JP4535027B2 - Fuel injection device and differential pressure valve used therefor - Google Patents

Description

  The present invention relates to a fuel injection device for injecting fuel into an internal combustion engine and a differential pressure valve used therefor.

  A conventional fuel injection device includes an injector that injects high-pressure fuel into an internal combustion engine. This injector has a nozzle that opens and closes the nozzle hole with a needle, and the needle is biased toward the valve closing direction by the fuel pressure in the control chamber, and the pressure in the control chamber is controlled by the control valve to control the opening and closing operation of the nozzle. It is like that.

  Further, the expansion / contraction displacement of the piezo stack is transmitted to the control valve via the hydraulic drive transmission unit, so that the control valve is driven. The liquid chamber of the drive transmission unit is filled with fuel as a working fluid, and when the piezo stack extends, the pressure of the liquid chamber rises, and the piston is displaced by the pressure to drive the control valve. It has become. The piezo stack and the drive transmission unit are arranged in a low pressure space in the injector.

  In such a fuel injection device, when the gas runs out, air enters the low-pressure space in the injector, and eventually air enters the liquid chamber of the drive transmission unit. The problem arises that the engine cannot be operated and the internal combustion engine cannot be started.

By the way, in Patent Document 1, in the fuel injection device as described above, a part of the low-pressure fuel pumped from the low-pressure pump (specifically, fuel having a pressure lower than the injection pressure) is transferred to the hydraulic drive transmission unit. Is supplied to the low-pressure space in the injector in which is disposed. According to this, since the air in the liquid chamber of the drive transmission unit is discharged by the fuel pumped from the low pressure pump, the internal combustion engine can be started even after the gas runs out.
JP 2005-507053 A

  However, in a general internal combustion engine, since the distance between the low pressure pump and the injector is long, in the fuel injection device described in Patent Document 1, piping for guiding the fuel from the low pressure pump to the low pressure space in the injector There was a problem that the handling of was complicated. Further, the pressure of the fuel pumped from the low pressure pump generally rises to a maximum of 1 MPa or more. Therefore, it is necessary to use a pipe made of metal or resin having a high strength as the pipe. Since the pipe has high rigidity, it is not easy to handle the pipe.

  Further, in the fuel injection device described in Patent Document 1, since fuel is continuously supplied from the low pressure pump to the return path even during normal operation, the fuel that is pumped from the low pressure pump to the low pressure side of the injector. The pressure-resistant structure must be able to withstand this pressure (for example, 1 MPa or more).

  In view of the above points, the present invention provides a fuel injection device that supplies fuel to a low-pressure space in which a drive transmission unit is disposed, and discharges air in a liquid chamber of the drive transmission unit, thereby simplifying the handling of piping. The purpose is to do.

  Further, the present invention provides a fuel injection apparatus in which fuel is supplied to a low pressure space in which a drive transmission unit is disposed, and air in a liquid chamber of the drive transmission unit is discharged. Another purpose is to lower.

  In the first feature of the present invention, the fuel pumped from the low pressure pump (20) is pressurized by the high pressure pump (22) and pumped to the pressure accumulator (23), and the high pressure stored in the pressure accumulator (23). Two pistons (1133, 1134) configured to inject fuel from the injector (10) and forming a liquid chamber (1135) in the middle are disposed in the low pressure space (112, 114) in the injector (10), A fuel injection device in which a back pressure valve (27) is disposed in a return path (26) for returning the fuel in the low pressure space (112, 114) to the fuel tank (21), and is located downstream of the high pressure pump (22). A filling path (29) for guiding the high-pressure fuel to a part upstream of the back pressure valve (27) in the return path (26) is provided.

  In this way, the air in the liquid chamber (1135) is discharged by the fuel supplied to the low pressure space (112, 114) via the filling path (29), so that the internal combustion engine is started even after the gas runs out. be able to. The filling path (29) communicates the downstream side of the high-pressure pump (22) and the upstream side of the back pressure valve (27) in the return path (26). The piping of the filling path (29) The length can be made shorter than the length of the pipe for guiding the fuel from the low-pressure pump in the fuel injection device described in Patent Document 1 to the low-pressure space in the injector, and therefore the piping is simplified. can do.

  In this case, a differential pressure valve (60, 553) for opening and closing the filling path (29) is provided, and the differential pressure valve (60, 553) is configured such that the pressure on the high pressure pump (22) side is higher than the pressure on the return path (26) side. The filling path (29) can be closed when it becomes higher than the predetermined differential pressure.

  In this way, it is possible to prevent the low pressure side of the injector from becoming a high pressure, so that the required pressure resistance performance on the low pressure side of the injector can be reduced.

  In this case, the differential pressure valve (553) can be incorporated into the safety valve (50) that opens the filling path (29) when the pressure on the high pressure pump (22) side becomes equal to or higher than the second predetermined pressure.

  In this way, in the case of a fuel injection device provided with a safety valve (50), it can be implemented without changing (adding) the routing of the return path (26).

  Moreover, the safety valve (50) in which the differential pressure valve (553) is incorporated can be assembled to the pressure accumulator (23).

  In this way, since the upstream portion of the accumulator (23) and the return path (26) are generally closer to the upstream side than the back pressure valve (27), the piping of the filling path (29) can be further routed. It can be simplified.

  Further, in the fuel injection device configured to control the pressure of the high pressure fuel in the accumulator (23) by controlling the amount of the high pressure fuel pumped from the high pressure pump (22), the start of the internal combustion engine is completed. Until it is determined, the pressure of the high-pressure fuel in the pressure accumulator (23) can be controlled so that the valve open state of the differential pressure valve (60, 553) is maintained.

  In this way, since the fuel is supplied to the liquid chamber (1135) through the filling path (29) until the start of the internal combustion engine is completed, the air in the liquid chamber (1135) is surely discharged and the gas is discharged. Even after the absence, the internal combustion engine can be reliably started.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a system diagram showing a piping configuration of the fuel injection device according to the first embodiment of the present invention.

  As shown in FIG. 1, the low pressure pump 20 sucks fuel from the fuel tank 21 and pumps it to the high pressure pump 22, and the high pressure pump 22 pressurizes the fuel pumped from the low pressure pump 20 and pumps it to the pressure accumulator 23. To do.

  In the substantially cylindrical accumulator 23, the high-pressure fuel pumped from the high-pressure pump 22 is accumulated. A plurality of injectors 10 (details will be described later) provided for each cylinder of an internal combustion engine (more specifically, a diesel engine) (not shown) are connected to the accumulator 23, and high pressure fuel accumulated in the accumulator 23 is supplied to each accumulator 23. The fuel is injected from the injector 10 into the corresponding cylinder. A pressure sensor 24 that detects the pressure of the fuel in the pressure accumulator 23 is disposed on one end side of the pressure accumulator 23.

  The electronic control unit (hereinafter referred to as ECU) 25 includes a known microcomputer including a CPU, a ROM, a RAM, and the like, and executes various processes stored in the microcomputer. The ECU 25 receives information such as the engine speed, the amount of depression of an accelerator pedal (not shown), and the output signal of the pressure sensor 24, and the ECU 25 opens the valve opening timing and valve opening of the injector 10 based on the information. Control the time. Moreover, ECU25 controls the pressure of the fuel in the pressure accumulator 23 to the predetermined | prescribed pressure calculated | required according to load and engine speed by controlling the pumping amount of the high pressure pump 22 based on those information.

  A return path 26 for returning the leaked fuel from the injector 10 to the fuel tank 21 is connected to the injector 10. In the return path 26, a back pressure valve 27 for controlling the pressure in the low pressure space in the injector 10 to be equal to or lower than a first predetermined pressure is disposed. Incidentally, while the pressure of the high pressure fuel stored in the pressure accumulator 23 is at least 20 MPa or more, the back pressure valve 27 controls the pressure on the low pressure space side in the injector 10 to about 1 MPa.

  A return path 28 for returning the leaked fuel from the high-pressure pump 22 to the fuel tank 21 is connected to a downstream portion of the return path 26 relative to the back pressure valve 27.

  A filling path 29 connects between the pressure accumulator 23 and a portion upstream of the back pressure valve 27 in the return path 26. The filling path 29 is provided with a safety valve 50 (described later in detail) that opens and closes the filling path 29.

  Next, the injector 10 will be described. FIG. 2 is a cross-sectional view showing the configuration of the injector 10 of FIG.

  As shown in FIG. 2, the injector body 101 includes a fuel inlet portion 102 into which high-pressure fuel from the pressure accumulator 23 is introduced, and a fuel outlet portion 103 that allows the fuel inside the injector 10 to flow out toward the fuel tank 21. ing.

  A nozzle 104 that injects fuel when the valve is opened is disposed on one end of the injector body 101 in the axial direction. The nozzle 104 includes a needle 1041 slidably held on the injector body 101, a nozzle spring 1042 that urges the needle 1041 in a valve closing direction, and a nozzle cylinder 1043 in which a piston portion 1041 a of the needle 1041 is inserted. Have.

  At one end in the axial direction of the injector body 101, an injection hole 106 communicating with the fuel inlet portion 102 via the high pressure fuel passage 105 is formed, and high pressure fuel is injected from the injection hole 106 into the cylinder of the internal combustion engine. ing. A tapered valve seat 107 is formed on the upstream side of the nozzle hole 106, and the nozzle hole 106 is opened and closed when the seat portion 1041 b formed on the needle 1041 contacts and separates from the valve seat 107. The high pressure fuel passage 105 corresponds to the high pressure space of the present invention.

  The piston portion 1041a is slidably and liquid-tightly inserted into the nozzle cylinder 1043, and the piston portion 1041a and the nozzle cylinder 1043 form a control chamber 108 in which the internal fuel pressure can be switched between high pressure and low pressure. ing. The needle 1041 is urged in the valve closing direction by the fuel pressure in the control chamber 108 and is opened in the valve opening direction by the high pressure fuel guided from the fuel inlet 102 to the nozzle hole 106 side through the high pressure fuel passage 105. Be energized.

  A valve chamber 110 in which a control valve 109 for controlling the pressure in the control chamber 108 is accommodated is formed in an intermediate portion in the axial direction of the injector body 101. The valve chamber 110 is always in communication with the control chamber 108 via the communication passage 111. The valve chamber 110 is connected to a high pressure communication passage 105 a branched from the high pressure fuel passage 105. Further, the valve chamber 110 is connected to the fuel outlet portion 103 via the low pressure fuel passage 112.

  The control valve 109 includes a control valve valve body 1091 that opens and closes between the valve chamber 110 and the high pressure communication passage 105a and between the valve chamber 110 and the low pressure fuel passage 112, and between the valve chamber 110 and the high pressure communication passage 105a. A control valve spring 1092 that biases the control valve body 1091 in a direction that opens and closes the space between the valve chamber 110 and the low-pressure fuel passage 112 is provided.

  An actuator chamber 114 in which an actuator 113 for driving the control valve 109 is housed is formed on the other axial end side of the injector body 101. The actuator chamber 114 is connected to the low pressure fuel passage 112 via the low pressure communication passage 112a. The actuator chamber 114 and the low pressure fuel passage 112 constitute the low pressure space of the present invention.

  The actuator 113 includes a piezo stack 1131 in which a large number of piezo elements are stacked and expands and contracts due to charge and discharge, and a drive transmission unit that transmits the expansion and contraction displacement of the piezo stack 1131 to the control valve body 1091 of the control valve 109. . The piezo stack 1131 corresponds to the driving means of the present invention.

  The drive transmission unit is configured as follows. A first piston 1133 and a second piston 1134 are slidably and liquid-tightly inserted into the actuator cylinder 1132, and a liquid chamber filled with fuel is provided between the first piston 1133 and the second piston 1134. 1135 is formed.

  The first piston 1133 is biased toward the piezo stack 1131 by a first piston spring 1136 and is directly driven by the piezo stack 1131. When the piezo stack 1131 is extended, the pressure of the liquid chamber 1135 is increased by the first piston 1133.

  The second piston 1134 is urged to the control valve body 1091 side of the control valve 109 by the second piston spring 1137, and is actuated by receiving the pressure of the liquid chamber 1135 to drive the control valve valve body 1091. It has become. When the piezo stack 1131 is extended, the second piston 1134 operates by receiving the pressure of the liquid chamber 1135 that has been increased in pressure, and the valve chamber 110 and the high-pressure communication passage 105a are closed, and the valve chamber 110 The control valve body 1091 is driven to a position where the low-pressure fuel passage 112 is opened. On the other hand, when the piezo stack 1131 contracts, that is, when the pressure in the liquid chamber 1135 is low, the second piston 1134 is pushed back toward the first piston 1133 by the control valve spring 1092 of the control valve 109 against the second piston spring 1137. It is.

  Next, the safety valve 50 will be described. FIG. 3 is a cross-sectional view showing the configuration of the safety valve 50 of FIG. 1, and FIG. 4 is an enlarged cross-sectional view of the main part of the safety valve 50 of FIG.

  As shown in FIGS. 3 and 4, the safety valve 50 includes a cylindrical valve body 510, and a spring chamber 511 extending in the axial direction is formed in the valve body 510.

  A valve seat 520 is caulked and fixed to one end of the valve body 510 so as to close one end of the spring chamber 511. The other end of the spring chamber 502 is connected to the return path 26 via the filling path 29.

  The valve seat 520 includes a first discharge hole 521 connected to the pressure accumulator 23 via the filling path 29, a guide hole 522 that slidably supports the safety valve body 530 and communicates with the spring chamber 511, a safety valve A safety valve seat surface 523 with which the valve body 530 is contacted and separated is formed.

  The safety valve body 530 is slidably supported in the guide hole 522 and has a substantially cylindrical first valve portion 531 that contacts and separates from the safety valve seat surface 523, and a bottomed cylindrical second valve portion 532 with a flange. And is urged toward the valve closing direction by a safety valve spring 540 disposed in the spring chamber 511.

  A discharge groove 533 that connects the spring chamber 511 and the first discharge hole 521 when the valve is opened is formed on the outer peripheral surface of the first valve portion 531. When the first valve portion 531 is separated from the safety valve seat surface 523 (that is, in the valve open state), the first path configured by the filling path 29, the first discharge hole 521, the discharge groove 533, and the spring chamber 511. The fuel in the pressure accumulator 23 is allowed to escape to the return path 26. In addition, when the first valve portion 531 is in contact with the safety valve seat surface 523 (that is, the valve is closed), the first path is blocked. That is, when the pressure in the pressure accumulator 23 exceeds the second predetermined pressure, the safety valve 50 opens due to the pressure and releases the fuel in the pressure accumulator 23 to the return path 26, so that the pressure in the pressure accumulator 23 becomes abnormally high. To prevent.

  The safety valve 50 is provided with a second path that leads the fuel of the pressure accumulator 23 to the return path 26 in parallel with the first path. In addition, a differential pressure valve that closes the second path when the fuel pressure of the accumulator 23 is higher than the pressure on the return path 26 side by a predetermined differential pressure ΔP is integrated into the safety valve 50.

  The second path and the differential pressure valve will be described below. As shown in FIG. 4, the differential pressure valve chamber 550 formed by the first valve portion 531 and the second valve portion 532 communicates with the first discharge hole 521 through a communication hole 551 formed in the first valve portion 531. In addition, the spring chamber 511 communicates with a second discharge hole 552 formed in the second valve portion 532. The second valve portion 532 is formed with a differential pressure valve seat surface 554 to which the differential pressure valve body 553 contacts and separates. The communication hole 551 corresponds to the inlet side opening of the present invention, and the second discharge hole 552 corresponds to the outlet side opening of the present invention.

  In the differential pressure valve chamber 550, a flanged columnar differential pressure valve valve body 553 that contacts and separates from the differential pressure valve seat surface 554 and opens and closes between the spring chamber 511 and the second discharge hole 552 is disposed. The differential pressure valve body 553 is formed with a differential pressure valve orifice 555 that allows the communication hole 551 and the spring chamber 511 to communicate with each other. In the differential pressure valve chamber 550, a differential pressure valve spring 556 that urges the differential pressure valve body 553 in the valve opening direction is disposed.

  The communication hole 551, the second discharge hole 552, and the differential pressure valve orifice 555 constitute a second path. Further, the differential pressure valve body 553 forms the main part of the differential pressure valve.

  Next, the operation of the fuel injection device will be described. First, in a normal state where air does not enter the liquid chamber 1135 of the actuator 113, when the piezo stack 1131 is energized, the piezo stack 1131 extends and the first piston 1133 is driven, and the first piston 1133 drives the liquid chamber. The pressure at 1135 is increased. The second piston 1134 is driven toward the control valve body 1091 side of the control valve 109 by the pressure of the liquid chamber 1135 that has been increased in pressure. When the control valve body 1091 is driven by the second piston 1134, the valve chamber 110 and the high pressure communication passage 105a are closed, and the valve chamber 110 and the low pressure fuel passage 112 are opened. . Therefore, the control chamber 108 is communicated with the low pressure fuel passage 112 via the communication passage 111 and the valve chamber 110.

  As a result, the pressure in the control chamber 108 decreases and the force for urging the needle 1041 in the valve closing direction decreases, so that the needle 1041 moves in the valve opening direction and the seat portion 1041b moves away from the valve seat 107 and the injection hole. 106 is opened, and fuel is injected into the cylinder of the internal combustion engine from the injection hole 106.

  Thereafter, when the energization to the piezo stack 1131 is stopped, the piezo stack 1131 contracts and the first piston 1133 is returned to the piezo stack 1131 side by the first piston spring 1136. Further, the control valve valve body 1091 and the second piston 1134 are returned to the first piston 1133 side by the control valve spring 1092.

  Thereby, the space between the valve chamber 110 and the high pressure communication passage 105a is opened, and the space between the valve chamber 110 and the low pressure fuel passage 112 is closed. Therefore, the high pressure fuel from the pressure accumulator 23 is introduced into the control chamber 108 via the high pressure fuel passage 105, the high pressure communication passage 105 a, the valve chamber 110, and the communication passage 111.

  As a result, the pressure in the control chamber 108 increases and the force for urging the needle 1041 in the valve closing direction increases, so that the needle 1041 moves in the valve closing direction, and the seat portion 1041b is seated on the valve seat 107 and injected. The hole 106 is closed and the fuel injection is finished.

  Next, an operation at the time of start-up in a state where air has entered the liquid chamber 1135 as in the case of restarting the internal combustion engine after lack of gas will be described. 5A and 5B are enlarged cross-sectional views showing the operating state of the differential pressure valve in the safety valve 50 of FIG.

  When the key switch is operated to the starter ON position in order to start the internal combustion engine, the low pressure pump 20 and the high pressure pump 22 are operated and the fuel is pumped to the accumulator 23. Then, as will be described below, the fuel in the accumulator 23 is supplied to the actuator chamber 114 via the filling path 29 and the second path in the safety valve 50 (that is, the communication hole 551, the differential pressure valve orifice 555, and the second discharge hole 552). The pressure is supplied to the low pressure fuel passage 112 side, and the pressure in the actuator chamber 114, the low pressure fuel passage 112, and the like rises.

  That is, after the low pressure pump 20 and the high pressure pump 22 start operating, when the difference between the pressure in the pressure accumulator 23 and the pressure in the actuator chamber 114 is less than the predetermined differential pressure ΔP, as shown in FIG. The differential pressure valve body 553 is separated from the differential pressure valve seat surface 554, and the fuel in the pressure accumulator 23 is supplied to the actuator chamber 114 via the filling path 29, the second path, and the like. As a result, the pressure in the actuator chamber 114 increases, and the pressure is controlled to a predetermined pressure by the back pressure valve 27.

  Then, since the air in the liquid chamber 1135 is discharged by the fuel supplied to the actuator chamber 114, the injector 10 can be operated normally, and the internal combustion engine can be started even after the gas runs out.

  When the pressure in the accumulator 23 becomes higher than the pressure in the actuator chamber 114 by a predetermined differential pressure ΔP or more, as shown in FIG. 5B, the differential pressure valve body 553 comes into contact with the differential pressure valve seat surface 554, and the second path is The fuel supply to the actuator chamber 114 is stopped by being shut off.

  Incidentally, until the air in the liquid chamber 1135 is discharged and the internal combustion engine is started, the pressure accumulator 23 is maintained so that the difference between the pressure in the pressure accumulator 23 and the pressure in the actuator chamber 114 is kept below a predetermined differential pressure ΔP. It is necessary to control the pressure.

  Therefore, a pressure control method for the accumulator 23 when starting the internal combustion engine will be described. FIG. 6 is a flow chart showing the pressure control process of the pressure accumulator when the internal combustion engine is started, which is executed by the ECU 25, and FIG. 7 is a time chart for explaining the pressure control process of the pressure accumulator when the internal combustion engine is started.

  The process shown in FIG. 6 is started when the key switch is operated to the starter ON position to start the internal combustion engine and the ECU 25 is turned on.

  First, the engine speed Ne and the pressure Pc of the accumulator 23 (hereinafter referred to as the accumulated pressure) detected by the pressure sensor 24 are read (S101).

  Next, in step S102 as start determination means, it is determined whether or not the start of the internal combustion engine is completed. Specifically, it is determined that the start of the internal combustion engine is completed when the engine speed Ne becomes equal to or higher than a predetermined speed Nf. The predetermined rotational speed Nf is set to a rotational speed (for example, 500 rpm) that is higher than the cranking rotational speed and lower than the idling rotational speed.

  Then, during the start of the internal combustion engine, that is, during a predetermined period until the start of the internal combustion engine is completed (step S102: YES), the process proceeds to step S103 as the start time pressure control means, and the accumulated pressure Pc read in step S101. Is controlled to a predetermined pressure range (P1 <Pc <P2). Incidentally, if the first predetermined pressure corresponding to the valve opening pressure of the back pressure valve 27 is Pb, the high pressure side set pressure P2 is set to P2 <Pb + ΔP.

  And while the process of step S101-step S103 is repeated, the differential pressure valve body 553 is separated from the differential pressure valve seat surface 554, and the fuel in the pressure accumulator 23 is supplied to the actuator chamber via the filling path 29, the second path, and the like. 114. Therefore, the air in the liquid chamber 1135 is discharged by the fuel, and the injector 10 can operate normally.

  Thereafter, when the injector 10 can be operated normally and the start of the internal combustion engine is completed (step S102: NO), the process proceeds to step S104, and the accumulated pressure Pc is set to the normal pressure level based on the map stored in the ROM of the ECU 25. (For example, about 40 MPa). Specifically, the control target value of the accumulated pressure Pc is obtained from the map based on the engine speed Ne and the fuel injection amount, and the pumping amount of the high-pressure pump 22 is controlled so that the accumulated pressure Pc becomes the control target value. .

  As described above, in this embodiment, when the internal combustion engine is started in a state where air has entered the liquid chamber 1135, the differential pressure valve body 553 is separated from the differential pressure valve seat surface 554, and the fuel in the pressure accumulator 23 is discharged. The fuel is supplied to the actuator chamber 114 via the filling path 29, the second path, and the like, and the air in the liquid chamber 1135 is discharged by the fuel. Therefore, the injector 10 can operate normally and the internal combustion engine can be started.

  The filling path 29 communicates the downstream side of the high-pressure pump 22 (more specifically, the accumulator 23) and the upstream side of the back pressure valve 27 in the return path 26. The length can be made shorter than the length of the pipe for guiding the fuel from the low-pressure pump in the fuel injection device described in Patent Document 1 to the low-pressure space in the injector, and therefore the piping is simplified. can do.

  Furthermore, since the differential pressure valve is integrally incorporated in the safety valve 50, in the case of a fuel injection device provided with the safety valve 50, it is possible to implement without changing (adding) the handling of the return path 26.

Furthermore, since the low pressure space of the injector 10 can be prevented from becoming high pressure by the differential pressure valve, the pressure resistance required performance on the low pressure side of the injector 10 can be reduced.
(Second Embodiment)
A second embodiment of the present invention will be described. 8 is a system diagram showing the piping configuration of the fuel injection device according to the second embodiment of the present invention, FIG. 9 is an enlarged cross-sectional view of the main part of the safety valve 50 of FIG. 8, and FIGS. It is sectional drawing which shows the operating state of the differential pressure | voltage valve 60 of 8. FIG. In addition, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment, and the description is abbreviate | omitted.

  In the first embodiment, the differential pressure valve is integrated into the safety valve 50, but in this embodiment, the safety valve 50 and the differential pressure valve 60 are separated as shown in FIG. The safety valve 50 is disposed in the discharge path 30 that connects between the pressure accumulator 23 and a portion downstream of the back pressure valve 27 in the return path 26. The differential pressure valve 60 is disposed in a filling path 29 that connects the pressure accumulator 23 and a portion upstream of the back pressure valve 27 in the return path 26.

  As shown in FIG. 9, the safety valve 50 is different from the first embodiment in the configuration of the safety valve body 530. That is, in the safety valve body 530 of the present embodiment, the differential pressure valve body 553 (see FIG. 4) and the differential pressure valve spring 556 (see FIG. 4) are deleted, and the first valve portion 531 (see FIG. 4) and the two valve portions. 532 (see FIG. 4) is integrated with a flanged cylinder.

  When the pressure in the pressure accumulator 23 exceeds the second predetermined pressure, the safety valve 50 is in a state in which the safety valve body 530 is separated from the safety valve seat surface 523 (that is, a valve open state), and the discharge path 30, the first discharge The fuel in the pressure accumulator 23 is released to the return path 26 through the hole 521, the discharge groove 533, and the spring chamber 511, thereby preventing the inside of the pressure accumulator 23 from becoming an abnormally high pressure.

  As shown in FIG. 10, the differential pressure valve 60 includes a cylindrical differential pressure valve body 610. The differential pressure valve body 610 includes a differential pressure valve spring chamber 611 extending in the axial direction thereof and a return path 26 via a filling path 29. And a differential pressure valve body through-hole 612 communicating with the differential pressure valve spring chamber 611 and a differential pressure valve seat surface 613 where the differential pressure valve body 620 contacts and separates are formed.

  A differential pressure valve cover 630 is joined to one end of the differential pressure valve body 610 so as to close one end of the differential pressure valve spring chamber 611. The differential pressure valve cover 630 is formed with a cover through hole 631 that is connected to the pressure accumulator 23 through the filling path 29 and communicates with the differential pressure valve spring chamber 611. The cover through hole 631 corresponds to the inlet side opening of the present invention, and the differential pressure valve body through hole 612 corresponds to the outlet side opening of the present invention.

  The differential pressure valve valve body 620 has a stepped columnar shape and is slidably disposed in the differential pressure valve spring chamber 611. A differential pressure valve outer circumferential groove 621, a differential pressure valve orifice 622, and a differential pressure valve central hole 623 are formed in the differential pressure valve body 620 to communicate with the differential pressure valve spring chamber 611 and the cover through hole 631.

  Further, the differential pressure valve valve body 620 includes a small diameter cylindrical portion 624, and the tip side of the small diameter cylindrical portion 624 contacts and separates from the differential pressure valve seat surface 613, so that the differential pressure valve spring chamber 611 and the differential pressure valve body through-hole 612 are separated. The space is opened and closed.

  In the differential pressure valve spring chamber 611, a differential pressure valve spring 640 that biases the differential pressure valve body 620 in the valve opening direction is disposed.

  Next, a description will be given of an operation at the time of start-up in a state where air has entered the liquid chamber 1135 (see FIG. 2) as in the case of restarting the internal combustion engine after lack of gas.

  Since the accumulated pressure is low before cranking the internal combustion engine, as shown in FIG. 10A, the differential pressure valve body 620 is urged by the differential pressure valve spring 640 and is in contact with the differential pressure valve cover 630.

  When the key switch is operated to the starter ON position in order to start the internal combustion engine, the low pressure pump 20 and the high pressure pump 22 are operated and the fuel is pumped to the pressure accumulator 23 to increase the pressure accumulation.

  When the difference between the accumulated pressure and the pressure in the actuator chamber 114 (see FIG. 2) is less than the predetermined differential pressure ΔP, the differential pressure valve body 620 resists the differential pressure valve spring 640 as shown in FIG. To the differential pressure valve seat surface 613 side. However, at this time, the distal end side of the small diameter cylindrical portion 624 is separated from the differential pressure valve seat surface 613. Therefore, the fuel in the pressure accumulator 23 passes through the filling path 29, the cover through hole 631, the differential pressure valve center hole 623, the differential pressure valve orifice 622, the differential pressure valve outer circumferential groove 621, the differential pressure valve spring chamber 611, and the differential pressure valve body through hole 612. To the actuator chamber 114. As a result, the pressure in the actuator chamber 114 increases, and the pressure is controlled to a predetermined pressure by the back pressure valve 27.

  Then, since the air in the liquid chamber 1135 is discharged by the fuel supplied to the actuator chamber 114, the injector 10 can be operated normally, and the internal combustion engine can be started even after the gas runs out.

  When the accumulated pressure becomes higher than the pressure in the actuator chamber 114 by a predetermined differential pressure ΔP or more, as shown in FIG. 10C, the distal end side of the small diameter cylindrical portion 624 comes into contact with the differential pressure valve seat surface 613 to close the valve. The fuel supply to 114 is stopped.

(Third embodiment)
A third embodiment of the present invention will be described. In the second embodiment, the present invention is applied to the fuel injection device including the safety valve 50 that prevents the inside of the pressure accumulator 23 from becoming an abnormally high pressure. However, the present invention includes an electromagnetic pressure reducing valve instead of the safety valve 50. The present invention can also be applied to a fuel injection device.

  FIG. 11 is a cross-sectional view showing the electromagnetic pressure reducing valve 70, and the configuration thereof is the same as that described in Japanese Patent Application Laid-Open No. 2001-182638, and thus the description of the configuration is omitted. The pressure reducing valve 70 rapidly reduces the accumulated pressure to a target value at the time of deceleration or the like in order to prevent, for example, combustion noise due to a delay in lowering the injection pressure. When the coil 710 is energized, the armature 720 and the valve The body 730 is aspirated to open, and the high-pressure fuel in the pressure accumulator 23 is discharged to the return path 26 via the discharge path 30.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. In each of the above embodiments, the communication hole 551 (see FIG. 4) or the cover through hole 631 (see FIG. 10) corresponding to the inlet side opening of the differential pressure valve is connected to the pressure accumulator 23, but as shown in FIG. The cover through hole 631 of the differential pressure valve 60 may be connected between the high pressure pump 22 and the pressure accumulator 23.

  Even in this case, when the internal combustion engine is started in a state where air has entered the liquid chamber 1135 (see FIG. 2), the high-pressure fuel discharged from the high-pressure pump 22 is supplied to the actuator chamber 114 (see FIG. 2). Since the fuel discharges air from the liquid chamber 1135, the injector 10 (see FIG. 2) can operate normally and the internal combustion engine can be started.

(Fifth embodiment)
A fifth embodiment of the present invention will be described. In each of the above embodiments, the communication hole 551 (see FIG. 4) or the cover through hole 631 (see FIG. 10) corresponding to the inlet side opening of the differential pressure valve is connected to the pressure accumulator 23, but as shown in FIG. The cover through hole 631 of the differential pressure valve 60 may be connected between the low pressure pump 20 and the high pressure pump 22.

  According to this, since the low pressure space of the injector 10 can be prevented from becoming high pressure by the differential pressure valve, the pressure resistance required performance on the low pressure side of the injector 10 can be lowered.

(Other embodiments)
In the first to third embodiments, one end of the filling path 29 is connected to the pressure accumulator 23, but the filling path 29 supplies the high-pressure fuel downstream from the high-pressure pump 22 to the upstream side of the back pressure valve 26 in the return path 26. Therefore, one end of the filling path 29 may be connected between the high-pressure pump 22 and the accumulator 23.

It is a distribution diagram showing the piping composition of the fuel injection device concerning a 1st embodiment of the present invention. It is sectional drawing which shows the structure of the injector 10 of FIG. It is sectional drawing which shows the structure of the safety valve 50 of FIG. It is an expanded sectional view of the principal part in the safety valve 50 of FIG. It is an expanded sectional view which shows the operating state of the differential pressure | voltage valve in the safety valve 50 of FIG. It is a flowchart which shows the pressure control process of the pressure accumulator at the time of the internal combustion engine start performed by ECU25 of FIG. 2 is a time chart for explaining pressure control processing of an accumulator at the time of starting an internal combustion engine executed by an ECU 25 in FIG. 1. It is a systematic diagram which shows the piping structure of the fuel injection apparatus which concerns on 2nd Embodiment of this invention. It is an expanded sectional view of the principal part in the safety valve 50 of FIG. It is sectional drawing which shows the operating state of the differential pressure valve 60 of FIG. It is sectional drawing of the pressure-reduction valve used for the fuel-injection apparatus which concerns on 3rd Embodiment of this invention. It is a systematic diagram which shows the piping structure of the fuel injection apparatus which concerns on 4th Embodiment of this invention. It is a systematic diagram which shows the piping structure of the fuel injection apparatus which concerns on 5th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Injector, 20 ... Low pressure pump, 21 ... Fuel tank, 22 ... High pressure pump, 23 ... Accumulator, 26 ... Return path, 27 ... Back pressure valve, 29 ... Filling path, 60, 553 ... Differential pressure valve, 104 ... Nozzle, DESCRIPTION OF SYMBOLS 105 ... High pressure fuel passage (high pressure space), 106 ... Injection hole, 108 ... Control chamber, 109 ... Control valve, 112 ... Low pressure fuel passage (low pressure space), 114 ... Actuator chamber (low pressure space), 1041 ... Needle, 1131 ... Piezo stack (driving means), 1133... First piston, 1134... Second piston, 1135.

Claims (3)

A low pressure pump (20) for pumping fuel sucked from the fuel tank (21);
A high-pressure pump (22) that pressurizes and pumps fuel pumped from the low-pressure pump (20);
A pressure accumulator (23) for storing high-pressure fuel pumped from the high-pressure pump (22);
An injector (10) for injecting high-pressure fuel stored in the pressure accumulator (23) into the internal combustion engine;
A return path (26) for returning the fuel in the low pressure space (112, 114) in the injector (10) to the fuel tank (21);
A back pressure valve (27) disposed in the return path (26) and controlling the pressure of the low pressure space (112, 114) to be equal to or lower than a first predetermined pressure;
The injector (10)
A nozzle (104) that opens and closes the nozzle hole (106) by operating the needle (1041) by increasing or decreasing the pressure in the control chamber (108);
A control valve (109) for selectively communicating the control chamber (108) with the low pressure space (112, 114) or the high pressure space (105);
A second piston (1134) disposed in the low pressure space (112, 114) and driving the control valve (109);
A first piston disposed in the low-pressure space (112, 114) and driving the second piston (1134) via fuel in a liquid chamber (1135) formed between the second piston (1134). A piston (1133);
Drive means (1131) for driving the first piston (1133) ,
A fuel injection device configured to control the amount of high-pressure fuel pumped from the high-pressure pump (22) to control the pressure of high-pressure fuel in the accumulator (23) ,
A charging path (29) for guiding high-pressure fuel downstream from the high-pressure pump (22) to a portion upstream of the back pressure valve (27) in the return path (26) ;
A differential pressure valve (60) disposed in the filling path (29) and closing the filling path (29) when the pressure on the high pressure pump (22) side becomes higher than the pressure on the return path (26) by a predetermined differential pressure or more. 553),
Start determination means (S102) for determining whether or not the start of the internal combustion engine has been completed;
Until the start determination means determines that the start of the internal combustion engine is completed, the high pressure fuel in the accumulator (23) is maintained so that the open state of the differential pressure valve (60, 553) is maintained. A fuel injection apparatus comprising : a start time pressure control means (S103) for controlling pressure . When the pressure on the high-pressure pump (22) side becomes equal to or higher than a second predetermined pressure, a safety valve (50) that opens the filling path (29) is provided, and the differential pressure valve (553) is incorporated in the safety valve (50). The fuel injection device according to claim 1 . The fuel injection device according to claim 2 , wherein the safety valve (50) is assembled to the pressure accumulator (23).

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