JP2008202417A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably maintain a valve element lift amount at a first lift amount in a fuel injection control device in which the rising speed of a needle valve is changed in two steps by changing the valve element lift amount of a control valve for controlling the rear surface pressure of the needle valve from the first lift amount to a second lift amount (> first lift amount). <P>SOLUTION: When the drive force of an actuator 43b reaches a first drive force, the lift amount of a valve element 43a is changed to the first lift amount, and the valve element 43a starts to come into contact with a piston 43c at the initial position. When the drive force is equal to or less than a second drive force (> first drive force), the piston 43c is not allowed to move from the initial position by the pressing of the valve element 43a, and the valve element lift amount is maintained at the first lift amount. When the drive force is above a third drive force (> second drive force), the piston 43c is moved to a first position by the pressing of the valve element 43c, and the valve element lift amount is changed to the second lift amount. A flow passage allowing a fuel to flow from a fuel supply passage C1 into a control chamber R2 is opened when the piston 43c is at the initial position, and cut off when it is at the first position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

Conventionally, as shown in FIG. 9, a needle valve 120 that opens and closes an injection hole 110 for injecting fuel into a combustion chamber of an internal combustion engine (particularly a diesel engine), and an injection valve Pc that is the pressure of the internal fuel One end side (lower end side in FIG. 9) of 120 receives a force in the valve opening direction (upward direction in FIG. 9), and the fuel inside is injected from the nozzle hole 110 toward the combustion chamber when the needle valve 120 is open. And a control chamber 140 in which the other end side (upper end side in FIG. 9) of the needle valve 120 receives a force in the valve closing direction (downward direction in FIG. 9) by the control pressure Pcntl which is the pressure of the internal fuel. , A fuel supply path 150 for supplying high-pressure fuel generated by a high-pressure generator (not shown) + a common rail to the nozzle chamber 130, and a flow for flowing the fuel from the fuel supply path 150 into the control chamber 140 A fuel inflow path 170 in which an inlet orifice 160 is interposed, a fuel discharge path 190 in which a discharge orifice 180 for discharging fuel from the control chamber 140 to a fuel tank (not shown) is interposed, and a fuel discharge path 190. 2. Description of the Related Art There is known a fuel injection control device that includes a control valve 210 that is mounted and communicates and blocks a fuel discharge path 190 (see, for example, Patent Document 1).
JP 2005-320870 A

  In this device, when the needle valve 120 that is in the closed state is opened (when the needle valve 120 is changed from the closed state (lift amount = 0) to the opened state (lift amount> 0)), the control valve 210 is opened. (Changed from the closed state to the open state). As a result, the fuel is discharged from the control chamber 140 through the fuel discharge passage 190 and the control pressure Pcntl is reduced from the injection pressure Pc, and accordingly, the fuel flows from the fuel supply passage 150 into the control chamber 140 through the fuel inflow passage 170. . As a result, the control pressure Pcntl decreases from the injection pressure Pc at a speed corresponding to the difference (= Qout−Qin) between the outflow flow rate Qout of the fuel passing through the discharge orifice 180 and the inflow flow rate Qin of the fuel passing through the inflow orifice 160. To go.

  When the control pressure Pcntl decreasing in this way reaches the “needle valve opening pressure” (the control pressure Pcntl when the needle valve 120 shifts from the closed state to the open state), the needle valve 120 opens. (Move upward in FIG. 9), and as a result, fuel injection is started. Thereafter, the needle valve 120 rises at a speed corresponding to the rate of decrease in the volume of the fuel in the control chamber 140 (that is, the difference between the outflow rate Qout and the inflow rate Qin (= Qout−Qin)) (FIG. 9 and move upward). That is, the lift amount of the needle valve 120 increases. During this time, fuel injection is continued. Hereinafter, the rising speed (the increasing speed of the lift amount) of the needle valve 120 when the needle valve 120 is lifted in this way is referred to as “needle valve rising speed”.

  On the other hand, when the needle valve 120 that is rising (in the open state) is closed (when the needle valve 120 is changed from the open state to the closed state), the control valve 210 is closed (opened). State is changed to a closed state). Thereby, the fuel discharge from the control chamber 140 through the fuel discharge passage 190 is stopped, while the fuel inflow into the control chamber 140 through the fuel inflow passage 170 is continued. As a result, the needle valve 120 descends at a speed corresponding to the fuel volume increase speed in the control chamber 140 (ie, the inflow flow rate Qin) (moves downward in FIG. 9). That is, the lift amount of the needle valve 120 decreases. Hereinafter, the descending speed of the needle valve 120 when the needle valve 120 descends (the rate of decrease in the lift amount) is referred to as “needle valve descending speed”. When the lift amount of the needle valve 120 reaches “0”, the needle valve 120 is closed and fuel injection is terminated. In this way, by controlling the control valve 210 and controlling the control pressure Pcntl, the position (lift amount) of the needle valve 120 is adjusted, and fuel injection control is performed.

  By the way, there is a demand for enabling the needle valve ascending speed to be switched between two stages. One reason for this is as follows. That is, in the diesel engine, most of the fuel injected within the period from the start of fuel injection to the start of ignition (so-called ignition delay time) is replaced by so-called diffusion combustion (diesel combustion), so-called premixed combustion (combustion chamber). In this case, there is a tendency to perform combustion that ignites substantially simultaneously in a relatively uniformly diffused state. In this premixed combustion, since the fuel is ignited substantially simultaneously, there is a problem that the pressure in the combustion chamber rises rapidly and noise increases. In order to reduce this noise, the total amount of fuel injected during the ignition delay time may be reduced. For this purpose, the injection rate (fuel injection amount injected per unit time) may be set to be small only for an extremely short period after the start of fuel injection. Here, the injection rate increases as the needle valve lift amount increases after the start of fuel injection. From the above, when the needle valve ascent rate (and hence the needle valve lift amount) is set to a small value for a very short period after the start of fuel injection, and then the needle valve ascent rate is switched to a larger value (ie, the needle valve ascent rate is reduced). When switching from “small” to “large” in two stages, the noise associated with the premixed combustion can be reduced.

  As described above, the needle valve ascending speed is based on the flow rate difference (= Qout−Qin). Therefore, in order to switch the needle valve ascent speed from “small” to “large” in two stages, for example, the inflow flow rate Qin may be reduced at a predetermined time during the needle valve ascent. For this purpose, for example, the control valve 210 in the apparatus shown in FIG. 9 may be configured as shown in FIG. 10, the same or equivalent members as those shown in FIG. 9 are denoted by the same reference numerals as those in FIG.

  That is, in the control valve 210 shown in FIG. 10, the valve element 212 is movably accommodated in the valve element accommodating chamber 211 (internal pressure = control pressure Pcntl) communicating with the control chamber 140 via the flow path 220. ing. The valve body 212 is driven in the valve opening direction (downward in FIG. 10) by the driving force of the actuator 213 (in FIG. 10, a piezo element (piezoelectric / electrostrictive element)), and the valve body in the valve body housing chamber 211 is driven. The position 212 (valve lift amount) is adjusted according to the driving force of the actuator 213.

  10, the flow path 220, the valve body accommodating chamber 211, the return chamber 214, and the flow path 230 correspond to the fuel discharge path 190 in FIG. 9, and the flow path 240, the valve body accommodating chamber 211, and the flow path 220 are as shown in FIG. This corresponds to the fuel inflow passage 170 in FIG.

  The driving force of the actuator 213 is zero or small, and the valve body 212 is in the position shown in FIG. 10, that is, the position where the valve body 212 contacts the valve seat portion 211a of the valve body storage chamber 211 and does not contact the valve seat portion 211b. When the valve body lift amount is 0, the valve body storage chamber 211 and the return chamber 214 (and hence the flow path 230) are shut off, and the valve body storage chamber 211 and the flow path 240 (and thus the fuel supply path 150). ). In this case, the control valve 210 is closed (the fuel discharge path 190 is shut off), and the fuel inflow path 170 is opened (that is, the same state as shown in FIG. 9).

  The driving force of the actuator 213 increases from the state shown in FIG. 10 to the first driving force, so that the valve body 212 is located at the position shown in FIG. 11, that is, the valve body 212 is also in the valve seat portion 211a of the valve body housing chamber 211. When moved to a position that does not contact the valve seat portion 211b (valve element lift amount = first lift amount), the valve element storage chamber 211 and the return chamber 214 communicate with each other. In this case, the control valve 210 is opened (the fuel discharge passage 190 is opened), and the fuel inflow passage 170 is maintained in the opened state. Therefore, when the state shown in FIG. 10 is changed to the state shown in FIG. 11, the control chamber pressure Pcntl decreases at a speed corresponding to the flow rate difference (= Qout−Qin), and the control chamber pressure Pcntl decreases the needle valve opening pressure. If it falls below, the needle valve 120 opens. Thereafter, the needle valve 120 rises at a needle valve ascent speed (= first ascent speed) corresponding to the flow rate difference (= Qout−Qin).

  The driving force of the actuator 213 further increases from the state shown in FIG. 11 to the second driving force (> first driving force), and the valve body 212 is in the position shown in FIG. When moving to a position where the valve seat 211b comes into contact (valve lift amount = second lift amount), the valve body accommodating chamber 211 and the passage 240 are blocked. That is, the fuel inflow path 170 is blocked and the inflow flow rate Qin = 0. Accordingly, thereafter, the needle valve 120 rises at a needle valve ascent rate (= second ascent rate> first ascent rate) corresponding to only the outflow rate Qout.

  In this way, the needle valve 120 is opened by setting the driving force of the actuator 213 to the first driving force and adjusting the valve body lift amount to the first lift amount. By further increasing the force from the first driving force to the second driving force and switching the valve body lift amount from the first lift amount to the second lift amount, the needle valve ascent speed is changed from “small” to “large”. It can be switched to two stages.

  By the way, in the configuration of the control valve 210 shown in FIG. 10, variation may occur in the relationship between the power (voltage) supplied to the actuator 213 and the driving force of the actuator 213 due to variations among the individual actuators 213. . Even when the driving force of the actuator 213 is constant, the position of the valve body 212 (valve body lift amount) in the open state can be changed due to a change in the viscosity of the fuel due to a temperature change.

  Therefore, the valve body lift amount is stably maintained at the first lift amount as shown in FIG. 11 by adjusting the electric power (and hence the driving force) supplied to the actuator (that is, the valve body 212 is accommodated in the valve body). In practice, it is very difficult to stably maintain a state where neither the valve seat portion 211a nor the valve seat portion 211b of the chamber 211 abuts. If the valve lift is not stably maintained at the first lift, the inflow flow rate Qin and the outflow flow rate Qout change, and the needle valve ascent speed becomes unstable. Therefore, the arrival of a fuel injection control device that can stably maintain the valve lift amount at the first lift amount is desired.

  An object of the present invention is to provide a valve body in a fuel injection control device capable of switching the needle valve ascent speed in two stages by changing the valve body lift amount of the valve body of the control valve from the first lift amount to the second lift amount. An object of the present invention is to provide a fuel injection control device capable of stably maintaining a lift amount at a first lift amount.

  The fuel injection control device according to the present invention has the same basic configuration as the device shown in FIG. 9 described above. In the fuel injection control device according to the present invention, the control valve includes a valve body that communicates and blocks the fuel discharge passage, and an actuator that generates a driving force that presses the valve body in a valve opening direction. The opening and closing of the valve body is controlled by adjusting the force, and the lift amount (valve body lift amount) in the valve opening direction from the closed state of the valve body in the valve open state according to the increase of the driving force is adjusted. When the lift amount of the valve body and the valve body lift amount is less than the first lift amount greater than zero, the valve body lift amount is maintained in its initial position without contacting the valve body, and the valve body lift amount is maintained at the first lift amount. When the amount reaches, the contact with the valve body starts at the initial position, and when the valve body lift amount increases from the first lift amount, the valve body is pressed to open the valve body from the initial position. And a piston moving in the valve direction.

  When the driving force of the actuator reaches the first driving force, the valve body lift amount is configured to reach the first lift amount, and the piston has a first driving force that is greater than the first driving force. When the driving force is 2 or less, the valve body cannot be moved from the initial position by pressing the valve body, and the valve body is opened from the initial position by pressing the valve body in accordance with the increase of the driving force from the second driving force. Arranged and configured to move in the valve direction. The minimum flow area of the fuel inflow passage is smaller when the piston is in the first position on the valve opening direction side of the valve body than the initial position than when the piston is in the initial position. The fuel inflow path is configured as described above.

  According to the said structure, when a valve body lift amount is more than 1st lift amount, a valve body contacts a piston and the motion of a valve body is suppressed by a piston. When the valve body lift amount is the first lift amount, the piston is in the initial position, and the valve body lift amount is a certain value larger than the first lift amount (hereinafter referred to as “second lift amount”). When it reaches, the piston moves to the first position on the valve opening direction side of the valve body from the initial position. In addition, the minimum flow area of the fuel inflow passage (and thus the inflow flow rate Qin) is smaller when the piston is in the first position than when the piston is in the initial position. Therefore, by changing the valve body lift amount from the first lift amount to the second lift amount, the needle valve ascent speed can be switched in two stages from “small” to “large”.

  Further, since the piston cannot move from the initial position due to the pressure of the valve body when the driving force of the actuator is less than or equal to the second driving force, the valve body does not move when the driving force of the actuator is between the first driving force and the second driving force. The lift amount is maintained at the first lift amount. Accordingly, the power (voltage) supplied to the actuator is set to a value corresponding to the case where the driving force of the actuator becomes a first predetermined value (for example, a median value) between the first driving force and the second driving force. If adjusted, the valve lift can be stably maintained at the first lift even when the above-described "variation among actuators", "change in fuel viscosity due to temperature change", and the like occur. .

  In this case, the piston reaches the first position when the driving force of the actuator reaches a third driving force that is larger than the second driving force, and when the driving force of the actuator is larger than the third driving force. It is preferable to be arranged and configured to be maintained in the first position.

  According to this, if the electric power (voltage) supplied to the actuator is adjusted to a value corresponding to the case where the driving force of the actuator becomes a second predetermined value larger than the third driving force, the valve body lift amount is The value corresponding to the case where the piston is in the first position (that is, the second lift amount) can be stably maintained.

  Therefore, when fuel injection is performed in such a configuration, the driving force of the actuator is first adjusted to the first predetermined value, and then adjusted to the second predetermined value, thereby reducing the needle valve ascent speed. It is possible to switch from "" to "large" in two steps in a stable and reliable manner.

  In the fuel injection control device according to the present invention, specifically, for example, the control valve includes a valve body housing chamber communicating with the control chamber and a pressure chamber communicating with the fuel supply path. The fuel discharge path is shut off in the closed state in which the valve body is movably accommodated in the valve body accommodating chamber, and the valve body is in contact with a valve seat provided in the valve body accommodating chamber. The fuel discharge passage is configured to communicate with the valve body in the open state in which the valve body is separated from the valve seat portion, and one end side of the piston faces the valve seat portion in the valve body housing chamber. The valve body may face the valve body from the side, the other end of the piston faces the pressure chamber, and the valve body may be in contact with one end of the piston. In this case, the 1st communicating path which connects the said control chamber and the said valve body storage chamber, and the said valve body storage chamber respond | correspond to a part of said fuel discharge path.

  In this case, it is preferable that an elastic member that constantly urges the piston toward the valve body side (the valve closing direction of the valve body) in the pressure chamber is provided. The elastic member is a spring, and it is more preferable that the spring is in a close contact state when the piston is in the first position. Thereby, when the driving force of the actuator is larger than the third driving force, a configuration for maintaining the piston in the first position can be easily achieved. In this case, a stopper mechanism that prohibits movement of the piston from the initial position to the valve body side (the valve closing direction of the valve body) is provided, and the actuator is driven by the cooperation of the stopper mechanism and the biasing force of the elastic member. The piston is configured to be maintained at the initial position when the force is equal to or less than the second driving force.

  As described above, when the valve body is configured to be in contact with one end side of the piston, the piston has an internal space communicating with the pressure chamber and an outer surface (on the side surface) on one end side of the piston. And when the piston is in the initial position, the outer surface side of the orifice communicates with the valve body housing chamber, and when the piston is in the first position, It is preferable that the outer surface side is configured to be blocked from the valve body storage chamber. Specifically, when the piston is in the first position, the opening on the outer surface side of the orifice is blocked by the sliding surface with the piston on the body side that houses the piston. In this case, the second communication path that connects the pressure chamber and the fuel supply path, the pressure chamber, the internal space, the orifice, the valve body storage chamber, and the first communication path correspond to the fuel inflow path. To do.

  According to this, when the piston is in the initial position, the fuel supply passage is opened and the flow passage area of the orifice provided in the piston itself is the minimum flow passage area of the fuel inflow passage, while the piston is in the first position. In some cases, the fuel inflow path is blocked (ie, the minimum flow area of the fuel inflow path is zero). Therefore, the fuel inflow path can be configured with a simple configuration so that the minimum flow path area of the fuel inflow path is smaller when the piston is in the first position than when the piston is in the initial position. it can.

  In this case, there may be provided a second fuel inflow passage having a second orifice through which fuel flows from the fuel supply passage into the valve body housing chamber. By providing the second fuel inflow path, the minimum flow area of the entire fuel inflow path is such that when the piston is in the initial position, the flow area of the orifice provided in the piston itself and the flow path of the second orifice When the piston is in the first position, the flow area of the second orifice is obtained. That is, when the second fuel inflow passage is not provided, the change rate of the minimum flow passage area as the entire fuel inflow passage can be changed. In other words, it is possible to change the change rate of the needle valve ascending speed that changes in two stages.

  In addition, as described above, when the valve body is configured to be in contact with one end side of the piston, the piston has an internal space communicating with the pressure chamber and an outer surface on one end side of the piston. An orifice is provided, the outer surface side of the orifice communicates with the valve body accommodating chamber (always), and the internal space at the other end of the piston faces the pressure chamber. The portion is provided with a tapered surface that expands from one end side to the other end side of the piston, and a protruding portion that protrudes toward the tapered surface is fixedly disposed in the pressure chamber. When the taper surface is in the initial position, the tapered surface is spaced apart from the protrusion to communicate the internal space and the pressure chamber, and when the piston is in the first position, the taper surface is the protrusion. May be configured to block said pressure chamber and said internal space in contact. In this case, the second communication path that connects the pressure chamber and the fuel supply path, the pressure chamber, the internal space, the orifice, the valve body storage chamber, and the first communication path correspond to the fuel inflow path. To do.

  This also allows the fuel inflow passage to be opened when the piston is in the initial position, the flow area of the orifice provided in the piston itself to be the minimum flow area of the fuel inflow passage, and when the piston is in the first position. The fuel inflow path may be blocked (that is, the minimum flow path area of the fuel inflow path becomes zero).

  In addition, the fuel inflow path is reliably blocked by the “contact between the tapered surface and the protruding portion”. Therefore, compared with the case where the fuel inflow path is blocked by the above-described “opening on the outer surface side of the orifice being blocked by the sliding surface with the piston on the body side”, the blocking state of the fuel inflow path is more It can be maintained more reliably.

  By the way, as described above, when one end of the piston is configured to receive the pressure of the valve body housing chamber (and therefore, the control pressure) and the other end of the piston is configured to receive the pressure of the pressure chamber (and thus the injection pressure), When the control pressure decreases from the injection pressure with the control valve open, the force in the valve closing direction of the valve element acting on the piston based on this differential pressure increases. Therefore, it is necessary to increase the size of the actuator in order to secure a sufficient driving force of the actuator against the force (load) based on the differential pressure.

  In order to cope with this problem, the other end side of the piston is formed so as to communicate with the valve body accommodating chamber via a third communication passage penetrating inward along the axial direction instead of the pressure chamber. An elastic member that constantly urges the piston toward the valve body in the back chamber is provided, and the pressure chamber is provided on the outer periphery of the intermediate portion in the axial direction of the piston. When the piston is in the initial position, the valve body storage chamber and the pressure chamber communicate with each other when the piston is in the initial position. Is configured to shut off the valve body housing chamber and the pressure chamber when the fuel is in the first position, and an orifice is formed in the second communication passage that connects the pressure chamber and the fuel supply passage. Is preferred. In this case, the first communication passage that communicates the control chamber and the valve body storage chamber, and the valve body storage chamber corresponds to a part of the fuel discharge passage, the second communication passage, the pressure chamber, The valve body storage chamber and the first communication passage correspond to the fuel inflow passage.

  Also in this case, when the piston is in the initial position, the fuel inflow passage is opened, the flow passage area of the orifice provided in the second communication passage becomes the minimum flow passage area of the fuel inflow passage, and the piston is in the first position. In some cases, the fuel inflow path may be blocked (that is, the minimum flow area of the fuel inflow path becomes zero).

  In addition, both ends of the piston receive the same pressure (specifically, control pressure). Therefore, even if the control pressure is reduced from the injection pressure in the open state of the control valve, the above-mentioned “force in the valve closing direction of the valve element acting on the piston based on the differential pressure” does not occur. Therefore, the increase in size of the actuator described above can be avoided.

  Embodiments of an internal combustion engine fuel injection control apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall schematic configuration of a fuel injection control device 10 for an internal combustion engine (diesel engine) according to an embodiment of the present invention. The fuel injection control device 10 includes a fuel pump 20 that sucks and discharges fuel stored in a fuel tank T, a common rail 30 to which high-pressure fuel discharged by the fuel pump 20 is supplied, and a fuel supply path from the common rail 30. An injector 40 that is supplied with high-pressure fuel through C1 and injects fuel into a combustion chamber (not shown) of the internal combustion engine, and an ECU 50 that controls the fuel pump 20 and the injector 40 are provided. The fuel pump 20 and the common rail 30 correspond to the “high pressure generator”.

  In FIG. 1, one injector 40 is described in which high-pressure fuel is supplied from the common rail 30 through one fuel supply path C1, but in reality, the injector 40 and the fuel supply path C1 include a plurality of internal combustion engines. The injectors 40 are individually connected to the common rail 30 through the corresponding fuel supply passages C1. The pressure of the fuel in the fuel supply path C1 (hereinafter referred to as “injection pressure Pc”) is substantially equal to the pressure of the fuel in the common rail 30 (= pressure of the high-pressure fuel). Hereinafter, for convenience of explanation, the upper and lower sides on the drawing in each drawing may be simply referred to as “upper” and “lower”.

  The fuel pump 20 is configured to be able to adjust the fuel intake flow rate according to an instruction from the ECU 50. As a result, the fuel discharge pressure (and hence the injection pressure Pc) can be adjusted.

  The injector 40 mainly includes a body 41, a stepped columnar needle valve 42 slidably accommodated in the first predetermined space inside the body 41, and a second predetermined space inside the body 41. And a control valve 43 disposed on the surface.

  The needle valve 42 divides the first predetermined space into a nozzle chamber R1 and a control chamber R2. The nozzle chamber R1 communicates with the fuel supply path C1, and the fuel pressure in the nozzle chamber R1 is equal to the injection pressure Pc. The nozzle chamber R1 also communicates with a plurality of nozzle holes 41a provided at the lower end of the body 41 and facing the combustion chamber.

  A tapered portion (conical shape portion) 42a whose diameter is reduced toward the distal end is coaxially formed at the distal end portion on the lower end side of the needle valve 42. In a state where the needle valve 42 is lowered in the first predetermined space and the tapered portion 42a is in contact with the circular valve seat portion 41b of the body 41 formed in the vicinity of the injection hole 41a (the state shown in FIG. 1). The nozzle hole 41a is cut off from the nozzle chamber R1. In this state, fuel is not injected.

  Hereinafter, this state is also referred to as a closed state of the needle valve 42. Further, the lift amount of the needle valve 42 (needle valve lift amount Ln) means the upward movement amount (rise amount) of the needle valve 42 from this state. That is, when the needle valve 42 shown in FIG. 1 is closed, the needle valve lift amount Ln is “0”.

  On the other hand, when the needle valve 42 moves (rises) upward from the closed state and the tapered portion 42a is separated from the circular valve seat portion 41b, the nozzle hole 41a communicates with the nozzle chamber R1. In this state (ie, the needle valve lift amount Ln> 0), the fuel is injected with the injection pressure Pc. Hereinafter, this state is also referred to as a valve open state of the needle valve 42. In the following, the transition from the open state to the closed state is referred to as “valve closing”, and the transition from the closed state to the open state is referred to as “valve opening”.

The lower end side of the needle valve 42 receives force F1 in the valve opening direction (upward) due to the pressure in the nozzle chamber R1 (= injection pressure Pc). Here, when the outer diameter of the sliding portion 42b that partitions the nozzle chamber R1 and the control chamber R2 in the needle valve 42 is D1, and the valve seat diameter (seat diameter) of the circular valve seat portion 41b is D2, the needle valve 42 In the closed state, the pressure receiving area on the lower end side of the needle valve 42 with respect to the force F1 in the valve opening direction is (π / 4) · (D1 ² −D2 ² ). Therefore, when the needle valve 42 is closed, the force F1 in the valve opening direction can be expressed by the following equation (1).

F1 = (π / 4) ・ (D1 ² −D2 ² ) ・ Pc (1)

When the needle valve 42 is opened, a portion of the tapered portion 42a on the tip side of the portion that contacts the circular valve seat portion 41b is exposed to the fuel having the injection pressure Pc. Accordingly, in the open state of the needle valve 42, the pressure receiving area on the lower end side of the needle valve 42 with respect to the force F1 in the valve opening direction is increased by (π / 4) · D2 ² and (π / 4) · D1 ² It becomes. Therefore, when the needle valve 42 is in the open state, the force F1 in the valve opening direction can be expressed by the following equation (2).

F1 = (π / 4) · D1 ² · Pc (2)

The upper end side of the needle valve 42 receives a force F2 in the valve closing direction (downward) due to the pressure in the control chamber R2 (hereinafter referred to as “control pressure Pcntl”). Pressure receiving area of the upper side of the needle valve 42 of the valve closing direction of the force F2 is ^{(π / 4) · D1 2} . Therefore, the force F2 in the valve closing direction can be expressed by the following equation (3).

F2 ＝ (π / 4) ・ D1 ²・ Pcntl (3)

  In addition, a coil spring 44 that constantly urges the needle valve 42 in the valve closing direction is disposed in the control chamber R2. When the urging force (force in the valve closing direction) of the coil spring 44 is F3, the upper end side of the needle valve 42 receives the force in the valve closing direction (F2 + F3) as a whole. The coil spring 44 is provided to prevent the occurrence of a situation where the needle valve 42 opens and the fuel flows out to the combustion chamber when the injection pressure Pc is low, such as when the fuel pump 20 is not operating. ing.

  As will be described later, the control pressure Pcntl can be changed within the range of the injection pressure Pc or less by the opening / closing control of the control valve 43. When the control pressure Pcntl is decreased from the injection pressure Pc to a certain pressure smaller than the injection pressure Pc (hereinafter referred to as “needle valve opening pressure Py”), the needle valve 42 opens (from the closed state). The valve is opened).

  This needle valve opening pressure Py (<Pc) can be expressed by the following equation (4) in consideration of the above equations (1) and (3). Thus, the needle valve opening pressure Py depends on the injection pressure Pc. As described above, the needle valve lift amount Ln is adjusted by the control of the control pressure Pcntl, and the injection hole 41a is opened and closed.

Py = {1 / ((π / 4) ・ D1 ² )} ・ {(π / 4) ・ (D1 ² −D2 ² ) ・ Pc−F3} (4)

  Hereinafter, the control valve 43 will be described with reference to FIG. 2 which is an enlarged view of the control valve 43. The control valve 43 includes a spherical valve body 43a that divides the second predetermined space into a valve body accommodating chamber R3 and a return chamber R4, and an actuator 43b that drives the valve body 43a in the valve opening direction (downward in FIG. 2). And a piston 43c arranged to be slidable in the axial direction dividing the second predetermined space into a valve body accommodating chamber R3 and a pressure chamber R5. The valve body 43a, the actuator 43b, and the piston 43c are arranged coaxially with respect to the axial direction of the second predetermined space.

  The valve body storage chamber R3 communicates with the control chamber R2 through the flow path C2, and the fuel pressure in the valve body storage chamber R3 is always equal to the control pressure Pcntl. The return chamber R4 communicates with the fuel tank T through a flow path C3 provided with a discharge orifice Z1 (constant opening area). Here, the flow path C2, the valve body storage chamber R3, the return chamber R4, and the flow path C3 correspond to the “fuel discharge path” that discharges fuel from the control chamber R2. The pressure chamber R5 communicates with the fuel supply path C1 through the flow path C4, and the fuel pressure in the pressure chamber R5 is always equal to the injection pressure Pc.

  The valve element 43a is movably accommodated in the valve element accommodating chamber R3, and the position (vertical position) of the valve element 43a is adjusted according to the driving force of the actuator 43b. In the state (state shown in FIGS. 1 and 2) in which the valve body 43a is in contact with the valve seat portion (conical portion) 41c of the body 41 formed on the upper end side of the valve body storage chamber R3. The return chamber R4 is shut off and the “fuel discharge path” is shut off. In this state, fuel is not discharged from the control chamber R2.

  Hereinafter, this state is also referred to as a valve closing state of the valve body 43a. Further, the lift amount of the valve body 43a (valve body lift amount Lv) means the downward movement amount (downward amount) of the valve body 43a from this state. That is, in the closed state of the valve body 43a shown in FIGS. 1 and 2, the valve body lift amount Lv is “0”.

  On the other hand, when the valve body 43a moves downward (lowers) from the closed state and is separated from the valve seat 41c, the valve body storage chamber R3 and the return chamber R4 communicate with each other so that the “fuel discharge passage” is opened. It has become. In this state (that is, the valve body lift amount Lv> 0), according to the differential pressure across the discharge orifice Z1 (that is, the differential pressure between the control pressure Pcntl and the fuel pressure (= atmospheric pressure) in the fuel tank T), The fuel is discharged from the control chamber R2 to the fuel tank T through the “fuel discharge passage”. Hereinafter, this state is also referred to as the valve opening state of the valve body 43a, and in this case, the flow rate that passes through the discharge orifice Z1 is referred to as "outflow flow rate Qout".

  In this example, the actuator 43b is composed of a piezo element (piezoelectric / electrostrictive element), and generates a larger driving force (large displacement) as the driving voltage V adjusted / supplied by an instruction from the ECU 50 increases. It is like that. As a result, the valve body lift amount Lv can be adjusted to a larger value as the drive voltage V of the actuator 43b is larger (accordingly, the drive force is larger). When the valve body lift amount Lv is equal to or greater than the value L1 (see FIG. 2, hereinafter referred to as “first lift amount L1”), the valve body 43a contacts the upper end portion of the piston 43c and the upper end portion thereof is lowered below. It pushes in the direction.

  The piston 43c has a bottomed cylindrical shape that opens downward at the lower end thereof and has a flange portion 43c1. The upper end side of the piston 43c receives a downward force F4 due to the pressure in the valve body housing chamber R3 (= control pressure Pcntl), and the lower end side of the piston 43c is caused by the pressure in the pressure chamber R5 (= injection pressure Pc). Receives upward force F5. Here, if the outer diameter of the piston 43c is D3, these forces F3 and F4 can be expressed by the following equations (5) and (6), respectively.

F4 = (π / 4) ・ D3 ²・ Pcntl (5)
F5 = (π / 4) · D3 ² · Pc (6)

  In addition, a coil spring 43d that constantly urges the piston 43c upward is disposed in the pressure chamber R5. When the urging force (upward force) of the coil spring 43d is F6, the lower end side of the piston 43c receives an upward force (F5 + F6) as a whole. Here, since there is a relationship of Pc ≧ Pcntl, there is a relationship of F5 ≧ F4.

  Therefore, when the valve body 43a is not in contact, the piston 43c receives an upward force (hereinafter referred to as “set load F7”) (= F5 + F6−F4) and the upper end surface of the flange portion 43c1 is the body 41. It is maintained in a state of contacting the stopper surface 41d (the state shown in FIGS. 1 and 2). The position of the piston 43c in this state is referred to as “initial position”.

  On the other hand, when the piston 43c is pressed downward by the valve body 43a, the piston 43c causes the coil spring 43d to be in close contact with the downward direction from the initial position (hereinafter referred to as “first position”). It can be lowered until it is called.

  A cylindrical inner space 43c2 communicating with the pressure chamber R5 is formed inside the piston 43c. An inflow orifice Z2 (constant opening area) that connects the internal space 43c2 and the outer surface is formed along a radial direction at a predetermined position on the upper end side of the piston 43c. Here, the flow path C4, the pressure chamber R5, the internal space 43c2, the inflow orifice Z2, the valve body storage chamber R3, and the flow path C2 correspond to the “fuel inflow path” through which fuel flows into the control chamber R2.

  When the piston 43c is in the initial position, the end portion on the outer surface side of the inflow orifice Z2 communicates with the valve body housing chamber R3 so that the “fuel inflow passage” is opened (see FIGS. 1 and 2). . In this state, fuel flows from the fuel supply path C1 to the control chamber R2 through the “fuel inflow path” in accordance with the differential pressure at both ends of the inflow orifice Z2 (accordingly, the differential pressure between the injection pressure Pc and the control pressure Pcntl). It has become. Hereinafter, the flow rate passing through the inflow orifice Z2 in this case is referred to as “inflow rate Qin”. In this case, the minimum flow path area of the “fuel inflow path” is the opening area of the inflow orifice Z2.

  On the other hand, when the piston 43c is in the first position, the end on the outer surface side of the inflow orifice Z2 is blocked by the sliding surface 41e with the piston 43c of the body 41 so that the “fuel inflow path” is blocked. (See FIG. 4C described later). In this state, no fuel flows into the control chamber R2. In this case, the minimum flow area of the “fuel inflow path” is “0”.

  Next, the relationship between the drive voltage V supplied to the actuator 43b and the valve body lift amount Lv will be described with reference to FIG. 3 and FIGS. 4A to 4C. Hereinafter, the driving force of the actuator 43b may be simply referred to as “driving force”. As shown in FIG. 3, when the drive voltage V is between “0” and the value V0, the valve body lift amount Lv is maintained at “0” (that is, the valve body 43a is maintained in the closed state). See 4A). The piston 43c is also maintained at the initial position. Here, the value V0 is a driving voltage corresponding to the case where the driving force is equal to the force F8 required to open the valve body 43a represented by the following equation (7). In the equation (7), the value D4 is the valve seat diameter (seat diameter) of the valve seat portion 41c (see FIG. 2).

F8 = (π / 4) · D4 ² · Pcntl (7)

  When the drive voltage V reaches the value V0, the valve body 43a is opened, and the valve body lift amount Lv increases from “0” toward the first lift amount L1 as the drive voltage V increases from the value V0. When the drive voltage V reaches the value VA, the valve body lift amount Lv reaches the first lift amount L1, and the valve body 43a contacts the upper end portion of the piston 43c (see FIG. 4B). Even at this stage, the piston 43c is still maintained at the initial position. Here, the driving force corresponding to the driving voltage V = VA corresponds to the “first driving force”.

  When the drive voltage V increases from the value VA, the valve body 43a presses the piston 43c downward. However, until the driving voltage V reaches the value VB, which is a value for generating a driving force equal to the set load F7, the driving force is not more than the set load F7, so the piston 43c is still maintained at the initial position. The As a result, the valve body lift amount Lv is also maintained at the first lift amount L1. Here, the driving force corresponding to the driving voltage V = VB corresponds to the “second driving force”.

  As the drive voltage V reaches the value VB and increases from the value VB, the piston 43c moves downward from the initial position toward the first position by the pressing of the valve body 43a. As a result, the valve body lift amount Lv also increases from the first lift amount L1. When the drive voltage V reaches the value VC, the piston 43c reaches the first position, and the valve body lift amount Lv reaches the second lift amount L2 (see FIG. 4C). Here, the driving force corresponding to the driving voltage V = VC corresponds to the “third driving force”.

  When the drive voltage V increases from the value VC, the valve body 43a tries to push the piston 43c further downward from the first position. However, the piston 43c cannot move downward from the first position due to the close contact of the coil spring 43d. That is, the piston 43c is maintained at the first position. As a result, the valve body lift amount Lv is also maintained at the second lift amount L2.

  As described above, if the drive voltage V is adjusted to a value between the value VA and the value VB (that is, if the drive force is adjusted between the first drive force and the second drive force), the valve body lift amount Lv. Is maintained at the first lift amount L1, and if the drive voltage V is adjusted to the value VC or more (that is, if the drive force is adjusted to the third drive force or more), the valve body lift amount Lv becomes the second lift amount L2. Maintained.

  Therefore, if the drive voltage V is adjusted to a certain value (for example, the median value, the value V1 in FIG. 3) between the maximum value of the variation range RA of the value VA and the minimum value of the variation range RB of the value VB, the valve body. If the lift amount Lv can be stably maintained at the first lift amount L1, and the drive voltage V is adjusted to a value (for example, the value V2 in FIG. 3) larger than the maximum value of the variation range RC of the value VC, the valve body The lift amount Lv can be stably maintained at the second lift amount L2.

  Next, an example of the operation of the fuel injection control device 10 will be described with reference to FIG. 5 and FIGS. Prior to time t1, the drive voltage V = 0. As a result, as shown in FIG. 4A, the control valve 43 is maintained in the closed state, and the “fuel discharge path” is shut off. That is, the valve body lift amount Lv = 0 and the outflow flow rate Qout = 0. On the other hand, since the piston 43c is maintained at the initial position and the “fuel inflow passage” is opened, the control pressure Pcntl is maintained at a pressure equal to the injection pressure Pc (that is, the inflow flow rate Qin = 0). As a result, the control pressure Pcntl is larger than the needle valve opening pressure Py expressed by the above equation (4). Therefore, the needle valve 42 is maintained in a closed state. That is, the needle valve lift amount Ln = 0, and no fuel is injected. Accordingly, the fuel injection rate is also “0”.

  When the driving voltage V is changed stepwise from “0” to the above-described value V1 (see FIG. 3) according to an instruction from the ECU 50 at time t1, as described above, the valve body 43a is moved to the piston after time t1. Although contacting the piston 43c, the piston 43c is still stably maintained at the initial position, and the valve body lift amount Lv is stably maintained at the first lift amount L1 (see FIGS. 3 and 4B). That is, at time t1, the control valve 43 is opened and the “fuel discharge passage” is opened. After time t1, fuel is discharged from the control chamber R2 through the “fuel discharge passage” (Qout> 0), and the control is performed. The pressure Pcntl decreases from the injection pressure Pc. Along with this, fuel flows from the fuel supply path C1 into the control chamber R2 through the opened “fuel inflow path” (Qin> 0). As a result, the control pressure Pcntl decreases from the injection pressure Pc at a speed corresponding to the difference between the outflow flow rate Qout and the inflow flow rate Qin (= Qout−Qin).

  When the control pressure Pcntl decreasing after the time t1 reaches the needle valve opening pressure Py expressed by the above equation (4) at the time t2, the needle valve 42 is opened (the needle valve lift amount is reduced). As a result, fuel injection is started and the injection rate increases from “0”.

  After time t2 when the needle valve 42 is opened, the needle valve 42 has a relatively small needle valve ascent rate (hereinafter referred to as “first ascent”) corresponding to the rate of decrease in the volume of fuel in the control chamber R2 (= Qout−Qin). (Referred to as “speed”) (see times t2 to t4). During this time, fuel injection is continued. Since the needle valve ascent speed (= first ascent speed) is relatively small, the needle valve lift amount Ln is maintained at a relatively small value, and the injection rate is maintained at a relatively small value without significantly increasing. The

  After time t2 when the needle valve 42 opens, the injection pressure Pc decreases immediately after the start of fuel injection and then immediately increases due to pressure pulsation in the fuel supply path C1. To go.

Further, when the needle valve 42 is opened, as described above, the tip side portion of the tapered portion 42a with respect to the portion contacting the circular valve seat portion 41b is also exposed to the fuel having the injection pressure Pc. The pressure receiving area on the lower end side of the needle valve 42 with respect to the direction force F1 is equal to the pressure receiving area on the lower end side of the needle valve 42 with respect to the force F2 in the valve closing direction (the above expressions (2) and (3) are See: Pressure-receiving area = (π / 4) · D1 ² ).

Due to this, after time t2 when the needle valve 42 is opened, the control pressure Pcntl is changed from the pressure in the nozzle chamber R1 (= injection pressure Pc) to the control chamber R2 corresponding to the urging force F3 of the coil spring 44. The pressure component (= F3 / ((π / 4) · D1 ² ), hereinafter referred to as “spring force equivalent pressure component Px”) is quickly increased to the pressure (Pc−Px) obtained. At time t3, the control pressure Pcntl reaches the pressure (Pc−Px). After time t3, the control pressure Pcntl changes with the pressure (Pc−Px). In this example, since the spring constant of the coil spring 44 is very small, the urging force F3 of the coil spring 45 (accordingly, the spring force equivalent pressure Px) is treated as being constant regardless of the needle valve lift amount.

  When the drive voltage V is changed stepwise from the value V1 to the above-described value V2 (see FIG. 3) according to an instruction from the ECU 50 at time t4, as described above, the piston 43c is operated by the valve body 43a after time t4. Is pressed and the piston 43c is stably maintained at the first position, and the valve body lift amount Lv is stably maintained at the second lift amount L2 (see FIGS. 3 and 4C). That is, after time t4, the “fuel inflow path” is shut off and the inflow flow rate Qin = 0. On the other hand, the “fuel discharge path” is still open (Qout> 0).

  As a result, after time t4, the needle valve 42 moves at a speed corresponding to the rate of decrease in the volume of fuel in the control chamber R2 (= Qout), that is, a needle valve ascending speed (hereinafter, “ (Referred to as “second rising speed”) (see times t4 to t5). During this time, fuel injection is continued. Since the needle valve ascent speed (= second ascent speed) is large, the needle valve lift amount Ln also increases significantly, and the injection rate increases significantly.

  When the drive voltage V is changed stepwise from the value V2 to “0” according to an instruction from the ECU 50 at time t5, the valve body lift amount Lv returns to “0” after time t5, and the piston 43c is also in the initial position. Return (see FIG. 4D). That is, the control valve 43 returns to the closed state, the “fuel discharge path” is shut off (Qout = 0), and the fuel discharge from the control chamber R2 through the “fuel discharge path” is stopped. On the other hand, the “fuel inflow path” is opened again, and the inflow of fuel into the control chamber R2 through the “fuel inflow path” is started again (Qin> 0). As a result, after time t5, the needle valve 42 descends at a speed corresponding to the fuel volume increase speed (= Qin) in the control chamber R2 (see times t5 to t6). During this time, fuel injection is continued.

  At time t6 when the needle valve lift amount Ln reaches “0”, the needle valve 42 is closed and fuel injection is terminated. After time t6, fuel is supplied from the fuel supply passage C1 into the control chamber R2 through the “fuel inflow passage” (Qin> 0), so that the control pressure Pcntl approaches the injection pressure Pc. After the control pressure Pcntl coincides with the injection pressure Pc (Qin = 0), the control pressure Pcntl is maintained at a pressure equal to the injection pressure Pc, as before time t1.

  As described above, according to the embodiment of the fuel injection control device of the present invention, fuel is supplied from the fuel supply passage C1 for supplying high-pressure (injection pressure Pc) fuel in the common rail 30 to the control chamber R2 of the injector 40. The flow path (that is, the “fuel inflow path”) is opened when the valve body lift amount Lv of the valve body 43a is the first lift amount L1 (see FIG. 4B), and the valve body lift amount Lv is the first. In the case of the 2-lift amount L2 (see FIG. 4C), it is blocked. Accordingly, the valve body lift amount Lv is first adjusted to the first lift amount L1 to open the needle valve 42. While the needle valve 42 is being lifted, the valve body lift amount Lv is changed from the first lift amount L1 to the second lift amount. By switching to the amount L2, the needle valve ascent speed can be switched in two stages from a relatively small first ascent speed to a second ascent speed (> first ascent speed).

  Accordingly, the total amount of fuel injected during the ignition delay time can be reduced by matching the period during which the needle valve ascent rate is maintained at the first ascent rate with the ignition delay time. As a result, noise associated with premixed combustion of fuel injected within the ignition delay time can be reduced.

  In the example shown in FIG. 5, when the valve body lift amount Lv is maintained at the first lift amount L1, the drive voltage V supplied to the actuator 43b is maintained at a value V1 between the value VA and the value VB. (See FIG. 3). Further, when the valve body lift amount Lv is maintained at the second lift amount L2, the drive voltage V is maintained at a value V2 greater than the value VC (see FIG. 3). Therefore, even if the relationship between the driving voltage V and the driving force varies due to variations among the individual actuators 43b, etc., or even if a change in the viscosity of the fuel due to a temperature change occurs, the valve lift Lv Can be stably maintained at the first and second lift amounts L1 and L2, respectively. As a result, the inflow flow rate Qin and the outflow flow rate Qout are stabilized while the valve body lift amount Lv is maintained at the first lift amount L1 or the second lift amount L2, and the needle valve ascent speed is increased by the first. It can be stably maintained at the speed or the second ascending speed.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, as shown in the example of FIG. 5, the valve body lift amount Lv is first adjusted to the first lift amount L1 to open the needle valve 42. By switching the body lift amount Lv from the first lift amount L1 to the second lift amount L2, the needle valve ascent speed is switched in two stages from the first ascent speed to the second ascent speed (> first ascent speed). However, by adjusting the valve body lift amount Lv to the first lift amount L1 and opening the needle valve 42, and maintaining the valve body lift amount Lv at the first lift amount L1 thereafter, the needle valve ascent rate is increased. You may maintain 1 ascending speed. Similarly, the valve body lift amount Lv is adjusted to the second lift amount L2, the needle valve 42 is opened, and thereafter the valve body lift amount Lv is maintained at the second lift amount L2, thereby increasing the needle valve ascent rate. The second rising speed may be maintained.

  Further, in the above embodiment, when the valve body lift amount Lv is the first lift amount L1 (that is, when the piston 43c is in the initial position), the minimum flow area of the “fuel inflow passage” is the opening of the inflow orifice Z2. When the valve body lift amount Lv is the second lift amount L2 (that is, when the piston 43c is in the first position), the minimum flow area of the “fuel inflow passage” is configured to be “0”. However, as shown in FIG. 6, a fuel inflow path C5 in which the second orifice Z3 is interposed for allowing the fuel to flow from the fuel supply path C1 into the valve body housing chamber R3 may be added.

  In this case, the minimum flow area of the “fuel inflow passage” as a whole is the sum of the opening area of the inflow orifice Z2 and the opening area of the second orifice Z3 when the piston 43c is in the initial position. When it is in the position, the opening area of the second orifice Z3 is obtained. That is, according to the configuration shown in FIG. 6, the change rate of the minimum flow path area as the whole “fuel inflow path” can be changed with respect to the first embodiment. In other words, it is possible to change the change rate of the needle valve ascending speed that changes in two stages.

  Further, in the above-described embodiment, the “fuel inflow passage” is blocked by the end portion on the outer surface side of the inflow orifice Z2 being blocked by the sliding surface 41e with the piston 43c of the body 41 (so-called sliding seal). However, the “fuel inflow passage” may be blocked by the configuration shown in FIG. 7.

  That is, in the configuration shown in FIG. 7, the piston 43 c has a tapered surface that expands from the upper end side to the lower end side of the piston 43 c at the end of the lower end side where the internal space 43 c 2 faces the pressure chamber R 5. 43c3 is provided, and a member 43d having a protruding portion 43d1 protruding upward toward the tapered surface 43c3 is fixedly disposed in the pressure chamber R5. Regardless of the position of the piston 43c, the inflow orifice Z2 always communicates the internal space 43c2 and the valve body accommodating chamber R3.

  When the piston 43c is in the initial position, the tapered surface 43c3 is separated from the protrusion 43d1, the internal space 43c2 and the pressure chamber R5 communicate with each other (that is, the “fuel inflow passage” is opened), and the piston 43c In the case of the first position, the tapered surface 43c3 abuts against the protruding portion 43d1, and the internal space 43c2 and the pressure chamber R5 are blocked (that is, the “fuel inflow path” is blocked). Thus, since the “fuel inflow path” is blocked by a so-called “valve seal” instead of the “sliding seal” as in the above embodiment, the “fuel inflow path” is more reliable and more stable than the above embodiment. Can be blocked.

  In the above embodiment, when the control valve 43 opens and the control pressure Pcntl decreases from the injection pressure Pc, the upward force acting on the piston 43c based on the differential pressure (injection pressure Pc−control pressure Pcntl). Will increase. Therefore, it is necessary to increase the size of the actuator 43b in order to ensure a sufficient driving force of the actuator 43b to counteract the force (load) based on the differential pressure.

  In order to cope with this, the configuration shown in FIG. 8 may be adopted for the piston 43c. That is, the lower end side of the piston 43c is formed so as to communicate with the valve body accommodating chamber R3 via the communication passage 43c4 penetrating inside along the axial direction instead of the pressure chamber R5 (internal pressure is the injection pressure Pc). The rear chamber R6 (internal pressure is the control pressure Pcntl) is configured as desired. The pressure chamber R5 communicating with the fuel supply path C1 via the flow path C4 in which the third orifice Z4 is interposed is always partitioned from the back chamber R6 by an annular recess formed in the outer periphery of the intermediate portion in the axial direction of the piston 43c. The compartments are formed as follows.

  When the piston 43c is in the initial position (in the case shown in FIG. 8), the valve body accommodating chamber R3 and the pressure chamber R5 communicate with each other by separating the tapered surface 43c5 of the piston 43c and the corner 41f of the body 41 (that is, The “fuel inflow passage” is opened). In this case, the minimum flow path area of the “fuel inflow path” is the opening area of the third orifice Z4. On the other hand, when the piston 43c is in the first position, the taper surface 43c5 and the corner portion 41f come into contact with each other so that the valve body housing chamber R3 and the pressure chamber R5 are blocked (that is, the “fuel inflow path” is blocked). ) In this case, the minimum flow path area of the “fuel inflow path” is “0”.

  According to the configuration shown in FIG. 8, both ends of the piston 43c receive the same pressure (specifically, the control pressure Pcntl). Therefore, even if the control pressure Pcntl is reduced from the injection pressure Pc in the open state of the control valve 43, the above-described “upward force acting on the piston based on the differential pressure” does not occur. Therefore, the increase in size of the actuator 43b described above can be avoided.

1 is an overall schematic configuration diagram of a fuel injection control device according to an embodiment of the present invention. It is an enlarged view of the control valve shown in FIG. 2 is a graph showing a relationship between a drive voltage supplied to an actuator that drives a valve body of a control valve and a lift amount of the valve body in the fuel injection control device shown in FIG. 1. It is the figure which showed the valve closing state of the control valve. It is the figure which showed the case where it is the valve opening state of a control valve, and the valve body lift amount is 1st lift amount. It is the figure which showed the case where it is the valve opening state of a control valve, and the valve body lift amount is the 2nd lift amount. It is the figure which showed the case where a control valve returns from a valve opening state to a valve closing state. 2 is a time chart showing an example of changes in physical quantities during operation of the fuel injection control device shown in FIG. 1. It is an enlarged view of the 1st modification of a control valve. It is an enlarged view of the 2nd modification of a control valve. It is an enlarged view of the 3rd modification of a control valve. It is a schematic block diagram of the conventional fuel-injection control apparatus. It is a schematic block diagram of the control valve in the conventional fuel injection control apparatus. It is the figure which showed the case where the valve body lift amount of the control valve shown in FIG. 10 is 1st lift amount. It is the figure which showed the case where the valve body lift amount of the control valve shown in FIG. 10 is 2nd lift amount.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Fuel pump, 30 ... Common rail, 40 ... Injector, 41 ... Body, 41a ... Injection hole, 41b ... Circular valve seat part, 41c ... Circular valve seat part, 42 ... Needle valve, 42a ... Taper part, 43 ... Control valve 43a ... Valve body, 43b ... Actuator, 43c ... Piston, 43c2 ... Internal space, 43d ... Coil spring, 50 ... ECU, C1 ... Fuel supply path, Z1 ... Discharge orifice, Z2 ... Inflow orifice

Claims (10)

A needle valve for opening and closing a nozzle hole for injecting fuel into the combustion chamber of the internal combustion engine;
A nozzle in which one end of the needle valve receives a force in the valve opening direction due to an injection pressure that is an internal fuel pressure, and in which the internal fuel is injected from the nozzle hole toward the combustion chamber when the needle valve is open. Room,
A control chamber in which the other end side of the needle valve receives a force in a valve closing direction by a control pressure that is a pressure of an internal fuel; and
A high-pressure generator that generates high-pressure fuel;
A fuel supply path for supplying the high-pressure fuel generated by the high-pressure generator to the nozzle chamber;
A fuel inflow path for allowing fuel to flow into the control chamber from the fuel supply path;
A fuel discharge passage for discharging fuel from the control chamber;
A control valve interposed in the fuel discharge path and communicating / blocking the fuel discharge path;
A fuel injection control device that adjusts the position of the needle valve by controlling the control valve and controlling the control pressure to perform fuel injection control,
The control valve is
A valve body that communicates and blocks the fuel discharge path;
An actuator that generates a driving force that presses the valve body in a valve opening direction, and controls the opening and closing of the valve body by adjusting the driving force, and the valve in an open state according to an increase in the driving force. An actuator for increasing the lift amount in the valve opening direction from the closed state of the valve body;
When the lift amount of the valve body is less than the first lift amount greater than zero, the valve body is maintained in its initial position without contacting the valve body, and the lift amount of the valve body reaches the first lift amount. Then, contact with the valve body starts at the initial position, and the valve body is pressed by the valve body in response to an increase in the lift amount of the valve body from the first lift amount, and the valve body opens from the initial position. A piston that moves to
When the driving force of the actuator reaches the first driving force, the lift amount of the valve body is configured to reach the first lift amount,
The piston cannot move from the initial position due to the pressing of the valve body when the driving force of the actuator is less than or equal to a second driving force that is greater than the first driving force, and the piston does not move from the initial driving force. It is arranged and configured to move from the initial position in the valve opening direction of the valve body by pressing the valve body according to the increase,
The minimum flow passage area of the fuel inflow passage is smaller when the piston is at the first position on the valve opening direction side of the valve body than the initial position than when the piston is at the initial position. A fuel injection control device in which the fuel inflow path is configured. The fuel injection control device according to claim 1,
The piston reaches the first position when the driving force of the actuator reaches a third driving force that is greater than the second driving force, and the first position when the driving force of the actuator is greater than the third driving force. A fuel injection control device arranged and configured to be maintained in position. The fuel injection control device according to claim 2,
When the fuel injection is performed, the driving force of the actuator is first adjusted to a first predetermined value between the first driving force and the second driving force, and then a second predetermined value larger than the third driving force. Fuel injection control device adjusted to the value. In the fuel injection control device according to claim 2 or 3,
The control valve includes a valve body storage chamber that communicates with the control chamber, and a pressure chamber that communicates with the fuel supply path.
The valve body is movably housed in the valve body housing chamber, the fuel discharge passage is shut off in the closed state in which the valve body is in contact with a valve seat provided in the valve body housing chamber, The valve body is configured to communicate with the fuel discharge path in the opened state in which the valve body is separated from the valve seat portion;
One end of the piston faces the valve body from the side facing the valve seat in the valve body housing chamber toward the valve body, and the other end of the piston faces the pressure chamber, The valve body is configured to be in contact with one end side of the piston,
A fuel injection control device, wherein the control chamber and the valve body storage chamber communicate with each other, and the valve body storage chamber constitutes a part of the fuel discharge passage. The fuel injection control device according to claim 4, wherein
A fuel injection control device provided with an elastic member that constantly urges the piston toward the valve body in the pressure chamber. The fuel injection control device according to claim 5, wherein
The fuel injection control device, wherein the elastic member is a spring, and the spring is in a close contact state when the piston is in the first position. The fuel injection control device according to any one of claims 4 to 6,
The piston includes an orifice that communicates an internal space communicating with the pressure chamber and an outer surface on one end side of the piston, and the outer surface side of the orifice is the valve when the piston is in the initial position. Communicating with the body accommodating chamber, and configured so that the outer surface side of the orifice is blocked from the valve body accommodating chamber when the piston is in the first position;
The second communication path that connects the pressure chamber and the fuel supply path, the pressure chamber, the internal space, the orifice, the valve body storage chamber, and the first communication path constitute the fuel inflow path. Fuel injection control device. The fuel injection control device according to claim 7,
A fuel injection control device comprising a second fuel inflow passage through which a second orifice is interposed, for allowing fuel to flow into the valve body housing chamber from the fuel supply passage. The fuel injection control device according to claim 4 or 5,
The piston includes an orifice that communicates an internal space that communicates with the pressure chamber and an outer surface on one end side of the piston, and the outer surface side of the orifice communicates with the valve body storage chamber,
The piston is provided with a tapered surface whose diameter increases from one end side to the other end side of the piston at a portion where the internal space at the end portion on the other end side faces the pressure chamber. A projecting portion projecting toward the tapered surface is fixedly disposed, and when the piston is in the initial position, the tapered surface is separated from the projecting portion and communicates the internal space and the pressure chamber; When the piston is in the first position, the tapered surface is configured to abut against the projecting portion to shut off the internal space and the pressure chamber,
The second communication path that connects the pressure chamber and the fuel supply path, the pressure chamber, the internal space, the orifice, the valve body storage chamber, and the first communication path constitute the fuel inflow path. Fuel injection control device. In the fuel injection control device according to claim 2 or 3,
The control valve includes a valve body storage chamber that communicates with the control chamber, and a pressure chamber that communicates with the fuel supply path.
The valve body is movably housed in the valve body housing chamber, the fuel discharge passage is shut off in the closed state in which the valve body is in contact with a valve seat provided in the valve body housing chamber, The valve body is configured to communicate with the fuel discharge path in the opened state in which the valve body is separated from the valve seat portion;
One end side of the piston faces the valve body from the side facing the valve seat in the valve body housing chamber toward the valve body, and the valve body can come into contact with one end side of the piston. Configured,
The other end side of the piston is desired in a back chamber formed so as to communicate with the valve body housing chamber through a third communication passage penetrating inside along the axial direction, and the piston is placed in the back chamber. An elastic member that constantly urges toward the valve body side is provided,
The pressure chamber is defined by an annular recess formed in the outer periphery of the intermediate portion in the axial direction of the piston,
The valve body storage chamber and the pressure chamber communicate with each other when the piston is in the initial position, and the valve body storage chamber and the pressure chamber are blocked when the piston is in the first position. Configured,
An orifice is formed in the second communication path that connects the pressure chamber and the fuel supply path,
The first communication passage communicating the control chamber and the valve body storage chamber, and the valve body storage chamber constitute a part of the fuel discharge passage, the second communication passage, the pressure chamber, the valve body storage A fuel injection control device in which the chamber and the first communication passage constitute the fuel inflow passage.

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