JP2010038139A - Accumulating fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device having safety and high performance without causing breakage of a leak line or an injector internal member even when leak fuel pressure abnormally rises above set pressure because of some trouble of the accumulating fuel injection device. <P>SOLUTION: A piezo injector 2 connected to a common rail 1 includes a driving force transmission mechanism for transmitting the driving force of an actuator via an oil tight chamber. In the leak line 12 for guiding leak fuel from the piezo injector 2 to a fuel tank T, a leak line pressure setting valve 5 and a safety valve mechanism 6 are provided which holds the leak fuel pressure at predetermined set pressure and which is operated to open a passage to the fuel tank T only when the leak fuel pressure in the leak line 12 rises over the predetermined set pressure, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an accumulator fuel injection device, and more particularly to an accumulator fuel injection device provided with a mechanism for holding a low pressure fuel pressure in a leak line at a set pressure.

For example, as disclosed in Patent Document 1, there is known an accumulator fuel injection device that accumulates high-pressure fuel for injection by providing a common rail (accumulation chamber) common to a plurality of cylinders of an internal combustion engine. In recent years, piezo injectors have been used as injectors provided for the respective cylinders because of their good responsiveness. In order to effectively transmit the driving force of a piezoelectric actuator that is a driving source of the piezoelectric injector to a needle valve, for example, a structure including a driving force transmission mechanism disclosed in Patent Document 2 is generally used.
Japanese Patent No. 3638297 JP 2002-257002 A

  The driving force transmission mechanism generally includes a piezoelectric actuator and an oil tight chamber formed by filling hydraulic oil between a pair of pistons. The piezo actuator is housed in a housing in order to protect the piezoelectric elements and electrode members which are internal components, and one of the pair of pistons is integrally displaced as the piezo actuator expands and contracts. The oil-tight chamber has a function to convert the displacement of this piston to hydraulic pressure and transmit it to the other piston. When a pair of pistons are large and small diameter pistons, the displacement of the piezo actuator is expanded according to the pressure receiving area ratio of the large and small diameter pistons. Can communicate.

  By the way, in order for the driving force transmission mechanism to always function, it is necessary to continue to replenish fuel (light oil, etc.) into the oil-tight chamber. Patent Document 2 discloses a structure in which a reciprocating means is provided with a passage communicating with a low-pressure fuel reservoir in a piston and provided with a check valve to replenish using a differential pressure inside and outside the oil-tight chamber. . As another means, for example, there is a method of replenishing from the sliding clearance portion on the outer periphery of the piston when the oil tight chamber becomes negative pressure by positively raising the ambient pressure by installing a positive pressure pump.

  In any of the replenishing means, it is necessary to keep the pressure of the low pressure fuel line by the injector leak fuel, that is, the external passage for replenishing the fuel through the passage with the check valve or the sliding clearance portion in the oil tight chamber. Normally, a check valve is provided in the middle of the leak line from the injector to the fuel tank as means for holding the low-pressure fuel pressure at the set pressure, and the valve opening pressure is set by a spring force that urges the valve body. .

  However, if the check valve malfunctions for some reason, for example, foreign matter is generated due to the collision of the movable member in the injector and enters the leak line, resulting in clogging of the check valve, fuel from the leak line to the fuel tank Discharge becomes difficult. Alternatively, if the common rail pressure rises due to a control error or the like, the leak flow rate from the metal surface seal of the injector increases before the pressure limiter or fail safe provided with the common rail described in Patent Document 1, for example, is checked. The fuel discharge from the valve cannot catch up.

  As a result, the fuel pressure in the leak line rises above the set pressure. In the worst case, the leak line member made of resin or rubber hose may be damaged, which may cause fuel leakage or combustion failure. In order to avoid this, the leak line member may be made of metal, but this time, there is a possibility that the casing inside the injector may be damaged to cause a malfunction of the piezoelectric actuator. In such a case, even if the cause of the primary failure (for example, check valve clogging) is removed, it may be considered that the subsequent drive of the injector is hindered.

  Therefore, in the accumulator fuel injection device having a mechanism for holding the low pressure fuel pressure of the leak line at a constant pressure, even if some trouble occurs and the leak fuel pressure rises abnormally beyond the set pressure, It is an object of the present invention to provide a safe and high-performance fuel injection device without causing damage to a leak line member or damage to a piezoelectric actuator housing inside an injector.

The invention of claim 1 is a pressure accumulation type fuel injection device for injecting high pressure fuel supplied from a pressure accumulation chamber into a cylinder of an internal combustion engine,
The injector provided for each cylinder has a driving force transmission mechanism that transmits the driving force of the actuator through the oil-tight chamber,
In the leak line that guides the leaked fuel from the injector to the fuel tank, a leak line pressure setting valve that holds the leak fuel pressure at a predetermined set pressure is provided,
A safety valve mechanism that operates only when the leak fuel pressure in the leak line rises above a predetermined allowable pressure and opens the passage to the fuel tank is provided.

  The safety valve mechanism of the present invention quickly opens, for example, when an abnormal fuel pressure in a leak line due to foreign matter contamination occurs. Since this mechanism does not operate when the leak line is within the allowable pressure range, it does not affect the operation of the leak line pressure setting valve.

  Therefore, during normal control, the leak line pressure setting valve maintains the leak fuel pressure at the set pressure, so that the oil-tight chamber of the driving force transmission mechanism is replenished with fuel as hydraulic oil from the sliding clearance portion, etc. It can be effectively demonstrated. On the other hand, when an abnormality occurs, the safety valve mechanism is quickly activated to discharge the fuel to the fuel tank, thereby preventing the leak line member and the constituent members of the injector from being damaged. Therefore, it is possible to achieve a high-performance and highly practical pressure accumulation fuel injection device that achieves both high-precision fuel injection performance from the injector and improved safety.

  According to a second aspect of the present invention, the safety valve mechanism is provided integrally with the leak line pressure setting valve. The leak line pressure setting valve includes a valve body that opens and closes the passage in a valve housing that forms a passage that forms a part of the leak line, and the valve body leaks from the injector. When the fuel pressure exceeds the set pressure, it functions as a check valve that opens the leaked fuel, and when the leaked fuel pressure from the injector exceeds the allowable pressure, the opening area is rapidly expanded. It also functions as a safety valve that opens the passage.

  By improving the existing leak line pressure setting valve and providing the valve body with a check valve function and a safety valve function, safety can be improved without adding a new device to the leak line. it can. Moreover, by providing the valve body in common, the apparatus can be made compact without greatly changing the existing configuration, and an increase in cost can be suppressed.

  According to a third aspect of the present invention, the valve element forms a first throttle that increases the opening area with an increase in the leak fuel pressure in the normal control region within a predetermined range from the set pressure, and from the upper limit pressure of the normal control region. In the pulsation region up to the permissible pressure, a second throttling is formed to maintain the upper limit opening area of the first throttling, and in the abnormally open region above the permissible pressure, the maximum opening area is quickly increased due to an increase in leak fuel pressure. A third diaphragm is formed.

  Specifically, in the first throttle and the second throttle that function as check valves, immediately after opening the valve, the opening area is changed according to the leak fuel pressure, the passing flow rate is increased or decreased, and the set pressure is quickly maintained. . In a region where the leak fuel pressure is slightly high, the pressure fluctuation of the leak line due to pulsation or the like is satisfactorily absorbed with a relatively large constant opening area. The third throttle, which functions as a safety valve, further increases the leak fuel pressure and instantly reaches the maximum opening area in the area where abnormal pressure is determined, thereby quickly opening the flow path and preventing damage to the device. To do. Thus, by forming the first throttle, the second throttle, and the third throttle according to the leak fuel pressure, the leak fuel pressure can be stably held at the set pressure while ensuring safety.

  According to a fourth aspect of the present invention, the valve body includes a conical sheet portion whose diameter is reduced toward the tip end side, and a columnar tip portion having the same diameter as the tip minimum diameter portion of the sheet portion and smaller than the sheet diameter. After the valve body is separated, the first throttle is formed between the side surface of the seat portion and the seat, and then the second throttle is formed between the side surface of the tip portion and the seat. The third diaphragm is formed between the end face of the tip and the sheet.

  More specifically, when the valve body has a cylindrical tip portion and a shape having a conical sheet portion that follows, the first throttle whose opening area changes as the valve body lifts at the time of valve opening, a constant opening A second diaphragm having an area and a third diaphragm for opening the passage are formed in this order.

  In the invention of claim 5, a spring for urging the valve body in the seating direction is disposed in the valve housing, and a stopper for holding the valve body at a position having a maximum opening area is formed.

  Preferably, a stopper that regulates the lift position of the valve body is provided, and safety and stability can be secured by maintaining the maximum opening area that opens the passage.

  According to a sixth aspect of the present invention, the safety valve mechanism is disposed in a branch passage that communicates the leak line on the injector side with the fuel tank from the leak line pressure setting valve, and the leak fuel pressure exceeds the allowable pressure. It is a mechanical safety valve that is set to open when the valve is opened to open the branch passage.

  The safety valve mechanism may be provided separately from the leak line pressure setting valve. For example, the safety can be easily improved by providing a mechanical safety valve in which the spring force is set so that the valve body is opened when the allowable pressure is exceeded in parallel with the leak line pressure setting valve.

  According to a seventh aspect of the present invention, the safety valve mechanism is disposed in a branch passage that communicates the leak line on the injector side with the fuel tank from the leak line pressure setting valve, and the leak fuel detected by the pressure detection means It is an electric safety valve that opens when the pressure exceeds the allowable pressure to open the branch passage.

  The safety valve mechanism may be provided separately from the leak line pressure setting valve. For example, by providing a pressure detection means for monitoring the leak fuel pressure and providing an electric safety valve in parallel with the leak line pressure setting valve for controlling the valve body to open quickly when the allowable pressure is exceeded, Safety can be improved easily.

  In the invention of claim 8, the driving force transmission mechanism is a mechanism for transmitting the displacement of the piezo actuator via the oil pressure of an oil tight chamber formed between a pair of pistons.

  Specifically, by adopting the driving force transmission mechanism configured as described above, the displacement of the piezo actuator can be transmitted effectively, and the oil-tight chamber can be replenished satisfactorily with high performance. An injector can be realized.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of an accumulator fuel injection device according to the present invention. Here, an example of application to a four-cylinder diesel engine will be described. The pressure accumulation fuel injection device of the present invention includes a common rail 1 as a pressure accumulation chamber in common to each cylinder of an engine (not shown). A plurality of piezo injectors 2 provided for each cylinder of the engine are connected to the common rail 1, and high-pressure fuel supplied from the common rail 2 through the high-pressure line 11 is injected into the corresponding cylinder.

  High pressure fuel is pumped from the supply pump 3 to the common rail 1 and accumulated at a predetermined pressure corresponding to the fuel injection pressure. The supply pump 3 is a variable discharge high-pressure pump having a known structure. After the fuel sucked from the fuel tank T through the fuel filter F is pressurized to the feed pressure by the built-in feed pump, the suction metering valve Then, a predetermined amount is sucked into the plunger chamber, further pressurized, and sent out from the pressure feed passage 31 to the common rail 1. The feed pressure fuel from the feed pump is also supplied to the fuel addition valve 32 and the like installed in the exhaust passage of the engine.

  Driving of the injector 2 and the supply pump 3 is controlled by an ECU 41 and an EDU 42 that constitute the control unit 4. The ECU 41 is an electronic control unit having a known structure including a CPU, a ROM, a storage device such as a RAM, an input / output circuit, and the like for performing various arithmetic processes, and is provided on one end side of the common rail 1 to detect the accumulated fuel pressure. In addition to the detection signal of the common rail pressure sensor (Pc sensor) 13, detection signals such as the accelerator opening and the rotation speed are input from various sensors. The ECU 41 performs a calculation based on these detection signals, and outputs a drive signal to the injector 2 and the supply pump 3 via the EDU 42 so that an injection amount and an injection pressure corresponding to the operating state can be obtained.

  A pressure reducing valve 14 is provided on the other end side of the common rail 1. The pressure reducing valve 14 is connected to a leak line 12 for collecting fuel in the fuel tank T, and is opened by a control signal from the ECU 41 to reduce the common rail pressure. Thus, the pressure is quickly controlled to a pressure corresponding to the vehicle running state, and also serves as a pressure limiter that opens when the fuel pressure in the common rail 1 becomes excessive and releases the fuel to the leak line 12 at once.

  FIG. 2 is a diagram illustrating a detailed configuration example of the injector 2 used in the present embodiment, and a control valve 22 having a three-way valve structure disposed at a lower end portion of the housing H by a driving force transmission mechanism 21 accommodated in the housing H. Is opened and closed to increase or decrease the pressure in the control chamber 23 provided at the upper end of the nozzle body B. Plates P1 and P2 are disposed between the housing H and the nozzle body B, and a high-pressure passage 24 extending in the axial direction is formed in these members so that high-pressure fuel is supplied from the external high-pressure line 11. It has become. The tip of the high-pressure passage 24 communicates with a fuel reservoir 27 provided on the outer periphery of the needle 26. Further, the housing H is provided with a low pressure passage 25 communicating with the external leak line 12 in parallel with the high pressure passage 24.

  The driving force transmission mechanism 21 uses a piezo actuator 201 disposed in the upper part of the housing H as a driving source, a flange member 202 that contacts the lower part thereof to transmit displacement, a large-diameter piston 203 that is a pair of pistons, and a small-diameter piston. 204 and a displacement expansion chamber 205 as an oil-tight chamber formed between the large and small pistons 203, 204. The piezo actuator 201 is formed by laminating disk-shaped piezoelectric elements with electrodes interposed therebetween, and is housed in a housing (not shown) in order to protect the piezoelectric elements and electrode members that are constituent parts.

  The piezo actuator 201 expands by charging and contracts when discharged. When the flange member 202 pushes down the large-diameter piston 203 along with the occurrence of this displacement, the pressure in the displacement expansion chamber 205 filled with fuel as hydraulic oil is increased, and the displacement is expanded and transmitted to the small-diameter piston 204. The displacement expansion rate at this time is determined according to the pressure receiving area ratio of the large diameter piston 203 and the small diameter piston 204.

  A spring chamber 206 communicating with the low pressure passage 24 is formed around the pair of pistons 203 and 204. In the spring chamber 206, a spring 207 is accommodated to urge the large-diameter piston 203 toward the piezo actuator 201 so that it can move up and down integrally, and a predetermined initial load is applied to the piezo actuator 201.

  The driving force transmission mechanism 21 has a shaft member 208 that contacts the hemispherical control valve 22 accommodated in the valve chamber 211 on the distal end side of the small diameter piston 204. When the small diameter piston 204 pushes down the control valve 22 via the shaft member 208, the control valve 22 is separated from the low pressure seat communicating with the low pressure passage 25 and is seated on the opposing high pressure seat.

  The valve chamber 211 is supplied with high-pressure fuel from a passage 212 formed in the plate P2 via a high-pressure seat, and is always in communication with the control chamber 23 by a communication passage 213 formed in the plates P1 and P2. Therefore, the fuel in the control chamber 23 flows out into the low pressure passage 25 via the valve chamber 211, and the pressure in the control chamber 23 that applies back pressure to the needle valve 26 decreases, so that the needle valve 26 opens and the fuel is discharged. Injection starts. The fuel injection is stopped by contracting the piezo actuator 201 by discharging and returning each member to the initial position.

  Here, in order to effectively transmit the displacement of the piezo actuator 201 by the driving force transmission mechanism 21, a mechanism for replenishing the fuel when the fuel in the displacement expansion chamber 205 decreases due to leakage or the like is required. In the configuration of FIG. 2, the fuel flows into the displacement expansion chamber 205 due to a pressure difference between the inside and outside through a sliding clearance portion on the outer periphery of the large-diameter piston 203 accommodated in the spring chamber 206. Alternatively, a passage that communicates the spring chamber 206 and the displacement expansion chamber 205 may be provided inside the large-diameter piston 203 so that fuel is supplied to the displacement expansion chamber 205 via a check valve.

  In either case, the pressure in the low-pressure passage 25 communicating with the spring chamber 206 needs to be sufficiently higher than the displacement expansion chamber 205. Accordingly, in the present invention, in order to smoothly replenish the displacement expansion chamber 205 with fuel, the leak fuel pressure in the leak line 12 is maintained at a predetermined set pressure or more and the safety is improved as shown in FIG. Equipped with an injector return system.

  FIG. 1 shows a basic configuration of an injector return system. A leak line 12 has a branch path connected to each injector 2 corresponding to each cylinder, and fuel leaks fuel from a low pressure passage 24 in the injector 2. It is designed to return to the tank T. A leak line pressure setting valve 5 for setting the leak fuel pressure is provided in the middle of the leak line 12, and a safety valve mechanism 6 that is a feature of the present invention is also provided. The leak line 12 is constituted by a resin or rubber hose, or a metal pipe.

  The leak line pressure setting valve 5 includes a passage that forms part of the leak line 12, a valve body that opens and closes the passage, and a spring that biases the valve body in the valve closing direction, and is directed from the injector 2 toward the fuel tank T. It has a check valve structure that allows only fuel movement. When the back pressure of the valve body, that is, the leak fuel pressure exceeds a predetermined pressure adjusted by the spring, the valve body opens against the spring force, and leak fuel is flowed out to be held at the set pressure. The safety valve mechanism 6 has a configuration in which the leak line 12 and the fuel tank T are directly connected and the leak line 12 can be opened without going through the leak line pressure setting valve 5. The safety valve mechanism 6 opens only when the leak fuel pressure exceeds a predetermined allowable pressure, opens the leak line 12, and returns the fuel to the fuel tank T promptly.

  In the injector return system, a leak fuel passage 33 from a feed pump built in the supply pump 3 is provided via a check valve 34 as means for increasing the pressure when the pressure in the leak line 12 is reduced. The leak line pressure setting valve 5 is connected to the leak line 12 on the injector 2 side. For example, if the pressure in the leak line 12 is low at the start, the injector 2 may not be driven. However, by supplying fuel at a feed pressure upstream of the leak line pressure setting valve 5, the leak pressure is increased and vice versa. The back valve is prevented by the stop valve 34, and the leak pressure can be stably maintained at the set pressure.

  In FIG. 1, in order to explain the basic configuration of the injector return system, the leak line pressure setting valve 5 and the safety valve mechanism 6 are described separately, but specifically, both may be provided integrally. it can. In the case of a separate body, the safety valve mechanism 6 includes a mechanical safety valve that is set to open when a predetermined allowable pressure is exceeded, such as the leak line pressure setting valve 5, or an electric drive unit that includes an electromagnetic drive unit or the like. It can be a safety valve of the type. These detailed configurations will be described below as the first to third embodiments.

(First embodiment)
FIG. 3A shows a main part of the injector return system according to the first embodiment of the present invention. In the present embodiment, a leak line pressure setting valve 7 having a built-in safety valve mechanism, in which the leak line pressure setting valve 5 and the safety valve mechanism 6 of FIG. 1 are integrally provided, is connected to the leak line 12 extending from the injector 2 to the fuel tank T. Install.

  As shown in the enlarged sectional view in the drawing, the leak line pressure setting valve 7 is configured by accommodating a valve body 72 in a valve chamber 73 provided in a valve housing 71. In the valve chamber 73, a leak fuel passage 74 connected to the leak line 12 on the injector 2 side is opened at the center of the bottom surface, and a conical taper-shaped seat 75 is formed around the opening so that the valve body 72 is seated. It has become. A leak fuel passage 76 connected to the leak line 12 on the fuel tank T side is opened on the side surface of the valve chamber 73. A flow path from the leak fuel passage 74 to the leak fuel passage 76 through the valve chamber 73 becomes a part of the leak line 12.

  In the valve body 72, the lower end portion following the substantially cylindrical main body portion is a conical sheet portion 721 whose diameter is reduced toward the distal end side, and the subsequent cylindrical distal end portion 722 is located in the leak fuel passage 74. ing. A spring 77 is accommodated in a recess 723 opened on the upper surface of the main body of the valve body 72, and urges the valve body 72 in the seating direction. The upper end of the spring 77 protrudes above the valve body 72 and is held in a recess 731 provided at the center of the top surface of the valve chamber 73. The annular portion around the recess 731 serves as a stopper 78 that regulates the lift amount of the valve body 72.

  The leak line pressure setting valve 7 adjusts the urging force of the spring 77, thereby adjusting the valve opening pressure of the valve body 72 and holding the pressure of the leak line 12 on the injector 2 side at a predetermined set pressure. Although this pressure varies depending on conditions, for example, by setting the pressure to 200 kPa, the oil-tight chamber 205 can be refilled with fuel. Further, when the leak line 12 becomes abnormal pressure, it also functions as a safety valve. When a predetermined allowable pressure is exceeded, the leak line 12 is fully opened and the leak fuel passage 74 is opened. Further, the valve body 72 has a conical seat portion 721 that makes the opening area variable at the time of valve opening, and has a cylindrical tip portion 722, so that it has a function of absorbing pulsation and stabilizes the leak line pressure. The set pressure can be controlled. The behavior when these valves are opened will be described with reference to FIGS.

  3 (b) shows a state where the valve opening pressure (for example, 1.1 MPa) exceeds a preset valve opening state from the closed state of FIG. 3 (a), and the conical sheet portion 721 of the valve body 72 pulls the seat 75 down. The valve opening state immediately after leaving the seat is shown, and a first throttle is formed between the conical seat portion 721 and the seat 75. As shown in FIGS. 4 and 5, the first throttle region is a normal control region in which the opening area of the first throttle through which the leak fuel passes gradually increases as the valve lift amount increases. That is, the opening area changes in accordance with the leak fuel pressure flowing into the leak fuel passage 74, and the opening area increases as the pressure increases. Therefore, excess fuel is quickly discharged to bring the pressure of the leak line 12 to the set pressure. Can be reduced.

  3B shows a state in which the cylindrical tip 722 of the valve body 72 is located in the same plane as the seat 75, and the second end between the cylindrical tip 722 and the seat 75 is the second. A diaphragm is formed. As shown in FIGS. 4 and 5, the second throttle region has a cylindrical shape from the valve lift amount at which the lowermost end of the conical seat portion 721, that is, the upper end of the cylindrical tip portion 722 is in the same plane as the seat 75. The lower end of the front end portion 722 is a pulsation absorbing region that maintains a relatively large constant opening area without changing the opening area of the second throttle through which the leak fuel passes until the valve lift amount is in the same plane as the seat 75. .

  For this reason, even if the pressure of the leak line 12 flowing into the leak fuel passage 74 temporarily rises due to pulsation or the like, the leak fuel passage 74 does not immediately fully open, and a constant opening corresponding to the maximum opening area of the first throttle. Let the fuel flow out of the area. Accordingly, the leak fuel pressure can be quickly reduced to the set pressure without rapidly decreasing, and the fluctuation of the leak fuel pressure can be suppressed and stably controlled to the set pressure.

  The right view of FIG. 3B shows a state in which the cylindrical tip 722 of the valve body 72 is positioned above the seat 75, and a third diaphragm is formed between the cylindrical tip 722 and the seat 75. Is done. As shown in FIGS. 4 and 5, the third throttle region opens when the leak fuel pressure flowing into the leak fuel passage 74 exceeds a preset allowable pressure (for example, 1.4 MPa), and the pressure increases. As a result, the opening area of the third diaphragm is suddenly enlarged to open the leak fuel passage 74, which is an abnormally open region.

  That is, even if some abnormality occurs and the leak fuel pressure flowing into the leak fuel passage 74 suddenly rises, the valve body 72 is immediately lifted and fully opened, resulting in a maximum opening area that contacts the stopper 78. This safety valve function prevents the fuel pressure inside the injector 2 from increasing and damaging the casing that protects the components of the leak line 12 and the piezo actuator 201.

  As described above, according to the leak line pressure setting valve 7 with a built-in safety valve mechanism of the present embodiment, the fuel pressure of the leak line 12 is maintained at the set pressure with a simple structure, and the leak line 12 is quickly opened in the event of an abnormality. Thus, a pressure-accumulating fuel injection device that is high performance and excellent in safety can be realized.

(Second Embodiment)
FIG. 6 is an example of the leak line pressure setting valve 5 that does not incorporate a safety valve mechanism, and FIG. 7 shows a configuration example of an injector return system using the same as a second embodiment of the present invention. The leak line 12 is provided with a mechanical safety valve 61 as a separate safety valve mechanism 6 on the upstream side of the leak line pressure setting valve 5.

  As shown in FIG. 6, the leak line pressure setting valve 5 is configured by housing a steel spherical valve body 52 in a valve chamber 53 provided in the valve housing 51. In the valve chamber 53, a leak fuel passage 54 connected to the leak line 12 on the injector 2 side is opened at the center of the bottom surface, and a conical taper-shaped seat 55 is formed around the opening so that the valve body 52 is seated. It has become. A leak fuel passage 56 connected to the leak line 12 on the fuel tank T side is opened on the side surface of the valve chamber 53. A flow path from the leak fuel passage 54 through the valve chamber 53 to the leak fuel passage 56 becomes a part of the leak line 12.

  The valve body 52 is urged in the seating direction by the urging force of the spring 57 disposed above it, and closes the leak fuel passage 54. The upper end of the spring 57 is supported by a recess provided on the top surface of the valve chamber 53 and is disposed around a rod-shaped stopper 58 that protrudes from the center of the recess toward the valve body 52 to maintain its posture. And the leak fuel pressure by the side of the injector 2 is hold | maintained to setting pressure by adjusting the spring 57 so that it may become predetermined | prescribed valve opening pressure (for example, 1.1 MPa).

  If comprised in this way, an accurate sealing surface can be made at low cost by pressing the steel spherical valve body 52 against the conical taper surface-like sheet 55. The valve body 52 is opened when the fuel pressure received on the pressure receiving surface exceeds the load of the spring 57, and the leak fuel passages 54 and 56 are communicated to discharge excess fuel to the fuel tank T side. At this time, the position shift of the spring 57 is suppressed by the stopper 58 and the lift amount of the valve body 52 is regulated, so that a stable operation can be obtained.

  The mechanical safety valve 61 is directly connected to the fuel tank T in the branch passage 15 that branches from the leak line 12 on the injector 2 side from the leak line pressure setting valve 5. The structure of the mechanical safety valve 8 can be a check valve structure similar to the leak line pressure setting valve 5 of FIG. 6, a passage that forms part of the branch passage 15, a valve body that opens and closes the passage, It has a spring that urges the body in the valve closing direction, and only allows fuel movement from the injector 2 in the direction of the fuel tank T. Then, when the inflowing leak fuel pressure exceeds a predetermined allowable pressure (for example, 1.4 MPa), the valve is opened and the spring force is adjusted so as to open the branch passage 15, thereby the leak line pressure setting valve. The leaked fuel is quickly discharged without going through 5, thereby improving safety.

  In order to operate the mechanical safety valve 61 stably and appropriately, as described in Patent Document 1 described above, a steel spherical valve body is accommodated in the end face of the valve member and is configured to slide integrally. It is also possible to adopt a configuration in which the member is always immersed in fuel to prevent sticking.

  According to the present embodiment, the leak line pressure setting valve 5 having a simple configuration maintains the leak fuel pressure at a predetermined setting pressure, and the mechanical safety valve 8 prevents damage at the time of abnormal pressure. An accumulator fuel injection device with high safety can be realized.

(Third embodiment)
FIG. 8 shows a configuration example of the injector return system according to the third embodiment of the present invention, in which the leak line pressure setting valve 5 and the electric safety valve 62 as the safety valve mechanism 6 are provided separately. The leak line pressure setting valve 5 has the same configuration as that of the second embodiment, and a description thereof is omitted. The electrical safety valve 62 is provided in the leak line 12 on the injector 2 side from the leak line pressure setting valve 5 and is directly connected to the fuel tank T in the branch passage 15 as with the mechanical safety valve 61. The timing leak fuel can be discharged. Hereinafter, the difference will be mainly described.

  FIG. 9A shows a specific configuration example of the electric safety valve 62. In the drawing, an electric safety valve 62 includes a coil 603 wound around a solenoid core 602 housed in a solenoid housing 601, an armature 604 driven by suction by energizing the coil 603, and a valve provided integrally with the armature 604. A needle 605 is provided. The valve needle 605 is slidably provided in a cylinder provided in the valve body 606 and is pressed downward by an urging spring 608. The urging spring 608 is accommodated in a space in the central portion of the solenoid housing 601, and a lower end is fitted around a convex guide spring 607 provided on the upper surface of the armature 604 to maintain the posture.

  As shown in FIG. 8, in this embodiment, the pressure sensor 16 is provided in the leak line 12, and the ECU 41 controls the driving of the electric safety valve 62 based on the detection result. In FIG. 9A, the valve needle 605 is seated on the valve seat 609 on the top surface of the convex portion provided in the valve body 606 and is opened to the bottom surface of the valve body 606 in a state where power is not supplied. Is closed. The annular space around the valve seat 609 is always in communication with an outlet 611 that opens on the side of the valve body 606. The inlet 610, the annular space around the valve seat 609, and the outlet 611 form part of the branch passage 15 from the leak line 12, and when the electric safety valve 62 is opened, the branch passage 15 is opened and the leak fuel is fueled. It flows out to the tank T.

  A stopper 614 is formed on the upper surface of the armature 604 at a step portion provided around the guide spring 607 so as to regulate the upper end position when the armature 604 is driven to be sucked. The outlet 611 is connected to a leak recovery passage 613 from an armature chamber in which the armature 604 is accommodated, and recovers fuel leaking from the sliding portion of the valve needle 605 to the armature chamber when driven. Since the leak recovery passage 613 communicates with the annular space around the valve seat 609, a filter 612 is interposed at the inlet 610 opening that reaches the valve seat 609.

  FIG. 10 shows a control flowchart by the ECU 41. FIG. 9B shows the control at the time of abnormally high pressure and the behavior of each part. In FIG. 10, the pressure of the pressure sensor 16 is read in step 101, and in step 102, it is determined whether or not the pressure is abnormal, that is, whether or not a predetermined allowable pressure (for example, 1.4 MPa) is exceeded. When the pressure is abnormal, the routine proceeds to step 103, the safety valve drive signal is turned on, the electric safety valve 62 is opened at step 104, and the routine returns to step 101.

  As shown in FIG. 9B, when the ECU 41 switches the drive signal of the electric safety valve 62 from OFF to ON and applies a solenoid drive current to the coil 603, the solenoid core 602 is excited and the bias spring 608 is attached. The armature 604 is sucked and driven by overcoming the power. Along with this, the valve needle 605 integrated with the armature 604 moves upward to open the valve seat 609, and the leaked fuel that has been blocked flows out from the outlet 611 to the fuel tank T. As a result, the pressure in the vicinity of the inlet 610 rapidly decreases. The solenoid drive current is reduced to a current value that can attract and hold the armature 604 at the valve open position after the valve is opened.

  In FIG. 10, Step 101 and the subsequent steps are repeated, and if Step 102 is negatively determined to be no abnormal pressure, the routine proceeds to Step 105 where the safety valve drive signal is turned off and the electric safety valve 62 is closed at Step 106. In the following step 107, it is determined whether or not the ignition switch is on. If not, exit.

  As shown in FIG. 9B, when the valve needle 605 is opened, the pressure in the vicinity of the inlet 610 quickly decreases to a predetermined set pressure. Here, when the drive signal is switched off again and application of the solenoid drive current is stopped, the valve needle 605 integrated with the armature 604 is lowered by the biasing force of the biasing spring 608 and is seated on the valve seat 609 to be closed. To do.

  FIG. 10 shows a control flowchart by the ECU 41. In FIG. 10, the pressure of the pressure sensor 16 is read in step 101, and in step 102, it is determined whether or not the pressure is abnormal, that is, whether or not a predetermined allowable pressure (for example, 1.4 MPa) is exceeded. When the pressure is abnormal, the routine proceeds to step 103, the safety valve drive signal is turned on, the electric safety valve 62 is opened at step 104, and the routine returns to step 101.

  According to the present embodiment, the leak fuel pressure is maintained at a predetermined set pressure with the leak line pressure setting valve 5 having a simple configuration, and at the time of abnormal pressure, the pressure sensor 16 and the electric safety valve 62 are used at an arbitrary timing. Since the leak line 12 can be opened instantaneously and reliably to prevent the structural members from being damaged, a high-performance and highly safe accumulator fuel injection device can be realized.

1 is an overall configuration diagram of a pressure accumulation fuel injection device according to a first embodiment of the present invention. It is a figure which shows the detailed structural example of the injector used in the 1st Embodiment of this invention. (A) is a figure which shows the principal part structure of the injector return system in 1st Embodiment of this invention, (b) is a figure for demonstrating the state at the time of valve opening of the leak line pressure setting valve with a built-in safety valve mechanism. is there. It is a figure which shows the relationship between the valve lift and opening area in the 1st Embodiment of this invention. It is a figure which shows the relationship between the leak pressure and valve opening area in the 1st Embodiment of this invention. It is a figure which shows the structural example of the leak line pressure setting valve which does not incorporate a safety valve mechanism. It is a figure which shows the structural example of the injector return system in 2nd Embodiment of this invention. It is a figure which shows the structural example of the injector return system in 3rd Embodiment of this invention. (A) is a figure which shows the specific structural example of an electric safety valve, (b) is a figure which shows the control at the time of abnormally high pressure, and the behavior of each part. It is a figure which shows the control flowchart by ECU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail 11 High pressure line 12 Leak line 13 Common rail pressure sensor 14 Pressure reducing valve 2 Piezo injector 21 Driving force transmission mechanism 201 Piezo actuator (actuator)
203 Large-diameter piston 204 Small-diameter piston 205 Oil-tight chamber 22 Control valve 23 Control chamber 24 High-pressure passage 25 Low-pressure passage 26 Needle valve 3 Supply pump 4 Control unit 41 ECU
42 EDU
5 Leak line pressure setting valve 6 Safety valve mechanism 61 Mechanical safety valve 62 Electric safety valve 7 Safety valve mechanism built-in type leak line pressure setting valve 71 Valve housing 72 Valve body 73 Valve chamber 77 Spring 78 Stopper T Fuel tank F Filter

Claims (8)

An accumulator fuel injection device that injects high-pressure fuel supplied from an accumulator into a cylinder of an internal combustion engine,
The injector provided for each cylinder has a driving force transmission mechanism that transmits the driving force of the actuator through the oil-tight chamber,
In the leak line that guides the leaked fuel from the injector to the fuel tank, a leak line pressure setting valve that holds the leak fuel pressure at a predetermined set pressure is provided,
An accumulator fuel injection device comprising a safety valve mechanism that operates only when a leak fuel pressure in the leak line rises above a predetermined allowable pressure and opens a passage to the fuel tank. The safety valve mechanism is provided integrally with the leak line pressure setting valve,
The leak line pressure setting valve accommodates a valve body that opens and closes the leak fuel passage in a valve housing that forms a leak fuel passage that forms part of the leak line, and the valve body is connected to the injector from the injector. A function as a check valve that opens when the leak fuel pressure exceeds the set pressure and causes the leak fuel to flow out, and when the leak fuel pressure from the injector exceeds the allowable pressure, the opening area is rapidly expanded The pressure-accumulation fuel injection device according to claim 1, which also has a function as a safety valve for opening the passage.   In the normal control region within a predetermined range from the set pressure, the valve body forms a first throttle that increases the opening area as the leak fuel pressure increases, and a pulsation region from the upper limit pressure of the normal control region to the allowable pressure Then, a second throttle that maintains the upper limit opening area of the first throttle is formed, and a third throttle that quickly reaches the maximum aperture area is formed by an increase in the leak fuel pressure in the abnormally open region that is greater than or equal to the allowable pressure. The pressure accumulation type fuel injection device according to claim 2 which has a structure.   The valve body includes a conical sheet portion whose diameter is reduced toward the front end side, and a cylindrical tip portion having the same diameter as that of the minimum tip diameter portion of the seat portion and smaller than the seat diameter. Then, after forming the first aperture between the side surface of the sheet portion and the sheet, and then forming the second aperture between the side surface of the front end portion and the sheet, the end surface of the front end portion The pressure-accumulation fuel injection device according to claim 3, wherein the third throttle is formed between the seat and the seat.   5. A spring for urging the valve body in a seating direction is disposed in the valve housing, and a stopper for holding the valve body at a position having a maximum opening area is formed. 2. An accumulator fuel injection device as described in 1.   The safety valve mechanism is disposed in a branch passage that communicates the leak line on the injector side with the fuel tank from the leak line pressure setting valve, and opens when the leak fuel pressure exceeds the allowable pressure. The pressure accumulation type fuel injection device according to claim 1, which is a mechanical safety valve set to open the branch passage.   The safety valve mechanism is disposed in a branch passage that communicates the leak line on the injector side with the fuel tank from the leak line pressure setting valve, and the leak fuel pressure detected by the pressure detection means exceeds the allowable pressure. 2. The accumulator fuel injection device according to claim 1, which is an electric safety valve that is driven to open when the valve is open and opens the branch passage.   The pressure accumulation type fuel injection device according to any one of claims 1 to 7, wherein the driving force transmission mechanism is a mechanism for transmitting a displacement of a piezoelectric actuator via an oil pressure in an oil tight chamber formed between a pair of pistons.

Images