is obtained by adding a return value M to the provisional learning value Tvpre. For example, the return value M corresponds to the half of the increase Δepduty of the spill valve closing timing epduty measured between E 1  and E 2  in  FIG. 8 . 
     Then, control proceeds to S 150 , where the spill valve closing timing epduty is updated. More specifically, the changed spill valve closing timing epduty is stored because the spill valve closing timing epduty is “advanced”. Also, the learning flag extv is turned to OFF. 
     Then, control proceeds to S 160 , where a new energization time period Tv is set as the learning value Tvcal. Then, the learning control is ended. 
     Then, a learning condition determination operation will be described with reference to  FIG. 10 . In the learning condition determination operation, it is determined whether the learning condition is satisfied. In other words, when it is determined that the learning condition is satisfied in the learning condition determination operation, the learning flag extv is set as ON. 
     At S 200 , it is determined whether the learning flag extv is ON. When it is determined that the learning flag extv is ON, corresponding to YES at S 200 , the following process is not executed, and the learning condition determination operation is ended. In contrast, when it is determined that the learning flag extv is OFF, corresponding to NO at S 200 , control proceeds to S 210 . 
     At S 210 , it is determined whether the engine is operated under a steady state operation. The above determination is made whether both an engine rotational speed and an engine load are equal to or less than predetermined values. Alternatively, the steady state operation may be determined depending one whether the engine is operated under a stand-by or idling operation. More specifically, it may be determined whether the vehicle speed is “0” while the accelerator pedal is not pressed. Furthermore, in order to determine the steady state operation, alternatively, it may be determined whether the fuel pressure is equal to or less than a predetermined value, or it may be determined whether a VCT is not driven. When it is determined that the engine is operated under the steady state operation, corresponding to YES at S 210 , control proceeds to S 220 . In contrast, when it is determined that the engine is not operated under the steady state operation, corresponding to NO at S 210 , the following process is not executed, and the learning condition determination operation is ended. 
     At S 220 , it is determined whether an engine coolant temperature is equal to or greater than a predetermined value S 0 . When it is determined that the engine coolant temperature≧S 0 , corresponding to YES at S 220 , control proceeds to S 230 , where the learning flag extv is set as ON, and then the learning condition determination operation is ended. In contrast, when it is determined that the engine coolant temperature&lt;S 0 , corresponding to NO at S 220 , a process at S 230  is not executed and the learning condition determination operation is ended. 
     In the present embodiment, the learning operation is executed when the engine is operated under the steady state operation (S 210  in  FIG. 10 ). In other words, the condition for executing the learning operation includes that the engine is continuously operated under the steady state. The reason of having the above condition will be described below. Firstly, a (A) relation between the engine rotational speed and the learning condition will be described, and next, a (B) relation between the engine load and the learning condition will be described. 
     (A) Relation between Engine Rotational Speed and Learning Condition 
     As illustrated in  FIG. 11A , it is known that when a pump rotational speed Np becomes higher, a valve-closing force that causes the inlet valve  58  to be closed becomes larger accordingly. The pump rotational speed Np may be a rotational speed of the camshaft. In other words, when the pump rotational speed Np becomes greater, a speed in increase of the pressure in the pressurizer chamber  14  caused by the plunger  31  becomes greater. As a result, the valve-closing force of the inlet valve  58  is increased. In general, the pump rotational speed Np is proportional to an engine rotational speed NE. As shown in  FIG. 11B , a vibration amplitude becomes greater when the engine rotational speed NE increases, because the increase of the engine rotational speed NE causes the pump rotational speed Np to increase, and thereby the valve-closing force is increased. In other words, the noise increases with the increase of the engine rotational speed. Furthermore, as shown in  FIG. 11B , when the engine rotates at a low speed, the vibration amplitude is limited from increasing. More specifically, when the engine is idle or operated under the stand-by operation, the vibration does not deteriorate, and also the vibration does not quickly deteriorate immediately after the travel of the vehicle. Then, because the valve-closing force increases as shown in  FIG. 11A  when the pump rotational speed Np increases, the valve-closing timing of the inlet valve  58  advances. As a result, even if the energization time period Tv, which has been learned while the engine is operated at the low speed, is used for the engine at the high speed, failure of the discharge is limited from occurring. Due to the above reasons, the learning control may be performed when the engine rotational speed is equal to or less than the predetermined value. 
     (B) Relation between Engine Load and Learning Condition 
       FIG. 12A  is a diagram illustrating a cam speed, corresponding to a speed of the plunger  31 , indicated by a dashed curved line, and the cam speed is overlapped on the cam lift of  FIG. 4  indicated by a solid curved line. In  FIG. 12A , cam angles employed in the operation with different engine load are indicated by H 1 , H 2 , and H 3 , More specifically, cam angle H 1  corresponds to the lowest engine load, cam angle H 2  corresponds to a second lowest engine load, and cam angle H 3  corresponds to the highest engine load. As illustrated in  FIG. 12A , the cam speed increases with an increase of the engine load. At the above case,  FIG. 12B  illustrates a relation between a load ratio of the engine and the vibration amplitude for one case, where the engine rotational speed NE is low and also illustrates the relation for another case, where the engine rotational speed NE is high. In a case, where the engine rotational speed NE is low, the vibration amplitude does not increase very much or the vibration amplitude remains almost the same even when the load becomes larger. Also, in a case, where the engine rotational speed NE is high, the vibration amplitude increases slightly when the load becomes greater. Also, even when the energization time period Tv, which is learned while the engine load is low, is used when the engine load is high, failure of the discharge is limited from occurring similar to the case of the above described engine rotational speed. Due to the above reasons, when the engine load is equal to or less than a predetermined value, the learning control may be executed. 
     As described in the above (A) and (B) relations, it may be appropriate to satisfy the learning condition when both the engine rotational speed and the engine load are equal to or less than the predetermined values. 
     The satisfaction of the learning condition may be determined using the engine rotational speed and the engine load for each of multiple operational conditions of the engine. For example, as shown in  FIG. 13A , the engine rotational speed NE may be categorized into one of four ranges, and the engine load KL may be categorized into one of four ranges. Thus, 16 operational ranges in total are prepared as a result of the above segmentation, and the learning operation is executed for each of the operational ranges. As a result, it is possible to set the energization time period Tv more appropriately. 
     As above, even in a case, where the energization time period Tv, which is learned while the engine rotational speed is low, is used while the engine rotational speed is high, failure of the discharge is effectively limited from occurring. Also, even in another case, where the energization time period Tv, which is learned while the engine load is low, is used while the engine load is high, failure of the is effectively limited from occurring. As a result, in a configuration, where the learning operation is executed for each of the multiple operational conditions, a learning value, which is learned in one operational condition, may be used in another operational condition that is in a higher rotational range or in a higher load range compared with the one operational condition. Specifically, when the engine rotational speed is NE 1  and the engine load is KL 1 , the learning operation is performed in an operational range X indicated by lined-hatching as shown in  FIG. 13B . Thus, the learning value in the operational range X may be used in five other operational ranges Y indicated by dotted-hatching. The five other operational ranges Y are located on a side of the operational range X in a range higher in the rotational speed and higher in the load. In  FIG. 13B , a learning value Tv 1  is set for both the operational range X and the operational range Y. 
     A learning operation executed under a further lower-speed and lower-load operational condition will be described with reference to  FIGS. 14A and 14B . In one example case of the lower-speed and lower-load operational condition, the engine rotational speed NE indicates the engine rotational speed NE 2  ( FIGS. 14A ,  14 B) that is further smaller than the engine rotational speed NE 1  ( FIG. 13B ), and the engine load KL indicates the engine load KL 2  ( FIGS. 14A ,  14 B) that is further smaller than the engine load KL 1  ( FIG. 13B ). 
     In an operational range Z that corresponds to the above example case, a learning value may indicate Tv 2 , Because the learning value Tv 2  is smaller than the learning value Tv 1  normally, the learning value Tv 2  may be used in 15 operational ranges W 1  that is indicated by dotted-hatching. The operational ranges W 1  are located on a side of the operational range Z in a range higher in the rotational speed and higher in the load as shown in  FIG. 14A . 
     In contrast, if the learning value Tv 2  is equal to or greater than the learning value Tv 1 , the learning value Tv 2  may be used in alternative ranges W 2  indicated by dotted-hatching in  FIG. 14B . As shown in  FIG. 14B , the ranges W 2  include nine operational ranges that are located on a side of the operational range Z in a range higher rotational speed and higher in the load. Thus, the ranges W 2  are part of the operational ranges W 1  in  FIG. 14A  but are different from the other part of the operational ranges W 1 , which have the learning value Tv 1 . 
     As above, the execution of the learning operation for each of the operational conditions based on the engine rotational speed and the engine load has been described. However, when the satisfaction of the learning condition is determined using the engine coolant temperature as described in S 220  in  FIG. 10 , the learning operation may be executed for each of multiple engine coolant temperatures. Specifically, multiple coolant temperature ranges may be set as follows, and the learning operation may be executed for each of the coolant temperature ranges. 
       FIG. 15  is a flow chart illustrating a learning condition determination operation for determining whether the learning condition is satisfied for each of the engine coolant temperatures. 
     At S 300 , it is determined whether the learning flag extv is ON. The process at S 300  is similar to that at S 200  of  FIG. 10 . When it is determined that the learning flag extv is ON, corresponding to YES at S 300 , the following process will not be executed, and the learning condition determination operation is ended. In contrast, when it is determined that the learning flag extv is OFF, corresponding to NO at S 300 , control proceeds to S 310 . 
     At S 310 , it is determined whether the engine is operated under the steady state operation. The process at S 310  is similar to that at S 210  of  FIG. 10 . When it is determined that the engine is operated under the steady state operation, corresponding to YES at S 310 , control proceeds to S 320 . In contrast, when it is determined that the engine is not operated under the steady state operation, corresponding to NO at S 310 , the following process is not executed, and the learning condition determination operation is ended. 
     At S 320 , it is determined whether the engine coolant temperature is in a first range. In other words, it is determined at S 320  whether the coolant temperature is equal to or higher than S 2  and also is equal to or lower than S 1  (S 1 ≧coolant temperature≧S 2 ). When it is determined that the coolant temperature is in the first range, corresponding to YES at S 320 , control proceeds to S 350 , where a coolant temperature condition flag extv 1  is set as ON. Then, control proceeds to S 380 . In contrast, when it is determined that the coolant temperature is not in the first range, corresponding to NO at S 320 , control proceeds to S 330 . 
     At S 330 , it is determined whether the engine coolant temperature is in a second range. In other words, it is determined at S 330  whether the engine coolant temperature is equal to or higher than S 4  and also is equal to or lower than S 3  (S 3 ≧coolant temperature≧S 4 ). When it is determined that the coolant temperature is in the second range, corresponding to YES at S 330 , control proceeds to S 360 , where a coolant temperature condition flag extv 2  is set as ON, and then, control proceeds to S 380 . In contrast, when it is determined that coolant temperature is not in the second range, corresponding to NO at S 330 , control proceeds to S 340 . 
     At S 340 , it is determined whether the engine coolant temperature is in a third range. In other words, it is determined at S 340  whether the engine coolant temperature is equal to or higher than S 6  and also is equal to or lower than S 5  (S 5 ≧coolant temperature≧S 6 ). When it is determined that the coolant temperature is in the third range, corresponding to YES at S 340 , control proceeds to S 370 , where a coolant temperature condition flag extv 3  is set as ON, and then, control proceeds to S 380 . In contrast, when it is determined that the coolant temperature is not in the third range, corresponding to NO at S 340 , the learning condition determination operation is ended. 
     At S 380 , to which control proceeds from S 350 , S 360 , and S 370 , the learning flag extv is set as ON, and then the learning condition determination operation is ended. At S 380 , the learning flag extv is set as ON when the coolant temperature falls within one of the first to third ranges. Thus, the learning flag extv of ON indicates that the learning condition is satisfied. 
     In a case, where the above learning condition determination operation is performed, the processes at S 120  to S 150  indicated by the dashed line in the learning operation shown in  FIG. 9  are executed for each of the coolant temperature ranges, such as the first range, the second range, and the third range. More specifically, a learning operation is performed to store the learning value when the coolant temperature condition flag extv 1  is ON. Another learning operation is performed to store the learning value, when the coolant temperature condition flag ectv 2  is ON. And still another learning operation is performed to store the learning value, when the coolant temperature condition flag extv 3  is ON. 
     As detailed above, in the present embodiment, the second drive signal is changed to the low level at time T 2 , at which the movement of the needle  64  has not been completed (see  FIG. 6 ). Due to the above, the travel speed of the needle  64  starts decreasing gradually after time T 2 . The above travel speed of the needle  64  corresponds to the inclination of a part indicated by K in  FIG. 6 . In other word, the needle  64  is capable of soft landing. As a result, for example, the movable core  68  is capable of soft landing on the surface of the stationary core  66 , and thereby collision noise between the stationary core  66  and the movable core  68  is regulated. As a result, it is possible to effectively reduce the noise of the needle  64 . 
     Also, in the present embodiment, the energization time period Tv is gradually shortened by repeating the process at S 110  of  FIG. 9 , the learning operation is executed at S 130  and S 140 , and then the energization time period Tv is set at S 160 . Due to the above, it is possible to appropriately set the energization time period Tv, and thereby it is possible to effectively reduce the noise of the needle  64 . Furthermore, in the learning control, it is determined whether the fuel pressure is reduced at S 120  of  FIG. 9 , and then the learning operation is executed at S 130  and S 140 . As a result, it is possible to identify the lower limit value of the energization time period Tv, and thereby it is possible to appropriately set the energization time period Tv. 
     Furthermore, also, in the present embodiment, it is determined whether the engine is operated under the steady state operation, and further, the learning control is executed when the engine coolant temperature is equal to or greater than S 0 . By executing the learning control when the engine has been continuously operated under the steady state, it is possible to appropriately set the energization time period Tv. The above is done because the appropriate energization time period may change when the operational condition changes. In the present embodiment, it may be additionally determined whether the operational condition substantially changes. Thus, alternatively, the learning control may be ended when it is determined that the operational condition substantially changes during the execution of the learning control. 
     Also, in the present embodiment, the initial value of the energization time period Tv is set as the maximum value, and the energization time period Tv is gradually shortened in the learning control. Thus, it is possible to set the energization time period Tv to a value in order to avoid causing the failure in the discharge. 
     Also, as described with reference to  FIG. 13A  to  FIG. 14B , the learning control is executed for each of the operational ranges. As a result, it is possible to appropriately set the energization time period Tv in accordance with various operational conditions, and thereby the noise of the needle  64  is effectively reduced. If the learning control is once executed for one operational range to obtain the energization time period Tv, the obtained energization time period Tv may be used in the other operational ranges located on a side of the one operational range in a range higher in the rotational speed and higher in the load ( FIG. 13B , see  FIG. 14 ). Then, it is not required to execute the learning control for all of the operational ranges advantageously. 
     Second Embodiment 
     The second embodiment of the present invention is different from the first embodiment in the learning control. In the present embodiment, parts of the embodiment that are different from the first embodiment will only be described, and thereby explanation of the similar configuration of the present embodiment similar to the first embodiment will be omitted. Also, similar components are indicated by the same numerals. 
     Also in the present embodiment, as shown in  FIG. 16 , the energization time period Tv is gradually reduced from the initial value. The initial value at E 4  corresponds to the maximum value of the energization time period Tv similar to the first embodiment, and the initial value may be set as the period from time t 1  to time t 4  shown in the comparison example of  FIG. 5 , for example. 
     The shortening of the energization time period Tv corresponds to the shortening of a certain time period, for which the second drive signal is kept at the high level and then changed to the low level after the certain time period has elapsed. Then, as described in the above explanation of  FIG. 6 , when the energization time period Tv is shortened, the valve-closing timing of the inlet valve  58  is delayed or retarded. Accordingly, the discharge amount is decreased, and thereby the spill valve closing timing epduty increases (E 5  in  FIG. 16 ). 
     In the first embodiment, when the fuel pressure (epr) actually starts decreasing (E 2  in  FIG. 8 ), the learning operation is executed based on increase Δepduty of the spill valve closing timing epduty. In contrast, in the present embodiment, when the fuel pressure reaches a predetermined value (E 7 ) after the fuel pressure starts decreasing (E 6  in  FIG. 16 ), the energization time period Tv is set as a provisional learning value Tvpre. Then, a main the learning value Tvcal is computed by adding a predetermined time period to the provisional learning value Tvpre. The predetermined time period is determined such that the main the learning value Tvcal falls within a variable range of the energization time period Tv during a time period from E 5  to E 6  in  FIG. 16 . 
     In the present embodiment, the advantages achievable in the first embodiment are also achieved. 
     Third Embodiment 
     The third embodiment is different from the above embodiments in the learning control. In the present embodiment, parts of the embodiment that are different from the of the present embodiment similar to the above embodiments will be omitted. above embodiments will only be described, and thereby explanation of the similar configuration Also, similar components are indicated by the same numerals. 
     In the present embodiment, the fuel supply apparatus  100  includes a vibration sensor  105  that is indicated by a dashed line in  FIG. 3 . The vibration sensor  105  is provided to the stationary core  66  of the high-pressure pump  10  as indicated by a dashed line in  FIG. 2  and detects vibration of the high-pressure pump  10 . Alternatively, a knock sensor  105   a  may be provided to the cylinder  500  of the engine as indicated by a dashed line in  FIG. 1  in order to detect the knock of the engine. The vibration sensor  105  outputs signals to the fuel pressure controller  103 . 
     In the present embodiment, as shown in  FIG. 17 , the energization time period Tv is gradually shortened from the initial value. The initial value corresponds to the maximum value of the energization time period Tv similar to the above embodiments. The initial value of the energization time period Tv at E 9  may be, for example, the period from time t 1  to time t 4  of the comparison example of  FIG. 5 . 
     The shortening of the energization time period Tv corresponds to the gradually shortening of the certain time period, for which the second signal is kept at the high level and then the second signal is changed to the low level after the certain time period has elapsed. As shown in  FIG. 7 , when the energization time period Tv is reduced to become close to TvA, the vibration amplitude sharply decreases. 
     In the present embodiment, when a vibration level detected by the vibration sensor  105  is equal to or lower than a predetermined value, the learning value is set as the energization time period Tv at the time of detection (E 10  in  FIG. 17 ). It should be noted that as shown by a dashed line in  FIG. 17 , if the energization time period Tv were decreased continuously, the vibration level would be decreased to a certain level. Also, the fuel pressure (epr) would be also decreased (E 11 ). Thus, the predetermined value used for determining the vibration level is set as a value that is limited from causing the decrease in the fuel pressure. 
     In the present embodiment, the advantages achievable in the above embodiments will be also achieved. 
     Fourth Embodiment 
     The fourth embodiment is different from the above embodiments in the learning control. In the present embodiment, parts of the embodiment that are different from the above embodiments will only be described, and thereby explanation of the similar configuration of the present embodiment similar to the above embodiments will be omitted. Also, similar components are indicated by the same numerals. 
     In the present embodiment, the fuel supply apparatus  100  includes an electric current sensor  106  indicated by a dashed line in  FIG. 3 . The electric current sensor  106  detects the drive electric current outputted by the drive circuit  104 . The electric current sensor  106  outputs signals to the fuel pressure controller  103 . 
     The drive electric current changes with a behavior of the needle  64  as shown by “d” in the comparison example in  FIG. 5 . More specifically, when the needle  64  is displaced to be closer to the closing-side position, the drive electric current decreases or drops. When the energization time period Tv is further shortened, the occurrence of the drop in the drive electric current is delayed. 
     In the present embodiment, when the delay of the drop d of the drive electric current detected by the electric current sensor  106  becomes equal to or greater than a predetermined value, the learning value is set as an energization time period Tv of the time of the detection. It should be noted that if the energization time period Tv were shortened further continuously, the needle  64  would not be able to reach the closing-side position or would not be attracted to be displaced to the closing-side position. As a result, the drop of the drive electric current is limited from occurring. However, the fuel pressure decreases accordingly. Thus, for example, the predetermined value used for determining the delay of the drop of the drive electric current is set in a magnitude that is limited from causing the decrease in the fuel pressure. 
     In the present embodiment, the advantages achievable in the above embodiments are also achieved. 
     It should be noted that, in the first to fourth embodiments, the fuel chamber  13  functions as a “receiver”, the inlet valve  58  functions as a “valve member”, the needle  64  and the movable core  68  function as a “movable unit”, the discharge valve unit  70  functions as a “discharge unit”, the fuel pressure sensor  102  functions as “fuel pressure detection portion”, the fuel pressure controller  103  functions as “drive control portion”, the drive circuit  104  functions as “drive circuit portion”, the vibration sensor  105  functions as “vibration detection portion”, and the electric current sensor  106  functions as “electric current detection portion”. 
     Other Embodiment 
     in the first embodiment, it is determined at S 120  in  FIG. 9  whether the fuel pressure decreases, and then, the main learning operation is executed at S 140  based on the increase Δepduty of the spill valve closing timing epduty. Alternatively, the provisional learning operation and the main learning operation may be executed based on the increase Δepduty of the spill valve closing timing epduty. Specifically, when the increase Δepduty exceeds the predetermined amount, the provisional learning operation is executed, for example, and the return value, which corresponds to a half of the increase (½×Δepduty), may be added to the provisional learning value. When the learning control is executed based on the spill valve closing timing epduty as above, the provisional learning operation may be omitted similar to the third embodiment, and the main learning operation may be executed when the increase Δepduty becomes equal to or greater than a predetermined amount. 
     In the above embodiments, the engine rotational speed, the engine load, and the engine coolant temperature are used as a parameter for defining the operational ranges for the operational condition. Alternatively, a temperature of an engine oil may be used as a parameter for the operational condition. 
     Also, the determination of whether the engine has been continuously operated under the steady state may be made based on the above operational condition. Alternatively, the determination of the operation under the steady state may be made whether at least one of a battery voltage, a fuel temperature, a fuel pressure, and a degree of viscosity of fuel is with in a predetermined range. 
     Also, a fuel pressure condition may be employed as the learning condition. For example, fuel pressure decreases in the learning control as in a case, where the decrease of the fuel pressure by a predetermined amount is detected in the second embodiment. Thus, the combustion may deteriorate accordingly. Thus, the learning condition may include that the fuel pressure is substantially high. Also, in the first and third embodiments, the learning condition may include that the fuel pressure is substantially high. In contrast, when the learning control is executed to obtain the energization time period while the fuel pressure is low, the obtained energization time period is also used for the operation under the high fuel pressure. Thus, in the first and third embodiments, the learning condition may include that the fuel pressure is low. 
     The fuel pressure sensor  102  is employed in the first and second embodiments, the vibration sensor  105  is employed in the third embodiment, and the electric current sensor  106  is employed in the fourth embodiment in order to executed the learning control. Alternatively, two or more of the above sensors  102 ,  105 ,  106  may be employed for the execution of the learning control. Also, one of the above sensors  102 ,  105 ,  106  may be mainly employed, and the other one or two sensors may be complementarily employed. More specifically, the fuel pressure sensor  102  is mainly used, and the vibration sensor  105  or the electric current sensor  106  may be complementarily used. Also, as shown in  FIG. 18A , the vibration sensor  105  may be mainly used, and the electric current sensor  106  or the fuel pressure sensor  102  may be complementarily used. Also, as shown in  FIG. 18B , the electric current sensor  106  is mainly used, and the fuel pressure sensor  102  or the vibration sensor  105  may be complementarily used. 
     The present invention is not limited to the above embodiments, and may be modified in various ways provided that the modification does not deviate from the gist of the present invention.