JP5003720B2 - Fuel pumping system - Google Patents

Description

  The present invention relates to a fuel pumping system that pressurizes and pressurizes fuel, and is particularly suitable for use in pumping fuel for combustion in an internal combustion engine.

  This type of fuel pumping system includes a cylinder and a plunger that form a pressure chamber inside. The fuel is sucked into the pressure chamber from the low pressure passage as the plunger is lowered, and the fuel in the pressure chamber is pressurized as the plunger is raised. The structure which discharges to a high voltage | pressure channel is known (refer patent document 1).

JP 2009-057885 A

  Then, the present inventor has studied a configuration that includes a metering valve that opens and closes a discharge port that discharges fuel in the pressure chamber to the low-pressure passage and adjusts (meters) the amount discharged by the plunger ascending as follows. . That is, the maximum amount of fuel is sucked when the plunger is lowered. Then, fuel is discharged from the discharge port during a predetermined metering period from the start of raising the plunger, and the fuel in the pressure chamber is metered. At this point, the current flowing to the metering valve is zero, and then the metering valve is closed by flowing a valve closing current to the metering valve to end the metering period, and the fuel is pressurized in the pressure chamber. To start.

  However, in the configuration based on the above study, when the valve closing current is supplied to end the metering period, a certain electromagnetic force is required to ensure the valve closing response of the metering valve. Therefore, there is a limit to downsizing the electromagnetic solenoid while securing a certain electromagnetic force, and there is a limit to reducing the physique of the metering valve.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel pumping system in which a metering valve is miniaturized.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

According to the first aspect of the present invention, a cylinder that forms a pressure chamber therein, a lowering of the inside of the cylinder (moving in a direction in which the pressure chamber is expanded), the fuel is sucked into the pressure chamber from the low pressure passage, and the inside of the cylinder is raised ( A plunger that moves the pressure chamber in a direction to reduce the pressure chamber and pressurizes the fuel in the pressure chamber and discharges it to the high-pressure passage; and a metering valve that opens and closes the discharge port that discharges the fuel in the pressure chamber to the low-pressure passage. Assuming Then, fuel is discharged from the discharge port during a predetermined metering period from the start of raising the plunger, the fuel in the pressure chamber is metered, and the metering valve is closed by supplying a valve closing current to the metering valve. In a fuel pumping system that ends the metering period and starts pressurizing the fuel in the pressure chamber, an intake port for sucking fuel from the low pressure passage to the pressure chamber is provided, and the suction port is separated by a suction valve different from the metering valve. was opened and closed, the falling period of the plunger sucks fuel from the suction port, prior to passing the closing current, pilot current of low current to flow to the metering valve than valve closing current, the metering valve is closed It has a spring for applying an elastic force on the valve side, and is configured to open the valve against the elastic force by receiving the fuel pressure in the pressure chamber .

According to this, since the valve closing current flows while the pilot current is flowing, the electromagnetic force of the metering valve is larger than when the valve closing current flows when the current flowing to the metering valve is zero. The rise of generation can be made faster. Therefore, the valve closing response of the metering valve can be improved without increasing the electromagnetic force generation capability by increasing the size of the electromagnetic solenoid or the like. That is, it is possible to reduce the size of the electromagnetic solenoid or the like while ensuring the valve closing response of the metering valve, and to reduce the size of the metering valve.
Here, contrary to the above-described invention, when the metering valve is opened during the descending period and the fuel is sucked from the discharge port, the maximum stroke of the metering valve is set so that a sufficient amount of fuel can be sucked. The amount needs to be increased. Then, securing the stroke amount becomes a restriction for downsizing the metering valve. On the other hand, according to the above invention, since the suction port is opened by the suction valve different from the metering valve and the suction is performed, the maximum stroke amount of the metering valve can be set small. Therefore, further miniaturization of the metering valve can be achieved.
Further, for example, when the plunger is driven by the internal combustion engine, when the internal combustion engine stops while the plunger is moving up and the energization amount to the metering valve becomes zero, the metering valve is operated by the spring. Is closed, so that the pressurized state in the pressure chamber is maintained. Therefore, when the internal combustion engine is started next time, the fuel can be pressurized and fed immediately.

In the second aspect of the present invention, the metering valve is configured to have a valve body for opening and closing the stator, armature, and a discharge port operates in conjunction with an armature having an electromagnetic solenoid, the pilot current is not flowing pilot current Compared to the case , the armature is driven during the metering period so as to reduce the air gap provided between the stator and the armature.

  According to this, since the valve closing current flows in a state where the air gap is small due to the pilot current, the valve closing response of the metering valve is not increased by increasing the electromagnetic force generation capacity by increasing the size of the electromagnetic solenoid or the like. Can be improved. Further, since the valve closing operation is performed from the state in which the armature is driven so as to reduce the air gap, the operation stroke of the metering valve required for the valve closing can be shortened. Therefore, the valve closing response of the metering valve can be improved without increasing the electromagnetic force generation capability by increasing the size of the electromagnetic solenoid or the like. As mentioned above, according to the said invention, the further miniaturization of a metering valve can be achieved.

The figure which shows the whole structure of the fuel pumping system concerning 1st Embodiment of this invention. It is a figure which shows the action | operation of a plunger, a metering valve, etc. which are shown in FIG. The time chart explaining the action | operation of the high pressure pump at the time of discharge. The flowchart which shows the calculation procedure of the metering period (metering control period) by ECU. The flowchart which shows the control procedure of the metering valve by ECU. The time chart explaining the action | operation of a high pressure pump when the discharge amount is zero. The figure which shows the high pressure pump concerning 2nd Embodiment of this invention.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
The fuel pumping system according to the present embodiment is applied to a fuel injection device that injects fuel to be used for combustion of a diesel engine (internal combustion engine). First, the configuration of the fuel injection device and the fuel pumping system will be described with reference to FIG.

  As shown in the figure, the fuel in the fuel tank 5 that stores the fuel is pumped up by the fuel pump 10 and is pumped to the common rail 42 (pressure accumulating vessel) through the high-pressure passage 41. The common rail 42 stores the pumped high-pressure fuel and supplies the high-pressure fuel to the fuel injection valve 43 of each cylinder. The tip of the fuel injection valve 43 is disposed so as to protrude into a combustion chamber (not shown) of the diesel engine, and fuel can be injected and supplied into the combustion chamber. The operation of the fuel injection valve 43 is controlled by an electronic control unit (ECU 44) based on the driver's accelerator pedal operation amount and the like. The fuel leaking from the fuel injection valve 43 is returned to the fuel tank 5 through the return passage 45.

  The common rail 42 is provided with a pressure reducing valve 46 that communicates and blocks the inside of the common rail 42 and the return passage 45. The common rail 42 is provided with a fuel pressure sensor 47 that detects the fuel pressure inside the common rail 42. The detection value of the fuel pressure sensor 47 and various detection values such as the accelerator operation amount and the engine rotation speed are taken into the ECU 44. The ECU 44 includes a central processing unit and an appropriate memory, and controls the operation of various actuators such as a metering valve ★, a pressure reducing valve 46, and a fuel injection valve 43, which will be described later, based on detection values of various sensors. To do.

  The fuel pump 10 includes a low-pressure pump 11 that pumps the fuel in the fuel tank 5 and a high-pressure pump 12 that pumps the fuel sent from the low-pressure pump 11 to the outside. The high-pressure pump 12 is configured to accommodate the plunger body 14 in a reciprocating manner inside the cylinder body 13. The cylinder body 13 has a plurality of (two in the example of FIG. 1) cylinders 15, and the plunger body 14 has a plunger 16 that reciprocates in the cylinder 15. The cylinder 15 forms a pressure chamber 15a therein. When the plunger 16 rises in the cylinder 15, the pressure chamber 15a is compressed, and when the plunger 16 descends, the pressure chamber 15a expands and expands.

  In the internal space 14a of the plunger body 14, a rotating body 17 connected to the output shaft (crankshaft) of the internal combustion engine is provided. Then, the plunger body 14 is pushed and moved back and forth by the rotating body 17 rotating eccentrically. Therefore, the plurality of plungers 16 repeat descending and ascending alternately. When the plunger 16 moves (lowers) from the top dead center to the bottom dead center, the fuel in the low pressure passage 18 sent from the low pressure pump 11 is sucked into the plurality of pressure chambers 15a. When the plunger 16 moves (rises) from the bottom dead center to the top dead center, the sucked fuel in the pressure chamber 15 a is pressurized by the plunger 16 and is pumped to the high pressure passage 41. Thus, although the high pressure pump 12 is driven by the output of the internal combustion engine, the low pressure pump 11 is also rotationally driven by the output of the internal combustion engine together with the high pressure pump 12.

  Next, the structure of the high-pressure pump 12 will be described in more detail with reference to FIG. Since the plurality of cylinders 15 and plungers 16 all have the same structure, FIG. 2 shows one cylinder 15 and plunger 16. FIG. 2A shows an operating state during the intake period in which fuel is sucked into the pressure chamber 15a, and FIG. 2B shows a metering amount for adjusting the amount of fuel (discharge amount) in the pressure chamber 15a. FIG. 2 (c) shows the operation during the pumping period in which the metered fuel in the pressure chamber 15a is pressurized and pumped.

  The cylinder 15 is formed with a discharge port 15 b for discharging the fuel in the pressure chamber 15 a to the low pressure passage 18, and the discharge port 15 b is opened and closed by an electromagnetically driven metering valve 19. The metering valve 19 includes a stator having an electromagnetic solenoid 19a, an armature 19b that is attracted to the stator when the electromagnetic solenoid 19a is energized, a valve body 19c that operates together with the armature 19b to open and close the discharge port 15b, And a spring 19d that applies an elastic force to the armature 19b in a direction to close the body 19c. The valve body 19c is biased in a direction to open by receiving the fuel pressure in the pressure chamber 15a.

  Therefore, when the suction force generated between the stator and the armature 19b and the elastic force of the spring 19d are larger than the fuel pressure received by the valve body 19c, the valve body 19c operates toward the valve closing side. On the other hand, when the suction force and the elastic force are smaller than the force of the fuel pressure received by the valve body 19c, the valve body 19c operates to the valve opening side.

  In short, the metering valve 19 has a spring 19d that applies an elastic force to the valve closing side, and is configured to open the valve against the elastic force of the spring 19d by receiving the pressure in the plunger. That is, it is a self-opening valve that automatically opens according to the plunger internal pressure. The electromagnetic actuator including the stator and the armature 19b further biases the metering valve 19 to the valve closing side.

  The low-pressure passage 18 is provided with a suction passage 18a that branches to bypass the discharge port 15b, and the plunger 16 is formed with a suction port 16a that sucks fuel from the suction passage 18a into the pressure chamber 15a. . In addition, a suction valve 20 is assembled to the plunger 16, and the suction port 16 a is opened and closed by the suction valve 20.

  The suction valve 20 includes a valve body 20a that opens and closes the suction port 16a, and a spring 20b that applies an elastic force in a direction to open the valve body 20a. The valve body 20a is biased in a direction to close by receiving the fuel pressure in the pressure chamber 15a. Therefore, when the fuel pressure in the pressure chamber 15a becomes lower than the set value, the valve body 20a is mechanically opened by the elastic force of the spring 20b.

  The cylinder 15 is formed with a discharge port 15c for discharging the fuel in the pressure chamber 15a to the high-pressure passage 41, and the discharge port 15c is opened and closed by a discharge valve 21 (a check valve). The discharge valve 21 is mechanically opened when the pressure in the pressure chamber 15a is higher than the pressure on the downstream side (common rail 42 side) of the discharge valve 21 by a predetermined pressure or more.

  Next, the control contents for the metering valve 19 and the operation of the high-pressure pump 12 will be described.

  First, as shown in FIG. 2 (a), during the period in which the plunger 16 is descending (intake period), the pressure in the pressure chamber 15a (the pressure in the plunger) is the pressure in the low pressure passage 18 (that is, the feed pressure by the low pressure pump 11). ). Therefore, the intake valve 20 is opened, and the discharge valve 21 and the metering valve 19 are closed. Note that energization of the metering valve 19 at this time is turned off. Therefore, the fuel in the low pressure passage 18 flows into the pressure chamber 15a through the suction passage 18a and the suction port 16a, and the high pressure pump 12 sucks the fuel.

  Next, as shown in FIG. 2B, in the initial period (a metering period) in which the plunger 16 is rising, the fuel in the pressure chamber 15a is pressurized by the plunger 16 and gradually increases in pressure. Therefore, although the suction valve 20 is closed, the set pressure of the discharge valve 21 is not reached and the discharge valve 21 is kept closed.

  Further, during such a metering period, a pilot current I1 having a current lower than the valve closing current I2 is allowed to flow to the metering valve 19. The pilot current I1 is set to a low current that does not close the valve body 19c against the pressure in the plunger. Therefore, the valve body 19c is in a valve open state during the metering period. Therefore, a part of the fuel sucked during the suction period is discharged from the discharge port 15b to the low pressure passage 18 during the metering period.

  If the valve opening lift amount of the valve body 19c during the metering period is increased, the fuel discharge is restricted at the discharge port 15b without restricting the fuel discharge at the valve body 19c. That is, the area of the discharge passage in this case is the smallest at the discharge port 15b and has a circular shape. On the other hand, the valve opening lift amount of the valve body 19c in the present embodiment is set to be small enough to restrict the fuel discharge by the valve body 19c. That is, the area of the discharge passage in this case is minimized at the gap portion between the valve body 19c and the discharge port 15b, and has an annular shape.

  Therefore, the fuel pressure (for example, 5 MPa) of the present embodiment in which the fuel is throttled by the valve body 19c is higher than the fuel pressure (for example, several hundred kPa) when the fuel is throttled by the discharge port 15b.

  Next, as shown in FIG. 2 (c), the pumping period after the initial stage during the period in which the plunger 16 is rising will be described. When a valve closing current is supplied to the metering valve 19 during the metering period, the valve body 19c is closed against the plunger pressure, and the fuel discharge from the discharge port 15b is completed. That is, according to the timing at which the valve closing current flows, the amount of fuel discharged by raising the plunger 16 is adjusted, and the amount of fuel remaining in the pressure chamber 15a is adjusted (metered).

  During the pumping period, the metering valve 19 is closed as described above, and the intake valve 20 is also closed. Therefore, the fuel pressure in the pressure chamber 15a rises as the plunger 16 rises, and the discharge valve 21 opens when the fuel pressure reaches the set pressure of the discharge valve 21 (see FIG. 2C). As a result, the high-pressure fuel is pumped from the high-pressure pump 12 to the common rail 42 through the high-pressure passage 41.

  Next, the operation of the high-pressure pump 12 described above will be described in more detail using the time chart shown in FIG. 3 (a) is the lift amount of the plunger 16, FIG. 3 (b) is the value of the solenoid current flowing to the electromagnetic solenoid 19a of the metering valve 19, FIG. 3 (c) is the plunger internal pressure, and FIG. The lift amount of the quantity valve 19 and FIG. 3 (e) show the lift amount of the intake valve 20, respectively.

  The plunger lowering period (lowering stroke) corresponds to t1 to t4 in FIG. 3, and the plunger rising period (upward stroke) corresponds to t4 to t1. The above-described suction period (suction stroke) corresponds to t1 to t4, the metering period (metering stroke) corresponds to t4 to t8, and the pumping period (pumping stroke) corresponds to t8 to t2.

  First, when the plunger 16 starts to descend at time t1, the plunger pressure starts to decrease (see FIG. 3C). Then, the intake valve 20 starts the valve opening operation (see FIG. 3E), and the fuel intake into the pressure chamber 15a is started. Further, the discharge valve 21 is closed at time t2 when the plunger internal pressure is reduced to the valve opening pressure P3 of the discharge valve 21, and the pressure feeding to the high pressure passage 41 is completed. Note that energization of the metering valve 19 is turned off as the plunger 16 starts to descend.

  The plunger internal pressure that has started to decrease with the start of the plunger lowering stroke (intake stroke) decreases to the feed pressure P1 by the low-pressure pump 11, and sucks fuel while maintaining this feed pressure P1 (see FIG. 3C). ).

  Next, the pilot current I1 is allowed to flow through the metering valve 19 at a time t3 that is a predetermined plunger lift amount (crank angle) before the time t4 when the plunger 16 finishes descending and starts to rise (FIG. 3). (See (b)). The pilot current I1 is set to a low current that does not affect the operation of the metering valve 19.

  Next, when the plunger 16 starts to rise at time t4, the plunger internal pressure starts to rise (see FIG. 3C). Then, the intake valve 20 starts the valve closing operation (see FIG. 3E), and the metering valve 19 starts the valve opening operation (see FIG. 3D). At time t5, the valve opening lift amount of the metering valve 19 is maximized and the valve opening operation is completed. The valve opening operation of the metering valve 19 during such a pressure feeding stroke is automatically (mechanically) performed when the valve body 19c receives the pressure in the plunger.

  Next, the valve closing current I2 starts to flow to the metering valve 19 at a time t6 that is a predetermined time (or a predetermined crank angle) before the time t8 when the metering period is desired to end. In the present embodiment, since the duty of the electromagnetic solenoid 19a is controlled, the current flowing through the electromagnetic solenoid 19a pulsates as shown in FIG. 3B, but the duty ratio is set so as to pulsate in a region exceeding the valve closing current I2. It is set.

  Next, with the start of energization of the valve closing current I2, the metering valve 19 starts the valve closing operation at time t7 (see FIG. 3D). The time from the energization start time t6 to the valve closing operation start time t7 is a mechanical response delay time of the valve body 19c.

  In addition, the valve closing operation of the metering valve 19 during such a pressure feeding stroke is performed by the attractive force of the electromagnetic solenoid 19a caused by flowing the valve closing current I2. On the other hand, the valve closing operation of the metering valve 19 during the intake stroke is automatically (mechanically) due to the fact that the pressure in the plunger is lower than the elastic force of the spring 19d.

  With the start of the valve closing operation of the metering valve 19, the fuel pressurization in the pressure chamber 15a is started, and the plunger pressure maintaining the metering pressure P2 starts to increase rapidly. Thereafter, at a time t8 when the response delay time has elapsed from the time t7 when the plunger internal pressure has increased to the valve opening pressure P3 of the discharge valve 21, the discharge valve 21 starts the valve opening operation, and the fuel pressure is sent to the high pressure passage 41. Is started.

  When the plunger internal pressure exceeds the target rail pressure P4, the actual rail pressure is reduced by opening the pressure reducing valve 46 (see FIG. 1). The pressure reducing valve 46 is feedback-controlled by the ECU 44 so that the actual rail pressure detected by the fuel pressure sensor 47 approaches the target rail pressure. Then, as the actual rail pressure approaches the target rail pressure while pulsating due to the operation of the pressure reducing valve 46, the pressure in the plunger approaches the target rail pressure P4 while pulsating (see FIG. 3C).

  Next, the control content of the metering valve 19 by the ECU 44 will be described in more detail with reference to FIGS. 4 and 5. Generally, the metering periods t4 to t8 are calculated by the control of FIG. Based on the calculated metering periods t4 to t8, in the control of FIG. 5, the metering valve 19 is turned off and the pilot current I1 and the valve closing current I2 are switched. Hereinafter, the control of FIGS. 4 and 5 repeatedly executed by the microcomputer of the ECU 44 will be described in detail.

  First, in step S10 in FIG. 4, the rotational speed of the crankshaft of the internal combustion engine (engine rotational speed NE) is acquired. In subsequent step S11, the target value of the pressure in the common rail 42 (target rail pressure Ptrg) is calculated based on the target injection amount Q of the fuel injected from the fuel injection valve 43 and the engine speed NE acquired in step S10. To do. Specifically, the value of the target rail pressure Ptrg is increased as the target injection amount Q and the engine speed NE are increased.

  In the subsequent step S12, the actual rail pressure (actual rail pressure Pact) is acquired based on the detection value of the fuel pressure sensor 47, and in the subsequent step S13, the value of the valve closing current I2 is variably set based on the actual rail pressure Pact. Specifically, the value of the valve closing current I2 is increased as the actual rail pressure Pact is higher. This ensures that the metering valve 19 is closed by the valve closing current against the fuel pressure in the pressure chamber 15a.

  In the subsequent step S14, the values of the metering periods t4 to t8 are variably set based on the deviation between the target rail pressure Ptrg and the actual rail pressure Pact. Specifically, the metering periods t4 to t8 are shortened as the actual rail pressure Pact is lower than the target rail pressure Ptrg. As a result, the amount of fuel discharged from the discharge port 15b at the beginning of the upward stroke of the plunger 16 is reduced, the amount of fuel pumped from the discharge port 15c after the initial stage of the upward stroke is increased, and the actual rail pressure Pact is increased.

  Here, at timing t7 delayed from timing t6 at which the valve closing current I2 starts to flow, the solenoid current flowing through the electromagnetic solenoid 19a rises to the value of the valve closing current I2. Further, at timing t8 that is delayed from timing t7 that has increased to the valve closing current I2, the discharge valve 21 starts the valve opening operation and fuel pumping is started. In consideration of such a shift (response delay) in the fuel pressure feed start timing t8 with respect to the energization start timing t6 of the valve closing current I2, in the subsequent step S15, the discharge valve 21 is moved in the metering period t4 to t8 calculated in step S14. The metering control periods t4 to t6 are calculated so that the valve opening operation is started.

  That is, the metering period t4 to t8 is a period from the timing t4 at which the plunger 16 starts to rise to the timing t8 at which the pressure feeding is started, and the metering control period t4 to t6 is closed from the timing t4. This is a period until timing t6 when the valve current I2 starts to flow. In step S15, when calculating the metering control period t4 to t6 based on the metering period t4 to t8 (that is, calculating the timing t6 at which the valve closing current I2 starts to flow), the actual rail pressure Pact, the engine speed NE, etc. It may be variably set according to.

  Next, in step S20 in FIG. 5, it is determined whether or not the timing t3 is a predetermined time (or a predetermined crank angle) before the timing t4 at which the plunger 16 starts lift-up. In addition to the processing in FIG. 5, a crank angle signal representing a change in the rotation angle of the crankshaft is acquired every predetermined time. Thereby, the lift position and moving direction of the plunger 16 at the present time can be acquired, and it is possible to determine whether or not the predetermined timing t3.

  If it is determined that it is not the predetermined timing t3 (S20: NO), the energization to the metering valve 19 is turned off in step S25. If it is determined that the timing t3 is reached (S20: YES), the pilot current I1 is supplied to the metering valve 19 in the subsequent step S21. In the subsequent step S22, it is determined whether or not the metering control period t4 to t6 calculated in step S15 of FIG. 4 has elapsed. If not, the pilot current I1 is continuously energized (S22: NO, S21). If it has elapsed, energization of the metering valve 19 with the valve closing current I2 is started (S22: YES, S23).

  That is, energization of the pilot current I1 is continued until the metering control period t4 to t6 elapses. When the metering control period t4 to t6 elapses, the energization to the metering valve 19 is changed from the pilot current I1 to the valve closing current. Switch to I2. Therefore, immediately before the valve closing current I2 flows, the pilot current I1 flows through the electromagnetic solenoid 19a, and the valve closing current I2 flows from the state where the pilot current I1 flows through the electromagnetic solenoid 19a.

  After that, in step S24, it is determined whether or not the timing t1 at which the plunger 16 starts to descend has been reached. If it has not reached the descent start timing t1, energization of the valve closing current I2 is continued (S24: NO, S23). If it has reached, the energization of the valve closing current I2 to the metering valve 19 is terminated and the energization is turned off (S24: YES, S25). In other words. The energization of the valve closing current I2 is continued until the descent start timing t1 is reached.

  Incidentally, when the discharge amount of the high-pressure pump 12 is made zero, the metering period t4 to t8 may be maximized. In other words, the pilot current I1 and the valve closing current I2 are not supplied to the metering valve 19, and the metering valve 19 is not closed during the plunger ascending stroke. As a result, all of the fuel sucked in the downward stroke is discharged from the discharge port 15b during the upward stroke. Hereinafter, the operation of the high-pressure pump 12 when the discharge amount is zero will be described with reference to FIG.

  6 is a time chart showing the operation of the high-pressure pump 12, FIG. 6 (a) is the lift amount of the plunger 16, FIG. 6 (b) is the value of the solenoid current flowing to the electromagnetic solenoid 19 a of the metering valve 19, 6 (c) shows the pressure in the plunger, FIG. 6 (d) shows the lift amount of the metering valve 19, and FIG. 6 (e) shows the lift amount of the intake valve 20, respectively.

  As shown in FIG. 6A, the solenoid current remains zero in any of the downward strokes t1 to t4 and the upward strokes t4 to t1 (see FIG. 6B). Therefore, when the plunger 16 starts to rise at time t4, the metering valve 19 is opened by receiving the pressure in the plunger (see FIG. 6D), and the suction valve 20 is closed (FIG. 6 ( e)). Thereafter, when the plunger 16 starts to descend at time t1, the metering valve 19 is closed by the elastic force of the spring 19d (see FIG. 6D), and the suction valve 20 is opened (FIG. 6 (FIG. 6). e)). Note that the discharge valve 21 remains in the closed state.

  Thus, at the initial stage of the ascending stroke when the discharge amount is made zero, the metering valve 19 is opened without the pilot current I1 flowing. The lift amount of the metering valve 19 at this time is larger than the lift amount of the metering valve 19 which is opened with the pilot current I1 flowing as shown in FIG.

  As described above, according to the present embodiment, the valve closing current I2 is allowed to flow while the pilot current I1 is flowing by causing the pilot current I1 to flow immediately before flowing the valve closing current I2. Therefore, the rise of the electromagnetic force generation of the electromagnetic solenoid 19a can be accelerated compared to the case where the valve closing current I2 is supplied when the current supplied to the metering valve 19 is zero. That is, the time (rise time) from the energization start timing t6 of the valve closing current I2 to the timing t7 when the solenoid current reaches the value of the valve closing current I2 can be shortened. Therefore, the valve closing response of the metering valve 19 can be improved without increasing the electromagnetic force generation capability by increasing the size of the electromagnetic solenoid 19a and the like. In other words, the solenoid solenoid 19a and the like can be downsized while ensuring the valve closing response of the metering valve 19, and the metering valve 19 can be downsized.

  Further, by causing the pilot current I1 to flow immediately before flowing the valve closing current I2, the air gap CL (see FIG. 2B) provided between the stator having the electromagnetic solenoid 19a and the armature 19b by the pilot current I1. ) Is reduced, the armature 19b is driven during the metering period. In other words, when the discharge amount is set to zero, the lift amount of the metering valve 19 can be increased by opening the valve with the pilot current I1 compared to the lift amount of the metering valve 19 that opens without flowing the pilot current I1. The air gap CL is made small by making it small. Thereby, the following effects are exhibited.

  That is, since the valve closing current I2 is allowed to flow while the air gap CL is small due to the pilot current I1, the size of the electromagnetic solenoid 19a and the like can be increased without increasing the electromagnetic force generation capability. Valve responsiveness can be improved. Further, since the valve closing operation is performed from the state in which the armature 19b is driven so as to reduce the air gap CL, the operation stroke of the metering valve 19 required for the valve closing can be shortened. Therefore, the valve closing response of the metering valve 19 can be improved without increasing the electromagnetic force generation capability by increasing the size of the electromagnetic solenoid 19a and the like.

  Here, contrary to the present embodiment, when the intake valve 20 is abolished and the metering valve 19 is opened during the descending period to suck the fuel from the discharge port 15b, a sufficient amount of fuel can be sucked. Therefore, it is necessary to increase the maximum stroke amount of the metering valve 19. Then, securing the stroke amount becomes a restriction for downsizing the metering valve 19. On the other hand, according to the present embodiment, since the suction port 16a is opened by the suction valve 20 different from the metering valve 19 for suction, the maximum stroke amount of the metering valve 19 can be set small. Therefore, the metering valve 19 can be downsized.

  Further, according to the present embodiment, the metering valve 19 has the spring 19d that gives an elastic force to the valve closing side, and is configured to open the valve against the elastic force of the spring 19d by receiving the pressure in the plunger. Has been. That is, it is a self-opening valve that automatically opens according to the plunger internal pressure. Therefore, when the internal combustion engine is stopped while the plunger 16 is moving up and the rotation of the crankshaft is stopped, the amount of current supplied to the metering valve 19 is zero, but the metering valve 19 is controlled by the spring 19d. Since the valve is closed, the pressurized state in the pressure chamber is maintained to some extent. Therefore, when the internal combustion engine is started next time, the fuel can be pressurized and fed immediately.

  Here, in the case of metering as shown in FIG. 3, the discharge port 15 b is set so that the plunger internal pressure becomes lower than the valve opening pressure P <b> 3 of the discharge valve 21 by the valve opening operation of the metering valve 19 in the metering period t <b> 4 to t <b> 8. The fuel has escaped from. And the valve opening lift amount of the metering valve 19 in the metering period at the time of zero discharge shown in FIG. 6 (that is, the rising period t4 to t1) is larger than the lift amount when the pilot current I1 is flowing. Therefore, with respect to the pressure difference between the plunger internal pressure and the low pressure passage 18 during the metering period (that is, the differential pressure across the metering valve 19), the differential pressure before and after metering (for example, 5 MPa) is the differential pressure before and after discharge (zero). For example, it is larger than 400 kPa).

  Since the discharge flow rate from the discharge port 15b is proportional to the square root of the front-rear differential pressure, according to the present embodiment in which the front-rear differential pressure at the time of metering is increased as described above, the discharge port 15b of the metering valve 19 A sufficient discharge flow rate can be secured while reducing the opening area. That is, a sufficient discharge flow rate can be secured while reducing the lift amount. Therefore, the metering valve 19 can be downsized.

(Second Embodiment)
In the first embodiment, the plunger 16 is formed with the suction port 16 a that is opened and closed by the suction valve 20. In contrast, in the present embodiment shown in FIG. 7, a suction port 16 a that is opened and closed by the suction valve 20 is formed in the cylinder 15. About the other point, the fuel pump concerning this embodiment is the same structure as the fuel pump 10 concerning 1st Embodiment. The control content for the metering valve 19 is the same.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows.

  That is, in each of the above-described embodiments, the fuel in the low pressure passage 18 is sucked from the suction port 16a into the pressure chamber 15a by opening the suction valve 20 during the downward period of the plunger 16. In contrast, the suction valve 20 is abolished, the suction port 16a opened and closed by the suction valve 20 is abolished, and the metering valve 19 is opened during the descending period of the plunger 16, so that the pressure chamber 15a is opened from the discharge port 15b. Alternatively, the fuel in the low pressure passage 18 may be sucked.

  The metering valve 19 in this case is urged in such a direction that the valve body 19c closes in response to the fuel pressure in the pressure chamber 15a. Accordingly, during the descending period, the metering valve 19 is automatically opened by the negative pressure of the pressure chamber 15a, and during the metering period, a current is supplied to the electromagnetic solenoid 19a of the metering valve 19 to increase the pressure in the plunger. The metering valve 19 is opened against this. During the pressurization and pressure feeding period, the metering valve 19 is automatically closed by the pressure in the plunger.

  In the first embodiment, the value of the pilot current I1 is set so as to drive the armature 19b to reduce the air gap CL. On the other hand, a slight current that does not drive the armature 19b may flow as the pilot current I1. Even in this case, the generation of the electromagnetic force of the electromagnetic solenoid 19a can be accelerated earlier than in the case where the valve closing current I2 is supplied when the current supplied to the metering valve 19 is zero.

DESCRIPTION OF SYMBOLS 15 ... Cylinder, 15a ... Pressure chamber, 15b ... Discharge port, 16 ... Plunger, 16a ... Suction port, 18 ... Low pressure passage, 19 ... Metering valve, 19a ... Electromagnetic solenoid, 19b ... Armature, 19d ... Spring, 41 ... High pressure A passage, t1 to t4 ... a descending period of the plunger, t4 to t8 ... a metering period, CL ... an air gap.

Claims (2)

A cylinder forming a pressure chamber inside,
A plunger that descends in the cylinder and sucks fuel from the low pressure passage into the pressure chamber, and rises in the cylinder to pressurize the fuel in the pressure chamber and discharge it to the high pressure passage;
An electromagnetically driven metering valve that opens and closes a discharge port for discharging the fuel in the pressure chamber to the low pressure passage;
The fuel is discharged from the discharge port during a predetermined metering period from the start of raising the plunger, the fuel in the pressure chamber is metered, and a valve closing current is supplied to the metering valve to close the metering valve. In the fuel pumping system that is operated to end the metering period and start pressurizing fuel in the pressure chamber,
A suction port for sucking fuel from the low-pressure passage into the pressure chamber;
Opening and closing the suction port by a suction valve different from the metering valve;
During the descending period of the plunger, the fuel is sucked from the suction port,
Wherein prior to passing the closing current and the flow of pilot current of low current than the closing current to the metering valve,
The metering valve has a spring for applying an elastic force on the valve closing side, and is configured to open the valve against the elastic force in response to the fuel pressure in the pressure chamber. Fuel pumping system. The metering valve is configured to have a valve body for opening and closing the stator, armature, and said discharge port working together with the armature having an electromagnetic solenoid,
The armature is driven during the metering period so that an air gap provided between the stator and the armature is made smaller by the pilot current than when the pilot current is not passed. The fuel pumping system according to claim 1.

Images