JP2008309015A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce actuator drive force necessary for opening a second control valve in a fuel injection control device capable of changing over needle valve rising velocity in two stages by opening a first and a second control valve controlling discharge of fuel from a control chamber to a fuel tank in order. <P>SOLUTION: Two systems are provided as channels for discharging fuel from the control chamber positioned at an injector back surface, and the first and the second control valve 43, 44 are installed in each system. A first valve element 43a of the first control valve 43 is driven by the actuator 43b and a second valve element 44a of the second control valve 44 are driven by pressing of the first valve element 43a via a piston 44b. Pressure in a pressure introduction chamber R7 communicating to a first back pressure chamber R4 rises to pressure in the control chamber by action of an orifice Z1 under a condition where the first valve element 43a is open and the second valve element 44a is close. The piston 44b receives force in a direction energizing actuator generation force by the pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

Conventionally, as shown in FIG. 17, a needle valve 120 that opens and closes a nozzle hole 110 that injects 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. 17) of 120 receives a force in the valve opening direction (upward direction in FIG. 17), and internal fuel 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. 17) of the needle valve 120 receives a force in the valve closing direction (downward direction in FIG. 17) 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 hydraulic pump + common rail) to the nozzle chamber 130, and fuel flowing from the fuel supply path 150 to the control chamber 140. A fuel inflow path 170 in which an inflow orifice 160 is inserted, a fuel discharge path 190 in which a discharge orifice 180 is discharged from the control chamber 140 to a fuel tank (not shown), and a fuel discharge path 190. There is known a fuel injection control device that includes a control valve 210 that is connected to the fuel discharge path 190 and communicates with and shuts off the 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. (Moves upward in FIG. 17), 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. 17 is moved 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. 17). 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 outflow flow rate Qout may be increased stepwise at a predetermined time during needle needle ascent. For this purpose, for example, in the apparatus shown in FIG. 17, the fuel discharge system from the control chamber 140 may be configured as shown in FIG. 18, the same or equivalent members as those shown in FIG. 17 are denoted by the same reference numerals as those in FIG.

  That is, in the fuel discharge system shown in FIG. 18, the first valve body 250 is placed in the first valve body housing chamber 240 connected to the control chamber 140 via the flow path 230 in which the first discharge orifice 220 is interposed. Contained. The first valve body 250 is movable in the valve opening / closing direction (vertical direction in FIG. 18) in the first valve body housing chamber 240, and is connected to the first valve body housing chamber 240 and the fuel tank. Further, the first back pressure chamber 260 is communicated with or cut off.

  The second valve element 310 is accommodated in the second valve element accommodating chamber 290 connected to the control chamber 140 via the flow path 280 in which the second discharge orifice 270 is interposed. The second valve element 310 is movable in the second valve element accommodating chamber 290 in the valve opening / closing direction (vertical direction in FIG. 18) coaxially with the first valve element 250, and is accommodated in the second valve element accommodating chamber 290. The chamber 290 and the first valve body accommodation chamber 240 are communicated and blocked.

  The actuator 320 (for example, composed of a piezo element (piezoelectric / electrostrictive element)) generates a driving force that presses the first back pressure chamber 260 side portion of the first valve body 250 in the valve opening direction. The valve body lift amount (the amount of movement downward from the position shown in FIG. 18) can be adjusted.

  When the lift amount of the first valve body 250 reaches a predetermined amount (distance z shown in FIG. 18), the lower end of the first valve body 250 comes into contact with the first valve body housing chamber 240 side portion of the second valve body 310. As the lift amount of the first valve body 250 increases, the second valve body 310 can move from the valve closing position to the valve opening direction (downward from the position shown in FIG. 18) while being pressed by the first valve body 250 (ie, downward from the position shown in FIG. 18). The second valve body lift amount (the amount of movement downward from the position shown in FIG. 18) can be increased). Thus, the 1st valve body 250 is driven by the actuator 320, and the 2nd valve body 310 is driven by the press of the 1st valve body 250 in a valve opening state.

  With the above configuration, when the first valve body lift amount = 0, the second valve body lift amount = 0 (that is, the state shown in FIG. 18). In this case, the first and second valve bodies 250 and 310 are both in the closed state, and the fuel outflow rates Qout1 and Qout2 = 0 through the first and second discharge orifices 220 and 270. Therefore, fuel does not flow out of the control chamber 140.

  On the other hand, as shown in FIG. 19, when 0 <first valve body lift amount ≦ z (in FIG. 19, first valve body lift amount = z), only the first valve body 250 is opened, and the outflow flow rate While Qout2 = 0, the outflow flow rate Qout1> 0. In this case, the needle valve 120 rises at a needle valve ascent rate (= first ascent rate) corresponding to the flow rate difference (= Qout1-Qin).

  Furthermore, as shown in FIG. 20, when z <the first valve body lift amount (in FIG. 20, the first valve body lift amount = maximum value max), the first and second valve bodies 250, 310 are both opened. And the outflow flow rate Qout1, Qout2> 0. In this case, the needle valve 120 rises at a needle valve ascent rate (= second ascent rate> first ascent rate) corresponding to the flow rate difference (= Qout1 + Qout2-Qin).

  As described above, when the needle valve 120 is raised in the state shown in FIG. 19 (the first valve body is open and the second valve body is closed), the driving force of the actuator 320 is increased and the state shown in FIG. By changing to (when both the first and second valve bodies are opened), the needle valve ascending speed can be switched from “small” to “large” in two stages.

  Hereinafter, the case where the actuator 320 is composed of a piezo element will be described in particular. In this case, the actuator 320 generates a driving force that presses the first valve body 250 in the valve opening direction as it tries to extend in the vertical direction in FIG.

  FIG. 21 shows a case where the actuator 320 is composed of a piezoelectric element, a driving voltage, a driving force of the actuator 320 (hereinafter also referred to as “actuator generating force”), and an extension amount of the actuator 320 (= first valve lift). (Hereinafter also referred to as “actuator lift amount”). Thus, when the drive voltage is constant, the amount of actuator generated decreases as the actuator lift increases. In order to increase the actuator generation force with a constant actuator lift, it is necessary to increase the drive voltage.

  FIG. 22 shows the state of the first and second valve bodies 250 and 310 in order to switch the needle valve ascending speed from “small” to “large” in two stages when the actuator 320 is made of a piezo element. (The first and second valve bodies are both closed), the state shown in FIG. 19 (the first valve body is open, the second valve body is closed), and the state shown in FIG. The transition of the relationship between the drive voltage, the actuator generating force, and the actuator lift amount in the case where the second valve body is sequentially changed to the valve opening state is shown.

  As indicated by a point o in FIG. 22, when the drive voltage is “0”, the actuator generation amount and the actuator lift amount are both “0”. Therefore, the states of the first and second valve bodies 250 and 310 are as shown in FIG. 18 (the first and second valve bodies are both closed).

  In this state, as shown by a point a, it is necessary to set the actuator generation force to a force necessary for opening the first valve body 250 in a state where the drive voltage is “0” and the actuator lift amount = 0. When the value increases stepwise to the correct value V1, the first valve body 250 opens (that is, the actuator lift amount increases from “0”). As a result, a large differential pressure is generated between both sides of the first discharge orifice 220 due to the generation of the outflow flow rate Qout1 (> 0), and the pressure in the first valve body housing chamber 240 is greatly reduced from the control pressure Pcntl. To do. As a result, the force received by the first valve body 250 in the valve closing direction decreases, so that the first valve body lift amount (= actuator lift amount) further increases, and the actuator generation force decreases accordingly. . As indicated by point b, when the actuator lift amount reaches the value z, the first valve body 250 contacts the second valve body 310 and the increase in the actuator lift amount stops. As a result, the state of the first and second valve bodies 250 and 310 is maintained in the state shown in FIG. 19 (the first valve body is opened and the second valve body is closed).

  Subsequently, in this state, as indicated by a point c, the driving voltage is set to the force necessary for opening the second valve body 310 from the value V1 and the actuator lift force = z in the state where the actuator lift amount = z. The second valve element 310 is opened (that is, the actuator lift amount is increased from the value z). As a result, due to the generation of the outflow flow rate Qout2 (> 0), a large differential pressure is generated between both sides of the second discharge orifice 270, and the pressure in the second valve body accommodating chamber 290 is greatly reduced from the control pressure Pcntl. To do. As a result, the force received by the second valve body 310 in the valve closing direction decreases, so that the actuator lift amount further increases, and the actuator generation force decreases accordingly. As indicated by a point d, when the actuator lift amount reaches the maximum value max, the increase in the actuator lift amount stops. As a result, the states of the first and second valve bodies 250 and 310 are maintained in the state shown in FIG. 20 (both the first and second valve bodies are opened).

  Here, as described above, in the state shown in FIG. 19 (corresponding to the point b in FIG. 22), the pressure in the first valve body housing chamber 240 is greatly reduced below the control pressure Pcntl. On the other hand, the pressure in the second valve body storage chamber 290 is maintained at the control pressure Pcntl. As a result, a large force acts on the second valve body 310 in the valve closing direction due to this differential pressure. Accordingly, in the state shown in FIG. 19 (corresponding to the point b in FIG. 22), the increase amount F (see FIG. 22) of the actuator generating force necessary for opening the second valve body 310 is very large. Value. As a result, the value V2 of the drive voltage necessary for opening the second valve body 310 becomes very large. This leads to an increase in the size of the actuator 320. The case where the actuator 320 is composed of a piezoelectric element has been described above. However, even when the actuator 320 is of other types, the actuator generation force necessary for opening the second valve body 310 is also large. This may cause a problem of an increase in the size of the actuator 320.

  An object of the present invention is a fuel injection control apparatus that includes first and second control valves that control the discharge of fuel from a control chamber to a fuel tank and that can switch the needle valve ascent speed in two stages. In the type in which the first valve body of the valve is driven by an actuator and the second valve body of the second control valve is driven by pressing the first valve body in the open state, it is necessary for opening the second valve body An object of the present invention is to provide an actuator that can reduce the actuator driving force and suppress an increase in the size of the actuator.

  The fuel injection control device according to the present invention has the same configuration as the device shown in FIG. 17 described above, except for the fuel discharge system from the control chamber. Regarding the fuel discharge system from the control chamber, the fuel injection control device according to the invention is generally arranged between a first fuel discharge passage for discharging fuel from the control chamber to a fuel tank, and the first fuel discharge passage. A first control valve that communicates and blocks the first fuel discharge path, a second fuel discharge path that discharges fuel from the control chamber to the fuel tank, and a second fuel discharge path that is interposed in the second fuel discharge path. And a second control valve for communicating / blocking the second fuel discharge path. Then, by controlling the first and second control valves to control the control pressure in the control chamber, the position of the needle valve is adjusted to perform fuel injection control.

  The first control valve is movably accommodated in the first valve body housing chamber communicating with the control chamber, the first back pressure chamber communicating with the fuel tank, and the first valve body housing chamber. A first valve body that communicates and blocks the one valve body housing chamber and the first back pressure chamber, and a driving force that presses the first back pressure chamber side portion of the first valve body in a valve opening direction. And an actuator capable of adjusting a lift amount in the valve opening direction from the closed state of the first valve body. Here, the first valve body storage chamber and the first back pressure chamber constitute a part of the first fuel discharge passage.

The second control valve is movably accommodated in the second valve body housing chamber communicating with the control chamber, the second back pressure chamber communicating with the fuel tank, and the second valve body housing chamber. A second valve body that communicates and blocks the two-valve body storage chamber and the second back pressure chamber, a pressure introduction chamber that communicates with the first back pressure chamber,
A piston that divides the second back pressure chamber and the pressure introduction chamber; Here, the second valve body accommodation chamber and the second back pressure chamber constitute a part of the second fuel discharge path.

  The piston has one end facing the second back pressure chamber and the other end facing the pressure introducing chamber, and receives a force in the direction from the other end to the one end due to the pressure in the pressure introducing chamber. When the lift amount of one valve body is greater than or equal to a predetermined amount, the other end is in contact with the first valve body and is pressed against the first valve body in response to an increase in the lift amount of the first valve body. It is movable in the direction from the end side to the one end side, and the one end side comes into contact with the second back pressure chamber side portion of the second valve body to press the second valve body in the valve opening direction. Arranged and configured. Here, it is preferable that the first valve body, the piston, and the second valve body are arranged coaxially.

  According to the above configuration, the first valve body of the first control valve is driven in the valve opening direction by the actuator, and the lift amount of the first valve body can be adjusted by adjusting the driving force of the actuator. The second valve body of the second control valve is driven in the valve opening direction via the piston by the pressing of the first valve body in the valve open state. Hereinafter, the open state and the closed state of the valve body are referred to as “open” and “closed”, respectively.

  Here, since the other end of the piston faces the pressure introduction chamber, the piston receives a force in the direction from the other end side of the piston to the one end side (that is, a force in the valve opening direction of the second valve body) due to the pressure in the pressure introduction chamber. . The pressure introducing chamber communicates with the first back pressure chamber. Here, when the first valve body of the first control valve is “open”, the pressure in the first back pressure chamber (accordingly, the pressure in the pressure introduction chamber) is due to the presence of the fuel flow in the first fuel discharge passage. The pressure in the fuel tank (ie, atmospheric pressure) can be higher. In addition, when the second valve body of the second control valve is “closed”, there is no fuel flow in the second fuel discharge passage, so the pressure in the second back pressure chamber facing the one end of the piston is equal to the atmospheric pressure. Become.

  Therefore, when the first valve body is “open” and the second valve body is “closed”, the pressure in the pressure introduction chamber is greater than the pressure in the second back pressure chamber (≈atmospheric pressure), and the piston has a pressure in the pressure introduction chamber. To receive the force in the valve opening direction of the second valve body (hereinafter referred to as “second valve body opening assist force”). This second valve body opening assisting force acts in the direction of assisting the driving force of the actuator necessary for opening the second valve body. As described above, when the first valve element is “open” and the second valve element is “closed”, the second valve element opening assisting force is generated, so that the actuator necessary for opening the second valve element is obtained. It is possible to reduce the driving force and suppress an increase in the size of the actuator.

  In this case, in the first fuel discharge passage, the first flow passage restriction portion is located downstream of the joining portion of the flow passage connecting the first fuel discharge passage and the pressure introduction chamber and the first fuel discharge passage. Is preferably provided. According to this, when the first valve body of the first control valve is “open”, a large differential pressure is generated between the both sides of the first flow restrictor due to the presence of the fuel flow in the first fuel discharge passage. obtain. Thereby, the pressure in the first back pressure chamber (≈pressure in the pressure introduction chamber) can be increased to the vicinity of the pressure (control pressure) in the control chamber. As a result, the second valve body opening assisting force becomes sufficiently large, and the actuator driving force required for opening the second valve body can be further reduced.

  Thus, when the 1st flow-path restriction | limiting part is provided, it is preferable to make the outer diameter of the said piston and the valve-seat diameter of a said 2nd valve body equal. As described above, when the first valve body is “open” and the second valve body is “closed”, the pressure in the pressure introduction chamber≈the pressure in the control chamber = the pressure in the second valve body housing chamber is established. Therefore, when the outer diameter of the piston is equal to the valve seat diameter of the second valve body as in the above configuration, the force in the valve opening direction that the second valve body receives due to the pressure in the pressure introducing chamber (= the second valve body). The valve opening assisting force) and the force in the valve closing direction that the second valve body receives due to the pressure in the second valve body housing chamber can be made substantially equal. As a result, the actuator driving force required for opening the second valve body can be greatly reduced.

  Moreover, in the fuel injection control device according to the present invention, it is preferable that a second flow restrictor is provided between the control chamber and the second valve body storage chamber in the second fuel discharge path. . According to this, when the second valve body of the second control valve is “open”, a large differential pressure is generated between the both sides of the second flow restrictor due to the presence of the fuel flow in the second fuel discharge passage. obtain. Thereby, the pressure in the second valve body housing chamber can be lowered to substantially the atmospheric pressure.

  That is, after opening the second valve body of the second control valve, the magnitude of the force in the valve closing direction that the second valve body receives due to the pressure in the second valve body housing chamber decreases, while the second The magnitude of the valve opening assisting force is maintained. As a result, the lift amount of the second valve body can be increased to the maximum value by the second valve body opening assist force without assist by the pressing force by the actuator.

  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. The first and second control valves 43 and 44 are provided.

  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, regardless of the type of valve, the open state is referred to as "open", the closed state is referred to as "closed", and the transition from "open" to "closed" is referred to as "valve closed" The transition from “closed” to “open” may be referred to as “valve open”.

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 45 that constantly urges the needle valve 42 in the valve closing direction is disposed in the control chamber R2. When the biasing force (force in the valve closing direction) of the coil spring 45 is F3, the upper end side of the needle valve 42 receives the force (F2 + F3) in the valve closing direction as a whole. The coil spring 45 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 a range equal to or lower than the injection pressure Pc by opening / closing control of the first and second control valves 43 and 44. When the control pressure Pcntl is reduced from the injection pressure Pc to a certain pressure lower than the injection pressure Pc (hereinafter referred to as “needle valve opening pressure Py”), the needle valve 42 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 first and second control valves 43 and 44 will be described with reference to FIG. 2 which is an enlarged view of the first and second control valves 43 and 44. First, the first control valve 43 will be described.

  The first control valve 43 includes a hemispherical first valve body 43a that divides the second predetermined space into a first valve body accommodation chamber R3 and a first back pressure chamber R4, and a valve opening direction of the first valve body 43a. And an actuator 43b that is driven in the downward direction in FIG. The first valve body 43a and the actuator 43b are arranged coaxially with respect to the axial direction of the second predetermined space.

  The first valve body storage chamber R3 communicates with the control chamber R2 through the flow path C2, and the pressure in the first valve body storage chamber R3 is always equal to the control pressure Pcntl. The first back pressure chamber R4 communicates with the fuel tank T through a flow path C3 in which a first discharge orifice Z1 (constant opening area) is interposed. Here, the flow path C2, the first valve body accommodating chamber R3, the first back pressure chamber R4, and the flow path C3 correspond to the “first fuel discharge path” that discharges fuel from the control chamber R2.

  The first valve element 43a is movably accommodated in the first valve element accommodating chamber R3, and the position (vertical position) of the first valve element 43a is adjusted according to the driving force of the actuator 43b. It is like that. A state in which the first valve body 43a (the spherical surface portion thereof) is in contact with a valve seat portion (conical portion) 41c of the body 41 formed on the upper end side of the first valve body housing chamber R3 (valve closed state, FIG. 2), the first valve body housing chamber R3 and the first back pressure chamber R4 are blocked, and the “first fuel discharge path” is blocked. In this closed state, fuel is not discharged from the control chamber R2 via the first fuel discharge path. The lift amount of the first valve body 43a (first valve body lift amount Lv1) means the downward movement amount (downward amount) of the first valve body 43a from this state.

  On the other hand, when the first valve body 43a moves downward (lowers) from the valve-closed state and is separated from the valve seat portion 41c, the first valve body housing chamber R3 and the first back pressure chamber R4 communicate with each other as “first”. The "fuel discharge passage" is opened. In this state (valve open state, first valve body lift amount Lv1> 0), fuel is discharged from the control chamber R2 to the fuel tank T through the “first fuel discharge passage”. That is, if the flow rate passing through the discharge orifice Z1 is referred to as “first outflow rate Qout1,” the first outflow rate Qout1 = 0 when the first valve body 43a is “closed”, and the first valve body 43a is “ In the “open” state, the first outflow rate Qout1> 0.

  In this example, the actuator 43b is composed of a piezo element (piezoelectric / electrostrictive element), and the rod 43c is configured to extend in the vertical direction in accordance with the drive voltage V adjusted and supplied in accordance with an instruction from the ECU 50. The first valve body 43a is pressed through the valve in the valve opening direction (downward). For this actuator 43b, the driving voltage V, the driving force of the actuator 43b (hereinafter also referred to as “actuator generating force”), and the amount of extension of the actuator 43b (extension in the vertical direction from the state shown in FIGS. The amount, that is, equal to the first valve body lift amount Lv1 (hereinafter also referred to as “actuator lift amount”) is as shown in FIG. That is, when the driving voltage V is constant, the amount of actuator generated decreases as the actuator lift increases. In order to increase the actuator generation force with a constant actuator lift, it is necessary to increase the drive voltage V.

  In addition, a coil spring 43d that constantly biases the first valve body 43a in the valve closing direction is disposed in the first valve body housing chamber R3. In this example, the biasing force of the coil spring 43d is a value F4 (constant). The coil spring 43d is provided only for reliably closing the first valve body 43a when the actuator 43b is not in operation (drive voltage V = 0). Therefore, the biasing force F4 is very small.

  When the first valve body 43a is “closed”, the first outflow flow rate Qout1 = 0 and the pressure in the first back pressure chamber R4 is equal to the atmospheric pressure, while the pressure in the first valve body housing chamber R3 is Equal to the control pressure Pcntl. Therefore, if the valve seat diameter (seat diameter) of the valve seat portion 41c is D3, the force F5 required to open the first valve body 43a can be expressed by the following equation (5). That is, when the actuator generating force exceeds the value F5, the first valve body 43a is opened.

F5 = (π / 4) · D3 ² · Pcntl + F4 (5)

  Next, the second control valve 44 will be described. The second control valve 44 includes a hemispherical second valve body 44a that divides the second predetermined space into a second valve body accommodating chamber R5 and a second back pressure chamber R6, and the second predetermined space into the second back space. A piston 44b that is divided into a pressure chamber R6 and a pressure introduction chamber R7 is provided. The second valve body 44a and the piston 44b are arranged coaxially with respect to the axial direction of the second predetermined space (that is, the first valve body 43a and the actuator 43b).

  The second valve body storage chamber R5 communicates with the control chamber R2 through a flow path C4 in which a second discharge orifice Z2 (constant opening area) is interposed. The second back pressure chamber R6 communicates with the flow path C3 downstream of the first discharge orifice Z1 (accordingly, with the fuel tank T) through the flow path C5. Accordingly, the pressure in the second back pressure chamber R6 is always substantially equal to the atmospheric pressure. The pressure introducing chamber R7 communicates with the first back pressure chamber R4 through the flow path C6. Therefore, the pressure in the pressure introducing chamber R7 is always equal to the pressure in the first back pressure chamber R4. Here, the flow path C4, the second valve body storage chamber R5, the second back pressure chamber R6, the flow path C5, and the flow path C3 correspond to the “second fuel discharge path” that discharges fuel from the control chamber R2. is doing.

  Piston 44b is comprised from the large diameter part 44b1, the small diameter part 44b2, and the small diameter part 44b3 which are mutually arrange | positioned coaxially. The large diameter portion 44b1 partitions the second back pressure chamber R6 and the pressure introduction chamber R7. The small-diameter portion 44b2 partitions the pressure introduction chamber R7 and the first valve body housing chamber R3, and the distal end portion (upper end portion) thereof is exposed in the first valve body housing chamber R3 and the first valve body 43a (of the It is opposed to the flat portion). The distal end portion (lower end portion) of the small diameter portion 44b3 is always in contact with the second valve body 44a (the spherical portion thereof).

  The second valve element 44a is accommodated in the second valve element accommodating chamber R4 so as to be movable. The position (vertical position) of the second valve body 44a is adjusted by being pressed in the valve opening direction via the piston 44b by the first valve body 43a in the valve open state, as will be described later. It has become. A state in which the second valve body 44a (the spherical surface portion thereof) is in contact with a valve seat portion (conical shape portion) 41d of the body 41 formed on the upper end side of the second valve body housing chamber R5 (valve closed state, FIG. 2), the second valve body accommodating chamber R5 and the first back pressure chamber R6 are blocked, and the “second fuel discharge path” is blocked. In this valve closed state, fuel is not discharged from the control chamber R2 through the second fuel discharge path. The lift amount (second valve body lift amount Lv2) of the second valve body 44a means the downward movement amount (downward amount) of the second valve body 44a from this state.

  On the other hand, when the second valve body 44a moves (lowers) downward from the valve closed state and is separated from the valve seat portion 41d, the second valve body housing chamber R5 and the second back pressure chamber R6 communicate with each other as “second”. The "fuel discharge passage" is opened. In this state (valve open state, second valve body lift amount Lv2> 0), fuel is discharged from the control chamber R2 to the fuel tank T through the “second fuel discharge passage”. That is, if the flow rate passing through the discharge orifice Z2 is referred to as “second outflow rate Qout2,” the second outflow rate Qout2 = 0 when the second valve body 44a is “closed”, and the second valve body 44a is “ In the “open” state, the second outflow rate Qout2> 0.

  In addition, a coil spring 44c that constantly biases the second valve body 44a in the valve closing direction is disposed in the second valve body housing chamber R4. In this example, the urging force of the coil spring 44c is a value F6 (constant). The coil spring 44c is provided only for reliably closing the second valve body 44a when the actuator 43b is not operated (drive voltage V = 0). Therefore, as with the urging force F4, the urging force F6 is very small.

  As shown in FIG. 2, when both the first and second valve bodies 43a, 44a are “closed”, the tip of the small diameter portion 44b2 of the piston 44b and the first valve body 43a (the flat portion thereof) are in the vertical direction. At a distance z. Therefore, when the first valve body lift amount Lv1 reaches the value z, the first valve body 43a (the flat surface portion thereof) comes into contact with the distal end portion of the small diameter portion 44b2. When the first valve body lift amount Lv1 further increases, the second valve body 44a is pressed by the piston 44b (that is, the first valve body 43a) to open the valve. Thus, the 1st valve body 43a is driven by the actuator 43b, and the 2nd valve body 44a is driven by the press of the 1st valve body 43a in a valve opening state.

  When the second valve body 44a is “closed”, the second outflow flow rate Qout2 = 0 and the pressure in the second valve body housing chamber R5 is equal to the control pressure Pcntl, while the pressure in the second back pressure chamber R6 is Is equal to atmospheric pressure. Therefore, if the valve seat diameter (seat diameter) of the valve seat portion 41d is D4, the force F7 required to open the second valve body 44a can be expressed by the following equation (6). That is, when the pressing force of the piston 44b against the second valve body 44a exceeds the value F7, the second valve body 44a is opened. In this example, the valve seat diameter D4 is equal to the outer diameter D5 of the large diameter portion 44b1 of the piston 44b.

F7 = (π / 4) · D4 ² · Pcntl + F6 (6)

  The control chamber R2 communicates with the fuel supply path C1 through a fuel inflow path C7 in which an inflow orifice Z3 (constant opening area) is interposed. Accordingly, the fuel flows from the fuel supply passage C1 into the control chamber R2 through the fuel inflow passage C7 in accordance with the differential pressure between the both sides of the inflow orifice Z3 (hence, the differential pressure between the injection pressure Pc and the control pressure Pcntl). ing. Hereinafter, the flow rate passing through the inflow orifice Z3 is referred to as “inflow rate Qin”.

  With the above configuration, the drive voltage V supplied to the actuator 43b is controlled to open and close the first and second control valves 43 and 44 (specifically, open and close the first and second valve bodies 43a and 44a). As a result, the first and second outflow flows Qout1, Qout2 and the flow rate Qin are adjusted, and the control pressure Pcntl is adjusted.

  Next, the relationship among the drive voltage V, the actuator generating force, the actuator lift amount, and the open / closed states of the first and second valve bodies 43a and 44a will be described with reference to FIG. 3 and FIGS. FIG. 3 is a diagram corresponding to FIG. 22 described in the section of the disclosure of the invention, and a broken line oabc′′d ′ in FIG. 3 is a solid line oabcc− in FIG. d (that is, when the conventional apparatus shown in FIG. 18 or the like is applied), and the solid line in FIG. 3 corresponds to the case where this example is applied. 4-8, “open” indicates that the internal pressure is equal to the atmospheric pressure, and “fine dots” indicates that the internal pressure is equal to the control pressure Pcntl. Yes.

  First, as shown at a point o in FIG. 3, when the drive voltage V = 0, the actuator generation amount and the actuator lift amount are both “0”, so that the first and second valve bodies are shown in FIG. 43a and 44a are both kept closed. Therefore, in this case, the first and second outflow rates Qout1, Qout2 = 0. Therefore, fuel does not flow out from the control chamber R2. In the state shown in FIG. 4, the pressure in the first and second valve body accommodating chambers R3 and R5 is equal to the control pressure Pcntl, and the pressure in the first and second back pressure chambers R4 and R6 is equal to the atmospheric pressure.

  In this state, as indicated by a point a in FIG. 3, the driving voltage V is changed from “0” to the force F5 required to open the first valve element 43a when the actuator lift amount = 0. When the value increases stepwise to the value V1 required to obtain (see the above equation (5)), as shown in FIG. 5, the first valve element 43a opens (that is, the actuator lift amount is “0”). To increase). As a result, a differential pressure is generated between both sides of the first discharge orifice Z1 due to the generation of the first outflow flow rate Qout1 (> 0), and the pressure in the first back pressure chamber R4 as shown in FIG. , And the pressure in the pressure introduction chamber R7 increases from the atmospheric pressure to the control pressure Pcntl (near).

  As a result, the force that the first valve body 43a receives in the valve opening direction due to the pressure in the first back pressure chamber R4 increases, so the first valve body lift amount Lv1 (= actuator lift amount) increases from “0”. Along with this, the force generated by the actuator decreases. When the actuator lift amount reaches the value z as shown at point b in FIG. 3, the first valve body 43a contacts the piston 44b (the small diameter portion b2 thereof), and the increase in the actuator lift amount stops. As a result, as shown in FIG. 6, the first valve body 43 a is kept “open” and the second valve body 44 a is kept “closed”.

  That is, in the state shown in FIG. 6, the first outflow rate Qout1> 0 and the second outflow rate Qout2 = 0, and the fuel flows out from the control chamber R2 through the “first fuel discharge path”. In this state, the pressure in the first and second valve body accommodating chambers R3 and R5, and the pressure in the first back pressure chamber R4 and the pressure introduction chamber R7 are equal to the control pressure Pcntl, and the pressure in the second back pressure chamber R6 is The pressure is equal to atmospheric pressure.

  As described above, after the opening of the first valve body 43a, the pressure in the first back pressure chamber R4 increases to the control pressure Pcntl by the action of the first discharge orifice Z1, thereby increasing the drive voltage V from V1. The first valve body lift amount Lv1 (= actuator lift amount) can be increased to the value z without any problem.

  Subsequently, in this state, as shown at a point c in FIG. 3, the actuator voltage is a force necessary to open the second valve body 44a from the value V1 and the actuator lift amount = z. When stepwise increases to the value V2 required to set F8, the second valve body 44a opens (that is, the actuator lift amount increases from the value z) as shown in FIG.

  Here, the force F8 will be described. As shown in FIG. 6, when the first valve body 43a is “open” and the second valve body 44a is “closed”, the pressure in the first valve body housing chamber R3 and the pressure in the pressure introduction chamber R7 are Control pressure Pcntl. On the other hand, the pressure in the second back pressure chamber R6 is maintained at atmospheric pressure. Accordingly, a force F9 (= “second valve body opening assist force”) expressed by the following equation (7) acts on the piston 44b in the valve opening direction (downward direction) of the second valve body 44b. is doing.

F9 = (π / 4) · D5 ² · Pcntl (7)

  On the other hand, as described above, D4 = D5. From the above, the force F8 = F7−F9 = the urging force F6 (= small) of the coil spring 44c is established. Therefore, the increase amount f (see FIG. 3) of the actuator generating force necessary for opening the second valve body 44a is also small. This increase amount f is sufficiently smaller than the increase amount F (see FIG. 3) of the actuator generation force required for opening the second valve body 44a when the conventional apparatus shown in FIG. 18 and the like is applied.

  This is because the pressure in the pressure introduction chamber R7 rises to the control pressure Pcntl when the first valve body 43a is “open” by the action of the first discharge orifice Z1, and the pressure in the pressure introduction chamber R7 (= control pressure). Pcntl) is based on the fact that the force F9 (see the equation (7)) received by the piston 44b acts in the direction of assisting the actuator generating force necessary for opening the second valve body 44a. As a result, the load of the actuator 43b required for opening the second valve body 44a can be significantly reduced as compared with the case where the conventional device is applied, and the drive voltage V2 is applied to the conventional device. In this case, the driving voltage can be made sufficiently lower than the driving voltage V2 ′ (see FIG. 3).

  When the second valve body 44a is opened, a differential pressure is generated between both sides of the second discharge orifice Z2 due to the generation of the second outflow flow rate Qout2 (> 0), and as shown in FIG. The pressure in the valve body storage chamber R5 decreases from the control pressure Pcntl to the atmospheric pressure.

  As a result, the force that the second valve element 44a receives in the valve closing direction due to the pressure in the second valve element accommodating chamber R5 decreases, so the second valve element lift amount Lv2 increases from “0” (ie, The actuator lift increases from the value z), and the actuator generation force decreases accordingly. As shown at a point d in FIG. 3, when the actuator lift amount (= first valve body lift amount Lv1) reaches the maximum value, the increase in the actuator lift amount stops.

  On the other hand, receiving the force F9, the piston 44b and the second valve body 44a continue to descend (that is, the tip of the small diameter portion 44b2 is separated from the first valve body 43a), and the second valve body lift amount is maximum. When the value is reached, the lowering of the piston 44b and the second valve body 44a stops. As a result, as shown in FIG. 8, the first and second valve bodies 43a and 43b are both kept open. In this example, the maximum value of the actuator lift amount (= first valve body lift amount Lv1) corresponds to the state in which the coil spring 43d is in close contact, and the maximum value of the second valve body lift amount is in close contact with the coil spring 44c. Corresponds to the state.

  That is, in the state shown in FIG. 8, the first outflow rate Qout1> 0 and the second outflow rate Qout2> 0, and the fuel flows out from the control chamber R2 through the “first fuel discharge path” and the “second fuel discharge path”. To do. In this state, the pressure in the first valve body storage chamber R3, the pressure in the first back pressure chamber R4 and the pressure introduction chamber R7 are equal to the control pressure Pcntl, and the second valve body storage chamber R5 and the second back pressure chamber The pressure in R6 is equal to atmospheric pressure.

  Thus, after the valve opening of the second valve element 44a, the drive voltage V is increased from V2 by the pressure in the second valve element accommodating chamber R5 being reduced to the atmospheric pressure by the action of the second discharge orifice Z2. The second valve body lift amount Lv2 can be increased to the maximum value by the force F9.

  Then, in the state shown in FIG. 8 (corresponding to the point d in FIG. 3), when the drive voltage V is changed stepwise from the value V2 to “0”, the actuator generation amount becomes “0”. Accordingly, the first and second valve bodies 43a and 44a are closed by the urging forces F4 and F6 of the coil springs 43d and 44c. As a result, when the first and second discharge flow rates Qout1 and Qout2 become “0”, the pressure in the first back pressure chamber R4 decreases from the control pressure Pcntl to the atmospheric pressure, and the second valve body accommodating chamber R5. The internal pressure increases from the atmospheric pressure to the control pressure Pcntl. That is, as shown in FIG. 4, the first and second valve bodies 43a and 44a are again maintained in the “closed” state.

  Next, an example of the operation of the fuel injection control device 10 will be described with reference to FIG. Prior to time t1, the drive voltage V = 0. Accordingly, as shown in FIG. 4, the first and second valve body lift amounts Lv1, Lv2 = 0, and the “first fuel discharge path” and the “second fuel discharge path” are blocked. That is, the first and second outflow flows Qout1, Qout2 = 0. Further, 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 kept “closed”. 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 by an instruction from the ECU 50 at time t1, the first valve body 43a is opened at time t1 (immediately after) and “first The fuel discharge path is opened (see FIG. 5), and after time t1, fuel is discharged from the control chamber R2 only through the “first fuel discharge path” (Qout1> 0), and the control pressure Pcntl is the injection pressure Pc. (See FIG. 6). Accordingly, fuel flows from the fuel supply path C1 into the control chamber R2 through the fuel inflow path C7 (Qin> 0). As a result, the control pressure Pcntl decreases from the injection pressure Pc at a speed corresponding to the difference between the first outflow rate Qout1 and the inflow rate Qin (= Qout1-Qin).

  When the control pressure Pcntl that decreases after time t1 reaches the needle valve opening pressure Py expressed by the above equation (4) at time t2, the needle valve 42 opens, and 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 fuel volume decreasing rate (= Qout1-Qin) in the control chamber R2. (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 changes 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 45. 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 45 is very small, the urging force F3 of the coil spring 45 (accordingly, the spring force equivalent pressure component Px) is treated as being constant without depending on the needle valve lift amount.

  When the drive voltage V is changed stepwise from the value V1 to the above-described value V2 according to an instruction from the ECU 50 at time t4, the second valve body 44a is opened at time t4 (immediately after), and “first fuel” In addition to the “discharge path”, the “second fuel discharge path” is opened (see FIG. 7), and after time t4, the fuel is discharged from the control chamber R2 through the “first fuel discharge path” and the “second fuel discharge path”. As a result, the control pressure Pcntl decreases from the injection pressure Pc (see FIG. 8). Accordingly, fuel flows from the fuel supply path C1 into the control chamber R2 through the fuel inflow path C7 (Qin> 0).

  As a result, the control pressure Pcntl decreases from the injection pressure Pc at a speed corresponding to the difference between the sum of the first and second outflow flow rates Qout1, Qout2 and the inflow flow rate Qin (= Qout1 + Qout2-Qin). That is, the needle valve rises at a needle valve ascent rate (hereinafter referred to as “second ascent rate”) greater than the first ascent rate (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 first and second valve body lift amounts Lv1, Lv2 return to “0” after time t5. . That is, both the “first fuel discharge path” and the “second fuel discharge path” are blocked (Qout1, Qout2 = 0), and the fuel discharge from the control chamber R2 is stopped. On the other hand, the inflow of fuel into the control chamber R2 through the fuel inflow passage C7 is still continued (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 C7 (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, the first and second fuel discharge paths are provided as the flow paths for discharging the fuel from the control chamber R2 located on the back surface of the injector 40. The first and second control valves 43 and 44 are interposed in the first and second fuel discharge paths, respectively. The first valve body 43a of the first control valve 43 is driven by an actuator 43b, and the second valve body 44a of the second control valve 44 is pressed by the first valve body 43a in the “open” state (ie, the piston 44b Driven).

  The first valve body 43a is opened by adjusting the drive voltage V of the actuator 43b to V1, and the second valve body is switched by switching the drive voltage V from V1 to V2 (> V1) while the needle valve 42 is raised. 44a is also opened. Thereby, 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.

  When the first valve body 43a is “open” and the second valve body 44a is “closed”, the pressure in the pressure introduction chamber R7 rises to the control pressure Pcntl by the action of the first discharge orifice Z1, The force F9 (see the equation (7)) received by the piston 44b due to the pressure in the introduction chamber R7 (= control pressure Pcntl) acts in the direction of assisting the actuator generating force necessary to open the second valve body 44a; In addition, due to the fact that the outer diameter D5 of the large diameter portion 44b2 of the piston 44b is equal to the valve seat diameter D4 of the second valve body 44a, the driving force of the actuator necessary for opening the second valve body 44a is coiled. The biasing force F6 (= small) of the spring 44c can be made equal.

  As a result, the drive voltage V2 can also be made sufficiently smaller than the drive voltage V2 '(see FIG. 3) when the conventional device is applied. That is, compared with the conventional device, the actuator driving force required for opening the second valve body 44a can be reduced, and the size of the actuator 43b can be prevented from increasing.

  In addition, after the second valve element 44a is opened, the drive voltage V is increased from V2 by reducing the pressure in the second valve element accommodating chamber R5 to the atmospheric pressure by the action of the second discharge orifice Z2. The second valve body lift amount Lv2 can be increased to the maximum value by the force F9.

  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. 9, the drive voltage V is set to V1, the needle valve 42 is opened, and the drive voltage V is switched from V1 to V2 while the needle valve 42 is rising. Thus, the needle valve ascent speed is switched in two stages from the first ascent speed to the second ascent speed (> first ascent speed). As shown in FIG. 10, the drive voltage V is set to V1. The needle valve 42 may be kept open at the first rising speed while the needle valve 42 is opened, and the driving voltage V is maintained at V1 thereafter.

  Similarly, as shown in FIG. 11, the needle valve 42 is opened by setting the drive voltage V to V2, and thereafter the needle voltage rises by maintaining the drive voltage V at V2, thereby increasing the needle valve. The speed may be maintained at the second ascent rate.

  In general, the injection pressure Pc is changed according to the operating state. On the other hand, the force F5 required to open the first valve body 43a expressed by the above equation (5) depends on the control pressure Pcntl (= injection pressure Pc) and increases as the injection pressure Pc increases. Therefore, in general, it is preferable to set the drive voltages V1 and V2 to larger values as the injection pressure Pc increases.

  That is, in this case, as shown in FIG. 12, when the injection pressure Pc is high, the drive voltages V1 and V2 are set to higher values for high pressure (see FIG. 12). As a result, when the drive voltage V is changed from “0” → V1 → V2, the relationship between the actuator generation force and the actuator lift amount changes as indicated by the solid line oabc. Points a and c correspond to the opening of the first and second valve bodies 43a and 44a, respectively. The value f is equal to the urging force F6 of the coil spring 44c as in FIG.

  On the other hand, when the injection pressure Pc is low, the drive voltages V1 and V2 are set to lower values for low pressure (not shown). As a result, when the drive voltage V is changed from “0” → V1 → V2, the relationship between the actuator generated force and the actuator lift amount changes as indicated by a broken line o-a′-b′-c ′. Points a 'and c' correspond to the opening of the first and second valve bodies 43a and 44a, respectively.

  On the other hand, let us consider a case where the drive voltages V1 and V2 are made constant without depending on the injection pressure Pc. In this case, it is necessary to set the drive voltages V1 and V2 to large values for high pressure as shown in FIG. 12, so that the first valve body 43a can be opened even when the injection pressure Pc is high. . However, in this case, in FIG. 12, the point c 'is located in the lower left region of the straight line passing through the points a and b corresponding to the drive voltage V1. This means that when the injection pressure Pc is low, setting the drive voltage V to V1 opens not only the first valve body 43a but also the second valve body 44a.

  In order to solve such a problem, in FIG. 12, the point c 'may be moved into the upper right region from the straight line passing through the points a and b corresponding to the drive voltage V1. One technique for this is to shift the point b '(and hence the point c') to the right as shown in FIG.

  In order to shift the point b ′ to the right, for example, when the first valve body 43a is “open” and the second valve body 44a is “closed”, the upward acting on the actuator 43b with respect to the change in the injection pressure Pc is performed. The amount of change in force (= actuator generated force) may be reduced. Here, as shown in FIG. 14, when the first valve element 43a is “open” and the second valve element 44a is “closed”, the upward force acting on the actuator 43b is the upward force (= control) The sum of the pressure Pcntl × “the pressure receiving area of the lower surface of the rod 43c” (see white arrow) and the upward force F4 (constant, see black arrow) by the coil spring 43d. Therefore, in order to reduce the amount of change in the upward force acting on the actuator 43b with respect to the change in the injection pressure Pc, it is conceivable to reduce the outer diameter of the rod 43c.

  Further, as another method for moving the point c ′ into the upper right region with respect to the straight line passing through the points a and b corresponding to the driving voltage V1, as shown in FIG. It is also conceivable to increase the urging force F6 of 44c. Further, in order to move the point c ′ into the upper right region with respect to the straight line passing through the points a and b corresponding to the driving voltage V1, the outer diameter of the rod 43c is reduced and the urging force F6 of the coil spring 44c is set to be smaller. You may enlarge it.

  In the above embodiment, the member (small diameter portion 44b2) that partitions the first valve body housing chamber R3 and the pressure introduction chamber R7 is integrally provided on the piston 44b side (see FIG. 2). As shown in FIG. 16, a member (43a2) that partitions the first valve body housing chamber R3 and the pressure introduction chamber R7 may be integrally provided on the first valve body 43a side. In this case, for example, by making the outer diameter of the member 43a2 equal to the valve seat diameter D3 of the first valve body 43a, the force F5 required to open the first valve body 43a is expressed by the above equation (5). Instead of the value to be applied, it can be set to a value equal to the urging force F4 (= small) of the coil spring 43d. Thereby, the load of the actuator 43b required for valve opening of the 1st valve body 43a can be reduced significantly.

  In the above embodiment, a piezoelectric element is used as the actuator 43b. However, other types of actuators may be used.

  In the above embodiment, the outer diameter D5 of the large diameter portion 44b2 of the piston 44b is equal to the valve seat diameter D4 of the second valve body 44a, but the outer diameter D5 may be smaller or larger than the valve seat diameter D4. .

  In addition, in the above-described embodiment, the first and second discharge orifices Z1 and Z2 are provided, but either one or both may be omitted. Moreover, although the 1st valve body 43a, piston 44b, and the 2nd valve body 44a are arrange | positioned coaxially, these do not need to be arrange | positioned coaxially.

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 1st, 2nd control valve shown in FIG. 2 is a graph showing an example of a relationship between a drive voltage, an actuator generation force, and an actuator lift amount and a transition of the relationship in the actuator shown in FIG. It is a figure which shows the pressure distribution of each chamber of a 1st, 2nd control valve in case a 1st, 2nd valve body is both "closed." It is a figure which shows the pressure distribution of each chamber of the 1st, 2nd control valve immediately after valve opening of a 1st valve body. It is a figure which shows the pressure distribution of each chamber of a 1st, 2nd control valve in case a 1st valve body is "open" and a 2nd valve body is "closed." It is a figure which shows the pressure distribution of each chamber of the 1st, 2nd control valve immediately after valve opening of a 2nd valve body. It is a figure which shows the pressure distribution of each chamber of a 1st, 2nd control valve in case a 1st, 2nd valve body is both "open". 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. 6 is a time chart showing another example of changes in each physical quantity during operation of the fuel injection control device shown in FIG. 1. 6 is a time chart showing another example of changes in each physical quantity during operation of the fuel injection control device shown in FIG. 1. It is a figure for demonstrating that the relationship between a drive voltage, an actuator generating force, and an actuator lift amount changes according to injection pressure. It is the figure which showed the case where point c 'was shifted to the right by making the outer diameter of a rod small. It is the figure which showed the upward force which acts on an actuator when a 1st valve body is "open" and a 2nd valve body is "closed." It is the figure which showed the case where point c 'was shifted to the right by enlarging the urging | biasing force of a coil spring. It is an enlarged view of the 1st, 2nd control valve of the fuel-injection control apparatus which concerns on the modification of embodiment of this invention. It is a schematic block diagram of the conventional fuel-injection control apparatus. In the conventional fuel injection control device, when the first and second valve bodies are both “closed”, it is a schematic configuration diagram around the first and second valve bodies. FIG. 19 is a schematic configuration diagram around the first and second valve bodies when the first valve body is “open” and the second valve body is “closed” in the apparatus shown in FIG. 18. FIG. 19 is a schematic configuration diagram around the first and second valve bodies when both the first and second valve bodies are “open” in the apparatus shown in FIG. 18. FIG. 19 is a graph showing a relationship among drive voltage, actuator generation force, and actuator lift amount in the actuator shown in FIG. 18. FIG. 19 is a graph showing an example of transition of the relationship among the drive voltage, the actuator generation force, and the actuator lift amount in the actuator shown in FIG. 18.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Fuel pump, 30 ... Common rail, 40 ... Injector, 41 ... Body, 41a ... Injection hole, 42 ... Needle valve, 43 ... First control valve, 43a ... First valve body, 43b ... Actuator, 43c ... Rod, 43d ... Coil spring, 44 ... Second control valve, 44a ... Second valve element, 44b ... Piston, 44b1 ... Large diameter part 43c, 44b2, 44b3 ... Small diameter part, 44c ... Coil spring, 50 ... ECU, C1 ... Fuel supply path C7: Fuel inflow path, Z1: First discharge orifice, Z2: Second discharge orifice, Z3: Inflow orifice

Claims (5)

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 first fuel discharge path for discharging fuel from the control chamber to a fuel tank;
A first control valve that is interposed in the first fuel discharge path and communicates and blocks the first fuel discharge path;
A second fuel discharge path for discharging fuel from the control chamber to the fuel tank;
A second control valve that is interposed in the second fuel discharge path and communicates and blocks the second fuel discharge path;
A fuel injection control device that controls the first and second control valves and controls the control pressure to adjust the position of the needle valve to perform fuel injection control,
The first control valve is
A first valve body storage chamber communicating with the control chamber;
A first back pressure chamber communicating with the fuel tank;
A first valve body that is movably housed in the first valve body housing chamber and communicates and blocks the first valve body housing chamber and the first back pressure chamber;
An actuator capable of generating a driving force for pressing the first back pressure chamber side portion of the first valve body in the valve opening direction and adjusting a lift amount in the valve opening direction from the closed state of the first valve body. When,
The first valve body storage chamber and the first back pressure chamber constitute a part of the first fuel discharge path,
The second control valve is
A second valve body accommodating chamber communicating with the control chamber;
A second back pressure chamber communicating with the fuel tank;
A second valve body that is movably housed in the second valve body housing chamber and communicates and blocks the second valve body housing chamber and the second back pressure chamber;
A pressure introducing chamber in communication with the first back pressure chamber;
A piston partitioning the second back pressure chamber and the pressure introducing chamber;
The second valve body storage chamber and the second back pressure chamber constitute a part of the second fuel discharge path,
The piston is
One end of the first valve body faces the second back pressure chamber and the other end faces the pressure introduction chamber and receives a force in the direction from the other end to the one end side due to the pressure in the pressure introduction chamber. When the lift amount is greater than or equal to a predetermined amount, the other end side comes into contact with the first valve body and is pressed against the first valve body in accordance with an increase in the lift amount of the first valve body. Arranged and configured so that it can move in the direction of one end side, and the one end side comes into contact with the second back pressure chamber side portion of the second valve body to press the second valve body in the valve opening direction. Fuel injection control device. The fuel injection control device according to claim 1,
In the first fuel discharge passage, a first flow passage restricting portion is provided downstream of the joining portion between the flow passage communicating the first fuel discharge passage and the pressure introducing chamber and the first fuel discharge passage. Fuel injection control device. The fuel injection control device according to claim 2,
A fuel injection control device in which an outer diameter of the piston and a valve seat diameter of the second valve body are equal. The fuel injection control device according to any one of claims 1 to 3,
A fuel injection control device in which a second flow restrictor is provided between the control chamber and the second valve body storage chamber in the second fuel discharge path. The fuel injection control device according to any one of claims 1 to 4,
A fuel injection control device in which the first valve body, the piston, and the second valve body are arranged coaxially.

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